Effect of the distribution of Cu on the tribo-corrosion mechanisms of CoCrFeNiCu0.3 high-entropy alloys

In the field of marine engineering, the application of Cu-containing antibacterial high-entropy alloys (HEAs) are inevitably subjected to the damage of both wear and corrosion. However, there is a lack of the fundamental understanding of the effect of Cu distribution on the tribo-corrosion mechanisms of alloys in marine environments. In this study, the working conditions of the alloy in a standard 3.5 wt.% NaCl solution were simulated to investigate the tribo-corrosion behaviour of CoCrFeNiCu0.3 HEAs with different distribution states of Cu. The focus was put on the effect of copper distribution on the tribo-corrosion mechanisms of the alloy. The research unveiled a correlation where the progressive dissolution of the copper element led to an elevation in the friction coefficient of the alloy, concomitantly resulting in a reduction in the wear rate. Alloys with the homogeneous distribution of copper exhibited optimal tribo-corrosion resistance. Furthermore, the transition of the copper distribution from segregation to homogeneity led to a shift in the tribo-corrosion mechanisms of the CoCrFeNiCu0.3 alloy from abrasive and corrosive wear to mild abrasive and oxidative wear. Moreover, the results demonstrated that by dissolving the Cu-rich phase and ensuring a homogeneous distribution of copper within the sintered alloy, the formation of corrosive microcouples and the detachment of oxidized debris were effectively suppressed. This promoted the formation of a protective chromium oxide layer in the groove region. The distribution optimization of copper towards homogeneity during the sintering process effectively enhanced the tribo-corrosion resistance of alloys. This work provides helpful guidance for material design and marine protection in the field of marine engineering.