Impact of annealing treatment on the fatigue behavior of Inconel 625 produced by laser‐based powder bed fusion

The fatigue behaviour of an AlSi10Mg alloy processed by laser powder bed fusion (L-PBF) and subjected to different surface finishing processes was investigated paying special attention to the residual defects on the surface and the dominant fatigue failure mechanisms. Roughness measurements and qualitative surface morphology analysis showed smooth surfaces in the case of vibro-finishing and machining followed by polishing. The fatigue performance did not reveal to be directly related to surface roughness, but residual intrusions left on the finished surfaces. Post-mortem analysis showed single- or multiple-crack nucleation from pores opened on the surface, un-melted powders, or spatters considered as typical L-PBF defects. A fatigue limit of 195 MPa for machined and polished samples was obtained by substantial removal of surface and subsurface defects.

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Fatigue strength prediction of laser powder bed fusion processed Inconel 625 specimens with intentionally-seeded porosity: Feasibility study

International Journal of Fatigue ◽

10.1016/j.ijfatigue.2019.105394 ◽

2020 ◽

Vol 132 ◽

pp. 105394 ◽

Cited By ~ 2

Author(s):

J.-R. Poulin ◽

A. Kreitcberg ◽

P. Terriault ◽

V. Brailovski

Keyword(s):

Fatigue Strength ◽

Feasibility Study ◽

Inconel 625 ◽

Strength Prediction ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Powder Bed

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In situ microstructure analysis of Inconel 625 during laser powder bed fusion

Journal of Materials Science ◽

10.1007/s10853-021-06577-8 ◽

2021 ◽

Author(s):

Felix Schmeiser ◽

Erwin Krohmer ◽

Christian Wagner ◽

Norbert Schell ◽

Eckart Uhlmann ◽

...

Keyword(s):

Laser Power ◽

Scanning Speed ◽

High Energy ◽

Mechanical Anisotropy ◽

Ex Situ ◽

Inconel 625 ◽

Powder Bed Fusion ◽

Laser Powder Bed Fusion ◽

Powder Bed

AbstractLaser powder bed fusion is an additive manufacturing process that employs highly focused laser radiation for selective melting of a metal powder bed. This process entails a complex heat flow and thermal management that results in characteristic, often highly textured microstructures, which lead to mechanical anisotropy. In this study, high-energy X-ray diffraction experiments were carried out to illuminate the formation and evolution of microstructural features during LPBF. The nickel-base alloy Inconel 625 was used for in situ experiments using a custom LPBF system designed for these investigations. The diffraction patterns yielded results regarding texture, lattice defects, recrystallization, and chemical segregation. A combination of high laser power and scanning speed results in a strong preferred crystallographic orientation, while low laser power and scanning speed showed no clear texture. The observation of a constant gauge volume revealed solid-state texture changes without remelting. They were related to in situ recrystallization processes caused by the repeated laser scanning. After recrystallization, the formation and growth of segregations were deduced from an increasing diffraction peak asymmetry and confirmed by ex situ scanning transmission electron microscopy. Graphical Abstract

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Fatigue Improvement of AlSi10Mg Fabricated by Laser-Based Powder Bed Fusion through Heat-Treatment.

10.20944/preprints202104.0075.v1 ◽

2021 ◽

Author(s):

Felix Sajadi ◽

Jan-Marc Tiemann ◽

Nooshin Bandari ◽

Ali Cheloee Darabi ◽

Javad Mola ◽

...

Keyword(s):

Heat Treatment ◽

Fatigue Behavior ◽

Fatigue Properties ◽

Powder Bed Fusion ◽

Microstructural Characteristics ◽

Powder Bed ◽

Treated Condition ◽

Heat Treated ◽

Treatment Parameter ◽

Heat Treated Condition

This study aims to identify an optimal heat-treatment parameter set for an additively manufactured AlSi10Mg alloy in terms of increasing the hardness and eliminating the anisotropic microstructural characteristics of the alloy in as-built condition. Furthermore, the influence of these optimized parameters on the fatigue properties of the alloy investigated. In this respect, microstructural characteristics of an AlSi10Mg alloy manufactured by Laser-Based Powder Bed Fusion in non-heat-treated and heat-treated conditions were investigated. Their static and dynamic mechanical properties were evaluated, and fatigue behavior was explained by a detailed examination of fracture surfaces. Much of the microstructure in the non-heat-treated condition was composed of columnar grains oriented parallel to the build direction. Further analysis revealed a high fraction of pro-eutectic α-Al. Through heat-treatment, the alloy was successfully brought to its peak-hardened condition, while eliminating the anisotropic microstructural features. Yield strength and ductility increased simultaneously after heat-treatment, which is due to the relief of residual stresses, preservation of refined grains, and introduction of precipitation strengthening. The fatigue strength, calculated at 10^7 cycles, improved as well after heat-treatment and finally detailed fractography reviled that a more ductile fracture mechanism has happened in the heat-treated condition compared to the non-heat-treated condition.

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