Diffusion between high speed steel and iron powders

Rates of diffusion of W, Mo, V, and Cr have been measured between high speed steel powders and iron powders in the presence of additional carbon. It is shown that the original site of the extra carbon is important and that maximum diffusion rates occur when there is about 1% extra carbon on the iron side of the diffusion interfaces. The diffusion rates are related to microstructural developments in the diffusion zone and are interpreted in terms of the thermodynamic activity gradients developed.