Microstructure and precipitation behavior of advanced RAFM steels for high-temperature applications on fusion reactors
P. Fernández, J. Hoffmann, M. Rieth, A. Gómez‐Herrero
Abstract
The composition of new eigth 9% Cr reduced activation ferritic/martensitioc steels (RAFMs) has been finely tuned in order to increase the amount of fine MX precipitates and reduce coarse M23C6 carbides through the application of thermomechanical treatments. The microstructural investigations by TEM/STEM and EELS have shown M23C6, M2X (Cr2N), and MX (Ta, V, and Ti-rich) precipitates after tempering at 750 °C/2 h. Higher N contens (0.04–0.03 wt%) seems to favored M2X precipitation over MX with V contents round 0.2 wt%. MX-Ti rich presents sizes larger than MX (Ta or V rich). EELS anlysis have shown that the MX (Ta, V and Ti rich) precipitated after tempering at 750 °C/2 h are mainly carbo-nitrides. Composition, size, number density and carbon and nitrogen content on MX and M2X is discussed in terms of the composition of each Alloy.