Novel thermal barrier coatings that are resistant to high-temperature attack by glassy deposits

Airborne sand particles that deposit on thermal barrier coatings (TBCs) in gas-turbine engines melt and form calcium-magnesium-aluminosilicate (CMAS) glass, which attacks the TBCs. A new approach for mitigating CMAS attack on TBCs is presented, where up to 20 mol.% Al2O3 and 5 mol.% TiO2 in the form of a solid solution is incorporated into Y2O3-stabilized ZrO2 (YSZ) TBCs. The fabrication of such TBCs with engineered chemistries is made possible by the solution-precursor plasma spray (SPPS) process, which is uniquely suited for depositing coatings of metastable ceramics with extended solid-solubilities. Here, the TBC serves as a reservoir of Al and Ti solutes, which are incorporated into the molten CMAS glass that is in contact with the TBC. This results in the crystallization of the CMAS glass and the attendant arrest of the penetrating CMAS front. This approach could also be used to mitigate attack by other types of foreign deposits (salt, ash, and contaminants) on TBCs. (c) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.