Solution Strengthening Research Articles

Effect of Si on the Yield Strength of Medium-Carbon Steels Consisting of Ferrite and Pearlite

To enhance the intrinsic yield strength of the ferrite-pearlite microstructure that inevitably forms in a non-quenched-and-tempered steel for large structural components, this study analyzed the effect of adding Si. The resulting ferrite-pearlite microstructure in medium-carbon steels was examined, and the resulting increase in yield strength was interpreted based on strengthening mechanisms. Hot-rolled sheets of 0.3C-1.5Mn steels were fabricated with Si ranging from 0.22 to 2.21 wt. %. Austenitization was conducted at 880°C followed by slow continuous cooling, and ferrite-pearlite microstructures were formed. With increasing Si, the yield strength increased from 409.1 to 573.6 MPa. Although there was a negligible change in the austenitic grain size, the mean diameter of the ferritic grains decreased from 8.8 to 5.0 μm, while the mean interlamellar spacing of the pearlites decreased from 196.6 to 109.9 nm. Using these quantitative data about microstructural features and considering possible strengthening mechanisms, a model to predict yield strength was derived via a constrained optimization method. The resulting model indicated that the major mechanisms are the refinement of pearlitic interlamellar spacing and the solid solution strengthening of ferrite by Si. Their contribution to the increment in yield strength was over 75 %, while others such as ferritic grain refinement and increased pearlitic volume fraction have limited influence.

Effect of aging state on microstructure and properties of heat affected zone in Al-Mg-Si-Cu alloy welded joints

The softening of the heat affected zone (HAZ) remains a significant challenge in fusion welding of novel Al-Mg-Si-Cu alloy, and the underlying mechanisms vary across different aging states. However, limited research has been conducted on this topic. Therefore, this study investigates the influence of various aging states on the microstructure and mechanical properties within the HAZ of welded joints by selecting extrusions treated with T4, T5, and T6 heat treatments. The results indicate that the increase in hardness of HAZ I is attributed to solid solution strengthening. In the HAZ I, the precipitated phases are mostly dissolved into the matrix under the influence of a peak temperature of 464.6 °C, and no residual precipitated phase is detected in T4 and T5 alloy joints, while some undissolved Q phase is observed in T6 alloy joint. The decrease in hardness of HAZ Ⅱ is attributed to the limited precipitation of coarse β" and Q' phases for the T4 alloy welded joints, which weakens the solid solution strengthening. However, the softening mechanisms in the HAZ Ⅱ of the T5 and T6 alloy joints are ascribed to the dissolution of β" and subsequent precipitation of Q' and Q phases. HAZ Ⅲ, close to the base metal, exhibits a lesser degree of influence and thus experiences a gradual recovery in hardness. This study can provide theoretical guidance for the exploration of high-strength, heat-resistant aluminum alloys.

Exceptional strength-ductility synergy in the novel metastable FeCoCrNiVSi high-entropy alloys via tuning the grain size dependency of the transformation-induced plasticity effect

In-depth knowledge of the coupling between grain refinement and the transformation-induced plasticity (TRIP) effect in metastable alloys is a viable approach for the improvement of strength-ductility synergy, which needs systematic research with consideration of commercial austenitic stainless steels and novel high-entropy alloys (HEAs). Accordingly, in the present work, two Si-containing metastable HEAs in the Fe47Co30Cr10Ni5V8-xSix system (x = 3 and 6 at.%) were designed, and the TRIP-assisted AISI 304L stainless steel was also considered for comparison. The alloys were processed by cold rolling and annealing to obtain different grain sizes. Reducing the stacking fault energy (SFE) through adjusting chemical composition contributes to minimizing the detrimental effect of grain refinement on the ductility of TRIP alloys, while extremely low SFE must be avoided owing to the fast kinetics of deformation-induced martensitic phase transformation, which leads to the deterioration of ductility. In contrast to AISI 304L stainless steel, a strong TRIP effect was maintained upon grain refinement in the Fe47Co30Cr10Ni5V2Si6 HEA due to the remaining apparent SFE in the appropriate TRIP range. The tuned kinetics of martensitic transformation was found to be responsible for the exceptional ductility (∼65%) of Fe47Co30Cr10Ni5V2Si6 HEA at an ultrahigh tensile strength of 1250 MPa. Therefore, considering the identical trend of SFE with grain size, an appropriate initial SFE value is important for tuning the grain size dependency of the TRIP effect. Moreover, the ultrahigh strength was attributed to the high volume fraction of α΄-martensite as well as the high strength of the martensite phase due to the high Si content. Accordingly, for achieving strong-yet-ductile HEAs, a high Si content is recommended to benefit from solid solution strengthening in the martensite phase, a specially-designed chemical composition is needed for attaining a high volume fraction of α΄-martensite, and SFE should be in a desirable range to tune the kinetics of martensitic phase transformation.

Relative Hardening Contributions and Ductility of As-prepared and Annealed Nanocrystalline Co-P Electrodeposits

The effect of annealing up to 538 °C (1000 °F) on the hardness and ductility of two electrodeposited bulk nanocrystalline cobalt-phosphorus alloys (L-nCoP, 0.14 at%P and H-nCoP, 2.17 at%P) was investigated. Through a combination of electron microscopy and X-ray/synchrotron diffraction characterization, hardness and bend ductility measurements as well as density functional theory calculations, it is shown that hardness is controlled by four additive contributions. At 0.14 at%P, grain size strengthening and likely grain boundary relaxation are the dominant strengthening mechanisms. In the 2.17 at%P alloy, the contributions from solute strengthening and cobalt phosphide precursors and precipitates are much more significant and typical age strengthening behavior is observed with a peak hardness temperature of 371 °C (700 °F). The bend ductility at 0.14 at%P was in the 12 – 17% range up to 482 °C (900 °F). In contrast, the ductility at 2.17 at%P decreased rapidly with increasing annealing temperatures approaching values less than 1% at 427 °C (800 °F) due to excessive cobalt phosphide precursor and precipitate formation. The dominant deformation mechanism in both alloys was found to be basal dislocation slip.

Evolution of Microstructure and Hardness during Carburization Heat Treatment of Heavy-duty Gear Steels: Numerical Prediction and Experimental Study

Abstract In order to solve the problems of long process cycle, low efficiency and high cost in the carburization heat treatment process of 18Cr2Ni4WA heavy-duty gear steel. The carbon concentration distribution of 18Cr2Ni4WA steel under conventional carburizing process at 930℃ was studied by combining numerical simulation with experimental research. The results show that the carbon concentration distribution predicted by the simulation is in good agreement with the experimental results. The microstructure of the surface layer after low-temperature tempering consists mainly of fine acicular tempered martensite, while the core consists mainly of lath tempered martensite and bainite. The increase in hardness after carburization is mainly attributed to the solid solution strengthening of the carbon atoms. The increase in hardness after cryogenic treatment is mainly attributed to the precipitation strengthening of the carbides. In addition, compared to the conventional carburization at 930°C, the high temperature carburizations at 950°C and 970°C reduced the carburization time by 37.2% and 53.5%, respectively.

Tailoring the microstructure and mechanical properties of wire arc additively manufactured Ti6Al4V alloy by in-situ microalloying with modified nanocarbon

Carbon alloying is a validated strategy for enhancing the mechanical properties of titanium alloys prepared by wire arc additive manufacturing (WAAM). However, achieving uniform carbon distribution, particularly nanocarbon, in the melt pool via the brushing method is challenging, which limits the improvement of mechanical properties. In this paper, nanocarbon was modified by nitric acid hydrothermal treatment and added into the Ti64 melt pool during the WAAM. The distribution of modified nanocarbon in the melt pool was characterized, and the microstructure and mechanical properties of the nanocarbon-alloyed titanium alloy deposits were studied. The findings revealed that the surface of modified nanocarbon generated oxygen-containing functional groups, which enhanced its dispersion in the melt pool. The addition of 0.1–0.3 wt% modified nanocarbon induced no pores in the deposits compared to unmodified ones. The tensile strength of the deposited alloys was continually enhanced with increasing modified nanocarbon content, while the elongation had a peak value. The Ti64 with 0.1 wt% nanocarbon exhibited a balanced comprehensive performance with an ultimate tensile strength (UTS) of 981 MPa coupled with an elongation of 8 %. The achievement of the balanced mechanical performances was attributed to the refinement of α-Ti and solid solution strengthening of nanocarbon. When 0.3 wt% nanocarbon was added, the UTS increased to 1012 MPa but the elongation sharply decreased to 4.5 % due to the precipitation of TiC.

Tailoring β-Ti based shape memory alloy with the exceptional mechanical and functional properties towards biomedical bone implants application

In the present study, the interstitial hydrogen (H) atoms were introduced as β-stabilizing element to tailor the microstructure, martensitic phase transition, and functional properties of Ti-V-Al shape memory alloys for biomedical applications. The results revealed that the addition of interstitial H atoms into Ti-V-Al shape memory alloys induced the transition from a single αˊˊ martensite to the coexistence of β parent phase and α phase, regardless of H content. Moreover, the amount of α phase firstly increases and then decreases in the present Ti-V-Al based shape memory alloy with H content increasing. Besides, H addition resulted in larger lattice distortion, further causing the formation of nano-domains in Ti-V-Al based alloys. Besides, no endothermic and exothermic peaks were detected due to the confinement of α-phase, and the emergence of nano-domains. With increasing H atoms content, the mechanical properties such as fracture strength, hardness, recoverable strain for Ti-V-Al based shape memory alloys initially increased and then decreased. (Ti-13V-3Al)99.2H0.8 shape memory alloys exhibited the highest fracture strength of 862MPa, superior hardness of 307HV, and the fully recoverable strain under 6% pre-strain as well as the moderate elastic modulus, which was mainly attributed to the solution strengthening of interstitial H atoms and the precipitation strengthening of α phase. The best corrosion resistance of Ti-V-Al based shape memory alloys was observed with the 2.0at. % H, which was due to the formation of TiO2, Ti2O3 oxide films. Moreover, the best wear resistance with the lower wear rate of 0.9347×10-6 mm3/N mm was obtained in (Ti-13V-3Al)99.2H0.8 shape memory alloy, due to the integrated effects of higher microhardness, reinforcing effect of α phase and lubrication effect of the hydrogenated film.

Investigation on precipitate behavior and mechanical properties of Al-Zn-Mg-Cu alloys with various Zn/Mg ratios

The effect of Zn/Mg ratio on the microstructure and properties of Al-Zn-Mg-Cu alloys under single-step and double-step aging processes were investigated by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), electron backscatter diffraction (EBSD), as well as hardness, room temperature tensile, and fracture toughness testing. During single-step aging, as the Zn/Mg ratio increases, the aging response of the alloys accelerates. However, the peak hardness and strength gradually decreased while the average size of precipitates increased. During double-step aging, as the secondary aging time increases, the strength and hardness of the alloys gradually decrease. Additionally, the higher the Zn/Mg ratio, the faster the strength and hardness decline. Under the T74 temper, the alloy with higher Zn/Mg ratios exhibits lower hardness and strength but better fracture toughness and larger precipitate sizes. A simple method was proposed to statistically determine the critical diameter size of GPII zone and η′ phase, which was approximately 4.47 nm. A strength model was developed to predict the yield strength of alloys, considering factors such as solid solution strengthening, grain boundary strengthening, and precipitation strengthening. The model demonstrates good predictive accuracy for both peak-aged and T74 temper alloys, providing valuable guidance for alloy design and microstructure regulation.

A novel process for simultaneously improving the strength and plasticity of 18Ni(350) maraging steel

A novel process involving cold deformation, cyclic solution, and two-step aging is developed for simultaneously improving the strength and plasticity of 18Ni(350) maraging steel. The strengthening and toughening mechanisms are elucidated by microstructural characterization and tensile property measurements. Cold deformation and cyclic solution refine the final martensite grains. In addition, two-step aging ensures the formation of numerous fine precipitates and a small amount of fine reversed austenite. Ultra-high strength is achieved by a combination of solid-solution, grain refinement, dislocation, and precipitation strengthening, with the latter having the largest contribution. Compared with the traditional process, the UTS and elongation are increased by 9.13% and 22.83%, respectively, to 2511 MPa and 5.81%, demonstrating the effectiveness of this novel process.

Influence of Al and Ti Alloying and Annealing on the Microstructure and Compressive Properties of Cr-Fe-Ni Multi-Principal Element Alloy

This study meticulously examines the influence of aluminum (Al) and titanium (Ti) on the genesis of self-generated ordered phases in high-entropy alloys (HEAs), a class of materials that has garnered considerable attention due to their exceptional multifunctionality and versatile compositional palette. By meticulously tuning the concentrations of Al and Ti, this research delves into the modulation of the in situ self-generated ordered phases’ quantity and distribution within the alloy matrix. The annealing heat treatment outcomes revealed that the strategic incorporation of Al and Ti elements facilitates a phase transformation in the Cr-Fe-Ni medium-entropy alloy, transitioning from a BCC (body-centered cubic) phase to a BCC + FCC (face-centered cubic) phase. Concurrently, this manipulation precipitates the emergence of novel phases, including B2, L21, and σ. This orchestrated phase evolution enacts a synergistic enhancement in mechanical properties through second-phase strengthening and solid solution strengthening, culminating in a marked improvement in the compressive properties of the HEA.

Mechanisms of hardening of heavy-loaded rails made of hypereutectoid steel during long-term operation

Using transmission electron microscopy methods, the structural-phase states and defective substructure were studied at distances of 0; 2 and 10 mm from the surface along the central axis and rounding radius of rails head fillet. Differentially hardened long rails of the DT400IK category made of hypereutectoid steel have been studied after operation on the Trans-Baikal Railway (passed tonnage equal to 234.7 million tons gross). It has been established that steel strength characteristics are determined by certain physical mechanisms. A qualitative assessment of the contributions from crystal lattice friction, solidsolution strengthening, strengthening of the pearlite component, incoherent cementite particles, grain boundaries and subboundaries, dislocation substructure and internal stress fields was carried out, and their hierarchy was established. A quantitative assessment of the additive yield strength of steel in different directions was carried out depending on the distance from the rolling surface. It is shown that the main mechanisms of strengthening are strengthening by incoherent particles, long-range stress fields and substructural strengthening. The additive yield strength on the fillet surface is significantly greater than on the rolling surface of the head along the central axis.

Microstructure development and strengthening behaviour in hot-extruded Ti-Mo alloys with exceptional strength-ductility balance

A series of strong and ductile Ti-Mo alloys containing 2.5, 5, 7.5 and 10 wt% Mo was experimentally investigated by a two-stage blended-elemental powder metallurgy process. This process consisted of a spark plasma sintering stage for powder-consolidation and in-situ-homogenisation, and a hot extrusion stage for densification and microstructure enhancement. Microstructures in the extruded alloys changed from α dominant to β dominant with molybdenum addition. Simultaneously, a grain refinement effect was observed due to suppressed α precipitation and increase β retention. A significant strengthening effect was observed with molybdenum addition. In comparison with similarly processed commercially pure titanium, Ti-10Mo exhibited a yield strength improvement of 290 % to 1382.8 MPa, and an ultimate tensile strength improvement of 239 % to 1496.5 MPa. Meanwhile, Ti-5Mo exhibited a yield strength improvement of 211 % (1007.9 MPa) without any substantial reduction in ductility, resulting in an exceptional tensile toughness of 361.3 MJ.m−3. A quantitative analysis of strengthening mechanisms reveals considerable strengthening effects from solid solution strengthening, dislocation strengthening, and grain refinement effects. These factors arise from the novel multi-modal microstructures formed by thermomechanical processing at super-transus temperatures. The newly achieved balance of strength and ductility appears to be unrivalled amongst all previously reported binary Ti-Mo alloys.

Role of Mo and Zr Additions in Enhancing the Behavior of New Ti–Mo Alloys for Implant Materials

AbstractThe utilization of Ti–Mo alloys in biomedical applications has gained attention for use in biomedical applications owing to their non-toxicity, reasonable cost, and favorable properties. In the present study, Ti–12Mo–6Zr and Ti–15Mo–6Zr alloys were prepared using elemental blend and mechanical alloying techniques. The effect of alloying elements Mo and Zr of Ti–Mo alloy, as well as the effect of fabrication techniques of Ti–Mo–Zr trinary alloys, were investigated. Thermodynamic calculations supported by CALPHAD analysis revealed that the addition of Zr increases lattice distortion, which contributes to enhancing the strength. Conversely, adding Mo decreases the enthalpy, facilitating improved mixing and solid solution formation. The as-sintered samples were characterized by X-ray diffraction, optical microscope, and scanning electron microscopy, and their microhardness, compressive, and corrosion behavior were investigated. Among all the investigated alloys, Ti–15Mo–6Zr alloy prepared by the mechanical alloying technique, milled for six hours at 300 rpm, compacted at 600 MPa, and sintered at 1250 ℃, shows good comprehensive mechanical properties with a preferable compressive strength (− 1710 MPa) and hardness (396 HV5), as well as the lowest wear rate (0.69%) and corrosion rate (0.557 × 10–3 mm/year). This can be related to the solid solution strengthening and relative density, together with dispersion and precipitation strengthening of the α phase. Remarkably, the combination of high mechanical and corrosion properties can be achieved by tailoring the content of the α phase, controlling the density, and providing new fabricating techniques for β Ti alloys. Graphical Abstract

High-throughput screening of the potential alloying elements for high-strength Mg alloys based on solid-solution strengthening

Abstract 49 types of alloy atomic dopants and their effects on the doping stability and micro-mechanical behaviour of magnesium matrix were investigated using density functional theory and high throughput first-principles calculations. Geometry optimization was performed for each doping system, and the ability of atom doping into the magnesium matrix was assessed based on the doping energy and atomic radius. Results show that the transition metal elements have negative or near negative doping energy, especially for the elements with a radius that similar to Mg. The micro-mechanical properties of the doping system were evaluated by computing the fracture energy and theoretical tensile stress. Through a screening on the doping stability and strengthening effect of 49 types of alloy atoms, a set of elements (Re, Os, Ir, Tc and W, etc.) are screened out that could strengthen the magnesium matrix with a good doping stability. The high throughput screen results serve as a theoretical guide for the selection of appropriate alloy elements for designing the high-strength magnesium alloys in the regime of solid solution strengthening effects.

Microstructure Characteristics and Elevated-Temperature Wear Mechanism of FeCoCrNiAl High-Entropy Alloy Prepared by Laser Cladding

This paper investigated the FeCoCrNiAl high-entropy alloy on H13 steel, prepared using laser cladding, to improve the elevated-temperature wear resistance of the alloy. The results revealed that FCC and BCC phases, in terms of the coating, produced a large dislocation density. The coating exhibited a columnar and equiaxed crystal microstructure. With the comprehensive effects of fine-grain strengthening, solid solution strengthening, and dislocation strengthening, the average hardness of the coating (500 HV0.1) was improved by 150% compared with that of H13 steel (200 HV0.1). The wear experiments were conducted at 623 K, 723 K, and 823 K. Compared with H13 steel, the wear volume of the coating decreased by 59.20%, 70.79%, and 78.20% under different temperatures. The wear forms impacting the coating were mainly abrasive wear and oxidation wear. However, H13 steel presented adhesive wear and fatigue wear, in addition to abrasive wear and oxidation wear.

Microstructure and wear characteristics of laser-clad Ni-based self-lubricating coating incorporating MoS2/Ag for use in high temperature

Nickel-based self-lubricating cladding containing Ag and MoS2 was prepared on Ti6Al4V alloy using laser cladding. The microstructure, microhardness and wear behaviour were measured and analysed. The coating was mainly composed of Ti2Ni and TiNi as the matrix, and TiC and TiB2 as the reinforcements. A new phase of Ti2SC was synthesized in situ in the coating, whereas Mo was consolidated in the matrix. The microhardness of the coating is greatly increased by in-situ generation of reinforcement phase and solution strengthening, with an average hardness of 823.6HV0.2, which is about 2–3 times that of the substrate. When the temperature increased to 600 °C, the coefficient of friction and wear rate of the coating decreased. The friction coefficient and the wear rate of the coating were greatly reduced at 800 °C. The wear rate of the coating decreased to 4.85 × 10−6 mm3, which decreased by nearly an order of magnitude compared with the coating's wear rate at room temperature. The anti-friction effect of the lubricating phase not only counteracted the effect of the decreased hardness on the wear rate, but also played a more obvious anti-friction effect. In the high-temperature stage, MoO3 and silver molybdate compounds produced by the tribological chemical reaction of wear surfaces could significantly improve the density of the enamel layer on the wear surface.

Microstructure evolution, mechanical properties, and corrosion behavior of in-situ TiC/TC4 composites through Mo addition

To further improve the mechanical properties and corrosion resistance of the composites, in-situ TiC/TC4-xMo composites were fabricated. The effect of Mo content on the microstructure evolution, mechanical properties, and corrosion behavior of the composites was investigated. The results show that with the increase of Mo content, the amount of β-Ti phase and the size of the TiC particle increase. The mechanical properties and corrosion resistance of the composites can be significantly enhanced through Mo addition. The TiC/TC4 composites containing 10 wt% Mo exhibits superior mechanical properties and corrosion resistance. Grain refinement, load transfer, and solid solution strengthening are the main strengthening mechanisms for improving the strength of composites. In addition, the increase of the β-Ti content, the presence of TiC, and the solid solution of Mo elements contribute to enhancing the corrosion resistance of the composites.

Analysis of fatigue fracture mechanism of laser spiral welding of dissimilar metals of 6082 high strength aluminum alloy and DP980 high strength dual phase steel

This paper investigates the relationship between weld quality, influencing factors, microstructure and mechanical properties of laser spiral dissimilarity welding of 6082 high-strength aluminum alloy and DP980 high-strength dual-phase steel, focusing on the fatigue properties and fracture mechanism of 6082-DP980 dissimilar metal welded joints. The research shows that intermetallic compound layers (IMCs) dominate the fatigue crack initiation stage and part of the crack extension stage, two fatigue crack initiation modes are obtained, one is the main crack initiation mode along the FeAl and FeAl2 interlayer, and the other is the secondary crack initiation mode along the Fe3Al and FeAl interlayer. In the crack propagation stage, due to the diffusion of Fe and Al elements generated by IMCs during the welding process, solid solution strengthening, intergranular strengthening and grain boundary strengthening, in the fatigue crack propagation stage formed a hardened zone, hindering the main crack to continue to expand along the IMCs, the main crack shifted to the expansion of the 6082 base material, thus extending the fatigue life.

Strengthening effects from Mg and Ni in Al-mischmetal eutectic alloys: Insights from microstructures and Bayesian analysis

This study investigates, both experimentally and via machine-learning modeling, the strengthening mechanisms and effects of Mg and Ni additions to Al-MM (mischmetal, a sustainable Ce+La+Nd mixture to replace Ce) alloys, aiming to develop creep- and coarsening-resistant Al-MM-Mg-Ni alloys with a focus on twin eutectic co-solidification microstructures. Based on near-eutectic Al-9MM (wt%) alloy, the Mg and Ni additions introduce solid-solution and eutectic strengthening, respectively. Ternary hypo-eutectic Al-9MM-0.25/0.5/0.75Mg variants improve hardness up to 592 MPa. Ternary Al-9MM-2/4Ni display hypo-eutectic microstructures. Al-9MM-2Ni shows separated growth of Al11MM3 and Al3Ni eutectic phases, while Al-9MM-4Ni features finely intertwined Al11MM3-Al3Ni fibers from co-solidification. The hyper-eutectic Al-9MM-5Ni contains primary Al3Ni particles alongside the intertwined fibers, raising the hardness to 739 MPa. Finally, quaternary Al-9MM-0.5/0.75Mg-4/4.5Ni alloys maintain hypo-eutectic microstructures with a significant increase of hardness to 929 MPa. The series Al-9MM, Al-9MM-0.75Mg, Al-9MM-4Ni, and Al-9MM-4.5Ni-0.75Mg exhibits increasing tensile yield strengths of 70, 83, 88, and 105 MPa, with decreasing ductility of 12.0, 5.8, 2.0, and 0.8 %. All Al-9MM-Mg-Ni alloys exhibit excellent hardness retention and coarsening resistance after thermal exposure at 300 or 350°C for up to 11 weeks. A machine-learning model accurately predicts the alloy's hardness evolution under thermal exposure. Feature analysis quantitively shows the strengthening impact of MM, Ni, and Mg addition and demonstrate enhanced strengthening retention, under thermal exposure, of Al11MM3 over Al3Ni, alongside the beneficial effects of Mg homogenization. At 300 °C, Al-9MM-Mg-Ni alloys demonstrate higher creep resistance than most precipitation-strengthened Al-Sc-Zr-based alloys and solid-solution-strengthened Al-Mg alloys, with Al-9MM-4Ni as the best performer.

Effect of plasma nitriding on microstructure and wear behavior of electrodeposited FeCoNiCr coating

An (FeCoNiCr)N high-entropy alloy coating with a single FCC phase was fabricated on 304 stainless steel by electrodeposition and plasma nitriding. The results indicated that the FeCoNiCr coating exhibited typical granular morphologies and a nearly equiatomic ratio of four elemental compositions. After nitriding, the coating primarily consisted of a high-entropy solid solution phase and a CrN phase, with the microstructure of the (FeCoNiCr)N coating being significantly refined due to the effect of crystallization. The microhardness of the (FeCoNiCr)N coating was 781.30 ± 20.3 HV0.5, considerably higher than that of the FeCoNiCr coating, which was 496.48 ± 21.82 HV0.5. Additionally, the (FeCoNiCr)N coating demonstrated a low friction coefficient and a wear rate of 0.59 and 6.8 × 10−8 mm3/N mm, respectively. The fine microstructure and high resistance to plastic deformation, attributed to solid solution strengthening and dispersion strengthening, were the primary factors contributing to the excellent wear performance of the (FeCoNiCr)N coating.