Research on Fatigue Crack Growth Behavior of 316LN Stainless Steel by Direct Current Potential Drop Method

Fatigue crack growth rates of 316LN stainless steel at room temperature and 350 ℃ were measured by the direct current potential drop (DCPD) method, and then the fatigue-crack growth threshold (ΔKth) at room temperature and 350 ℃ was obtained. The fatigue fracture morphology was also analyzed. The results show that the ΔKth obtained by the DCPD method at room temperature and 350 ℃ was 11.9, 8.1 MPa·m1/2 respectively, coinciding well with the values from references. The fatigue crack growth rates at 350 ℃ were about 2-20 times as high as those at room temperature. In the subcritical propagation zone, the relationship between fatigue crack growth rate and stress intensity factor range accorded with Paris equation. The parameter m in the equation was temperature-independent while parameter D showed a linearly positive correlation with temperature. The failure mode of the specimen was transgranular fracture.