Low cycle fatigue behaviors with nitrogen content and temperature in type 316L stainless steel

Strain controlled Low Cycle Fatigue(LCF) tests were conducted in the temperature range between R.T. and 600 .deg. C in type 316L stainless steels with different nitrogen contents. Fatigue life decreased and cyclic stress increased with increasing temperature due to Dynamic Strain Ageing(DSA) at the temperature range of 300∼600 .deg. C. The dislocation structures were changed from cell to planar by increasing effect of DSA and Short Range Order(SRO) with increasing temperature and nitrogen addition. Since nitrogen reduced the chromium diffusion coefficients, nitrogen retarded DSA, which resulted in decrease in LCF life at high temperature. So, fatigue life increased with nitrogen addition due to the retardation of DSA and planar slip by SRO