Interface structure and reaction kinetics between SiC and thick cobalt foils

Abstract

Reaction couples of SiC with thick cobalt foils were annealed in an Ar-4 vol% H2 atmosphere at temperatures between 950 and 1250 °C for times between 4 and 100 h. At temperatures above 950 °C, solid-state reactions lead to the formation of various silicides with carbon precipitates. The typical layer sequence in the reaction zone was determined by quantitative microanalysis to be SiC/CoSi+C/Co2Si+C/Co2Si/Co2Si+C/ ... /Co2Si/Co(Si)/Co. The mechanism of the periodic band structure formation with the carbon precipitation behaviour was discussed in terms of reaction kinetics and thermodynamic considerations. Two ternary phases, CoSiC2 and Co2SiC3, unstable at room temperature, may exist in the system Co-Si-C. The growth of the reaction zone is dependent on the square root of time. The reaction kinetics are proposed to estimate the effective reaction constant from the parabolic growth of the reaction zone. The mechanical properties of the reaction zones were determined by the microhardness test.