Effect of secondary austenite on fatigue behavior of S32750 super duplex stainless steel

Tension-tension fatigue tests were carried out to investigate the effect of secondary austenite (gamma(2)) on the fatigue behavior of S32750 super duplex stainless steel (SDSS). Stress-life curves were fitted and analyzed in detail. It was demonstrated that gamma(2) deteriorates the fatigue resistance of SDSS. To further study the role of gamma(2) in fatigue deformation, fracture surfaces were examined. gamma(2) increased the probability of ferrite as a crack initiation source, which could be attributed to the combined variation of the ferrite/austenite interface relationship and alloying elemental distribution. gamma(2) increased the ratio of Kurdjumov-Sachs/Nishiyama-Wassermann crystallographic orientation, making the slip systems crossing the ferrite/austenite boundaries easier to affect the formation of fine-scaled dislocation structure in ferrite. Moreover, segregation of N enhanced the strength of gamma(2), thus leading to the earlier plastic deformation of partial ferrite in the fatigue deformation process.

Automated summary

Tension-tension fatigue tests were conducted to study the effect of secondary austenite on the fatigue behavior of super duplex stainless steel. The results showed that secondary austenite decreased the fatigue resistance of the material. Fracture surface analysis revealed that secondary austenite increased the probability of ferrite as a crack initiation source, which could be attributed to the change in ferrite/austenite interface relationship and elemental distribution. Additionally, the segregation of N enhanced the strength of secondary austenite, leading to earlier plastic deformation in partial ferrite during the fatigue deformation process.