Microstructure and properties of laser cladding CoCrNi-based medium-entropy alloy enhanced by Nb

CoCrNiNb x ( x = 0, 0.15, 0.3, 0.45) medium-entropy alloy (MEA) coating was prepared on the surface of AISI 1045 steel by laser cladding to explore the influences of Nb addition on the microstructure, microhardness, friction, wear property, and corrosion resistance of the CoCrNi-based MEA. The coating microstructure consisted of single FCC phases when x = 0. CoCrNiNb x MEA showed an FCC-Laves duplex structure with Nb addition. The microhardness of CoCrNiNb x MEA increased with the increased Nb content. When x = 0.45, the coating had the highest average microhardness of 505.53 HV 0.5 , 2.86 times that of Nb 0 . The wear resistance of CoCrNiNb x MEA coating gradually increased with the increased Nb content. The average friction coefficient decreased from 0.774 to 0.598; the abrasion loss decreased from 0.0616 mm 3 to 0.00946 mm 3 . The main friction and wear mechanisms contained adhesion wear, abrasive wear, and oxidative wear. The corrosion resistance test of the coating in 3.5 wt% NaCl solution showed that Nb 0.45 had the highest self-corrosion potential of −0.440 V and the lowest self-corrosion current of 3.17E-08 A/cm 2 . The passivation film on the Nb 0.45 surface demonstrated superior stability, density, and exceptional overall corrosion resistance. Research results provide a reference for strengthening the performance of CoCrNi MEA coating by laser cladding.