Effect of Cu content on the tribological behavior of CuxCoCrMoNi high-entropy alloys
Ying Wang, Shuobin Chen, Jian Yu, Yuhua Peng, Pan Gong, Mao Zhang, Zhigang Hu, Bin Li
Abstract
In this study, Cu x CoCrMoNi high-entropy alloys with different Cu contents (x = 0, 0.3,0.6,0.9) were prepared by vacuum arc melting, and their tribological behaviors under 5–15 N load were systematically studied. XRD analysis shows that all the alloys are single FCC phase. SEM-EDS analysis showed that Cu element segregated in the interdendritic region (IR) to form Cu-rich FCC2 phase. Vickers hardness test shows that the hardness of Cu x CoCrMoNi HEAs with Cu is higher than that of CoCrMoNi alloy without Cu. Friction experiments show that the alloy's average friction coefficient decreased from 0.82 of Cu x CoCrMoNi (x = 0) to 0.56 of (x = 0.3). The wear rate decreased from 4.1 × 10 −4 mm 3 /(N·m) (x = 0) to 2.6 × 10 −4 mm 3 /(N·m) (x = 0.3). Then the increase of Cu content increases the average friction coefficient from 0.53 (x = 0.3) to 0.62 (x = 0.9). However, due to the lubrication of the oxide layer, the wear rate gradually decreased from 1.98 × 10 −4 mm 3 /(N·m) (x = 0.3) to 1.17 × 10 −4 mm 3 /(N·m) (x = 0.9). EDS analysis confirmed that the oxygen content on the worn surface increased significantly at high Cu content (x = 0.9) and high load (15 N), indicating that a lubricating oxide layer was formed and the alloy wear rate was reduced. With rising Cu content, the wear mechanism gradually changes from abrasive wear to oxidation wear. The oxide layer formed by the oxidation reaction during the friction process will hinder the wear of the HEAs and improve the alloy wear resistance.