Creep performance of candidate SiC and Si{sub 3}N{sub 4} materials for land-based, gas turbine engine components
Tensile creep-rupture of a commercial gas pressure sintered Si3N4 and a sintered SiC is examined at 1038, 1150, and 1350 C. These 2 ceramics are candidates for nozzles and combustor tiles that are to be retrofitted in land-based gas turbine engines, and there is interest in their high temperature performance over service times {ge} 10,000 h (14 months). For this long lifetime, a static tensile stress of 300 MPa at 1038/1150 C and 125 Mpa at 1350 C cannot be exceeded for Si3N4; for SiC, the corresponding numbers are 300 Mpa at 1038 C, 250 MPa at 1150 C, and 180 MPa at 1350 C. Creep-stress exponents for Si3N4 are 33, 17, and 8 for 1038, 1150, 1350 C; fatigue- stress exponents are equivalent to creep exponents, suggesting that the fatigue mechanism causing fracture is related to the creep mechanism. Little success was obtained in producing failure in SiC after several decades of time through exposure to appropriate tensile stress; if failure did not occur on loading, then the SiC specimens most often did not creep-rupture. Creep-stress exponents for the SiC were determined to be 57, 27, and 11 for 1038, 1150, and 1350 C. For SiC, the fatigue-stress exponents did not correlate as well with creep-stress exponents. Failures that occurred in the SiC were a result of slow crack growth that initiated from the surface.
- Research Organization:
- Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC05-96OR22464
- OSTI ID:
- 236225
- Report Number(s):
- CONF-960608-3; ON: DE96006703
- Resource Relation:
- Conference: 41. American Society of Mechanical Engineers (ASME) international gas turbine and aeroengine congress and exposition, Birmingham (United Kingdom), 10-13 Jun 1996; Other Information: PBD: [1996]
- Country of Publication:
- United States
- Language:
- English
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