Interaction of Molybdenum with Cobalt–Tin and Cobalt–Copper Melts

Abstract

The solubility of molybdenum in Co–Cu and Co–Sn melts and the growth kinetics of Mo₆Co₇ layer at the molybdenum–melt interface at 1200 °C are examined. The solubility of molybdenum in these melts is well described by the equations: lgС_Мo= –3.642 + 24.589 C_Co – (134.787 ) ∙ C_Co² (Co–Cu melt) and lgС_Мo= –3.363 + 6.552 C_Co – 6.284 ∙ C_Co² (Co–Sn melt). The melt composition (in atomic fractions) in the three-phase equilibrium Mo–Mo₆Co₇–melt is established: C_Co = 5.34 ∙ 10^–3, C_Mo = 3.05 ∙ 10^–4, the rest being Cu (Co–Cu melt); C_Co =  0.176, C_Мо = 5.7 ∙ 10^–3, the rest being Sn (Co–Sn melt). The substantial difference in growth rate constants in the melts (k_Co–Sn >> k_Co–Cu) with the same cobalt activity α_Co is attributed to the impact of admixtures (Cu and Sn) on the growth of the Mo₆Co₇ layer. Data on the solubility of molybdenum in Co–Cu and Co–Sn melts and the growth kinetics of Mo₆Co₇ are obtained for the first time.