Creep Failure and Damage Mechanism of Inconel 718 Alloy at 800–900 °C
The creep behavior and damage mechanisms of 718 alloys were investigated at 800–900 °C in air. The fracture morphology and microstructure evolution were observed by optical, scanning and transmission electron microscope. Besides, the creep damage tolerance (λ) and creep strain evolution curve were also calculated. The results showed that the creep curves of 718 alloys at 800 or 850 °C consisted of primary and tertiary stages, while the steady-state region became apparent at 900 °C. The apparent creep activation energy of 718 alloy was in the range from 446.3 to 491.8 kJ/mol. The alloy presented ductile fracture at 800 °C due to the nucleation, growth and linkage of creep voids. However, the failure of alloys at 850 or 900 °C presented necking to a point due to the microstructure degradation. Further investigations showed the softening of materials and the loss of mechanical performance could be mainly attributed to the coarsening or decrease of strengthening precipitates. Above 850 °C, it was found that γ′ phases would dissolve into matrix and stress promoted the re-dissolution of γ′ phases or led to the break of δ phases. Moreover, the creep strain evolution curves indicated that 718 alloys kept a relative stable state at 800–900 °C when the strain fraction was below 1.
KeywordsInconel 718 Creep failure Damage mechanism Microstructure degradation
The authors would like to thankfully appreciate the support of this research from the National Natural Science Foundation of China (Grant No. 51771016, 51771017).
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
- 5.R.W. Hayes, in Proceedings of the International Symposium on Superalloys 718, 625, 706 and Various Derivatives, ed. by E.A. Loria (The Minerals, Metals & Materials Society, Warrendale, PA,1991) pp. 549–562Google Scholar
- 6.M.C. Chaturvedi, Y.F. Han, in Proceedings of the International Symposium on Superalloys 718─Metallurgy and Applications, ed. by E. A. Loria EA (The Minerals, Metals & Materials Society, Warrendale, PA, 1989) pp. 489–498Google Scholar
- 8.J.F. Radavich, G.E. Korth, High temperature degradation of alloy 718 after longtime exposures, in Superalloys 1992, in The Minerals, Metals & Materials Society, ed. by S.D. Antolovich, R.W. Stusrud, R.A. MacKay, D.L. Anton, T. Khan, R.D. Kissinger, D.L. Klarstrom (PA, Warrendale, 1992), pp. 497–505Google Scholar
- 25.J.T. Guo, D. Ranucci, E. Picco, P.M. Strocchi, An investigation on the creep and fracture behavior of cast nickel-base superalloy IN738LC. Metall. Trans. A. 14A, 2329–2335 (1983)Google Scholar
- 37.S. Azadian, L.Y. Wei, F. Niklasson, R. Warren, Precipitation in spray-formed IN 718, In: Loria EA (ed) Proceedings of the international symposium on superalloys 718, 625, 706 and various derivatives. The Minerals, Metals & Materials Society, Warrendale, PA, 617–626 (2001).Google Scholar
- 41.M.F. Ashby, B.F. Dyson, Creep damage mechanics and micromechanisms (Pergamon Press, Oxford, 1984), pp. 3–30Google Scholar