The effect of nitrogen on low-cycle fatigue mechanisms of austenitic stainless cast steels

The effect of nitrogen on mechanical properties and low cycle behaviour of Cr-Ni-Mn-Mo-Nb-N austenitic stainless cast-steels has been investigated at room temperature. Results obtained are as follows:

1. Nitrogen induces cyclic softening over the composition 0.267 to 0.496 wt % and influences the number of cycles to failure

2. Plastic strain range Delta epsilon_p is determined as a nonlinear function of both a number of cycles N_c and stress amplitude sigma_a (exp(sigma_aC3))

3. Radial arrangement of dendrites in cast steels has a significant influence on the fracture character

4. In tension as well as in low-cycle fatigue, the interstitial nitrogen promotes planar character of deformation.