Study On Fe-Based Coating By Plasma Jet Surface Metallurgy

Plasma Jet surface metallurgy can make a wear-resistant, corrosion-resisting, metallurgically bonded, low-cost coating and this technology owns good economic returns and large market.In this paper, on base of the principle of alloy design and a large number of tests, three new Fe-based alloy being applied on plasma-jet surface metallurgy have been designed successfully. By means of seeding powder synchronically, Fe-based coating has been produced by high-energy plasma beam.The process of plasma-jet surface metallurgy has been discussed, which is a course of quick and non-equilibrium freezing. With the shift of plasma torch, melting and freezing occur simultaneously, and the process of surface metallurgy can be regarded as a phasing and continuous reaction process. The freezing mechanics, characteristic and influence on structure of plasma-jet surface metallurgy have been analyzed in full.Making use of optical microscope, SEM, electron probe, X-ray diffraction etc., morphology and component features have been studied in detail. The coating near the substrate has typical flat epitaxial growth morphology and near the top has relatively regular dendritic morphology. The growth of grains is affected by crystallographic aeolotropy. The different component increased or decreased generally, but has been disturbed from microscopic view. The white-bright band , appearing between the coating and the substrate, proved metallurgical bond.Some defects appeared in the coating. In this paper, just two defects, gas cavity and crack, have been involved. Their reasons and mechanics have been discussed in detail. Furthermore, the conception of molten bath viscosity has been presented. The molten bath viscosity affects the surface quality and structure of metallurgical coating directly. So the molten bath viscosity can be look on as a criterion of designing powder of plasma-jet surface metallurgy.