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

The performance of a coated silicon carbide/carbon composite under isotherm al and thermal fatigue conditions was investigated. The material studied is known as Ceracarb(TM) which consists of eight-harness satin weave Nicalon( R) silicon carbide cloth reinforcement, a carbonaceous matrix, and a silico n carbide composite coating. This advanced composite is being considered fo r replacing the nickel based superalloy Rene'41, as the exhaust nozzle comp onents on military afterburning turbine engines. Thermal fatigue experiment s, performed in the laboratory using a thermal cycling test system, were in tended to roughly simulate the thermal excursions of an afterburning exhaus t nozzle. Several thermal profiles were used to characterize the role of te mperature, number of cycles, temperature range, and time at temperature, on the room temperature residual tensile strength of the material. The same t hermal profiles were also conducted on test specimens of Rene'41 in order t o compare its durability in the laboratory simulation test set-up to the co mposite. Both materials showed no loss in strength from the as-received con dition following thermal testing. However, the Rene'41 showed evidence of m icrostructural instability at the maximum test temperature of 1093 degrees C (2000 degrees F) which did affect the toughness of the material. While th e 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. (C) 2000 Kluwer Academic Publisher s.