Surface Integrity of TA19 Notched Simulated Blades with Laser Shock Peening and Its Effect on Fatigue Strength
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JMEPEG https://doi.org/10.1007/s11665-020-05025-z
Surface Integrity of TA19 Notched Simulated Blades with Laser Shock Peening and Its Effect on Fatigue Strength Junfeng Wu, Zhigang Che, Shikun Zou, Ziwen Cao, and Rujian Sun (Submitted April 7, 2020; in revised form June 20, 2020) To reveal the fatigue strengthening mechanism of TA19 notched simulated blades with laser shock peening (LSP), surface integrity and fatigue strength were investigated. The surface morphology, residual stress, near-surface microstructure, fatigue strength and fatigue fracture morphology were analyzed by surface profiler, x-ray diffraction (XRD), transmission electron microscopy (TEM), QRG-100 servo-hydraulic fatigue test machine and scanning electron microscope (SEM). Results indicated that LSP induced surface micro-dents plastic deformations with a few microns in depth, surface compressive residual stresses and surface nano-grains of TA19 notched simulated blades. Compared with the as-received material, fatigue strengths of TA19 notched simulated blades were improved by 162% for LSP-1 and 218% for LSP-3. In addition, fatigue crack initiation (FCI) locations reduced after LSP, fatigue crack growth (FCG) rate decreased after LSP, and secondary cracks were observed in the FCI and FCG regions of fatigue fracture morphologies after LSP. Fatigue strengthening mechanism of TA19 notched simulated blades with LSP was compressive residual stresses and refined grains. Results could be beneficial to the application of LSP process in civil engines blades. Keywords
compressive residual stresses, fatigue strengthening mechanism, laser shock peening (LSP), refined grains, TA19 notched simulated blades
1. Introduction TA19 alloy (also named as Ti-6Al-2Sn-4Zr-2Mo for ASTM) is a near-a titanium alloy and widely used in civil engines as integral disks and blades because of its great mechanical property (Ref 1-3). However, the blade leading edge experiences the foreign object and is subjected to the foreign object damage (FOD) during the aircraft takeoff and landing (Ref 4). The velocities of these objects may reach 500 m/s, which cause the stress concentrations or the failure sources at the leading edge of the blades. Then, these cause the rapid fracture of blades (Ref 5, 6). In addition, the titanium alloy is very sensitive to the FOD notch. As a result, the FOD notch has been identified as one of the main factors limiting the fatigue lives of civil engine blades. In recent years, advanced surface treatments, such as laser shock peening (LSP), have been used to improve the fatigue crack growth (FCG) resistance of the critical components (Ref 7, 8). Compared with the traditional shot peening, LSP induces much deeper compressive residual stress layers at the leading
Junfeng Wu, Zhigang Che, Shikun Zou, Ziwen Cao, and Rujian Sun, Science and Technology on Power Beam Processes Laboratory, AVIC Manufacturing Technology Institute, Beijing 100024, PeopleÕs Republic of China. Contact e-mail: [email protected].
Journal of Materials Engineering and Performance
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