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The Ni-based WC coatings enhanced by WC particle were fabricated on FV520B by plasma cladding device. The influence of magnetic force on the microstructure and performance of the coating was investigated. If the magnetic field does not exist, the microstructure of coating is a cluster of block-shaped structures; it is observably different from the dendritic and crumbling snowflake-like structures formed under transverse and longitudinal magnetic fields. The WC particles were distributed at the grain boundary. With the effect of longitudinal magnetic field, wear resistance and erosion resistance of coatings improved markedly. When axial magnetic field intensity came to 38 mT, the microhardness of coatings reached a maximum value, 720 HV0.2. Electron probe microanalyzer (EPMA) indicates the metallurgical combination at the interface and element interdiffusion happened between the coating and substrate. [ABSTRACT FROM AUTHOR]

Inspired by the high entropy effects of high-entropy components, a novel high-entropy rare-earth zirconate (La 1/5 Gd 1/5 Y 1/5 Sm 1/5 Yb 1/5) 2 Zr 2 O 7 (HEC-LZ) was designed and successfully synthesized in this work. In addition, two binary rare-earth doped zirconates (RE-LZ), (La 1/3 Sm 1/3 Yb 1/3) 2 Zr 2 O 7 (LSYZ) and (La 1/3 Gd 1/3 Y 1/3) 2 Zr 2 O 7 (LGYZ), were proposed using the same rare-earth elements for comparison. The thermal barrier coatings with LZ-based ceramic top layer were prepared by spray granulation, solid-phase synthesis and atmospheric plasma spraying techniques. The as-synthesized LZ-based ceramics are all dominated by the pyrochlore phase. Under 1000 °C, the thermal cycling performances of the three coatings were studied. The microstructure evolution and crack expansion during the failure process were investigated in detail. The strengthening mechanism and the cause of coating spallation are proposed in combination with mechanical properties and thermal matching analysis. The results showed that compared with the undoped LZ coating, the thermal shock life of LGYZ coating, LSYZ coating and HEC-LZ coating is improved by nearly 46%, 27% and 57%, respectively. Due to the characteristics of high randomness, HEC-LZ ceramic has a large lattice distortion than RE-LZ ceramics, resulting in a higher coefficient of thermal expansion and fracture toughness, which contributes to maintaining the structure stability of coatings under thermal stress. [ABSTRACT FROM AUTHOR]

In this work, we adopted a cyclic carburizing method to improve the wear resistance and antifriction properties of 17CrNiMo6 heavy-gear steel. The possibility of achieving cyclic carburization is described in terms of diffusion thermodynamics and carburization kinetics. The results indicated that the phase transmation during cyclic carburization can significantly refine the microstructure, and the change of carbon concentration provides a guarantee for cyclic carburization to obtain a high hardness, dense and thick hardened layer. As the number of cycles increases, the friction coefficient of surface wear of the carburized layer at room temperature gradually decreases, while the wear rate after surface removal of 50 µm is significantly diminished and wear rate was the minimum (0.69 ×10-14 mm3N-1m-1) after 4 cycles carburization. At 100 ℃, the oxidation of wear scars on the surface of carburized layer increases. In the case of oil lubrication, the friction coefficient of the cyclic carburized layer was clearly declined. Wear analysis revealed that the wear mechanism of the circulating carburized layer was mainly abrasive wear and oxidation wear with a small amount of adhesive wear. • Cyclic carburizing was used to tailor the microstructure of heavy-duty gear steel. • The effect of cyclic carburizing on the frictional properties of the material was investigated. • The diffusion thermodynamics and carburizing kinetics were explored. • The tribological behavior was investigated by analysis of surface wear at room temperature/100 °C/oil lubrication. [ABSTRACT FROM AUTHOR]

The new carboxylic acid-neodymium anhydrous conversion films were successfully prepared and applied on the AZ91D magnesium alloy surface by taking absolute ethyl alcohol as solvent and four kinds of soluble carboxylic acid as activators. The corrosion resistance of the coating was measured by potentiodynamic polarization test in 3.5 wt.% NaCl solution in pH 7.0. The morphology, structure, and constituents of the coating were observed by scanning electron microscope, energy dispersivespectrum, x-ray photoelectron spectrum, and Fourier infrared spectrometer. Results show that corrosion resistance properties of samples coated with four different anhydrous conversion films were improved obviously. The corrosion potential increased, corrosion current density decreased, and polarization resistance increased. Among these four kinds of conversion films the one added with phytic exhibits the best corrosion resistant property. The mechanism of anhydrous-neodymium conversion film formation is also analyzed in this paper. It reveals that the gadolinium conversion coating is mainly composed of stable NdO, MgO, Mg(OH), and carboxylate of Nd. And that the sample surface is rich in organic functional groups. [ABSTRACT FROM AUTHOR]

In this work, the effect of the dual-phase microstructure (FCC and Laves phases) of Ni 1.5 CrCoFe 0.5 Mo 0.1 Nb x (x = 0.55 hypoeutectic, 0.68 eutectic and 0.8 hypereutectic) high-entropy alloy coatings on their corrosion and tribo-corrosion behaviors were studied. In a 3.5 wt.% NaCl solution, the FCC phase behaved as anodic sites. With the increase of Nb content, the passive regions of the coatings increased slightly. Mott–Schottky analysis revealed that the improvement in the performance of the passive film is mainly attributed to the reduced point-defect density. The increased Laves phase changed the wear mechanism of the coatings from adhesive to abrasive wear. [Display omitted] • The effect of the dual-phase microstructure on the tribo-corrosion behaviors of the eutectic HEA coatings was studied. • The interaction between FCC and Laves phases in the coatings was revealed by EBSD. • Nb 0.68 and Nb 0.8 coatings exhibited nano-scale pitting sizes. • With the increase of Laves phase, the protective capability of the passive films on the coatings was improved. [ABSTRACT FROM AUTHOR]

Aluminum bronze coatings were prepared on MBLS10A-200 magnesium-lithium alloy substrate by cold spraying technology to improve the surface properties of Mg–Li alloys. The microstructure, phase composition, microhardness, tribological properties and corrosion resistance of the coatings were systematically analyzed. The results show that aluminum bronze coatings are mainly composed of α phase. β phase in the original aluminum bronze powder disappeared in the coating due to the eutectoid transition of β→α + γ 2 during the cold spraying. Compared with the Mg–Li alloy substrate, the aluminum bronze coating exhibits the higher microhardness (222.88 HV 0.3) and wear resistance (friction coefficients, wear track widths and wear mass losses are 0.37, 0.79 mm and 2.47 mg, respectively). The dominant wear mechanism of the coatings was abrasive wear. In the electrochemical test, the corrosion current density of the aluminum bronze coating (3.07 × 10−5 A/cm2) was an order of magnitude lower than that of Mg–Li alloy substrate (6.15 × 10−4 A/cm2), indicating that the coating had superior corrosion resistance. The above analysis confirms that preparing a cold sprayed aluminum bronze coating has outstanding tribological and corrosion resistance properties. • Aluminum bronze coatings were prepared on Mg–Li alloy by cold spraying. • Aluminum bronze coatings are mainly composed of α phase. • The eutectoid transformation of β. →α + γ 2 occurred during the cold spraying process. • The wear and corrosion resistance of Mg–Li alloy are comprehensively improved. [ABSTRACT FROM AUTHOR]

The effects of supersonic particle bombardment (SFPB) on the microstructure, microhardness and wear property of Ti6Al4V alloy prepared by laser metal deposition (LMD) were investigated in this paper. The electrochemical corrosion behaviors of the LMDed Ti6Al4V alloy samples before and after SFPB treatment in 3.5% NaCl solution were measured. The results showed that a gradient severe deformation layer of ~ 350 μm thickness was formed with refined equiaxed grains oriented in various directions on the surface of LMDed Ti6Al4V alloy after SFPB treatment. The microhardness of the deformation layer was significantly increased due to the plastic deformation, grain refinement, dislocations and deformation twins increment. After SFPB treatment, the LMDed Ti6Al4V exhibited higher wear resistance which is about 55.6% decrease in wear loss than that of the untreated sample. Moreover, the corrosion resistance and corrosion rate of the SFPB-treated samples in 3.5% NaCl solution improved due to the finer hexagonal grains and high density of grain boundary in the severe deformation layer. [ABSTRACT FROM AUTHOR]

NiTi, NiTi-4Si, and NiTi-4Si-2YF 3 coatings were prepared on Ti-6Al-4V substrate by laser cladding to obtain composite multilayer protective coating for composite structure. The effects of Si and YF 3 addition on the microstructure, phase composition, microhardness, and phase transformation of the coatings were systematically analyzed. The coatings are mainly composed of NiTi, NiTi 2, and TiN phases. The addition of YF 3 results in the decrease of the dendrite TiN phase in the coating. TEM results show that the core-shell structure is observed in NiTi-4Si coating. The β -Ti phase was surrounded by the shell NiTi 2 phase. After the addition of YF 3 , the core-shell structure was found to disappear. With the addition of the Si element, the eutectic structure was found in the coatings. The eutectic structure is mainly composed of NiTi (B2) and Ti 2 Si phases. According to the SEAD result, there are crystallographic orientation relationships (ORs) between NiTi (B2) phase and Ti 2 Si phase as follows: 1 ¯ 11 B 2 / / 1 ¯ 23 Ti 2 Si. The average microhardness of the NiTi, NiTi-4Si and NiTi-4Si-2YF 3 coatings were at 468.33 HV 0.5 , 499.86 HV 0.5 , and 433.65 HV 0.5 , respectively. At the same time, the uniformity of the NiTi phase in NiTi-4Si-2YF 3 coatings is improved, which is conducive to a more complete phase transition. [Display omitted] • With the addition of Si element, the eutectic structure was found in the coatings. • The addition of YF 3 results in the decrease of the dendrite TiN phase in coatings. • the core-shell structure (NiTi 2 @ β -Ti) is observed in NiTi-4Si coating. • The NiTi-4Si-2YF 3 coating exhibits the lowest microhardness. [ABSTRACT FROM AUTHOR]

• The formation of solid solution phase is promoted by increasing Ta content. • The microstructure evolution mechanism with varied Ta content is investigated. • The RHEA coatings possess the good structure stability below 900 °C. • The stability of passive film is improved by increasing Ta content. [Display omitted] In this work, the novel NiTiCrNbTa x (x = 0.1, 0.3, 0.5, 1) refractory high-entropy alloy (RHEA) coatings were successfully synthesized on Ti6Al4V by laser cladding technology. The effect of Ta content on microstructure, thermal stability, micro-hardness and corrosion resistance of RHEA coatings was investigated in detail. The results showed that NiTiCrNbTa x RHEA coatings were composed of BCC, NiTi 2 -Laves and Cr 2 Nb-Laves phases. With Ta content increasing, the formation of BCC phase was promoted while the precipitate of Cr 2 Nb-Laves phase was affected. The average micro-hardness values of Ta 0.1 , Ta 0.3 , Ta 0.5 and Ta 1.0 RHEA coatings were calculated as ~922.8 HV 0.3 , ~985.1 HV 0.3 , ~851.3 HV 0.3 and ~825.4 HV 0.3 , respectively. The decrease of micro-hardness value might be ascribed to the reduction of hard Laves phase. After annealing at 900 °C for 3 h, the phase compositions of all RHEA coatings remained unchanged but the grains of Cr 2 Nb-Laves phase were refined obviously. Besides, RHEA coatings exhibited excellent corrosion resistance and the minimum corrosion current density was 1.08 × 10−7 A/cm2. Moreover, the secondary passivation phenomenon emerged in Ta 0.5 and Ta 1.0 coatings, and the passive film mainly consisted of the oxidation state of Ti, Cr, Nb, Ta and the sub-oxide state of Nb, Ta. [ABSTRACT FROM AUTHOR]

Alloyed layer with gradient structure was prepared on the surface of 20Cr2Ni4A steel by lanthana-bearing supersonic fine particle bombarding (SFPB). Microstructure features of the surface layer were characterized. Subsequently, the samples were carburized in an ECM vacuum furnace. Based on the experimental observations, the mechanism of promoting the diffusion of carbon atoms by lanthana-bearing SFPB was proposed. It mainly involves the promotion of the structure obtained by lanthana-bearing SFPB on the adsorption and diffusion of carbon atoms during carburization. The promotion mechanism of the rare earth in the alloying layer on carbon atom diffusion was analyzed from the aspects of accelerating mechanism of carbon source decomposition by rare earth, subsurface diffusion channel mechanism and driving force. Experimental evidence and related mechanisms show that, the structure formed by the step of austenitization during carburization and the existence of rare earth are necessary to promote the diffusion of carbon atoms. Therefore, our research results clarify the promotion mechanism of lanthana-bearing SFPB treatment on the diffusion of carbon atoms in the carburizing process, and further useful to adjust the surface structure to promote the application of pretreatment technology in surface modification. [Display omitted] • A surface alloying layer is prepared by lanthana-bearing SFPB. • The alloying layer presents texture characteristics and gradient structure. • The alloying layer improves the interstitial atom diffusion significantly. • Microstructure evolution mechanism for promoting atom diffusion is proposed. [ABSTRACT FROM AUTHOR]

NiTi 98-x Si x C 2 (x = 0, 4, 8 wt%) coatings were prepared on Ti-6Al-4V substrate by laser cladding to improve the surface mechanical properties of NiTi coatings. The effects of Si content addition on the microstructure, phase composition, microhardness, and tribological properties of the coatings were systematically analyzed. The results show that NiTi 98-x Si x C 2 (x = 0, 4, 8) coatings are mainly composed of NiTi, NiTi 2 , TiC, and Ti 5 Si 3 phases. The rod-like phase of Ti 5 Si 3 was found in NiTi 90 Si 8 C 2 coating, while the rod-like phases were found broken. The fragmentation of the rod-like phase is related to the growth of the NiTi phase around it. At the same time, TEM results show that the NiTi (B2) phase and Ti 2 Si second phase are exited in the NiTi 90 Si 8 C 2 coating. Ti 2 Si, which has not been decomposed into Ti 5 Si 3 , remains during the laser cladding process. In addition, the eutectic structure in NiTi 90 Si 8 C 2 coating was observed in some regions. The average microhardness of the NiTi 98-x Si x C 2 (x = 0, 4, 8) coating were at 534.08 HV 0.5 , 598.06 HV 0.5 , and 974.08 HV 0.5 , respectively. The wear resistance of NiTi 98-x Si x C 2 (x = 0, 4, 8) coatings increased with the increased Si content. The NiTi 90 Si 8 C 2 coating exhibits the highest microhardness (974.08 HV 0.5) and wear resistance (friction coefficients, wear trace, widths loss weight, and wear rate are 0.320, ~1.25 mm, 12.2 mg, and 5.78 × 10−6 g/Nm, respectively). In NiTi 90 Si 8 C 2 coating, Ti 5 Si 3 phase plays a significant role in the second phase strengthening to improve its tribological properties. The above analysis confirms that NiTi 90 Si 8 C 2 coating has optimal tribological properties. [Display omitted] • NiTi 90 Si 8 C 2 coatings are mainly composed of NiTi, NiTi 2 , Ti 5 Si 3 , and TiC phases. • The fragmentation of Ti 5 Si 3 phase is related to the growth of NiTi phase around it. • Ti 2 Si phase and the eutectic structure were found in NiTi 90 Si 8 C 2 coating. • The microhardness of NiTi 90 Si 8 C 2 coating is 1.8 times than NiTi 98 C 2 coating. [ABSTRACT FROM AUTHOR]

Welding solidification cracks are considered as critical defects in narrow gap laser welding, and it is of utmost importance to develop reliable measures to suppress them. The fundamental approach to curbing solidification cracks lies in controlling the solidification behavior of the weld. A novel narrow gap laser welding technology is proposed to address this issue by controlling the solidification of the weld with double laser beam in this paper. The influence of process parameters on the suppression of welding solidification cracks is explored. Additionally, the mechanism behind the dual-beam laser's ability to suppress solidification cracks are comprehensively examined through weld formation, molten pool solidification behavior and microstructure evolution. The findings demonstrate that the energy matching of the dual-beam and the spacing between the beams are crucial factors that impact the effectiveness of welding crack suppression. When the beam spacing is greater than 6 mm, this method begins to work on suppressing welding solidification cracks. Three distinct effective modes of crack suppression are identified, namely molten pool expansion, gradient solidification, and weld remelting. Among these, the gradient solidification mode proves to be the most reliable method for suppressing welding solidification cracks, as it facilitates a transformation in the molten pool's solidification mode from "enclosed" solidification to "sequential" solidification. Compared to conventional single-beam Narrow Gap Laser Welding, this approach not only effectively suppresses welding solidification cracks but also improves welding efficiency by nearly doubling the filling speed. [Display omitted] • Inventing a narrow gap laser welding method based on dual-beam gradient control of weld solidification (NGDBLW). • Developing an in-situ observation method for molten pool solidification in weld cross-section. • NGDBLW has three effective modes to inhibit welding solidification cracks. • NGDBLW changes the growth mode of columnar crystals and enhances the tendency of growth along the y-axis. • NGDBLW significantly improves the efficiency of deposited metal. [ABSTRACT FROM AUTHOR]

Refractory high entropy alloy (RHEA) coatings containing W and Ta elements at the same time usually have excellent performance at high temperature, which are promising candidate materials for high temperature protective coating materials. In this work, the effects of W and Ta on the microstructure and performance evolution of TiMoCrW x Ta y RHEA coatings have been investigated. Experimentally, TiMoCrW x Ta y coatings are mainly composed of BCC phase, Laves phase and Ti-rich phase, with W and Ta atoms preferably dissolved in BCC phase. The W atoms promote the formation of dendrites and the growth of rod-like and equiaxed crystals and the Ta atoms promote the formation of cellular crystals and produce the effect of fine crystal strengthening. W and Ta atoms have significant influence on the tribological properties of TiMoCrW x Ta y coatings. The tribological properties of TiMoCrW x Ta y coatings at 800 °C are better than those at room temperature. TiMoCrW x Ta y RHEA coatings follow near-linear oxidation kinetics during the oxidation of 50 h at 800 °C.The oxidation resistance of the coatings first increases and then decreases with the increase of Ta content. Ta 2 O 5 , TiO 2 and other oxides may have a shielding effect on the oxidation of W. In particular, The W 0.3 Ta 0.5 shows the best tribological properties and oxidation resistance, and the mass gain of W 0.3 Ta 0.5 is only 13.4 mg/cm2 after the oxidation test for 50 h. It indicates that TiMoCrW x Ta y coatings can obtain good high temperature performance by optimizing the content of W and Ta in RHEA coatings. This work can provide guidance for the research and application of TiMoCrW x Ta y RHEA coatings. • The Ta atom is preferentially dissolved in the BCC phase and it significantly affects the BCC lattice. • The variable content of W and Ta elements significantly affects the crystal growth rate and precipitation sequence of phases. • The tribological properties of the coatings can be improved by controlling the content of W and Ta elements. • Appropriate addition of W and Ta elements can improve the oxidation resistance of the coatings. [ABSTRACT FROM AUTHOR]

• Inventing a high efficiency hot wire narrow-gap dual beam laser welding (HW-NGDBLW). • NGDBLW changes the solidification behavior of weld pool and suppresses solidification cracks. • Laser plume fluctuates violently and directly heating the wire affects the feeding stability. • Laser plume heating special tungsten wire feeding nozzle to achieve hot wire welding. • HW-NGDBLW significantly improves the efficiency of deposited metal. Porosity, incomplete fusion, and solidification cracks are frequently encountered defects in narrow gap laser welding. How to effectively inhibit welding defects while significantly improving welding efficiency has become the key technical challenge of narrow gap laser welding. In this paper, a new method of high-efficiency narrow gap dual-beam laser welding utilizing laser plume energy radiation to achieve "quasi-hot wire" filling is proposed. The solidification behavior of the molten pool was controlled by dual-beam to realize the reliable suppression of welding solidification cracks. The wire feeding speed and stability of the filler wire were improved by developing a high temperature resistant tungsten wire feeding nozzle. The "quasi-hot wire" filling was realized by the heating effect of laser plume energy radiation on the tungsten wire feeding nozzle. The wire feeding stability, thermal radiation characteristics, laser plume characteristics and weld formation during the welding process were studied. The high-efficiency welding of 120 mm high-strength steel was realized and the micro-structure and mechanical properties of the joints were tested and analyzed. The results showed that the method could effectively suppress the defects of porosity, incomplete fusion and solidification cracks in narrow gap laser welding. Compared with the traditional narrow gap laser welding (NGLW), the laser power was reduced by 10%. The welding speed was doubled, and the wire filling efficiency was increased by more than 1 time. The mechanical properties of the welded joint were comparable to those of the traditional narrow gap welded joints, which solved the prominent contradiction between the quality and efficiency of narrow gap laser welding of thick-wall components. [ABSTRACT FROM AUTHOR]

• High quality Ni-coated graphene powders were prepared by electroless plating. • Modified graphene was preserved in laser cladded coatings. • Modified graphene was conducive to improving the wear resistance of coatings. • Modified graphene significantly improved the corrosion resistance of coatings. In recent years, graphene (Gr) has attracted much attention owing to its excellent reinforcement effects. However, the application of Gr in laser cladded coatings remains a challenge due to the agglomeration of Gr and poor wettability between Gr and the molten metals. To overcome these problems, in this study, Ni modified Gr (Ni@Gr) powders were synthesized by electroless plating method, and Ni@Gr powders reinforced Ni60 (Ni60-Ni@Gr) composite coatings were prepared on the surface of AISI 1045 steel by laser cladding technique. The microstructure, existential state of Gr nanosheets, micro-hardness, wear resistance and corrosion resistance of Ni60-Ni@Gr coatings, Ni60-Gr coatings and Ni60 coatings were studied by SEM, TEM, XRD, Raman, micro-hardness tester, wear tester and electrochemical tester. The results showed that the wettability between the metal matrix and Gr was improved after modification, which promotes the dispersion of Gr nanosheets. The average micro-hardness value of Ni60-Ni@Gr coating was 920.79 HV 0.2 , which was higher than that of Ni60-Gr coatings (843.80 HV 0.2) and Ni60 coatings (777.13 HV 0.2). Compared with Ni60-Gr coatings and Ni60 coatings, the Ni60-Ni@Gr coatings have the lowest friction coefficient and weight loss, indicating the best wear resistance of Ni60-Ni@Gr coatings. The potentiodynamic polarization test and EIS test indicated that the corrosion resistance of Ni60 coatings was significantly improved after adding Gr. More notably, compared with the Gr without modification, the addition of modified Gr contributes to the further improvement of the corrosion resistance of Ni60 coating, which was related to the excellent barrier property of uniformly dispersed Ni@Gr powders in coatings. [ABSTRACT FROM AUTHOR]

The new parameter ε we proposed in this study is to be more conducive to the hardness design of high-entropy alloy coatings. Here, the parameter ε is defined as the ratio of the atomic size mismatch to the atomic stacking mismatch. This parameter can be used as the criterion for measuring the magnitude of lattice distortion caused by the atomic size effect, which reveals the influence of the atomic size effect on the hardness of the alloy. We collected nearly 100 groups of on high-entropy alloy coatings in order to verify the feasibility of parameter ε, and to analyze the relevant data from available literatures by using the parameter ε. We found that the hardness value of the high-entropy alloy coatings showed monotonicity with the ε increased. When ε < 6.4, the phase structure of the coating is mainly fcc phase, the increase in hardness of the coating is smaller with the increments of ε. The opposite of bcc phase as the main phase for ε > 6.4, hardness value of the coating escalates with the increase of parameter ε. Based on this finding, it is suggested that the parameter ε can then be used to design a high-entropy alloy coatings with the desired hardness. • The influence of atomic size effect on the hardness of high-entropy alloy coating is briefly analyzed. • A dimensionless parameters is proposed and tested using available experimental data. • The new criterion is able to predict the hardness of high-entropy alloy metallic coatings. [ABSTRACT FROM AUTHOR]

In this work, a novel Ni 1.5 CrCoFe 0.5 Mo 0.1 Nb 0.68 eutectic HEA coating with nano-lamellar microstructure was successfully designed by binary eutectic compositions strategy, thermodynamic calculation and simple experimental approach. Compared with the predicted eutectic compositions, the actual eutectic composition had a higher Nb content due to the increased solid solubility of Nb in the FCC phase. The Ni 1.5 CrCoFe 0.5 Mo 0.1 Nb x (x = 0.55 hypoeutectic, 0.68 eutectic, 0.8 hypereutectic) HEA coatings were prepared by laser cladding, which were composed of FCC phase with lattice parameter of a = ~3.59 Å and Laves phase with lattice parameter of a = b = ~4.82 Å and c = ~7.80 Å. The FCC phase was enriched in Ni, Cr, Co and Fe elements, while the Laves phase was enriched in Nb and Mo elements. Typical eutectic lamellar and hypoeutectic/hypereutectic microstructures were obtained at the central regions, while the columnar crystals formed at the interfacial regions. The average micro-hardness of Nb 0.55 , Nb 0.68 and Nb 0.8 coatings were calculated as ~573.5 HV, ~665.8 HV and ~715.6 HV respectively. From x = 0.55 to x = 0.8, the wear resistance of Ni 1.5 CrCoFe 0.5 Mo 0.1 Nb x HEA coatings are increased, and the dominant wear mechanism of the HEA coatings transforms from adhesive wear to abrasive wear. Unlabelled Image • A feasible design strategy for laser-cladded eutectic HEA coatings was proposed. • A novel Ni 1.5 CrCoFe 0.5 Mo 0.1 Nb 0.68 eutectic HEA coating with nano-lamellar microstructure was successfully prepared. • Typical eutectic microstructures were obtained at central regions, while columnar crystals formed at interfacial regions. • The Nb content of actual eutectic composition high than that of predicted composition. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) as nano reinforcement has been extensively used to improve the overall performance of metal-based composite coatings. In this work, GO nanosheets with surface modification and magnetic field (MF) assisted electro-brush plating (EBP) technique were employed to construct Ni-based composite coatings with biomimetic structure to improve the corrosion resistance of coatings. The preparation, deposited behavior and some properties of coatings were investigated. The results showed that after surface modification, GO surface carried numerous Co 7 Fe 3 magnetic nanoparticles with the size of 40–50 nm. During the MF assisted EBP process, the co-deposition of CoFe@GO magnetic powders with the reduced Ni atoms contributed to the formation of Ni-CoFe@GO composite coatings with stripe-like structure that resembled the surface morphology of conch. Besides, induced by the synergistic action of MF and electric field, most magnetic powders were distributed regularly in the stripe-like areas. After two weeks exposure to air, Ni-CoFe@GO composite coatings changed spontaneously from hydrophilic for fresh coatings to hydrophobic. This transformation was mainly attributed to the high surface roughness and the adsorption of a lot of hydrocarbons on the stripe-like surface. Moreover, air pockets that resulted from these hydrocarbons formed on the coating surface impeded the diffusion of corrosive media into coatings. Consequently, Ni-CoFe@GO composite coatings exhibited good corrosion resistance. Therefore, the preparation proposed in this work is desirable and has a prospect in further improving the corrosion resistance of GO reinforced Ni-based composite coatings. • A composite method was employed to prepare a new GO-reinforced Ni-based coating. • This coating presented the stripe-like structure similar to conch surface. • GO changed from non-magnetic to magnetic via surface modification. • Ni-CoFe@GO coatings exhibited hydrophobicity and good corrosion resistance. [ABSTRACT FROM AUTHOR]

The surface nanocrystallization layer induced by supersonic fine particle bombardment (SFPB) was obtained on a structural steel. SFPB was applied as pretreatment on the steel prior to the vacuum carburization, for enhancing the tribological properties under various sliding conditions. Varying duration of pretreatment was performed to investigate the influence on microstructure, surface hardness, and tribological behavior of the carburized substrates. Results suggested that 240s of SFPB pretreatment induced finer grain boundaries and higher hardness. A decrease in weight loss and friction coefficient under unlubricated and lubricated sliding conditions indicated enhanced tribological properties of the 240s SFPB nanocrystallized steel after vacuum carburization. Notably, the lowest friction coefficient was achieved under sea water sliding condition, whereas the highest weight loss was obtained. Rolling contact fatigue behavior of the carburized steel with SFPB 240s pretreatment was discussed and Weibull life distribution was proposed in the study. • Surface nanocrystallization layer induced by supersonic fine particle bombardment (SFPB) obtained on structural steel. • 240s SFPB produced a thickest nanocrystallized layer with the highest surface hardness. • Refined carbides with homogenized distribution in the carburized samples pre-treated with 240s of SFPB. • Carburized samples pre-treated with 240s of SFPB showed the lowest weight loss and friction coefficient. [ABSTRACT FROM AUTHOR]

In this work, hot corrosion behavior of air plasma sprayed La 0.8 Ba 0.2 TiO 3-δ (LBT)-YSZ double-ceramic-layer thermal barrier coating exposed to Na 2 SO 4 + V 2 O 5 molten salt at 900 °C for 20 h was investigated. The phase characterization and microstructural evolution analysis of the coating was carried out after the hot corrosion test by using X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The results showed that the LBT-YSZ coating possessed excellent hot corrosion resistance compared with the conventional pure YSZ coating. The conventional pure YSZ coating was completely destroyed after the 10 h test due to the volume change resulting from the adverse phase transition. However, the situation for the LBT-YSZ coatings is completely opposite. The LBT-YSZ coating could prevent the YSZ interlayer underlying the LBT overlayer from densification for at least 20 h. In the LBT overlayer, the double-reaction-layer composed of under dense layer and upper porous layer was formed. In particular, the continuous dense layers with a thickness of ~100 μm formed after 10 h, effectively arresting further penetration of the molten salt. In addition, affected by the diffusion extent of SO 3 gas, the corrosion products of porous layer were composed of Ba 2 V 2 O 7 , LaVO 4 , TiO 2 and BaSO 4 , while those of dense layer consisted of Ba 2 V 2 O 7 , LaVO 4 and TiO 2. The specific mechanism by which the corrosion reaction occurred was proposed based on Lewis acid-base rule and thermodynamics. • A La 0.8 Ba 0.2 TiO 3–δ -YSZ double-layer coating was successfully deposited. • Hot corrosion behavior in Na 2 SO 4 + V 2 O 5 molten salt was investigated at 900 °C for 20 h. • The double-layer coating possessed better hot corrosion resistance than YSZ coating. • The upper porous layer and under dense layer were formed in La 0.8 Ba 0.2 TiO 3-δ layer. • The dense layer could arrest further penetration of the molten salt. [ABSTRACT FROM AUTHOR]

The welding solidification crack is a common welding defect occurring in the narrow gap laser welded high-strength steel joint, which poses a detrimental effect in reducing the weld quality. However, the relationship between the weld geometric characteristics and the metallurgical characteristics with the solidification crack of the narrow gap laser weld is still unclear. In this study, a 20-mm-thick 10Ni5CrMoV high-strength steel with a root gap of 3 mm and groove angle of 1º was used to analyze the single-pass welding process of narrow gap laser welding using high-frequency beam oscillation. The correlation between the weld form factor and the welding solidification crack was discussed, alongside with the clarification on the influence of the welding process parameter on the welding solidification crack, the aim of which was to analyze the causes for the formation of welding solidification crack and explore the effective ways to suppress it. The results showed that the influence of welding process parameters on welding solidification crack could be attributed to change in the form factor of the weld and weld metal solidification crystallization characteristics. The smaller the weld form factor, the larger the area of the opposite crystal growth in the upper part of the weld cross section, and the higher the tendency toward solidification crack formation. Furthermore, the higher welding speed was also likely to have columnar grains with a larger angle of crystallization direction with the centerline. This resulted in a higher tendency of solidification crack formation. Under the test conditions used in this study, a weld form factor φ = 0.8 was considered effective for controlling welding solidification crack. [ABSTRACT FROM AUTHOR]

• High entropy alloys (HEAs) was first introduced in underwater laser wetcladding process process. • The utilization rate of laser energy underwater can be enhanced. • The incorporation of Nb can enhance the corrosion resistance and prevent the expansion of pitting pits. Underwater wet laser cladding technology (UWLC) offers advantages such as short repair cycles, low costs, and independence from drainage equipment, making it highly practical. The exceptional design flexibility of high entropy alloys, combined with the convenience of UWLC technology, presents significant application potential. To assess the feasibility of utilizing high entropy alloys (HEAs) in underwater wet laser cladding, (NiCrCoFe) 100-x Nb x (x = 0, 5, 10) coatings were prepared. This study investigates the effects of Nb addition on the formation characteristics and metallurgical process of (NiCrCoFe) 100-x Nb x HEA coatings. The results show that the addition of Nb promotes the efficient utilization of laser energy underwater by altering the melting latent heat of UWLC materials and enhancing the fluidity of the molten pool. Furthermore, the introduction of Nb element improves the corrosion resistance of the coatings and inhibits the expansion of corrosion pits. This study confirms the feasibility of utilizing high entropy alloys for underwater wet laser cladding and offers new ideas and methods for the underwater online repair of marine equipment. [ABSTRACT FROM AUTHOR]

• The addition of La 2 O 3 presented remarkable grain refinement of DMDed NiTi alloy. • The strength of DMDed NiTi alloy was significantly promoted by La 2 O 3 addition. • The promotion of wear resistance is ascribed to higher degree of superelasticity. Additive manufacturing of NiTi alloys has received significant attention recently, but its insufficient strength and wear resistance need to be improved. In this work, NiTi alloys with and without La 2 O 3 addition were fabricated by direct metal deposition (DMD) technology. The influence of La 2 O 3 addition on the microstructure, mechanical properties and wear resistance of DMDed NiTi alloy was investigated. The results showed that the grain and the microstructure uniformity of the DMDed NiTi alloy were significantly refined and improved respectively after La 2 O 3 addition. Besides, the microhardness and tensile strength were remarkably promoted, which were mainly attributed to the synergistic action of the grain refinement strengthening of NiTi phase and second phase strengthening of NiTi 2 or La 2 O 3 phases. Moreover, the addition of La 2 O 3 significantly improved the wear resistance of DMDed NiTi alloy due to the higher degree of superelasticity and finer hard phase. [ABSTRACT FROM AUTHOR]

The supersonic fine particles bombarding (SFPB) pretreatment is adopted to assist vacuum carburizing for refining the microstructure and improving the mechanical properties of carburized layer. The microstructures, micrhardness and tribology properties of SFPB carburized sample and vacuum carburized sample were studied. The results showed that SFPB pretreatment could form random oriented, ultrafine-grained microstructure and high density dislocations in AISI 9310 steel, leading to the increase of case depth of carburized layer, the refinement of grain size and the promotion of the formation of twin martensite and carbides in carburized layer. Besides, the surface microhardness, maximum residual compressive stress and wear rate of carburized layer were enhanced by SFPB pretreatment, which was attributed to the formation of twin martensite, grain refinement, dispersion strengthening of carbides and the increase of high misorientation angle grain boundary. [ABSTRACT FROM AUTHOR]

N + Cr ions were co-implanted into the carburized 18Cr2Ni4WA steel to improve hardness, wear and corrosion resistance. The microstructures of the samples were characterized by the glancing incidence X-ray diffractometer, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy, respectively. In addition, the mechanical, corrosion and tribological properties were evaluated by nano-indenter instrument, electrochemical corrosion workstation and wear test, respectively. The results showed that after implanting N + Cr ions, a new nano-nitride phase was formed on the surface of carburized steel. Ions implantation process was accompanied by the radiation damage, which led to lattice distortion on the surface of the steel. These changes accordingly made the N + Cr ions implantation layer present high nano-hardness. Meanwhile, the N + Cr ions implantation layer could effectively prevent the synergistic effect of corrosion and friction in seawater environment, and significantly enhance the tribological property of the carburized steels in simulated seawater. • N + Cr ions implanted layer was prepared on the surface of 18Cr2Ni4WA steel. • The tribological properties in simulated seawater were investigated. • The N + Cr implanted layer has higher nano-hardness and better corrosion resistance. • N + Cr implanted layer can resist the synergistic effect of friction and corrosion. [ABSTRACT FROM AUTHOR]

La ion pre-implantation was successfully used to obtain vacuum carburized layer with ultrafine microstructure and higher case depth of AISI 9310 alloy steel. The effect of La ion pre-implantation on microstructure, case depth and hardness of carburized layer was investigated in detail. The results showed that the La 2 O 3 , BCC structure solution of La and lattice defects were introduced into AISI 9310 alloy steel by La pre-implantation. Meanwhile, the pre-implantation can effectively refine microstructure and dramatically improve diffusion coefficient of carbon and hardness of carburized layer. The La 2 O 3 and LaC 2 in situ produced during carburizing can act as potential heterogeneous nucleation sites for γ -Fe phase to refine grain. The higher carbon concentration gradient caused by the inhibition effect of La on C–C bond formation and induction of Cottrell can increase the amount of carbides in carburized layer. The excellent microstructure and higher carbon concentration gradient can enhance short-circuit diffusion to accelerate the carbon diffusion coefficient inducing the increase of hardness of carburized layer. • Carburized layer with ultrafine microstructure and higher hardness was obtained by La pre-implantation. • The carbon concentration gradient and short-circuit diffusion are enhanced by La pre-implantation during carburizing. • The La 2 O 3 and LaC 2 can act as potential heterogeneous nucleation sites for γ-Fe phase during carburizing. [ABSTRACT FROM AUTHOR]

• Nano-ceramic phase was obtained by Ti+N and Zr+N ions implanted and carburized. • Ti+N ions implantation layer expresses better nanomechanical property. • Zr+N ions implantation layer owned superior tribology and corrosion properties. • Corrosion form of Ti+N and Zr+N ions implantation layers are local corrosion. Ti+N and Zr+N ions were implanted into the carburized AISI 9310 layer to improve surface properties. The microstructure, nanomechanics, tribology and corrosion properties were investigated by transmission electron microscopy, glancing incidence X-ray diffraction, nanoindentation, tribology analysis and corrosion test. The results showed that there were a large number of dense metal (Ti or Zr) ceramic phases with ultrahigh nanomechanical property and wear resistance in Ti+N and Zr+N ions implantation layers. Simultaneously, the corrosion type of the carburized layer changed from general corrosion to the localized and pitting corrosion after Ti+N and Zr+N ions implantation. Due to favorable corrosion resistance of the ceramic phases, the corrosion property of Ti+N and Zr+N ions implantation layers have been improved significantly. Comparing with these two ions implantation (Ti+ N and Zr+N) layers, the Ti+N ions implantation layer exhibited better nanomechanical property, while the Zr+N ions implantation layer displayed superior tribology and corrosion properties attributed to element composition and new phase structure. [ABSTRACT FROM AUTHOR]

Based on the two-way diffusion behavior of FeCoCrNi and W elements and the lattice distortion principle during alloy solidification, a new type of HEA wear-resistant coating with Laves phase and hardness gradient was prepared in this work. Analysis results show that the Laves phase has higher hardness and resistance to deformation, while the FCC phase exhibits higher plastic deformation ability. The tribological properties of the coating material under both room- and high-temperature wear conditions are improved by the synergistic effect of the hard Laves phase and the ductile FCC phase. Moreover, the transition effect of the intermediate eutectic layer alleviates the stress concentration during the friction process, and the oxide film shows a strong wear resistant under the room-temperature wear condition. [Display omitted] • The HEA wear-resistant coating with Laves phase and hardness gradient distribution was prepared in situ. • The FCC-Laves dual-phase structure with soft and hard cross has good strength and toughness. • The wear mechanism of W-CC at room temperature is three-body wear with slight oxidation. • The high hardness of Laves phase and the oxidation of FCC phase improve the high temperature anti-friction performance. • When the oxide film is worn at room temperature, it shows a strong wear protection effect. [ABSTRACT FROM AUTHOR]

The friction and wear of bearing cages, sealing rings and other transmission components working in harsh environments such as high vacuum and heavy load directly affect the operational stability and safety reliability of the equipment. Therefore, it is vitally important to improve the tribological properties of machine components. In this paper, NiCrBSi alloy coating, NiCrBSi-30 wt% WS 2 coating and double-layer NiCrBSi-30 wt% WS 2 coating were prepared on 38CrMoAl steel by laser cladding. The results show that a metal sulfide layer is formed on the double-layer NiCrBSi-30 wt% WS 2 coating compared to NiCrBSi-30 wt% WS 2 coating. The NiCrBSi-30 wt% WS 2 coating consists of γ-(Ni,Fe) solid solution, (Fe,Ni) 9 S 8 , Cr 7 S 8 and M 7 C 3 phases. The metal sulfide layer consists of γ-(Ni, Fe) solid solutions, Fe 3 S 4 , Cr x S y and M 7 C 3 phases. The double-layer NiCrBSi-30 wt% WS 2 coating is 4 mm thicker than the NiCrBSi-30 wt% WS 2 coating. The average microhardness values of NiCrBSi coating, NiCrBSi-WS 2 coating and double-layer NiCrBSi-WS 2 coating are 412.6 ± 15.2HV 0.3 , 383.9 ± 14.5HV 0.3 , and 368.6 ± 13.3HV 0.3 , respectively. The average coefficient of friction of the double-layer NiCrBSi-30 wt% WS 2 coating is 0.29, which is 37 % and 14.7 % lower than that of the NiCrBSi coating (0.46) and the NiCrBSi-30 wt% WS 2 coating (0.34), respectively. The wear rate of the double-layer NiCrBSi-30 wt% WS 2 coating is 1.51 × 10−5 mm3/(N·m), which is 47.6 % and 34.9 % lower than that of NiCrBSi coating (2.88 × 10−5 mm3/(N·m)) and NiCrBSi-30 wt% WS 2 coating (2.32 × 10−5 mm3/(N·m)), respectively. Therefore, double-layer NiCrBSi-30 wt% WS 2 coating has the best wear resistance and friction reduction performance at room temperature. A more continuous lubricating film was formed on the surface of the double-layer NiCrBSi-30 wt% WS 2 coating, which explains its lowest coefficient of friction and wear rate. • A metal sulfide layer was formed on top of double-layer NiCrBSi-30 wt.% WS 2 coating. • Formation mechanism and tribological behavior of metal sulfide layer were studied. • A more continuous lubricating film is formed on the metal sulfide layer, resulting in the lowest coefficient of friction(0.29) and wear rate(1.51×10-5 mm3/(N·m)). [ABSTRACT FROM AUTHOR]

Based on the influence of Mo and Nb content on the eutectic degree of FeCoCrNi high-entropy alloy (HEA), this study prepared in-situ HEA composite coatings with a gradient eutectic degree using the principle of element diffusion in the molten pool under a laser beam, namely Mo-CC and Nb-CC. Both of the two coatings were composed of the face-centered cubic (FCC) phase and Laves phase. Within the coating, there was a gradual decrease in the Laves phase and an increase in the FCC phase from top to bottom. The Laves phase in Mo-CC was rich in Mo (21.36 at.%) element and exhibited an orientation relationship with the FCC phase of [ 0 1 ¯ 1 ] Laves //[ 0 1 ¯ 1 ] FCC. The phase interface was a non-coherent crystal plane. The Laves phase in Nb-CC is enriched with Nb (36.15 at.%) element and demonstrated an orientation relationship with the FCC phase of [ 1 ¯ 2 ¯ 1 ] Laves //[ 0 0 1 ] FCC. The phase interface was a semi-coherent crystal plane. Furthermore, the process and mechanism of FCC phase transformation into FCC + Laves phase were elucidated by examining the mixing enthalpy, lattice distortion, and atomic radius difference. In terms of properties, the hardness of Mo-CC and Nb-CC from the top to the bottom section gradually decreased from the outer to inner section. Nb-CC possessed a higher surface average hardness (773.66 HV 0.3) and superior tribological properties compared to Mo-CC. The gradient control method for HEA and the phase structure formation mechanism presented in this study provided valuable insights for the research and development of new HEA coatings. [Display omitted] • Mo-CC and Nb-CC with eutectic gradient were prepared in situ, which were composed of FCC phase and Laves phase. • The difference between Δ H AB mix and δ lead to a transition from the FCC phase to the FCC + Laves phase. • The Laves phase was enriched in Mo or Nb elements, and the strain was concentrated in the Laves phase. • The Laves phase and the hardness gradually decreased from the top to the bottom of the coating. • Compared with Mo-CC, Nb-CC exhibited better tribological properties. [ABSTRACT FROM AUTHOR]

Refractory High Entropy Alloys (RHEAs) have great potential for ultra-high temperature environments and are one of the potential candidates for high temperature applications. In this work, a series of Al 0.75 NbNi 0.1 Mo 0.1 Cr 0.5 Si 0.1 W x (x = 1, 1.5, 2) refractory high-entropy alloy coatings is prepared by laser cladding technology. The microstructure and oxidation behavior at 1000 °C and effect of changing oxidation temperature on oxidation behavior of the coatings is investigated. The results show that Al 0.75 NbNi 0.1 Mo 0.1 Cr 0.5 Si 0.1 W x RHEA coatings are composed of BCC, W 5 Si 3 and AlNi 3 phases. The microstructure of RHEA coatings exhibits dendritic-cellular grain transition with increasing W content. The specific mass gains of coatings due to high temperature oxidation is 65.5 mg/cm2 for x = 1, 8.5 mg/cm2 for x = 1.5 and 14.5 mg/cm2 for x = 2 at 1000 °C for 70 h. After oxidation in 1000 °C for 70 h under air atmosphere, a protective oxide film (such as Al 2 O 3 and SiO 2) adhere around NiWO 4 on the alloy coatings, which impedes the inward oxygen transport. Moderate addition of W elements is found to be beneficial in enhancing the oxidation resistance of coatings. However, excessive addition of W elements prevents the formation of protective oxides (Al 2 O 3 and SiO 2) and reduces the high-temperature oxidation resistance of the coatings. With the increase of oxidation temperature, simple oxides are significantly reduced while compound oxides are increased on the surface of the coatings. The surface appears hill-shaped oxides with the increase of NiWO 4. • The increase in W element content promotes the formation of cellular crystal structure. • The combination of SiO 2 and Al 2 O 3 can form a dense oxide layer. • Al diffuses rapidly to the top of the oxide layer during the oxidation process. • Part of the elemental distribution shows a continuous horizontal band in the oxide film. [ABSTRACT FROM AUTHOR]

• Heat treatment led to the growth of the grain size of the NiTi phase in the coatings. • The spinodal decomposition occurred in the NiTi 2 phase by cryogenic treatment. • The post-treatments affected the phase transformation characteristics of the coatings. • The coating after cryogenic treatment has the highest microhardness. YF 3 modification NiTi-Si coatings were prepared on Ti-6Al-4 V substrate by laser cladding. On this foundation, heat and cryogenic treatments were conducted respectively to explore the effect of after-treatment procedures. The consequence of post-treatment methods on the phase constituent, microstructure, mechanical property, and phase transition characteristics of post-treatment coatings was studied. The phase constituent of the three coatings was roughly the same, composed of NiTi and NiTi 2. The results show that heat treatment led to the coarsening of NiTi phase grain size and increased Si content in the NiTi 2 phase. In addition, due to the rapid cooling rate provided by cryogenic treatment, the spinodal decomposition of the Si element occurred in the NiTi 2 phase. Furthermore, the post-treatments also affected the phase transformation characteristics of the coatings. As the temperature of martensitic transformation is sensitive to the content of Ni element in the NiTi phase, the M s and M f points of the heat treatment coating were slightly higher. In contrast to the heat treatment, the M s and M f points of the cryogenic treatment coating decreased. The microhardness of the three coatings is as follows: cryogenic treatment > original coatings > heat treatment. The cryogenic treatment coating has the highest microhardness due to grain refinement and spinodal decomposition. In addition, the cryogenic treatment coating showed the best wear morphology. [ABSTRACT FROM AUTHOR]

Iron oxide nanoparticles (FeONPs) have been specifically designed for use in biomedical applications by tailoring their properties, micromorphology, and chemical composition through various synthesis techniques. Further modification and functionalization strategies have enabled the incorporation of diverse functional groups or micromorphologies into FeONP-based nanocomposites to meet the demands of specific target applications. FeONP-based nanocomposites improve MRI diagnostic accuracy through dual/multimode imaging and can also be tailored for magnetic particle imaging. Exogenous and endogenous stimuli can enhance drug delivery efficacy. Further research is needed to understand the enhancement effect and design efficient diagnostic and therapeutic agents. Biosafety of FeONP-based nanocomposites is a concern and their bioaccumulation, biodegradation, and bioelimination behavior must be carefully studied for their safe clinical use. Iron-oxide-based biomagnetic nanocomposites, recognized for their significant properties, have been utilized in MRI and cancer treatment for several decades. The expansion of clinical applications is limited by the occurrence of adverse effects. These limitations are largely attributed to suboptimal material design, resulting in agglomeration, reduced magnetic relaxivity, and inadequate functionality. To address these challenges, various synthesis methods and modification strategies have been used to tailor the size, shape, and properties of iron oxide nanoparticle (FeONP)-based nanocomposites. The resulting modified nanocomposites exhibit significant potential for application in diagnostic, therapeutic, and theranostic contexts, including MRI, drug delivery, and anticancer and antimicrobial activity. Yet, their biosafety profile must be rigorously evaluated. Such efforts will facilitate the broader clinical translation of FeONP-based nanocomposites in biomedical applications. [ABSTRACT FROM AUTHOR]

In this work, the CoNiAlBx coatings were successfully prepared on 38CrMoAl steel by laser cladding technology. The effects of B content addition on the microstructure, phase composition, microhardness, and tribological properties of the coatings were systematically analyzed. We found that CoNiAlB coatings were composed of β,γ,and FeB phase. TEM results shown that the orientation relationships between FeB phase and γ phase were [—112]FeB//[12]γ. With the addition of B, the microstructure changed from cellular morphology to dendritic morphology, then generated FeB phase, the transformation of microstructure led to the improvement of the coating: The microhardness improved from 380 Hv 0.3 to 790 Hv 0.3 , the friction coefficient reduced from 0.75 to 0.45, wear rate decreased from 3.59·10−14 m3 N−1 m−1 to 1.34·10−14 m3 N−1 m−1. The wear mechanism of CoNiAlB coatings was changed from only oxidation wear to only abrasive wear, exhibited excellent tribological property. [Display omitted] • FeB phase was appeared in CoNiAlB coatings due to the addition of B. • The crystallographic orientation relationships and d-spacing of two phases were analyzed. • The appearance of FeB phase improved the microhardness and friction property of the coating. • The microhardness was increased by ∼390 Hv0.3, wear rate decreased to 1/3 of the original. [ABSTRACT FROM AUTHOR]

Lanthanum zirconate coatings (La 2 Zr 2 O 7 , LZ) have a high Poisson's ratio and low fracture toughness, making it indescribable for long service life at high temperatures. Rare earth doped lanthanum zirconate (RE-LZ) is an effective way to improve its mechanical properties. In this study, the lanthanum zirconate ceramic coating modified by binary rare earth ((La 1/3 Gd 1/3 Y 1/3) 2 Zr 2 O 7 , LGYZ; and (La 1/3 Sm 1/3 Yb 1/3) 2 Zr 2 O 7 , LGYZ) and multi-principal rare earth modified ((La 1/5 Gd 1/5 Y 1/5 Sm 1/5 Yb 1/5) 2 Zr 2 O 7 , HEC-LZ) was studied, aiming to improve the intrinsic mechanical properties of lanthanum zirconate ceramic coating. By comparing the mechanical properties such as fracture toughness, bonding strength, microhardness dissipation parameter, and solid erosion properties of various types of coatings, the results show that compared with binary rare earth modified coatings such as LGYZ and LSYZ, the elastic modulus of the HEC-LZ ceramic coating is reduced by 4.7–6.3%, the microhardness dissipation parameter (MDP) is increased by 4.8–10.2%, and the fracture toughness is increased by 5.2–7.4%. The HEC-LZ ceramic coating showed favorable toughness and crack resistance. Regarding the erosion resistance of the coatings, the ability of RE-LZ coatings is significantly better than that of LZ coatings, and the erosion rate at 45° and 90° is reduced by 44.9–66.0% and 45.7–62.9%, respectively. • Multi-rare earth doped modified lanthanum zirconate ceramic coating (RE-LZ). • Rare earth modified lanthanum zirconate (LZ) coatings have high plastic deformation capacity. • The modification of multi-rare earths enhanced the fracture toughness of LZ coatings. • The crack resistance of RE-LZ coatings has been greatly improved. • RE-LZ coatings effectively dissipate the energy of erosion particles. [ABSTRACT FROM AUTHOR]

The embrittlement of thermal barrier coatings (TBCs) in a high-temperature service environment inhibits the ability of the top-coat to resist crack initiation and propagation, in which the cracks are generated by erosion or wear of particles, limiting the service durability of TBCs. This study was based on the preparation of SiC whiskers (SiC w) / Y 2 O 3 partially stabilized ZrO 2 (YSZ) integrated composite powder, and the SiC w /YSZ composite TBCs was prepared through the atmospheric plasma spraying (APS) to improve the toughness of the top-coat. The effects of SiC w on the fracture toughness, tribological properties, erosion resistance and bending strength of the coatings were studied. The results showed that the fracture toughness of the composite coating with a SiC w length-to-diameter ratio (L/D ratio) of 250 was 24.6 % higher than the YSZ coating. Moreover, the composite coating presented excellent performance in wear, erosion, and resistance to crack propagation and spallation. The low amplitude of the Weibull modulus m of hardness distribution of the doped coating proved the stability effect of SiC w on the reinforcement and toughening of the coating. • A SiC whiskers/Y 2 O 3 partially stabilized ZrO 2 (YSZ) composite coating was successfully deposited. • The toughening mechanism of SiC whiskers in thermal barrier coatings (TBCs) was revealed. • SiC whiskers can significantly improve the wear resistance and bending strength of TBCs. • Promote the application process of SiC whiskers toughened TBCs under extreme service environments. [ABSTRACT FROM AUTHOR]

[Display omitted] • The HA/CM/MWCNTs has superior hydrophilicity. • The HA/CM/MWCNTs is fabricated onto glassy carbon electrode. • Catalysis of dopamine can be still achieved in the presence of protein. • The electrochemical sensor exhibits superior electrocatalytic activity. • This method presents high stability, selectivity, well-maintained sensitivity. Resisting protein adsorption on electrode surfaces is one of pivotal challenges in the electrochemical analysis of small bioactive molecules. In this work, we constructed a novel electrochemical sensing electrode modified with hydrophilic hyaluronic acid (HA) and curcumin/multi-walled carbon nanotube (CM/MWCNTs). The modified electrodes were comprehensively characterized for dopamine detection including the sensing sensitivity, selectivity and stability. The constructed electrochemical sensor for dopamine detection exhibited remarkable resistance to protein adsorption because of the inherent hydrophilicity of HA, and synergistically, the superior electrochemical behavior of the CM/MWCNTs composite (quinone/hydroquinone redox couples enabled superior electrochemical behavior). The HA/CM/MWCNTs/GCE performed about 5.0 folds, 3.5 folds and 2.4 folds higher electrocatalytic current for dopamine than that revealed at bare GCE, MWCNTs/GCE, and CM/MWCNTs/GCE, respectively. In addition, the HA/CM/MWCNTs-based sensor demonstrated excellent sensing performance with a low detection limit of 0.009 μM (S/N = 3) within the concentration range from 50 to 200 μM. The constructed HA/CM/MWCNTs-modified glassy carbon electrodes offered a reliable platform for the real-time monitoring of dopamine with no protein absorption. [ABSTRACT FROM AUTHOR]

A grain fine surface plastic deformation layer with a thickness of about 108.6 ± 1.5 μm was fabricated on 20Cr2Ni4A steel by supersonic fine particle bombardment (SFPB). The microstructure, wettability, and tribological properties of original and SFPB-treated (including Co-SFPB samples: activated carbon was added to the bombarded powder (Al2O3) followed by SFPB; Precoat + SFPB samples: the activated carbon is precoated on the surface of the original material followed by SFPB) low carbon steel were characterized by optical microscope (OM), scanning electron microscope (SEM), static water contact angle, friction, and wear test. The results show that SFPB can refine the surface microstructure and the grain size is about 21 nm. The surface hardness is as high as 428.1 HV0.2, which is 89.3% higher than the original samples. Compared with the residual stress of the original samples (− 116.7 MPa), the residual stress on the surface of Precoat + SFPB samples (− 333.8 MPa) is significantly increased. The measurement results of static water contact angle illustrate that Precoat + SFPB samples have the best hydrophobicity (133.4°). After the treatment of SFPB, 20Cr2Ni4A steel is worn for a certain time, combined with the comprehensive analysis results of friction coefficient, mass loss, and wear morphology, Precoat + SFPB samples have the best wear resistance, which is due to its high surface hardness, large residual compressive stress, and the alloying layer formed by pre-coating activated carbon under the SFPB. [ABSTRACT FROM AUTHOR]

In this study, graphite/CeO 2 reinforced Co-based coatings were prepared on the surface of HT250 gray cast iron by the plasma cladding technology. The influence of graphite and CeO 2 on microstructure and properties of Co-based coatings were studied in detail. The phase composition and microstructure of coatings were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The micro-hardness, wear resistance and corrosion resistance of coatings were evaluated using micro-hardness tester, friction wear testing machine and electrochemical workstation. The results showed that the addition of graphite was beneficial to enhance micro-hardness and wear resistance of coatings, but there was still shortcoming in improving corrosion resistance. On this basis, CeO 2 was further introduced together with graphite. The microstructure of coatings was found to be more uniform under the synergy of graphite and CeO 2. The micro-hardness increased from 684.5 HV 0.3 (coatings adding graphite alone) to 767.4 HV 0.3 (coatings adding graphite and CeO 2), which was 29.7% and 115.1% higher than that of as-cladded coatings and substrate respectively. More importantly, the corrosion current density of coatings was an order of magnitude lower than that of coatings adding graphite alone. Therefore, adding CeO 2 together with graphite was beneficial to the synergistic improvement of micro-hardness, wear resistance and corrosion resistance of Co-based coatings. • Co-based coatings adding graphite/CeO 2 were prepared by plasma cladding. • The microstructure of coatings became uniform after adding graphite/CeO 2. • Wear resistance of coatings adding graphite together with CeO 2 was enhanced. • Corrosion resistance of coatings adding graphite together with CeO 2 was raised. [ABSTRACT FROM AUTHOR]

We investigate herein that whether the directional array TiN can improve the wear resistance of AlCoCrFeNiTi high-entropy alloy (HEA) coating. The results show that the microstructures of in-situ TiN display a "cross" shape of the directional array, and a coherent interface in TiN (2 0 0)/(Ni, Co)Ti 2 (5 1 1) and the high bonding strength between TiN and BCC improve the wear resistance of HEA coating. [Display omitted] • The directional array TiN is synthesized in high entropy alloy coating. • The coherent interface optimizes the interface stability of TiN/(Ni, Co)Ti 2. • The high bonding strength improves the wear resistance of high entropy alloy coating. Recent studies have shown that ceramic particles reinforced high entropy alloy (HEA) has attracted increased attention due to their excellent strength and wear resistance. In this work, the directional array TiN-reinforced AlCoCrFeNiTi HEA coating was synthesized via magnetic field-assisted laser cladding. Besides, the wear resistance of HEA coating was systematically investigated. The atomic structure, ideal adhesion work (W ad) and electronic structure of the interface between matrix and TiN were calculated by first principles method. The results show that the microstructures of in-situ TiN display a "cross" shape of the directional array, and a coherent interface in TiN (2 0 0)/(Ni, Co)Ti 2 (5 1 1) and the high bonding strength between TiN and BCC improve the wear resistance of HEA coating. [ABSTRACT FROM AUTHOR]

In this work, the YSZ fibers and multi-walled carbon nanotubes (MWCNTs) were respectively employed as the extra additive to make some effect to improve the mechanical and thermal properties of YSZ-La 2 Zr 2 O 7 double-layer (LZ) thermal barrier coatings (TBCs). The porosity, thermal conductivity, bonding strength, fracture toughness and thermal cycling behavior of coatings were tested and discussed. The results showed that the addition of YSZ fibers and MWCNTs could improve the properties of LZ coating. In particular, the LZ coating exhibited lower thermal conductivity than that of YSZ coating with single-layer. Compared with MWCNTs reinforced LZ coating, YSZ fibers reinforced coating showed the lowest thermal conductivity and highest bonding strength value, due to the outstanding reinforcement of fibers. In contrast, the LZ coating containing MWCNTs presented the highest fracture toughness value and the best thermal cycling behavior than those of LZ coating and LZ coating containing YSZ fibers, which were attributed to the lowest porosity existing in LZ coating with MWCNTs, contributing to the remarkable inhibition of crack propagation. Therefore, the addition of YSZ fibers and MWCNTs was expected to be a potential way to improve the mechanical and thermal properties of LZ-TBCs. • Comparison study of adding YSZ fibers or MWCNTs in YSZ-La 2 Zr 2 O 7 TBCs was explored. • Adding YSZ fiber or MWCNTs can increase or decrease porosity of TBCs, respectively. • MWCNTs improved the fracture toughness of coatings better than YSZ fibers. • Coatings adding YSZ fibers present the highest bonding strength. • The MWCNTs-containing coatings possess the best thermal cycling lifetime. [ABSTRACT FROM AUTHOR]

The improvement of wear resistance has a profound effect on the far-ranging application of aluminum alloy. In this study, the Al–Cu-based in-situ reinforced composite coating was successfully manufactured on the AlSi10Mg substrate by laser cladding. The microstructure, microhardness and wear resistance under gradient loading (3 N, 6 N, 9 N, 12 N and 15 N) and thermal conditions (200 °C, 300 °C and 400 °C) of the composite coating were studied. The research results showed that the composite coating exhibited a gradient distributed microstructure due to the different diffusion degrees of Cu and Al atoms. The composite coating was mainly composed of Al 4 Cu 9 , Al 7 Cu 4 Ni and α-Al in the bottom, center and top area, respectively, and Al 2 Cu evenly distributed in each area. The microhardness showed gradient distribution owing to the gradient microstructure. Compared with the AlSi10Mg substrate, the composite coating possessed higher microhardness and better wear resistance contributed by the gradient Al–Cu intermetallic compounds. At room temperature, the main wear mechanisms of the composite coating changed from abrasive wear to adhesive wear with the increase of loading condition. At high temperatures, the main wear mechanisms of the composite coating were adhesive wear and plastic flow. During the wear process, Al–Cu intermetallic compound was the key to improving the wear resistance and stabilizing the friction coefficient. • The Al–Cu-based composite coating with gradient distribution on Al alloy was prepared. • The diffusion properties of Al and Cu elements were briefly analyzed. • The friction property of the coating is improved than the substrate at room and high temperatures. • The increase of Al–Cu intermetallic and the transformation of microstructure make the coating have better properties. [ABSTRACT FROM AUTHOR]

FeCoCrNiCu is a face-centered cubic (FCC) high entropy alloy (HEA) with good dislocation storage capacity, ductility, and toughness. FeCoCrNiAl is a body-centered cubic (BCC) HEA whose phase is hard and brittle with high strength and low toughness. In this study, a FeCoCrNiCu/FeCoCrNiAl composite HEA coating was prepared by laser cladding technology. After preparation, the microstructure and mechanical properties of the composite HEA were evaluated. A new two-phase (FCC + BCC) HEA was generated in situ between FCC and BCC HEA, achieving a good transition from hard to soft. The composite coating has the best wear resistance, the friction coefficient is about 0.3, the wear rate is 4.2 × 10−5 mm3/ N·m, and the wear mechanism is abrasive wear. While maintaining high hardness and good wear resistance, the composite coating has good compression properties. The FeCoCrNiCu cladding layer reduced the energy of the FeCoCrNiAl cladding layer by storing dislocations, which reduced its tendency to crack during compression, thus extending the service life of the coating surface. • FeCoCrNiCu/FeCoCrNiAlCu/FeCoCrNiAl composite high entropy alloy coating was successfully prepared by laser cladding. • In-situ generation of FeCoCrNiAlCu dual-phase high-entropy alloy. • Gradient distribution of coating hardness. • The composite HEA coating achieved an effective strength-toughness balance. [ABSTRACT FROM AUTHOR]

Background & Aims: Intestinal fibrosis is a significant complication of Crohn's disease (CD). Gut microbiota reactive Th17 cells are crucial in the pathogenesis of CD; however, how Th17 cells induce intestinal fibrosis is still not completely understood., Methods: In this study, T-cell transfer model with wild-type (WT) and Areg -/- Th17 cells and dextran sulfate sodium (DSS)-induced chronic colitis model in WT and Areg -/- mice were used. CD4 + T-cell expression of AREG was determined by quantitative reverse-transcriptase polymerase chain reaction and enzyme-linked immunosorbent assay. The effect of AREG on proliferation/migration/collagen expression in human intestinal myofibroblasts was determined. AREG expression was assessed in healthy controls and patients with CD with or without intestinal fibrosis., Results: Although Th1 and Th17 cells induced intestinal inflammation at similar levels when transferred into Tcrβxδ -/- mice, Th17 cells induced more severe intestinal fibrosis. Th17 cells expressed higher levels of AREG than Th1 cells. Areg -/- mice developed less severe intestinal fibrosis compared with WT mice on DSS insults. Transfer of Areg -/- Th17 cells induced less severe fibrosis in Tcrβxδ -/- mice compared with WT Th17 cells. Interleukin (IL)6 and IL21 promoted AREG expression in Th17 cells by activating Stat3. Stat3 inhibitor suppressed Th17-induced intestinal fibrosis. AREG promoted human intestinal myofibroblast proliferation, motility, and collagen I expression, which was mediated by activating mammalian target of rapamycin and MEK. AREG expression was increased in intestinal CD4 + T cells in fibrotic sites compared with nonfibrotic sites from patients with CD., Conclusions: These findings reveal that Th17-derived AREG promotes intestinal fibrotic responses in experimental colitis and human patients with CD. Thereby, AREG might serve as a potential therapeutic target for fibrosis in CD., (Copyright © 2023 AGA Institute. Published by Elsevier Inc. All rights reserved.)

Background: Intestinal immune dysfunction is involved in the onset of Crohn's disease (CD). Dendritic cells (DCs), antigen-presenting cells, play a key role in the maintenance of intestinal immune homeostasis. The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor widely expressed in various immune cells, including DCs. Although AhR plays an important role in immune tolerance, its role in the DCs is unclear. The purpose of this study was to investigate whether the activation of AhR can induce tolerogenic DCs (tolDCs) and the differentiation of regulatory T (Treg) cells, as well as ameliorate experimental colitis., Results: AhR activation in the DCs resulted in a lower expression of surface markers such as CD80, CD83, CD86, and pro-inflammatory cytokine production, and higher anti-inflammatory production (IL-1β, IL-23, and IL-12) compared to the control DCs. The surface dendrites in DCs were significantly reduced following AhR activation by 6-formylindolo [3,2-b]carbazole (FICZ). Such DCs with FICZ-mediated activation of AhR, namely tolDCs, promoted Treg cell differentiation. Adoptive transfer of tolDCs to a TNBS-induced colitis mouse model significantly alleviated the severity of inflammation by improving the colon length and decreasing the disease activity index (DAI) and histopathological score. Moreover, the transferred tolDCs decreased the frequency of Th17 cells and increased the frequency of Treg cells in the spleen and mesenteric lymph nodes (MLNs) in murine colitis models., Conclusions: Activation of AhR in the DCs could induce tolDCs, and the transplantation of tolDCs may help in relieving intestinal inflammation and maintaining the Th17/Treg differentiation balance. Thus, our data suggest that AhR may be a potential therapeutic target for CD., (© 2022. The Author(s).)