The Influence of Spraying Angle on Properties of HVOF Sprayed Hardmetal Coatings

The spraying angle is one of the deposition parameters that influence the quality of thermally sprayed coatings. In theory, decreasing the spraying angle results in lower process deposition efficiency, whereas the porosity of coatings increases, becoming a cause of poorer microstructure and mechanical properties. In this study, the dependence of microstructure together with the basic mechanical properties and wear of WC-Co and Cr3C2-NiCr high-velocity oxyfuel (HVOF) sprayed coatings on the spraying angle was investigated. For each coating, the maximum spraying angle was determined that can be used without significantly decreasing coating quality. Based on the changes in properties of coatings and requirements for the process deposition efficiency, a maximum 30A degrees diversion from the normal spray direction is recommended for WC-Co and 15A degrees diversion for Cr3C2-NiCr coatings.