Effect of service exposure on fatigue crack propagation of Inconel 718 turbine disc material at elevated temperatures

Journal Article · Mon Sep 15 04:00:00 EDT 2014 · Materials Characterization

DOI:https://doi.org/10.1016/J.MATCHAR.2014.06.022· OSTI ID:22403550

Jeong, Dae-Ho ^[1]; Choi, Myung-Je ^[2]; Goto, Masahiro ^[3]; Lee, Hong-Chul ^[4]; Kim, Sangshik ^[1]

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1. Department of Materials Science and Engineering, RECAPT, Gyeongsang National University, Chinju (Korea, Republic of)
2. Korea Aerospace Industry, Sacheon (Korea, Republic of)
3. Department of Mechanical Engineering, Oita University, Oita (Japan)
4. Republic of Korea Air Force (Korea, Republic of)

In this study, the fatigue crack propagation behavior of Inconel 718 turbine disc with different service times from 0 to 4229 h was investigated at 738 and 823 K. No notable change in microstructural features, other than the increase in grain size, was observed with increasing service time. With increasing service time from 0 to 4229 h, the fatigue crack propagation rates tended to increase, while the ΔK{sub th} value decreased, in low ΔK regime and lower Paris' regime at both testing temperatures. The fractographic observation using a scanning electron microscope suggested that the elevated temperature fatigue crack propagation mechanism of Inconel 718 changed from crystallographic cleavage mechanism to striation mechanism in the low ΔK regime, depending on the grain size. The fatigue crack propagation mechanism is proposed for the crack propagating through small and large grains in the low ΔK regime, and the fatigue crack propagation behavior of Inconel 718 with different service times at elevated temperatures is discussed. - Highlights: • The specimens were prepared from the Inconel 718 turbine disc used for 0 to 4229 h. • FCP rates were measured at 738 and 823 K. • The ΔK{sub th} values decreased with increasing service time. • The FCP behavior showed a strong correlation with the grain size of used turbine disc.

• OSTI ID: 22403550
• Journal Information: Materials Characterization, Journal Name: Materials Characterization Vol. 95; ISSN 1044-5803; ISSN MACHEX
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CLEAVAGE
CORRELATIONS
CRACK PROPAGATION
CRACKS
CRYSTALLOGRAPHY
FATIGUE
GRAIN SIZE
INCONEL 718
MATERIALS TESTING
SCANNING ELECTRON MICROSCOPY
STRIATIONS
TURBINES