A Novel strategy for Applying Oxide-free Self-fluxing Alloys Coatings by One-step Atmospheric Plasma Spraying

Self-fluxing alloys coatings are usually utilized by spray-fusing two-step process for excellent performance. Fusing process brings out limitations for applications of the coatings. In this study, two NiCrBSi powders with different sizes were used as typical materials for coating deposition at different particle temperatures. The oxygen content in the coatings were analyzed by the inert gas fusion method. The morphology, boron content and phase composition of coatings were analyzed using SEM, ICP-MS, and XRD. The results showed that the oxygen content in NiCrBSi coating was remarkably low. The boron content decreased in coatings compared with original powders. Moreover, it was found that particle temperature significantly influences the coating oxygen content and the higher particle temperature the lower the coating oxygen content. Based on the results, a de-oxide mechanism is proposed for plasma spraying of self-fluxing alloy. Moreover, a novel strategy to directly deposit dense oxide free coatings by atmospheric plasma spraying is proposed based on the mechanisms explored for in-flight particle behavior within high temperature plasma jet. It will be clearly demonstrated that the new approach leads to further wide applications of fluxing alloy materials coatings since high performance of oxide-free coatings can be created without need of fusing process.