Abstract

Thermal spraying of silicon nitride has been considered impossible because the high temperatures of the spray processes lead to its decomposition and oxidation. To suppress the degradation oxide bonded silicon nitride spray powders (OBSN) have been developed. In this paper spray experiments with these powders by detonation gun spraying (DGS) and atmospheric plasma spraying (APS) with axial powder injection are described. All coatings were characterized using optical microscopy and X-ray diffraction. In addition, DGS coatings were also investigated using SEM, microhardness testing and a rubber wheel abrasion wear test. For the first time, relatively dense Si3N4-rich coatings with an oxide binder phase were produced. The abrasion wear resistance of some DGS coatings was found to be sufficiently high to envisage industrial application. Further progress is expected from optimized spray experiments with variations of spray powder composition and particle size.

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