Deposition of WC-Co Coatings by a Novel High Pressure HVOF

Abstract

Abstract WC-Co coatings are primarily deposited by using the high velocity oxy-fuel (HVOF) spray process. However, the decomposition and decarburization of carbides during spraying result in the degradation of coating wear performance. In this paper, a novel high pressure HVOF with the characteristics of lower particle temperature and higher particle velocity was developed. It exhibits combustion chamber pressures up to 3.0 MPa. The influence of combustion chamber pressure and oxygen/fuel equivalence ratio on WC-Co particle velocity and temperature levels were analyzed by numerical simulation. The experiment results show that the combustion chamber pressure and the oxygen/fuel equivalence ratio have a significant influence on the particle velocity and melt degrees, as well as, on the coating microstructure and microhardness. High velocity WCCo particles in different states, i.e., molten, semi-molten and non-molten can be readily obtained by changing the spray conditions. A comparison to the conventional JP-5000 was also executed.