Precipitation characteristics and effect of nitrogen in superaustenitic Fe-22Cr-21Ni-6Mo-(0.3N) stainless steels

摘要

The effect of nitrogen on the precipitationcharacteristics of superaustenitic Fe-22Cr-21Ni-6Mo-(0.3N)stainless steels was investigated by means of X-ray diffraction andmicrostructural observations such as SEM and TEM. The sigmaphase and M26C6 carbide were recognized in all specimensregardless of their heat treating condition. In case of nitrogen-freespecimen, four phases such as σ, M23C6, M6C and χ phaseswere formed by aging treatment after solutiontreatment. However, two more nitrides such as Cr2N andAIN were recognized by long time aging in the nitrogencontaining specimen. The addition of nitrogen intosuperaustenitic Fe-22Cr-21Ni-6Mo steel markedlyretarded the coarsening of precipitates and promotedhomogeneous distribution of precipitates duringisothermal aging. The orientation relationshipsbetween the matrix and the precipitates formed duringtreatment were also elucidated.