Investigation of Fatigue Behavior of a Thermal Barrier Coating System

In this dissertation, fatigue behavior of a thermal barrier coating system applied to the turbine blades of gas turbine aero-engines is investigated. An experimental study on the isothermal high temperature low cycle fatigue (HTLCF) properties of a thermal barrier coating system and the results of this experimental study is presented. Investigated TBC system consists of a directionally solidified nickel based superalloy IN 100 DS substrate, a yttria partially stabilized zirconia (YPSZ) ceramic top coat and a NiCoCrAlY metallic bond coat. Both layers are applied by Electron Beam Physical Vapor Deposition (EB-PVD) method. Damages on test specimens are investigated in terms of mechanical stress, number of cycles, the effect of thermal barrier coating and time at high temperature. The macro and microstructural changes in the specimens are described by means of various characterization techniques such as Scanning Electron Microscope (SEM), Energy Dispersive X-ray Analysis (EDX), X-ray Diffraction (XRD), Optical Microscope (OM) and Infrared Imaging (IR) and by comparison of previous studies in the literature