Study on the effect of Ni60 transition coating on microstructure and mechanical properties of Fe/WC composite coating by laser cladding

Abstract

Two coatings, i.e. a single Fe/WC cladding layer and a combination of a Fe/WC cladding layer and a Ni60 transition coating, were prepared on the surface of 60Si2Mn spring steel using the laser cladding technology. The effect of the Ni60 transition coating on the macromorphology, microstructure, element distribution, Vickers microhardness and tribological properties of the Fe/WC cladding layer was investigated. The experimental results show that the added Ni60 transition coating reduces the possibility of generating pores and cracks in the Fe/WC composite coating and promotes the upward elongation growth trend of columnar crystals, but has no significant effect on the solidification characteristics of the cladding layer. The solidification characteristics of both coatings consist of dendrites and interdendritic eutectics. In addition, the microstructure in the top and middle regions of the single Fe/WC composite coating mainly shows the distribution of snowflake-like equiaxed crystals, and columnar crystals dominate the bottom region. In terms of mechanical properties, the diffusion of the Ni element reduces the microhardness of the cladding layer and increases the average friction coefficient and wear volume of the Fe/WC composite coating, but these mechanical properties are still significantly enhanced compared with those of the matrix.