Fossil energy applications of intermetallic alloys

This paper presents the history and results of the US Department of Energy, Office of Fossil Energy (FE), development effort on iron aluminide alloys and the status of research and development on ultrahigh temperature (well a bove 1000 degrees C) intermetallic alloys. The outstanding (perhaps unequal ed) sulfidation resistance of iron aluminide alloys, based on the Fe3Al com position, was the basis for initiation of an exploratory project to determi ne whether improvement in mechanical properties of iron aluminide alloys co uld be achieved. This was a high-risk venture but with significant payoff i f successful, because sulfidation was a critical problem for applications o f alloys in coal gasification systems. The exploratory project, which was c onducted at Oak Ridge National Laborator (ORNL), was successful, and the pr ogram was expanded in both scope and participation. Several other national laboratories, industrial research organizations, and universities were invo lved. Iron aluminide development is now quite mature. Some of the research has transferred to line programs leading to product that will be used in ad vanced fossil energy systems. The first product to be commercialized for fo ssil energ applications was a porous metal filter developed jointly by ORNL and Pall Corporation. In addition to th coal gasification application, the se filters are also being used in combustion systems. Several other commerc ial products are being pursued. Additional exploratory projects on intermet allic alloys have been initiated. These are also high risk activities, but, as with the iron aluminides, the payoff potential is great. The intermetal lic alloys presently being investigated include a Cr2Ta-strengthened chromi um alloy and a boron-modified molybdenum silicid based on Mo5Si3 The challe nges with these alloys are to modify them to provide acceptable mechanical properties, including ductility and toughness, and corrosion resistance to allow them to be used in structure applications such as gas turbines. (C) 2 000 Elsevier Science Ltd. All rights reserved.