Key Takeaways & Executive Findings
- •• LSP-CS treatment improved the fretting fatigue lifetime of GH4169 dovetail components at 500 °C by up to 494.9%, outperforming LSPwC (346.8%). • Both LSPwC and LSP-CS introduce plastic deformation and residual compressive stress layers without significantly altering grain size, enhancing surface integrity. • LSP-CS yields higher surface microhardness (+28.6%) and greater residual compressive stress (−404.3 MPa) compared to LSPwC (+20.5%, −306.5 MPa). • The synergistic effect of the hardening layer and residual stress layer is the key mechanism for the improved fretting fatigue resistance at elevated temperatures.
Abstract
The effects of nanosecond laser shock peening without coating (LSPwC) and nanosecond stacked femtosecond laser shock peening compound strengthening (LSP-CS) on the surface integrity and fretting fatigue lifetime at 500 ℃ of GH4169 dovetail component were investigated. The results show that LSP treatment does not significantly lead to changes in the grain size of GH4169 alloy, but it introduces a large number of dislocations, resulting in the formation of a plastic deformation layer and residual compressive stress layer. The surface microhardness increased by 20.5% and 28.6% after being treated by LSPwC and LSP-CS, respectively. The surface residual compressive stresses were (−306.5±42.5) MPa and (−404.3±34.7) MPa, respectively; The depth of both the hardening layer and the residual compressive stress layer is 400 μm, and along the cross-section with 0−100 μm region after LSP-CS treatment has higher hardness and greater residual compressive stress. The fretting fatigue lifetime of the GH4169 dovetail component at 500 ℃ was increased by 346.8% and 494.9%, which is the result of the combined effects of the hardening layer and the residual stress layer. The LSP-CS treatment can effectively make up for the disadvantage of the LSPwC treatment, and further enhance the fretting fatigue lifetime of the GH4169 dovetail component at high temperature.
1. Introduction
GH4169 is a precipitation hardening nickel-based high-temperature alloy (γ" -Ni3Nb/γ' -Ni3Al), which has high hardness, high corrosion resistance, creep resistance, and excellent mechanical properties at high temperatures, making it widely used in aerospace and marine industries [1 −3]. GH4169 high-temperature alloy is equivalent to the US-grade Inconel 718, which is often used to make engine discs, shafts and blades [4 −6]. During the operation of an aero-engine, the blades and discs of the mortise-and-tenon joint are often subjected to fretting fatigue, which can lead to cracking and fracture failure [7−9]. Therefore, it is necessary to improve the surface properties of the material through surface treatment, so as to improve the fretting fatigue performance of the tongue-and-groove joint structure between the blade and the disc, and thus increase the service life of the aero-engine [10, 11].
Currently, the commonly used surface treatment technologies are shot peening (SP), ultrasonic nano roller pressing (UNSM), thermal spray coating and laser shock peening (LSP) [12 −15]. Each of these surface-strengthening techniques has its strengths and weaknesses. Among them, laser shock peening technology, as a relatively new surface strengthening technology, has high research value [16 −18]. Advantages include precise machining parameters, greater depth of penetration, wide applicability, cleaner machining environments, and more [19 −22]. Compared with the traditional laser shock peening technology, the uncoated laser shock peening technology (LSPwC) and femtosecond laser shock peening technology (FS-LSP) have superior characteristics. LSPwC has no absorbing layer in the process, only constraining layers [23]. FS-LSP has neither absorbing nor constraining layers during processing, both of which simplify the process to some extent. The laser energy of conventional LSP technology can reach the joule level, whereas the laser energy of LSPwC technology is typically between a few tens and a few hundred millijoules [24]. This effectively avoids severe ablation of the material during processing. However, high power densities of pulsed lasers can still cause some degree of thermal damage when acting on the surface of the material. Processing laser energies in FS-LSP technology are typically in the microJoule class, and their pulse durations can be as long as 10 −15 s. Although its pulse duration is extremely short, the interaction of the laser with the electrons is non-thermal, so femtosecond lasers have extremely high peak power but low thermal effects [25].
DHAKAL et al [26] performed LSPwC strengthening of 7075-T6 aluminum alloy with
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FANG Xiu-yang, WANG Zheng, GONG Jian-en, WANG Zhi-guo, CHEN Tai-li, NI Jing, CAI Zhen-bing (2025). Improvement of fretting fatigue lifetime at 500 ℃ of GH4169 dovetail component treated by nanosecond stacked femtosecond laser shock peening. Journal of Central South University. https://doi.org/10.1007/s11771-025-6003-6
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Frequently Asked Questions
What is the effect of LSP-CS on the fretting fatigue lifetime of GH4169 dovetail at 500 °C?
The LSP-CS treatment increased the fretting fatigue lifetime of GH4169 dovetail components at 500 °C by 494.9%, outperforming LSPwC which achieved a 346.8% improvement.
How does LSP-CS compare to LSPwC in improving surface hardness and residual stress?
LSP-CS resulted in a higher surface microhardness increase of 28.6% and a residual compressive stress of −404.3 MPa, whereas LSPwC only achieved a 20.5% microhardness increase and −306.5 MPa residual stress.
What is the mechanism behind the improved fretting fatigue life after LSP treatments?
The improvement is attributed to the combined effects of a plastic deformation layer and a residual compressive stress layer introduced by laser shock peening, which do not significantly alter grain size but enhance surface integrity and inhibit crack initiation and propagation.
What are the key surface integrity changes after LSPwC and LSP-CS treatments?
Both LSPwC and LSP-CS introduce a large number of dislocations, forming a plastic deformation layer and residual compressive stress layer of approximately 400 μm depth, with LSP-CS providing higher hardness and greater residual stress in the subsurface 0–100 μm region.
Why is the LSP-CS treatment considered advantageous for aerospace applications?
LSP-CS combines the benefits of nanosecond and femtosecond lasers, offering high precision, low thermal damage, and superior surface strengthening, which significantly enhances the fretting fatigue resistance of critical components like GH4169 dovetail joints at high temperatures.
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