Development of 1400°C (2552°F) Class Ceramic Matrix Composite Turbine Shroud and Demonstration Test With JAXA F7 Aircraft Engine

Serviceable temperature for turbine components material of aircraft engines is increasingly needed to be higher in order to improve engine performance and durability. Recently SiC/SiC Ceramic Matrix Composites (CMCs) are commercialized instead of Ni-base super alloys which have been used for turbine components. The Authors developed 1400°C (2552°F) class CMC material system which consist of SiC fibers and SiC matrix and ytterbium silicate base matrix, aiming for higher temperature capability on consignment from the New Energy and Industrial Technology Development Organization (NEDO). Then they designed and manufactured high pressure turbine shrouds for aircraft engines using that 1400°C class material system, and they conducted strength tests and thermal cycle tests for turbine shroud components. After that they conducted engine tests for the CMC turbine shrouds demonstration in the actual engine environment jointly with the Japan Aerospace Exploration Agency (JAXA) in 2021. The test vehicle for this demonstration engine tests was the F7 engine which was introduced in 2019 at JAXA as the first case of a commercial transfer of the F7-10 turbofan engine which was developed by the Acquisition, Technology & Logistics Agency (ATLA) for the P-1 maritime patrol aircraft. The engine test was conducted for over 75 hours including over 35 hour hot time. After the test teardown inspection was conducted. No spallation of EBC, no recession and no wear on CMC turbine shrouds were found. As the result of the microstructure observation for cut faces of CMC turbine shrouds, no oxidation in SiC fibers, no chemical reaction in matrix, and no microcrack in matrix were found, but, some oxidation in fiber interface coating and microcrack in EBC were found. Bending strength tests with specimens cut out from CMC turbine shrouds were conducted in order to survey the degradation of material. Two types of specimens were prepared. One was the specimen cut out from the high temperature portion. The other was the specimen cut out from the high stress portion. As the result of bending test, the strength of the specimens cut out from engine tested shrouds were equivalent to the strength of the specimens cut out from unused shrouds. The CMC turbine shrouds after engine test were determined to be serviceable, therefore the developed 1400°C class CMC shrouds was proven to be sound in an actual engine environment.