Microstructure evolution and high temperature wear resistance of in-situ synthesized carbides reinforced NiCoFeCrSiMo high entropy alloy coatings fabricated by laser cladding

In this work, we reported a novel strengthening strategy of NiCoFeCrSiMo high entropy alloy by high density in-situ synthesized carbides. The external WC particles were introduced into the laser molten pool and basically dissolved which facilitate the in-situ reactions of carbides. The microstructure of composite coatings consists of high-density carbides which formed dendrites, while the FCC based solid solution matrix of high entropy alloy filled the inter-dendritic zone. The original added WC particles were almost dissolved in the laser pool and M6C type carbides or M2C carbides were in-situ synthesized. The composite coating was strengthened by dislocation pinning and plugging effects. Notably, the average microhardness of the composite coating can reach as high as 947 HV, while the friction coefficient of high entropy alloy coatings with 50 % WC addition could be as lower as 0.2 at 600 °C. The wear surface morphology analysis shows that the wear mechanism of M6C/FCC composite coating was adhesive wear and abrasive wear. The results in this work may provide some new thoughts for the design of ceramic particles reinforced HEA composite coatings.