Tribological and electrochemical behaviors of FeCoNiCrMox HEA coatings prepared by internal laser cladding on 316L steel tube

In order to improve the performance of the inner wall of the 316L hydraulic cylinder, FeCoNiCrMox (x = 0.2, 0.4, 0.6) high entropy alloy coatings were prepared by laser cladding. The effects of the Mo element on the phase, microstructure, hardness, and tribological as well as electrochemical behaviors of the coating were investigated. The results show that the coatings consist of the FCC phase. The FCC phase increases, and the grain orientation becomes more complex with increased Mo element content. The coatings are mainly composed of columnar and equiaxial crystals. Mo0.4 coating has the finest grain structure, resulting in the coating with a maximum hardness of 421.99 HV, 2.11 times that of the substrate. The nanoindentation test shows that the elastic modulus of the HEA coating increases with the increase of Mo content. The dry sliding wear test shows that adding the Mo element improves the wear performance of the coating. The wear volume loss and wear rate of Mo0.4 coating were the lowest, 12.242 mg and 2.88 × 10−4 mm3•N−1•m−1, respectively. In the 3.5 wt% NaCl solution, the polarization curves and EIS results indicated that adding the Mo element improved the corrosion resistance of the coating. The FeCoNiCrMox coatings significantly improved the hardness, tribological, and electrochemical behaviors of the 316L substrate.