Evaluation of Tantalum-to-Stainless-Steel Transition Joints
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CENTER
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Tantalum-to-stainless-steel bimetallic transition joints were tested to determine the overall strength of the brazed joint. Tensile tests were conducted on flat sheet and tubular specimens at elevated temperatures 1350 degrees F 1005 degrees K and vacuum levels of 10exp -7 to 10exp -6 torr 10exp -5 to 10exp -4 Nm squared. Studies were also conducted to determine if any unfavorable interdiffusion embrittlement was taking place between the braze material and the parent metals. A 2.5 inch 6.4x10exp -2m. Studies were also conducted to determine if any unfavorable interdiffusion embrittlement was taking place between the braze material and the parent metals. A 2.5 inch 6.4x10exp -2 diameter by 0.125-inch 3.18x10exp -3 wall bimetallic joint was subjected to he temperature 1350 degrees F 1005 degrees K and pressure 350 psia 92.41x10exp 6 Nm squared levels expected in a liquid metal loop including 20 temperature cycles between 600 degrees F 589 degrees K and 1350 degrees F 1005 degrees K. The tests indicated 1. The parent material in all tensile specimens ruptured first, leaving the brazed area intact. 2. No significant interdiffusion occurred between the braze and the parent metals. 3. The 2.5 inch 6.4-cm diameter tube remained leak tight after 150 hours of testing at 1350 degrees F 1005 degrees K and 350 psia 2.41x10exp 6 Nm squared. Ultimate and yield strength data are also included for unalloyed tantalum rods, plate and sheet test specimens at 1350 degrees F 1005 degrees K at vacuum levels of 10exp -8 to 10exp -7 torr 10exp 06 to 10exp-5 Nm squared.
- Metallurgy and Metallography