Protective Al-rich mullite coatings on Si- based ceramics against hot corrosion at 1200 degrees C

作者：Kulkarni Tushar^*; Wang H Z; Basu S N; Sarin V K

来源：Surface and Coatings Technology, 2011, 205(10): 3313-3318.

DOI：10.1016/j.surfcoat.2010.11.055

• Ceramics
• Composites
• Electron microscopy

The hot-corrosion behavior of uncoated SiC, bulk mullite and CVD grown mullite coatings in contact with Na(2)SO(4) were investigated at 1200 degrees C. The range of thermodynamic activity of Na(2)O (10(-4) to 10(-6)) simulated in this study makes the oxide very basic leading to high reaction rates with SiO(2). Uncoated SiC corroded severely, forming various Na(2)O center dot SiO(2) compounds with a significant weight gain. Even though the thermodynamic activity of silica is reduced in mullite, several compounds in Na(2)O center dot SiO(2)center dot Al(2)O(3) system were formed in case of bulk mullite. CVD based mullite coatings with high alumina content at the top surface of the coating, and therefore reduced SiO(2) activity, offered protection to the underlying SiC in corrosive environments. As predicted correctly by thermodynamic calculations, the trend in weight gain with the coated SiC samples followed the theoretically calculated SiO(2) activity in Al-rich mullite.

• 出版日期2011-2-15