A novel bond coat with excellent adhesive strength deposited by plasma-spraying of Mo-clad core-shell-structured metal powders

The adhesion of thermal spray coatings is of essential importance to applications and usually depends on mechanical bonding with a low adhesive strength. The metallic bond coat is generally utilized to increase the coating adhesion. In this study, a novel metal bond coating with high cohesion strength is proposed by plasma-spraying Mo-clad Ni-based or Fe-based spherical powder particles. Mo-cladding ensures the heating of spray particles to Mo melting temperature and prevrents metal core from oxidation during spraying. Theoretical analysis on the splat-substrate interface temperature and experimental examination into coating-substrate interface microstructure were performed to reveal the metallurgical bonding formation mechanism. The local melting of substrate surface and resultant bond coating by impacting high temperature droplets creates the metallurgical bonding throughout the interfaces between substrate and bond coat, and within bond coat. The experiments were conducted with different substrates in different surface processing conditions including Ni-based alloy, stainless steel and low carbon steel. All pull-off tests yielded the adhesive strength higher than the adhesives strength with a highest value of 80 MPa. The present results revealed that Mo-clad metal powders can be used as new bond coat materials and high performance bond coat can be deposited by plasma spraying.