The influence of laser glazing on morphology, composition and microhardness of thermal sprayed Ni-WC coatings

Ni-based, thermally sprayed coatings have many commercial applications for wear and corrosion resistance at low and moderate temperatures. The performance of Ni-based coatings can be improved further by adding hard precipitates such as carbides of refractory metals and cemented carbides. The properties of coatings can be further enhanced by laser glazing of the thermally sprayed coatings. In the present study, measurements such as microhardness, surface profile surface morphology and composition were used to compare nickel matrix coatings - NiCrBSi with different tungsten carbide content. The coatings were deposited by HVOF technique and then glazed using Nd:YAG Laser with different scan speeds. The effect of laser treatment and scan speeds were also investigated. Laser glazing of coatings affects the surface roughness in either way depending on the coating composition as well on the treatment parameters. The comparison of the microhardness values of coatings reveals th at the microhardness increases by the post deposition treatment but the extent of increase depends on the scan speed as well as on the coating composition. The SEM/EDAX results explain the observations in terms of effect of laser glazing on the coating composition.