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Open AccessArticle

Effects of the γ″-Ni3Nb Phase on Fatigue Behavior of Nickel-Based 718 Superalloys with Different Heat Treatments

1
Shanghai Key Lab of Advanced High-temperature Materials and Precision Forming, Shanghai Jiao Tong University, Shanghai 200240, China
2
Mechanical and Electrical Engineering College, Nanchang University, Nanchang 330031, China
*
Author to whom correspondence should be addressed.
Materials 2019, 12(23), 3979; https://doi.org/10.3390/ma12233979
Received: 23 August 2019 / Revised: 7 November 2019 / Accepted: 18 November 2019 / Published: 30 November 2019
The effects of the γ″-Ni3Nb phase on fatigue behavior of nickel-based 718 superalloys with standard heat treatment, hot isostatic pressing + solution treatment + aging, and hot isostatic pressing + direct aging were investigated by scanning electron microscope, transmission electron microscopy, and fatigue experiments. The standard heat treatment, hot isostatic pressing + solution treatment + aging, and hot isostatic pressing + direct aging resulted in the formation of more and smaller γ″ phases in the matrix in the nickel-based 718 superalloys. However, the grain boundaries of the hot isostatic pressing + direct aging sample showed many relatively coarse disk-like γ″ phases with major axes of ~80 nm and minor axes of ~40 nm. The hot isostatic pressing + direct aging sample with a stress amplitude of 380 MPa showed the longest high cycle fatigue life of 5.16 × 105 cycles. Laves phases and carbide inclusions were observed in the crack initiation zone, and the cracks propagated along the acicular δ phases in the nickel-based 718 superalloys. The precipitation of fine γ″ phases in the matrix and relatively coarse γ″ phases in the grain boundaries of the hot isostatic pressing + direct aging sample can hinder the movement of dislocation. View Full-Text
Keywords: γ″-Ni3Nb; fatigue behavior; nickel-based 718 superalloy; heat treatment; hot isostatic pressing γ″-Ni3Nb; fatigue behavior; nickel-based 718 superalloy; heat treatment; hot isostatic pressing
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Ling, L.-S.-B.; Yin, Z.; Hu, Z.; Wang, J.; Sun, B.-D. Effects of the γ″-Ni3Nb Phase on Fatigue Behavior of Nickel-Based 718 Superalloys with Different Heat Treatments. Materials 2019, 12, 3979.

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