Search

The influence of deep rolling (DR) parameters (speed, number of passes and pressure) on the equivalent total strain, α '-martensite formation, ultra-microhardness, microstructure, and corrosion resistance of an AISI 304 austenitic stainless steel was investigated. The results showed that increasing DR speed led to less heterogeneous strain distributions and relatively high ultra-microhardness, despite an overall reduction in strain and α '-martensite content. This increase in hardness was related to the rise of geometrically necessary dislocations (GNDs) density, found to be one of the primary microstructural features influencing mechanical behavior under high DR speed. The increase in the number of passes elevated the intensity and depth of strain, leading to a 70% increase in the content of α '-martensite, ultra-microhardness, and producing severe grain refinement. The GNDs density decreased in the refined grain layer and increased sharply below it. Increased pressure induced similar results relative to the number of passes, with less impact. Improvement in the material properties is achieved through the interaction of parameters that result in an increase in the severity of the DR process, i.e, a reduction in speed and an increase in the number of passes and pressure. For severe DR conditions, the materials corrosion resistance in a 3.5% NaCl aqueous solution was significantly improved, with an increase of up to 2488% in the polarization resistance, as assesssed by electrochemical impedance spectroscopy. In potentiodynamic polarization tests, the corrosion potential increased from an average value of −0.274 to −0.14 V, and the corrosion current density decreased by approximately 300%. [Display omitted] • High speed reduces martensite but increases GNDs, improving mechanical strength. • Number of passes is the main burnishing parameter responsible for grain refinement. • Severe burnishing increases strain and martensite AISI 304 steel subsurface. • Severe burnishing significantly improves corrosion resistance of AISI 304 steel. [ABSTRACT FROM AUTHOR]

As a burgeoning surface finishing process, laser polishing (LP) introduces some undesired surface structures, limiting access to better laser-polished surfaces. Considering this, the paper proposes a novel hybrid processing method, ultrasonic vibration-assisted laser polishing (UVLP). Horizontal ultrasonic vibration, perpendicular to the laser scanning direction, is imposed on the workpiece, which promotes homogenized melt distribution in the melting pool, contributing to the polished surface flatness. Bulge, a typical surface structure formed in LP, serves as the verification vehicle for the effect of ultrasonic vibration here. In this investigation, comparative experiments were performed on 304 stainless steels to demonstrate the regulation phenomenon of ultrasonic vibration on the bulge formation. Subsequently, the corresponding numerical model was developed to explore the acting mechanisms of ultrasound from the thermal and hydrodynamic fields. The model also optimized the coupling method of volume expansion to better capture the change in melting pool volume during the polishing process, especially during the cooling phase. The results indicated that the forced melt oscillations are the dominant mechanism to uniformize the metallic materials distribution, regulating the bulge formed along the polished track. The degraded melt flow pattern, a simple harmonic oscillation, reached similar results. Furthermore, the developed model verified its effectiveness through surface flatness, melting pool dimensions, and microhardness. • A new hybrid processing method, ultrasonic vibration-assisted laser polishing (UVLP), is proposed. • The regulation phenomenon of ultrasonic vibration on the bulge formation is visualized. • The acting mechanisms of ultrasonic vibrations in UVLP are analyzed theoretically and experimentally. • A UVLP model is developed and its effectiveness is verified. • The coupling method for volume expansion is optimized. [ABSTRACT FROM AUTHOR]

Surface decorated wood-based panels with melamine formaldehyde resin (MF) impregnated paper is highly favored by consumers due to its outstanding appearance and durable performance. However, the laminated composites would encounter hygroscopic expansion and damage that affect its service and aesthetics in long-term humid environments. This study aims to construct highly durable superhydrophobic surface to address this issue. Firstly, a controlled micro rough structure on stainless steel plates which were built with sandblasting was successfully duplicated onto the surface of MF impregnated paper laminated medium density fiberboard (MDF) using the embossing method. Following that, a spray treatment with hydrophobic nanoparticles was employed to the laminated composite surface, ultimately resulting in a superhydrophobic coating with a contact angle up to 163°. To confirm the durability of the fabricated superhydrophobic layer, linear abrasion test, water droplet impact test, sand impact test, and tape peeling test were carried out. The results demonstrated that even after severe processed conditions, the contact angle of the decorated surface remained above 150°. And the decorated laminate successfully passed both self-cleaning and dirt resistance challenge, clearly indicating the outstanding durability of superhydrophobic structure. Furthermore, water absorption thickness expansion measurement was done to verify the dimensional stability of the laminate in humid conditions. This research presented a straightforward and cost-effective approach to fabricate highly durable superhydrophobic MF impregnated paper decorated laminates, offering a dependable strategy for research and applications in related domains. [ABSTRACT FROM AUTHOR]

Plasma assisted thermochemical diffusion treatments have been extended to stainless steel and the usual process parameters are still in discussion regarding wear and corrosion performance as well as energy efficiency. In this work, a short time route for the thermochemical treatment for AISI 420 martensitic stainless was chosen, setting the duration to 2 h, changing other parameters such as temperature and N 2 partial pressure. Temperatures of 420 and 440 °C were used, and two different atmospheres were applied, N 2 -H 2 for nitriding, and N 2 -H 2 -CH 4 for nitrocarburizing. The microhardness was measured, and microstructure was analyzed by XRD. Pin on disk tests were carried out according to G99 standard using alumina as counterpart, and abrasion wear tests were done following ASTM G65 standard. Corrosion behavior was evaluated using the salt spray fog test and electrochemical tests in NaCl solution. Modified layers between 5 and 15 μm thickness were obtained and surface hardness was always above 1000 HV. In XRD measurements martensite expanded by nitrogen/carbon and iron nitrides or carbonitrides were detected. The sample nitrocarburized at 440 °C showed better wear resistance under sliding conditions, however, the samples nitrided at 440 °C had the lowest mass loss in abrasive wear tests. Regarding the corrosion resistance, the sample nitrocarburized at 440 °C exhibited the best results in the salt spray fog test and in electrochemical tests. This behavior was related to the presence of the carbonitrides and the layer thickness. • Plasma nitriding and nitrocarburizing for 2 h produced modified layers 13 μm thick. • All treated samples had good wear resistance under adhesive and abrasive conditions. • The N440 sample with higher hardness in depth had the best behavior in abrasive wear. • The NC440 sample had the best corrosion behavior in electrochemical and Salt Spray tests. [ABSTRACT FROM AUTHOR]

Corrosive wear is a key factor affecting the safe operation of offshore engineering equipment. In this study, Co 19.6 Cr 19.6 Fe 19.6 Ni 19.6 (B 13.72 Si 5.88) 19.6 Y 2 and Fe 43.6 Ni 17.4 Cr 9 Co 6 B 17.5 Si 1.5 Nb 5 coatings were prepared on the surface of 304 stainless steel using laser cladding technology. Dry wear and corrosive wear behavior of both coatings and 304 stainless steel were comparatively studied under different loads. The results show that both coatings are mainly composed of FCC solid solution, boride, and Laves phases. The average microhardness of Co 19.6 Cr 19.6 Fe 19.6 Ni 19.6 (B 13.72 Si 5.88) 19.6 Y 2 and Fe 43.6 Ni 17.4 Cr 9 Co 6 B 17.5 Si 1.5 Nb 5 coatings are 578.6 HV 0.2 and 632.5 HV 0.2 , respectively. The dry wear resistance of Fe 43.6 Ni 17.4 Cr 9 Co 6 B 17.5 Si 1.5 Nb 5 coating is approximately 3 times that of 304 stainless steel under all friction load conditions. It can be found that the Fe 43.6 Ni 17.4 Cr 9 Co 6 B 17.5 Si 1.5 Nb 5 coating with high hardness is less sensitive to friction load changes during dry wear process. In 3.5 wt% NaCl solution, the corrosive wear resistance of CoCrFeNiBSiY coating under friction loads of 30 N and 50 N is 2.68 times and 2.83 times that of 304 stainless steel, respectively. The excellent corrosive wear resistance performance of the CoCrFeNiBSiY coating is mainly attributed to its superior corrosion resistance and repassivation ability. During the corrosive wear process, a dense passivation film is formed on the surface of both coatings, which significantly reduces their friction coefficient and volume loss rate. • Laser cladding coatings were successfully prepared on 304 stainless steel substrate. • Laser cladding coatings with high hardness are less sensitive to frictional loads. • The increase in friction load accelerates the formation of oxide layer on the coating surface. • The CoCrFeNiBSiY coating exhibits superior corrosive wear resistance. • A dense passivation film is formed on the surface of both coatings in corrosive wear environments. [ABSTRACT FROM AUTHOR]

In this paper, CrN coatings were deposited on AISI 1045 steel, AISI H13 steel, and AISI 2205 duplex stainless steel substrates using arc ion plating. The effects of substrate characteristics on the hardcoated sample properties, especially tribocorrosion performance were investigated systematically. The results show that there were little differences in the surface morphology, crystalline structure as well as nanohardness among the three hardcoated samples. Compared with the bare substrates, the electrochemical properties of 1045-CrN and H13-CrN in 3.5 wt% NaCl solution were significantly improved with the I corr values of 2.10 × 10−6 A·cm−2 and 9.63 × 10−7 A·cm−2, respectively, but still worse than that of 2205-CrN specimen (1.84 × 10−8 A·cm−2). The E corr of 2205-CrN was over 200 mV higher than those of 1045-CrN and H13-CrN. In addition, 2205-CrN displayed the highest R ct value of 1.953 × 106 Ω·cm2, which was enhanced by two orders of magnitude compared to the other two specimens owing to the excellent corrosion resistance of AISI 2205 steel substrate. The tribocorrosion rates of the three hardcoated specimens in 3.5 wt% NaCl solution were significantly reduced compared with their underlying substrates (by 70 %, 36 %, and 85 % for 1045-CrN, H13-CrN, and 2205-CrN, respectively). The 2205-CrN specimen displayed the best tribocorrosion performance with the rate of 2.51 × 10−6 mm3·N−1·m−1. The tribocorrosion mechanisms of CrN coatings deposited on carbon and stainless steels were also discussed. Mutual promotion effect of corrosion and wear was confirmed for CrN-coated carbon steels, while a negative synergistic effect was observed from the CrN-coated stainless steel substrate. • The electrochemical and tribocorrosion properties of CrN coatings deposited on different steels were closely related to their underlying substrates. Compared to the steel hardness, the substrate corrosion resistance played a more important role in the specimen performance. • The OCP variations of CrN-coated carbon steels were opposite to those of CrN-coated stainless steel during tribocorrosion process, but the OCP trends of all CrN-coated specimens were similar with those of their underlying substrates. • The tribocorrosion mechanisms of CrN coatings deposited on carbon and stainless steel substrates were thoroughly discussed. Mutual promotion effect of corrosion and wear was confirmed for CrN-coated carbon steels, while a negative synergistic effect was observed from the CrN-coated stainless steel substrate. [ABSTRACT FROM AUTHOR]

Deep drawing of stainless steel and aluminum is a widely adopted method for manufacturing various industrial goods. However, the wear damage produced to die tools is a recurring problem in these processes. While lubricants are often employed to lubricate and reduce die wear, dry deep drawing is the current best alternative for meeting green manufacturing demands. Hence, enhanced solid lubricants or surface treatments for dies are highly required. This study aims to evaluate and compare the tribological behavior of a heat-treated AISI D2 steel and a boriding AISI D2 tool steel against stainless steel (AISI 304) and aluminum alloy (AA 6061 T6) in the absence of lubricant. The boride coating was formed on the AISI D2 steel by the closed-pack boriding technique, resulting in a tooth-saw morphology with an overall thickness of 33.6 μm. X-ray diffraction analysis confirmed the presence of FeB, Fe2B, and Cr2B3 phases on the surface of the borided AISI D2 tool steel. Notably, the boriding treatment led to a significant increase in the surface hardness of the tool steel, reaching a value of 20.7 GPa. The coefficient of friction (CoF) behavior and wear were evaluated by pin-on-disk tests, simulating conditions similar to those found in cold deep drawing operations. The wear surfaces were analyzed by optical profilometry and scanning electron microscopy (SEM). The results suggest boriding as a suitable treatment to reduce wear damage on the surface of deep drawing dies used for stainless steel and aluminum forming processes in the absence of lubricant. Two-body abrasion and adhesion were identified as the main wear mechanisms in AISI D2 steel against stainless steel and aluminum, with a significant amount of oxidation observed when aluminum was tested. Additionally, a reduction of approximately 20 % in the CoF was observed when employing borided tool steel against stainless steel. However, there was an observed increase of around 75 % in the CoF when the borided tool steel was tested against aluminum. • Boriding reduced wear in dry sliding of tool steel against Inox steel and aluminum. • CoF decreased for Inox steel vs. tool steel with borided samples. • CoF increased for aluminum vs. tool steel with borided samples. • Stainless steel mass loss decreased significantly with borided tool steel. • Abrasion and adhesion were identified as the primary wear mechanisms in all tests. [ABSTRACT FROM AUTHOR]

Nitrogen-doped diamond-like carbon (N-DLC) films with different nitrogen content were prepared on the surface of 304 stainless steel (SS) using plasma-enhanced chemical vapour deposition technology. Localized failure mechanisms of the N-DLC films under long-term exposure to sodium chloride solutions have been investigated. The results demonstrated that nitrogen doping significantly affected the failure behavior of the N-DLC films. When undoped, the number of pore defects in the film is high, providing a channel for the corrosive medium to attack the substrate metal. Meanwhile, due to the high internal stress within the undoped film, extensive exfoliation of the film occurred under the effect of the growth of oxides at the film-substrate interface. The DLC film on 304 SS is subject to stress corrosion cracking failure during long-term service in sodium chloride solution. However, when nitrogen doping is 10 sccm, the pH of the micro-zone solution was highly variable due to the dissolution of nitrogen in the film and the processes of formation and hydrolysis of NH 4 +. A large number of residual metal cations dissolved from the substrate combine with oxygen at the corrosion pits mouth to form oxides. This can aggravate the occlusion effect of the pits and severe pitting corrosion of 304 SS occurs under autocatalytic effects. The N-DLC film with 5 sccm nitrogen addition showed the excellent durability properties. The evolution mechanism of oxidation and dissolution behaviors in the presence of variations in local hydrochemistry is also discussed. [ABSTRACT FROM AUTHOR]

Due to the complex incineration environment of waste incineration power generation boilers generates large amounts of acidic gases (such as Cl 2 and HCl) and alkali metal chlorides (such as NaCl and KCl), leading to boiler corrosion failure. Herein, a new type of NiCrAlTi alloy coatings was deposited on 304 stainless steel surfaces by laser cladding technology. High-temperature corrosion experiments were then carried out at 650 °C for 64 h and the results were compared with those of traditional Inconel625 alloy coating. The high-temperature chloride corrosion mechanism and the corrosion resistance of alloy coatings were examined. The results revealed the decomposition of chlorides, such as HCl, NaCl, and KCl into Cl 2 at high temperatures as the source of corrosion of high-temperature chlorides. The released C1 2 reacted with the metals present in the coating to form nonprotective metal chlorides. The low melting point and high vapor pressure of metal chlorides allowed their transition into a gaseous state to diffuse outward and oxidize into Cl 2. In turn, the released Cl 2 reacted with the metal to induce corrosion. During the corrosion process of NiCrAlTi alloy coating, a Cr depletion zone was induced, and a continuous Al 2 O 3 /TiO 2 /Cr 2 O 3 three-layer protective film was formed on the coating surface, conducive to better alleviating the corrosion caused by the reaction between Cl 2 passing through the film and the metal substrate. Under the conditions of this experiment, the corrosion resistance of NiCrAlTi alloy coating is 1.8 times that of the common material 304 stainless steel, and about 1.2 times that of Incon625 alloy coating. With the extension of the experiment, its corrosion resistance will be better. Overall, rich experimental data and theoretical guidance were provided for further research and development on high-temperature chloride corrosion-resistant alloys or coating materials for high-efficiency cost-effectiveness boilers. • A new type of NiCrAlTi alloy coating has been prepared, which has better resistance to high-temperature chloride corrosion compared to the traditional chromium nickel iron alloy 625 coating. Moreover, over time, due to its three-layer oxide film structure, its stability becomes better. • Supplementary explanations have been provided on the original high-temperature chloride corrosion mechanism. In the final stage of corrosion, as the temperature returns to room temperature, metal chloride oxides are generated on the surface of the coating. • At present, research on high-temperature chloride corrosion mainly focuses on the high-temperature corrosion of HCl gas or the hot corrosion of NaCl and KCl. This article combines HCl gas with NaCl and KCl chloride for corrosion research, and the results are closer to reality. [ABSTRACT FROM AUTHOR]

The effects of heat treatment on the microstructure, residual stresses, nano-indentation behavior, the resistance to the corrosion and cavitation erosion (CE) of 17-4PH stainless steel (17-4PH SS) by laser surface melting (LSM) were thoroughly investigated. Experimental results showed that the samples were mainly composed of martensite phase, and the NbC precipitations formed after heat treatment. The distribution of NbC precipitations was more uniform in the sample (S3) after solution treatment 3 h at 1040 °C + aging treatment 3 h at 480 °C. The grain size was increased for the samples after heat treatment. This heat treatment processing significantly reduced the residual stresses generated from the LSM process, and the nano-indentation behavior of the LSM samples after heat treatment was improved compared to that of the LSM sample without heat treatment. The S3 sample displayed the highest corrosion resistance as indicated by the low corrosion current density (i corr), high pitting potential (E pit) and high polarization resistance (R p). The CE resistance of samples after heat treatment in 3.5 wt% NaCl solution was higher than that of the sample without heat treatment. Among them, the S3 sample exhibited the highest CE resistance, and its CE mass loss was only 59.5 % of the sample without heat treatment. The excellent CE resistance resulted from the appropriate combination of mechanical properties, corrosion resistance and self-recovery ability of the passivation film. • 17-4PH stainless steel by laser surface melting was subjected to heat treatment. • The microstructure and residual stress of samples after heat treatment were studied. • The nano-indentation behaviors of samples after heat treatment were improved. • The resistance to corrosion and cavitation erosion was improved. [ABSTRACT FROM AUTHOR]

In this study, Co-Cr-Ni-W alloy parts were fabricated on the surface of 304 stainless steel (SS) substrate by laser directed energy deposition (LDED). Microstructure, microhardness and tribological behavior of as-deposited samples and 750 °C–950 °C aging-treated samples were tested. Carbides precipitated from Co-Cr-Ni-W alloy, and martensite transformation from γ-Co (FCC) to ε-Co (HCP) occurred in high temperature. The changes of microstructure caused by aging treatment could increase the microhardness and change wear mechanism. Tensile property of Co-Cr-Ni-W alloy at 750 °C–950 °C was also investigated. Co-Cr-Ni-W alloy formed a hard-sliding structure under high temperature, leading to high tensile strength. The main fracture mode of Co-Cr-Ni-W alloy was brittle cleavage fracture. • Discussed the effects of various elements in laser clad Co-Cr-Ni-W alloy • Revealed the wear mechanism of laser clad Co-Cr-Ni-W alloy • Evaluated the tensile property of Co-Cr-Ni-W alloy at high temperatures • Analyzed the fracture mechanism of Co-Cr-Ni-W alloy during stretching [ABSTRACT FROM AUTHOR]

Super duplex stainless steels (SDSS), widely used in industries such as offshore oil and gas, offer a unique combination of high strength and corrosion resistance. However, surface hardening treatments are crucial to enhance their performance and extend service life. This work investigates the effect of plasma nitriding on the tribological behaviour of SDSS SAF 2507. Samples are treated without prior polishing (as received, AR) at ultra-low temperatures (250 and 300 °C) aiming to avoid detrimental CrN precipitation. Comprehensive microstructural characterization, corrosion studies, and tribological tests (scratch and ball-on-disc) are conducted on samples that do not present CrN (PN). Results indicate that the hardness of PN samples nearly doubles that of AR samples due to the presence of expanded austenite. Corrosion tests show improvements in passivity for PN samples. In scratch tests, while the AR material undergoes progressive plastic deformation, in PN material the nitrided layer breaks down only after reaching a critical load. In ball-on-disc test, wear rates are remarkably lower for PN condition compared to AR condition. Wear mechanism is tribo-oxidative and abrasive for the AR condition. Wear of PN samples is characterized by asperity break-off and ratcheting. The nitrided layer in PN samples exhibits an enhanced load-bearing capacity that improves wear resistance in both tests. • SDSS without previous polishing (AR) was plasma nitrided at 250 °C and 300 °C. • Plasma nitrided AR at 250 °C (PN) does not present Cr nitrides. • PN has an expanded austenite layer of 2 μm thickness. • PN has enhanced passivity and hardness than that of untreated material. • The good load-bearing capacity of PN increased its wear resistance. [ABSTRACT FROM AUTHOR]

To enhance the surface properties, particularly hardness and wear resistance, of AISI 321 steel, an aluminizing coating was introduced through pack cementation treatment. Microstructure characterization and wear resistance tests were conducted to elucidate the intricate relationship between the microstructure and wear behaviors. A thorough analysis on the structure and compositions revealed the incorporation of FeAl(Cr) phases, aluminum oxides, titanium compounds and B2-NiAl phases in the coating, which resulted in a remarkable 192 % increase on the surface hardness, elevating it from 226 HV to an impressive 662 HV. In comparison to the uncoated 321 steel, the aluminized counterpart exhibited a pronounced reduction in coefficients of friction (COFs), wear volume losses, and wear rates. The wear mechanisms of both the uncoated 321 steel and aluminized steel were intricately analyzed. The uncoated 321 steel endured severe adhesive and oxidation wear, characterized by pronounced plastic deformation, the presence of wear debris and flaking oxides. In contrast, the aluminized steel predominantly underwent abrasive wear, showcasing a relatively smooth worn surface and dense continuous oxides. These findings not only reveal the significant enhancement of tribological properties by aluminized coatings, but also provide valuable insights into their fundamental behavior during wear. • A ~135 μm thick Fe Al coating was introduced on the surface of AISI 321 steel. • The tribological properties were significantly enhanced after aluminizing treatment. • The coated and uncoated 321 steels exhibited different wear mechanisms. [ABSTRACT FROM AUTHOR]

Due to the outstanding mechanical and physical properties of high entropy alloy (HEA) coatings, the global academic and industrial communities have made significant research efforts in recent years, aiming to expand their industrial applications. In this study, TiZrNbSiMo and (TiZrNbSiMo) 1-x N x HEA nitride coatings with different nitrogen contents were fabricated using a high power impulse magnetron sputtering (HiPIMS) system. By varying the nitrogen flow rates, the nitrogen contents of coatings increased from 0 to 48.8 at. %. The deposition rate decreased with increasing nitrogen content due to the target poisoning effect. Very fine and dense microstructure can be seen for each coating. The amorphous structure was obtained as the nitrogen content was lower than 19.1 at.%, whereas a nanocrystalline FCC structure was formed when the nitrogen content reached 34.9 at. %. Furthermore, the corrosion resistance of TiZrNbSiMo and four TiZrNbSiMoN HEA coatings in 0.5 M H 2 SO 4 aqueous solution were superior to uncoated 304 stainless steel. We can conclude that the nanocrystalline TiZrNbSiMoN HEA coatings with a nitrogen content of 34.9 at. % exhibited a high hardness of 15.6 GPa, an electrical resistivity of 766.5 μΩ·cm, and an excellent corrosion polarization resistance of 9.71 × 105 Ω·cm2, 610.7 times higher than 304SS. This study provides valuable insights for future promising applications of (TiZrNbSiMo) 1-x N x HEA nitride coatings in severely corrosive environments, such as the protective coatings on stainless steel bipolar plates in proton exchange membrane fuel cells. • We grow TiZrNbSiMo and TiZrNbSiMoN high entropy alloy coatings. • The FCC structure is obtained after the addition of 34.9 at.% N. • The deposition rate of the coating decreases with N content. • The 34.9 at.% N contained TiZrNbSiMoN coating has the highest hardness and the best corrosion resistance. [ABSTRACT FROM AUTHOR]

In this work, surface mechanical rolling treatment (SMRT) was applied as a post-process nanostructuring technique to improve the tribo-corrosion degradation resistance of coarse grain (CG) 316L stainless steel (SS). The experimental findings reveal that when tribo-corrosion wear took place, the CG specimen experienced severe surface de-passivation, which increased wear-corrosion synergy and the rate of material loss. On the other hand, the SMRT specimen experienced enhanced re-passivation kinetics, which reduced wear-corrosion synergy and the rate of material loss. The wear mechanism for both the CG and SMRT specimens was abrasion-dominant, with the CG specimen having the presence of micro-pits within the wear track. In addition to these findings, the reduced surface roughness, improved hardness, formed compressive stresses, microstructural refinement, and martensite phase transformation induced by the SMRT process contributed to the enhanced tribo-corrosion resistance of the SMRT specimen. In total, SMRT was found to be a feasible technique to improve the tribo-corrosion resistance of CG 316L SS. • The tribocorrosion (TC) behavior of surface nanostructured (SN) steel was studied. • SNing reduced surface roughness/grain size and increased surface hardness. • SNing improved TC repassivation kinetics and decreased wear-corrosion synergy. • Abrasive wear was the predominant wear mechanism for the SN'd steel. • Collectively, SNing is a viable technique to improve the TC resistance of steel. [ABSTRACT FROM AUTHOR]

Using a high-power impulse and direct current (DC) magnetron sputtering approach, C-doped CrN films with various C-target pulse frequencies are created on the surface of SS 304. The microstructure, corrosion resistance and conductivity of the films are examined. With the decreases of C-target pulse frequency, the roughness of the CrCN films decreases and the density increases. The results of XPS and TEM analyses demonstrate that C atoms are either present in CrN lattice as interstitial atoms or precipitate at grain boundaries to form amorphous carbon, which facilitates the increase of film density and conductivity. In the potentiodynamic tests, the CrCN-1000 Hz film exhibits the lowest corrosion current density 0.54 μA/cm2 at 0.6 V vs. Ag/AgCl potential. The values of i corr and E corr are 0.11 μA/cm2 and 0.427 V, respectively. Furthermore, the CrCN-1000 Hz film has the lowest interface contact resistance (ICR) under a compaction force of 140 N/cm2 after potentiostatic polarization test, indicating that C doping is beneficial to improve the corrosion resistance and conductivity of CrN film. • C-doped CrN films deposited on SS 304 by High Power Impulse Magnetron Sputtering. • C exists as interstitial atom in CrN lattice or amorphous C network at grain boundaries. • Formation of a-C or a-CN x at grain boundaries improve corrosion resistance of film. • Corrosion resistance and conductivity of C-doped CrN films superior to the DoE's criteria. [ABSTRACT FROM AUTHOR]

In this investigation, electropolishing and plasma ion nitriding were applied to super austenitic stainless steel for the purpose of improving corrosion resistance and hardness. Electrochemical experiments were performed in natural seawater, which is used as scrubber wash water. Further, various experiments and analyses—such as FE-SEM, EDS, XRD, 3D laser microscopy, and potential measurement—were performed to evaluate both surface and electrochemical characteristics with the surface treatments. The hardness of electropolished and plasma ion nitrided stainless steel increased by 284.06 Hv and 1548.3 Hv, respectively, compared to mechanical polishing. After electropolishing, the surface roughness (Sa) decreased by approximately 78.2 % compared to mechanical polishing. And after plasma ion nitriding, CrN(precipitate) Fe 4 N(compound) and γ N (expanded austenite) were observed on the surface. The thickness of the layer formed on the surface was expressed as 10 to 12 μm In addition, the surfaces observed after the cyclic potentiodynamic polarization experiment revealed that local corrosion occurred in the mechanical polishing and electropolished specimens, whereas the plasma ion nitrided specimens presented a tendency toward general corrosion. [ABSTRACT FROM AUTHOR]

Surface nanocrystallization is a highly effective approach for enhancing the surface wear resistance of stainless steel. However, the attainment of fast nanocrystallization on stainless steel surfaces remains a significant obstacle. Thus, a novel form for high-voltage electron beam radiation with a rapid response time of 50 ms is proposed to break through this bottleneck. The results revealed the presence of significant quantities of nanocrystals and an amorphous structure in the modified layer of stainless-steel surfaces. A large number of dislocation lines resulted in an interplane distance increase in the (110) planes of Fe-Cr. In addition, the dislocation walls can inhibit the growth of the crystal, contributing to a remarkable enhancement in their surface wear resistance. Significantly, the wear volume of the modified layer decreased from 0.0124 mm3 to 0.0013 mm3, a remarkable reduction of 90 % compared to the initial state due to surface nanocrystallization, dispersion strengthening, and dislocation walls. This study provides novel concepts for the production of surface nanocrystals in ultra-wear-resistant stainless steel. [Display omitted] • A novel form for high-voltage electron beam radiation with a rapid response time of 50 ms • Stainless steel with ultra-wear-resistant was fabricated by EB irradiation. • The process of nanograins generation and the underlying mechanism of strengthening have been elucidated. • Rapid fabrication via EB irradiation advances the wear resistance to 9.5 times higher than that of matrix [ABSTRACT FROM AUTHOR]

The applications of mild steel in harsh service environments are limited due to its poorer mechanical properties and less favorable corrosion resistance. In this work, a martensitic stainless steel cladding layer is manufactured on the surface of the mild steel via heterogeneous double-wire arc directed energy deposition (DED). Two gas metal arc (GMA) torches are used, with heterogeneous metal wires of ER316L and ER70-G as raw materials. The wires, with wire feed speeds of 5.6 m/min and 2.4 m/min, respectively, melt together to form a common molten pool, which solidifies to create a cladding layer. The formation characteristics, microstructure, mechanical properties, and corrosion resistance of the cladding layer are investigated. The results reveal a well-formed cladding layer without macroscopic defects. The microstructure of the cladding layer is composed of martensite and austenite. Compared with the mild steel substrate, the cladding layer exhibits a 170 % increase in microhardness, a 160 % increase in strength, and a 1070 % increase in corrosion resistance. The results of this work contribute to the high-efficiency and low-cost preparation of a high-strength, high-hardness, and corrosion-resistant Fe-based cladding layer (F-BCL) on mild steel. • Fabricating a martensitic stainless steel cladding layer on mild steel • Two heterogeneous wires of ER316 and ER70-G are used. • Martensite and austenite constitute the microstructure. • Mechanical properties and corrosion resistance are significantly improved. [ABSTRACT FROM AUTHOR]

This study explores the high-temperature oxidation behavior of AISI 321 austenitic stainless steel (ASS) at 600 °C in an Ar-21vol.%O 2 atmosphere, considering nanometer-sized surface grain size and pre-oxidation conditions. After initial solution annealing at 1050 °C, AISI 321 ASS samples were water-quenched for homogenized microstructure (SAed samples). Moreover, the surface nanocrystallization of AISI 321 ASS was performed through high-energy shot peening (SNCed samples), reducing the surface grain size to ~75 ± 5 nm. Pre-oxidation occurred at 400 °C for 150 h in Ar-21%O 2 for both SAed and SNCed samples. High-temperature oxidation kinetics was analyzed at 600 °C for 150 h using thermal gravimetric analysis (TGA) on pre-oxidized and non-preoxidized SAed and SNCed samples. FESEM/GDOES and GI-XRD revealed that SNCed samples exhibited improved oxidation resistance, showing no Cr depletion in the subsurface oxide layer up to 100 h, and only minor signs after 150 h. Pre-oxidized SNCed samples demonstrated superior oxidation performance, showing no Cr depletion and subsurface Kirkendall pore formation even after 150 h. These findings are coupled with diffusion relationships, and propose potential mechanisms for enhancing the oxidation behavior of pre-oxidized SNCed AISI 321 stainless steel. • At 600 °C, AISI 321 manifests an inner layer rich in Cr and an outer layer rich in Fe. • SNCed surfaces show improved oxidation behavior, delaying Cr-depletion to ~150 h. • Pre-oxidation treatment (P) offers a barrier, especially in initial oxidation stages. • P-SNCed sample resists Cr depletion and pore formation even after 150 h. [ABSTRACT FROM AUTHOR]

The high-temperature corrosion performance of NiMoCr and CoNiCrAl coatings produced by high velocity oxy-fuel (HVOF) on laser powder bed fusion (L-PBF) 316L stainless steel substate has been evaluated in presence of three different molten salts used as thermal energy storage (TES) materials for concentrated solar power (CSP) plants. The coatings have an excellent oxidation resistance at 700 °C, showing a percentage of affected thickness lower than 2 %, due to the formation of a protective layer of Cr 2 O 3 and Al 2 O 3 in both NiMoCr and CoNiCrAl coatings, respectively. The carbonates-based molten salt accelerates the corrosion of the NiMoCr coating, affecting around 43 % of the coating thickness, due to the formation of chromates and the high depletion of Mo in the coating. In contrast, the effective protection shown by the CoNiCrAl coating is explained because the grown LiAlO 2 after the lithiation process has a high capacity to act as a strong diffusion barrier for metal ions and inhibited the formation of chromates. In the presence of two different ZnCl 2 and MgCl 2 -rich molten salts, the CoNiCrAl coating behaved worse than NiMoCr coating due to the breakage of the (Al,Cr)-rich oxide layer as a consequence of an active oxidation mechanism and due to the formation of voids along the entire thickness, which were identified in 100 % of the coating thickness. The superior corrosion resistance of the NiMoCr coating in presence of the chloride rich molten salts was attributed to the presence of Mo, which fixed the Cr and inhibited the diffusion of oxygen. [Display omitted] • HVOF coatings have been effectively deposited on L-PBF 316L ss substrates. • The high-temperature corrosion performance of HVOF coatings has been evaluated in presence of three molten salts. • The HVOF coatings have an excellent oxidation resistance at 700 °C. • The CoNiCrAl coating has superior resistance in the presence of carbonates-based molten salt than NiMoCr coating. • The CoNiCrAl coating behaved worse than NiMoCr coating in the presence of the two chloride-rich molten salts analyzed. [ABSTRACT FROM AUTHOR]

Among various fabrication technologies for high entropy alloy coatings, high power impulse magnetron sputtering (HiPIMS) technologies have been utilized to synthesize dense microstructure and high hardness coatings with enhanced mechanical and chemical properties. Mid-frequency (MF) pulses have been introduced in the off-time of HiPIMS pulses of the superimposed HiPIMS-MF system to improve the deposition rate. In this study, AlCrNbSiTiBN coatings were deposited using a superimposed HiPIMS-MF system connected to an Al 4 Cr 2 NbSiTi 2 high entropy alloy target and a direct current (DC) power source for TiB 2 target in a reactive Ar and N 2 gas mixture. The DC power of the TiB 2 target was varied to increase the titanium and boron contents. With increasing Ti and B contents, the microstructure transforms from loose granular and crystalline structure to denser and refined nanocrystalline phases. A residual stress-free coating with a B content of 4.2 at.%. and a hardness of 16.2 GPa was achieved without intentional heating and substrate bias. The poor corrosion resistance of the coatings with lower B contents can be enhanced with a further increase of B content up to 6.4 at.% and reaching a maximum of 10.3 times improvement than that of AISI 304 stainless steel. • Six AlCrNbSiTiBN coatings were deposited using a superimposed HiPIMS-MF system. • Increasing Ti ratio and N reduce the lattice parameter. • Coating structure changes from granular to dense nanocrystalline with increasing B content. • Coating with (Ti+B)/(Al+Cr+Nb+Si) ratio of 0.47 exhibits a hardness of 16.2 GPa. • Coating with (Ti+B)/(Al+Cr+Nb+Si) ratio of 0.58 shows the best corrosion resistance, 10.3 times of AISI 304 steel. [ABSTRACT FROM AUTHOR]

To improve the friction and wear performance of coatings in aerospace engineering under wet and dry alternating conditions, the porous hard TiCN coating was prepared by a combination of multi-arc ion plating and oblique angle deposition. The study found that when the titanium target current was reduced from 80 A to 60 A, the pore size of the porous TiCN coating increased from 0.30 μm to 0.93 μm. In comparison to the low hardness of stainless steel substrate of 3.4 GPa, the hardness of TiCN coatings with pore sizes of 0.93 and 0.30 μm rose to 10 and 22 GPa, respectively. The existence of pores can effectively improve the hydrophilicity of the coatings. However, as the pore size increased, the anti-wear lifetime of the coatings were also decrease. This process was followed by ultrasonication and hydrogen reduction of (NH 4) 2 MoS 4 to infuse MoS 2 directly into the pores to fabricate the TiCN-MoS 2 composite coatings. The findings revealed MoS 2 atomic sheets are randomly embedded in the pores of the TiCN coating. In a stable humidity environment, as the relative humidity increased, the friction coefficient of the TiCN-MoS 2 porous composite coating increased and the anti-wear lifetime decreased. In addition, the anti-wear lifetime of the TiCN-MoS 2 porous composite coating at 20 % relative humidity environment is 128,322 laps, which exceeded the 38,099 laps of the dense TiCN-MoS 2 composite coating. This proved that the porous composite coating had better anti-wear lifetime due to the continuous release of MoS 2 in the pores under low humidity conditions. The tribological behavior of the porous composite coatings was systematically investigated under alternating humidity conditions, with a comparison against the dense TiCN-MoS 2 composite coatings. The porous composite coatings possessed better self-adaptation under alternating humidity conditions, with coefficients of friction of 0.05 and 0.15 at 10 % and 70 % RH air, respectively. A detailed discussion was conducted on the relationship between tribofilm composition and tribological properties under different humidity environments. • Preparation of porous TiCN-MoS 2 composite coating by oblique deposition and heat treatment. • The TiCN-MoS 2 composite coating shows tribological adaptability to environmental humidity. • Changing the titanium target current affects the pore size of the porous TiCN coating. [ABSTRACT FROM AUTHOR]

In this study, C 3 N 4 coating was successfully fabricated on AISI 304 stainless steel by electrochemical deposition method using N-N dimethylformamide (DMF) and KCl as the electrolyte. The influences of DMF concentration on the microstructure, hardness, and wear resistance of the coatings were investigated by scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Vickers hardness tester, and pin-on-disk wear tester. The results indicate that a continue C 3 N 4 coating layer can be formed on the steel surface. Compared to the untreated sample, the surface hardness and wear resistance of the stainless steel can be improved apparently after depositing of C 3 N 4 coating. The hardness and wear resistance of the coatings increase firstly and then decrease with increase of DMF concentration. The coatings fabricated with 50 % DMF possess the highest hardness of 1329 HV 0.05 and the lowest friction coefficient of 0.35 at 5 N. The main wear mechanisms are fatigue wear, abrasive wear, and oxidative wear. Deposition of C 3 N 4 coating conforms to the polarization-adsorption-electrochemical reaction mechanism in the present investigation conditions. [Display omitted] • C 3 N 4 coating can be successfully prepared by electrochemical deposition on AISI 304 stainless steel • C 3 N 4 coatings exhibit the high hardness and wear resistance • Deposition of C 3 N 4 coating conforms to the polarization–adsorption–electrochemical reaction mechanism [ABSTRACT FROM AUTHOR]

Liquid metal corrosion has become a critical issue in lead-cooled fast reactor when the steel encounters lead–bismuth eutectic (LBE). Although various coatings applied in LBE have garnered interest from many researchers, there are few reports on the compatibility of chrome carbide or chromium nitride coatings in LBE. Thus, Cr carbide and Cr-nitride coatings with thicknesses of 80 μm were prepared on 316H stainless steel (SS) to investigate the corrosion behavior in contact with static liquid LBE at 550 °C for 25, 76, and 207 h. These coatings were synthesized via pack chromizing and subsequent gas nitriding. The results showed that a distinct LBE penetration layer appeared on the surface of the as-received 316H SS after exposure to LBE. Pack-chromized coating and pack-chromized + gas nitride coating did not undergo obvious consumption in LBE in the early stages. Cracks in the pack-chromized coating promoted the preferential diffusion of oxygen and Pb Bi. The Cr in the pack-chromized + gas nitride coating slightly diffused outward to combine with oxygen to form Cr-oxide scale on the coating surface. These coatings act as a barrier to LBE corrosion, making the surface of the coating impermeable to LBE. • Cr atoms absorbed by 316 H SS during the chromizing treatment dissolved within the Fe in the substrate and formed a solid solution of Cr in α-Fe. • The outermost layer of the pack-chromized sample consists of Cr 23 C 6 (about 5 μm), with α-Fe (substrate) underneath. • Cr 2 N and CrN generated during the gas nitriding treatment is diffusely distributed inside the α-Fe phase. • The larger grain size of Cr 23 C 6 in pack-chromized coating is more prone to defects as cracks and pores in the normal oxide layer. [ABSTRACT FROM AUTHOR]

Cavitation erosion is a common damage form of hydraulic components. Constructing a cavitation-erosion-resistant layer on the surface of hydrodynamic components can effectively prolong the service life of the equipment. In this study, 304 austenitic stainless steel was machined by a diamond blade under specific processing parameters, and a nanocrystalline layer (304-Nano) was formed by the work hardening during the machining process. The machining process also allowed strain-induced martensitic transformation, creating martensite in the nanocrystalline layer. The nanocrystalline layer had an average grain size of approximately 34.7 nm, showing a Vickers hardness of 600 ± 30 Hv, which was much higher than that of the original 304 austenitic stainless steel (230 ± 14 Hv). After the 15-h cavitation erosion test, the cavitation erosion rate of the 304-Nano sample was only 19.4 % that of the original ordinary 304 stainless steel, showing that the 304-Nano sample has excellent cavitation erosion resistance. Furthermore, the in-situ SEM results showed that the 304-Nano sample could significantly inhibit crack propagation, which was probably attributed to its high density of grain boundaries and ultrahigh hardness. The excellent cavitation erosion resistance of the nanocrystalline layer is expected to be used as a protective material for anti-cavitation erosion applications. [ABSTRACT FROM AUTHOR]

Organic antifouling coatings represent an economical and efficient solution for addressing the marine biofouling. However, their application is constrained by issues of durability and toxicity. Therefore, this study has developed a metal-based antifouling coating by utilizing pre-alloyed copper-bearing stainless steel (Cu-bearing SS) powder in conjunction with high-velocity air fuel (HVAF) technology, aiming to achieve an environmentally-friendly and long-lasting antifouling coating. Compared to the self-polishing copolymer (SPC) coating, the adhesion strength of Cu-bearing SS coating increased to 69.0 MPa, which is approximately a 33-fold increase. The coating also exhibited enhanced wear resistance, the width and depth of the wear track for the Cu-bearing SS coating decreased 42.9 % and 81.0 %, respectively. Furthermore, the coating still demonstrated strong inhibitory effects on typical fouling microorganisms and algae adhesion due to Cu ions release process environmentally-friendly. The electrochemical techniques coupling with surface morphology observations were used to elucidate the antifouling mechanism. The variation trend of coating corrosion current was consistent with the release process of Cu ions, which was directly related to the evolution of the coating surface morphology. The three-stage change in the surface morphology of the 304 L-Cu SS coating contributes to the formation of a cyclic variation trend process of Cu ions. The evolution of surface morphology, accompanied by the controlled release process of Cu ions, had become a distinctive feature of antifouling properties for a metal-based coating. [Display omitted] • The Cu-bearing SS coating is prepared by pre-alloyed powder combined with HVAF. • The coating shows effective antifouling property with lower release rate of Cu ion. • The antifouling coating is environmental-friendly. • The three-stage morphology evolution decides the release process of Cu ions. [ABSTRACT FROM AUTHOR]

A gradient structured (GS) surface layer was fabricated by laser shock peening (LSP) on an AISI 316 L stainless steel (SS), and its wear behavior was investigated. Results show that the GS layer contains ultrafine nanocrystalline, nanocrystalline, ultrafine grain and coarse sub-grain. The cross-sectional microhardness of GS 316 L SS showed a gradient, and the surface hardness reached 4.87 GPa, an increase of 70.99 %, resulting in a 41.4 % increase in wear resistance. The microstructure evolution after wear indicates that the surface structure of GS 316 L SS forms a hardened layer during wear, which in turn effectively resists the wear failure. [Display omitted] • Gradient structured (GS) surface layer was fabricated by LSP on AISI 316L SS. • LSP improves surface nanoindentation hardness by 47.75 %–70.99 %, resulting in the improved wear resistance by 44.4 %. • GS sample surface generates a hardened layer under the wear stress, which in turn effectively resists wear. [ABSTRACT FROM AUTHOR]

The hot corrosion behavior of Co W multilayered oxide-coated FSS430 in molten NaCl-KCl (44.53–55.47 wt%) at 700 °C in an air atmosphere was investigated. The effects of Co W multi-layer oxide coating on the oxidation resistance and hot corrosion resistance of the substrate were studied by analyzing the mass change, corrosion products, surface morphology, and cross-sectional structure. The results showed that the Co W multi-layer oxide coating suppressed the interdiffusion of elements, and thus, effectively reduced the corrosion rate under the experimental conditions from 4.98 × 10−8 to 2.42 × 10−9 (g2·cm−4·s−1). Also, the coating was proved to inhibit the outward diffusion of Cr in the substrate and reduced the hot corrosion caused by the loss of Cr into the molten chloride salts. • The Co-W coating is prepared by electroplating followed with pre-oxidation treatment. • The oxidation products have been investigated to elucidate the Cr loss during the hot corrosion. • The Co-W coating significantly enhances the corrosion resistance against molten NaCl-KCl. • The CoWO 4 layer suppresses the diffusion of Cr and surface degradation, and thus improves the corrosion resistance. [ABSTRACT FROM AUTHOR]

The tribocorrosion of low-temperature plasma nitrided UNS S32750 super duplex stainless steel was investigated according to procedures for passivating materials. Nitrided and non-treated samples were compared through two reciprocating sliding tests in NaCl solution: the continuous test, without significant passive layer growth, and the intermittent one, with repassivation. Open circuit potential and linear polarization resistance (LPR) characterized the electrochemical response. LPR was successfully introduced to evaluate the polarization resistance evolution during the continuous test. Corrosion and mechanical wear components were quantified. The mechanical wear dominated, and nitrided samples showed lower wear volume loss. After the intermittent test, their values were further reduced. Such improvement was explained by the higher load bearing capacity and repassivation ability of the nitrided surfaces. • Tribocorrosion assessment based on recent protocols for passivating materials. • Mechanical and corrosion terms quantification for tribocorrosion wear loss. • An alternative technique for EIS to measure polarization resistance during sliding. • Electrochemical parameters and friction evolution during the tribocorrosion tests. • Nitrided samples showed drastic wear behaviour change due to the sliding condition. [ABSTRACT FROM AUTHOR]

High-velocity oxygen fuel (HVOF) coatings are applied to steel surfaces to prevent high-temperature degradation in coal-fired power and waste-to-energy plants. However, the protective HVOF coating deteriorates in aggressive environments such as combustion gas in coal-fired boilers. In this study, nanocomposite coatings of 80Ni20Cr and nano-rare earth oxides (nano-REOs) of nano-Y 2 O 3 and nano-ZrO 2 particles were sprayed on AISI 304 austenitic stainless steel by the HVOF technique. The high-temperature corrosion of the 80Ni20Cr/nano-Y 2 O 3 and nano-ZrO 2 coated steels (NiCr/n-Y 2 O 3 and NiCr/n-ZrO 2) was investigated and compared with bare steels in a simulated combustion (CO-CO 2) atmosphere. Ultra-low porosity nanocomposite coating at less than 1 % was observed after coating by X-ray nano-computed tomography (nano-CT). The 0.5 wt% nano-Y 2 O 3 and 0.5 wt% nano-ZrO 2 in 80Ni20Cr-based coatings showed oxide dispersion strengthened (ODS) coating layers, confirmed by electron backscatter diffraction (EBSD) and synchrotron X-ray absorption spectroscopy (XAS) techniques. Nanoparticle characteristics and formation mechanisms were explored and presented to close interlamellar pores in the nanocomposite coatings. High-temperature degradation of the two nanocomposite coatings was investigated under a combustion atmosphere of 39%CO-35%CO 2 –26%N 2 at 800 °C for 1–10 h. The corrosion resistance performance of the nanocomposite coatings was better than the conventional 80Ni20Cr and bare AISI 304 stainless steels in the carburisation environments relative to biomass/waste-to-energy plants. Both NiO and Cr 2 O 3 were found in the coating layer but carbide precipitates were not observed. The severity of intergranular corrosion of the coated specimens, measured by a double-loop electrochemical potentiokinetic reactivation (DL-EPR) technique, was around 2 fold lower than bare steel. The corrosion potential of 80Ni20Cr-based coatings increased by up to 2 fold when nano-oxide particles were added. [ABSTRACT FROM AUTHOR]

Post-implant inflammation is a leading factor in the failure of orthopedic implant surgery. Hydrogen therapy is viewed as a medium capable of reducing reactive oxygen species (ROS) to alleviate inflammatory responses. However, existing hydrogen therapy methods have limitations, often involving undesired inhalation, injection, or non-targeted exposure of hydrogen to the body. To address this, the concept of delivering hydrogen precisely using the implant itself has been conducted in this study. Traditional hydrogen treatments for metallic implant materials, such as 316 L stainless steel (316 L SS), can induce hydrogen embrittlement (HE), significantly restricting the potential applications of hydrogenated implants in the biomedical field. Therefore, in this study, the electrochemical cathodic hydrogen charging method was employed to diffuse a hydrogenated layer of approximately 216 ± 31 nm on the surface of 316 L SS. This renders the material minimized by HE and alters its surface properties. Through in vitro and in vivo experiments, an approximately 80 % free radical scavenging rate was achieved. Additionally, significant anti-inflammatory effects were observed in the histological analysis of Femur implantation. This demonstrates that the surface hydrogenation treatment can impart anti-inflammatory properties to metallic implant materials without compromising their inherent material properties, thereby enhancing the success rate of surgical procedures. Schematic illustration of the hydrogenated 316 L stainless steel femoral implant prepared via cathodic charging technique, aimed at mitigating inflammatory response and augmenting osseointegration between the implant and surrounding tissues. [Display omitted] • Hydrogen acts as a therapeutic approach for diseases and inflammation by mitigating oxidative stress. • An innovative surface hydrogenation treatment of 316 L SS implants, imparting anti-inflammatory properties. • The surface hydrogenation of 316 L SS can effectively eliminate reactive oxygen species and reduce inflammation. • Hydrogenated 316 L SS reduces the surface hardness and enhances its bonding strength with biological tissues. [ABSTRACT FROM AUTHOR]

Laser direct deposition is commonly used in repair and remanufacturing due to its advantages of small heat-affected zone, compact structures, and rapid cooling. In this study, stainless steel coatings with different Ni contents were applied on the surface of 24CrNiMo using laser direct deposition. The structure and properties of the cladding layer were analyzed using XRD, SEM, microhardness tester, universal testing machine and ball-disk wear tester. The results revealed that an increase in Ni content led to a transition in the microstructure of the cladding layer from martensitic to austenitic. According to the Creq/Nieq ratio, the coating solidifies in different modes. At a Ni content of 2 %, a region with equiaxed crystals and martensitic structure was observed. Moreover, the hardness of the cladding layer decreased from 446 HV 0.2 to 200 HV 0.2 with higher Ni content. The wear of the cladding layers increases with the increase of Ni element. However, the oxidative wear of the cladding layers can be improved with the addition of Ni. Interestingly, at a Ni content of 2 %, a new martensite + austenite duplex the structure of stainless steel was identified in the cladding layer, which effectively enhanced its tensile strength and plasticity. In addition, with the addition of Ni elements can effectively improve the plasticity of the coating. • Excellent balance between strength and plastic toughness was achieved with combination of 316 L + 410 stainless alloy powder. • The addition of Ni element can significantly improve the microstructure and enhance the plasticity of the cladding layer. • The solidification mechanism of composite stainless steel coating was discussed with different additions of Ni. • The coating exhibited better overall performance with a Ni addition of 2 wt%. [ABSTRACT FROM AUTHOR]

Laser cladding was used to prepare an Al-containing Fe-Cr-C hardfacing alloy layer on a 316 L stainless steel substrate. The effects of Al addition on the elemental distribution, physical phase composition, and properties of the cladding layers were systematically investigated using experimental observations, finite-element simulation, and performance tests. Aluminum promoted the flow and elemental homogenization of the molten pool, leading to a more dispersed carbide distribution. Aluminum increased the thermal conductivity of the material and accelerated the cooling rate of the melt pool, which suppressed the eutectic reaction L → γ + (Fe,Cr) 7 C 3 and promoted the peritectic reaction L + (Fe,Cr) 7 C 3 → γ + (Fe,Cr) 3 C. Consequently, the (Fe,Cr) 7 C 3 content decreased, whereas that of (Fe,Cr) 3 C increased. Aluminum improved the stability of ferrite and promoted its formation. The Al addition resulted in fine-grain, load-transfer, dislocation, and Orowan strengthening, thereby improving the hardness and wear resistance of the Fe-Cr-C hardfacing alloys. Dislocation and Orowan strengthening were the largest contributors, followed by fine-grain and load transfer strengthening. • High-performance Al-containing Fe-Cr-C hardfacing alloy layer was fabricated. • Al promoted the production of (Fe,Cr) 3 C carbide in the Fe-Cr-Al-C cladding layer. • Inexpensive Al improved the performance of Fe-Cr-Al-C cladding layer. [ABSTRACT FROM AUTHOR]

A fluorine-free and time-saving process was developed to prepare superhydrophobic (SHP) surface of 304 stainless steel (SLS). Dilute aqua regia and hydrogen peroxide solution were used to construct rough micro-nanostructure on the 304 SLS surface, followed by modification with stearic acid. The effects of various etching and modification parameters on the surface wettability of SLS were examined in order to achieve high surface roughness and low surface energy. The results indicated that the molar ratio of H+/H 2 O 2 showed the most significant influence on the water contact angle (WCA) of SLS. The optimal SHP with a maximum WCA of 158.3° and a sliding angle (SA) of 2.3° could be achieved at the etching time of 30 min, the molar ratio of H+/H 2 O 2 = 1/0.4, the stearic acid concentration of 0.03 mol/L, the modification time of 3 h, and the modification temperature of 70 °C. The long-term stability, wearing durability, thermal stability, and corrosion resistance of the optimal SHP sample were examined, and the results indicated that there was only a slight change in WCA and SA after exposing the sample in air for 75 days, that the sample could keep SHP property after abrasion for 300 cm under a load of 1000 g, that the sample showed good thermal stability at temperature lower than 200 °C, and that the corrosion current density of the SHP SLS decreased by about 2 orders of magnitude compared to the raw SLS, with a corrosion inhibition rate of 98.6 %. The good performance of the SHP SLS in water repellency, durability, abrasion resistance, and corrosion resistance could greatly extend the application potential of SLS. [Display omitted] • A fluorine-free, fast method of fabricating superhydrophobic steel surface was developed. • The maximum contact angle of 158.3° and sliding angle of 2.3° were achieved. • H+:H 2 O 2 ratio showed the greatest influence on the water contact angle of stainless steel. • There was excellent durability, abrasion and corrosion resistance for the prepared sample. [ABSTRACT FROM AUTHOR]

The study focused on investigating the phenomenon of stress corrosion cracking induced by H 2 S, while also examining the influence of low-temperature oxy-nitriding (LTON) surface modification on the diffusion behavior of hydrogen atoms through electrochemical hydrogen charging experiments. Following the hydrogen charging process, the concentration of diffusible hydrogen in the base material (BM) was measured at 5.41 ppm (ppm), which reduced to 1.10 ppm after implementing LTON treatment. Clearly, the surface-modified layer effectively hindered the diffusion of hydrogen atoms within the steel substrate. In the case of BM specimens exposed to H 2 S stress corrosion, the duration of exposure significantly impacted the formation of corrosion products. Additionally, the externally applied tensile stress played a pivotal role in the cracking behavior, as increasing stress levels led to the emergence of deformation bands outside the C-ring and ultimately initiated cracks at the base of the pits. Notably, H 2 S stress corrosion pits accumulated oxides and sulfides. Excessive hydrogen supersaturation potentially induced localized plastic deformation. Furthermore, due to the presence of sulfide ions, hydrogen atoms could not recombine to form hydrogen molecules, resulting in an accumulation of hydrogen atoms on the steel surface. The diffusion of hydrogen atoms within the steel material strongly influenced the initiation and propagation of stress corrosion cracking. Importantly, the surface modification layer established by LTON treatment exhibited remarkable capability in enhancing the steel material's resistance against H 2 S-induced stress corrosion. This was achieved by effectively preventing acidic medium attack and impeding the penetration of hydrogen atoms. • In comparison to 304 stainless steel, the electrochemical hydrogen charging of the LTON modified layer reduced the hydrogen content in the sample by 80%. • The H 2 S stress corrosion cracking behavior of austenitic stainless steels was investigated to reveal the transformation mechanism of cracks under different corrosion times and stresses. • The composite S-phase layer formed after LTON treatment can significantly improve the stress corrosion performance of stainless steel and prevent the penetration of hydrogen atoms. [ABSTRACT FROM AUTHOR]

Thermal management of electronic products and communication equipment is a key bottleneck restricting the integration of products, and high-performance thermal management materials are an effective means to solve this problem. In this study, graphene prepared by liquid phase exfoliation was used as a functional additive material to successfully prepare a graphene high-thermal-conductivity coating material on stainless steel substrates for enhanced cooling performance. The research found that the thermal conductivity of different coating materials with different graphene contents significantly varies, and when the graphene content is 15 %, the thermal conductivity can reach as high as 9.499 W/(m·K), which can rapidly achieve heat dissipation. Considering the actual working conditions of the thermal coating, the comprehensive performance of the coating was tested, and it has excellent corrosion resistance and excellent temperature cycling resistance. Under experimental conditions, after adding the thermal coating to the stainless steel substrate, its cooling effect significantly improved. Compared with uncoated blank samples, the maximum temperature difference during heat transfer under room temperature can reach 11 °C, and the maximum temperature difference under −80 °C can reach 19 °C. This study's coating has potential application prospects in the field of thermal management. [ABSTRACT FROM AUTHOR]

In this work, titanium‑carbon (Ti C) based coating is deposited on AISI-420 martensite stainless steel samples to improve surface properties. The coating is deposited using a graphite cathodic cage equipped with a titanium lid, which acts as a source of carbon and titanium. The hardness of samples (untreated hardness of 220 HV 0.25) is increased up to 1337 HV 0.25 and 1524 HV 0.25 by coating deposition at cathodic (base plate connected with cathodic cage) and floating potential (with no external potential). The sample treated at cathodic potential exhibits expanded martensitic phase due to diffusion of carbon atoms. In contrast, additional TiC and chromium carbide Cr 23 C 6 peaks are formed while treated at floating potential. The thickness of carburizing layer is 80 and 77 μm, when the coating is deposited at cathodic and floating potential, respectively. The wear volume of the untreated sample (1200 × 10−4 mm3) is reduced to ∼ (20 × 10−4 mm3) after the coating deposition, and the friction coefficient is also reduced due to the coating deposition. A significant decrease in corrosion rate is also observed, specifically at floating potential. It suggests that Ti-C-based coating using this modified cathodic cage plasma deposition (CCPD) is beneficial for the hardness, wear, and corrosion resistance of AISI-420 steel. • Ti C based coating is deposited on AISI-420 steel to improve surface properties • A novel technique is introduced and exceptional surface properties are obtained • Graphite cathodic cage with a titanium lid is used in cathodic cage plasma deposition • Hardness, wear resistance and corrosion resistance are improved by this coating. [ABSTRACT FROM AUTHOR]

The impact of plasma carburizing treatment on the erosion wear resistance of AISI 420 martensitic stainless steel (MSS) was studied. Experiments were carried out varying a broad spectrum of erosion parameters, including impact velocity, impact angle, and exposure duration. Both slurry and liquid impingement erosion were employed in the experiments, with testing conducted using both distilled water and saline solutions to assess the combined effects of corrosion and erosion wear. Compared to untreated samples, a significant improvement in the erosion wear resistance of AISI 420 MSS due to low-temperature plasma carburizing treatment was observed for all tested conditions. The observed performance enhancement can be attributed to the formation of the carburized layer, constituted of the α' C and Fe 3 C phases. Results also highlighted that the severity of the tribosystem was significantly influenced by the test solution characteristics. A marginal increase in severity was observed upon introducing the saline solution, while a more substantial severity increase occurred with the addition of solid particles in the test fluid. The specimens' mass loss was increased by increasing impact velocity, following a simple potential relationship, and with impact angle, following a first-degree linear equation. In the case of the exposure time, the mass loss curves depended on the test environment. For solutions containing quartz particles, an additional final stabilization stage was observed in addition to the acceleration stage observed in the absence of abrasive component. This phenomenon was attributed to surface work hardening induced by the impact of solid particles. Regarding wear mechanisms, samples tested only with distilled water displayed erosion flow marks. Those containing distilled water and NaCl exhibited not only flow marks but also pits. Lastly, solutions containing solid particles additionally presented features of plastic deformation, lip formation, craters, indentations, and extruded material. • Low-temperature carburizing effect on AISI 420 MSS erosion resistance was assessed. • Experiments in slurry and liquid impingement erosion environments were conduct. • Distilled water and saline solution were the studied environments. • Impact velocity and angle, and exposure time were the investigated parameters. • Mass loss exponentially increased with impact velocity, linearly with impact angle. [ABSTRACT FROM AUTHOR]

In micro-injection molding, polymer/mold interface adhesion may cause severe deformation or damage of micro features on the molded products. To reduce the interface adhesion and improve the molding quality of polymer microfluidic chip, Ni-P-PTFE (polytetrafluoroethylene) ternary composite was adopted to electroform mold insert with self-lubricating properties. The influence of phosphorous acid concentration on the composition and performance of Ni-P-PTFE composites was systematically investigated. Our results demonstrated that the content of P and PTFE particles in the composites raised with an increase in phosphorous acid concentration. Elevated phosphorous acid concentration adversely affected the current efficiency and slowed down the deposition rate, allowing sufficient contact time for PTFE to transfer and adsorb onto the electrode surface. The hardness of the deposited nickel increased from 310 HV to 510 HV in the Ni-P-PTFE composites. Furthermore, the Ni-P-PTFE composites demonstrated excellent self-lubricating properties, showcasing friction coefficients of 0.15 and 0.25 during the initial and steady stages, respectively, representing a notable reduction of 66.7 % and 64.3 % compared to pure nickel. This study provides a novel approach to fabricate molds with self-lubricating properties, which contributes to the high-precision injection molding of polymer-based micro devices. The electrodeposited Ni-P-PTFE ternary composites show good self-lubrication and high wear resistance properties. [Display omitted] • Increasing H 3 PO 3 concentration (8–32 g/L) raises P and PTFE content in Ni-P-PTFE. • The maximum hardness of electrodeposited Ni-P-PTFE composites reaches 510 HV. • Ni-P-PTFE composites show low friction coefficients against stainless steel. [ABSTRACT FROM AUTHOR]

Erosion-corrosion is a significant concern across industries, impacting equipment lifespan and efficiency. When erosion-corrosion occurs, the resulting damage becomes complex, often leading to greater mass loss than that observed with erosion or corrosion alone. Martensitic stainless steels (MSSs) are commonly used in such environments due to their favorable combination of mechanical and corrosion resistance. However, under severe tribocorrosive conditions, it is necessary to apply surface treatments to prevent rapid steel degradation. Carburizing treatment is known to independently enhance the corrosion and erosion resistance of MSS. Nonetheless, there is a limited understanding of the impact of carburizing on the synergy between corrosion and erosion in such steels. In this study, we examined two different tribocorrosion conditions, assessing the resistance to slurry erosion and liquid impingement erosion for both carburized and non-carburized AISI420 MSS specimens exposed to a corrosive agent (from an electrochemical test using a 3.5 %-NaCl solution). To provide a basis for comparison, a static corrosion test was also performed to evaluate the environmental impact, with the electrolyte at rest, without flow or particles. Our findings revealed that the carburized layer is responsible for reducing the corrosion current density and increasing corrosion potential of AISI420 MSS. In contrast, slurry and liquid impingement erosion result in an increased corrosion current density and a decreased corrosion potential. The parameters Ω and Ω' (role of carburizing on the relationships between 'slurry erosion and corrosion' and 'liquid impingement erosion and corrosion' mechanisms interaction, respectively) demonstrated that carburizing application mitigates the impact of slurry and liquid impingement erosion, respectively. Additionally, the carburizing treatment reduces the corrosion rate, total mass loss, and erosion-induced mass loss of the studied samples, minimizing the synergy between erosion and corrosion. Finally, the interactions between the degradation modes reveal that erosion predominantly governs the AISI420 MSS deterioration process. • Assessment of low-temperature carburizing on AISI 420 steel tribocorrosion behavior • Experiments in slurry and liquid impingement erosion environments were conducted. • Increased corrosion rates were determined for electrolyte flow with solid particles. • Erosion governs carburized AISI 420 steel deterioration in tribocorrosion. • Carburizing mitigates slurry and liquid impingement erosion effects on corrosion. [ABSTRACT FROM AUTHOR]

The increasing demand for energy production has expanded oil and gas extraction, particularly in harsh exploration sites with highly corrosive media. In the Brazil's pre-salt layer, rich in oil reserves, high NaCl content and CO 2 presence may induce sweet corrosion. Corrosion resistant alloys are often used for better performance, and among them, austenitic stainless steels (SS) offer good balance of cost and properties. However, pre-salt acidic and salty environment may induce localized corrosion, making protective coatings a viable option to prolong the lifespan of components exposed to these environments. Diamond-like carbon (DLC) coatings are a great alternative, as besides being chemically stable, they improve mechanical properties of the coated material, such as higher hardness and wear resistance and lower friction coefficient. Therefore, the performance of different types of DLC on the anti-corrosion protection of SS was evaluated. Four DLC types were tested: a hydrogenated amorphous DLC; a multilayered film (DLC-M); and films with fluorine (DLC-F) and silicon (DLC-S). The films showed chemical and structural differences, evidenced by Raman, SEM/EDS and XPS analysis. Their tribological performances were evaluated through scuffing resistance tests; the base DLC showed the highest resistance, followed by DLC-F and DLC-M. DLC-S films didn't exhibit satisfactory tribological performance. For corrosion characterization, potentiodynamic polarization tests were conducted in NaCl and CO 2 -saturated NaCl solutions. In the NaCl tests, DLC films exhibited impressive anti-corrosion properties, with DLC-F delivering the highest performance, followed by DLC-M, DLC-S, and base DLC. 316 L SS showed high corrosion susceptibility in the CO 2 -saturated solution, but the coatings also improved corrosion resistance in this setting. The DLC, DLC-S and DLC-M showed similar E corr and j corr values, while DLC-F demonstrated superior corrosion resistance with higher E corr and lower j corr values. [Display omitted] • Modifying DLC to multilayered or doped films improves its corrosion resistance. • Fluorine addition does not reduce the scuffing resistance of the films. • Fluorine doping appears to reduce the quantity of defects, like micro-detachments and pinholes, more than other solutions. • Adding silicon with HMDSO leads to great changes in the film structure. [ABSTRACT FROM AUTHOR]

Nitriding treatments at low temperatures (<450 °C) are receiving increasing interest for the surface engineering of stainless steels due to the possibility of producing supersaturated solid solutions of nitrogen in the iron-based lattices, known as "expanded" phases. In this study this treatment was applied to AISI 430 ferritic stainless steel with the aim of clarifying the characteristics of the modified surface layer, and in particular the microstructure and phase composition. The formation of expanded ferrite caused high compressive stresses, so that local plastic deformation phenomena occurred, observable as microstructural changes (slip lines, grain swelling) both at the surface and in the section of the samples. Moreover, the formation of a nitrogen-containing hexagonal close-packed phase, dissimilar to ε-nitride, was reported for the first time for low-temperature nitrided ferritic stainless steels. It is suggested that this phase might be a N-rich expanded ε ′-martensite, which formed from expanded ferrite due to a bcc-to-hcp displacive transformation and it remained in the microstructure owing to the residual compressive stresses and nitrogen and chromium solubilization. The presence of this phase contributed to the increase of surface microhardness together with expanded ferrite. The assessment of the corrosion behaviour in 3.5 wt% NaCl aerated solution by means of electrochemical impedance spectroscopy analysis and potentiodynamic measurements showed that, when the modified surface layer consisted only of expanded ferrite, impedance values and corrosion potential had a marked increase and corrosion current density decreased, as compared to those of the untreated steel, suggesting an enhancement of the resistance to general corrosion. On the contrary, when a heterogeneous modified layer formed (expanded ferrite and N-rich expanded ε ′-martensite), a worsening of corrosion resistance was observed. • When expanded ferrite forms, local plastic deformations occur in the modified layer. • Due to bcc-to-hcp transformation, expanded hcp ε ′-martensite may also form. • Expanded ferrite and expanded hcp ε ′-martensite increase surface hardness. • When only expanded ferrite forms, resistance to general corrosion is improved in NaCl solution. • The presence of expanded ε ′-martensite causes a worsening of corrosion resistance. [ABSTRACT FROM AUTHOR]

Conventional carburizing treatments of steels are usually carried out above 550 °C thus they are not suitable for austenitic stainless steels because surface hardening is achieved to detriment of corrosion resistance. To overcome this drawback different carburizing treatments at lower temperature have been developed and among them one of the most efficient is a plasma assisted process at 475 °C. With respect to austenitic stainless steels produced through traditional processes additive manufacturing allows to obtain mechanical parts of complex shape with enhanced strength and without loss of ductility. However, for certain applications the components still suffer of limited hardness and wear resistance. In this work the plasma assisted process at 475 °C has been employed to treat the 316 L steel manufactured by Laser Powder Bed Fusion (L-PBF) with the aim of improving its tribological behavior. The treatment time was 7 h and gas mixtures (CH 4 + H 2) with different amounts of CH 4 have been used. The samples were then submitted to wear tests in pin-on-flat (POF) mode at room temperature with applied loads of 10 N and 20 N. The surface characteristics were examined by scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), Raman spectroscopy (RS), glow discharge optical emission spectroscopy (Rf-GDOES), and X-ray photoelectron spectroscopy (XPS). The results show that plasma treatments induce the formation of a ~ 25 μm thick layer of expanded austenite (S-phase) that is covered by a diamond like carbon (DLC) over-layer of ~2 μm. Such over-layer exhibits a complex sub-structure: the inner part consists of amorphous C (sp2 bonds) with a degree of topological disorder depending on the gas mixture whereas in the external part both sp2 (graphite-like) and sp3 (diamond-like) bonds are present with relative amounts changing with the distance from the surface. Independently on the gas mixture used in plasma treatment, all the samples exhibit a wear resistance much better than that of the untreated material. Moreover, wear resistance also depends on plasma treatment conditions: the greater the CH 4 content, the lower the wear resistance. The results have been discussed by considering the intrinsic DLC brittleness that fractures and detaches from the metal surface during the tests thus hard debris take part to the wear process acting as abrasive particles. • The investigated material is 316 L steel manufactured by L-PBF. • Its surface was hardened by low temperature carburizing treatments assisted by plasma • Affected surface consists of a 25 μm thick layer of S-phase covered by a thin DLC layer • In the inner part of DLC C exhibits sp2 bonds whereas in the external one sp3 bonds. • All the treated samples exhibit a wear rate much lower than that of original material • Wear rate increases with CH 4 content in the gas mixture [ABSTRACT FROM AUTHOR]

This study presents an interesting result based on the laser beam irradiation of austenitic steels in an open atmosphere, which enables the formation of a surface layer comprising a nitrogen solid solution rather than an oxide. First, a focused nanosecond pulsed Nd:YAG laser beam with a laser energy of 400 mJ·pulse−1 was used to irradiate an AISI 316 stainless steel. This formed a surface layer of ~3 μm thickness with ~12 at.% nitrogen solid solution, thereby enhancing the hardness of the AISI 316 stainless steel surface to ~380 HV, nearly twice that of the untreated surface. Consequently, wear resistance was improved by preventing plastic deformation and abrasive wear. Thereafter, similar laser beam irradiation of Inver42® and Kovar® steels resulted in the formation of nitrogen solid solution layers with a thickness of ~1.5 μm, which is lower than that of AISI 316 steel. Furthermore, their nitrogen contents were reduced to ~6 at.%. Consequently, the improvement in the surface hardness of the Inver42® and Kovar® steels was less than that of the AISI 316 stainless steel. These differences were attributed to their alloy compositions; for instance, Cr, which has a high affinity for nitrogen, might trap the available nitrogen, thereby contributing to an increase in the nitrogen content. • A laser process for austenitic steels to form wear-resistant surfaces is presented. • A focused nanosecond pulsed laser beam was irradiated on austenitic steels. • A surface layer with a nitrogen-solid solution was formed even in an open atmosphere. • The hardness of an AISI 316 stainless steel surface was enhanced nearly twice. • Wear resistance was improved by preventing plastic deformation and abrasive wear. [ABSTRACT FROM AUTHOR]

This study evaluated the corrosion behavior and anti-inflammatory activity of brushite (BS or DCPD, CaHPO 4 ·H 2 O)/hydroxyapatite (HAp, Ca 10 (PO 4) 6 (OH) 2) coating on sulfuric acid (H 2 SO 4) treated 316L stainless steel (SS). The coating was applied using the electrodeposition process on untreated and H 2 SO 4 passivated 316L SS surface. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS) to obtain crystal and electronic structure as well as morphological and compositional information of the coated 316L SS. Electrochemical impedance spectroscopy (EIS) tests were performed in 0.9 % sodium chloride (NaCl) solution and compared with the pristine (P316L), H 2 SO 4 treated (T316L), untreated/BS/HAp coated (BHP316L) and treated/BS/HAp coated (BHT316L) 316L SS specimens. The anti-inflammatory activity was carried out for the coated samples by the protein denaturation method. The results showed that the BS/HAp coating on H 2 SO 4 treated 316L SS (hereafter, denoted as BHT316L) were susceptible to corrosion attack against 0.9 % NaCl solution. Additionally, the anti-inflammatory activity of the BHT316L was found to be lower compared to control (sodium diclofenac), indicating that particular concern should be given to H 2 SO 4 treated 316L SS as the corrosion products formed by this surface modification may cause harmful effects in the human physiological environment. [Display omitted] • A biphasic calcium phosphate phase precipitated under the electrodeposition conditions. • The relationship between surface morphology and corrosion resistance is investigated. • SO2− 4 weakens passive film of 316L SS in 0.9 % NaCl solution of pH 6. • SEM images corroborate the characteristic of low Rp in the T316L specimen. • The BS/HAp coating on the 316L SS sample treated with H 2 SO 4 increases protein denaturation. [ABSTRACT FROM AUTHOR]

Cold spraying is a well-established coating fabrication method for metals onto metallic substrates. Over the past decade, there has been a growing interest in its application as a deposition technique for hydroxyapatite (HAp) coatings due to its lower processing temperatures compared to conventional coating manufacturing techniques. HAp coatings are ceramic coatings employed in biomedicine for their biocompatibility and osteoconductive properties. The deposition of ceramic coatings using cold spraying remains a challenge due to the brittle nature of these materials when subjected to high-velocity solid-state impacts. In the present study, HAp deposits were produced via low-pressure cold spraying onto 316 stainless steel under various processing conditions to induce different energy states upon impact and elicit distinct responses in the deposited material. The morphology of the deposited HAp particles was examined after single-track experiments to comprehend the characteristics of the particles adhering to the substrate surface after each experiment. The study was supplemented with impact energy calculations, which allowed the establishment of processing windows to form HAp deposits and coatings. A cold-sprayed HAp coating was successfully obtained within the suggested range of experimental conditions based on energy calculations. • Agglomerated spherical and irregular HAp deposition behavior was studied by LPCS. • A deposition window for HAp deposition by LPCS was established. • The main key processing variables on the HAp deposition by LPCS were identified. • Processing variables to predict HAp deposition efficiencies were used. • A simplified model was employed to build-up a deposition window. [ABSTRACT FROM AUTHOR]

Multi-principal element alloy (MPEA) films demonstrate superior corrosion resistance and tribological properties, which have substantial potential for applications in marine engineering equipment. In this study, the TiNbZrN x MPEA nitride films were successfully deposited on 316 L austenitic stainless steel by direct current (DC) magnetron sputtering at various nitrogen flow ratio (R N2). The phase, composition, microstructure, corrosion and mechanical behaviors were investigated in detail. The results showed that the phase transitioned from amorphous to amorphous/nanocrystalline as R N2 increased. The TiNbZrN x films deposited at R N2 = 0.15–0.4 exhibited better corrosion performance in the electrochemical and salt spray tests. The R N2 = 0.4 film presented the optimal corrosion resistance, with the lowest self-corrosion current density (0.249 μA/cm2) and the largest passivation zone (from OCP to >1.2 V SCE). The amorphous/nanocrystalline film deposited at R N2 = 0.2 showed a remarkable nanohardness of 7.03 GPa and adhesion strength of 18.86 N. The strengthening effect can be attributed to the interstitial dissolution of nitrogen atoms among the metal atoms. The formation of nitride nanocrystalline phases and the existence of interfaces can effectively improve the plastic deformation ability of amorphous alloy films. This work provides theoretical guidance for the development of MPEA nitride films with tunable properties for key moving parts in marine equipment. [Display omitted] • The relationship between the film structure and performance was discussed. • Corrosion resistance and mechanical behaviors were comprehensively enhanced at appropriate nitrogen content. • The mechanism of amorphous/nanocrystalline strengthening of TiNbZrN x films was revealed. • The composition of the passivation layer was confirmed by XPS analysis. [ABSTRACT FROM AUTHOR]

Plasma carburizing has emerged as a potent technique for improving the wear resistance of stainless steels, and sustaining or improving corrosion resistance through a suitable choice of process parameters. This study evaluated the impact of plasma carburizing time and temperature on the tribological behavior of AISI 420 martensitic stainless steel through dry-sliding wear tests in a ball-on-disk configuration. Two different treatment sets were conducted to assess the impact of carburizing time and temperature on the wear performance of the treated AISI 420 steel. The first group encompassed treatments at temperatures spanning from 350 to 500 °C, with fixed treatment times of 8 and 12 h. The second group involved treatments at a temperature of 400 °C for durations spanning 12 to 48 h and at temperature of 450 °C for durations between 4 and 16 h. To facilitate the discussion of wear test results, microstructural analysis was performed using metallographic analysis, X-ray diffraction, and microscale hardness measurements. Microstructural characterization results revealed that the carburized surface consists of an outer layer followed by a diffusion layer. The diffusion layer is primarily composed of the α′ C phase, while the outer layer contains α′ C and Fe 3 C (for low-temperature and short-time treatments) and Cr/Fe-carbides primarily formed due to the α′C decomposition into Fe–α phase (for the studied higher-temperature and longer-time treatments). Wear test results suggest that the surface structure and composition of the treated material exert substantial influence on its tribological behavior. Carburized layers free from Cr-carbide precipitation exhibit lower wear and friction coefficients. The decomposition of α′ C into Fe-α and Cr/Fe-carbides leads to an elevation of friction and wear coefficients. Finally, carbon enrichment does not alter the wear mechanism, as both uncarburized and carburized samples exhibited microabrasion and oxidative wear. • Tribological behavior of carburized MSS was valued by dry-sliding test using alumina as counterbody. • Wear and friction coefficients can be decreased by suitably selecting the carburized conditions. • Cr-carbides precipitation-free carburized layers have lower wear and friction coefficients. • Carburizing at 450 °C for 8–12 h produces the surfaces with the best tribological performance. • Micro-abrasion and oxidative wear are the principal failure mechanisms operating on carburized MSS. [ABSTRACT FROM AUTHOR]

The widespread application of AISI 304 austenitic stainless steel is mainly due to its high corrosion resistance. However, its field of application can be expanded by improving its tribological properties. This work deposited thin films on AISI 304 steel substrates through different plasma treatments using a titanium cathodic cage to evaluate which configuration best combines the films' mechanical, tribological, and corrosion resistance properties. The samples were analyzed by X-ray diffraction, Scanning Electron Microscopy, Energy Dispersive X-ray Spectroscopy, Vickers microhardness, Rockwell C adhesion, fixed-sphere micro-abrasion wear, and Electrochemical Impedance Spectroscopy. The simultaneous duplex treatment sample exhibited the best wear resistance results. It was the film with the lowest loss of corrosion resistance compared to the untreated substrate, highlighting the efficiency of this technique in obtaining surfaces with good mechanical, tribological, and corrosion properties obtained in treatment times shorter than conventional duplex treatment. [ABSTRACT FROM AUTHOR]