Comparative Investigation of Standard WC-Co and a New WC-FeCrAl Feedstock Powder

This study investigates the HVOF spraying characteristics of a new WC-FeCrAl powder as compared to a standard WC-Co feedstock. Significantly higher particle temperatures were recorded for the WC-FeCrAl powder during spraying, presumably an effect of phase reactions during particle dwell time in the jet. XRD graphs revealed W₂C and δ-Fe₂O₃ formations. Gibbs free energy calculations propose that energy is being released during the formation of these phases. Comparable correlations between in-flight particle measurements and splat morphologies were found for both powders. Coating hardness was also found to be comparable, although porosity was significantly lower in the WC-FeCrAl samples. This is attributed to the smaller carbide grain size of the new powder, which might help explain the lower viscosity of the molten particles at impact. A response surface analysis of XRD measurements indicates that W₂C formation occurs in the spray jet, and it is assumed that δ-Fe₂O₃ formation occurs on the surface of the substrate after particle deposition.