Erosion Resistance of WC-12Co High Velocity Oxy-Fuel Coatings

In this work a number of different WC-12Co powder formulations were applied to coupons of steel using HVOF (high velocity oxy-fuel) and DSC (detonation spray coating) spray techniques. Two different HVOF guns and a super detonation gun (Super D-Gun ) were used to apply the coatings. The coated specimens were heat treated in an inert atmosphere at various temperatures in the range of 540°C -1000°C and subsequently characterized using optical microscopy, a Vicker’s microhardness tester, SEM (Scanning Electron Microscopy) and XRD (X-Ray Diffraction) to identify the phases generated. Additionally, in situ XRD was performed on a subset of these samples to explore the progression of the phase transformations as a function of temperature. Samples were also exposed to sand erosion with 20-30 mesh Ottawa sand at 825 feet per second to quantify performance. The work shows that the heat treatment and the transformation of amorphous metallic phases, WC and W₂C to the η phase (Co₆W₆C) results in higher hardness and lower sand erosion rates.