Adding WC Nano-particles to Nickel-Based Coating Deposited by PTA Process: Microstructure and Nanoindentation Hardness Characteristics

The influence of the introduction of tungsten carbide nanocrystalline on the microstructure and mechanical characteristics of Ni-WC composite overlays on tool steel was studied. In addition to the improved fraction of retained WC phase and decreased fraction of brittle secondary carbide phases, the influence of the addition of tungsten carbide in nano-size on the microstructure, and mechanical behaviors of the deposited layer was considered. Tungsten carbide nanoparticle in the range 1-7 wt.% was added to existing commercial powder and deposition was carried out. The optimum welding parameters were determined. The results showed that the Ni-WC overlays possessed microstructures including gamma-Ni dendrites, with interdendritic Ni-Fe-based eutectics, borides (Fe-Cr)2B, and carbides (Fe, Cr)7C3. With the introduction of WC-nanocrystalline, refining the microstructure was achieved and the dissolution of WC particles enhanced the generation and growth of secondary carbide phases. The strengthening contribution of the reinforcing particles in alloy with 3 wt.% causes an increase in hardness, while the hardness values decrease as the content of WC increases by 7 wt.%.