Exposure of ceramics and ceramic matrix composites in simulated and actualcombustor environments

A high-temperature, high-pressure, tube furnace has been used to evaluate t he long term stability, of different monolithic ceramic and ceramic matrix composite materials in a simulated combustor environment. All of the tests have been run at 150 psia, 1204 degreesC, and 15 percent steam in increment al 500 h runs. The major advantage of this system is the high sample throug hput; >20 samples can be exposed in each tube at the same time under simila r exposure conditions. Microstructural evaluations of the samples were cond ucted after each 500 h exposure to characterize the extent of surface damag e, to calculate surface recession rates, and to determine degradation mecha nisms for the different materials. The validity of this exposure rig for si mulating real combustor environments was established by comparing materials exposed in the rest rig and combustor liner materials exposed for similar times in an actual gas turbine combustor under commercial operating conditi ons.