Characterizing the effects of laser control in laser powder bed fusion on near-surface pore formation via combined analysis of in-situ melt pool monitoring and X-ray computed tomography

2021 ◽  
Vol 48 ◽  
pp. 102372
Author(s):  
F.H. Kim ◽  
H. Yeung ◽  
E.J. Garboczi
Keyword(s):  
Pore Formation ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Near Surface ◽  
Powder Bed ◽  
X Ray ◽  
Melt Pool ◽  
X Ray Computed ◽  
Laser Control

scholarly journals In Situ Analysis of Laser Powder Bed Fusion Using Simultaneous High-Speed Infrared and X-ray Imaging

JOM ◽  
2020 ◽  
Vol 73 (1) ◽  
pp. 201-211 ◽  
Author(s):  
Benjamin Gould ◽  
Sarah Wolff ◽  
Niranjan Parab ◽  
Cang Zhao ◽  
Maria Cinta Lorenzo-Martin ◽  
...  
Keyword(s):  
High Speed ◽  
In Situ Analysis ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
X Ray ◽  
X Ray Imaging

scholarly journals Synchrotron Characterisation of Ultra-Fine Grain TiB2/Al-Cu Composite Fabricated by Laser Powder Bed Fusion

2021 ◽  
Author(s):  
Sheng Li ◽  
Biao Cai ◽  
Ranxi Duan ◽  
Lei Tang ◽  
Zihan Song ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Tensile Loading ◽  
Fusion Pore ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
X Ray ◽  
Random Texture ◽  
Average Grain Size

AbstractIsotropy in microstructure and mechanical properties remains a challenge for laser powder bed fusion (LPBF) processed materials due to the epitaxial growth and rapid cooling in LPBF. In this study, a high-strength TiB2/Al-Cu composite with random texture was successfully fabricated by laser powder bed fusion (LPBF) using pre-doped TiB2/Al-Cu composite powder. A series of advanced characterisation techniques, including synchrotron X-ray tomography, correlative focussed ion beam–scanning electron microscopy (FIB-SEM), scanning transmission electron microscopy (STEM), and synchrotron in situ X-ray diffraction, were applied to investigate the defects and microstructure of the as-fabricated TiB2/Al-Cu composite across multiple length scales. The study showed ultra-fine grains with an average grain size of about 0.86 μm, and a random texture was formed in the as-fabricated condition due to rapid solidification and the TiB2 particles promoting heterogeneous nucleation. The yield strength and total elongation of the as-fabricated composite were 317 MPa and 10%, respectively. The contributions of fine grains, solid solutions, dislocations, particles, and Guinier–Preston (GP) zones were calculated. Failure was found to be initiated from the largest lack-of-fusion pore, as revealed by in situ synchrotron tomography during tensile loading. In situ synchrotron diffraction was used to characterise the lattice strain evolution during tensile loading, providing important data for the development of crystal-plasticity models.

scholarly journals In Situ Thermography During Laser Powder Bed Fusion of a Nickel Superalloy 625 Artifact with Various Overhangs and Supports

2021 ◽  
Vol 126 ◽  
Author(s):  
Benjamin Molnar ◽  
Jarred C. Heigel ◽  
Eric Whitenton
Keyword(s):  
Cooling Rate ◽  
High Speed ◽  
Nickel Superalloy ◽  
Powder Bed Fusion ◽  
Support Structures ◽  
Radiance Temperature ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Melt Pool

This document provides details on the experiment and associated measurement files available fordownload in the dataset “In Situ Thermography During Laser Powder Bed Fusion of a Nickel Superalloy 625 Artifact with Various Overhangs and Supports.” The measurements were acquired during the fabrication of a small nickel superalloy 625 (IN625) artifact using a commercial laser powder bed fusion (LPBF) system. The artifact consists of two half-arch features with increasing slopes for overhangs. These overhangs range from 5° from vertical to 85° from vertical in increments of 10°. The artifact geometry and process are controlled to ensure consistent processing along the overhang geometry. This control enables the effect of overhang geometry and support structures to be isolated from effects of inter-layer scan strategy variations. The measurements include high-speed thermography of each layer, from which radiance temperature, cooling rate, and melt pool length are calculated.

scholarly journals Cooling dynamics of two titanium alloys during laser powder bed fusion probed with in situ X-ray imaging and diffraction

2020 ◽  
Vol 195 ◽  
pp. 108987
Author(s):  
Nicholas P. Calta ◽  
Vivek Thampy ◽  
Duncan R.C. Lee ◽  
Aiden A. Martin ◽  
Rishi Ganeriwala ◽  
...  
Keyword(s):  
Titanium Alloys ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
X Ray ◽  
X Ray Imaging

scholarly journals In-Situ Characterization of Pore Formation Dynamics in Pulsed Wave Laser Powder Bed Fusion

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2936
Author(s):  
Seyed Mohammad H. Hojjatzadeh ◽  
Qilin Guo ◽  
Niranjan D. Parab ◽  
Minglei Qu ◽  
Luis I. Escano ◽  
...  
Keyword(s):  
Pore Formation ◽  
Continuous Wave ◽  
Formation Mechanisms ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Subsequent Formation ◽  
Powder Bed ◽  
Formation Dynamics ◽  
Wave Laser

Laser powder bed fusion (LPBF) is an additive manufacturing technology with the capability of printing complex metal parts directly from digital models. Between two available emission modes employed in LPBF printing systems, pulsed wave (PW) emission provides more control over the heat input compared to continuous wave (CW) emission, which is highly beneficial for printing parts with intricate features. However, parts printed with pulsed wave LPBF (PW-LPBF) commonly contain pores, which degrade their mechanical properties. In this study, we reveal pore formation mechanisms during PW-LPBF in real time by using an in-situ high-speed synchrotron x-ray imaging technique. We found that vapor depression collapse proceeds when the laser irradiation stops within one pulse, resulting in occasional pore formation during PW-LPBF. We also revealed that the melt ejection and rapid melt pool solidification during pulsed-wave laser melting resulted in cavity formation and subsequent formation of a pore pattern in the melted track. The pore formation dynamics revealed here may provide guidance on developing pore elimination approaches.

scholarly journals Linking In Situ Melt Pool Monitoring to Melt Pool Size Distributions and Internal Flaws in Laser Powder Bed Fusion

Metals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1856
Author(s):  
Claudia Schwerz ◽  
Lars Nyborg
Keyword(s):  
Near Infrared ◽  
In Situ Monitoring ◽  
Ex Situ ◽  
Process Conditions ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Melt Pool ◽  
Melt Pool Size

In situ monitoring of the melt pools in laser powder bed fusion (LPBF) has enabled the elucidation of process phenomena. There has been an increasing interest in also using melt pool monitoring to identify process anomalies and control the quality of the manufactured parts. However, a better understanding of the variability of melt pools and the relation to the incidence of internal flaws are necessary to achieve this goal. This study aims to link distributions of melt pool dimensions to internal flaws and signal characteristics obtained from melt pool monitoring. A process mapping approach is employed in the manufacturing of Hastelloy X, comprising a vast portion of the process space. Ex situ measurements of melt pool dimensions and analysis of internal flaws are correlated to the signal obtained through in situ melt pool monitoring in the visible and near-infrared spectra. It is found that the variability in melt pool dimensions is related to the presence of internal flaws, but scatter in melt pool dimensions is not detectable by the monitoring system employed in this study. The signal intensities are proportional to melt pool dimensions, and the signal is increasingly dynamic following process conditions that increase the generation of spatter.

Computational Investigation of Melt Pool Process Dynamics and Pore Formation in Laser Powder Bed Fusion

2019 ◽  
Vol 28 (11) ◽  
pp. 6565-6578 ◽  
Author(s):  
Bo Cheng ◽  
Lukas Loeber ◽  
Hannes Willeck ◽  
Udo Hartel ◽  
Charles Tuffile
Keyword(s):  
Pore Formation ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Computational Investigation ◽  
Powder Bed ◽  
Process Dynamics ◽  
Melt Pool

scholarly journals In Situ Alloying of a Modified Inconel 625 via Laser Powder Bed Fusion: Microstructure and Mechanical Properties

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 988
Author(s):  
Giulio Marchese ◽  
Margherita Beretta ◽  
Alberta Aversa ◽  
Sara Biamino
Keyword(s):  
Mechanical Properties ◽  
Base Alloy ◽  
Heat Treatments ◽  
Inconel 625 ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Melt Pool ◽  
Composition Modification

This study investigates the in situ alloying of a Ni-based superalloy processed by means of laser powder bed fusion (LPBF). For this purpose, Inconel 625 powder is mixed with 1 wt.% of Ti6Al4V powder. The modified alloy is characterized by densification levels similar to the base alloy, with relative density superior to 99.8%. The material exhibits Ti-rich segregations along the melt pool contours. Moreover, Ti tends to be entrapped in the interdendritic areas during solidification in the as-built state. After heat treatments, the modified Inconel 625 version presents greater hardness and tensile strengths than the base alloy in the same heat-treated conditions. For the solution annealed state, this is mainly attributed to the elimination of the segregations into the interdendritic structures, thus triggering solute strengthening. Finally, for the aged state, the further increment of mechanical properties can be attributed to a more intense formation of phases than the base alloy, due to elevated precipitation strengthening ability under heat treatments. It is interesting to note how slight chemical composition modification can directly develop new alloys by the LPBF process.

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