Study on tribological oxide mechanism of CoCrFeNiMo high entropy alloy

The oxide film can improve the tribological properties of high entropy alloy, but its formation needs further study. In this work, the tribological oxide mechanism of CoCrFeNiMo high entropy alloys was investigated by means of experiments and finite element simulation. Simulation results reveal that the formation and destruction of oxide film are related to contact stress, von Mises stress and tensile stress. The contact stress destroys the passivation film of CoCrFeNiMo high entropy alloy. Then von Mises stress causes plastic deformation on the surface to form oxide films. Finally, tensile stress causes these oxide films to crack. These results were confirmed by the experiment. When CoCrFeNiMo rubs with ZrO2, the increase of load can make the CoCrFeNiMo surface prone to plastic deformation, forming more oxide films. However, when it sildes against stainless steel no oxide film is formed on the surface of CoCrFeNiMo because there is no plastic deformation. Cracks in the oxide film perpendicular to the tensile stress were also observed on the surface, proving the destruction of periodic tensile stress.