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To broaden the process understanding with regard to a tool concept for finishing operations based on soft foams coated with diamonds, the application behaviour with respect to the surface preparation of a ground hardened steel surface is considered. By analysing the surface on the basis of established roughness parameters, the material removal behaviour is investigated in dependence on the process parameters and tool specifications. Furthermore, the influence on the micro roughness superimposed on the roughness profile can be analysed. The recorded process forces serve as a basis for understanding the underlying mechanisms and for interpreting the results. [ABSTRACT FROM AUTHOR]

The application of additive manufactured titanium alloy is extensive in aerospace, biomedical, and various important industrial fields. To meet the precision requirements, post-treatment processes such as micro-milling become imperative for additive manufactured parts. In this work, the forged TC4 material and additive manufactured TC4 materials before and after heat-treatment were used as samples, the machinability of three TC4 materials in micro-milling with PCD micro end mill was assessed and compared. The results indicate that the additive manufactured TC4 material before heat-treatment exhibits the poorest surface quality due to its original microstructure defects, but it obtains the improved surface quality after heat-treatment, which even is better than the forged material. The most serious work hardening degree of 111.2% is exhibited on additive manufactured TC4 material after heat-treatment, under the combined action of large cutting force and pore closure. There is no obvious difference in top burr morphology of three materials, but the forged material displays the largest total average top burr size of 239.8 μm owing to its lower hardness and superior plasticity characteristics. • The machinability of three TC4 materials after micro-milling with PCD micro end mill was compared. • After heat-treatment, the micro-milled surface quality of AM TC4 material was greatly enhanced. • The AM TC4 materials are prone to pore closure and more serious surface hardening under the significant milling forces. • The top burr size of three TC4 materials on the up-milling side is larger than that on the down-milling side. [ABSTRACT FROM AUTHOR]

In this work, geopolymer matrix samples containing different amounts of chitosan, specifically 1, 3, 5 and 10 wt%, were produced to study the effect of a ductile phase within a much more brittle one. The reference geopolymer was produced mixing a commercial metakaolin with sodium silicate solution and sodium hydroxide solution. Geopolymeric slurries were caste into mold and hardened by a thermal treatment at 70 °C and then at ambient temperature for 28 days. Hardened materials, containing different amount of chitosan, were examined by mean of X-ray diffraction, Fourier Transform Infrared Radiation, Scanning Electron Microscope investigation. Microhardness and fracture toughness were measured to study the effects on the samples chemistry and microstructure caused by the introduction of chitosan into the geopolymer. It has been observed that the addition of chitosan lowers materials porosity and microhardness, but slightly improves their fracture toughness. [ABSTRACT FROM AUTHOR]

The tribological behavior of rails and wheels is a topic of great relevance to the railway industry. However, simulating the complex interactions that occur in the wheel-rail contact presents a challenge to researchers. In this context, tests using the twin-disc tribometer have emerged as a promising alternative. In the test, it is common for the disc with the higher speed (driving disc) to be used to simulate the behavior of the wheel, while the disc with the lower speed (driven disc) simulates the rail. Nonetheless, many studies base their discussions on the differences in tribological behavior between the wheel and the rail considering only microstructural aspects and the hardness relationship between the materials of the wheel and the rail. This study evaluated the effect of slip rates of 1 %, 3 %, and 5 %, as well as the residual stresses generated, on the tribological behavior of class C wheel steel. To isolate the effects of microstructure and hardness, the same material was used in the fabrication of both discs employed in the tests. The results showed that although both discs were made of the same material, the driving disc exhibited greater wear than the driven disc. This finding is frequently reported in the literature, mainly due to the microstructural differences between the discs; still, this study, which used the same material for both discs, achieved the same result. This highlights the need for further discussion on the causes of wear on the driving disc, as the wear may not be solely attributed to the microstructural effects of the materials, contrarily to what is widely indicated in the literature. The results of this study demonstrate that the different residual stresses on the discs, along with the contact dynamics, play a significant role influencing the tribological behavior of the materials tested in the twin-disc tribometer. • Residual stresses tended to be more compressive on the driven disc, which led to reducing crack propagation. • Driving disc presented tensile residual stress closer to the surface in the three slips studied. • There was less mass loss on the driven disc for all slips. • In the driving disc, the higher wear induced less surface hardening and more tensile residual stresses below the surface. [ABSTRACT FROM AUTHOR]

The evolution of the surface gradient hardening layer of AISI 304 stainless steel induced by conventional shot peening at room temperature and −160 °C was comparatively investigated in this work. Shot peening was conducted for durations of 10 s, 15 s, 20 s, 25 s, 30 s, and 60 s under both experimental conditions. The changes in microhardness and tensile properties induced by different shot peening conditions were tested and compared. The microstructure in the sub-surface layer was examined by electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The experimental findings revealed that shot peening at room temperature for durations of 10 s and 25 s yielded gradient hardening layers with depths of 150 μm and 175 μm, respectively. However, extending the shot peening duration to 60 s resulted in negligible changes in both microhardness and the depth of the hardening layer. Conversely, at a temperature of −160 °C, the depth of the gradient hardening layer was observed to increase with longer shot peening durations. Shot peening at −160 °C led to a significant enhancement in both microhardness and the depth of the gradient hardening layer when compared to room temperature. The improvement in microhardness is highly dependent on the shot peening duration. The yield strength of the specimens subjected to shot peening at −160 °C increased by 10 MPa compared to those treated at room temperature. This increase in yield strength was primarily due to a higher induction of martensite content through shot peening at −160 °C, which was the main contributor to the elevated microhardness. The transformation to strain-induced martensite was notably facilitated at cryogenic temperatures, which in turn significantly deepened the gradient hardening layer within the steel. [ABSTRACT FROM AUTHOR]

[Display omitted] • N-ion implantation was performed to modify the ZrO 2 -SiO 2 glass ceramics surface. • The surface hardening and phase transformation were initiated by ion irradiation. • The O-Zr-N, N-Si-O and Si-N bonds were formed on the surface. • The glass ceramics show antibacterial properties after implantation. • The glass ceramics show great potential in dental restoration. Periodontal disease caused by bacterial accumulation is a critical issue affecting the longevity of related materials and implants. Enhancing the antibacterial properties of glass ceramics remains a significant challenge. Due to their excellent mechanical properties, ZrO 2 -SiO 2 glass ceramics have shown great potential in dental restoration. Here, to endow ZrO 2 -SiO 2 glass ceramics with antibacterial properties, nitrogen ion implantation was performed to modify their surfaces. The effects of nitrogen fluence on the microstructural, mechanical and antibacterial properties were investigated. The results showed that phase transformation from tetragonal to monoclinic phase occurred after ion implantation. Surface hardening was observed in the sample under the low fluence ion implantation. Partial amorphization and blistering were observed at the highest fluence of 6.0 × 1017 ions/cm2. XPS analysis revealed that the implanted nitrogen ions mainly form O-Zr-N, N-Si-O and Si-N bonds. Staphylococcus aureus testing showed that the antibacterial properties of ZrO 2 -SiO 2 glass ceramics can be enhanced after implantation, which may be attributed to the formation of reactive nitrogen species. The results show that nitrogen implantation can enhance the antibacterial properties of ZrO 2 -SiO 2 glass ceramics without compromising their mechanical properties. [ABSTRACT FROM AUTHOR]

The contradiction between surface strengthening and ductility loss has been a challenge for laser surface treatment of high-carbon steels. In this study, fiber laser with scanning galvanometer (FL) and diode laser with rectangular beam (DL) were respectively used to obtain periodic and homogenized hardened surfaces on a 65Mn steel. The tensile fracture mechanism and wear property were analyzed based on the microstructure distribution. The results indicated that the maximum surface hardness in the condition FL and DL was approximately 1060 HV and 925 HV, respectively. The tensile properties in the condition FL were comparable to that in the condition without laser surface treatment. The tensile elongation rate in the condition FL was at least 6.8 %, whereas it decreased to approximately 1.4 % in the condition DL. The brittle hardened-layer became crack source during tensile deformation, and led to the deterioration of tensile property. Periodic hardening surface composed of hard and soft regions formed a kind of surface heterostructure, which decreased the stress concentration of hardening zone at the later stage of deformation and postponed the microcracks formation. The deterioration of tensile property was effectively avoided through adjusting the periodic arrangement of hard and soft regions. Additionally, the wear tests indicated that, compared with the specimens without laser surface treatment, wear properties were enhanced after laser surface treatment, and the wear mechanism transforms from adhesive wear to abrasive wear. This work provides new insight into improving the wear properties without decreasing the tensile ductility. [ABSTRACT FROM AUTHOR]

Lateral confinement and high temperature affect the load-carrying capacity of a concrete member significantly. In a fire condition, a concrete member exhibits not only mechanical deformation but also thermal deformation. Therefore, accurately modeling the fire behavior of confined structural concrete is challenging. In this paper, a new three-dimensional thermo-plasticity model for concrete is developed, taking both high temperature and confinement into account. A temperature-dependent yield surface and a non-associate flow rule are formulated. The hardening rules for concrete are proposed as a function of confinement and temperature. The load-induced strain of concrete at elevated temperatures is calculated by using a stress-triaxiality factor to consider the confinement effect. The proposed concrete model is implemented in the user-subroutine (UMAT) of Abaqus, in which Runge-Kutta-England scheme with sub-stepping is used to update stress increment. The accuracy of the proposed model is validated by experiments on concrete specimens, circular concrete-filled steel tubular (CFST) columns, double-skin CFST (DCFST) columns, and concrete-filled double steel tubular (CFDST) columns. It is shown that the developed thermo-plasticity model of concrete accurately captures the behavior of confined concrete at ambient and elevated temperatures and can be incorporated in nonlinear procedures for simulating the fire resistance of composite columns exposed to fire. • A new thermo-plasticity model for concrete at elevated temperatures is developed. • The effects of confinement and high temperatures are considered in the model. • The yield surface and hardening rules for concrete exposed to fire are formulated. • The proposed concrete model is implemented in user-subroutine (UMAT) of Abaqus. • The accuracy of the proposed models is validated by comparison with fire test results. [ABSTRACT FROM AUTHOR]

Plasma nitriding is a widely used technique for the surface hardening of metals. Numerous nitriding methods based on glow discharge have been developed over time. In this study, we designed a versatile system capable of performing conventional nitriding, radio-frequency nitriding, active screen plasma nitriding, and radio-frequency active screen overlay nitriding, all within a single piece of equipment. Using M50 steel as the test material, we compared the effects of these nitriding techniques. Our results indicate that both direct current glow discharge plasma nitriding and active screen plasma nitriding produce a compound layer on the M50 surface, characterized by high surface hardness but low compressive stress. In contrast, radio frequency plasma nitriding results in a nitrogen solid solution within α-Fe, producing a uniform surface with high surface hardness and significant residual stress. The overlay nitriding method yields a nitriding layer with moderate thickness and favorable residual stress. Additionally, we analyzed the impact of the potential of the sample on the nitriding layer. For nitriding processes dominated by direct current glow discharge, the cathode potential enhances the nitriding effect by promoting the directional movement of charged particles. However, in processes dominated by radio frequency discharge, the influence of the directional movement of plasma on the nitriding layer properties is substantially reduced. Notably, samples treated at a floating potential produced nitriding layers with excellent overall performance. This study provides valuable insights for optimizing nitriding equipment and selecting appropriate nitriding processes for various applications. • A system capable of performing multiple nitriding methods is designed. • The treatment effects of different nitriding methods were compared horizontally. • The impact of sample potential on the nitriding layer is analyzed. [ABSTRACT FROM AUTHOR]

Gradient nanostructured (GNS) 316L stainless steel manufactured by surface mechanical rolling treatment (SMRT) with a full martensitic phase on the surface exhibits an extraordinary annealed hardening. The surface hardness increases by 44 % from 4.1 GPa of the SMRTed 316L stainless steel up to 5.9 GPa after annealed at 400 °C for 120 min. Surface hardening is primarily attributed to the formation of low angle grain boundaries (LAGBs) within the original nano-grains. LAGBs function as substructures that effectively divide the grains into smaller units. These LAGBs originate from lattice distortions caused by Ni segregation during the annealing process. Furthermore, the redistribution of Ni can be regarded as a nucleation step leading to phase reversion from martensite to austenite. Additionally, the presence of Ni-enriched zones distributed within the martensite matrix serves to hinder dislocation movement, thus contributing to the observed surface hardening. • Surface hardness of SMRTed 316L stainless steel increases from 4.1 GPa to 5.9 GPa after 400 °C/120 min annealing treatment. • Annealing-induced LAGBs, which function as substructures dividing the grain into smaller units, is the main reason for the surface hardening phenomenon. • The formation of LAGBs is intimately linked to the redistribution of Ni and Ni redistribution serves as a nucleation step potentially leading to phase reversion. [ABSTRACT FROM AUTHOR]

Plasticity is a common phenomenon in many materials. Furthermore, it is also commonly applied in multiscale analyses. Plasticity is mainly characterised by the yield function. This function distinguishes between the elastic and the plastic material domain. The transition surface is denoted as the yield surface, and characterises the material behaviour significantly. In the contribution at hand, an algorithm is proposed, which can identify arbitrary yield surfaces. No assumptions regarding the geometry, kinematics, or material model need to be incorporated. The algorithm can identify yield surfaces as long as a function can be formulated, which measures the distance of any point in the principal stress space to the yield surface, and an indicator exists, which characterises the behaviour of the material to be elastic or plastic. Hence, a very general algorithm is achieved, which can also be applied to crystal plasticity. The property of star-convexity of yield surfaces is exploited. This algorithm is also well suited for the application in high performance computing environments. Furthermore, the proposed algorithm can be applied to the identification of initial damage surfaces as well. The proposed algorithm is validated on one macroscopically formulated yield function. Subsequently, it is applied to multiscale frameworks to highlight the benefits of the proposed approach. Furthermore, the capabilities of the algorithm to also identify yield surfaces after hardening are presented. Important properties of such yield surfaces are highlighted. The good scalability within distributed memory systems is shown, and the applicability for anisotropic yield surfaces is demonstrated. • Numerical approach on identifying arbitrary yield surfaces. • Application onto multiscale analyses. • Application onto distributed memory systems. [ABSTRACT FROM AUTHOR]

Infrared radiation is a non-ionizing electromagnetic radiation ranging from 0.78 to 1000 μm and lies between red visible and microwave region. With an advent in atomic age, it has been gaining considerable interest in the food processing industries as it attenuates the disadvantages caused by other thermal processing treatments leading to enhanced yield of milling along with improved functional properties. Infrared radiation is a thermal processing treatment; however, it possesses several benefits over methods of conventional thermal treatment as it has a reduced time of heating, lower rate of quality losses, versatile in nature, low energy requirements, causes uniform heating, reduced surface hardening and equipment is simple and compact. Once infrared radiations come in contact with food particles, they start penetrating the food material further leading to vibration of water molecules that causes the food product to heat up. This article examines the working principles of infrared heating and how it affects cereal grains and flours. The changes that infrared heating causes on structural morphology, functional characteristics, physico-chemical properties and other aspects may help to support the use of exploration as a food processing alternative in the future. [ABSTRACT FROM AUTHOR]

This study investigates the high-temperature wear of additive-manufactured Ti6Al4V alloy against GH2132. The wear mechanism transitioned from abrasive and adhesive wear to oxidative wear with rising temperatures. The microstructure characteristics reveal the special hybrid high-temperature wear mechanisms: shear deformation-induced wear hardening and dynamic recrystallization-induced wear softening. At lower temperatures, the thinner oxide layer was easily removed and the worn surface in contact underwent work hardening, reducing the negative effects of thermal softening. At higher temperatures, the thicker oxide layer slightly reduced adhesive of the substrate but failed due to cracking and spalling. Combined with intensified thermal softening, recrystallization softening on the worn surface not only eliminated surface hardening but led to a sharp decline in wear resistance. [ABSTRACT FROM AUTHOR]

Friction Stir Processing (FSP) was performed to create a composite layer of ZrO 2 + SiO 2 nanoparticles on the surface of the AA5083 alloy plate under different process conditions. The FSP process was carried out by varying the tool traverse speed from 20 to 60 mm/min and a number of tool passes (1 and 2) at a constant tool rotational speed of 1200 rpm. The microstructure of the composite layer was investigated and its mechanical properties, viz, microhardness and wear behaviour were studied and compared with those of the base alloy. Investigation of microstructure revealed ZrO 2 + SiO 2 nanoparticles embedded up to an average depth of 300 μm below the top surface. Grain size refinement and increased homogeneity in reinforcement distribution were the outcomes of multi-pass FSP. A composite layer with consistent hardness was obtained via two-pass FSP. The hardness of the surface nanocomposite was found to be 33 % higher than that of the base alloy. The surface composite showed improved wear resistance. The composite layer exhibited a reduction of 46 % in the coefficient of friction and a 35 % reduction in the specific wear rate compared to the base alloy. The primary reasons for the observed increase in surface hardness and wear resistance are strengthening due to grain refinement, the presence of hard secondary phases and the quick formation of a passive layer at the surface. • FSP successfully produced a ZrO 2 + SiO 2 /AA5083 surface nanocomposite, reinforcing the AA5083 substrate. • During the FSP, the evolution of microstructure is dominated by dynamic recrystallization. • The surface nanocomposite acting as a passive layer improved the hardness resistance of the modified surface. • Fine-grain strengthening and reinforcing particles hardened the modified surface, resulting in improved wear resistance. [ABSTRACT FROM AUTHOR]

The Cryo-lubrication technique was introduced to minimize the environmental impact produced by traditional flood cooling and to promote resource equity in a sustainable manner. The synergetic interaction of cryogenic coolant and minimum quantity lubrication (MQL) produces a hybrid cryo-lubrication effect that significantly reduces the thermal-mechanical damage associated with tool-workpiece interaction. This leads to enhanced machinability and increased dimensional accuracy. To provide more insight into hybrid lubrication effectiveness, this article presents a systematic literature review of cryo-lubrication techniques for machining many difficult-to-cut materials. Two leading databases, Scopus and ScienceDirect, are used to select 82 relevant research articles published during the last six years from 2018 to 2023. The contents incudes, (a) review of cryo-lubrication fundamentals, (b) summary of the characteristics of cryo-lubrication types, (c) in-depth analysis on the effectiveness and challenges of each cryo-lubrication technique in machining processes, and d) suggestions for future perspectives. It is summarized that cryo-lubrication is better than flood, dry, cryogenic, and MQL environments in demonstrating superior heat transfer characteristics, improving chip breakability, reducing cutting force and power consumption, and enhancing surface integrity. However, in some cases, the excessive surface hardening induced by low-temperature coolant may impedes the machining performance and increased the surface roughness, cutting force, and energy consumption, thereby emphasizing potential advancements in this field. [Display omitted] [ABSTRACT FROM AUTHOR]

• Metal shot peened nickel-base superalloy single crystals have been analysed through the analysis of local misorientations. • A methodology of establishing reliable estimates of the depth of cold work and its magnitude in these single crystals is described. • This methodology is shown to be robust to changes in acquisition parameters within the scanning electron microscope and to changes in post-acquisition analysis parameters. • The principles and processes underlying this methodology can be readily adapted for the analysis of datasets of electron backscattered diffraction images from other surface hardening techniques and other surface-hardened materials. The amount of cold work induced by a surface hardening technique and the depth to which it is produced within a metallic material are both important parameters within the field of surface engineering. In this paper a methodology of establishing reliable estimates of the depth and magnitude of cold work in surface hardened nickel-based superalloy single crystals from a dataset (map) of electron backscattered diffraction images through the analysis of local misorientations is described in detail. The impact of varying a number of acquisition parameters within the scanning electron microscope and the impact of the various post-acquisition analysis parameters on the outcome of the analysis are both described and discussed in detail. The Python script used to perform this analysis is published in full. The principles and processes underlying this methodology, as well as the published script, can be readily adapted for the analysis of datasets of electron backscattered diffraction images from other surface hardening techniques and other surface-hardened materials. [ABSTRACT FROM AUTHOR]

• Under air atmosphere, furfuryl alcohol resins can be oxidized above 175 °C. • This oxidation process results in the formation of carbonyls and benzenic moieties. • This surface oxidation has a thickness of about 20 µm. • This surface oxidation offers protection against thermal degradation. This article emphasizes the phenomena occurring in furan resins at high temperature, once they are polymerized and before their carbonization. The effects of the atmosphere (N 2 and air) during the curing of furan resins were investigated and it is shown that upon exposure to air at temperatures above 175 °C, the furan resins develop an aromatic surface. By means of solid-state NMR and infrared spectroscopy, it is demonstrated that the aromatic groups are mainly located on the material's surface. A mechanism of this surface modification is proposed together with a short kinetic study. In addition, the thermo-mechanical properties are studied. The aromatic surfaces decrease the damping capacity of the material, yet its resistance to degradation is increased. Finally, tensile properties of the furan resins are not affected by the presence of this aromatic surface. [ABSTRACT FROM AUTHOR]

The interfacial bonding strength of Ti/steel clad plates is a crucial factor that affects their application. However, the effect of the surface state, which is a significant determinant, is often neglected. In this study, various surface treatment processes were employed to create different surface states based on the hot-rolling of double-layer steel billets, and the effects and mechanisms of these surface states on the bonding performance of hot-rolled Ti/steel clad plates were systematically examined. The results showed that the Ti/steel clad plates pretreated with a louver wheel exhibited the highest bonding performance, with the average bonding strength peaking at 328.67 MPa and stabilising at approximately 300 MPa. This strength was approximately 50 % greater than that achieved with wire brush treatment and significantly surpassed the results obtained with sanding belts and diamond grinding discs. The analysis of the surface properties and microstructural characteristics revealed that various surface treatments led to different levels of work hardening and lattice distortion at the surface, and the interface bonding strength depended on the degree of matching between these factors. Proper surface hardening can promote the transformation of lattice distortion energy into a diffusion-driving force of elements on both sides of the interface during rolling, enabling sufficient diffusion of elements on both sides of the interface and obtaining good interface bonding performance. A phenomenological prediction mechanism-based model was established to quantify the relationship between the surface state and the bonding strength. This study elucidats the mechanism by which the surface state of materials influences the interfacial bonding performance of hot-rolled Ti/steel clad plates. These findings have significant implications for enhancing the interfacial properties of these composite plates and for selecting suitable pre-rolling surface treatment processes. [Display omitted] • This work studied the effect of surface states during the rolling compounding process. • The appropriate surface pretreatment process for rolling Ti-steel clad plates was identified and verified. • Surface pretreatment led to surface hardening and the accumulation of lattice distortions. • The interfacial bonding mechanism of hot-rolled Ti-steel clad plates based on surface states was elucidated. • A lattice distortion energy-hardening-diffusion based phenomenological model was proposed. [ABSTRACT FROM AUTHOR]

Polydimethylsiloxane (PDMS) is a soft, biocompatible polymer extensively employed in biomedical research, notable for its tunable mechanical properties achieved through cross-linking. While many studies have assessed the mechanical properties of PDMS utilizing macroscopic and microscopic methods, these analyses are often limited to freshly prepared samples. However, the mechanical properties of PDMS can be expected to change during prolonged exposure to water or air, such as interface polymer chain loosening or surface hardening, which are critical considerations in applications like cell culture platforms or microfluidic devices. This paper presents a comprehensive 10-day investigation of the evolution of PDMS surface mechanical properties through AFM-based nano-indentation. We focused on the most commonly utilized crosslinker-to-base ratios of PDMS, 1:10 (r10) and 1:20 (r20), under conditions of air and deionized water storage. For r10 samples, a hardening process was detected, peaking at 2.12 ± 0.35 MPa within five days for those stored in air and 1.71 ± 0.16 MPa by the third day for those immersed in water. During indentation, the samples displayed multiple contact points, suggesting the formation of distinct regions with varying mechanical properties. In contrast, r20 samples exhibited better stability, with an observed elastic modulus averaging 0.62 ± 0.06 MPa for air-stored and 0.74 ± 0.06 MPa for water-stored samples. Relaxation experiments, interpreted via the General Maxwell Model featuring two distinct component responses, a relatively consistent fast response τ 1 (on the order of 10−1 s), and a more variable, slower response τ 2 (on the order of 10 s), throughout the study period. The identification of two distinct relaxation times suggests the involvement of two disparate material property regimes in the relaxation process, implying changes in the surface material composition at the interface with air/water. These variations in mechanical properties could significantly influence the long-term functionality of PDMS in various biomedical applications. [ABSTRACT FROM AUTHOR]

Surface treatment techniques, like laser peening, enhance the longevity of Ni-based superalloy components by reinforcing their microstructure against surface-initiated damage. Recent findings suggest that these methods may also influence precipitate coarsening behavior at high temperatures, leading to rafting phenomena. This study extensively examined γ' rafting in single crystal Ni-based superalloy CMSX-4 post laser peening and heat treatment. X-ray diffraction revealed surface compressive stresses (-400 MPa to -800 MPa), transitioning to tensile stresses at greater depths before returning to an unstressed state. Correlation with electron microscopy indicated horizontal coarsening in compressive regions and vertical coarsening in tensile regions due to misfit and residual stresses aiding diffusion. Plastic strain near the LPed surface was measurably increased with lattice misorientation values around 5° before returning to an unstrained state after heat treatment due to rafting-aided recovery and defect reorganization. Secondary γ' precipitates with a radius of approximately 10 nm occupied γ channels between rafted precipitates, indicating solute element diffusion and supersaturation. Energy dispersive x-ray spectroscopy showed a significant depletion of γ'-forming elements around rafted primary precipitates, highlighting preferential solute diffusion. [Display omitted] • Dislocations and residual stresses significantly altered γ' coarsening behavior. • Coarsening driven by diffusion of solutes through the vertical matrix channels. • Rafting directionality was influenced by residual stress orientation. • Recrystallization not observed following laser peening and heat treatment. [ABSTRACT FROM AUTHOR]

• Development of ruiniform relief structure-controlled and dissolution-facilitated. • Depressions upon the plateau surface as sinks, below which speleogenesis proceeds. • Dissolution of cement as a facilitating factor of ruiniform relief development. • Elements leaching enhanced by acidic solutions and soil microorganisms. Despite recent major advances, complex factors contributing to the development of sandstone ruiniform relief still require recognition, particularly with respect to environmental controls and the character of the weathering processes responsible for the formation of corridors. The discovery of a small cave and roofed slots in one of ruiniform terrains in the Stołowe Mountains tableland, SW Poland – with active weathering and erosional processes – allowed us to tackle the problem. Our study confirmed earlier claims that the formation of corridors might lead through the speleogenesis. We showed that the process is geologically- and environmentally-controlled and is facilitated by cement dissolution. Thick sandstone beds of subhorizontal alignment, well-developed vertical jointing, high porosity and coarse grain size account for preferential groundwater drainage and the susceptibility to erosional removal of mass. The dominance of quartz and kaolinite in mineral composition, together with the present-day temperate climate and the dense vegetation cover, result in the development of permeable and very acidic soils upon the plateau surface. Such soils support efficient rainwater percolation, produce acidic solutions and create room for fungi dominance among soil microorganisms. The development of corridors of ruiniform relief is associated with structure-controlled topographic lows upon the plateau surface, which act as sinks. There, the throughput of acidic solutions, enriched with microorganisms, is the highest and over prolonged period of time causes dissolution of clay and quartz cement. Since its content is small, the dissolution results in the reduction of rock cohesion and the susceptibility to grain-by-grain detachment. Yet, dissolution is only a facilitator, with various mechanical processes (frost weathering, wetting-weakening, dilation) earlier recognized taking part in sandstone deterioration and upward propagation of voids, until the emergence of an unroofed corridor. The remaining bedrock compartments – hardened by protective surface crust – are also subject to dissolution, but at slower pace. [ABSTRACT FROM AUTHOR]

The components manufactured by Wire and Arc Additive Manufacturing (WAAM) have some problems to be solved urgently, such as uneven microstructure, numerous pore defects, and residual tensile stress. Laser Shock Peening (LSP) is an innovative and advanced surface modification technology that improves mechanical characteristics by inducing significant plastic deformation and high compressive residual stress on metal surfaces. Therefore, combining LSP with WAAM is expected to solve its existing problems. In this work, LSP with different energy parameters was used to post-process the WAAM 2319 aluminum alloy. The results indicated that LSP could improve the microstructure, eliminate near-surface pores, harden the surface layer, and induce a residual compressive stress layer, and the effect was more effective with the increase of laser energy applied. The yield strength of the peened specimens significantly increased by 60.73 %, and the ultimate tensile strength also increased by 16.03 %. The hole fatigue life of the peened specimens was significantly improved, increasing by 179.8 % and 261.7 %, respectively, applying laser energies of 5 J and 10 J. Therefore, the engineering industry may benefit from a combination of LSP and WAAM technology. • LSP is an effective post-treatment method for wire and arc additive manufacturing. • LSP treatment could remarkably eliminate the near-surface pores. • LSP could harden the surface and induce the deeper residual compressive stress layer. • Yield strength and hole fatigue life are significantly increased by 60.73% and 261.7%, respectively. [ABSTRACT FROM AUTHOR]

In general, the outermost region of a metallic material has the highest hardness after surface mechanical strengthening. However, an abnormal surface hardening behavior was observed in Ti6Al4V alloy after the ultrasonic surface rolling process (USRP) in this work. The region with the highest surface hardening was not at the top surface but at the subsurface. By analyzing the distribution of grain size, dislocation density, texture, and kernel average misorientation (KAM) at different depths from the surface, and combining these findings with finite element analysis (FEA), the microstructural evolution underlying this abnormal surface hardening was elucidated. The microstructural characterization and FEA results indicate that the subsurface region underwent the most significant deformation. Subsequently, through the application of theoretical analysis, the potential mechanism of abnormal hardening of USRP treatment is described quantitatively for the first time. The results demonstrated that the hardening effect resulting from grain refinement was less pronounced, whereas the hardening effect resulting from dislocation pile-up was more prevalent. At the subsurface region of the USRP sample, a large number of interfaces resulted in the highest accumulation of dislocations in this area. Consequently, the subsurface region exhibited the highest microhardness, leading to the abnormal surface hardening phenomenon. • The USRP treated Ti6Al4V alloy exhibits excellent surface integrity. • The USRP treated Ti6Al4V alloy shows abnormal surface hardening behavior. • The maximum plastic deformation at the subsurface area causes abnormal hardening. • The accumulation of dislocations provides the main surface hardening effect. [ABSTRACT FROM AUTHOR]

3D printing has demonstrated manufacturing and economic advantages in terms of customization, flexibility and rapid prototyping of precision complex geometric components. The 17-4PH precipitate hardening steel is notable for its excellent corrosion resistance. This study aims on enhancing the wear resistance of SLM-printed 17-4PH components through interstitial surface hardening. To eliminate microstructural defects introduced by the SLM process, the components were first subjected to solution heat treatment. Following this, a low-temperature nitrocarburizing (LTNC) process was applied at temperatures below 400 °C, resulting in the formation of an interstitial surface layer with an average thickness of approximately 17 μm. Optical microscopy and XRD analyses confirmed the presence of a dual-phase structure composed of expanded BCC and FCC phases within the hardened layer, with no detectable nitride/carbide precipitates. Quantitatively, the LTNC process significantly enhanced the surface microhardness of the components, increasing it to a minimum of 1000 HV0.2. The bulk microhardness also increased from 360 HV0.2 to 480 HV0.2, indicating an aging effect during the diffusion treatment. In terms of performance, LTNC substantially improved the wear resistance of the components. However, a slight reduction in corrosion resistance was observed, attributed to increased surface roughness and the presence of the dual-phase expanded structure. [Display omitted] • An interstitially hardened layer free of nitride/carbide was obtained. • An interstitially hardened layer with expanded FCC/BCC lattice was formed. • Microhardness and wear resistance significantly improved after LTNC. • Slight decrease in corrosion resistance was observed after LTNC. [ABSTRACT FROM AUTHOR]

The IN718 superalloy has become a strategic alloy for applications in critical components in aerospace, oil, and gas, or power generation. Commercially, IN718 is produced by conventional casting processes. However, manufacturing is evolving towards 3D printing, which allows the manufacturing of near-net-shape parts and complex designs, thus optimizing manufacturing steps, reducing production costs, and adding other advantages to the final product. However, high corrosion resistance and mechanical strength are required in applications such as oil and gas, whereas IN718 superalloys have limitations. Surface hardening by applying plasma nitriding can protect against corrosion by increasing mechanical strength and wear resistance. For this, plasma nitriding has been widely applied for surface hardening of IN718; however, little is found on the effects of surface treatments (coating or nitriding) of additively manufactured alloys. The effects of temperature during plasma nitriding on the surface properties of IN718 superalloy 3D printed by the Laser Beam Powder Bed Fusion (LB-PBF) method are reported here. Samples of IN718 fabricated by 3D printing were plasma nitrided at fixed temperatures between 500 and 650 °C in a semi-industrial reactor, their effects are analyzed and correlated with their microstructural characteristics, the mechanical properties at the micro- and nanoscale, and the tribological responses in a pin-on-disk configuration. [Display omitted] • PN at 500 °C produced the γ N coexisting with c-CrN and the fine crystalline γ-(Ni,Cr,Fe) phases. • PN between 550& 650 °C produced the γ Cr-depleted and the c-CrN hardening phases. • HV increases with PN at 500 °C to 575 °C, and neglectable changes in nano-hardness & E are detected. • The elastoplastic behavior of the IN718 PN at 500 °C was better than the nitriding at 650 °C. • Wear resistance of the 3D-printed IN718 is strongly improved upon plasma nitriding at 500 °C. [ABSTRACT FROM AUTHOR]

High modulus steels are promising materials for future lightweight design solutions, as their embedded boride particles in a ductile steel matrix increase the stiffness/density ratio. One key requirement for maturing them towards industrial application is their suitability for improving the surface hardness. In this study we investigated the effects of low-pressure carburizing and plasma nitriding on the microstructure and mechanical properties of selected Fe-TiB 2 - and Fe-Cr-M 2 B-based high modulus steels. Nitriding resulted with the formation of expanded ferrite in the strongest hardness increase to about 1100 HV0.05 from the alloy system's base hardness of 240 and 500 HV0.05, respectively, albeit with different hardness depth profiles. The Fe-Ti-B alloy indicated deformation phenomena in the ferritic matrix after nitriding, whereas nitriding of Fe-Cr-B-C resulted in a diffusion-controlled particle transformation of M 2 B borides into CrN nitrides of lower stiffness. Carburizing on the other hand led to a slightly lower maximum hardness value of about 800 HV0.05 over an increased depth for Fe-Cr-B, as martensite and additional M 23 C 6 carbides were formed in the surface zone. The surface hardness of the Fe-TiB 2 -based alloy could not be increased by the deployed carburization parameters, most likely due to excessive Ti dissolved in the matrix. Consequences for the transfer to engineering applications as well as the refinement of both, thermochemical processing parameters and designated alloy concepts, of high modulus steels are outlined and discussed. • Surface hardening of high modulus steels for ultra-high performance lightweight design • Maximum surface hardness reached about 1100 HV via plasma nitriding. • Carburizing of Fe-TiB 2 -based high modulus steel showed limited effect on hardness. • Nitriding of Fe-Cr-B-based high modulus steel yielded in M 2 B particle transformation. • Discussion of application potentials and alloy design perspectives [ABSTRACT FROM AUTHOR]

Femtosecond laser shock peening (FsLSP) is performed on engineering alloys to improve their wear resistance in dry and oil-lubricated sliding conditions. In this study, the influence of FsLSP on the fretting wear behavior of Ti6Al4V alloy is studied. For this purpose, FsLSP treatment, with laser energies of 50, 100, 150, and 200 μJ, is performed on a Ti6Al4V sample which mainly consists of α-phase. Topographical investigations using white light interferometry reveal that with increase in the laser energy, the coverage area of laser-induced periodic surface structures (LIPSSs) decreases, and the extent of surface pitting damage increases, leading to higher surface roughness. While surface hardness also initially increases with increasing laser energy, it remains invariant when the energy is increased beyond 150 μJ. Sub-surface microstructural investigations and kernel average misorientation maps obtained from electron backscatter diffraction reveal that FsLSP treatment leads to the formation of severely deformed and mildly deformed layers along the depth of the alloy surface. Surface hardening due to FsLSP is attributed to the activation of prismatic , basal slip systems, and 1 0 1 ¯ 2 , 1 1 2 ¯ 3 tensile twins in the severely deformed zone along with grain refinement, which is an outcome of dynamic recrystallization. Fretting wear tests indicate that the coefficient of friction (CoF) of FsLSP treated alloys is consistently lesser than that of its as-received counterpart, whose CoF is 0.38. In contrast, the wear resistance, quantified by the wear rate, wear volume and wear depth, is highest in the sample treated with laser energy of 100 μJ but lower for the as-received as well as 150 and 200 μJ laser treated samples. These results are explained on the basis of the differences in the contact area, formation of surface hardening layer and the size and integrity of asperities on the surface, which in turn influences the dominant fretting wear mechanism. • Effects of femtosecond laser energies on fretting wear is investigated on Ti6Al4V. • Increasing laser energy up to 150 μJ, but not beyond it, enhances surface hardness. • Fretting resistance is highest in the Ti6Al4V treated with laser energy of 100 μJ. • During FsLSP treatment, nanocavities underneath the sub-surface oxide layer form. • The oxide layers break up during fretting and cause abrasive wear. [ABSTRACT FROM AUTHOR]

In this study, turbine dovetail tenon specimens made of iron-based superalloy were composite treated by shot peening and CuNiIn coating, and the fretting fatigue performance at room temperature and 500 °C high temperature was investigated. The surface integrity of the composite-treated dovetail specimens and the wear, fracture morphology, and microstructure after the fretting fatigue tests were characterized. The results showed that the composite treatment of shot peening and CuNiIn coating made the surface roughness of iron-based superalloy from 0.405 μm to 11.279 μm, 46 % reduction in surface hardness and the residual compressive stress layer of about 100 μm was introduced. Compared with the as-received (AS) specimens, the fretting fatigue lifetime of shot peening and CuNiIn coating composite treatment (SC) specimens was increased by 437 % at room temperature, and the fretting fatigue lifetime of SC specimens at high temperature was reduced by 54 % compared with that at room temperature. The cracks in SC specimens were still initiated by multiple fatigue sources, but the number of crack sources decreased and the position of crack sources moved down. At room temperature, CuNiIn coating first underwent shear grinding and then entered delamination wear, while at high temperature, the presence of a large number of coating oxides would lead to serious abrasive wear of CuNiIn coating. Fretting fatigue resulted in obvious orientation differences in the contact region, and the formation and propagation of cracks were related to the plastic deformation and dislocation accumulation of the contact region. The good plasticity of CuNiIn coating is an important reason why it can improve the fretting fatigue performance. The surface hardening caused by shot peening and the introduction of residual compressive stress layer can effectively inhibit crack initiation and propagation. The composite treatment of shot peening and CuNiIn coating can effectively improve the fretting fatigue performance of the dovetail structure of superalloy. • The dovetail tenon treated by shot peening and CuNiIn coating were designed for fretting fatigue test. • The difference in wear mechanism of CuNiIn coatings at room temperature and 500 °C was analyzed. • It was found that fretting fatigue test can cause orientation differences in the contact region. • Summarized the protection mechanism of composite treatment at room temperature and 500 °C. [ABSTRACT FROM AUTHOR]

This study focuses on investigating the precipitation behavior of the expanded austenite during low-temperature salt bath nitrocarburizing by adjusting the treatment temperature and time. The results indicate that the nitrocarburizing layer consists of a N-rich expanded austenite layer near the surface, and a C-rich expanded austenite layer closer to the substrate. Notably, all precipitates occur within the N-rich expanded austenite. When the temperature exceeds 430 °C, Cr 3 C 2 and M 2-3 N emerge in the near-surface region. Furthermore, at 470 °C, with the prolongation of time, the M 2-3 N near the surface gradually decreases and even disappears, as the increase in carbon content within the N-rich expanded austenite enhances its stability. Specifically, at 430 °C, due to the high chemical potential of carbon and the nitrogen-induced lattice expansion, M 5 C 2 forms near the interface between the N-rich layer and the C-rich layer. However, when the temperature rises to 470 °C, a significant amount of thermodynamically more stable M 7 C 3 and M 23 C 6 precipitates with the assistance of chromium diffusion. These findings may provide new insights for the process design and performance optimization of nitrocarburizing. • The precipitation of the nitrocarburizing layer strongly depends on temperature. • At 430 °C, Fe 5 C 2 was detected near the middle section of nitrocarburizing layer. • At 470 °C, M 7 C 3 and M 23 C 6 formed near the middle section of nitrocarburizing layer. • At 470 °C, the M 2-3 N near the surface gradually decreases with the treatment time. [ABSTRACT FROM AUTHOR]

The effect of age hardening treatment on microstructure, tensile properties, and corrosion behavior of additively manufactured A20X alloy was investigated. Three single-step aging temperatures (150 °C, 175 °C, and 200 °C) and one double-step aging temperature (pre-aging at 165 °C followed by aging at 185 °C) along with varying heat treatment durations ranging from 30 min to 144 h, were studied systematically. Microstructural characterizations revealed that the co-existence of coherent/semi-coherent (Ω, θ ′) and incoherent precipitates (θ) resulted in the maximum hardening effect (up to 30 % higher microhardness). This improved the yield strength at room and 150 °C by 33.4 % and 22.6 %, respectively. Double aging delivered the best combination of microstructure with fine grains and optimal precipitate assembly in a short duration (12–16 h). The heat-treated LPBF A20X showed higher ductility and similar mechanical properties compared to the cast A20X. However, optimal precipitate characteristics reduced the corrosion potential by 13–16 % due to a higher galvanic reaction. The highest corrosion potential (−0.622 V) was achieved in the solutionized state. [ABSTRACT FROM AUTHOR]

Surface and subsurface gradient microstructures play a significant role in mechanical properties. To obtain gradient microstructures, a surface strengthening method, namely diamond rotary rolling treatment (DRRT), was proposed in this study. Varied gradient microstructures in 316 L stainless steel were obtained through different DRRT processing parameters. The micro-hardness distribution along the gradient microstructure was tested. The resulting gradient micro/nanostructures in terms of grain size, dislocation density and phase transformation were characterized and evaluated with electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and X-ray diffraction (XRD) analyses. The corresponding mechanical properties were investigated by slow strain rate test. The results showed that the DRRT could introduce a gradient hardening layer on the surface, accompanied by a gradient distribution of nano-grains, ultrafine grains, fine grains and coarse grains extending from the surface to the material interior. Besides, the gradient microstructure was associated with martensitic phase transformation, slip and dislocation. Compared to milled and untreated specimens, the DRRT-treated specimens exhibited a significant increase in yield strength and reduced ductility. Particularly, a well-designed DRRT process can enhance the yield limit while preserving higher ductility. Additionally, a quantitative relationship between the overall yield strength and the hardness distribution of the gradient microstructure was established. • Diamond rotary rolling treatment (DRRT) is proposed to obtain gradient microstructures. • Gradient micro-nano structures are characterized. • Appropriate DRRT process can enhance the yield limit while preserving ductility. [ABSTRACT FROM AUTHOR]

[Display omitted] • PEI surface curing and hardening by plasma etching, forming micro-texture. • Improvement of the PEI wettability benefits for the nucleation of the growing film. • The CrN-PEI adhesion enhanced due to surface hardening and high wettability. • The wear rate of the CrN on etched PEI is the lowest of 9.83 × 10-5 mm3·N−1·m−1. The adhesion enhancement between a hard CrN coating and soft polyetherimide (PEI) is a key factor to effectively increase the usability of the CrN coated PEI as a wear resistant surface. Ion etching by a high pulsed power supply resulted in the surface hardening and hydrophilicity increasing of the PEI owing to the curing effect, which leaded to the weak atom's vibration, proved by the absence of PEI's characteristic infrared peaks, and the presence of the new polar adsorption infrared peaks. The CrN-PEI adhesion was enhanced, the wear resistance of the CrN coated PEI improved to the wear rate as low as 9.83 × 10-5 mm3·N−1·m−1. [ABSTRACT FROM AUTHOR]

Surface discrete hardening by laminar plasma (HLP) enhances rail wear resistance by rapidly quenching surfaces to form discrete martensitic zones. In comparative field tests on a North China freight railway, HLP-treated U75V rails supported twice the total passing weight before reaching wear limits, compared to untreated rails. However, HLP treatment increases susceptibility to rolling contact fatigue (RCF) cracks, including interface cracks from mechanical differences, impact cracks from wheel-rail contact, deformation cracks from cumulative deformation, and matrix cracks extending from interfaces. The ratchet effect and seesaw mechanism, due to plastic deformation accumulation and quenching area warping, are crucial for crack initiation and propagation. This research advances understanding of HLP-treated rails' tribological behavior, emphasizing the necessity for customized maintenance strategies. • The HLP-treated rail demonstrates superior wear resistance in railway testing. • Different types of cracks including interface cracks, matrix cracks, impact cracks and deformation cracks are studied. • The seesaw mechanism and ratchet effect exacerbate the HLP-treated rail's damage process. • The spalling process of the HLP-treated rail is categorized into five stages, and a related model has been developed. [ABSTRACT FROM AUTHOR]

The effect of pulsed electron beam treatment on the structural phase state and strength properties of the AA6111-T4 aluminum alloy was studied. The irradiation led to the formation of a surface layer with a modified structural phase state. The results showed that an oversaturated aluminum-based solid solution is the main phase of the modified layer. Intermetallic phases which were found in the initial state of the alloy, weren't detected in the modified layer using X-ray diffraction methods. The surface layer is characterized by the high-speed cellular crystallization structure with dimensions of 0.7 μm. The microhardness of the irradiated layer increased by more than 30%. Surface hardening parameters and mechanisms were clarified by investigation of the microstructural modification and the phase transformation both pre and post irradiation. It was shown that the grain boundary and solid solution hardening mechanisms play the key role in increasing the microhardness of the irradiated layer. [ABSTRACT FROM AUTHOR]

Strain-hardening, thermal-softening as well as grain refinement may lead to unexpected changes in surface hardness of turned steel parts. Although the relationship between hardness, microstructure and cutting parameters has been investigated in previous research works, the prediction of surface hardness remains still a challenge. In this work, orthogonal turning tests were performed using low carbon steel AISI 4140 and thermomechanical loads, surface hardness and microstructure were measured. The relationship between surface hardness and thermomechanical loads was explored by establishing an empirical model. Moreover, grain size evolution was observed and correlated with micro hardness. Results suggest that cutting conditions can be controlled to achieve desired surface hardness by evaluating functions dependent on in-process measurements. [ABSTRACT FROM AUTHOR]

The grind-hardening process aims to increase the surface hardness of the material through the dual action of the mechanical and thermal load. A novel approach to model the process and predict the hardness penetration depth was developed based exclusively on the prediction of austenite-martensite transformation. A combined micro and macro scale approach was implemented to forecast the temperature reached in the surface starting from the action of a single grain and using its specific cutting power to design a moving heat source representing the interaction between the grinding wheel and the material. The martensitic transformation temperature considered in this paper takes into consideration the fast heat cycle typical of this process. In order to validate the model, tangential surface grinding tests were performed on 42CrMo4 and microstructural analysis with micro-hardness measurements were performed. This research presents a first step in developing a grinding process simulation that includes multi-grain grinding, real grain geometries, binder effect, and real workpiece-grinding wheel kinematics. [ABSTRACT FROM AUTHOR]

Pulsed laser-based micro-texturing induces topographical and chemical modifications on surfaces that yield beneficial properties such as anti-microbial effect, micro-hydrodynamic bearing, and surface hardening. These properties find a multitude of applications in surface treatment and tribology. However, laser texturing of free form surfaces is a cost and effort-intensive process, specifically medical implants or ergonomically designed tools/devices. Such components often require numerically controlled 3 or 5 axes machines and sophisticated computer-aided manufacturing (CAM) software for precise tool movement. In this manuscript, the authors have designed, fabricated, and validated a jerk-free, cost-effective Stewart platform that works in tandem with an existing laser machining setup. A microcontroller and stepper motor based linear actuators were used to orient and translate the six degrees-of-freedom (DoF) platform. A customized computer program helped maneuver the workpieces (medical implants) for the micro texturing of the 3D surface profiles. As laser irradiation demands a time-invariant focal length for effective ablation, the platform maintains the focal length from the galvo-scanner of the laser machine to the workpiece while maneuvering the workpiece throughout the texture trajectory. To estimate the smoothness of the platform during motion, vibrational parameters were also measured and analyzed. Such cost-effective platforms may find applications in free form texturing in non-contact mode of machining as well as in metrology. Texturing was performed successfully on implants freeform surface with an average diameter of ~35–40 μm and depth of ~15–20 μm. [Display omitted] • A cost-effective Stewart platform was designed for freeform texturing of implant. • Jerk-free 3D maneuvering with ±25 μm tolerance was achieved by customized program. • The platform works in tandem with an existing laser machining setup. • 6 degrees-of-freedom was achieved using a microcontroller and linear actuators. • Electrochemical studies showed improved corrosion resistance post texturing. [ABSTRACT FROM AUTHOR]

Methane/nitrogen (CH 4 /N 2) separation remains a persistent challenge owing to the similar polarities, kinetic diameters, and boiling points of CH 4 and N 2. Herein, a novel method is proposed for enhancing the separation performance of CH 4 /N 2 via vacuum resistance calcination, which uses surface-carbonized and hardened ZIF-8 (SCH-Z), MOF-74-Ni (SCH-M), and UiO-66-NH 2 (SCH–U). The nanoparticles treated by vacuum resistance calcination remain the microporous characteristics of MOF, while introducing additional mesoporous structure and unsaturated metal sites. Such multistage pore structure and rich metal sites display a significant improvement in the CH 4 adsorption over N 2. In addition, the separation performance of multiple metal–organic frameworks (MOFs) mixed matrix membranes (MMMs) fabricated by homogeneously mixing the alkaline polymer polyvinylamine (PVAm) with SCH-M/SCH-Z and SCH-M/SCH–U was investigated, respectively. When the measured pressure was 0.1 MPa and the binary filler loading was 48 %, the PVAm/(SCH-M) 0.7 (SCH-Z) 0.3 /MPSf MMM exhibited outstanding CH 4 /N 2 separation performance (CH 4 permeance of 2888.48 GPU and selectivity of 4.38). Furthermore, when the loading of the binary filler was 45 %, the ideal CH 4 /N 2 selectivity and CH 4 permeance of PVAm/(SCH-M) 0.67 (SCH–U) 0.33 /MPSf MMM are 5.57 and 2263.94 GPU, respectively. This study provides a novel idea that introducing multi-MOF nanoparticles into MMMs for optimizing gas separation performance. [Display omitted] • Vacuum-resistance calcination treated SCH by surface carbonization and harden was used as binary filler of MMMs. • SCH with multistage pore structure and rich metal sites exhibited good membrane-forming property and adsorption capacity for CH 4. • The multi-MOF MMMs showed good CH 4 permeance and outstanding CH 4 /N 2 selectivity. [ABSTRACT FROM AUTHOR]

Inconel 718 coatings deposited by laser-cladding (LC) on low-alloy steel substrate have been grinded followed by robotic hammer peening (RHP). White layer consisted of nanograins, smaller than 100 nm, has been observed on the surface accompanied with a deformation layer underneath after grinding and RHP. By increasing the RHP intensity (i.e., both the impact energy and the dent overlap), the residual tensile stress measured by X-ray diffraction from the surface of the coating has been monotonically reduced and eventually converted to residual compressive stress with increased in-plane anisotropy, which was accompanied with monotonically increased surface hardening up to 40.5 HRC. Grain deformations have been induced in the white- and deformation-layer, they are dominated by twinning and slipping, respectively. In terms of depth-dependent distributions of low-angle (<15°) grain boundaries and hardening, the effective cold-working thickness induced by the RHP process is over 1000 μm, which is close to the thickness of a single-pass LC deposition. Onset of porosity closures occurred upon the RHP process, especially in the near-surface regions. These findings shed light on integrity enhancement for additive manufacturing of metal alloys by LC-based techniques through introducing interpass RHP process. • Laser-cladding of Inconel 718 on low-alloy steel followed by grinding and RHP • Laves phase seen in build direction due to columnar growth and Nb-/Mo-segregation • Grinding-induced a white layer of nanograins with a deformed layer underneath • RHP-induced deformations are dominated by twining and crystallographic shear. • Inter-pass RHP can be made in laser-cladding thanks to its larger effective depth. [ABSTRACT FROM AUTHOR]

The interrupted discrete waterjet (DWJ) offers advantages in surface treatment due to its exceptional load characteristics and high controllability. However, the surface characteristics of materials under controllable DWJ parameters have not been fully elucidated. This study delves into the surface morphology, roughness parameters, microhardness, residual stress, and distribution of crystal characteristics in both the depth and radial directions under 2400–36,000 impact cycles of DWJ through peening experiments and material characterization. The findings indicate that the surface morphology is influenced by high-frequency roughness components with limited impact cycles, while low-frequency waviness components gradually take precedence with more impact cycles. As impact cycles increase, certain roughness parameters such as Sq , S5p , S5v , and S10z initially rise until 21,600 cycles, after which they fluctuate within a specific range. Furthermore, DWJ peening leads to an increase in maximum hardness with impact cycles, with the depth of peak value transitioning from the surface layer to the subsurface. The residual compressive stress initially increases and then decreases with impact cycles. Under the experimental conditions, the maximum hardness reaches 268.1HV0.3, a 49.95 % increase from the original state, and the peak residual compressive stress reaches 297.7 MPa with a 310.2 % increase. As impact cycles continue to rise, a balance between material removal and surface hardening is achieved, resulting in the stabilization of maximum hardness and compressive stress as erosion strength grows. Following DWJ peening, there is an increase in the percentage of low-angle grain boundaries, along with enhanced grain refinement, increased geometrically necessary dislocation (GND) density, and the emergence of new phases. As the impact cycles increase, the effects of DWJ peening on crystal grains become more pronounced. Additionally, it has been observed that the lateral jetting influence extends further horizontally than in the depth direction of the incoming jet. It is considered that cyclic hardening and high strain rate effects (1.2 × 104) play significant roles in material hardening and failure. • The study reveals the changes of morphology, hardness, residual stress, and crystal structure as impact cycles increase. • Surface topography initially shows high-frequency roughness, shifting to waviness with increased impacts. • Maximum hardness increases with impact cycles, while residual compressive stress first rises, then falls. • Increasing impact cycles causes a balance between material removal and surface hardening. • The influence of lateral jet on crystal structure exceeds that of the incident jet in horizontal range. [ABSTRACT FROM AUTHOR]

Magnesium (Mg) alloy is an engineering material with tremendous application potential in fields such as transportation, aerospace, electronic instruments, and biomaterials. Nonetheless, the poor abrasion and corrosion resistance hinder the further application of Mg alloy in the field of industrial manufacturing. Solid - state thermal diffusion (SSTD) is regarded as an strategy for creating intermetallic thermal diffusion layers (TDLs) on the surface of Mg alloy, providing protection against wear and corrosion. However, traditional SSTD is a high - temperatures and time - consuming heat treatment process. During the process, Mg alloy may undergo grain coarsening and phase transformations, leading to a degradation in mechanical properties. Additionally, the long - term high - temperature heat treatment will inevitably increase energy consumption and production cost. The present study introduces a solid - state pressure - assisted thermal diffusion (SSPTD) process with the goal of efficiently fabricating Mg Zn intermetallic TDLs on the surface of AZ31 alloy at relatively lower temperatures. As a result, Mg Zn intermetallic TDLs with an outer diffusion layer (ODL) and an internal diffusion layer (IDL) were successfully fabricated on the AZ31 alloy at the average fabrication rate (AFR) of 0.6–3 × 103 μm/h. When the SSTPD treatment was conducted at 360 °C for 60 min under 10 MPa, the surface microhardness of the sample was increased by up to 3.6 times compared to that of the AZ31 alloy, and the corrosion current was reduced by about 74 %. However, the decline in the microhardness and corrosion resistance took place when the sample was subjected to the SSPTD treatment under the condition of higher temperature and pressure (e.g., 400 °C@30 MPa). The degradation in performance was primarily attributed to the increased formation of α - Mg phases and phase transition defects (e.g., cracks and shrinkage cavities) within the TDLs during the SSPTD treatment. • Developed a rapid process for fabricating TDLs on the surface of AZ31 alloy. • Clarified the formation mechanism for Mg Zn intermetallic TDLs. • SSPTD was used to harden surface and improve corrosion resistance of AZ31 alloy. [ABSTRACT FROM AUTHOR]

• Additive manufacturing of CuCrZr alloy for nuclear fusion applications. • Influence of heat treatments on CuCrZr microstructure. • Performance evaluation of CuCrZr printed with 370 W IR laser. In this study, the processability of CuCrZr alloy with additive manufacturing (AM) technology and the performance achievable with Direct Age Hardening treatments for nuclear fusion applications were investigated. This copper alloy is one of the most interesting for the field: it is easier to manufacture through Laser-based additive manufacturing technology and mechanically superior compared to pure copper, and it ensures values of thermal conductivity high enough to be considered a valid substitute for pure copper in many applications. The investigation on CuCrZr alloy was carried out in order to examine the influence of Direct Age Hardening (DAH) treatments on physical and mechanical properties. Laser Powder Bed Fusion technology was used to produce samples with CuCrZr alloy. The additive manufacturing process involved a machine provided with a 370 W IR laser and a preliminary process optimization was carried out to find the printing parameters that assured the highest density (99.15 %), which confirmed the processability of CuCrZr alloy also with low IR laser power. Then, three different DAH treatments were tested and the performance of DAHed material was compared to that of the alloy in as-built conditions. Precipitation phenomena were investigated with DSC analyses, revealing the effectiveness of the treatment already after 1 h. A deep microstructural investigation revealed a fine cellular structure formed during solidification and the presence of nanometric precipitates starting from the as-built condition. The presence of microstructural defects was also investigated. Mechanical performance and thermal conductivity were tested, too: the as-built samples showed limited properties, while very promising results for the use of additively manufactured CuCrZr components have been obtained after the DAHs. The ultimate tensile strength (UTS) and yield strength (YS) doubled the as-built values after 1 h treatment at 550 °C. The thermal conductivity reached three times the initial condition (from 100 W/mK to 300 W/mK). [ABSTRACT FROM AUTHOR]

Enhancing wear resistance is the core factor that prolonged the life of the Cr12MoV mold and elevates the quality of the components produced. Hence, Cr12MoV mold steel was shocked by scanning electron beam (SEB) to improve wear resistance. Results revealed that the segregation eutectic carbides in the surface structure of Cr12MoV steel were dissolved during the shock process of various beam electron beams, and the small particles of carbides produced are helpful in reducing wear. With an energy density of 20 J/mm2, surface roughness of Cr12MoV steel decreases from 2.9 μm to 1.2 μm, the friction coefficient decreases from 0.85 to 0.52. Additionally, the wear capacity also decreases from 0.036 mm3 to 0.011 mm3, and surface wear resistance increases by over 3 times. Grain refinement-induced surface hardening is the primary cause underlying performance improvement. This study provides ideas for improving the surface quality of Cr12MoV steel. [Display omitted] • Through the utilization of SEB to shock the Cr12MoV steel, the surface quality was enhanced. • The segregation of tissue structure was improved by SEB strengthening. • Surface wear resistance of Cr12MoV steel were significantly improved via SEB shock. • The SEB shock changes the wear mechanism of Cr12MoV steel from adhesive wear to abrasive wear. [ABSTRACT FROM AUTHOR]