Influence of HVOF spraying parameters on the corrosion resistance of WC–CoCr coatings in strong acidic environment

• Particle temperature and velocity have a significant effect on the coating quality.
• HVOF parameters must allow a sufficient melting of the WC–CoCr agglomerates.
• Moderate decarburization of WC is helpful for the corrosion resistance of coating.
• Corrosion of the metallic CoCr binder phase is the principal corrosion mechanism.

High-velocity oxy-fuel (HVOF) spray techniques can produce cermet coatings for applications that require corrosion resistant surfaces. The aim of this study was to investigate the influence of different oxygen/fuel ratios on velocity and temperature of flying particles and establish the effects on the coatings quality in relation to the corrosion behavior of HVOF WC–CoCr coating in a 0.1 N HCl. The results show that in-flight particle characteristics have a significant effect on the porosity, hardness and corrosion resistance. The highest corrosion resistance is obtained with those parameters that allow a sufficient melting of the agglomerates while minimizing the decarburization of the WC particles.