Development of dense Si coatings by atmospheric plasma spraying

In modern aircraft engines, ceramic matrix composites with thermally sprayed protective coatings are used, which service life depends, among other things, on the properties of the Si bond coat. In this study, Si coatings were produced and characterized using Atmospheric Plasma Spraying (APS). The process parameters were varied to produce dense and low-oxide Si coatings. Particle temperatures and velocities were determined using optical particle diagnostics. The Si coatings were analyzed in terms of their surface topography, coating structures, microhardness as well as indentation moduli. The results show that the particle temperatures and velocities under all spraying conditions are generally at a very high level for the three-cathode plasma spraying process used. As a result, all Si coatings exhibit a dense coating structure and a low number of oxide inclusions. However, the deposition efficiency of the Si powder is limited.