Study on fatigue failure behavior of 316L/2Cr13 multilayered steel: Fracture mechanism and a new method for fatigue strength prediction

In this study, the high-cycle fatigue failure behavior of 316L/2Cr13 multilayered steel (MLS) is explored. Five kinds of MLS with different states are compared, among which are the as-rolled state and four heat-treatment states with different annealing temperatures and holding times. In order to establish the S-N curve, high-cycle fatigue tests are conducted. The difference of fatigue strength and behavior of five kinds of MLS was analyzed by microstructure, hardness and tensile property. The fatigue fracture mechanism was summarized using quasi-in-situ fatigue tests. The findings revealed that as the annealing temperature and the holding time increase, the fatigue strength of 316L/2Cr13 MLS decreases, which is associated with the dislocation density of 316L layers of 316L/2Cr13 MLS. In the process of cyclic loading, fatigue cracks always initiate along the slip band of ferrite with highest Schmid factor in the 2Cr13 layer, and the whole is mainly a trans-granular fracture. Ultimately, the fatigue strength is predicted according to the microhardness of the 316L layers as well as the work hardening of MLS. The error rate is less than 5 %.