Interdiffusion of Chromium in Molten Fe-Cr and Fe-Cr-Ni Alloys

Abstract

Interdiffusion coefficients of chromium in molten Fe-Cr and Fe-Cr-Ni alloys have been determined at 1 550°C by the diffusion couple method with the following results:
(1) Interdiffusion coefficient in molten Fe-Cr alloy, D_Fe-Cr, is expressed by the following empirical equation for chromium content up to 15 at%:
D_Fe-Cr×10⁵=3.36-20.9N_Cr+171N²_Cr, cm²/s
(2) In molten Fe-Cr-Ni alloy with the composition of 4 at%Ni and 0 to 12 at%Cr, the main (diagonal) diffusion coefficient of chromium, D_CrCr, is 1.3 to 1.9 times as large as the binary diffusivity D_Fe-Cr, that is, an addition of nickel increases the diffusion rate of chromium. Cross diffusion coefficients, D_CrNi and D_NiCr, are estimated to be negative and smaller than the main coefficients by an order of magnitude.