Strain controlled fatigue deformation and fracture of nitrogen alloyed 316LN austenitic stainless steel

摘要

In this paper, Low cycle fatigue (LCF) behavior of 316LN austenitic stainless steel alloyed with 0.078 and 0.22 wt% nitrogen, designated as N078 and N022 steels respectively, is compared in the temperature range 300–873 K by strain controlled fatigue tests at ± 0.6% strain amplitude. Interestingly, N022 steel showed continuous decrease in fatigue life with temperature in contrast to N078 steel which showed maximum in fatigue life at 573 K. Drastic reduction in fatigue life is observed in both the steels in the temperature range 673–873 K and has been attributed to the occurrence of dynamic strain aging. Both steels exhibited manifestations (for ex.: decrease in plastic strain and anomalous stress response with increase in temperature) corresponding to the occurrence of Dynamic Strain Ageing (DSA) in the above temperature range. Under all testing conditions, fracture surfaces revealed transgranular crack initiation and transgranular crack propagation.