The development of modified chromium steels underwent a real boom in the last decade. Various ways how to improve creep resistance as well as corrosion resistance of the steel at temperatures at and above 600°C were tested. Increasing molybdenum and/or tungsten contents brings about the presence of increased delta ferrite and the precipitation of detrimental Laves phase and also M_6X phase. Compensating their ferrite forming effect by nickel seems to be unadvisable as nickel promotes M_6X precipitation and facilitates structural recovery. The most promising way how to improve the creep properties of the new generation chromium modified steels thus seems to be optimizing boron and nitrogen contents of the steel. In order to get the maximum precipitation strengthening, it is necessary to keep the ratio V:N_(AV) close to the stoichiometric line.
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