scholarly journals Spatter Formation and Splashing Induced Defects in Laser-Based Powder Bed Fusion of AlSi10Mg Alloy: A Novel Hydrodynamics Modelling with Empirical Testing

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 2023
Author(s):  
Asif Ur Rehman ◽  
Muhammad Arif Mahmood ◽  
Peyman Ansari ◽  
Fatih Pitir ◽  
Metin Uymaz Salamci ◽  
...  
Keyword(s):  
High Speed ◽  
Laser Scanning ◽  
Scanning Speed ◽  
Operating Conditions ◽  
Powder Layer ◽  
Hydraulic Pressure ◽  
Powder Bed ◽  
Vapor Cloud ◽  
Laser Scanning Speed ◽  
Material Interaction

Powder spattering and splashing in the melt pool are common phenomena during Laser-based Powder Bed Fusion (LPBF) of metallic materials having high fluidity. For this purpose, analytical and computational fluid dynamics (CFD) models have been deduced for the LPBF of AlSi10Mg alloy. The single printed layer’s dimensions were estimated using primary operating conditions for the analytical model. In CFD modelling, the volume of fluid and discrete element modelling techniques were applied to illustrate the splashing and spatter phenomena, providing a novel hydrodynamics CFD model for LPBF of AlSi10Mg alloy. The computational results were compared with the experimental analyses. A trial-and-error method was used to propose an optimized set of parameters for the LPBF of AlSi10Mg alloy. Laser scanning speed, laser spot diameter and laser power were changed. On the other hand, the powder layer thickness and hatch distance were kept constant. Following on, 20 samples were fabricated using the LPBF process. The printed samples’ microstructures were used to select optimized parameters for achieving defect-free parts. It was found that the recoil pressure, vaporization, high-speed vapor cloud, Marangoni flow, hydraulic pressure and buoyancy are all controlled by the laser-material interaction time. As the laser-AlSi10Mg material interaction period progresses, the forces presented above become dominant. Splashing occurs due to a combination of increased recoil pressure, laser-material interaction time, higher material’s fluidity, vaporization, dominancy of Marangoni flow, high-speed vapor cloud, hydraulic pressure, buoyancy, and transformation of keyhole from J-shape to reverse triangle-shape that is a tongue-like protrusion in the keyhole. In the LPBF of AlSi10Mg alloy, only the conduction mode melt flow has been determined. For multi-layers printing of AlSi10Mg alloy, the optimum operating conditions are laser power = 140 W, laser spot diameter = 180 µm, laser scanning speed = 0.6 m/s, powder layer thickness = 50 µm and hatch distance = 112 µm. These conditions have been identified using sample microstructures.

Dissolution Behavior of Cast WC Particles in NiCrBSi-WC Coatings by Laser Induction Hybrid Cladding

2013 ◽  
Vol 668 ◽  
pp. 283-287
Author(s):  
Sheng Feng Zhou ◽  
Xiao Qin Dai
Keyword(s):  
High Speed ◽  
Laser Scanning ◽  
Metallic Matrix ◽  
High Hardness ◽  
Scanning Speed ◽  
Eutectic Structure ◽  
Dissolution Behavior ◽  
Positive Role ◽  
Laser Scanning Speed ◽  
Laser Induction

In order to characterize the dissolution of cast WC particles in Ni-based WC coatings by laser induction hybrid rapid cladding, NiCrBSi+50 wt.% WC coatings are produced on A3 steel by low and high speed laser induction hybrid cladding (LIHC). When laser scanning speed is only 600 mm/min, the crack-free coating has pores and its dilution is as high as 45%. At the bottom of coating, the cast WC particles are dissolved completely and the herringbone M6C eutectics are precipitated. In the center of coating, the cast WC particles are also dissolved completely and the acicular, blocky and dendritic carbides with relatively low hardness are precipitated. At two sides of coating, some cast WC particles are dissolved partially and interact with Ni-based alloy to form an alloyed reaction layer, while others preserve the primary eutectic structure and high hardness. When laser scanning speed and powder feeding rate are increased to 1500 mm/min and 85.6 g/min, the coating has cracks but no pores. Its dilution can be markedly decreased to 7.8%. Moreover, a majority of WC particles are still composed of primary eutectic structure and keep their high hardness, which can play a positive role in strengthening Ni-based metallic matrix.

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 Processability of Atypical WC-Co Composite Feedstock by Laser Powder-Bed Fusion

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 50 ◽  
Author(s):  
Mohaimen Al-Thamir ◽  
D. Graham McCartney ◽  
Marco Simonelli ◽  
Richard Hague ◽  
Adam Clare
Keyword(s):  
Laser Scanning ◽  
Single Layer ◽  
Scanning Speed ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Future Production ◽  
Laser Scanning Speed ◽  
First Time ◽  
Am Processes

Processing of tool materials for cutting applications presents challenges in additive manufacturing (AM). Processes must be carefully managed in order to promote the formation of favourable high-integrity ‘builds’. In this study, for the first time, a satelliting process is used to prepare a WCM-Co (12 wt.% Co) composite. Melting trials were undertaken to evaluate the consolidation behaviour of single tracks within a single layer. Tracks with continuous and relatively uniform surface morphology were obtained. These features are essential for high-quality AM builds in order to encourage good bonding between subsequent tracks within a layer which may reduce porosity within a 3D deposition. This study elucidates the formation of track irregularities, melting modes, crack sensitivity, and balling as a function of laser scanning speed and provides guidelines for future production of WCM-Co by laser powder-bed fusion.

Liquation and Crystallization Cracks in Aluminum Alloy AA2024 during Selective Laser Melting

2021 ◽  
Vol 410 ◽  
pp. 203-208
Author(s):  
I.S. Loginova ◽  
N.A. Popov ◽  
A.N. Solonin
Keyword(s):  
Aluminum Alloy ◽  
Selective Laser Melting ◽  
Laser Scanning ◽  
Scanning Speed ◽  
Melting Zone ◽  
Alloying Elements ◽  
Laser Melting ◽  
Laser Scanning Speed ◽  
Positive Effect

In this work we studied the microstructure and microhardness of standard AA2024 alloy and AA2024 alloy with the addition of 1.5% Y after pulsed laser melting (PLM) and selective laser melting (SLM). The SLM process was carried out with a 300 W power and 0.1 m/s laser scanning speed. A dispersed microstructure without the formation of crystallization cracks and low liquation of alloying elements was obtained in Y-modified AA2024 aluminum alloy. Eutectic Al3Y and Al8Cu4Y phases were detected in Y-modified AA2024 aluminum alloy. It is led to a decrease in the formation of crystallization cracks The uniform distribution of alloying elements in the yttrium-modified alloy had a positive effect on the quality of the laser melting zone (LMZ) and microhardness.

Formability of the Layer Additive Ceramic Part

2008 ◽  
Vol 594 ◽  
pp. 241-248 ◽  
Author(s):  
Fwu Hsing Liu ◽  
Yunn Shiuan Liao ◽  
Hsiu Ping Wang
Keyword(s):  
Surface Roughness ◽  
Laser Scanning ◽  
Selective Laser Sintering ◽  
Single Layer ◽  
Dimensional Accuracy ◽  
Scanning Speed ◽  
Laser Sintering ◽  
Single Line ◽  
Laser Scanning Speed ◽  
Silica Slurry

The material in powder state has long been used by selective laser sintering (SLS) for making rapid prototyping (RP) parts. A new approach to fabricate smoother surface roughness RP parts of ceramic material from slurry-sate has been developed in this study. The silica slurry was successfully laser-gelling in a self-developed laser sintering equipment. In order to overcome the insufficient bonding strength between layers, a strategy is proposed to generate ceramic parts from a single line, a single layer, to multi-layers of gelled cramic in this paper. It is found that when the overlap of each single line is 25% and the over-gel between layers is 30%, stronger and more accurate dimensional parts can be obtained under a laser power of 15W, a laser scanning speed of 250 mm/s, and a layer thickness of 0.1 mm. The 55:45 wt. % of the proportion between the silica powder and silica solution results in suitable viscosity of the ceramic slurries without precipitation. Furthermore, the effects of process parameters for the dimensional accuracy and surface roughness of the gelled parts are investigated and appropriate parameters are obtained.

Research on Microstructure and Wear Property of 45 Steel Quenched with Different Laser Power

2020 ◽  
Vol 861 ◽  
pp. 35-40
Author(s):  
Yu Liu ◽  
Tian Hao Xu ◽  
Ying Liu ◽  
Hai Cheng Zhang ◽  
Xing Xing Li ◽  
...  
Keyword(s):  
Laser Power ◽  
Laser Scanning ◽  
Scanning Speed ◽  
Wear Volume ◽  
Wear Property ◽  
Steel Matrix ◽  
Wear Properties ◽  
Laser Scanning Speed ◽  
Friction And Wear Properties ◽  
Minimum Wear

The surface of 45 steel is quenched by CO2 laser with scanning speed 1000 mm/min and different laser power 1000W, 1200W, 1400W, 1600W and 1800W. Experiments are carried out to analyze microstructure, friction and wear properties of quenched 45 steel. The results show that the quenching layer thickness increases gradually with the increase of laser power,and the maximum value of quenching layer hardness increases first and then decreases. When the laser power is 1600W, the maximum hardness value is 883HV0.5. But when the laser power is 1800W, the hardness of quenching layer becomes to decrease. The reason is the surface of 45 steel becomes to melt. The wear volume increases first and then decreases too. When laser power is 1600W, the minimum wear volume is 0.08mm3, which is 6.4% to the wear volume of 45 steel matrix without laser quenching. Therefore, better microstructure and properties of 45 steel can be obtained when laser scanning speed is 1000mm/min and laser power is 1600W.

scholarly journals The Effects of Laser Remelting on the Microstructure and Performance of Bainitic Steel

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 912 ◽  
Author(s):  
Yuelong Yu ◽  
Min Zhang ◽  
Yingchun Guan ◽  
Peng Wu ◽  
Xiaoyu Chong ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Laser Scanning ◽  
Production Efficiency ◽  
Scanning Speed ◽  
Bainitic Steel ◽  
Laser Remelting ◽  
Melted Layer ◽  
Laser Scanning Speed ◽  
And Performance ◽  
Nanoindentation Instrument

The surface of bainitic steel was remelted by fiber laser, and the microstructure and mechanical properties of the melted layer were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), a nanoindentation instrument, and wear equipment. The study of changing the laser scanning speed showed that the depth of the melted layer increases with decreases of the laser scanning speed. The wear-resistance property increased by 55% compared with the matrix and decreased with the reduction of laser scanning speed within a certain range. In the study of changing the laser-scanning space, the thermal effect of laser melting in the back channel on the front channel was further validated. At the same time, it was found that the solidified layer surface of hardness alternating with softness can be obtained by appropriately expanding the scanning space, which is conducive to improving the wear-resistant properties of the steel surface, and properly improving the production efficiency of the laser remelting treatment.

Experimental Evaluation of Blasting Near Pipelines

2018 ◽  
Author(s):  
Justin Gossard ◽  
Steven A. Waters ◽  
Shane Finneran
Keyword(s):  
High Speed ◽  
Laser Scanning ◽  
Field Experiments ◽  
Separation Distance ◽  
Primary Objective ◽  
Operating Conditions ◽  
Soil Conditions ◽  
Exterior Surface ◽  
High Speed Video ◽  
Test Segment

Construction blasting was proposed as a technique to create a trench for a new pipeline within the right-of-way (ROW) of an existing vintage pipeline where soil conditions consisted primarily of rock. Several field experiments were conducted to assess the potential loading conditions that the vintage pipeline could experience due to various blasting configurations as part of the nearby construction process. Two test pipe segments were constructed from segments removed from the vintage pipeline for use in these experiments. Each test segment contained two vintage bell-bell chill ring girth welds (GW) and were pressurized to operating conditions of the vintage pipeline for the duration of all blasting. Groups of eight resistive strain gages were bonded around the exterior surface of three distinct locations on each test segment. The three locations include one pipe body location and each of the two welds on each segment. Four separate experiments were conducted with each experiment focusing on a unique combination of trench backfill material, compaction level and separation distance from the test pipe segments and the explosive charges. The primary objective throughout these four experiments was to monitor and record the behavior of buried test pipe sections due to nearby blasting activities. Long range 3-dimentional (3D) laser scanning equipment was used to track movement of each test segment from test to test. High-speed video equipment was also employed to capture each blast. The high-speed video provided additional details on the blast energy transfer, verification of individual charge initiation as well as pipeline test segment movement where each pipeline segment was exposed. Peak particle velocity measurements were taken during each test blast. Strain data collected during each test was used to assess potential damage to the vintage pipeline test segments as a result of blasting. The combined information collected from the in-field testing showed that elevated strains and stresses may be observed during blasting activities near pipelines.

scholarly journals Research and Optimization of Surface Roughness in Milling of SLM Semi-Finished Parts Manufactured by Using the Different Laser Scanning Speed

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 9 ◽  
Author(s):  
Andrzej Matras
Keyword(s):  
Surface Roughness ◽  
Feed Rate ◽  
Laser Scanning ◽  
Cutting Tool ◽  
Scanning Speed ◽  
Milling Process ◽  
Face Milling ◽  
Machining Parameters ◽  
The Face ◽  
Laser Scanning Speed

The paper studies the potential to improve the surface roughness in parts manufactured in the Selective Laser Melting (SLM) process by using additional milling. The studied process was machining of samples made of the AlSi10Mg alloy powder. The simultaneous impacts of the laser scanning speed of the SLM process and the machining parameters of the milling process (such as the feed rate and milling width) on the surface roughness were analyzed. A mathematical model was created as a basis for optimizing the parameters of the studied processes and for selecting the sets of optimum solutions. As a result of the research, surface with low roughness (Ra = 0.14 μm, Rz = 1.1 μm) was obtained after the face milling. The performed milling allowed to reduce more than 20-fold the roughness of the SLM sample surfaces. The feed rate and the cutting width increase resulted in the surface roughness deterioration. Some milled surfaces were damaged by the chip adjoining to the rake face of the cutting tool back tooth.

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