Characterization of carbide--graphite composite material. First progress report
Declassified 30 Aug 1973. Selected billets of 75 wt% NbC. balance graphite composite materials were characterized with respect to structure, homogeneity, compressive creep deformation, flexural strength, and electrical conductivity. In addition, the effects of variations in the purity and properties of the raw materials, NbC and graphite powders, on these properties were assessed. It was established that an average total 1 hour creep deformation of 4 percent could be expected in the across-grain (AG) direction at 2500 deg C and 4000 psi with the provision that rigid control be maintained for NbC powder purity and graphite powder characteristics. The apparent activation energy for the creep deformation was approximately 70 kcal/mole. Creep deformation rate was found to be a quadratic function of stress. The exponent, n, in the strain-time relationship, epsilon - = A t/sub n, was found to be related to stress and temperature. This enables the prediction of creep time curves under varied conditions. The with--grain (WG) creep deformation was approximately 40% greater than the AG creep deformation under the same conditions. Average room- temperature flexural strengths were 13,000 and 9,000 psi in the WG and AG direction, respectively. Variations in the raw-powder characteristic had no effect on room-temperature flexural strength. Flexural strength remained essentially constant to 2500 deg C. AG compressive strength was approximately 40,000 psi at room temperature and 10,000 psi at 2500 deg C. Ductility in flexure was limited at 2000 deg C permitting a maximum permanent bend angle of 2 deg . At 2500 deg C, the maximum permanent bend angle increased to 1O deg . Compressive ductility was above 10% at 2200 deg C. Roomtemperature flexural strength was found to correlate consistently with electrical conductivity, although no direct exponential relationship could be found. (auth)
- Research Organization:
- Westinghouse Electric Corp., Pittsburgh, Pa. (USA). Astronuclear Lab.
- DOE Contract Number:
- SUBNP-1
- NSA Number:
- NSA-29-008370
- OSTI ID:
- 4422258
- Report Number(s):
- WANL-TME-1664
- Resource Relation:
- Other Information: Declassified 30 Aug 1973. Orig. Receipt Date: 30-JUN-74
- Country of Publication:
- United States
- Language:
- English
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Ceramics
& Other Materials-Plastics & Other Materials-Properties
Structure & Phase Studies
*GRAPHITE- MICROSTRUCTURE
*NIOBIUM CARBIDES- MICROSTRUCTURE
COMPOSITE MATERIALS
CREEP
DEFORMATION
ELECTRICAL PROPERTIES
FLEXURAL STRENGTH
HIGH PRESSURE
IMPURITIES
MECHANICAL PROPERTIES
POWDERS
VERY HIGH TEMPERATURE