Effects of spherical WC powders on the erosion behavior of WC-Ni hardfacing used for steel body drill bit

Abstract

Improving the erosion resistance of polycrystalline diamond compact (PDC) bit can prolong its service life. The influence of spherical WC powders on the erosion behavior of WC-Ni hardfacing used for steel body drill bit has not been reported. In this work, Ni-based hardfacing coatings reinforced with various content of spherical cast tungsten carbide (CTCS) and angular cast tungsten carbide (CTC-A) particles are fabricated by oxy-acetylene welding process. The erosion behavior of WC-Ni hardfacing used for steel body PDC drill bit is experimentally studied. Results show that, the coating's microstructure, microhardness, fracture toughness and corrosion resistance varies under different CTC-S content, which leads to the differences in erosion mechanisms. The erosion resistance of hardfacing coatings decreases first and then increases with the decrease in CTC-S content. Sample 1 with 60% CTC-S and 0% CTC-A has the best erosion resistance, while sample 3 with 30% CTC-S and 30% CTC-A has the worst erosion resistance. As CTC-S content decreases, the erosion wear mechanism of hardfacing coating transforms from brittle mechanism to ductile mechanism. At a high CTC-S content, hardfacing coatings present brittle erosion wear mechanisms, such as micro-fracture and precipitate removal. At a low CTC-S content, hardfacing coatings show ductile erosion wear mechanisms, such as plastic deformation and crater formation.