Influence of tungsten carbide raw materials to microstructure and wear performance on PTA hard-facing materials with its micro-mechanism analysis

The wear performance of the plasma transferred arc (PTA) welding hard-facing materials manufactured reinforced by cast WC/W2C and coarse grain WC with different shapes are investigated. Coarse grain WC-Ni coating shows the best wear resistance in a high applied load condition, with spherical reinforced particles give higher wear performance than angular shape. WC, W2C, γ-Ni, M23C6, and M7C3 (M = Cr, Fe, W, and Ni) are detected in PTA coatings. The spherical cast and angular cast WC/W2C particles contain a higher volume of W2C, which is easier to be dissolved during the PTA welding process, resulting in lower retained reinforced particle volume and more precipitates concentration. In the PTA coating, the cast WC/W2C particles have a higher hardness, whereas the matrix has a relatively low hardness. The wear performance of PTA coating is more affected by the hardness rather than the coefficient of friction (COF). At a load of 5 N applied on the Si3N4 ball, the contact area between reinforced particles and counterparts, resulting in wear resistance is controlled by the hardness of the reinforced particles. When the load increases to 10 N, the hardness of the matrix controls wear performance. The precipitates formed between the carbides and matrix smooth the interface and strengthen the bonding, which prevents the cast WC/W2C from being pulled out from the matrix during the wear test.