Chemical and morphological evolution of a (NiPt)Al bondcoat

International audienceExperimental results are reported on the chemical and microstructural evolutions of a (NiPt)Al coating, deposited on a single-crystal, nickel-base superalloy, during isothermal-oxidation tests at 1100°C, up to 50 hr. Analytical STEM studies were carried out, in conjunction with Auger experiments, in order to follow the various changes that occur in the bondcoat (β into γ′ phase transformation, TCP and α-Cr precipitation, S-diffusion pathways) and at the Al2O3/bondcoat interface. Efforts were concentrated on the effect of interfacial sulfur segregation (at both intact interfaces and void surfaces) as a function of the oxidation time and its dependence on phase transformations in the external layer of the bondcoat. An important result concerning the co-segregation of S and Cr at the alumina/bondcoat interface was realized in this system due to Cr diffusion from the substrate into the bondcoat. This S segregation adversely affected Al2O3-bondcoat adhesion where extensive interfacial voids formed at the interface