Fabrication of nickel composite coatings reinforced with TiC particles by laser cladding

Various weight ratios of TiC particulate nickel-based composite coatings were produced on carbon steel substrates by laser cladding. The experimental results showed that the coating was uniform, continuous and free of cracks when a CaF2 flux was used. Excellent bonding between the coating and the medium carbon steel substrate was ensured by the strong metallurgical interface. The microstructures of the coating were mainly composed of γ-Ni dendrites, M23C6, a small amount of CrB, and dispersed TiC particles. The morphologies of TiC particles changed from the globular, cluster to flower-like shape. The volume fraction of TiC particles and the microhardness gradually increased from the bottom to the top of the coating, and the volume fraction of TiC particles increased with increasing of volume fraction of Ti and C. The maximum microhardness of the coatings with 10, 15 and 20 wt.% (Ti+C) in the preplaced alloy powder was approximately HV0.2750, HV0.2850 and HV0.2920, respectively, which was much larger than that of the steel substrate, HV0.2240.