Characterization on Crack Initiation and Early Propagation Region of Nickel-Based Alloys in Very High Cycle Fatigue

Zelin Chen; Zihao Dong; Chang Liu; Yajun Dai; Chao He

doi:10.3390/ma15175806

Characterization on Crack Initiation and Early Propagation Region of Nickel-Based Alloys in Very High Cycle Fatigue

Materials (Basel). 2022 Aug 23;15(17):5806. doi: 10.3390/ma15175806.

Authors

Zelin Chen¹, Zihao Dong¹, Chang Liu^{1

2}, Yajun Dai^{1

2}, Chao He^{1

2}

Affiliations

¹ Failure Mechanics and Engineering Disaster Prevention Key Laboratory of Sichuan Province, Sichuan University, Chengdu 610105, China.
² MOE Key Laboratory of Deep Earth Science and Engineering, College of Architecture and Environment, Sichuan University, Chengdu 610065, China.

Abstract

As nickel-based alloys are more and more widely used in engineering fields for bearing cyclic loadings, it is necessary to study their very-high-cycle fatigue (VHCF) properties. In this paper, the fatigue properties of nickel-based alloy 625 were investigated using an ultrasonic fatigue test apparatus. The fracture microscopy shows that around the crack initiation site there are two characteristic zones, a rough area (RA) and a fine granular area (FGA). Inclusions caused the interior fatigue crack initiation, and the coalescence of neighboring micro cracks was strongly influenced by the local microstructure, resulting in the RA morphology. Subsequently, the contact and compressing of the crack surfaces contributed to the formation of the FGA. Finally, the stress intensity factors of the RA and FGA were quantitatively evaluated for further discussion of the crack initiation and propagation processes.

Keywords: Inconel 625; crack initiation; fine granular area; rough area; stress intensity factor; very-high-cycle fatigue.

Grants and funding

This research was financially supported by the National Natural Science Foundation of China (grant numbers 12072212 and 11832007), the Sichuan Science and Technology Program (2021YJ0071 and 2020YJ0230), and the National Key Research and Development Program of China (No. 2018YFE0307104).