Effects of Automated Grit Blasting on Roughness and Thickness Loss of Reaction-Bonded Silicon Carbide

Thermally sprayed coatings improve component lifespan and protect the underlying substrate in high temperature and corrosive environments. The coating adhesion is one of the most important properties with respect to coating performance. Before coating, surfaces are typically cleaned and roughened via manual grit blasting to promote mechanical interlocking of the coating with substrate. With recent interest in implementing ceramics and ceramic composites in the hot section of advanced gas turbine engines, there is a need to better understand how to prepare these nonmetal and composite materials before being coated. In this study, an automated grit blasting system was utilized to observe the effects of parameters such as blast pressure, angle, and nozzle traverse speed on multiple surface roughness parameters of reaction-bonded silicon carbide (rb SiC). The effect of these parameters on the substrate thickness loss during grit blasting was also analyzed. Blast pressure had the largest effect on surface roughness, as well as the highest linear correlation with roughness parameters. The automated robotic system allowed for the controlled study of traverse speeds higher than that typically used for grit blasting (≤ 350 mm/s). Increasing nozzle traverse speed was found to greatly reduce material loss with minimal effect on surface roughness.