Vibration damping of superalloys and thermal barrier coatings at high-temperatures

A high-temperature mechanical spectroscopy system, based on non-contact laser vibrometry, has been developed to investigate the temperature dependence of the flexural damping properties of materials and coatings up to 900 °C. Results for the damping coefficient and Youngʹs modulus have been obtained for several high temperature alloys (FeCrAlY and a single crystal, Ni-based superalloy PWA 1484), ceramics (polycrystalline alumina and yttria-stabilized zirconia) and an electron-beam deposited thermal barrier coating. The results indicate that the thermally grown oxide, formed by high-temperature oxidation does not confer significant damping, whereas, coatings of the yttria-stabilized zirconia produce measurable damping over the entire temperature range with a peak centered at ~200 °C. The damping peak appears to be an intrinsic property of the YSZ material whether in the form of a bulk material or a metastable coating. Data on the temperature dependent in-plane Youngʹs modulus of the 7 wt.% yttria-stabilized zirconia thermal barrier coating between room temperature (22 GPa) and 900 °C (18 GPa) is also reported for the first time.