Dry Coated Particle for Plasma Spraying

The performance of an in-house designed mechanofusion process and the preparation of composite powders for plasma spraying are investigated in a variety of powdered mixtures including metal/oxide, carbide/oxide, carbide/metal and metal/oxide/carbide. Scanning electron microscopy shows that dry particle coating depends on the thermo-mechanical and chemical properties of the powdered system. In the metal/oxide, carbide/oxide and metal/oxide/carbide powder mixtures, fine ceramic particles coat the surface of the metallic or ceramic coarser particles with no need of binders or solvents. However with the carbide/metal powdered system, an intimate mixture of components is achieved with an incipient dry particle coating. A nearly rounded shape of the final composite particles is induced by the mechanical energy input with no formation of new phases as confirmed by XRD analysis. It is suggested that the coating mechanism is governed by agglomeration and rolling phenomena. Finally these types of powders feature characteristics to be plasma sprayed in air.