Measurement of interdiffusivity for fcc_A1 Co-V-W alloys

Abstract

Combining the solid-solid diffusion couples and the electron probe microanalysis (EPMA) technique, the composition profiles of 15 ternary diffusion couples within single fcc_A1 Co-V-W alloys at 1373, 1423 and 1473 K were measured in the present work. The interdiffusivities were evaluated by means of composition profiles applied to Matano-Kirkaldy method, in which the uncertainties were calculated by error propagation and the reliability was validated via thermodynamic constraints. According to the measured main interdiffusivities D˜VVCo and D˜WWCo, it is found that the diffusion of V in fcc_A1 Co is faster than that of W in fcc_A1 Co. The ternary main interdiffusion coefficients of D˜VVCo and D˜WWCo at different compositions were compared with the ones for boundary binary CoV and CoW systems in the literature. A normalized ternary interdiffusivity diagram, in which the ternary interdiffusivities D˜VVCo and D˜WWCo are plotted against the normalized ration of x(W)/(x(W) + x(V)), is proposed in the present work. Meanwhile, comprehensive comparisons of main interdiffusivity D˜XXCo in fcc_A1 Co-W-X (X = Al, V, Cr, Mo) alloys and D˜YYCoin fcc_A1 Co-V-Y (Y = Al, Ti, Mo, W) alloys indicate that both of the main interdiffusivities decrease with the increase of atomic number. The present work provides interdiffusivties for the establishment of a kinetic database to computationally design the multi-component cemented carbides.