期刊
INTERNATIONAL JOURNAL OF FATIGUE
卷 114, 期 -, 页码 11-21出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.ijfatigue.2018.04.033
关键词
High temperature fatigue; Oxidation; Crack initiation; Crack growth; Sanicro 25
资金
- IPMinfra [LM2015069]
- project CEITEC 2020 of MEYS [LQ1601]
- project RVO [68081723]
- project OP VVV [CZ.02.2.69/0.0/0.0/16_027/0008056]
- Grant Agency of the Czech Republic [13-23652S, 15-08826S]
Crack initiation and short crack growth in highly-alloyed austenitic steel Sanicro 25 cyclically strained at a temperature of 700 degrees C has been studied. Specimens cycled to 10% of the fatigue life and to the fracture were inspected using scanning electron microscopy and electron backscatter diffraction. On the surface, thin lamellae were extracted site-specifically by focused ion beam and then they were further characterized by high spatial resolution scanning transmission electron microscopy and energy dispersive X-ray spectroscopy. The preferential oxidation of grain boundaries was found to play a principal role in the initiation of multiple cracks. The oxide scale was analysed to show the distribution of individual elements during crack initiation and growth. Two types of crack paths were observed: intergranular due to the oxidation and transgranular accompanied by a cyclic plastic zone. Cracks preferentially initiated at the grain boundaries perpendicular to the stress axis and propagated in the bulk of the material. The role of the oxidation in high temperature fatigue crack initiation is discussed as well as the mechanisms of the crack initiation and growth.
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