Microstructure and thermal barrier coating properties of plasma sprayed SrCeO3

Abstract

The trend to improve the efficiency of gas turbine engines leads to an increase in requirements for thermal barrier coating (TBC) materials. Strontium cerate (SrCeO3) is a promising perovskite-like type oxide with a low thermal conductivity and moderate thermal expansion coefficient (TEC) value. In this work, TBC was applied by atmospheric plasma spraying to a nickel superalloy ZhS 32 VI, and the change in its microstructure and phase composition after thermal cycles was investigated. It was found that during spraying, SrCeO3 crystals orientated along the most densely packed directions, which led to the structuring of the coating. In the process of thermal cycling, Sr diffuses to the top coat – bond coat boundary with the formation of strontium chromate. SrCrO4 together with NiO form a layer of thermally grown oxide (TGO). TBC failed after 44 ± 3 thermal cycles of rapid heating up to 1200 °C followed by air cooling with 5 min of holding time at each stage. The absence of direct reactions of the top coat and bond coat, the TGO formation from components of both layers as well as low TEC mismatch allows to resist onset of exfoliation for about 30 cycles. The thermal conductivity value of nickel superalloy covered by SrCeO3 is only 1.65 ± 0.05 W·m−1·K−1 in the temperature range of 25–100 °C and mainly determines by top coat properties. The new experimental data being obtained highlights the prospects of the considered TBC based on SrCeO3.