Influence of surface conditions and specimen orientation on high cycle fatigue properties of Inconel 718 prepared by laser powder bed fusion

Witkin, David B.; Patel, Dhruvil; Albright, Thomas V.; Bean, Glenn E.; McLouth, Tait D.

doi:10.1016/j.ijfatigue.2019.105392

Cited by 66 publications

(23 citation statements)

References 44 publications

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“…Numerous studies focus on the randomly dispersed defects, the microstructure heterogeneity and the anisotropic mechanical properties for SLM materials [ 5 , 6 ]. Although IN718 is widely used in the high-temperature environment and is often subjected to cyclic loading, previous studies mainly focused on the fatigue behavior at room temperature (RT).…”

Section: Introductionmentioning

confidence: 99%

Very-High-Cycle Fatigue Behavior of Inconel 718 Alloy Fabricated by Selective Laser Melting at Elevated Temperature

et al. 2021

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This study investigates the very-high-cycle fatigue (VHCF) behavior at elevated temperature (650 °C) of the Inconel 718 alloy fabricated by selective laser melting (SLM). The results are compared with those of the wrought alloy. Large columnar grain with a cellular structure in the grain interior and Laves/δ phases precipitated along the grain boundaries were exhibited in the SLM alloy, while fine equiaxed grains were present in the wrought alloy. The elevated temperature had a minor effect on the fatigue resistance in the regime below 108 cycles for the SLM alloy but significantly reduced the fatigue strength in the VHCF regime above 108 cycles. Both the SLM and wrought specimens exhibited similar fatigue resistance in the fatigue life regime of fewer than 107–108 cycles at elevated temperature, and the surface initiation mechanism was dominant in both alloys. In a VHCF regime above 107–108 cycles at elevated temperature, the wrought material exhibited slightly better fatigue resistance than the SLM alloy. All fatigue cracks are initiated from the internal defects or the microstructure discontinuities. The precipitation of Laves and δ phases is examined after fatigue tests at high temperatures, and the effect of microstructure on the formation and the propagation of the microstructural small cracks is also discussed.

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Section: Introductionmentioning

confidence: 99%

Very-High-Cycle Fatigue Behavior of Inconel 718 Alloy Fabricated by Selective Laser Melting at Elevated Temperature

et al. 2021

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“…Because of the prospective advantages of Inconel718 produced via AM, the scientific research into the mechanical and fatigue performance of this superalloy has grown in recent years. The influence of internal defects and rough as-built surfaces on the high cycle fatigue (HCF) regime was investigated previously, [25][26][27] whereas the effect of microstructure on the LCF was investigated in other studies. 28,29 What emerges from these works is that for a reliable fatigue analysis, one cannot ignore the combined effect of manufacturing defects (internal and superficial) and the anisotropic mechanical behaviour due to the microstructure obtained.…”

Section: Introductionmentioning

confidence: 99%

Anisotropic mechanical and fatigue behaviour of Inconel718 produced by SLM in LCF and high‐temperature conditions

Sausto

Marchese

Bassini

et al. 2020

Fatigue Fract Eng Mat Struct

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Additive manufacturing (AM) is one of the processes with the most potential for producing components used in internal combustion engines and features high efficiency due to the possibility of building very complex shapes. Several drawbacks of parts produced using AM are still unresolved, like poor surface quality, the presence of internal defects and anisotropic mechanical behaviour, which all contribute to decreasing the fatigue strength compared with the material produced using conventional processes. The effect of building direction on both the macroscopic mechanical behaviour and the crack propagation mechanism of Ni-base superalloy Inconel718 produced using AM was investigated under the combined effect of low cycle fatigue (LCF) and high temperature. The different crack growth mechanisms investigated using compact tension (CT) specimens, tested at high temperature, showed a significant difference between the two building directions. The LCF fatigue experiments also showed a significant difference in the ε-N curves from the two directions together with a high level of scatter due to the dispersion of the defect size at the fracture origin. The dimensions of the defects (as measured using the ffiffiffiffiffiffiffiffiffi area p parameter) were analysed by means of extreme value statistics and showed a significant difference between the two orientations investigated. The aim of this work is to propose a simplified approach (based on ΔJ eff concepts) to estimate the fatigue life of a component produced using AM that takes into account the material variability due to the combined effect of mechanical anisotropic behaviour and the presence of defects at high-temperature conditions.

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“…15 In terms of anisotropy, the specimens manufactured horizontally display longer fatigue life than those manufactured vertically. 1,16,17 Hot isostatic pressing (HIP) can close internal porosity and has been reported to increase the fatigue strength to the same level as wrought 18 ; however, it has also been reported to reduce the strength due to microstructural effects. 19 Dealing with the influence of notches on the fatigue behaviour of AM Inconel 718, several different approaches have been made.…”

Section: Introductionmentioning

confidence: 99%

Fatigue assessment of as‐built and heat‐treated Inconel 718 specimens produced by additive manufacturing including notch effects

Solberg

Wan

2020

Fatigue Fract Eng Mat Struct

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The fatigue behaviour of notched and unnotched specimens produced by additively manufactured Inconel 718 were analysed in the as‐built and heat‐treated conditions. The surfaces display high roughness and defects acting as fatigue initiation sites. In the as‐built condition, fine subgrains were found, while in in the heat‐treated state, the subgrains were removed and the dislocation density recovered. SN‐curves are predicted based on tensile properties, hardness and defects obtained by fractography, using the area‐method.

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Influence of surface conditions and specimen orientation on high cycle fatigue properties of Inconel 718 prepared by laser powder bed fusion

Cited by 66 publications

References 44 publications

Very-High-Cycle Fatigue Behavior of Inconel 718 Alloy Fabricated by Selective Laser Melting at Elevated Temperature

Very-High-Cycle Fatigue Behavior of Inconel 718 Alloy Fabricated by Selective Laser Melting at Elevated Temperature

Anisotropic mechanical and fatigue behaviour of Inconel718 produced by SLM in LCF and high‐temperature conditions

Fatigue assessment of as‐built and heat‐treated Inconel 718 specimens produced by additive manufacturing including notch effects

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