The Microstructure and Properties of Plasma Sprayed Ceramic Composites

The microstructure and properties of plasma-sprayed ceramics and ceramic matrix composites (CMCs) have been investigated. Substrate-free deposits were fabricated by plasma spraying onto expendable graphite substrates. The deposits were evaluated in the as-sprayed and heat-treated conditions. X-ray diffractometry (XRD) was used in conjunction with differential scanning calorimetry (DSC) to examine the phase content and transformation temperatures of plasma-sprayed Al2O3. Mechanical properties were measured using three-point flexural testing and density measurements were made for both the as-sprayed and heat treated conditions. Significant increases in modulus and strength were achieved as a result of post -spray heat treatment.;Having established baseline properties with respect to the pure matrix material, the effect of incorporating a second phase was examined. Ceramic matrix composites were fabricated by plasma-spraying a mechanical mixture of Al2O3 and SiC particulate. Composites consisted of particulate SiC and resolidified inclusions in an Al2O3 matrix. Significant improvements in strength and modulus resulted from the incorporation of second phase combined with heat-treatment.