Effect of laser remelting on corrosion behavior of plasma-sprayed Ni-coated WC coatings

The corrosion properties of plasma-sprayed (PS) Ni-coated WC coatings are studied for both before and after laser remelting of the coatings. Optic microscope (OM), scanning electron microscope (SEM) and X-ray diffraction (XRD) are applied to investigate the microstructure and phase composition of PS Ni-coated WC coatings. The results indicate that coatings with laser remelting could improve their microstructure, such as lower porosity rate, weaker lamellar structure and more uniform distribution of phases. XRD shows that the W2C phase is not identified both in as-sprayed and coatings with laser remelting, which means that the decarburization of WC has not happened because of Ni-coated WC grain. However, the Ni compounds were observed both in the plasma spray and the laser-remelting coatings. The salt spray corrosion (SSC) shows that the laser remelting coating has better corrosion resistance, which is mainly due to its fully dense top layer, low number of defects and uniform distribution of the phase and composition.