PSI - Issue 19

Lloyd Hackel et al. / Procedia Structural Integrity 19 (2019) 452–462 Valentin LOURY--MALHERBE/ Structural Integrity Procedia 00 (2019) 000–000

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7. Conclusions and continuing work: The results of this initial work strongly suggest that the LP + TME technique has great promise for extending the performance of superalloys used in high temperature applications. Implications in two significant areas: 1. Improvement of material performance of superalloys in high temperature applications. This would include wrought and AM materials, and extend into directionally cast and single crystal materials. 2. Potential use of AM components in safety critical applications combining safety and improved fuel efficiency. Our intent is to extend this work in several important areas so as to enable high value applications. We specifically plan the following: 1. Fabricate and test fatigue samples of wrought In718 to enable detailed comparison against the AM material. In tests of 316L we were able to perform a single sample comparison of the fatigue life a wrought 316L sample against more extensive tests of AM316L. Surprisingly the AM material in the single test performed significantly better than the wrought material. This has a powerful suggestion that “well-made” AM components might truly be considered for safety critical applications and highly advanced performance. 2. More extensively test the LP+TME process in both AM and wrought materials including single crystal alloys. Perform microscopic examination of microstructure so as gain a better understanding of the changes induced by shock and annealing. 3. We definitely need to consider fatigue testing with real-time thermal loading. This is a much more challenging test regime but important for establishing the advanced capability of LP+TME and the potential for increased turbine fuel efficiencies. 4. In a similar manner we need to perform tests of stress induced creep in the thermally loaded regime. Creep is directly related to stress loading and the compressive stress of the LP+TME process should reduce creep effects as well as improve fatigue performance. Creep is of importance to superalloys but also materials such as Ti6/4 used in compressors. Limitations on rotor-to-stator spacing and thus compressor efficiencies are impacted by concerns associated with momentary thermal loading and consequent creep and resulting fatigue issues. 5. Because of the ability to fabricate components with internal structures not capable to forging, casting or machining, an AM blade structure could be made that would incorporate advanced cooling passages in the blade and thereby enable much improved heat loading . Such an advance would lay the groundwork for improved efficiency performance of turbines and other systems. [1] “Total fuel consumption of commercial airlines worldwide between 2005 and 2019,” statista.com. [2] "Shot peening," en.wikipedia.org/wiki/Shot_peening. [3] Clauer, A. H. "A Historical Perspective on Laser Shock Peening". Metal Finishing News. 10. [4] M. B. Prime, “Residual Stress Measurement by Successive Extension of a Slot: The Crack Compliance Method,” Appl. Mech. Rev., vol. 52, no. 2, pp. 75–96, Feb. 1999. [5] S. Prabhakaran, S. Kalainathan, P. Shukla, and V. K. Vasudevan, “Residual stress, phase, microstructure and mechanical property studies of ultrafine bainitic steel through laser shock peening,” Opt. Laser Technol., vol. 115, pp. 447–458, 2019. [6] S. U. 2. Hill, M.R., 1996, Determination of residual stress based on the estimation of eigenstrain, PhD dissertation, “No Title.” [7] Y. Ueda, K. Fukuda, and Y. C. Kim, “New Measuring Method of Axisymmetric Three-Dimensional Residual Stresses Using Inherent Strains as Parameters,” J. Eng. Mater. Technol., vol. 108, no. 4, pp. 328–334, Oct. 1986. [8] H. Luong and M. R. Hill, “The effects of laser peening and shot peening on high cycle fatigue in 7050-T7451 aluminum alloy,” Mater. Sci. Eng. A, vol. 527, no. 3, pp. 699–707, 2010. [9] K. A. Gujba and M. Medraj, “Laser Peening Process and Its Impact on Materials Properties in Comparison with Shot Peening and Ultrasonic Impact Peening,” Materials , vol. 7, no. 12. 2014. [10] Y. K. Gao, “Improvement of fatigue property in 7050–T7451 aluminum alloy by laser peening and shot peening,” Mater. Sci. Eng. A, vol. 528, no. 10, pp. 3823–3828, 2011. [11] B. K. Pant, A. H. V Pavan, R. V Prakash, and M. Kamaraj, “Effect of laser peening and shot peening on fatigue striations during FCGR study of Ti6Al4V,” Int. J. Fatigue, vol. 93, pp. 38–50, 2016. References