Tribo-induced microstructural evolutions and wear mechanisms of AlCoCrFeNi2.1 eutectic high-entropy alloy at elevated temperatures

Abstract

The tribological behaviors and wear mechanisms of the AlCoCrFeNi_2.1 eutectic high-entropy alloy (EHEA) were investigated in the broad temperature range 25 – 800 °C. The AlCoCrFeNi_2.1 EHEA exhibits a very low wear rate at 25 °C, owing to the formation of the composite type oxidation layer consisting of nanocrystals embedded in amorphous matrix. The EHEA exhibits decreasing trends for COF and stable wear rates with increasing temperature. The synergistic effect of oxidation and plastic deformation causes the formation and thickening of oxidation layer which is beneficial to wear resistance at 400 °C. At 800 °C, the high temperature enhances atomic diffusion, thus the amorphous oxide layer undergoes partial crystallization to form nano and ultrafine grains. Both the newly formed nanograins and ultrafine grains are thermally stable, and possess high hardness which can improve anti-wear performance of the alloy. This work gets insights into developing new wear-resistant alloys that is applicable in a broad temperature range, by revealing the tribo-induced surface deformation mechanisms.