Microstructural patterning of the reaction zone formed by solid-state interaction between iridium and SiC ceramics

Abstract

The phenomena occurring within the Ir–SiC couple depending on temperature and time were studied. In the temperature range of 1300–1400°C, when all the components of the Ir–Si–C system are solids, the following sequence of phases is formed between Ir and SiC plates: Ir / Ir3Si / Eutectoid / Ir3Si2 / IrSi / IrSi + C/ SiC. The effect of exposure time on the morphology, phase composition, and thickness of the product layer was studied. The reaction between Ir and SiC was shown to obey the linear law, being indicative of the kinetic control. Iridium atoms diffuse faster across the product layer than silicon atoms do. The product thickness increases mainly due to growth of the IrSi layer with carbon inclusions. A periodic morphology of the IrSi layer composed of carbon-free IrSi layers and IrSi layers with carbon inclusions is observed with increasing exposure time. The thickness of carbon-free IrSi layers and sizes of carbon inclusions increases at greater distances from the reaction front. The process is accompanied by ordering and graphitization of carbon inclusions. The Vickers microhardness for the iridium silicide phases were measured. The microhardness of iridium silicides is ∼ 3 times less than that of SiC that can decrease the brittleness of SiC-based materials.