Substructure of martensite in particle reinforced Fe-based composite coating by laser cladding

In-situ particle reinforced Fe-based composite coating was produced by laser cladding Fe-C-Si-B base powder containing Ti powder.The microstructure of the coating,especially the formation and transformation of martensite during laser processing,was investigated by scanning electron microscopy and transmission electron microscopy.The experimental results show that the coating has no pores or cracks and the microstructure is homogeneous,which consists of martensite,ledeburite,residual austenite and dispersed in-situ Ti carbide particles.The martensite is {211},113 twinned martensite.Nanometric carbides are precipitated from martensite due to the second tempering effect.They are demonstrated to be cementite and have an orientation relationship with martensite.