Isothermal Oxidation Behaviour of Thermally Sprayed Nickel Foam Structure

Isothermal Oxidation Behaviour of Thermally Sprayed Nickel Foam Structure S. Yugeswaran, Thomas W. Coyle, Larry Pershin, Javad Mostaghimi Centre for Advanced Coating Technologies, University of Toronto, Toronto, Canada Nickel foams are widely used for different kinds of engineering applications due to their excellent physical and mechanical properties. Recently, our group has been investigating sandwich structures for high temperature applications, like heat exchangers, fabricated by thermally spraying skins on the surfaces of nickel foams. In this investigation, in order to examine the oxidation behaviour of this type of sandwich structure, isothermal oxidation tests were performed at 700°C and 1000°C for about 200 h. For this purpose, nickel foam (10 ppi) structures were sealed by a YSZ top coat and Alloy-625 bond coat by atmospheric plasma spraying. Scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) was employed to analyse microstructures and element distribution in the coatings and foam struts before and after oxidation. Oxidation kinetics were characterized by measuring the weight change versus time. Compression tests were performed on the oxidized sandwich structures and the results are correlated to the oxidation behavior.