Effect of Oxidation Exposure on Flexural Strength of Hot-Pressed ZrB2-SiC Composites with Cr3C2 Additives

Abstract

Abstract In this study, the effect of oxidation exposure on room temperature flexural strength was examined in 3 and 5 wt% Cr3C2-containing ZrB2-20 vol% SiC composites exposed to air at different temperatures between 1100°C and 1300°C, for up to 100 h. The oxidation products determined by X-ray diffraction consisted of ZrO2, SiO2, Cr2O3 and ZrSiO4. After 100 h of oxidation, the flexural strength of the two compositions was evaluated at room temperature by four-point bending test. The results show that the strength retention displayed by the two compositions depended on the amount of Cr3C2 additives. For 3 wt% Cr3C2composition, the flexural strength slightly increased after 100 h of oxidation at 1100°C, however, the strength substantially degraded after 100 h oxidation at 1200°Cand 1300°C. For 5 wt% Cr3C2 composition, on the other hand, the flexural strength decreased after 100 h of oxidation between 1100°Cand 1300°C. Additionally, the flexural strength was higher for 3 wt%Cr3C2 composition than for 5 wt%Cr3C2one in the oxidation temperature range 1100°C to 1300°C. The strength decrease was associated with the formation and coarsening of defects in the oxidized layer and the delamination of the outermost thinner dense oxide layer.