Influence of Plasma Parameters on the Corrosion Resistance and Microstructure of WC-10%Co Coatings

Due to their beneficial wear resistance, WC-Co hardmetals are widely used in industrial applications. An intrinsic weakness, however, is their corrosion susceptibility. The aim of this work was evaluate the influence of processing parameters on the corrosion resistance and morphology of a WC-10%Co commercial alloy thermally sprayed by using a Plasma Praxair S6-100 system. A 3 ³ factorial design experiment was used to establish the effects of the variables on the coating quality. The voltage was varied between 35 and 40 V, the amperage was varied between 700 and 800A and the powder feed rate was varied between 30 and 50 g/min. Response surface methodology (RSM) was employed to describe empirical relationships amongst the studied parameters. The maps obtained allowed the selection of the optimum operating conditions. The corrosion behavior was evaluated by potentiodynamic and linear polarization tests. Scanning electron microscopy technique coupled with X-Ray microanalyses (EDS) were employed for the coatings microstructural characterization before and after the corrosion test in order to identify the possible mechanisms of corrosion. The analysis of the results indicates that the voltage and the powder feed rate have a significant effect on the porosity, microhardness and corrosion resistance of these coatings.