Influence of in-flight particle states on the particle peening intensity and related properties of HVOF WC-CoCr coatings

The peening mechanism occurring during High Velocity Oxy-Fuel (HVOF) thermal spray deposition of Ceramic-Metallic (CerMet) powders, such as WCCoCr, has long been known to have beneficial effects on the coating properties and performance in wearing and corrosive environments. In this study, the extent of peening, or ‘peening intensity’, and its effect on coating properties and performance of HVOF sprayed WCCoCr is examined. Coatings were deposited using a single feedstock utilizing a variety of process parameters via gas- and liquid- fueled HVOF torches. A Taguchi matrix was used to establish the correlation between processing parameters and in-flight particle states. The peening intensity was assessed via in-situ beam-curvature based measurements, which allow monitoring of stress build-up during deposition, and thus, the ability to identify relationships with the thermal and kinetic energy of the depositing particles. A linear correlation between the particles’ kinetic energy and the coating deposition stress is observed, encompassing both gas- and liquid-fuel torches. Coating properties, such as hardness, and performance, such as abrasive wear and corrosion, are evaluated relatively to the process induced residual coating stress with the goal to identify critical process and stress parameters that might be used for optimizing overall performance of these coatings.