Effect of Al2O3 Doping on Damping Properties of YSZ Coatings

In this paper, the changes in the microstructure and damping performance of x wt% Al-doped 8YSZ (xAl-YSZ, x = 0, 2.5, 5, 10, or 15) were investigated. Al-YSZ coatings with a thickness of about 80 lm were prepared on nickel-based alloys by means of EB-PVD. The surface morphology, phase composition and loss factor of the coatings were compared and analyzed by means of SEM, XRD, DMA, and SEM. XRD revealed that the grain size of the coating decreases, the preferred orientation changes to multi-orientation, and the diffraction peak intensity decreases. With reference to the DMA test results, it could be shown that doping an appropriate amount of Al(2)O(3 )improved the grain boundary density, while multi-orientation formed more interfaces and pores between grains, which makes the coating consume more energy as a result of internal friction under external load. Too much or too little doping was not conducive to improving the damping performance. The results indicate a direct influence of the Al2O3 content (up to 5 wt%) on the improvement of the damping performance.