Phase evolution, microstructure, microhardness and corrosion performance of CoCrFeNiNbx high entropy alloy coatings on 316 stainless steel fabricated by laser cladding

FeNiCoCrNbx (x. molar ratio, x = 0, 0.1, 0.2, 0.3) high entropy alloy coatings (HEACs) were fabricated on 316 stainless steel (SS) by laser cladding (LC). Experimental results showed that the addition of Nb increased the lattice constant of FeNiCoCrNb high entropy alloy system. HEAC exhibited the transformation from columnar crystal at the interface to equiaxed crystal at the surface on the cross-sectional plane because of the change in the temperature gradient (G) and solidification rate (R). When x = 0.3, lamellar Laves phases appeared in ID. The microhardness of the four HEACs was 1.78, 2.19, 2.30 and 2.37 times that of 316 SS. The HEAC with x = 0.3 as well as 316 SS exhibited typical p-type semiconductor characteristics, which showed excellent corrosion resistance as indicated by the lowest I-corr of 2.46 x 10(-9) A cm(-2) and a larger passivation region with 2 times that of 316 SS.