Microstructure and properties of in situ synthesized TiB2+WC reinforced composite coatings

Nickel-based composite coatings reinforced by in situ synthesized TiB2 and WC particles were deposited on stainless steel by laser cladding, and their microstructure and mechanical properties were investigated. The results show that the coatings are mainly composed of gamma-Ni cellular dendrites and dispersed spherical/strip/network shaped TiB2 and equiaxial WC particles. The initial WC particles are dissolved to become fine and mostly dispersed within gamma-Ni cellular dendrites. The coating prepared at a special laser energy of 0.225 kJ.mm(-2) is uniform, continuous, and free of pores and cracks. With the decrease in special energy density, TiB2 phase changes from fine spherical particles which cluster together to strip shape with different morphologies and further crystallizes to form network structure, and the dispersion zone also gradually changes from intragranular to intergranular phase. The coating possesses a higher microhardness compared with the substrate, and it has a good metallurgical bond with the substrate and excellent cracking resistance.