Bond coat (BC) surface rumpling has been identified as one of the important mechanisms that can lead to failure of the thermal barrier coatings. The driving force behind rumpling—whether the stresses in the thermally grown oxide over the BC or the stresses in the BC—remains to be clarified. Meanwhile, the mass transport mechanisms in the BC leading to rumpling are not clearly identified. In the present investigation, we subject two types of BC-superalloy systems, nickel aluminide and platinum aluminide BCs on a Ni-based superalloy, to isothermal exposure at temperatures ranging from 1150 to 1200°C in vacuum. The results show that the nickel aluminide BC rumples at 1200°C and at 1175°C in absence of significant oxidation. The wavelength of the rumpled surfaces was 60–100 µm, with an amplitude of 5–8 µm. The rumpling was insensitive to the initial BC surface morphology. At 1150°C, no clear rumpling was observed, but some surface undulations could be seen related to the BC grains. ...[more]...published or submitted for publicationis peer reviewe
