Microstructure characteristics and properties of in-situ formed TiC/Ni based alloy composite coating by laser cladding

Different weight ratio of nickel based alloy, titanium and graphite powders were mixed and then laser cladded onto carbon steel substrate to produce a surface metal matrix composite layer. The experimental results showed that the coating was uniform, continuous and free of cracks. An excellent bonding between the coating and the carbon steel substrate was ensured by the strong metallurgical interface. The microstructures of the coating were mainly composed of gamma-Ni dendrite, M23C6, a small amount of CrB, and dispersed TiC particles, and the in-situ generated TiCP/matrix interfaces were clean and free from deleterious surface reaction. The morphologies of TiC particles changed from the global, cluster to flower-like shape, the volume fraction of TiCP and the microhardness gradually increased from the bottom to the top of the coating layer, and the maximum microhardness of the coating was about HV(0.2)850, 3 times larger than that of steel substrate. The volume fraction of TiC particles increased with increasing of volume fraction of Ti and C too.