INVESTIGATION OF DIFFUSION BARRIERS FOR REFRACTORY METALS
May 1960-Mar 1962
AERONAUTICAL SYSTEMS DIV WRIGHT FIELD OH
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Thirty-three base barrier combinations involving the four refractory metals W, Mo, Ta, Cb and 12 potential barrier metals having melting points over 1700 C were evaluated for relative interdiffusion behavior at 1700 C. Further evaluation of promising W and Ta-base combinations was carried out at 1800 C. In general, the relative extent of interdiffusion decreases with increasing basebarrier solidus temperature, although wide variations occur for melting points up to 2100 C. The thickness X of the total interdiffusion zone as well as of the intermediate phase layers in the W-Re, Mo-Re, Ta-Re, and Cb- Re combinations was found to increase with time t in accordance with Xn kt, with values of n in the range 1.4 to 4.9. Approximate over-all interdiffusion coefficients, D sub s, of 3.4 x 10 to the 6th power, 9.0 x 10 to the 5th power, 1.9 x 10 to the 8th power, and 5.1 x 10 to the 8th power sq cmsec were found for the W-Re, Mo-Re, Ta-Re, and Cb-Re combinations, respectively.
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