scholarly journals Influence of Pulsed Exposure Strategies on Overhang Structures in Powder Bed Fusion of Ti6Al4V Using Laser Beam

Metals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1125
Author(s):  
Jonas Grünewald ◽  
Pirmin Clarkson ◽  
Ryan Salveson ◽  
Georg Fey ◽  
Katrin Wudy
Keyword(s):  
Surface Roughness ◽  
Energy Density ◽  
Laser Beam ◽  
Continuous Wave ◽  
Scanning Speed ◽  
Powder Bed Fusion ◽  
Powder Bed ◽  
Volume Energy ◽  
Pulsed Exposure ◽  
Overhang Angle

Manufacturing structures with low overhang angles without support structures is a major challenge in powder bed fusion of metals using laser beam (PBF-LB/M). In the present work, various test specimens and parameter sets with continuous wave (cw) and pulsed exposure are used to investigate whether a reduction of downskin roughness and overhang angle can be achieved in PBF-LB/M of Ti6Al4V. Starting from cw exposure, the limits of overhang angle and surface roughness at the downskin surface are investigated as a reference. Subsequently, the influence of laser power, scanning speed, and hatch distance with fixed pulse duration (τpulse = 25 µs) and repetition rate (υrep = 20 kHz) on surface roughness Ra is investigated. Pulsed exposure strategies enable the manufacturing of flatter overhang angles (≤20° instead of ≥25°). Furthermore, a correlation between the introduced volume energy density and the downskin roughness can be observed for pulsed exposure. As the reduction in volume energy density causes an increase in porosity, the combination of pulsed downskin exposure and commercial cw infill exposure is investigated. The larger the gap in volume energy density between the infill area and downskin area, the more challenging it is combining the two parameter sets. By combining cw infill and pulsed downskin exposure, flatter overhang structures cannot be manufactured, and a reduction in roughness can be achieved.

scholarly journals On the Relevance of Volumetric Energy Density in the Investigation of Inconel 718 Laser Powder Bed Fusion

Materials ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 538 ◽  
Author(s):  
Fabrizia Caiazzo ◽  
Vittorio Alfieri ◽  
Giuseppe Casalino
Keyword(s):  
Surface Roughness ◽  
Energy Density ◽  
Process Parameters ◽  
Vickers Hardness ◽  
Powder Bed Fusion ◽  
Processing Conditions ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Fractional Density ◽  
Experimental Variation

Laser powder bed fusion (LPBF) can fabricate products with tailored mechanical and surface properties. In fact, surface texture, roughness, pore size, the resulting fractional density, and microhardness highly depend on the processing conditions, which are very difficult to deal with. Therefore, this paper aims at investigating the relevance of the volumetric energy density (VED) that is a concise index of some governing factors with a potential operational use. This paper proves the fact that the observed experimental variation in the surface roughness, number and size of pores, the fractional density, and Vickers hardness can be explained in terms of VED that can help the investigator in dealing with several process parameters at once.

scholarly journals Mesoscopic simulation of overlapping behavior in laser powder bed additive manufacturing

2021 ◽  
Author(s):  
Pan Lu ◽  
Liu Tong ◽  
Wang Wen-hao ◽  
Gao Yu ◽  
Zhang Cheng-lin ◽  
...  
Keyword(s):  
Energy Density ◽  
Molten Pool ◽  
Laser Power ◽  
Laser Scanning ◽  
Flow Behavior ◽  
Pure Copper ◽  
Scanning Speed ◽  
Powder Bed ◽  
Volume Energy ◽  
Laser Scanning Speed

Abstract The prediction of the flow behavior of Metal micro-molten pool is prerequisite for high-quality Laser Powder Bed Fusion (L-PBF). In this study, mesoscopic scale numerical simulation modelling for L-PBF process was used to help understand the melting process of pure copper micro-melt pool.In this study, the orthogonal test was designed to study the influence of laser power, laser scanning velocity, hatching space on the flow behavior of molten pool and the overlapping rate of adjacent molten tracks. The results shows that laser scanning speed has the greatest influence on both the size and overlapping rate of the molten pool, and the overall trend was that the size of molten pool continues to increase as the volume energy density increases, and the maximum molten pool size was 243.6um × 110um with volume energy density 370.037 J/mm3, overlapping rate of adjacent molten tracks was 48.84% with volume energy density 285.71 J/mm3. The optimized pure copper laser process parameters were obtained: laser power 300 KW, laser scanning speed 500 mm/s, hatching space 0.07mm, overlapping rate 48.84%.

scholarly journals Carbon Particle In-Situ Alloying of the Case-Hardening Steel 16MnCr5 in Laser Powder Bed Fusion

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 896
Author(s):  
Matthias Schmitt ◽  
Albin Gottwalt ◽  
Jakob Winkler ◽  
Thomas Tobie ◽  
Georg Schlick ◽  
...  
Keyword(s):  
Laser Beam ◽  
Mechanical Strength ◽  
Carbon Content ◽  
Metal Powder ◽  
Case Hardening ◽  
Powder Bed Fusion ◽  
Powder Bed ◽  
Carbon Particles ◽  
Case Hardening Steel

The carbon content of steel affects many of its essential properties, e.g., hardness and mechanical strength. In the powder bed fusion process of metals using a laser beam (PBF-LB/M), usually, pre-alloyed metal powder is solidified layer-by-layer using a laser beam to create parts. A reduction of the carbon content in steels is observed during this process. This study examines adding carbon particles to the metal powder and in situ alloying in the PBF-LB/M process as a countermeasure. Suitable carbon particles are selected and their effect on the particle size distribution and homogeneity of the mixtures is analysed. The workability in PBF-LB is then shown. This is followed by an evaluation of the resulting mechanical properties (hardness and mechanical strength) and microstructure in the as-built state and the state after heat treatment. Furthermore, potential use cases like multi-material or functionally graded parts are discussed.

Establishing Specimen Property to Part Performance Relationships for Laser Beam Powder Bed Fusion Additive Manufacturing

2021 ◽  
pp. 106384
Author(s):  
Arash Soltani-Tehrani ◽  
Rakish Shrestha ◽  
Nam Phan ◽  
Mohsen Seifi ◽  
Nima Shamsaei
Keyword(s):  
Additive Manufacturing ◽  
Laser Beam ◽  
Powder Bed Fusion ◽  
Powder Bed

scholarly journals Optimization of Laser Powder Bed Fusion Processing Using a Combination of Melt Pool Modeling and Design of Experiment Approaches: Density Control

2019 ◽  
Vol 3 (1) ◽  
pp. 21 ◽  
Author(s):  
Morgan Letenneur ◽  
Alena Kreitcberg ◽  
Vladimir Brailovski
Keyword(s):  
Scanning Speed ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Density Prediction ◽  
Melt Pool ◽  
Density Control ◽  
Pool Model ◽  
Conventional Material ◽  
Prediction Approach

A simplified analytical model of the laser powder bed fusion (LPBF) process was used to develop a novel density prediction approach that can be adapted for any given powder feedstock and LPBF system. First, calibration coupons were built using IN625, Ti64 and Fe powders and a specific LPBF system. These coupons were manufactured using the predetermined ranges of laser power, scanning speed, hatching space, and layer thickness, and their densities were measured using conventional material characterization techniques. Next, a simplified melt pool model was used to calculate the melt pool dimensions for the selected sets of printing parameters. Both sets of data were then combined to predict the density of printed parts. This approach was additionally validated using the literature data on AlSi10Mg and 316L alloys, thus demonstrating that it can reliably be used to optimize the laser powder bed metal fusion process.

Improvement of Build Speed and Quality of H13 Tool Steel Processed by Laser-Beam Powder Bed Fusion with a High-Power Laser

2021 ◽  
Vol 68 (10) ◽  
pp. 415-421
Author(s):  
Takashi MIZOGUCHI ◽  
Takaya NAGAHAMA ◽  
Makoto TANO ◽  
Shigeru MATSUNAGA ◽  
Takayuki YOSHIMI ◽  
...  
Keyword(s):  
Laser Beam ◽  
Tool Steel ◽  
High Power ◽  
Powder Bed Fusion ◽  
High Power Laser ◽  
Power Laser ◽  
Powder Bed ◽  
H13 Tool Steel

Multi-Objective Build Orientation Optimization for Powder Bed Fusion by Laser

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
Salah Eddine Brika ◽  
Yaoyao Fiona Zhao ◽  
Mathieu Brochu ◽  
Justin Mezzetta
Keyword(s):  
Mechanical Properties ◽  
Surface Roughness ◽  
Integrated Approach ◽  
Powder Bed Fusion ◽  
Powder Bed ◽  
Build Orientation ◽  
Multi Objective ◽  
Build Time ◽  
Process Factors ◽  
Experimental Data Analysis

This paper proposes an integrated approach to determine optimal build orientation for powder bed fusion by laser (PBF-L), by simultaneously optimizing mechanical properties, surface roughness, the amount of support structure (SUPP), and build time and cost. Experimental data analysis has been used to establish the objective functions for different mechanical properties and surface roughness. Geometry analysis of the part has been used to estimate the needed SUPP and thus evaluate the build time and cost. Normalized weights are assigned to different objectives depending on their relative importance allowing solving the multi-objective optimization problem using a genetic optimization algorithm. A study case is presented to demonstrate the capabilities of the developed system. The major achievements of this work are the consideration of multiple objectives and the establishment of objective function considering different load direction and heat treatments. A user-friendly graphical user interface was developed allowing to control different optimization process factors and providing different visualization and evaluation tools.

scholarly journals Roadmap for Additive Manufacturing of Haynes® 282® Superalloy by Laser Beam Powder Bed Fusion (PBF-LB) Technology

2020 ◽  
Author(s):  
Robert Otto ◽  
Vegard Brøtan ◽  
Patricia Almeida Carvalho ◽  
Magnus Reiersen ◽  
Joachim Seland Graff ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Laser Beam ◽  
Powder Bed Fusion ◽  
Powder Bed

scholarly journals PBF-LB Process-Induced Regular Cavities for Lightweight AlSi10Mg Structures

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6665
Author(s):  
Victor Lubkowitz ◽  
Jonas Alber ◽  
Frederik Zanger
Keyword(s):  
Laser Beam ◽  
Pore Formation ◽  
Powder Bed Fusion ◽  
Powder Bed ◽  
Lack Of Fusion ◽  
Keyhole Effect ◽  
Pore Types ◽  
Induced Defects

In powder bed fusion with laser beam (PBF-LB), two process-induced defects by pore formation are known: local spherical pores by the keyhole effect and geometrically undefined pores caused by lack of fusion. Both pore types are heterogeneously distributed and can be used for lightweight or damping design applications. The achievable porosity is limited to around 13%. This article presents a novel process-controlled method enabling the targeted and reproducible manufacturing of solid parts with regularly distributed cavities, currently up to 60% porosity in AlSi10Mg, using the balling effect. This eliminates the need for time-consuming digital pre-processing work.

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