Improving the Adhesion of Cold Sprayed WC-Co-Ni Composite Coatings through the Development of a Bond Coat

Wear resistant coatings are materials that enhance the tribological properties of parts without modifying bulk properties. Among these wear resistant coatings, cemented carbides, specifically WC-Co, is prevalent thanks to its combination of hardness and toughness. However, when produced by many thermal spray techniques, the WC often gets decarburized, forming detrimental phases for tribological applications. Cold spray comes as a solution to overcome such issues since the lower process temperature allows for the deposition of materials without detrimental effects on the powder or the substrate. Several studies have shown the feasibility of producing WC-Co by cold spray, often by adding a metallic binder, such as Ni, to entrap the hard WC-Co agglomerated particles, but those deposits often suffer from low adhesion strength. In this study, the deposition of a bond coat is proposed to improve the adhesion of such coatings. Pull-off adhesion tests were performed to assess the adhesion of the deposits and microhardness was used to determine coating and bond layer hardness. Lastly, a tribological assessment of the coatings was performed to determine their wear resistance.