Damage Evaluation of Thermal Barrier Coatings Under High Temperature Low Cycle Fatigue Conditions

Document Type : Original Article

Authors

Asst. Prof. Dr., Anadolu University Civil Aviation School Turkey.

Abstract

Thermal Barrier Coatings (TBCs) are multi-layer protective coatings used in the hot section components such as combustor and turbine of advanced gas turbine engines to protect them from degrading effects of hot gases. Today, due to lack of a reliable life time assessment, the potential of these coatings cannot be fully used. Understanding of damage
mechanisms of thermal barrier coatings is the key factor to increase durability and reliability. In this paper TBCs have been shortly introduced and then damages resulting from high temperature low cycle fatigue tests and their probable reasons have been explained. Inconel 100, a directionally solidified nickel based superalloy as a substrate, approximately 120 μm thick NiCoCrAlY bond coat and approximately 200 μm thick 7 wt % Yttria Partially Stabilized Zirconia ceramic top coat have been used. Both layers are deposited by EB-PVD technique. The results of the tests show that number and size of the cracks changes with the strain range. Cracks initiate in the TGO/BC interface and propagate into the substrate
perpendicularly to the loading axes. Ceramic thermal barrier coating retards the formation of cracks. On the surfaces of the specimens having only bond coat, rumpling which is a typical service damage of turbine blades has been detected.

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