Dissolution and precipitation of TiC particles and their distribution in a laser clad 30vol.-%TiC_p/Ni-alloy composite coating

A 30vol%TiCp/Ni-alloy composite material was clad on steel 1045 using a 2 kW laser. The clad layer of the coating presents TiC particles, primary γ-Ni dendrites and the eutectics of γ-Ni +(Cr, Fe)23C6 in the interdendritic regions. Depending mainly on their sizes. TiC particles can not only be trapped by the advancing solid/liquid interface and thus distribute within the γ-Ni dendrites, but also be pushed away by the interface into the interdendritic regions together with the eutectics. The morphology of TiC particles are closely related to their dissolution and precipitation behavior during laser cladding. The growing mechanism of TiC particles are as follows: (1) radiated or stepped lateral growth at the edges of original particles; (2) bridging growth of the particles in cluster; (3) faceted growth of newly independently nucleated TiC particles in the liquid phase and (4) precipitation of TiC in γ-Ni extended solid solution.