PSI - Issue 58

Juraj Belan et al. / Procedia Structural Integrity 58 (2024) 109–114

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Juraj Belan et al. / Structural Integrity Procedia 00 (2023) 000–000

In the fatigue tests with the cycle asymmetry parameter R < 1, only a minimal decrease in the total fatigue life corresponding to approx. 2% was detected at the number of cycles to fracture of 2.10 7 , comparing the initial state and the state after applying annealing 800°C/ 72h. However, a more significant difference was recorded in the area of low cycle fatigue, at the number of cycles to fracture of 3.5.10 5 (the so-called timed fatigue limit), where the fatigue life decreased by about 18%. An even more significant decrease in fatigue life is recorded at lower numbers of cycles to failure. This phenomenon is mainly characteristic of the so-called Manson-Coffin part of the S-N curve, where the fatigue process is controlled by the size of the stress amplitude and is structurally very sensitive. It follows that the increased volume fraction of the delta phase has a significant negative effect on the elastic-plastic characteristics of the IN 718 alloy under cyclic loading. This fact can be seen from the course of the fatigue curves (Fig. 2) for three point bending, where the samples after annealing generally had a flatter curve. 4. Conclusions Based on the experimental results, it can be concluded that the applied annealing did not have a significant effect on the change in the grain size of the gamma solid solution. It is a consequence of the positive effect of the delta phase. However, from the point of view of dynamic mechanical properties, the increased proportion of the delta phase is undesirable; it reduces the fatigue life at higher loading amplitudes and a lower number of cycles to fracture. The excluded δ-phase at higher loading amplitudes acted as a stress concentrator and reduced the number of cycles required to initiate a fatigue crack and increased the rate of propagation of a fatigue crack, which propagated through the material by an intercrystalline mechanism along the grain boundaries, respectively. Acknowledgements The authors acknowledge the KEGA projects No. 004ŽU-4/2023 and No. 009ŽU-4/2023 for the financial support Belan, J., 2012. Study of Advanced Materials for Aircraft Jet Engines Using Quantitative Metallography. In: Agarwal, R. K., editor. Recent Advances in Aircraft Technology [Internet]. London: IntechOpen, pp. 49 – 74. Belan, J., 2016. GCP and TCP Phases Presented in Nickel-base Superalloys. Materials Today: Proceedings 3, 936-941. Belan, J., Vaško, A., Kuchariková, L., Tillová, E., Matvija, M., 2018. The high-temperature loading influence on orthorhombic Ni3Nb DOa δ - phase formation and its effect on fatigue lifetime in alloy 718. Manufacturing Technology 18, 875-882. Gonzalo, M. D. A., Manuel, G. T., Alexiane, D., 2020. Ultrasonic Fatigue Tests on the Inconel Alloy 718. Procedia Structural Integrity 26, 20-27. Gonzalo, M. D. A., Manuel, G. T., Ishvari F. Z. T., 2022. Ultrasonic fatigue endurance of Inconel 718 after the heat treatments: solution annealing and double aging. Procedia Structural Integrity 39, 281-289. Goodfellow, A., J., 2018. Strengthening mechanisms in polycrystalline nickel-based superalloys. Materials Science and Technology 34, 1793-1808. He, L. Z., Zheng, Q., Sun, X. F., Guan, H.R., Hu, Z. Q., Tieu, A. K., Lu, C., Zhu, H. T., 2005. Effect of carbides on the creep properties of a Ni base superalloy M963. Materials Science and Engineering: A 397, 297-304. Kim D., Jiang, R., Evangelou, A., Sinclair, I., Reed, P. A. S., 2021. Effects of γʹ size and carbide distribution on fatigue crack growth mechanisms at 650 °C in an advanced Ni-based superalloy. International Journal of Fatigue 145, 106086. Maj, P., Adamczyk-Cieslak, B., Slesik, M., Mizera, J., Pieja, T., Sieniawski, J., Gancarczyk, T., Dudek, S., 2017. The precipitation processes and mechanical properties of aged Inconel 718 alloy after annealing. Archives of Metallurgy and Materials 62, 1695-1702. Silva, Ch., Song, M., Leonard, K., Wang, M., Was, G., Busby, J., 2017. Characterization of alloy 718 subjected to different thermomechanical treatments. Materials Science & Engineering A 691, 195-202. Sulzer, S., Hasselqvist, M., Murakami, H. et al., 2020. The Effects of Chemistry Variations in New Nickel-Based Superalloys for Industrial Gas Turbine Applications. Metallurgical and Materials Transactions A 51, 4902–4921. Sundararaman, M., Mukhopadhyay, P., Banerjee, S., 1988. Precipitation of the δ-Ni3Nb phase in two nickel-base superalloys. Metallurgical Transactions A 19, 453-465. Sundararaman M., Mukhopadhyay, P., Banerjee, S., 1997. Carbide precipitation in nickel-base superalloys 718 and 625 and their effect on mechanical properties. In: Superalloys 718, 625, 706 and Various Derivatives, Edited by E.A. Loria, The Minerals, Metals & Materials Society, pp. 367-378. of this work. References