105 Matching Results

Search Results

Advanced search parameters have been applied.

Application of thick film and bulk coating technology to the Subterrene program

Description: From conference on structure-property relationships in thick film and bulk coatings; San Francisco, California, USA (28 Jan The Subterrene is a rock- melting earth-penetration system representing a significant advancement in excavation technology. Temperatures of 1700-2000 deg K are involved, and heated refractorymetal or alloy probes are used. Corrosion problems are severe on the exterior surfaces of the refractory metals used; bulk coatings having the required properties would be extremely desirable provided they could be deposited upon a substrate as a tenacious coating. Within the Subterrene, pyrographite radiant heaters are operating at temperatures to 2450 deg K. Graphite receptors added to improve the radiant heat transfer react with the Mo and W penetrator bodies to form carbides. A 30 mu m-thick CVD film of TaC may be applied to inhibit this reaction. The techniques of applying these fllms, their nature, and the results of their application, are discussed. The environment of an operating penetrator is described, and the requirements and properties of exterior coatings are outlined. (auth)
Date: January 1, 1974
Creator: Stark, W.A. Jr.; Wallace, T.C.; Witteman, W.; Krupka, M.C.; David, W.R. & Radosevich, C.
Partner: UNT Libraries Government Documents Department

Liquid lithium corrosion research. Progress report, April 1, 1975-- December 31, 1975

Description: Kinetics for grain boundary penetration and weight loss were determined for 304L stainless steel in Ti-gettered liquid Li. Empirical weight loss rate coefficient expressions were determined as function of both N content and temperature which predict the weight loss behavior of stainless steel for Li with high N content. Capillarity was eliminated as a possible driving force for grain boundary penetration of Fe by Li with the evidence of a grain boundary groove. Coupled ionic diffusion in a corrosion product surface film is suggested as the controlling mechanism for grain boundary grooving of Fe in N-contaminated liquid Li. Stress-enhanced grain boundary penetration showed that the penetration of stressed Fe is a function of t sup 1/3 rather than t sup 1/2, suggesting that primary creep of the Fe is continually breaking the protective corrosion product in the grain boundaries. A new purification procedure and systems were designed and constructed to achieve very low N contents in the liquid Li (less than 300 ppM N). A gas purification train, based on a molten Al bubbler for the removal of O and N, was designed and built, and vacuum melting of as-received Li and gettering are being initiated. Experiments designed to determine the role of Cr in stainless steel resistance are in progress. Also experiments have been designed which will investigate how liquid metal corrosion is a function of the contact potential between the metals. (auth)
Date: January 1, 1975
Creator: Olson, D.L. & Bradley, W.L.
Partner: UNT Libraries Government Documents Department

Twin boundary cavitation in aged type 304 stainless steel

Description: A transition from grain to twin boundary cavitation was observed in aged- and-creep-tested type 304 stainless steel. Evidence of twin boundary cavitation has also been observed for unaged material under certain test conditions. This same behavior was also found in aged type 316 stainless steel. Several possible reasons have been suggested for the absence of frequently observed grain boundary cavitation. (auth)
Date: October 1, 1975
Creator: Sikka, V.K.; Swindeman, R.W. & Brinkman, C.R.
Partner: UNT Libraries Government Documents Department

Preliminary assessment of corrosion product transport in fusion reactors

Description: Corrosion which is tolerable from the standpoint of system mechanical integrity may cause substantial problems if the corrosion product is released and deposited at locations where it interferes with heat transfer or coolant flow. Furthermore, neutrons from the fusion reaction activate the corrosion product, causing radiation fields in maintenance areas near piping and components where the activated material deposits. Preliminary estimates suggest that formidable problems may occur in a lithium-cooled stainless steel primary circuit due to corrosion product deposition. If the estimated order of magnitude is confirmed in future studies, new concepts in corrosion control or corrosion product removal would need to be developed for lithium-cooled stainless steel CTR systems. Other fusion reactor system concepts and materials appear to offer alternatives which tend to minimize corrosion product transport. (auth)
Date: November 1, 1973
Creator: Johnson, A.B. Jr. & Vogelsang, W.F.
Partner: UNT Libraries Government Documents Department

Particle release from niobium under 14-MeV neutron impact

Description: The particle release from cold-rolled and annealed polycrystalline niobium surfuces under 14-MeV neutron impact to a total dose of 4.6 x 10/sup 15/ neutrons/cm/sup 2/ was investigated in two separate runs at ambient temperature and under ultrahigh and high-vacuum conditions, respectively. The type and amount of material released and deposited on a substrate surface were determined independently by four analytic techniques. Surprisingly. there were two types of deposits---one in the form of large chunks. the other a more even layer covering the surface. For the cold-rolled niobium sample with a surface finish of 5 mu m the estimated particle release value is S = 0.25 plus or minus 0.10 niobium atoms per incident 14-MeV neutron. A model for the chunk emission is suggested. (auth)
Date: January 1, 1973
Creator: Kaminsky, M. & Das, S.K.
Partner: UNT Libraries Government Documents Department