Effect of heat-treatment of spray-dried powder on properties of ultrafine-structured WC–Co coating

The ultrafine WC–Co composite powder was firstly synthesized by in situ reactions, and was then spray-dried and heat-treated to prepare the feedstock powder for the high velocity oxy-fuel thermal spraying. The effects of the heat-treatment of the spray-dried powder on the properties of the final ultrafine-structured WC–Co coating were studied in detail. The results show that increasing the heating temperature leads to a significant increase in the density and the flowability of the feedstock powder, together with the coarsening of the WC particles. The decarburization during the formation of the coating is effectively inhibited. As a result, the fracture toughness and abrasive wear resistance of the ultrafine-structured coating are enhanced due to the increased bonding strength of WC and Co inside the splats and also that between the neighboring splats. The present study suggests that controlling the heat-treatment process for the spray-dried powder is an effective approach to improve the properties of the ultrafine-structured WC–Co coatings.