New insights into thermomechanical fatigue behavior of AISI Type 316 LN SS weld joint

Abstract

Cyclic deformation and fracture behavior of a type 316 LN austenitic stainless steel (SS) weld joint (WJ) were investigated under thermomechanical fatigue (TMF) and isothermal low cycle fatigue (IF) cycling at the maximum temperature (Tmax) of TMF. A higher cyclic stress response (CSR) and reduced cyclic softening were observed under TMF compared with IF tests. In‐phase (IP) TMF resulted in lower lives compared with IF cycling at the Tmax and out‐of‐phase (OP) TMF, which was attributed to the more pronounced creep‐induced intergranular damage. Characterization of microstructural features and microhardness variations revealed that the accumulation of damage and associated failure depends on the strength and microstructural gradient, together with the deformation incompatibility. The crack propagation is found to depend on the individual and synergistic interactions of the microstructural transformations, creep, and oxidation, depending on the type of fatigue cycle (IF and IP/OP TMF), strain amplitude, and thermal cycling effects.

Thermomechanical and isothermal fatigue crack propagation testing method for 316LN austenitic stainless steel

“…A large number of reports have studied the mechanical behavior and fatigue life of 316LN SS under TMF loading condition 11,12 . However, research is rarely published about the fatigue crack propagation behavior of 316LN SS under TMF loadings 13,14 . Actually, the structures can continue to serve for a certain period of time even when cracks develop during their practical service process 15–17 .…”

“…11,12 However, research is rarely published about the fatigue crack propagation behavior of 316LN SS under TMF loadings. 13,14 Actually, the structures can continue to serve for a certain period of time even when cracks develop during their practical service process. [15][16][17] Therefore, it is of quite importance to evaluate the residual life by performing crack propagation tests under servicesimulating conditions.…”