Liquid-Assisted Interaction of Iridium with Silicon Carbide Ceramics

— Liquid-assisted processes that occur in iridium–silicon carbide diffusion couples have been studied in the temperature range 1500–1800°C at different heat treatment times. We have examined the microstructure and determined the elemental and phase compositions of the diffusion zone forming above eutectic temperatures and/or the melting points of individual reaction products: iridium silicides. The microstructure of the diffusion zone forming under liquid formation conditions has been shown to differ from that forming under the conditions of solid-state reaction between iridium and silicon carbide. At temperatures above 1700°C, the silicon content of the Ir–Si melt exceeds 50 mol %, which leads to crystallization of the Ir 3 Si 4 and Ir 3 Si 5 phases during cooling. The carbon resulting from reaction between iridium and SiC undergoes graphitization with increasing heat treatment temperature and time.