Wear Resistance Of High-entropy Alloy Research Articles

Nanotribological behaviors of high-entropy alloys CoCrFeMnNi and medium-entropy alloys Ni0.4Al0.3Co0.3, Ni0.4Cr0.3Fe0.3 under different conditions: A molecular dynamics study

High-entropy alloys (HEAs) and medium-entropy alloys (MEAs) have great potential for practical engineering applications in aerospace, rail transit, oil and gas equipment and other key fields due to their excellent physical and mechanical properties. However, there are relatively few studies on the wear resistance and mechanism of high-entropy alloys and medium-entropy alloys. In this paper, based on molecular dynamics (MD) simulation, the friction and wear behavior and influence mechanism of CoCrFeMnNi (HEA), Ni0.4Al0.3Co0.3, and Ni0.4Cr0.3Fe0.3 (MEAs) under different conditions were compared. Interestingly, the results show that the Ni0.4Cr0.3Fe0.3 alloys exhibits the lowest coefficient of friction and lowest wear under the same friction conditions. The CoCrFeMnNi alloy demonstrates relatively good wear resistance at higher velocities and deeper penetration depths due to its HCP phase structure and the "V"-shaped shear bands that help dissipate stress and shear strain during the friction process. In addition, further research found that the proportion of Ni element is one of the key factors to determine the wear resistance of high-entropy alloy CoCrFeMnNi. As the growth of the proportion of Ni element, the accumulation height and CSP value in the alloy will gradually decrease, and eventually lead to the enhancement of the wear resistance of high-entropy alloy CoCrFeMnNi.

Microstructure and properties of CoCrFeNiAlxMo2-x high-entropy alloy coating by laser cladding

CoCrFeNiAlxMo2-x (x = 0, 0.5, 1, 1.5, and 2) high-entropy alloy coatings were applied to Q235 steel, and this study investigated the effect of x variations on microstructure evolution and properties. It was fount that as x increased, the crystal structure of the coatings transitioned from a face-centred cubic (FCC) + body-centred cubic (BCC) + σ + B2 phase to a BCC + σ + B2 phase, and eventually it become a BCC phase. Concurrently, the microhardness, wear resistance, corrosion resistance, and high-temperature oxidation resistance of the coatings initially increased and then decreased with the rise in x. The optimal values were achieved at x = 1. The enhancement in microhardness and wear resistance of high-entropy alloy (HEA) coatings was attributed to the change of phase type, dispersion strengthening and solid solution strengthening. Adding of the Al element generated a passivation film on the coatings’ surface, which mitigated galvanic corrosion. Furthermore, an appropriate amount of Mo increased the thickness and density of the passivation film, thereby improving its corrosion resistance. During early-stage high-temperature oxidation, the Al underwent element undergoes rapid oxidation, while Mo promoted the formation of Al2O3, leading to an excellent high-temperature oxidation resistance. Additionally, mathematical model equations were used to fit the results, adding insights into the effects of Al and Mo content changes (x value) on the wear resistance, corrosion resistance, and high-temperature oxidation resistance of the coatings.

Microstructure and Properties of FeCrMnxAlCu High-Entropy Alloys and Coatings

FeCrMnxAlCu (x = 0.5, 1, 1.5, and 2) high-entropy alloys (HEA) and coatings were prepared through vacuum arc melting and cold spray-assisted induction remelting processes. This study investigated the effect of different Mn contents on the microstructure and wear resistance of HEAs and coatings. The results showed that the high-entropy FeCrMnxAlCu alloy prepared through vacuum arc melting and cold spray-assisted induction remelting processes comprised simple body-centered cubic and face-centered cubic phases with dendritic + interdendrite structures. The coating of the prepared alloys exhibited superior performance compared with the cast alloy. In addition, the hardness of the FeCrMnxAlCu HEA coatings synthesized through induction remelting was 1.4 times higher than that of the cast FeCrMnxAlCu HEA. Moreover, the wear rate of induction-remelted produced HEA coating was reduced by 24% compared with that of vacuum arc-melted produced HEA. The hardness of the induction-remelted produced FeCrMnxAlCu HEA coating initially increased and then decreased with increasing Mn contents. At x = 1, the hardness of FeCrMnAlCu HEA coating reached a maximum value of 586 HV, with a wear rate of 2.95 × 10−5 mm3/(N·m). The main wear mechanisms observed in the FeCrMnxAlCu HEA coatings were adhesive, abrasive, and oxidative.

Dry sliding wear and friction behavior of powder metallurgy FeCoNiAlSi0.2 high-entropy alloys

Wear behaviors of the FeCoNiAlSi0.2 high-entropy alloy (HEA) and Si-free FeCoNiAl during the reciprocating sliding wear process were evaluated for automotive piston rings. The HEAs were prepared using on advanced powder metallurgy route to solve the inherent shrinkage porosity and segregation defects during casting, poor densification, and wear resistance of HEAs while reciprocating motion. The morphology, hardness, wear, and friction properties were investigated. FeCoNiAl had biphasic face-centered cubic (FCC) and body-centered cubic (BCC) solid solution structures, whereas FeCoNiAlSi0.2 HEAs had a single BCC solid solution structure. Si addition significantly enhanced the hardness and wear resistance of the HEAs under reciprocating conditions because of the increased solid solution strengthening and lattice distortion effects. The maximum hardness of the FeCoNiAlSi0.2 HEA reached approximately 582 HV, which is higher than that of the equiatomic FeCoNiAl HEA (491 HV). The findings depict that FeCoNiAlSi0.2 maintains better tribological behavior than FeCoNiAl HEA against the tungsten carbide (WC) ball indenter. Oxidative delamination and cracking occurred in the FeCoNiAl/WC pair, whereas a mixed adhesive–abrasive wear mechanism was prominent in the FeCoNiAlSi0.2/WC pair because of the harder BCC solid solution phase. This study explores an effective strategy for enhancing the tribology behavior of automotive piston structures under varying loads and reciprocating dry sliding motions.

Tribological behavior of boronized Fe40Mn20Cr20Ni20 high-entropy alloys in high temperature

Boronization can improve the wear resistance of high-entropy alloys (HEAs). However, the tribological tests on boronized HEAs were generally carried out at room temperature. In fact, materials are often applied in high temperature. Therefore, it is essential to investigate the effect of boronization on the tribological properties and mechanism of HEAs in high temperature. In present work, the hot-rolled Fe40Mn20Cr20Ni20 HEAs were boronized by the pack cementation method at 900 °C for 6 h. The tribological tests of the alloys before and after boronization were conducted in 20–600 °C. The results showed that the boronized alloys showed higher wear resistance at 20–600 °C, whose average coefficients of friction and wear rate were lower than those of hot-rolled alloys. At 20–200 °C, the main wear mechanisms of the hot-rolled alloys were abrasive and adhesive wears; while the main wear mechanism of the boronized alloys was polishing effect. At 300–600 °C, the main wear mechanisms of the alloys before and after boronization were oxidation and abrasive wear. The wear rate was reduced by the B2O3 produced on the surface of the boronized layer during wear and the good thermal stability of the boronized layer, which indicated that boronization improved the wear resistance of HEAs in high temperature.

A Study on Outstanding High‐Temperature Wear Resistance of High‐Entropy Alloys

Wear property is a main reason for failure, especially for those parts which are mechanically moving and interacting with each other in industrial utilization. High‐entropy alloys (HEAs) are considered promising candidates to possess outstanding tribological factors of performance at high temperatures compared with conventional engineering alloys, which have drawn much attention from academic and industrial points of view. This study is performed to survey the influence of microstructure, grain size, precipitation, reinforcement, and elements addition on the wear resistance of HEAs over a wide temperature range. In this respect, the worn microstructure, wear rate, friction coefficient, hardness, wear track, and subsurface are precisely checked. This review also explores the high‐temperature wear resistance of thermally sprayed and additively manufactured HEAs associated with emphasizing the dominant wear mechanisms through in a wide range of temperatures.

Using C to enhance the wear resistance of AlCrFe2Ni4Ti2 high-entropy alloy via replacing brittle phases by in-situ formed TiC in a matrix with improved ductility

The wear resistance of high-entropy alloy (HEA), AlCrFe2Ni4Ti, can be enhanced by increasing the Ti content, which raises the hardness of the alloy due to the formation of harder phases, including an L21 phase with disordered-BCC nano-precipitates, a η-Ni3Ti hexagonal phase, and a MgZn2-type Fe2Ti Laves phase. However, these hard but relatively brittle phases have negative influences on the wear resistance of the alloy if their amount exceeds a certain level, especially when large impact forces or large fluctuations in wearing force are involved. In this work, we added carbon to AlCrFe2Ni4Ti2 to reduce the Ti-containing brittle phases and form in situ TiC particles in the metallic matrix with improved ductility. Samples of AlCrFe2Ni4Ti2CX (x = 0, 0.5 and 1.0, in molar ratio) were fabricated by arc melting. The fabricated HEA-matrix with in situ TiC particles showed improved ductility, e.g., the compressive ductility was increased by up to 30%, along with increased ultimate compressive strength, although the yield strength was slightly decreased, compared with the alloy without carbon addition. Wear tests demonstrated that the HEA with in situ TiC particles showed consequently enhanced wear resistance (10%–19% higher). This study demonstrates an effective approach to modify the high-entropy alloy for enhanced wear resistance by eliminating or minimizing Ti-containing brittle phases using carbon to react with Ti, forming in situ TiC particles in a HEA matrix with improved ductility.

Influence of laser power on microstructure evolution and properties of laser cladded FeNiCoCrMo HEA coatings

The present study is to investigate the effect of laser on the microstructure evolution, wear and corrosion resistance of FeNiCoCrMo high entropy alloy (HEA) coatings, which were prepared on 304 stainless steel by laser cladding technology. The results showed that the HEA coatings were mainly composed of face-centered cubic (FCC) solid solution structure (Ni-Cr-Co-Mo) and rhombohedral structure (Fe3Mo and CoMo2Ni). The laser power will directly affect the content and distribution of each phase. With the increase of laser power, the content of Ni-Cr-Co-Mo phase decreases, the contents of Fe3Mo phase and CoMo2Ni phase increase obviously, and the Mo phase gradually decreases to disappear. When the laser power is 1200 W, there is a relatively clear boundary between the eutectic structure and the strengthening phase in the microstructure, but when the laser power is 1800 W, the eutectic structure and the strengthening phase have infiltrated each other, and the phases are in a chaotic state. The wear resistance of HEA is better at low laser power, and the corrosion resistance of HEA is better at high laser power. The wear and corrosion mechanisms for different samples were discussed. This work is helpful to understand the existing state of Mo element in FeNiCoCrMo coating and the influence of phase composition and distribution on the wear resistance and corrosion resistance of the coating.

Coatings from high-entropy alloys: State and prospects

The authors made a brief review of recent publications by foreign and domestic researchers on the structure, phase composition, and properties of films and coatings of five-component high-entropy alloys (HEA) on various substrates and modification of the HEA surface by various types of processing. The main methods of applying films and coatings are considered: magnetron sputtering, thermal sputtering, laser sputtering, and electrodeposition. Particular attention is paid to the deposition of coatings on stainless steels and titanium alloys. The positive change in the tribological, strength properties, and corrosion resistance of film coatings in a wide temperature range is analyzed and possible causes of the observed effects are discussed. The role of solid solution strengthening, formation of fine-grained structure, and the formation of oxide layers enriched with one of the HEA components were taken into account. The authors identified new methods for applying coatings from HEA and subsequent processing. Using Nb and Ti doping as an example, their role in increasing microhardness, wear resistance, and reducing the friction coefficient in coatings were revealed. Electrolytic polishing, electroerosive machining, mechanical polishing and their combination are considered among the methods of HEA surface treatment. A number of works propose a method of powder borating to increase the surface strength and wear resistance of HEAs. The paper considers analysis of works on electron-beam processing as one of the promising and high efficient methods of HEA surface hardening.

Microstructures and Wear Resistance of CoCrFeNi2V0.5Tix High-Entropy Alloy Coatings Prepared by Laser Cladding

CoCrFeNi2V0.5Tix high entropy alloy coatings were synthesized by laser cladding on Ti-6Al-4V (annotated as TC4) substrate. The microstructures, hardness, and wear properties of the coatings were studied in detail. The results showed that these coatings were all composed of body-centered cubic (BCC) solid solution, (Co,Ni)Ti2 phase, and Ti-rich phase. With the increase of Ti content (x in the range of 0–1.0), the hardness of these coatings (about 960 HV) was basically unchanged and stabilized, whereas, when x was increased to 1.25, the correspondent hardness was decreased significantly to about 830 HV. Compared with original substrate, the wear resistance of high-entropy alloy (HEA) coatings was greatly improved. In particular, CoCrFeNi2V0.5Ti0.75 (donated as Ti0.75) exhibited the lowest wear rate, width, and depth of tracks of wear, indicating the best wear resistance. Moreover, the wear mechanisms of Ti0.75 coating were mainly adhesive wear and oxidative wear.

Wear Resistance of High-Entropy Alloys

The tribotechnical properties of high-entropy alloys in pair with 65G steel in air under dry sliding friction conditions are investigated in comparison with wear-resistant steel and powder materials. The sliding friction rate was 6, 8, and 12 m/sec and the pressure was 0.5 and 1.0 MPa. It is determined that the wear intensity of high-entropy alloys at the sliding friction rate 5–10 m/sec under 0.5 and 1.0 MPa loads ranges from 6.1 · 10–10 g/km to 1.6 · 10–9 g/km for the samples and from 5.5 · 10–8 g/km to 1.1 · 10–8 g/km for the counterface. It is established that, when friction, the shear deformations promote the formation of thermally stable nanostructures with grains 30–70 nm in size in the surface layer of the secondary structures. It is shown that the formation of nanostructures is accompanied with 20–30% increase in hardness for both high-entropy alloys and counterface material. It is established that, when friction, high temperatures at the contact points promote the formation of ordered β-phase with BCC lattice on the friction surface of the Fe25Cr20Ni20 Mn15Co10Al10 high-entropy alloy.

Wear behavior of high entropy alloys containing soft dispersoids (Pb, Bi)

Intrinsic high entropy alloys (HEAs) exhibit superior mechanical properties (hardness, strength, ductility, toughness etc.) and hence, they are considered as potential candidates for wear resistance applications. Wear resistance of HEAs can further be improved by engineering microstructure using various novel design concepts. One of such concepts involves the usages of soft dispersoids (Sn, Pb, Bi, Sb etc.) in the HEA matrix. However, the challenge is to engineer the novel microstructure consisting of soft dispersoids, dispersed uniformly in the HEA matrix, using suitable processing techniques. In this connection, the present work reports the effect of soft dispersoids, such as Pb and Bi on the wear behavior in equiatomic CuCrFeTiZn and AlCrFeMnV HEAs. The alloys containing Pb and Bi were synthesized using mechanical alloying (MA) followed by spark plasma sintering (SPS) in inert argon atmosphere. Phases and microstructure of milled powder and sintered alloys were investigated using XRD, SEM equipped with EDS. Sliding wear tests were also carried out for all the sintered samples at 2N, 5N, 7N and 10N load for various sliding speeds. Wear results indicate coefficient of friction (COF) does not vary much with varying the Pb concentration in HEAs. However, wear rate decreases significantly with increasing the Pb content in the alloys. For HEAs containing Bi, there is considerable decrease in the COF as well as in the wear rate even for a lower (5%) Bi content. Increasing load does not cause any change in the COF in both cases. However, wear rate decreases substantially due to increase of load. In addition, SEM analysis of the worn surface and wear debris were performed and it has been found that oxidative wear is the dominant wear mechanism in these systems. However wear tracks indicate the presence of abrasive wear. Analysis of Raman spectroscopy of wear debris confirms the presence of Fe2O3, Bi2O3 and PbO.