The carbide phase in grain and at grain boundary

microstructure and mechanical properties of heat resistant steel 5Cr21Mn9Ni4Nb2WN of status forged

status solution-treated at 1200 °C for 120 min water cooled

+ at 1030 °C for 20 ~ 240 min water cooled

and status solution-treated again at 1220 °C for 20 -240 min water cooled have been studied by scanning electron microscope ( SEM)

transmission electron microscope (TEM)

electron diffraction analysis ( EDA) and energy dispersive X-ray diffraction analysis (EDAX) etc techniques. Results show that with solid-solution-treated at 1030 °C

not only the granular (CN)

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precipitates in grain and at grain boundary of steel 5Cr21Mn9Ni4Nb2WN

but also as a addition of ca

rbon resource the M(CN) degenerates into (CN)

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the ambient impact energy of steel markedly decreases but the change of yield strength of steel is minor； with again solid-solution-treated at 1220 °C the reverse precipitation reaction from M

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(CN)

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to M(CN) occurs once more

and the higher ambient energy impact of steel shows again.