Corrosion and wear behaviour of HVOF spraying WC-12% Ni coating on gray cast-iron

Abstract

The coatings produced with high-velocity oxygen fuel spraying technology can greatly improve wear and corrosion resistance. In this study, WC-12% Ni coating was applied on the lamellar graphite cast iron substrate. Morphologies and structures of uncoated samples and sprayed coatings were analyzed with light microscopy, scanning electron microscope, energy dispersive spectrometry and X-ray diffraction. Although their micro-hardness, porosity, abrasion and corrosion properties were studied, wear experiments were performed at normal atmospheric conditions (under room temperature and 30% humidity) in the reciprocating wear testing machine. The corrosion resistance of the coatings was measured using potentio-dynamic polarization. The results revealed that the microstructure was porous, had micro-cracks, and contained some inhomogeneous structures such as carbide. Energy dispersive spectrometry analysis revealed that the presence of phases indicated the success in coating process. It was found that the WC-12% Ni coating exhibited lower potential and lower corrosion current density compared to those of the uncoated sample.