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Title: Characterization of carbide--graphite composite material. First progress report

Abstract

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-temperaturemore » 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)« less

Authors:
Publication Date:
Research Org.:
Westinghouse Electric Corp., Pittsburgh, Pa. (USA). Astronuclear Lab.
OSTI Identifier:
4422258
Report Number(s):
WANL-TME-1664
NSA Number:
NSA-29-008370
DOE Contract Number:  
SUBNP-1
Resource Type:
Technical Report
Resource Relation:
Other Information: Declassified 30 Aug 1973. Orig. Receipt Date: 30-JUN-74
Country of Publication:
United States
Language:
English
Subject:
N50330* -Metals, 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

Citation Formats

Singleton, R H. Characterization of carbide--graphite composite material. First progress report. United States: N. p., 1967. Web.
Singleton, R H. Characterization of carbide--graphite composite material. First progress report. United States.
Singleton, R H. Sun . "Characterization of carbide--graphite composite material. First progress report". United States.
@article{osti_4422258,
title = {Characterization of carbide--graphite composite material. First progress report},
author = {Singleton, R H},
abstractNote = {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)},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = {1967},
month = {10}
}

Technical Report:
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