On the conjoint influence of broaching and heat treatment on bending fatigue behavior of Inconel 718

Chen, Zhe; Peng, Ru Lin; Johansson, Sten; Gustafsson, David

doi:10.1016/j.msea.2016.06.030

Cited by 14 publications

(7 citation statements)

References 34 publications

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“…However, they pointed out that polishing can improve fatigue life when the residual stress has degenerated at high temperatures. Chen et al 14 reported the same finding in their research of broaching, polishing, and heat treatment on Inconel 718 superalloy. Warren and Guo 15 compared four combination processes of hard turning, grinding, and polishing on surface integrity and rolling contact fatigue performance.…”

Section: Introductionsupporting

confidence: 57%

Effects of process combinations of milling, grinding, and polishing on the surface integrity and fatigue life of GH4169 components

Quan

Chen

et al. 2019

Proceedings of the Institution of Mechanical Engineers, Part B:

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The nickel-based superalloy GH4169 is widely applied in the aviation industry due to its outstanding mechanical properties. However, many blades of GH4169 are still produced by milling and manual polishing, which is costly and unreliable. In this article, GH4169 superalloy components manufactured with combination processes of milling, grinding, and polishing were comparatively studied involving surface integrity and fatigue performance. Test results indicate that the final polishing is the most dominant process that influences the high-cycle fatigue life of GH4169 components. Samples produced via cubic boron nitride grinding and numerical control polishing with a diamond-rubber wheel exhibit fatigue limits of 150 MPa higher than the milled and manually polished samples. Cubic boron nitride grinding induces a considerable compressive residual stress profile with a magnitude of -930 MPa and a depth of 200 μm. Milling induces a typical “hook” residual stress profile with 318 MPa at the surface. Polishing affects the machined surface by two ways, the removal effect and the squeezing effect. The squeezing effect induces a shallow compressive residual stress with approximately −1000 MPa, therefore improves the surface condition. However, inevitable omissions, scratches, texture disorders, and knock marks in hand-polishing are the main causes of the unstable high-cycle fatigue life of hand-polished components.

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Section: Introductionsupporting

confidence: 57%

Effects of process combinations of milling, grinding, and polishing on the surface integrity and fatigue life of GH4169 components

Quan

Chen

et al. 2019

Proceedings of the Institution of Mechanical Engineers, Part B:

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“…Several researchers have undertaken to study the influence of residual stress on the fatigue performance of Inconel 718. Chen et al [12] investigated the influence of the broaching process on the bending fatigue behavior of Inconel 718. They pointed out that the CRS in a longitudinal direction at the surface induced by broaching could extend the bending fatigue life of Inconel 718.…”

Section: Introductionmentioning

confidence: 99%

Effects of Machining Induced Residual Shear and Normal Stresses on Fatigue Life and Stress Intensity Factor of Inconel 718

Hua

Wang

2019

Applied Sciences

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Residual shear stresses and normal stresses induced by machining affect the fatigue performance of components. Thus, residual shear and normal stresses should be considered simultaneously when evaluating the influence of residual stress on fatigue performance. In the present paper, the influences of residual shear and normal stresses on the fatigue life and stress intensity factor (SIF) of turned Inconel 718 were investigated. Firstly, the cos α measurement method was utilized to calculate the residual shear stress and residual normal stress of turned Inconel 718. Then, the combined effects of residual shear and normal stresses on fatigue life were evaluated through uniaxial tension–tension fatigue tests. Thirdly, a prediction model for the SIF was proposed by taking the residual shear and normal stresses into account. Finally, the predicted SIF was validated by the published experimental data from the literature. The predicted results of the proposed model generally agreed well with the available experimental data.

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“…The achievement of desired surface roughness is not only essential to the subsequent assembly, but also plays a pivotal role in determining the fatigue life and strength of the workpiece [54]. It has been shown that fatigue cracks are usually initiated from persistent slip bands or at grain boundaries if the specimen has low surface roughness, for instance, a specimen with a polished surface [54,55]. However, the micro-notch effect on a rougher surface will lead to a local plastic strain field when an external load is applied due to stress concentration.…”

Section: Surface Topographymentioning

confidence: 99%

“…In addition, a hardness reduction within the surface work-hardened layer has been commonly observed after thermal exposure as a consequence of the annihilation of dislocations [55,82]. These thermal effects on surface integrity are extremely important when high fatigue resistance and tight tolerance of component dimensions are strongly required for high temperature applications.…”

Section: Effect Of Thermal Exposurementioning

confidence: 99%

Surface Integrity and Fatigue Performance of Nickel-based Superalloys

Chen¹

Self Cite

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Gas turbines are widely used in e.g., power generation, and aero-industries. Due to global warming, the demand for more efficient gas turbines has increased. A way to achieve this is by increasing the operating temperature of gas turbines. Therefore, nickel-based superalloys have been developed to withstand these extreme temperatures and loads, especially in the hot sections.Today, the way of operating land-based gas turbines is changing. Instead of running for long periods of time, the operation is becoming more flexible, with everincreasing cyclic loads and number of start and stop cycles. To handle the increased stress and cycles, component resistance to fatigue failure needs to be improved.Surface integrity is critical to fatigue performance, since fatigue cracks are normally initiated at surfaces. Nickel-based superalloys are difficult-to-machine materials, primarily due to their high strength, high tendency for work-hardening, and low thermal conductivity. The machining process changes the surface integrity of the alloys which can result in worse fatigue resistance.The work presented in this Ph.D. thesis was conducted in collaboration with Siemens Industrial Turbomachinery AB in Finspång, Sweden. Surface integrity changes which are induced during machining and their effects on fatigue performance have been studied on alloy Inconel 718. Inconel 718 is a widely-used nickel-based superalloy for high temperature applications in modern gas turbines.Broaching, milling, and wire electrical discharge machining, related to component manufacturing in turbo machinery industries, were included in this study. Surface irregularity and defects induced by machining provide preferential sites for fatigue crack initiation which influence the fatigue performance of the alloy. If compressive residual stresses are induced during machining, they benefit the fatigue life by retarding fatigue crack initiation away from surface regions. Shot peening was performed on machined Inconel 718, by which high compressive residual stresses are deliberately induced. It results in increased fatigue performance. The high iv temperatures in gas turbines generally deteriorate the surface integrity. For instance, recrystallization often occurs in the highly plastically-deformed surface layer. Microstructural degradation, in a form of α-Cr precipitates, have also been observed in the deformed surface and sub-surface microstructure when subjected to thermal exposure. Oxidation at elevated temperatures was found to degrade the surface integrity and thereby also the fatigue performance. Fatigue cracks are preferably initiated at oxidized surface carbides, if thermal exposure has been made prior to the test, and a reduced fatigue life is often obtained. It is even worse when high temperatures relax the beneficial compressive residual stresses induced by shotpeening and thereby lowering the fatigue resistance. This increases the interest for research regarding how to optimize the shot peening process in order to enhance the thermal stability o...

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On the conjoint influence of broaching and heat treatment on bending fatigue behavior of Inconel 718

Cited by 14 publications

References 34 publications

Effects of process combinations of milling, grinding, and polishing on the surface integrity and fatigue life of GH4169 components

Effects of process combinations of milling, grinding, and polishing on the surface integrity and fatigue life of GH4169 components

Effects of Machining Induced Residual Shear and Normal Stresses on Fatigue Life and Stress Intensity Factor of Inconel 718

Surface Integrity and Fatigue Performance of Nickel-based Superalloys

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