Mechanical Properties, Thermal Shock Resistance, and Thermal Stability of Zirconia‐Toughened Alumina‐10 vol% Silicon Carbide Whisker Ceramic Matrix Composite

Abstract

Zirconia‐toughened alumina (Al2O3–15 vol% Y‐PSZ (3 mol% Y2O3)) reinforced with 10 vol% silicon carbide whiskers (ZTA‐10SiCw) ceramic matrix composite has been characterized with respect to its room‐temperature mechanical properties, thermal shock resistance, and thermal stability at temperatures above 1073 K. The current ceramic composite has a flexural strength of ∽550 to 610 MPa and a fracture toughness, KIC, of ∽5.6 to 5.9 MPa·m1/2 at room temperature. Increases in surface fracture toughness, ∽30%, of thermally shocked samples were observed because of thermal‐stress‐induced tetragonal‐to‐monoclinic phase transformation of tetragonal ZrO2 grains dispersed in the matrix. The residual flexural strength of ZTA–10 SiCw ceramic composite, after single thermal shock quenches from 1373–1573 to 373 K, was ∽10% higher than that of the unshocked material. The composite retained ∽80% of its original flexural strength after 10 thermal shock quenches from 1373–1573 to 373K. Surface degradation was observed after thermal shock and isothermal heat treatments as a result of SiC whisker oxidation and surface blistering and swelling due to the release of CO gas bubbles. The oxidation rate of SiC whiskers in ZTA‐10SiCw composite was found to increase with temperature, with calculated rates of ∽8.3×10−8 and ∽3.3×10−7 kg/(m2·s) at 1373 and 1573 K, respectively. It is concluded that this ZTA‐10SiCw composite is not suitable for high‐temperature applications above 1300 K in oxidizing atmosphere because of severe surface degradation.