Effect of MCrAlY Bond Coat Temperature on Thermal Cyclic Lifetime of Plasma-Sprayed Thermal Barrier Coatings

Abstract

Abstract Gradient thermal cycling test was performed on atmospheric plasma sprayed (APS) thermal barrier coatings (TBCs) to examine the influence of the bond coat temperature on the thermal cyclic lifetime. The TBC system consisted of Inconel 738 substrate, cold-sprayed NiCoCrAlTaY bond coat (BC) and plasma-sprayed yttria-stabilized zirconia (YSZ) top coat. Every thermal cycling test included 70s heating, 50s holding and 120s cooling. The temperature of top YSZ surface was about 1150 °C, while the bond coat temperatures were 900°C, 950°C and 1000°C, respectively. Results indicated that the lifetime of APS TBCs is significantly affected by bond coat temperature. A model to predict the relative thermal cyclic lifetime of TBCs at different bond coat temperature was established by taking account of main factors affecting the lifetime of TBCs. It was found that the predicted results are consistent with the observed results. As a result, the change of lifetime of APS TBCs mainly depends on the growth rate of thermally grown oxide (TGO), elastic modulus of YSZ and thermal expansion mismatch difference between YSZ and substrate caused by different bond coat temperature.