Thermal shock resistance of Cr2O3–Al2O3–ZrO2 bricks with the microstructure of Cr2O3 aggregates coated by ZrO2

Abstract

Abstract Zirconia-coated Cr2O3 aggregates synthesized by mixing ZrO2 powders and Cr2O3 aggregates with a phenolic resin binder followed by thermosetting treatment were employed as modified Cr2O3 aggregates to obtain Cr2O3–Al2O3–ZrO2 bricks (high-chromia bricks). The elastic modulus (E) and cold modulus of rupture (CMOR) of these high-chromia bricks before and after thermal shock cycles were systematically investigated, and the residual ratios of CMOR and E were calculated. The thermal shock resistance of the high-chromia bricks was significantly improved by the factor of modification of Cr2O3 aggregates. The mechanism of the improved thermal shock resistance of these high-chromia bricks was studied via microstructure analysis, and the crack propagation behavior was analyzed by scanning electron microscopy (SEM). The fracture work (γWOF), thermal shock damage factor (R′′′′), and thermal stress crack stability parameter (Rst) were measured and calculated using the wedge splitting test (WST). The results indicate that the porous ZrO2 coating layer wrapped the Cr2O3 aggregates, forming modified Cr2O3 aggregates that can increase crack deflection, free path of crack propagation, and fracture work, thus improving the thermal shock resistance of high-chromia bricks. The thermal shock resistance of the fabricated high-chromia bricks was highly correlated with the thickness of the ZrO2 coating layer surrounding the Cr2O3 aggregates. The variation trend of Rst is well consistent with the experimental results, which is suitable to evaluate the thermal shock resistance of high-chromia bricks.