In-Flight Reactions of Metallic Particles during Thermal Spraying

Abstract

During thermal spraying of metal materials reactions between the spray materials and the gaseous species from plasma gas, atomization gas or surrounding atmosphere occur. Some reactions like nitriding during reactive spraying are designed to improve coating properties, while other reactions like oxidation during atmospheric plasma spraying of stainless steels impair the coating properties. In this study, the reaction of titanium particles in-flight during reactive plasma spraying and the reaction of the 316 L stainless steel in-flight during HVOF spraying were investigated. It was found that the melting degree of the powders was essentially important for the reactions in-flight. The convection movement within a molten particle significantly accelerated the reactions.