C and N Atom Redistribution Behaviors in 0.30C-15.0Cr-1.0Mo-0.50N Martensitic Stainless Steel During Cryogenic Treatment

The redistribution of C and N interstitial atoms i n a martensitic stainless steel combined alloying with 0.3 wt.% C and 0.5 wt.% N after cryogenic treatment was investigated by the transition electronic microscope (TEM), X-ray diffractometer (XRD), and atom probe tomography (APT). C atoms accumulated to form clusters which were enhanced by the decrease of cryogenic temperature. N atoms as Mo-N and Cr-N pairs were found when the cryogenic temperature was deep to -190 o C. It seems that the redistribution behavior of C and N atoms is considerably different, and these interstitial atoms migrated more strenuously despite of the cryogenic temperature decreasing. The migration of interstitial atoms is supposed to associate with the microstructure evolution combining the increase of dislocation density and the martensite transformation from the retained austenite during cryogenic treatment.