Behavior of Ceramics at 1200° C in a Simulated Gas Turbine Environment

This report summarizes programs at the NASA Lewis Research Center evaluating several classes of commercial ceramics, in a high gas velocity burner rig simulating a gas turbine engine environment. Testing of 23 ceramics in rod geometry identified SiC and Si₃N₄ as outstanding in resistance to oxidation and thermal stress and identified the failure modes of other ceramics. Further testing of a group of 15 types of SiC and Si₃N₄ in simulated vane shape geometry has identified a hot pressed SiC, a reaction sintered SiC and hot pressed Si₃N₄ as the best of that group. SiC and Si₃N₄ test specimens were compared on the basis of weight change, dimensional reductions, metallography, fluorescent penetrant inspection, X-ray diffraction analyses, and failure mode.