Abstract: An engine component is generally provided for a gas turbine engine generating hot combustion gas flow. In one embodiment, the engine the engine component includes a substrate having a hot surface facing the hot combustion gas flow and a cooling surface facing a cooling fluid flow. The substrate defines a film hole extending through the substrate and having an inlet provided on the cooling surface, an outlet provided on the hot surface, and a passage connecting the inlet and the outlet. The passage defines a diffusion section having a pair of side passage walls extending to the outlet on the hot surface, with each of the side passage walls within the diffusion section having a surface roughness (Ra) of about 4 mils to about 7 mils. Methods are also provided for forming a film hole in a CMC substrate.

Abstract: An engine component is generally provided for a gas turbine engine generating hot combustion gas flow. In one embodiment, the engine the engine component includes a substrate having a hot surface facing the hot combustion gas flow and a cooling surface facing a cooling fluid flow. The substrate defines a film hole extending through the substrate and having an inlet provided on the cooling surface, an outlet provided on the hot surface, and a passage connecting the inlet and the outlet. The passage defines a diffusion section having a pair of side passage walls extending to the outlet on the hot surface, with each of the side passage walls within the diffusion section having a surface roughness (Ra) of about 4 mils to about 7 mils. Methods are also provided for forming a film hole in a CMC substrate.