Effects of Magnetic Field Type on Supersonic Plasma Spraying Particles Flight State and Coating Properties

To illustrate the feasibility and effectiveness of magnetic field in coating preparation, supersonic plasma spraying technology is combined with magnetic field to get better performance coatings in this paper. NiCrBSi-10%WC&Co coatings are prepared by supersonic plasma spray under three conditions, as: without magnetic field, pulsed magnetic field and steady magnetic field. Droplets flight progress, coatings morphology, coatings micromorphology and mechanical properties in three conditions are compared and analyzed in this study. Broken edges appear when molten and unmolten particles spread on matrix. Results indicate that magnitude and direction of droplet velocity when impacting the matrix change under the effect of magnetic field. Observing cross-sectional morphology of coatings, it is found that reinforcement is aggregated because magnetic field promotes the internal flow in coating solidification. Grain refinement occurs under magnetic field according transmission electron microscopy analysis. Moreover, the grain refinement effect under steady magnetic field is stronger than that under pulsed magnetic field. Spreading morphology growth, enhanced phase aggregation and fine-grained structure lead to the higher microhardness and adhesion strength properties in magnetic field coatings.