Research on the microstructure and properties of iron based alloy coatings based on gradient transition

Abstract

An iron alloy coating with gradient transition was sprayed on F304 stainless steel substrate by plasma spraying method and with a gradient material obtained by the material performance simulation software, and the effect of gradient transition on the microstructure, hardness and wear resistance of the coating was analyzed by comparing with the non gradient transition coating. The results show that both the gradient coating and the non gradient coating have wavy layered structure and are formed by highly flattened deformed particles overlapping each other. Micro metallurgical bonding was observed between the coating particles, and oxides were observed between the coating and the substrate, between the flat particles and inside the flat layer. The coating microstructure includes austenite phase, ferrite phase and carbides. The surface hardness of the gradient coating and the non gradient transition coating are basically similar, but there are obvious steep drop steps between the section hardness of the non gradient coating and the substrate hardness, while the section hardness of the gradient coating and the substrate hardness change gently, and the section hardness of the gradient coating is slightly lower than that of the non gradient coating. The wear rate of gradient coating is similar to that of non gradient coating at 400 °C, but it is lower than that of non gradient transition coating at 350 °C. The reason for reducing hardness changes and improving wear resistance of the coating may be related to the improvement of the microstructure and plasticity of the coating by the gradient layer, but more research is needed.