Experimental Work on Alloy Development for High-Temperature Gas-Cooled Reactor Systems

In the context of developing high-temperature wrought alloys especially designed for advanced high-temperature gas-cooled reactor systems at temperatures up to 1000°C, a program of investigations has been performed during the past few years. The progress of the work can be traced through several stages:

1. the addition of single minor alloying elements to model Fe-Cr-Ni alloys
2. the study of multiple minor alloy additions in commercial alloys
3. the additions of preferred minor alloy combinations to modified commercial alloys
4. the variation of chromium in experimental nickel-base alloys containing titanium and aluminum
5. the variation of iron, molybdenum, tungsten, and cobalt in nickel-base alloys containing low chromium, titanium, and aluminum.

The first three stages were directed toward the study and improvement of the corrosion resistance of existing alloys, but in the last two stages, radical changes in composition have been investigated. The work so far has culminated in a family of alloys that have excellent microstructural stability and corrosion resistance combined with strengths comparable with those of traditional alloys.