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Fig. 8-1 Comparison of newly developed Ni-Cr-W superalloy with existing high-temperature alloys

The kinetic energy of particles released in nuclear fission or fusion processes is high, ranging from a few MeV up to more than 10 MeV. This energy can be used to generate very high temperatures, and the higher the heat source temperature, the higher the thermal efficiency. In addition, various new applications are expected at high temperatures such as development of new materials and utilization of special chemical reactions. Therefore, materials are needed which are strong and durable at high temperatures. For this purpose, alloys containing nickel, chromium and tungsten as the basic component have been extensively studied, with special attention paid to the effects of a small amount of other systematically-added elements. A superalloy has been successfully developed which has the world's best high-temperature creep strength, while maintaining sufficient hot-workability. This alloy showed excellent strength in a creep test in which it was exposed to high temperatures under stress for a long period of time. It has also been shown that this alloy has a good balance of corrosion resistance, hot-workability and creep rupture strength. Based on its good formability at low and high temperatures, a seamless tube made out of this alloy was tested and showed satisfactory performance in service at 1,000 degrees cent. This superalloy is expected to be very useful not only as a component material for the next generation of high-temperature gas-cooled reactors, but also as a general purpose, high-temperature material for other, non-nuclear applications.

Reference H. Tsuji et al., Development of Ni-Cr-W Superalloy for Application to High Temperature Structures, Proc. Int. Conf. on Materials for Advanced Power Engineering, 939 (1994).

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