Thermal and mechanical properties of cordierite, mullite and steatite produced by plasma spraying

Cordierite, mullite and steatite are silicate materials widely used in the ceramics industry. There is, however, only sparse information on their application in plasma spraying and properties of sprayed materials. Plasma sprayed deposits of cordierite, mullite and steatite contain amorphous phases as the result of rapid cooling of molten particles. The amorphous phase has a significant influence on physical properties, especially in connection with heat treatment. This article deals with phase changes of cordierite, mullite and steatite, resulting from plasma deposition. Special attention is paid to amorphous phase crystallization in subsequent heat treatment. Plasma sprayed deposits were produced using a water stabilized plasma torch WSP®. The processes taking place in the deposits were examined primarily by differential thermal analysis (DTA), thermal dilatometry (TMA) and X-ray diffraction (XRD). These measurements were complemented by the determination of physical properties (namely, density, Young’s modulus and strength) and morphological observations. Important thermal characteristics like crystallization temperature and the coefficient of thermal expansion (CTE) of all materials were determined.