Short-time oxidation of a NiAI(Zr) bond coat thermochemically deposited on a nickel-based superalloy

摘要

Thermal barrier systems, used for turbine blades, are made of a nickel-based superalloy, a nickel aluminide bond coat layer and a ceramic thermal barrier. The aim of the present work is to study the initial stages of oxidation of the AM1/NiAl(Zr) system. It is currently of prime importance to characterize the initial thin oxide layer that covers the bond coat prior to the topcoat deposition. Indeed, the adhesion of the thermal barrier layer and the lifetime of the system are partly influenced by the substrate pre-heating oxidizing treatment. In order to determine the contribution of zirconium during this intermediate temperature range oxidation, the AM1/NiAl(Zr) system was heat treated at 950°C. in two vacuum conditions, that were close to the industrial ones. The compositions of the extreme surface of the nickel aluminide and of the thermally grown oxide were investigated by X-ray photoelectron spectroscopy. In particular, these experiments allowed us to detect zirconium at the surface of the system and to determine its oxidation state.