CMAS corrosion resistance characteristics of RE50TaxZr50-xO175+0.5x thermal barrier oxides in RE2Zr2O7-RETaO4 systems
(School of Materials Science and Engineering, Xiangtan University, Xiangtan 411105, China)
Abstract: The corrosion resistance characteristics of RE-rich RE50TaxZr50-xO175+0.5x oxides in RE2Zr2O7-RETaO4 systems to calcium-magnesium-alumino-silicate (CMAS) at 1300 °C, and the influence of RE3+ and Ta5+ on chemical reactions and reactive crystallization of CMAS melts were investigated. The results show that following the thermochemical reactions, apatite, pyrochlore, reprecipitated fluorite and residual Yb(Y)TaO4 phases were the predominant reaction products. Formation abilities of apatite and pyrochlore were found to be proportional to the ionic radius of RE3+. The increase of Ta5+ amount can decrease the number of available RE3+ to form apatite. Moreover, the resistance characteristic to CMAS corrosion in RE50TaxZr50-xO175+0.5x systems was decided by the combined action of apatite and pyrochlore phases. The cohesive mixture of apatite and pyrochlore phases can generate a dense layer near the reaction front, which had a positive effect on suppressing CMAS infiltration. The ability of the fluorite + RETaO4 two-phase field was determined to be sufficient to mitigate CMAS corrosion.
Key words: thermal barrier coatings; CMAS corrosion; thermochemical reaction; apatite; pyrochlore; penetration experiment