Effect of Powder Characteristics on Properties of Warm-Sprayed WC-Co Coatings

In high-velocity oxy-fuel (HVOF) process of WC-Co coatings, the decomposition and decarburization of WC during deposition are responsible for their much lower toughness compared with a sintered bulk WDC-Co. In the previous study, Warm Spray (WS) process, which is capable to control flame temperature, was successfully applied in attempt to suppress such detrimental reactions by keeping particles’ temperature lower than their melting point. The coatings deposited by WS process showed no or little formation of W₂C and h phases and demonstrated the improved fracture properties. However, there is still a not negligible difference in fracture toughness between WS coatings and a bulk. In order to optimize the properties of the WS coatings, the effect of original powder characteristics were investigated. Microstructural characterization and phase analysis were carried out on deposited coatings by SEM and XRD. The results show that the feedstock powder size has substantial effects on the properties of the coatings and the smaller powder showed the improved properties.