Research on Mechanical Properties and Corrosion Behavior of (Co34Fe8Cr29Ni8Si7)100−xBx High Entropy Alloy Coating

Abstract

CoCrFeNiSi high entropy alloy coatings doped with different boron (B) contents were prepared on titanium alloy substrate by laser cladding. The microstructure, friction behavior and corrosion resistance of the coatings were investigated, based on which the mechanism of improving the form ability of the laser cladding coatings with doped B element was observed in detail. It was revealed that oxide layer (B₂O₃) produced on the surface at high temperature had enhanced the form ability of the coating layer by significantly decreasing pores and cracks in the coatings. At the same time, the incorporation of B gave birth to the formation of boride, while the coatings were composed of CoB, CrB, Co₂B and amorphous phase. It was worth noting that the high entropy alloy coating exhibited the highest microhardness of up to 1189 HV_0.2 and optimum wear resistance as the B content approached 6 wt.%. Furthermore, lower corrosion current density, or better corrosion resistance in other words, was presented by the high entropy alloy coating containing doped B element, which was mainly due to that the improved microstructure of the coatings with fewer pores or cracks had effectively hindered the penetration of chloride ions and formed an effective barrier between the substrate and the corrosion solution.