Evaluation and mechanisms on heat damage of WC particles in Ni60/WC composite coatings by laser induction hybrid cladding

The evaluation and mechanisms on the heat damage of WC particles in Ni60/WC composite coatings produced by laser induction hybrid cladding (LIHC) were investigated. A semi-quantitative formula, R=4946×bM×η1−η×1−η2+0.45, was deduced to evaluate the heat damage degree of WC particles in Ni60/WC composite coatings according to the proposed trapping model. The results show that the heat damage degree of WC particles decreases as the laser scanning speed increases, whereas firstly increases as the content of WC particles increases then decreases. WC particles in Ni60/WC composite coatings produced by LIHC present the mechanisms of the dissolution-diffusion controlled heat damage, the collapsibility-dissolution-diffusion controlled heat damage and the dissolution-precipitation controlled heat damage, which of mechanism depends on the size of WC particles and the processing parameters. The first mechanism results in the formation of the alloyed reaction layer with a thickness of several micrometers around WC particles. The second one results in the formation of alloying carbides. The third one leads to the precipitation of the different carbides with the different morphologies.