Failure and Protection of Thermal Barrier Coating under CMAS Attack

Abstract

Along with the increase of operating temperature of aero-engine, thermal barrier coatings （TBCs） used in the engine are highly susceptible to the attack of glassy silicate deposits, the chemical composition of which is mostly CaO-MgO-Al2O3-SiO2 （CMAS）. The deposition of CMAS on TBCs tends to cause blocking of cooling holes in turbine blades, which results in decrease of cooling efficiency, change of temperature and stress distribution in blades. On the other hand, the durability of TBCs is significantly reduced due to the CMAS deposition. It is very important to make the strategy to constrain the absorption and infiltration of glassy CMAS on TBCs at high temperature to ensure the development of advanced aero-engine. In this paper, the failure mechanisms of TBCs which are thermochemistry, densification and phase transformation caused by CMAS are summarized, and the solutions to CMAS, such as coating structure optimization, adding permeability barrier layer and sacrificial layer are briefly overviewed.

Keywords

• thermal barrier coatings (TBCs)
• CaO-MgO-Al₂O₃-SiO₂ (CMAS)
• failure mechanisms
• protection