Publication Date:
2014-09-07
Description:
Based on the application of OB considerations (Part I) to various major thermal barrier coating (TBC) compositions and two types of important calcium–magnesium–alumino–silicates (CMAS)—desert sand and fly ash—the 2 ZrO 2 · Y 2 O 3 solid solution (ss) TBC composition, with high CMAS-resistance potential, is chosen for studying molten-CMAS/TBC interactions. It is demonstrated that 2ZrO 2 ·Y 2 O 3 (ss) air plasma sprayed (APS) TBCs are highly resistant to high-temperature attack by both sand-CMAS and fly-ash-CMAS. Despite the differences in the compositions of the two CMASs, the overall CMAS-attack mitigation mechanisms in both cases appear to be similar, viz reaction between 2ZrO 2 ·Y 2 O 3 (ss) APS TBC and the CMAS, and the formation of main reaction products of Y-depleted c - ZrO 2 and nonstoichiometric Ca – Y apatite. Large differences in the OBs (ΔΛ) between the 2ZrO 2 ·Y 2 O 3 (ss) and the CMASs are good predictors of ready reaction between this TBC and these CMASs. While the details of the CMAS-mitigation mechanisms can depend critically on various other aspects, the OB difference (ΔΛ) calculations could be used for the initial screening of CMAS-resistant TBC compositions.
Print ISSN:
0002-7820
Electronic ISSN:
1551-2916
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
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