Residual Stress in Selective Laser Melted Inconel 718: Influence of the Removal from Base Plate and Deposition Hatch Length

Thiede, Tobias; Cabeza, Sandra; Mishurova, Tatiana; Nadammal, Naresh; Kromm, Arne; Bode, Johannes; Haberland, Christoph; Bruno, Giovanni

doi:10.1520/mpc20170119

Cited by 38 publications

(42 citation statements)

References 32 publications

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“…Indeed, some studies show that the connection between part and base plate contribute to the residual stress state. [5,[30][31][32] In general, the scanning parameters during SLM have a significant influence on residual stress state, due to changes in the heat input and thermal gradient: The scanning strategy with smaller hatch length in similar IN718 SLM samples [20,33] has shown the highest gradient in longitudinal and transversal directions in comparison with longer hatch, because of more localized laser energy input; the increase of the laser energy density by means of smaller scanning speed has shown to decrease residual stresses. [17] In the present case, the support structure can also be viewed as a process parameter since its shape and size can be changed depending on the component and its purpose.…”

Section: Discussionmentioning

confidence: 99%

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The Influence of the Support Structure on Residual Stress and Distortion in SLM Inconel 718 Parts

Mishurova

Cabeza

Thiede

et al. 2018

Metall Mater Trans A

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The effect of support structure and of removal from the base plate on the residual stress state in selective laser melted IN718 parts was studied by means of synchrotron X-ray diffraction. The residual stresses in subsurface region of two elongated prisms in as-built condition and after removal from the base plate were determined. One sample was directly built on a base plate and another one on a support structure. Also, the distortion on the top surface due to stress release was measured by contact profilometry. High tensile residual stress values were found, with pronounced stress gradient along the hatching direction. In the sample on support, stress redistribution took place after removal from the base plate, as opposed to simple stress relaxation for the sample without support. The sample on support structure showed larger distortion compared to sample without support. We conclude that the use of a support decreases stress values but stress-relieving heat treatments are still needed.

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Section: Discussionmentioning

confidence: 99%

“…In fact, distortion can be used as an inexpensive and fast assessment of the amount of RS in the part, [17,18] as well as for quality assurance scopes. In comparison to bulk residual stress analysis by neutron diffraction, [19,20] synchrotron radiation diffraction allows RS investigations in subsurface regions (up to 100 lm depth).…”

Section: Introductionmentioning

confidence: 99%

The Influence of the Support Structure on Residual Stress and Distortion in SLM Inconel 718 Parts

Mishurova

Cabeza

Thiede

et al. 2018

Metall Mater Trans A

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“…Determining elastic strains by measuring the variation of lattice spacing provides a powerful method to identify RS. This is achieved at the surface by Lab X-ray Diffraction (XRD), up to a depth of about 5 µm in metals, as well as in the bulk by Neutron Diffraction (ND) up to a depth of about a few mm to a few cm [11][12][13]. In this work, the bulk triaxial RS state was determined using ND and was combined with the Lab XRD biaxial RS state at the surface.…”

Section: Introductionmentioning

confidence: 99%

Separation of the Formation Mechanisms of Residual Stresses in LPBF 316L

Ulbricht

Altenburg

Sprengel

et al. 2020

Metals

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Rapid cooling rates and steep temperature gradients are characteristic of additively manufactured parts and important factors for the residual stress formation. This study examined the influence of heat accumulation on the distribution of residual stress in two prisms produced by Laser Powder Bed Fusion (LPBF) of austenitic stainless steel 316L. The layers of the prisms were exposed using two different border fill scan strategies: one scanned from the centre to the perimeter and the other from the perimeter to the centre. The goal was to reveal the effect of different heat inputs on samples featuring the same solidification shrinkage. Residual stress was characterised in one plane perpendicular to the building direction at the mid height using Neutron and Lab X-ray diffraction. Thermography data obtained during the build process were analysed in order to correlate the cooling rates and apparent surface temperatures with the residual stress results. Optical microscopy and micro computed tomography were used to correlate defect populations with the residual stress distribution. The two scanning strategies led to residual stress distributions that were typical for additively manufactured components: compressive stresses in the bulk and tensile stresses at the surface. However, due to the different heat accumulation, the maximum residual stress levels differed. We concluded that solidification shrinkage plays a major role in determining the shape of the residual stress distribution, while the temperature gradient mechanism appears to determine the magnitude of peak residual stresses.

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“…Not only laser parameters and scanning strategy [7,21] must be taken into account, but also other factors basically poorly explored in the open literature such as the position on the base plate, the laser path, or the Argon flow [13]. Those factors cannot always be captured by simulations and sometimes are not experimentally measurable.…”

Section: Introductionmentioning

confidence: 99%

Exploring the Correlation between Subsurface Residual Stresses and Manufacturing Parameters in Laser Powder Bed Fused Ti-6Al-4V

Mishurova

Artzt

Haubrich

et al. 2019

Metals

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Subsurface residual stresses (RS) were investigated in Ti-6Al-4V cuboid samples by means of X-ray synchrotron diffraction. The samples were manufactured by laser powder bed fusion (LPBF) applying different processing parameters, not commonly considered in open literature, in order to assess their influence on RS state. While investigating the effect of process parameters used for the calculation of volumetric energy density (such as laser velocity, laser power and hatch distance), we observed that an increase of energy density led to a decrease of RS, although not to the same extent for every parameter variation. Additionally, the effect of support structure, sample roughness and LPBF machine effects potentially coming from Ar flow were studied. We observed no influence of support structure on subsurface RS while the orientation with respect to Ar flow showed to have an impact on RS. We conclude recommending monitoring such parameters to improve part reliability and reproducibility.

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Residual Stress in Selective Laser Melted Inconel 718: Influence of the Removal from Base Plate and Deposition Hatch Length

Cited by 38 publications

References 32 publications

The Influence of the Support Structure on Residual Stress and Distortion in SLM Inconel 718 Parts

The Influence of the Support Structure on Residual Stress and Distortion in SLM Inconel 718 Parts

Separation of the Formation Mechanisms of Residual Stresses in LPBF 316L

Exploring the Correlation between Subsurface Residual Stresses and Manufacturing Parameters in Laser Powder Bed Fused Ti-6Al-4V

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