Fatigue Behavior in an Fe-N Binary Ferritic Steel: Similarity and Difference between Carbon and Nitrogen

Abstract

Fatigue crack initiation and propagation behavior of a water-quenched fully ferritic nitrogen steel were investigated by means of tension-compression fatigue tests. The Fe-0.011 mass% N steel showed no serrated flow associated with dynamic strain aging, and showed a fatigue limit of 150 MPa alongside a non-propagating fatigue crack. The major mode of crack initiation was at the grain boundaries, and the cracks propagated along the grain boundaries and interiors at and above the fatigue limit. The Fe-N steel did not exhibit a significant level of coaxing effect. The results were compared with our previous findings in Fe-0.006 and 0.017C steels, and the similarity and difference were discussed.