Investigation of operating parameters on high-velocity oxyfuel thermal spray coating quality for aerospace applications

The coating quality by the high-velocity oxyfuel (HVOF) thermal spray process is greatly dependent on the operating parameters chosen during the operation. Depending on the application, the operating conditions are manipulated to enhance the desired coating property. Enhancement of multiple properties necessitates optimization of the operating conditions. This entails a comprehensive analysis of several coatings deposited at different operating conditions. The design of experiments is an effective method that helps in identifying optimum operating conditions with a reduced number of experiments. In the present study, a 2⁴ factorial design approach is used to establish the relationships between four operating parameters (coating thickness, fuel/oxygen ratio, spraying distance, and powder injection rate) and three coating properties (roughness, microhardness, and contact angle). The results obtained are utilized in identifying the optimum parameters that produce the best coating quality. Furthermore, the study also compares the coating quality obtained by the HVOF thermal spray process with that by chrome plating. The results show that the HVOF thermal spray process produces superior coating quality and it can be a promising environmentally friendly candidate for replacing chrome plating.