Crystallization behavior of CMAS and NaVO3+CMAS mixture and its potential effect to thermal barrier coatings corrosion

Calcium-magnesium-alumina-silicate (CMAS) and molten salt corrosion pose great threats to thermal barrier coatings (TBCs), and recently, a coupling effect of CMAS and molten salt has been found to cause even severer corrosion to TBCs. In this study, the crystallization behavior of CMAS and CMAS+NaVO3 is investigated for potentially clarifying their corrosion mechanisms to TBCs. Results indicated that at 1000 °C and 1100 °C, CMAS was crystallized to form CaMgSi2O6, while at 1200 °C, the crystallization products were CaMgSi2O6, CaSiO3 and CaAl2Si2O8. The introduction of NaVO3 in CMAS reduced the crystallization ability, and as the NaVO3 content increased, glass crystallization occurred at a lower temperature, with crystallization products mainly consisting of CaAl2Si2O8 and CaMgSi2O6. At 1200 °C, CMAS+10 wt% NaVO3 was in a molten state without any crystallization, which suggested that NaVO3 addition in CMAS could reduce its melting point, indicating enhanced penetration ability in TBCs and thus increased corrosiveness.