Foreign Object Damage of an Environmental Barrier Coated Ceramic Matrix Composite

Foreign object damage (FOD) is one of the key damage modes in environmental barrier coatings (EBCs) developed for gas turbine engines. While there has been extensive research on FOD in metals, ceramics, and ceramic matrix composites (CMCs), there have been limited studies on the effects of FOD in EBC systems. Previous work studied FOD in NASA’s Ytterbium Disilicate EBC that had been deposited on monolithic Silicon Carbide. It was found that impact velocity was limited by the brittle ceramic substrates. In order to understand substrate effects and enable testing at higher impact velocities, the present work will investigate FOD of the same Ytterbium Disilicate EBC deposited on a SiC/SiC CMC substrate. A limiting factor of EBC development is the growth of a SiO2 thermally grown oxide (TGO) layer which exacerbates coating spallation. As such, the effects of steam exposure and heat treatment on FOD will also be explored. FOD testing was conducted at room temperature using a 1.59 mm steel ball projectile with particle velocities ranging from 100–300 m/s at a normal incidence angle. Samples were impacted in the as deposited state, after steam exposure in a 1316°C furnace, and after heat treatment in a 1316°C furnace in air. The impact damage was characterized by optical profilometry and scanning electron microscopy (SEM) of the cross-sections.