Corrosion characteristics of plasma-sprayed Ni-coated WC coatings comparison with different post-treatment

The effects of vacuum annealing and laser remelting on the microstructure and corrosion behaviour of plasma-sprayed Ni-coated WC coatings on steel substrate have been investigated. The laser remelting was operated in a continuous way while the vacuum annealing was operated with clamping the coating on the graphite face in order to avoid decarburization of WC. When compared with the as-sprayed coating, the microstructure of the post-heating treatment coatings has been found to consist of different phases. Moreover, the denser microstructure can be obtained after heating treatment, especially the laser remelting coating. Electron probe micro analyzer (EPMA) shows that the chemical composition remained largely unchanged except the “bumps” at the interface for as-sprayed and vacuum annealing coatings. The more uniform composition was obtained for laser remelting coating. The Vickers microhardness measurement shows a very slightly enhancement for post-heating treatment coatings, which may be duo to the lamellar structure, lower contemt and bulky of carbide for coatings. However, salt spray corrosion (SSC) show the laser remelting coating has the best corrosion resistance, which is due to its low number defects and uniform distribution of the phase and composition.