Gas Pressure Bonding

Open-ended Terms: Gas-pressure bonding. Solid-state-bonding by the gas-pressure-bonding process employs a gas at high pressure and elevated temperature in order to fabricate metallic or ceramic materials. The process has been used to produce metallurgical bonds between similar and dissimilar metals, ceramics, and cermet materials. It appears to be ideal for fabricating brittle materials or materials of widely differing properties. Consolidation of metallic and ceramic powders to densities approaching theoretical is readily accomplished by gaspressure bonding at temperatures well below those normally required in sintering operations, and the resulting grain growth is held to a minimum. Numerous configurations have been fabricated from Be and Nb by the gas-pressurebonding process. Examples are cited of typical nuclear fuel elements and various structural components of interest for aircraft and missile application. (Author).

The effects of core barrier coatings, void spaces, and surface-cleaning techniques on the quality of Zircaloyclad flat-plate UO/sub 2/ fuel elements prepared by gas-pressure bonding were investigated. Techniques were developed for the application of barrier layers of chromium by a vapordeposition process and of crystalline carbon by a pyrolytic process. These coatings, together with a graphite coating previously developed, were evaluated in pressure-bonded fuel elements for their effectiveness in preventing coreto-cladding reaction and for their general production feasibility. Crystalline carbon coatings 15 to 40 mu in. thick and chromium coatings 25 to 40 mu in. thick were determined to be satisfactory. In the stady of the flow of cladding-plate material into void spaces in the picture-frame assembly, it was established that excessive flow, and consequent thinning of the cladding, can be minimized by individually compartmentalizing the cores with Zircaloy ribs. This design resulted in maximum restriction of the effects of a cladding failure in service. Quantitative data on the maximum amount of void space resulting from manufucturing tolerances or from chipped fuel cores that is tolerable in cladding failure in service. Quantitative data on the maximum amount of void space resulting from manufucturing tolerances or from chipped fuel cores that is tolerable in elements of this design were obtained. In stadies of surface-cleaning technlques, it was found that a final multistep rinsing cycle resulted in bonds consistently free of evidence of contamination. (See also BMI-1374.) (auth).