Hf and Ta co-doping MCrAlY alloy to improve the lifetime of coatings

Abstract

Thermal barrier coating (TBC) is one of the key components of an aircraft turbine or stationary gas turbine. NiCoCrAlY is the most commonly used bond coat (BC) and its composition and impurities have an impact on the lifetime of the TBC. However, the performance of NiCoCrAlY is very unstable due to the influence of impurities. Reactive elements (RE) Hf and Ta are co-doped into the bond coat to improve the adhesion of thermally grown oxide (TGO) layers to extend the lifetime of TBC. Yttrium stabilized zirconia (YSZ) is sprayed on free-standing alloys of NiCoCrAlY and NiCoCrAlYHfTa, respectively. The samples are cyclically oxidized at 1050 °C until the peeling off of coatings. The lifetime of NiCoCrAlY coatings is only 240 h, while the lifetime of NiCoCrAlYHfTa coatings reaches 2664 h. The morphology and structure of the oxide scale are characterized to study the mechanisms of lifetime extension.