Solid state interfacial reactions in a ceria-coated Ni-based superalloy

Abstract

Perovskite type phases are known to improve the adherence of protective oxide scales grown onto chromia- and alumina-forming alloys and coatings. The present study investigates the interfacial reactions occurring during the high temperature oxidation of a ceria coated Ni-based superalloy at 1100 °C. The substrate firstly grew a duplex oxide scale with a NiAl2O4 spinel on top of an α-Al2O3 scale underneath the ceria coating. Increasing oxidation time led to the development of Al-rich and Ce-rich nanometric grains at the oxide scale/coating interface and to the progressive vanishing of the NiAl2O4 spinel. Micro-Raman analyses demonstrated the formation of cerium aluminate CeAlO3 by solid-state reaction between Al2O3 and CeO2 favoured by an Al supply coming from the substrate. The results are in line with the thermodynamic calculations.