Reaction products of Sm2Zr2O7 with calcium-magnesium-aluminum-silicate (CMAS) and their evolution

Abstract

During flight, many silicates (sand, dust, debris, fly ash, etc.) are ingested by an engine. They melt at high operating temperatures on the surface of thermal barrier coatings (TBCs) to form calcium-magnesium-aluminum-silicate (CMAS) amorphous settling. CMAS corrodes TBCs and causes many problems, such as composition segregation, degradation, cracking, and disbanding. As a new generation of TBC candidate materials, rare-earth zirconates (such as Sm2Zr2O7) have good CMAS resistance properties. The reaction products of Sm2Zr2O7 and CMAS and their subsequent changes were studied by the reaction of Sm2Zr2O7 and excess CMAS at 1350 °C. After 1 h of reaction, Sm2Zr2O7 powders were not completely corroded. The reaction products were Sm-apatite and c-ZrO2 solid solution. After 4 h of reaction, all Sm2Zr2O7 powders were completely corroded. After 24 h of reaction, Sm-apatite disappeared, and the c-ZrO2 solid solution remained.

Progress in ceramic materials and structure design toward advanced thermal barrier coatings

“…The ceramic top coat in TBCs can be severely degraded by corrosion if molten deposits are introduced with the inlet air, although ceramic materials are usually resistant to corrosion. Such molten-deposit-induced corrosion has already been an important issue [19,247,248]. Degradation by molten salt deposits (especially alkaline sulfate-vanadate mixtures) was of early interest.…”

Evaluation of environmental barrier coatings: A review

“…Therefore, EBCs should prevent the invasion of these gases. Volcanic ashes or other kinds of salt dust have chances to enter into the high‐temperature region of the engine and add another severer chemical corrosion for EBCs and CMCs components 23,24 . The corrosion of chemicals at high temperatures is another difficulty for the design of EBCs.…”

Abnormal thermal expansion coefficients in (Nd1−xDyx)2Zr2O7pyrochlore: The effect of low-lying optical phonons

“…In recent years, rare-earth zirconates (RE2Zr2O7) have been identified as nextgeneration top coat materials with better phase stability, lower thermal conductivity, and better calcium-magnesium-aluminum-silicate (CMAS) corrosion resistance than the previously used 8 wt% yttria-stabilized zirconia (8YSZ) [8][9][10]. The thermal expansion coefficient of RE2Zr2O7 is approximately 9.6-11.0×10 -6 K -1 [11].…”