Fretting wear resistance at ambient and elevated temperatures of 316 stainless steel improved by laser cladding with Co-based alloy/WC/CaF2 composite coating

The coating fabricated by laser cladding on the surface has been an effective way to strengthen and enhance the wear resistance of alloys. However, the traditional Co-based alloy coatings rarely pay attention to the addition of self-lubrication constituents to form the composite coating. In addition, the effects of the Co-based composite coating on fretting wear resistance were few addressed. In this study, a Co-based alloy/WC/CaF2 composite coating was fabricated by laser cladding on the surface of 316 stainless steel to improve the surface hardness and self-lubrication performance. The microstructure, phase constituents and fretting wear resistance at both room temperature (RT) and 500 degrees C were investigated. Results confirm that the composite coating is consisting of alpha-Co, Cr23C6 and WC phases. And the F element is effectively dissolved into the alpha-Co phase. The fabricated composite coating is dense and uniform. The microhardness of the composite coating can reach to 600 HV0.2 due to the presence of WC and Cr23C6 phase. In addition, the grain refinement is another reason resulting in the higher microhardness. Fretting tests demonstrate that the fretting wear resistance at both RT and 500 degrees C are signifi-cantly improved by the composite coating, which can lead to the decrease of the COF and the wear loss. The lower COF can be ascribed to the dissolved F element in alpha-Co phase, especially at high fretting temperature. Additionally, the composite coating can effectively prevent the oxidation during fretting both at RT and 500 degrees C. This work provides an excellent method for the metallic materials to improve fretting wear resistance at both RT and high temperature.

Automated summary

The laser-cladded Co-based alloy/WC/CaF2 composite coating improved the surface hardness and self-lubrication performance of 316 stainless steel, leading to enhanced fretting wear resistance at room temperature and 500 degrees C. The coating consists of alpha-Co, Cr23C6, and WC phases, with a microhardness of 600 HV0.2. In addition, the composite coating effectively prevents oxidation and reduces the coefficient of friction (COF) and wear loss at high fretting temperature.