Current-carrying wear behavior of CoCrFeNiW_0.2 and CoCrFeNiW_0.2+3at%C high entropy alloys

High performance CoCrFeNiW_0.2 and CoCrFeNiW_0.2 + 3 at% C HEAs were prepared by vacuum arc melting, which are promising candidates for extreme environment applications. To study the current-carrying wear behavior of the two HEAs under different current conditions, a pin-on-ring test rig was custom-designed. The microstructures, hardness, wear properties and mechanisms of the HEAs were investigated. The results reveal that the HEAs exhibit outstanding wear resistance in the absence of current, as evidenced by the very low wear rates and the relatively smooth worn surfaces. With the increasing of current intensity, it simultaneously exacerbates the abrasive wear, adhesive wear, oxidative wear and arc erosion. The HEAs show the worst wear resistance due to the melt ejection and arc discharge at 10 A. However, when the current reaches 20 A, the elevated temperature promotes material transfer and the formation of dense and complete oxide film, which has lubricating and protective effect to separate the worn surfaces, resulting in the reduction of COFs and wear rates. The rupture and regeneration of oxide film play an opposite effect on sliding contact friction, and their competitive relationship dominates the wear resistance of the HEAs under the large current. The CoCrFeNiW_0.2 + 3 at% C HEA exhibits superior wear resistance than CoCrFeNiW_0.2 HEA under various conditions because the WC carbide is harder than μ phase particle and can impede plastic deformation of FCC matrix during tribological process more efficiently.