Novel Thermal Barrier Coatings (Tbcs) That Are Resistant To High Temperature Attack By Cao-Mgo-Al2o3-Sio2 (Cmas) Glassy Deposits

Abstract

Higher performance and durability requirements of gas-turbine engines will require a new generation of thermal barrier coatings (TBCs).This is particularly true of engines operated at higher temperatures, where TBCs are subjected to attack by CaO-MgO-Al 2 O 3 -SiO 2 (CMAS) glassy deposits.In this work, a new approach for mitigating CMAS attack on TBCs is introduced, where up to 20 mol% Al 2 O 3 and 5 mol% TiO 2 in the form of a solid solution is incorporated into Y 2 O 3 -stabilized ZrO 2 (YSZ) TBCs.The fabrication of such TBCs with engineered chemistries is made possible by the solutionprecursor plasma spray (SPPS) process, which is uniquely suited for depositing coatings of metastable ceramics with extended solid-solubilities.In the current work, 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.An accumulation of Al concentration in the CMAS glass as it penetrates the TBC shifts the glass composition from the difficult-to-crystallize psuedowollastonite field to the easy-to-crystallize anorthite field.The incorporation of Ti in the glass promotes crystallization of the CMAS glass by serving as a nucleating agent.