Fatigue and Structural Changes of High Interstitial Stainless Austenitic Steels

Abstract

Steels with 18 to 19 mass% Cr and Mn each were studied in the as-cast condition containing 0.85 mass% C þ N and in the elektro-slag-remelted and hot worked condition containing 0.96 mass% C þ N after final solution annealing. The latter was also tested after 20% prestraining. The results of tensile tests were compared to those of rotating bending and push/pull loading. The higher C þ N content raised the 0.2% proof strength to about 600 MPa of which 70% were retained as fatigue limit of rotating bending at 10 7 cycles and a failure probability of 50%. Prestraining further improved this limit but lowered it in relation to the proof strength. The structural components of cold work hardening under unidirectional loading and cyclic loading were similar (planar slip, dislocation, twins and e-martensite) except for precipitates in the latter. Nitrides appeared in the austenite and carbides in the e-plates.

The influence of the nitrogen/nickel‐ratio on the cyclic behavior of austenitic high strength steels with twinning‐induced plasticity and transformation‐induced plasticity effects

“…In general such steels show a cyclic hardening behavior, while the CrMnCn steels always exhibit planar slip and cyclic softening [9]. Still recently developed CrMnCN steels also bring about a higher fatigue limit, which could even be further improved by 20 % cold-working [12][13][14][15]. With these so-called austenitic high interstitial steels both carbon and nitrogen are of similar importance for all properties depending on the sum of carbon + nitrogen and its ratio carbon/nitrogen [16].…”

Experimental Quantification of the Austenite‐Stabilizing Effect of Mn in CrMnNi As‐Cast Stainless Steels

“…To obtain a metastable austenite at a given Cr‐equivalent, it is essential that the Ni‐equivalent value is just above the line which separates the single‐phase austenite region from the austenite + martensite phase region of the Schaeffler‐diagram. The advantage of metastable austenitic steels is then their superior cold formability with a possible contribution to the strength and ductility caused by the occurrence of TRansformation‐Induced Plasticity and/or TWinning‐Induced Plasticity (TRIP/TWIP) mechanisms …”

Microstructural changes in high interstitial stainless austenitic steels due to ballistic impact

“…After repeated impacts by wear particles of 25 m/s velocity the deformation turned the microstructure into nanocrystals and an amorphous layer at the wear surface [11]. Cyclic push/pull deformation entailed the precipitation of fine Fe 2 N particles [12]. The only additional deformation feature of the present study is the bands of localised slip (Figs.…”