High-entropy Alloy Coatings Research Articles

Construction of hard BCC phases FeCrVMnTix wear-resistant high-entropy alloy coatings enhanced by solid solution of Ti elements

To address the complex working conditions encountered by 1Cr13 ferritic/martensitic steel during operation, it is imperative to develop high-entropy alloys (HEAs) protective coatings with enhanced friction resistance. In this work, guided by the valence electron concentration criterion, we constructed a single-phase body-centered cubic (BCC) structure with high hardness. This was achieved through the introduction of titanium (Ti), which has a significantly different atomic radius compared to other elements. FeCrVMnTix (x = 0, 0.5, 1.0, 1.5, and 2.0) coatings were fabricated on 1Cr13 steel surfaces using laser cladding techniques, and the microstructure, mechanical properties, and wear-resistance properties of Ti-doped HEA coatings were investigated. The results reveal that the FeCrVMnTix coatings are comprised of a BCC solid solution. Increasing Ti content refined the dendritic structure of the coatings, enhancing the Vickers hardness from 4.35 GPa to 8.27 GPa and the Young's modulus from 232.6 GPa to 273.2 GPa. Additionally, the wear rate decreased from 3.07 × 10−5 mm3·N−1·m−1 to 4.94 × 10−6 mm3·N−1·m−1. Notably, the FeCrVMnTi2.0 coating demonstrated excellent wear resistance that can be attributed to the solid solution strengthening effect of Ti. These findings underscore the pivotal role of Ti in enhancing the wear resistance of the coatings.

Design, microstructure, wear and corrosion behaviors of laser clad FeNiCoCrMo0.3Nbx hypoeutectic high entropy alloys coatings

FeNiCoCrMo0.3Nbx (x = 0.15, 0.40 and 0.55 in molar ratio) hypoeutectic high entropy alloys (HEAs) coatings are prepared by laser cladding (LC) designed by binary eutectic composition strategy. Nbx HEAs coatings present FCC + Laves duplex. Under the joint action of various strengthening mechanisms, the average microhardness of Nb0.15, Nb0.40 and Nb0.55 coatings is as high as 480.5 ± 7, 510.2 ± 6 and 540.6 ± 5 HV0.2, respectively. The unique fluctuating oxide film of the HEAs coatings plays a role in reducing wear, with the specific wear rates of 0.37 × 10−4, 0.22 × 10−4 and 0.18 × 10−4 mm3/Nm for Nb0.15, Nb0.40, and Nb0.55 cladding layers, respectively. The Nbx HEAs coatings displayed excellent corrosion resistance in 0.5 M H2SO4 solution. For Nb0.15 and Nb0.40 HEAs coatings, the increase of Nb promotes the formation of passivation film and improves corrosion resistance. However, the higher dislocation density intensifies the chemical inhomogeneity of the alloy due to excessive addition of Nb, which is not conducive to the corrosion resistance of Nb0.55 HEAs coating. The Nb0.40 cladding layer exhibits better corrosion resistance, and the Icorr is only 1.24 ± 0.6 μA/cm2. Combined with Mott-Schottky (M-S) test, the carrier densities (ND) of three HEAs coatings are increased in the order of Nb0.40 (1.09 × 1021 cm−3) < Nb0.15 (1.83 × 1021 cm−3) < Nb0.55 (3.57 × 1021 cm−3), indicating that the strong protective passivation film is also a key factor to achieve better corrosion resistance.

Optimizing substrate bias voltage to improve mechanical and tribological properties of ductile FeCoNiCu high entropy alloy coatings with FCC structure

Conventional hard coatings are limited in their tribological applications due to their high brittleness. High-entropy alloy (HEA) coatings, which combine high toughness and hardness, represent a new class of tribological coatings with great potential. The microstructure and stress state of HEA coatings can be significantly affected by the deposition parameters of magnetron sputtering, which can regulate their mechanical and tribological properties. In this study, DC magnetron sputtering with varying substrate bias voltages was used to deposit FeCoNiCu HEA coatings with an FCC single phase structure on 316 stainless steel. The microstructure, mechanical, and tribological properties of these coatings were studied in detail. The residual tensile stress of the coatings decreases, while toughness and hardness increase as the bias voltage increases. The coatings exhibited optimal toughness, highest hardness (11.3 GPa), and the lowest wear rate (as low as 6.01 × 10−5 mm3/N·m) when the bias voltage was set to −200 V. The formation of a metal oxide adhesion layer during friction improved the tribological properties of the coatings. This study demonstrates that optimizing the deposition bias voltage is an effective way to improve the mechanical and tribological properties of high-entropy, face-centered cubic alloy coatings, which are intrinsically tough and ductile.

Effect of Laser Multiple Remelting on the Geometric Parameters and Component Distribution of CrMnFeCoNi High-Entropy Alloys Coatings Fabricated on Al Alloy by Laser Cladding

Effect of Laser Multiple Remelting on the Geometric Parameters and Component Distribution of CrMnFeCoNi High-Entropy Alloys Coatings Fabricated on Al Alloy by Laser Cladding

Microstructure, multi-scale mechanical and tribological performance of HVAF sprayed AlCoCrFeNi high-entropy alloy coating

Thermal spray high-entropy alloy (HEA) coatings have demonstrated potential for improving the wear resistance of conventional materials used in extreme engineering environments. In the present work, an equiatomic AlCoCrFeNi HEA coating was manufactured using the high velocity air fuel (HVAF) process. The phase and microstructural transformations in gas-atomized (GA) powder during HVAF spraying were analyzed using SEM, EDS and EBSD techniques. The tribological properties of this HEA coating sliding against an Al2O3 ball at both room temperature (RT) and 600 °C were also evaluated. The GA powder was composed of Body Centred Cubic (BCC) + ordered BCC (B2) phases, which transformed to BCC + B2 + minor Face Centred Cubic (FCC) phases during the HVAF coating process, validating the thermodynamic phase prediction projected by the Scheil simulation for non-equilibrium processing conditions. The rapid solidification and high velocity impact-assisted deformation of GA powder resulted in significant grain refinement in the HVAF coating, which ultimately improved the mechanical properties at both micro and nanoscale levels. The wear resistance of the HEA coating at RT was severely impacted by the relatively brittle BCC/B2 phase structure, leading to susceptibility to abrasive wear and surface fatigue. The wear resistance at 600 °C was slightly lower at RT due to the formation of a brittle oxide layer on the worn surface, which induced surface fatigue and aggravated mass loss of the coating.

Microstructure and wear properties of carbide reinforced high-entropy alloy coatings on EA4T steel via vibration assisted TIG-cladding using WC core spiral AlCuNiCrTi-CWW

Aiming at the difficulty preparing high-entropy alloy (HEA) coating by adding carbide powder using TIG-cladding, the WC core spiral CWW prefabricated vibration assisted TIG-cladding method is proposed in this work. The HEA coating (S1-coating) was prepared on the EA4T steel using AlCuNiCrTi cable-type welding wire (CWW) via TIG-cladding, then the WC reinforced HEA coating (S2-coating) was produced using spiral AlCuNiCrTi-CWW with WC powder core by TIG-cladding. Finally, another WC reinforced HEA coating (S3-coating) via vibration assistance TIG-cladding using the same material as S2-coating. The S1-coating is composed of BCC and FCC solid solutions. Except for the same phases as S1-coating, TiC appeared in the S2-coating and the S3-coating. Due to the grain refinement effect caused by vibration, the S3-coating has the maximum microhardness (725HV), lowest friction coefficient (0.42) and the smallest volume wear rate (0.1397 × 10−4 mm3/N·m). The addition of vibration assistance effectively improves the microhardness and wear resistance of the coating without changing CWW composition.

Molecular Dynamics Study on Wear Resistance of High Entropy Alloy Coatings Considering the Effect of Temperature.

High entropy alloys have excellent wear resistance, so they have great application prospects in the fields of wear resistance and surface protection. In this study, the wear resistance of the FeNiCrCoCu high entropy alloy coating was systematically analyzed by the molecular dynamics method. FeNiCrCoCu high entropy alloy was used as a coating material to adhere to the surface of a Cu matrix. The friction and nanoindentation simulation of this coating material were carried out by controlling the ambient temperature. The influence of temperature on its friction properties was analyzed on five aspects: lattice structure, dislocation evolution, friction coefficient, hardness, and elastic modulus. The results show that with the increase of temperature, the disorder of the lattice structure increases, which leads to an increase of the tangential force and friction coefficient in the friction process. At 300 K and 600 K, the ordered lattice structure of the high entropy alloy coating material is basically the same, and thus its hardness is basically the same. However, the dislocation density at 600 K is significantly reduced compared with that at 300 K, resulting in an increase of the elastic modulus of the material from 173 GPa to 219 GPa. At temperatures of 900 K and 1200 K, lattice disorder takes place rapidly, and dislocation density also decreases significantly, resulting in a significant decrease in the hardness and elastic modulus of the material. When the temperature reaches 900 K, the wear resistance of the FeNiCrCoCu high entropy alloy coating decreases sharply. This work is of great value in the analysis of wear resistance of high entropy alloys at high temperature.

Microstructures and Corrosion Behaviors of Laser Remelted High-Velocity Oxygen Fuel Sprayed Co-free Non-equiatomic Al0.32CrFeTi0.73Ni1.50 High-Entropy Alloy Coating

Microstructures and Corrosion Behaviors of Laser Remelted High-Velocity Oxygen Fuel Sprayed Co-free Non-equiatomic Al0.32CrFeTi0.73Ni1.50 High-Entropy Alloy Coating

Advanced wear protection at high temperatures: A study of Al20V20Cr20Nb(40-x)Mox RHEA coatings on Ti6Al4V by laser cladding

Al20V20Cr20Nb(40-x)Mox Refractory High Entropy Alloys (RHEAs) coatings were applied to Ti6Al4V surfaces via laser cladding. These coatings, primarily in a single BCC phase with dendritic microstructures, demonstrated varied wear resistance. Notably, the Al20V20Cr20Nb10Mo30 exhibited the highest wear resistance, achieving a wear rate reduction of 98.35 % and 99.28 % compared to uncoated Ti6Al4V and the Al20V20Cr20Nb30Mo10 coating, respectively. This superior performance is attributed to the formation of a dense oxide film and the beneficial presence of rod-like Al2(MoO4)3 and Cr2(MoO4)3 oxides, which enhance mechanical clamping at the surface. The study highlights the critical role of rapid oxide film formation at 600 °C in enhancing the high-temperature wear resistance of Ti6Al4V, offering insights into the tribological behaviour of RHEA coatings under extreme conditions.

Microstructure and properties of novel nano-lamellar Al27Nb18(CrZr0.5)xTi55−1.5x eutectic high-entropy alloy coatings on Ti-6Al-4V alloy

The serious wear damage caused by low surface hardness and poor wear resistance of titanium alloy severely limits its further application in engineering field. In this work, novel eutectic high entropy alloys (EHEAs) were designed by means of infinite solution strategy combined with mechanical assistance to explore the application of EHEAs in the field of surface protection coating. Three types of EHEA coatings were achieved through the adjustment of the Cr and Zr element proportions on Ti-6Al-4V alloy by laser cladding. The microstructure was eutectic structure composed of Laves and BCC/B2 phases with superlattice structure. A significant presence of stacking faults, Lomer-Cottrell locks and other defects is observed within the BCC/B2 phase, which contributes to the enhancement of both microhardness and nano-hardness. Al27Cr25Ti18Nb18Zr12 coating showed excellent wear resistance and minimal volume loss, which are 0.340 (65.38 % of the substrate) and 6.71 × 10−5 mm3/N·m (16.89 % of the substrate). Notably, the three alloys exhibit interesting selective corrosion behavior, which is mitigated by the presence of a nano-lamellar eutectic structure that limits pitting propagation.

Effect of WC content on the microstructure and wear resistance of laser cladding AlCoCrFeNiTi0.5 high-entropy alloy coatings

AlCoCrFeNiTi0.5+x(WC) high-entropy alloy (HEA) coatings with varying WC content (x = 0, 10, 20, and 30 wt%) were prepared by laser cladding. The results of the microstructure analysis showed that the AlCoCrFeNiTi0.5 coating consisted of body-centered cubic (BCC1) and BCC2 phases, while additional TiC and W2C phases formed within the coating with the WC content reaching 20 wt% mol. The addition of WC particles acted as a barrier to grain growth, preventing grains from growing larger. Additionally, the in-situ TiC phase was distributed at the grain boundaries and further inhibited the grains growth. The grain refinement and increase in dislocation density jointly improved the ability of the coating to resist plastic deformation. Due to the addition of the WC particles, the micro-hardness and wear resistance of the coatings improved considerably. The AlCoCrFeNiTi0.5 coating with 30 wt% WC exhibited the best performance. Its hardness increased by 35.8 % and wear rate decreased by 58.2 % compared with the AlCoCrFeNiTi0.5 coating.

Synthesis of a novel AlBeSiTiV light weight HEA coating on SS316 using atmospheric plasma spray process

High Entropy Alloys (HEAs) are currently a subject of significant research interest in the fields of materials science and engineering. They are rapidly evolving due to their exceptional properties, and there is considerable focus on expanding their application potential by developing HEA coatings on various substrate materials. This area of study holds promise for advancing technology and innovation in diverse industries. In this study, a novel equiatomic AlBeSiTiV Light Weight HEA was synthesized via mechanical alloying and was sprayed on the substrate SS316 by the thermal spray process. The microstructural characterization revealed that synthesized HEA had a major FCC phase and the average coating thickness was observed to be 150 μm. The average microhardness was measured to be 975 ± 13 HV for the coating which was five times than the substrate. The coated samples' wear resistance was found out using a pin-on-disc apparatus by varying the wear process parameters and Taguchi's L27 Orthogonal Array was used to interpret the parametric influence on wear rate. ANOVA and regression analysis revealed applied load to be the most significant factor followed by distance and velocity. The major wear mechanisms observed were adhesion abrasion and oxidation, and the formation of tribolayer was observed at higher velocity and distance.

Machine learning based prediction of Young's modulus of stainless steel coated with high entropy alloys

The High Entropy Alloy (HEA) coatings exhibit diverse properties contingent upon their composition and microstructure, addressing current industrial requirements. Machine Learning (ML) regression emerges as a proficient solution for predicting the properties of HEA coatings, offering a significant reduction in experimental work. The ML regressions including Support Vector Regression (SVR), Gaussian Process Regression (GPR), Ridge Regression (RR), and Polynomial Regression (PR), are effectively employed to predict Young's modulus of HEA coated Stainless Steel (SS) through a significant database. The statistical responses of the developed regression models are analyzed through evaluation indices of Coefficient of determination (R2), Mean Absolute Error (MAE), and Root Mean Square Error (RMSE). Among the regression models, the 2-degree PR model stands alone with a high prediction accuracy of R2-0.95, MAE-16.12, and RMSE-21.53. The 2-degree PR model demonstrates a significant correlation between the predicted and experimental Young's modulus, contributing to the accurate prediction of unknown Young's modulus of the HEA-coated SS. The prediction of Young's modulus by the PR model is more reliable, as proved by an error percentile of ±4.76 %, compared to the experimental values of Young's modulus.

Atomic-scale investigation of the synergistic impact of Mo and Nb addition on enhancing the performance of laser cladding FeCoCrNi-based high entropy alloy coatings

Utilizing synchronous powder feeding laser cladding technology, two high entropy alloy coatings, FeCoCrNiMo and FeCoCrNiMoNb, were deposited on the surface of low-carbon steel. An in-depth investigation into the synergistic interplay of Mo and Nb on FeCoCrNi-based high entropy alloy coatings was conducted. The findings reveal that FeCoCrNiMo comprises an FCC stable solid solution, Mo3Co3C, and Ni3Mo3C. Conversely, FeCoCrNiMoNb exhibits a composition comprising an FCC stable solid solution phase, NbC, and (Mo, Nb)C. This is attributed to the robust interaction between Mo and Nb, wherein Mo infiltrates the NbC lattice, substituting for a portion of Nb atoms. Notably, the synergistic influence of Mo diminishes the formation energy of NbC, thereby lessening the energy barrier encountered during the nucleation of (Mo, Nb)C. Consequently, the incorporation of Mo facilitates the precipitation of Nb. The refined microstructure and solid solution strengthening effect of (Nb, Mo)C and NbC, coupled with their elevated Vickers hardness and hard elastic ratio, contribute significantly to the notable enhancement in surface hardness and wear resistance observed in the FeCoCrNiMoNb high entropy alloy coating.

INFLUENCE OF SUBSTRATE TEMPERATURE ON THE MICROSTRUCTURE AND PROPERTIES OF CoCrFeNiNbx HIGH ENTROPY ALLOY COATINGS

This work studies the effect of the substrate temperature on the microstructure and properties of CoCrFeNiNbx high entropy alloy (HEA) coatings fabricated by magnetron sputtering. The results indicate that all three CoCrFeNiNbx HEA coatings were composed of a simple FCC solid solution with a columnar structure. As the substrate temperature increased, Nb content in the FCC matrix increased while the grain size first decreased and then increased. Accordingly, CoCrFeNiNbx HEA coatings exhibited an increasing micro-hardness and a decreasing fracture toughness with the increasing substrate temperature. Moreover, CoCrFeNiNbx HEA coating deposited at 200∘ had better corrosion performance, which was due to its better surface quality and denser columnar structure compared to the other two coatings.

Wear and high-temperature oxidation resistance of (AlCrFeTiV)100-xNix high-entropy alloy coatings prepared by laser cladding on Ti6Al4V alloy

A series of novel (AlCrFeTiV)100-xNix (x = 0, 10, 20, and 30) high-entropy alloy (HEA) coatings were prepared via laser cladding on Ti6Al4V. The microstructure evolution, hardness, wear behavior, and high-temperature oxidation resistance were systematically studied. The results indicate that the microstructure of the (AlCrFeTiV)100-xNix HEA coatings gradually transition from BCC1 (enriched Ti, Al) + BCC2 (enriched V, Cr) + Laves phases to BCC + NiAl-type B2 + Laves phases with increasing x content. Ni addition gradually increased the hardness and wear resistance of the HEA; however, the formation of the B2 phase led to a slight decrease in hardness. Among the studied compositions, the Ni30 HEA coating exhibited the best wear resistance, with a wear mass loss of 8 mg·mm−2 and a wear mass loss of only 13.6 % for Ti6Al4V. The wear mechanism of the (AlCrFeTiV)70Ni30 HEA coating is a comprehensive effect of abrasive wear, oxidative wear, and adhesive wear. Compared with those of Ti6Al4V, the oxidation rates of the AlCrFeTiV, Ni0, Ni10, Ni20, and Ni30 HEA coatings decreased by 65 %, 62 %, 55 %, and 61 %, respectively. The improved oxidation resistance is attributed to the formation of a dense NiXO4 spinel oxide layer. The Ni20 HEA coating exhibited excellent oxidation resistance at 800 °C, and the oxidation mechanism was further investigated via first-principle calculations. The results indicate that there is strong charge transfer between O atoms and Ni and Al, which tends to form NiAlO4-type spinel oxides.

Study on the microstructure and properties of Mo0.5VNbTiCr0.25 refractory high-entropy alloy coatings

Study on the microstructure and properties of Mo0.5VNbTiCr0.25 refractory high-entropy alloy coatings

Microstructure and performance of AlCoCrFeNiCu(CeO2)X high-entropy alloy coatings by plasma cladding

AlCoCrFeNiCu(CeO2)X (x=0 wt%, 0.3 wt%, 0.6 wt%, 0.9 wt%, and 1.2 wt%) HEA coatings were applied via plasma cladding technology to a 35CrMo steel surface in this investigation. Electron back-scattering diffraction (EBSD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used to analyze the phase composition and microstructure of the coatings. A microhardness meter, a nanoindenter, a wear test machine, and an electrochemical station were used to assess the coating performance. The findings demonstrate that the phase composition of the coatings is unaffected by the addition of CeO2, with all coatings consisting of FCC and BCC phases. CeO2 was added to the coatings to refine their grain size and increase their proportion of high angle grain boundaries (HAGBs), BCC phase content, and geometrically necessary dislocation (GND) density. These improvements led to significant increases in the microhardness and wear resistance of the coatings. The 0.3 wt% CeO2 coating has the best corrosion resistance, which is caused by a number of factors including the element distribution, grain size, content of each phase, and phase distribution of the coatings. The corrosion resistance of the coating increases and then decreases nonlinearly with increasing CeO2 content.

Microstructures and Corrosion Behaviors of Non-Equiatomic Al0.32CrFeTi0.73(Ni1.50−xMox)(x = 0, 0.23) High-Entropy Alloy Coatings Prepared by the High-Velocity Oxygen Fuel Method

The non-equiatomic Al0.32CrFeTi0.73(Ni1.50−xMox) (x = 0, 0.23) high-entropy alloy (HEA) coatings were prepared by the high-velocity oxygen fuel (HVOF) method. The microstructures and corrosion behaviors of the HVOF-prepared coatings were investigated. The corrosion behaviors were characterized by polarization, EIS and Mott-Schottky tests under a 3.5 wt.% sodium chloride aqueous solution open to air at room temperature. The Al0.32CrFeTi0.73Ni1.50 coating is a simple BCC single-phase solid solution structure compared with the corresponding poly-phase composite bulk. The structure of the Al0.32CrFeTi0.73Ni1.27Mo0.23 coating, combined with the introduction of the Mo element, means that the (Cr,Mo)-rich sigma phase precipitates out of the BCC solid solution matrix phase, thus forming Cr-depleted regions around the sigma phases. The solid solution of large atomic-size Mo element causes the lattice expansion of the BCC solid solution matrix phase. Micro-hole and micro-crack defects are formed on the surface of both coatings. The growth of both coatings’ passivation films is spontaneous. Both passivation films are stable and Cr2O3-rich, P-type, single-layer structures. The Al0.32CrFeTi0.73Ni1.50 coating has better corrosion resistance and much less pitting susceptibility than the corresponding bulk. The corrosion type of the Mo-free coating is mainly pitting, occurring in the coating’s surface defects. The Al0.32CrFeTi0.73Ni1.27Mo0.23 coating with the introduction of Mo element increases pitting susceptibility and deteriorates corrosion resistance compared with the Mo-free Al0.32CrFeTi0.73Ni1.50 coating. The corrosion type of the Mo-bearing coating is mainly pitting, occurring in the coating’s surface defects and Cr-depleted regions.

Effects of Tungsten Addition on the Microstructure and Properties of FeCoCrNiAl High-Entropy Alloy Coatings Fabricated via Laser Cladding.

This study examines the effects of different addition levels of tungsten (W) content on the microstructure, corrosion resistance, wear resistance, microhardness, and phase composition of coatings made from FeCoCrNiAl high-entropy alloy (HEA) using the laser cladding technique. Using a preset powder method, FeCoCrNiAlWx (where x represents the molar fraction of W, x = 0.0, 0.2, 0.4, 0.6, 0.8) HEA coatings were cladded onto the surface of 45 steel. The different cladding materials were tested for dry friction by using a reciprocating friction and wear testing machine. Subsequently, the detailed analysis of the microstructure, phase composition, corrosion resistance, wear traces, and hardness characteristics were carried out using a scanning electron microscope (SEM), X-ray diffractometer (XRD), electrochemical workstation, and microhardness tester. The results reveal that as the W content increases, the macro-morphology of the FeCoCrNiAlWx HEA cladding coating deteriorates; the microstructure of the FeCoCrNiAlWx HEA cladding coating, composed of μ phase and face-centered cubic solid solution, undergoes an evolution process from dendritic crystals to cellular crystals. Notably, with the increase in W content, the average microhardness of the cladding coating shows a significant upward trend, with FeCoCrNiAlW0.8 reaching an average hardness of 756.83 HV0.2, which is 2.97 times higher than the 45 steel substrate. At the same time, the friction coefficient of the cladding coating gradually decreases, indicating enhanced wear resistance. Specifically, the friction coefficients of FeCoCrNiAlW0.6 and FeCoCrNiAlW0.8 are similar, approximately 0.527. The friction and wear mechanisms are mainly adhesive and abrasive wear. In a 3.5 wt.% NaCl solution, the increase in W content results in a positive shift in the corrosion potential of the cladding coating. The FeCoCrNiAlW0.8 exhibits a corrosion potential approximately 403 mV higher than that of FeCoCrNiAl. The corrosion current density significantly decreases from 5.43 × 10-6 A/cm2 to 5.26 × 10-9 A/cm2, which suggests a significant enhancement in the corrosion resistance of the cladding coating.