High Temperature Oxidation Test of ZrB2-based UHTCs by Oxyacetylene Flame

Abstract

Ultra high temperature ceramics (UHTC) include some refractory metal diborides that were historically studied and interests in ZrB2-based ceramics have increased significantly in recent years because of the drive to produce thermal protection systems and other components for hypersonic aerospace vehicles. However, reports on the oxidation and ablation behaviors of ZrB2-based ceramics under simulated atmospheric re-entry conditions are limited and the characterizations are still not well understood because its oxide scale is complex, and it is difficult to achieve temperatures above 2000oC rapidly. In this study, ZrB2-based ceramics were prepared by hot-pressing at 1900oC for 2hrs under 32 MPa and the high temperature oxidation behavior of the specimens was investigated using oxyacetylene flame. The temperature of the oxidation specimens was around 2200oC and the mass and linear oxidation rate plots with time variation were obtained. The mechanical properties test (flexural strength, toughness and hardness) of ZrB2-based ceramics was performed to investigate the effects of high temperature oxidation on mechanical properties. The effects of SiC addition on microstructure, oxidation behavior of ZrB2-based ceramics were also investigated. Finally, the oxidation mechanism of ZrB2-based ceramics will be discussed using volatility diagram.