Research and development of ultra-high temperature materials in Japan (Reprinted from proceedings of High-Temperature Corrosion and Protection 2000)

Gas turbines for aircraft engine and power generation are typical fields of application of high temperature materials. Nickel-based superalloys are excellent and most useful materials for these applications and have been well developed especially with the outstanding progress of jet engines. In future, from a view point of global environmental problems, there will be strong demands for special materials for high temperature and high efficiency gas turbines for power generation. However, the temperature capability of the superalloys will saturate to some limit because of their melting points which are lower than 1400 degreesC. So-called ultra-high temperature materials, such as intermetallic compounds, refractory metals and alloys, ceramics, and various composite materials are expected to surpass the temperature capability of the superalloys, although these materials have several problems such as difficulty of processing, lack of ductility and toughness or the poor resistance to oxidation and hot-corrosion. In this paper, present and future prospects of R&D of these ultra-high temperature materials have been briefly reviewed.