Effect of Spray Method and Sprayed Material on Creep Behavior of MCrAlY Coating

Abstract

The blade of gas turbines used in combined cycle power plant are exposed to a high-temperature combustion gas. In order to protect it from such a harsh environment, a thermal barrier coating (TBC) is applied to the surface of the blade. TBC consists of a top coat (TC), which is a thermal barrier layer, and a bond coat (BC), which increases the adhesion strength between the TC and the substrate. Thermal stress is caused by the thermal expansion mismatch between the TC and substrate, which leads to delaminating in TC. In order to reduce such thermal stress in TC, creep deformability of BC is essential. In this study, we attempted to evaluate the creep deformation property of BC by creep indentation test method developed by our group. CoNiCrAlY and CoCrAlY are selected as BC materials and APS and HVOF are also as thermal spraying methods, and the creep indentation tests were conducted at various temperatures. It was found that material differences had little effect on creep deformation properties, and that creep properties were strongly affected by the thermal spraying method even if the material systems had the same chemical composition.