High temperature corrosion of silicon nitride composite ceramics in sulfur-oxygen environments
(1. Key Laboratory of Liquid Structure and Heredity of Materials,
Ministry of Education, Shandong University, Ji＇nan 250061, China;
2. Key Laboratory of Engineering Ceramics, Shandong Province,
Shandong University, Ji＇nan 250061, China)
Ministry of Education, Shandong University, Ji＇nan 250061, China;
2. Key Laboratory of Engineering Ceramics, Shandong Province,
Shandong University, Ji＇nan 250061, China)
Abstract: High temperature corrosion behavior of Si3N4-8%Al2O3(volume fraction) composite ceramics in sulfur-oxygen environments was studied. At 1150℃ and 1350℃, the corrosion processes follow parabolic law with parabolic rate constants (Kp) of 1.45×10-9g2·cm-4·s-1 and 7.92×10-9g2·cm-4·s-1, respectively. The corrosion mechanisms are different at different temperatures. At 1150℃, the corrosion of the material is due to the destruction of SiO2 layer caused by sulfur and the active oxidation corrosion. At 1350℃, 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 Si3N4 ceramics.
Key words: Si3N4 composite ceramics; sulfidation; oxidation; corrosion