High temperature indentation tests of YSZ coatings in air up to 1200 °C

In this paper, high temperature indentation tests in air up to 1200 °C were firstly conducted to measure hardness and elastic modulus of nanostructured 8 wt% yttria partially stabilized zirconia (YSZ) coatings. An in-house constructed elevated temperature indentation apparatus was developed. The load-displacement curves of YSZ coatings testing at 25, 1000 and 1200 °C were obtained. Hardness and elastic modulus were evaluated from the load-displacement curves. It is found that the value of hardness and elastic modulus both decrease with increasing temperature. This may be attributed to the enhanced plasticity of YSZ coatings at high temperatures. The microphotographs of residual indentation impressions also show that plastic deformation tends to occur with increasing temperature.