Microstructure and wear behavior of laser cladding FeCoCrNiMo coating with gradient transition entropy interlayer

The CoCrNi-FeCoCrNi-FeCoCrNiMo gradient high entropy alloy (GHEA) coatings with good metallurgical properties have been successfully prepared on 316 stainless steel by laser cladding (LC). The microstructure, element distribution, microhardness and wear behavior of HEA coating were investigated by SEM, EDS, hardness test and wear test, respectively. The results show that the design of the entropy-varying gradient structure improves the bonding quality of the 316 stainless steel and the FeCoCrNiMo coating. The phase compositions of FeCoCrNiMo HEA coating and CoCrNi-FeCoCrNi-FeCoCrNiMo GHEA coating contain face-centered cubic (FCC) and σ phases. The surface microstructure of the CoCrNi-FeCoCrNi-FeCoCrNiMo GHEA coating is much finer than FeCoCrNiMo HEA coating. The microhardness and wear resistance of the CoCrNi-FeCoCrNi-FeCoCrNiMo GHEA coatings are significantly improved compared to the FeCoCrNiMo HEA coatings directly deposited on the 316 stainless steel. The CoCrNi-FeCoCrNi-FeCoCrNiMo GHEA coatings have high hardness of 840HV. Moreover, the results show that the shift in the wear mechanism is evident within the GHEA coatings, from more severe oxidized wear, adhesive wear and slight deformation to abrasive wear, which can significantly reduce the wear rate of the HEA coatings in friction process.