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Materials 2018, 11(1), 98; https://doi.org/10.3390/ma11010098

Very High Cycle Fatigue Behavior of a Directionally Solidified Ni-Base Superalloy DZ4

1
School of Materials Science and Energy Engineering, Foshan University, Foshan 528000, China
2
School of Materials Science and Engineering, Beihang University, Beijing 100191, China
3
School of Environmental and Chemical Engineering, Foshan University, Foshan 528000, China
*
Author to whom correspondence should be addressed.
Received: 10 December 2017 / Revised: 28 December 2017 / Accepted: 8 January 2018 / Published: 10 January 2018
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Abstract

The effect of casting pores on the very high cycle fatigue (VHCF) behavior of a directionally solidified (DS) Ni-base superalloy DZ4 is investigated. Casting and hot isostatic pressing (HIP) specimens were subjected to very high cycle fatigue loading in an ambient atmosphere. The results demonstrated that the continuously descending S-N curves were exhibited for both the casting and HIP specimens. Due to the elimination of the casting pores, the HIP samples had better fatigue properties than the casting samples. The subsurface crack initiated from the casting pore in the casting specimens at low stress amplitudes, whereas fatigue crack initiated from crystallographic facet decohesion for the HIP specimens. When considering the casting pores as initial cracks, there exists a critical stress intensity threshold ranged from 1.1 to 1.3 MPa m , below which fatigue cracks may not initiate from the casting pores. Furthermore, the effect of the casting pores on the fatigue limit is estimated based on a modified El Haddad model, which is in good agreement with the experimental results. Fatigue life for both the casting and HIP specimens is well predicted using the Fatigue Indicator Parameter (FIP) model. View Full-Text
Keywords: DZ4; casting defects; VHCF; crack initiation DZ4; casting defects; VHCF; crack initiation
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Nie, B.; Zhao, Z.; Liu, S.; Chen, D.; Ouyang, Y.; Hu, Z.; Fan, T.; Sun, H. Very High Cycle Fatigue Behavior of a Directionally Solidified Ni-Base Superalloy DZ4. Materials 2018, 11, 98.

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