Improving the strength, ductility and toughness of martensitic stainless steels via nanoscale carbonitrides

The precipitate characters and mechanical properties of martensitic stainless steels with various carbon/nitrogen combinations have been studied. The results indicated that co-addition of carbon and nitrogen could enhance the strength, ductility and toughness simultaneously, compared to the steel alloyed with carbon or nitrogen solely. According to TEM and APT results, high density nanoscale V(C,N) has been identified as the dominant precipitate in steel with co-addition of both carbon and nitrogen. However, a mass of bridged rod-like Cr 2 C or Cr 2 N precipitates were discovered in the steels with only carbon or nitrogen addition. Compared to rod-like Cr 2 X precipitates, disperse nanoscale V(C,N) precipitates could facilitate precipitation hardening and continuous work hardening effect, which contributes to both uniform plastic deformation and crack tip blunting in the fracture process.