M2N nitride phases of 9% chromium steels for nuclear applications

Identification of precipitate phases in a 11Cr ferritic/martensitic steel using electron micro-diffraction

“…The average composition in atomic pct of the metal fraction in the examined Cr-rich M 2 (C,N) precipitates was about 80.07Cr, 15.44V, 0.42Nb, 1.18Fe, 1.16Mo, 1.71W, which was similar with 79.2Cr, 17.3V, 1.9Fe, 0.9Mo, 0.7W and 82.8Cr, 14.2V, 1.0Nb, 0.4Fe, 1.6Mo for Cr-rich M 2 N nitride phase in tempered (750°C/2 h) 9% chromium steels with extra-low carbon (<0.003C, in wt.%) [11]. Thus, the typical chemical formula of Cr-rich M 2 (C,N) phase in the present steel can be expressed as (Cr 0.8 V 0.2 ) 2 (C,N) approximately.…”

Influence of tempering temperature upon precipitate phases in a 11%Cr ferritic/martensitic steel

“…It can be seen clearly that the content of vanadium and tungsten in the precipitate was increased and decreased with tempering temperature, respectively, meanwhile the general trend of chromium content in the precipitate maintained without significant changes with increasing tempering temperature. The present results show some differences compared with the results that with increasing the tempering temperature from 600 to 780°C, chromium content was decreased, whereas vanadium content was increased, and there was no obvious change in the content of tungsten in the M 2 N precipitate phase in a 9%Cr F/M steel [18], as well as that the content of chromium was increased in chromium-rich M 2 X phase in a 5%Cr heat resistant steel as the tempering temperature was increased from 600 to 700/or 750°C [19]. Since chromium-rich M 2 (C,N) precipitate phase in the steel specimens underwent a coarsening progress during the tempering with the increasing in temperature, which can be seen clearly from Table 1, the composition of the precipitate phase changed with increasing tempering temperature.…”

Precipitate phases in normalized and tempered ferritic/martensitic steel P92

“…Since precipitate types may mainly depend on tempering temperature and the chemical composition of steels, there is somewhat difference in precipitate phases in tempered 9À12%Cr F/M steels reported previously. It has also been reported that the microstructure of 9e12% Cr F/M steels normalized at 1050e1100 C (1323e1373 K) and tempered at 770e780 C (1043e1053 K) reveals tempered martensite, which consists of small ferrite subgrains with a high density of dislocations, M 23 C 6 and MX precipitates [6], as well as M 2 X precipitates in some cases [7,8].…”