Study of HVOF spraying of WC–CoCr using on-line particle monitoring

Tungsten carbide–cobalt based spray coatings are widely used in industry for applications requiring abrasion, sliding, fretting and erosion resistance. High velocity oxy-fuel (HVOF) flame spraying has been used for the production of high quality carbide coatings. In this study, a WC–CoCr powder was sprayed using the HVOF process. The spray parameters were varied to study their influence on the particle in-flight properties and the coating properties using on-line particle monitoring. It was found that the spray parameters such as the total gas flow rate, the spray distance and the powder feed rate could strongly influence the particle in-flight properties and the coating properties. In general, a trend existed that higher total gas flow rates, shorter spray distance and lower powder feed rates resulted in higher particle velocity and temperatures and denser and harder coatings.