Synchrotron x-ray measurements capturing thermally grown oxide behavior in thermal barrier coatings

Abstract

In-situ synchrotron x-ray diffraction was used to identify the mechanical behavior of thermal barrier coatings under extreme environments. Experiments were conducted on ceramic coatings deposited via electron-beam physical vapor deposition on a tubular Inconel 100 substrate. The ceramic top coat consisted of a 7-8% yttria stabilized zirconia (YSZ), which was adhered to the substrate via a NiCoCrAlY bond coat. The specimens were pre-aged at 1000 °C, developing the thermally grown oxide (TGO) layers to thicknesses representative of different stages of a coating lifespan. High-energy x-rays were used to measure lattice strains in these multi-layer coatings with through transmission diffraction. Experiments were conducted under various combinations of applied thermal gradients and mechanical loads to determine the effects of these conditions on stresses within TGO and YSZ layers. Larger applied tensile loads have shown the ability to cause tensile stresses in the TGO at high temperature. The experimental results capturing time and temperature dependent behavior has shown positive contributions that will support the creation of life prediction models.