Chromium-molybdenum steels for fusion reactor first walls — a review

Abstract

Chromium-molybdenum steels have recently become of interest as a first wall and blanket structural material for fusion reactors. This application will be assessed, and possible approaches on how CrMo alloys may be further developed for this application will be proposed. Generally, the CrMo steels can be divided into two categories: unmodified, basically CrMoC steels and CrMoC steels modified by the addition of carbide-forming elements. Extensive research and development efforts have been conducted on the unmodified steels, especially 2 1 4 Cr-1 Mo and 12 CrMo steels. Considerable work has also been done on 12 CrMo steels modified with additions of V, Nb, Ti and W. In recent years much of the research effort on this type of alloy has been directed at developing modified CrMo steels with less than 12% Cr (generally ⩽9%) for applications where the “stainless” properties imparted by chromium additions of at least 12% are not needed. We will examine the unmodified and modified steels in terms of hardenability, precipitation processes (stability at elevated temperatures), strength, and toughness. Where possible, we will discuss the effects of irradiation on these properties. Such a study leads to the types of tradeoffs that may be necessary between the well-researched unmodified 2 1 4 Cr-1 Mo steel and a high-chromium modified steel.