Effect of micro-Al₂O₃ powders on oxidation and corrosion behaviors of low-carbon MgO–C refractories

To solve the problem of poor high-temperature service performance caused by low carbonization of MgO–C refractories, low-carbon MgO–C refractories with excellent thermal shock, oxidation and corrosion resistances were successfully designed by using SiC whiskers as reinforcing phases and introducing micro-Al₂O₃ powders as additives. The results indicated that the addition of micro-Al₂O₃ powders optimized the internal structure of the material, like the columnar β-Si₃N₄ with a stepped distribution and the mosaic structure formed between granular and flaky Mg₂SiO₄, which synergistically strengthened and toughened the material and gave the material excellent mechanical properties and thermal shock resistance. Specifically, the cold modulus of rupture and cold crushing strength after thermal shock were increased by 4.1 and 20.3 MPa, respectively. Moreover, the addition of micro-Al₂O₃ powders promoted the formation of fine particles of Mg₂SiO₄, MgAl₂O₄ and MgO, as well as a dense protective layer of Mg₂SiO₄ in the material under high-temperature environment. Furthermore, spinel and high-temperature solid solution were formed in the corrosion environment. The oxidation and corrosion resistances were greatly improved by 41% and 15%, respectively.