Characterization of First‐Stage Silicon Nitride Components After Exposure to an Industrial Gas Turbine

Abstract

This paper provides a summary of recent efforts undertaken to examine the mechanical properties and microstructural stability of first‐stage silicon nitride blades and nozzles after field testing in an industrial gas turbine. Two commercially available silicon nitrides, i.e., Kyocera SN282 vanes and SN281 blades, were successfully evaluated in the 100 h final phase engine test at Solar Turbines Incorporated. The turbine rotor inlet temperature was increased from 1010° to 1121°C at 100% speed during the engine test with efficiency increasing from 28.8% to 30.1%. Results of scanning electron microscopy showed that apparent materials recession still occurred during the 100 h engine test, especially in the leading and trailing edge regions where the gas pressure or velocity was the highest. The apparent material recession of the airfoils resulted from the volatilization of the normally protective silica layer, evidenced by the increased surface roughness and porous Lu 2 Si 2 O 7 surface layer features. On the other hand, mechanical results generated using a ball‐on‐ring test technique showed that little strength degradation was measured after the 100 h engine test.