Environmental barrier coating comprising a gas velocity reducing top layer

摘要

A composite comprising a silicon based substrate, an environmental barrier coating (EBC) with a top layer, wherein the top layer comprises a velocity barrier layer. Velocity barrier layer is. any layer positioned between a flowing gas stream and the underlying EBC protective layer which acts to reduce the velocity of the gas stream which otherwise would impinge on the underlying protective layer. The velocity barrier layer preferably reduces the velocity of an impinging gas stream by at least 50% across the thickness of the velocity barrier layer. It also preferably reduces the velocity of the impinging gas stream to less than 1 meter per second across the thickness of the velocity barrier layer.