Influence of spray parameters on the particle in-flight properties and the properties of HVOF coating of WC-CoCr

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 producing high quality carbide coatings. In this study, a WC-CoCr powder was sprayed using a 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. The wear behavior of the coatings was evaluated both by rubber wheel tests and by pin-on-disk tests. It was found that the total gas flow rate and the powder feed rate could strongly influence the particle in-flight properties under the spray conditions in the study. By contrast, the spray distance had less influence than the above two parameters. In general, the higher the total gas flow rate, the lower the powder feed rate and the shorter the spray distance, the higher the particle velocity and temperature, and the denser and harder the coating. The rubber wheel tests showed that the total gas flow rate was of large significance for the wear resistance of the coatings.