Novel Liquid Fuel HVOF Torches Fueled with Ethanol: Optimization and Erosion Wear Response of Cr3C2-NiCr Coatings

Commercial WC-10Co-4Cr powder was sprayed by a novel HVOF process with ethanol used as fuel. Ethanol benefits from environmentally friendly features and less consumption of oxygen compared to conventional fossil liquid fuels (i.e. kerosene). In order to be able to add compressed air into the novel HVOF spray gun, the gun was designed to add a second-stage combustion chamber. Investigations were carried out to determine the influence of different compressed air flow rates on the evolution of the velocity and temperature of in-flight particles in correlation with the properties of the resulting WC-10Co-4Cr coatings. The phase compositions, microstructures, porosity data, microhardness and wear resistance were tested for comparation. The results indicate that the modified spray gun can greatly increase the velocity of the particles while reducing the temperature of the particles, which is generally expected for spraying WC-CoCr powder. In addition, different compressed air flow rates have a significant impact on coating performance. Detailed correlation of compressed air flow rates and the coating properties are elaborated in order to provide the coatings exhibiting optimum properties.

Keywords: HVOF; ethanol; compressed air flow rates; WC-10Co-4Cr; wear resistance