Stress-Corrosion Cracking of Silicon Carbide Fiber/Silicon Carbide Composites
Ceramic matrix composites are being developed to operate at elevated temperatures and in oxidizing environments. Considerable improvements are being made in the creep resistance of SiC fibers and hence in the high-temperature properties of SiCf/SiC composites; however, more needs to be known about the stability of these materials in oxidizing environments before they will be widely accepted. Experimental weight change (1,2) and crack growth data (3,4) supports the conclusion that O2 enhanced crack growth of SiCf/SiC occurs by more than one mechanism depending on the experimental conditions. This data suggests an oxidation embrittlement mechanism (OEM) at temperatures below 1373?K and high O2 pressures and an interphase removal mechanism (IRM) at temperatures of about 700?K and above and low O2 pressures. The OEM, as proposed by Evans et al. (3), results from the reaction of O2 with SiC to form a glass layer on the fiber or within the fiber-matrix interphase region. The fracture stress of the fiber is reduced if this layer is thicker than a critical value (d>dc) and the temperature is below a critical value (TTg for d>dc. This paper summarizes the evidence for the existence of these two mechanisms and attempts to define the conditions for their operation.
- Research Organization:
- Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC05-76RL01830
- OSTI ID:
- 15001354
- Report Number(s):
- PNNL-SA-32579; JACTAW; KC0201020; TRN: US200412%%207
- Journal Information:
- Journal of the American Ceramic Society, 83(8):1999-2005, Vol. 83, Issue 8; ISSN 0002-7820
- Country of Publication:
- United States
- Language:
- English
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