Lifetime Response of a Hi-Nicalon Fiber-Reinforced Melt-Infiltrated SiC Matrix Composites
- ORNL
Lifetime studies in four-point flexure were performed on a Hi-NicalonTM fiber-reinforced SiC matrix composite over a temperature range of 700 degrees to 1150 degrees C in air. The composite consisted of ~40 vol. % Hi-NicalonTM fiber (8-harness weave) with a 0.5 Mu-m BN fiber coating and a melt-infiltration SiC matrix wand was tested with as-machined surfaces. Lifetime results indicated that the composite exhibited a stress-dependent lifetime at stress levels above an apparent fatigue limit, similar to the trend observed in CG-NicalonTM fiber reinforced CVI SiC matrix composites. At less than or equal to 950 degrees C, the lifetimes of Hi-Nicalon/MI SiC composites decreased with increasing applied stress level and test temperature. However, the lifetimes were extended as test temperature increased from 950 degees to 1150 degrees C as a result of surface crack sealing due to glass formation by the oxidation of Mi SiC matrix. The lifetime governing processes were, in general, attributed to the progressive oxidation of BN fiber coating and formation of glassy phase, which formed a strong bond between fiber and matrix, resulting in embrittlement of the composite with time.
- Research Organization:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN
- Sponsoring Organization:
- USDOE Office of Industrial Technologies (OIT) (EE-20)
- DOE Contract Number:
- AC05-96OR22464
- OSTI ID:
- 6877
- Report Number(s):
- ORNL/CP-102833; EE 38 01 00 0; ON: DE00006877
- Country of Publication:
- United States
- Language:
- English
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