Estimate of the diffusion coefficient in Co based liquids

The experimental determination of the diffusion coefficient of given specie s into liquid alloys is difficult because of the unavoidable contribution o f the convection. This remark applies to the case of tungsten (W) and carbo n (C), introduced in liquid cobalt (Co) through the dissolution of tungsten carbide (WC). In the present work, the flow patterns produced by two diffe rent conditions of electromagnetic stirring of the liquid Co bath are compu ted. The electromagnetic forces which are induced by a high frequency induc tion coil are calculated with an integral method. They are introduced into a finite volume code for calculating the flow field. The velocity character istics which are determined together with the experimental values of the ra te constants [O. Lavergne, C, Allibert, Dissolution mechanism of WC in Co b ased liquids, High Temperatures, High Pressures 31 (1999)] for the dissolut ion of WC in the stirred liquid Co at 1450 degrees C lead to evaluate the d iffusion coefficient to 2 10(-9) m(2) s(-1). It is remarkable that the valu es of D which are deduced for each case differ only from 14%. (C) 1999 Else vier Science Ltd. All rights reserved.