High temperature corrosion of silicon nitride composite ceramics in sulfur-oxygen environments

摘要

High temperature corrosion behavior of Si 3N 4 8%Al 2O 3(volume fraction) composite ceramics in sulfur oxygen environments was studied. At 1 150 ℃ and 1 350 ℃,the corrosion processes follow parabolic law with parabolic rate constants ( K p) of 1.45×10 -9 g 2·cm -4 ·s -1 and 7.92×10 -9 g 2·cm -4 ·s -1 , respectively. The corrosion mechanisms are different at different temperatures. At 1 150 ℃, the corrosion of the material is due to the destruction of SiO 2 layer caused by sulfur and the active oxidation corrosion. At 1 350 ℃ , the diffusion of additives and impurity elements to grain boundaries and outward to surface layers lead to the formation, growth and break of bubbles, which accelerates the corrosion rate of the Si 3N 4 ceramics.