THE CONTAMINATION OF REFRACTORY METALS IN VACUA BELOW 10$sup -6$ TORR
From Technical Conference on Applied Aspects of Refractory Metals, Los Angeles, Dec. 1963. The contamination characteristics of Cb-- 1% Zr, Cb, Mo, TZM, and Ta by the residual gases in vacua of 10/sup -7/ to 10/sup -6/ torr and temperatures of 600 to 1200 deg C were determined for times up to l000 hr. The principal contaminant was oxygen and to a lesser degree carbon. Under certain conditions, decarburization and purification occurred. The degree of contamination was largely dependent on the alloy base and was significantiy increased by zirconium and/or titanium alloying additions. The reactivity of these alloys decreased in the order Cb--1% Zr, TZM, Cb, Ta, and Mo. For the Cb-- 1% Zr alloy, contamination was found to increase with temperature, vary inversely as the specimen thickness, while its dependence on system pressure and exposure time was not clearly established. The permissible pressures for negligible contamination are estimated to be below 10/sup -7/ torr. This pressure can be increased to at least 10/sup -6/ torr by wrapping the alloy with refractory metal foils. The function of the foils was to serve as a barrier and not a getter'' since the protectiveness of the foils did not their reactivity. Low pressure CH/ sup 4/ showed promise indcoonntrolling oxygen contamination in some of the alloys. (auth)
- Research Organization:
- Oak Ridge National Lab., Tenn.
- DOE Contract Number:
- W-7405-ENG-26
- NSA Number:
- NSA-18-014355
- OSTI ID:
- 4077901
- Report Number(s):
- CONF-373-7
- Country of Publication:
- United States
- Language:
- English
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