Residual Stress in TGO and Interfacial Damage in Thermal Barrier Coating after Thermal Exposure and Cyclic Indentation

Abstract

The purpose of this study was to understand interface damage mechanism of Thermal barrier coating (TBC) systems. The TBC systems used as testing specimens consisting of 8 wt% yttria stabilized zirconia (ZrO 2-8 wt% Y 2O 3) top coat by atmospheric plasma spraying and NiCoCrAlY alloy bond coat by low-pressured plasma splaying on a Ni based superalloy (Inconel 738). The local stress distributions in thermally grown oxide (TGO) layer of thermal barrier coating before and after thermal exposure were measured by photo-stimulated luminescence spectrum. The effect of isothermal oxidation on the residual stress in the TGO was investigated. It was found that the compressive stress in the TGO increased with an increase in thermal exposure time up to 100 hours and then decreased. The residual stresses in the TGO were also influenced by interfacial damage introduced by cyclic indentation.