Interdiffusion behaviour in aluminide-coated Rene 80H at 1150 degrees C

The hot-section components in commercial aero gas turbines are typically made of a nickel-base superalloy and are protected by a diffusion-aluminide coating. At elevated temperatures this alloy/coating system is metastable and, as a consequence, microstructural changes occur. The extent to which these changes occur is critically dependent upon temperature and time. In the case of overheating, where the component temperature exceeds about 1100 degrees C, the microstructural changes are often extensive enough to cause a decrease in both the strength and protectiveness of the alloy/coating system in a relatively short period of time. This paper reports the effects of overheating on the microstructural changes that occur in an aluminide-coated; nickel-base superalloy, Rene 80H. The overheating condition was simulated by isothermally heating at 1150 degrees C for up to 167 h. Both the alloy/coating interdiffusion kinetics and the time-dependent phase changes resulting from interdiffusion are discussed. The interdiffusion behaviour is complex and requires the application of diffusion paths for proper interpretation. (C) 1997 Elsevier Science S.A.