An investigation on the wear and corrosion resistance of AlCoCrFeNi high-entropy alloy coatings enhanced by Ti and Si

Ti and Si are commonly used elements in the design of high-entropy alloy (HEA) systems, and their targeted regulation has significant implications for HEA performance. The combined action mechanism of Ti and Si on HEA is worth exploring. Thus, this study examines the influence of Ti and Si, both individually and in combination, on the microstructural evolution, wear resistance, and corrosion resistance of AlCoCrFeNi HEA coatings. Results indicate that the inclusion of Ti and Si consistently maintains the BCC structure of the AlCoCrFeNi HEA coatings, with the exclusive addition of Ti resulting in the BCC2 phase. Concurrent doping of both elements leads to a coating comprising a BCC + Laves phase, characterized by a notably refined phase structure. The introduction of Ti and Si to varying extents enhances the microhardness and wear resistance of the coating. Optimal enhancement is observed when both are co-doped, resulting in a reduction in wear rate by approximately 25.3 % and 31.2 %, respectively, compared to individual doping of Ti and Si. The inclusion of Ti establishes a stable passive film on the coating, while subsequent addition of Si decreases the width of the passivation region without compromising its stability. Moreover, the reduction in phase size and weaker galvanic corrosion effect, observed in the co-doping of Ti and Si compared to Ti doping alone, lay the groundwork for superior corrosion resistance.