Adhesion behavior of calcia-magnesia-alumino-silicates on gadolinia-yttria-stabilized zirconia composite thermal barrier coatings

Military operations occurring in particle-laden environments have resulted in aircraft incidents and loss of life due to sand ingestion into the engine. Sand melts in the hot combustion environment and deposits as glassy calcia-magnesia-alumino-silicates (CMAS) which leads to rapid performance degradation due to clogged air pathways in the engine. A novel, composite thermal barrier coating (TBC) consisting of yttria-stabilized zirconia (YSZ) blended with gadolinia is proposed that combines the excellent thermo-mechanical properties of YSZ together with the CMAS resistance of rare-earth oxides. YSZ was blended with 2, 8, 17, and 32 vol% gadolinia and tested under simulated engine-relevant conditions. The presence of gadolinia in the composite coating reduced the adhesion of the CMAS, and at 32 vol% gadolinia addition, the CMAS was completely delaminated. A possible CMAS adhesion mitigating mechanism is discussed. This work demonstrated the capability of a new composite TBC to significantly reduce CMAS adhesion.