Development of Protective Coatings for Tantalum Base Alloys. Task II. Development of Technology Applicable to Coatings Used in the 3000 to 4000 F Temperature Range

摘要

The objective of this program was to develop new concepts and obtain experimental data which would be useful in a solution to the problem of the protection of tantalum from oxidation in the 3000 to 4000 F temperature range. Studies of bulk oxides were made to determine what modifier oxides would be required to form the optimum oxide coating. Thermal expansion measurements were performed on oxides from 1500 to 4000 F to determine the expansion match with tantalum. Electrical conductivity of an oxide was used as one indication of the diffusion characteristics of an oxide; hence its protective ability. Compatibility tests were also conducted with oxide, reservoir, barrier, and substrate material. The experimental results indicate that hafnia or hafnia modified with ZrO2 and Y2O3 are suitable for continued investigation as coating materials. Hafnium appears to be a suitable reservoir material with tungsten as a barrier on tantalum. (Author)