Effect of WC Content on Microstructure and Corrosion Resistance of Laser Cladding CoCrFeNiTi High-Entropy Alloy Coating

To prolong the life of the desulfurization slurry circulating pump impeller, WC-reinforced CoCrFeNiTi-WCx (x=0, 5, 10, 15, 20, wt%) high-entropy alloy (HEA) coatings were fabricated on the base material 30CrMnSiA steel surface of desulfurization slurry circulating pump impeller by laser cladding. The effects of WC content on the microstructure, phase composition, element distribution, microhardness, wear resistance, and corrosion resistance of the coatings were studied. It is found that the phase composition of CoCrFeNiTi HEA coating is fcc (Fe-Ni), bcc (Fe-Cr), Laves (CoTi2), and AB-type (compounds of Ti) phases. With the increase in WC content, the diffraction peak intensity of Laves phase increases, and new phases carbides (WC, TiC, Cr7C3, and Fe3C) are formed. The microstructure of CoCrFeNiTi HEA coating is mainly composed of cellular crystals at the bottom and equiaxed dendrites at the top. With the increase in WC content, the coating microstructure is mainly equiaxed dendrites, and the grain size gradually refines. The addition of WC improves the properties of the CoCrFeNiTi-20% coatings, including the largest microhardness (HV0.2) of 6419 MPa and the smallest coefficient of friction (0.664) and wear rate (1.3x10(2) mu m(3)center dot(s center dot N)(-1)), and the best wear resistance. Meantime the wear mechanism is mainly slight adhesive wear and abrasive wear. In addition, with the increase in WC content, the coating shows lower corrosion rate and corrosion current. Among all the coatings, CoCrFeNiTi-20%WC coating has the smallest corrosion current and the best corrosion resistance.