Effect of Ti content on high-temperature wear resistance and oxidation resistance of AlCoCrNi alloy

Ductile iron offers advantages such as high strength, good toughness, and low casting and machining costs. However, its service life and application range are limited by factors including susceptibility to oxidation at high temperatures and inadequate tribological performance. In this study, AlCoCrNiTi_x (x = 0, 0.2, 0.4, 0.6, molar ratio) high-entropy alloy coatings were fabricated on ductile iron using laser cladding technology, and their wear resistance and oxidation resistance at elevated temperatures were investigated. The results show that Ti doping promotes the in-situ formation of new phases TiC and Ni₃Ti in the AlCoCrNi alloy. With increasing Ti content, the microhardness of the coatings gradually increases due to dispersion strengthening and solid solution strengthening, reaching a maximum value of 703.2 HV_0.5 for Ti0.6, which is approximately 2.83 times that of ductile iron. The Ti0.4 coating exhibits the best tribological performance, where the formation of a dense lubricating phase at high temperature effectively reduce interfacial friction and wear, resulting in a friction coefficient of 0.298—43.45% lower than that of the substrate. The Ti0.2 coating shows the best oxidation resistance, with an oxidation rate constant of 0.8724 mg²⋅cm⁻⁴⋅h⁻¹. The composite oxide layer composed mainly of Al₂O₃、TiO₂ and Cr₂O₃ effectively suppresses inward oxygen diffusion.