Tensile behavior of SiC/C and Rene'41 following isothermal exposure and thermal fatigue

Abstract

The performance of a coated silicon carbide/carbon composite under isothermal and thermal fatigue conditions was investigated. The material studied is known as Ceracarb™ which consists of eight-harness satin weave Nicalon® silicon carbide cloth reinforcement, a carbonaceous matrix, and a silicon carbide composite coating. This advanced composite is being considered for replacing the nickel based superalloy Rene'41, as the exhaust nozzle components on military afterburning turbine engines. Thermal fatigue experiments, performed in the laboratory using a thermal cycling test system, were intended to roughly simulate the thermal excursions of an afterburning exhaust nozzle. Several thermal profiles were used to characterize the role of temperature, number of cycles, temperature range, and time at temperature, on the room temperature residual tensile strength of the material. The same thermal profiles were also conducted on test specimens of Rene'41 in order to compare its durability in the laboratory simulation test set-up to the composite. Both materials showed no loss in strength from the as-received condition following thermal testing. However, the Rene'41 showed evidence of microstructural instability at the maximum test temperature of 1093°C (2000°F) which did affect the toughness of the material. While the results from this study showed that both materials retained strength when thermally exposed in the laboratory under no loads, thermal testing under load may provide a more realistic view of how the materials perform in the afterburning exhaust nozzle application.