Corrosion and corrosive wear of AlCrFeCoNi and Co-free AlCrFeNi-Tix (x = 0–1.5) high-entropy alloys in 3.5 wt % NaCl and H2SO4 (pH = 3) solutions

The Co-free AlCrFeNi HEA has good application prospects for its simple duplex BCC phase structure and attractive mechanical properties. In this work, influences of Ti on corrosion and corrosive wear of AlCrFeNi alloy in salty and acidic solutions were investigated and compared with those of AlCrFeCoNi. Results showed that removing Co led to little influence on hardness but only a slight decrease in corrosion resistance. However, the corrosive wear resistance was significantly improved, which was attributed to improved ductility, which benefited the toughness, of the Co-free AlCrFeNi alloy. AlCrFeNiTi0.5 showed the lowest passivation current and its corrosion current density was only about one-third that of SS316. A strong correlation was found among the corrosive wear resistance, corrosion resistance, hardness and brittleness. Titanium can improve the anti-corrosive wear ability of AlCrFeNi alloy with increased hardness, higher corrosion resistance, and enhanced protectiveness of formed surface oxide film. However, as the Ti content exceeded a certain level, corrosive wear of Ti-containing alloys was accelerated by easy formation of crack and delamination in substrate which led to a negative effect on the corrosive wear resistance, although the alloys showed higher hardness.