Preliminary Investigation on the Potential of VC-WC-Co HP/HVOF Powders and Coatings

It has been observed that VC-WC-Co hardmetals have a better wear resistance than conventional WC-Co hardmetals. This work represents a first attempt to add VC to thermal spray powders in order to determine whether this would increase the wear resistance of HVOF hardmetal coatings. Standard WC-Co and WC-CoCr thermal spray powders were compared to two experimental VC-WC-Co powders in terms of size distribution, morphology and phase composition. Coatings were produced from the powders using the TAFA JP-5000 High Pressure High Velocity Oxy-Fuel (HP/HVOF) process. The microstructure, phase composition, hardness, dry solid particle erosion and three body abrasion of the coatings were compared. It was found that due to the non-homogeneous dispersion of VC particles in the powders, the experimental coatings were not optimised. Nevertheless they showed some advantage over the conventional coatings, particularly in low angle erosion tests. This result is regarded as promising, and it is believed that a homogeneous dispersion of VC particles in the coatings would result in a significant increase in wear resistance. In order to test this, the manufacture of improved powders and optimised coating microstructures would be necessary as a next step.