WC-Ti coatings deposited via cold gas spray and modified by laser and furnace heat treatments

This work is focused on furnace and laser post-treatment and characterization of WC-Ti cermet coatings obtained by cold gas spray technique. The main purposes of this study are (i) to find a suitable alternative to cobalt as metallic binder, since it has been listed as a critical material and (ii) to investigate the effects of different post-deposition heat treatments, carried out to trigger a self-propagating high-temperature synthesis reaction able to promote a partial and controlled decarburization of WC and the consequential in-situ nucleation of TiC micro/nano-precipitates. A standard furnace heat-treatment at 550 °C and different laser treatments were performed with the aim of increasing the overall coating microhardness. The effects of the furnace and laser treatments on the WC-Ti coatings were evaluated in terms of microscopic, compositional and phase analyses and through preliminary block-on-ring sliding wear tests. The microstructure exhibited a good distribution of carbides, with an average size ranging from submicrometric to 5μm, and the XRD analysis revealed the formation of TiC in the laser-treated coatings. In the sliding wear tests, the laser-treated materials showed a significative reduction in the wear rate, with a weight loss up to 75% lower than both the furnace-treated and the as-sprayed coatings.