Revealing the fatigue crack propagation mechanism of a Ni-based superalloy electron beam welded joint through in-situ SEM observation

In this study, in-situ scanning electron microscope (SEM) fatigue crack propagation experiments for electron beam welded joints of GH4169 Ni-based superalloy are carried out. Based on material characterization and analysis, the corresponding fatigue crack propagation mechanism of the welded joint (WJ) is investigated. Compared to the base material (BM), the WJ has comparable static strength, but worse plasticity. Significantly, the WJ has longer fatigue crack growth life than that of the BM. The fatigue crack growth rate (FCGR) curves of the WJ and the BM intersected with each other. In particular, under low stress intensity factors (Delta K) level, the FCGR of the WJ is lower than that of the BM. Under high Delta K level, the FCGR of the WJ is higher than that of the BM. The steep FCGR curve of the WJ can be attributed to the unique weld texture and a shielding effect caused by the weld strength mismatch.

Automated summary

This study investigates the fatigue crack propagation mechanism of electron beam welded joints of GH4169 Ni-based superalloy through in-situ scanning electron microscope (SEM) experiments. It is found that the welded joint has comparable static strength but worse plasticity compared to the base material. Interestingly, the welded joint exhibits a longer fatigue crack growth life than the base material. The fatigue crack growth rate (FCGR) curves of the welded joint and the base material intersected with each other, with the FCGR of the welded joint being lower at low stress intensity factors and higher at high stress intensity factors.