scholarly journals In-Situ Laser Polishing Additive Manufactured AlSi10Mg: Effect of Laser Polishing Strategy on Surface Morphology, Roughness and Microhardness

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 393
Author(s):  
Jiantao Zhou ◽  
Xu Han ◽  
Hui Li ◽  
Sheng Liu ◽  
Shengnan Shen ◽  
...  
Keyword(s):  
Surface Quality ◽  
Molten Pool ◽  
Surface Defects ◽  
Polished Surface ◽  
Transient Model ◽  
Surface Evolution ◽  
Powder Bed ◽  
Laser Polishing ◽  
Surface Morphologies

Laser polishing is a widely used technology to improve the surface quality of the products. However, the investigation on the physical mechanism is still lacking. In this paper, the established numerical transient model reveals the rough surface evolution mechanism during laser polishing. Mass transfer driven by Marangoni force, surface tension and gravity appears in the laser-induced molten pool so that the polished surface topography tends to be smoother. The AlSi10Mg samples fabricated by laser-based powder bed fusion were polished at different laser hatching spaces, passes and directions to gain insight into the variation of the surface morphologies, roughness and microhardness in this paper. The experimental results show that after laser polishing, the surface roughness of Ra and Sa of the upper surface can be reduced from 12.5 μm to 3.7 μm and from to 29.3 μm to 8.4 μm, respectively, due to sufficient wetting in the molten pool. The microhardness of the upper surface can be elevated from 112.3 HV to 176.9 HV under the combined influence of the grain refinement, elements distribution change and surface defects elimination. Better surface quality can be gained by decreasing the hatching space, increasing polishing pass or choosing apposite laser direction.

scholarly journals Numerical Simulation of Effect of Different Initial Morphologies on Melt Hydrodynamics in Laser Polishing of Ti6Al4V

Micromachines ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 581
Author(s):  
Kai Li ◽  
Zhenyu Zhao ◽  
Houming Zhou ◽  
Hao Zhou ◽  
Jie Yin ◽  
...  
Keyword(s):  
Flow Behavior ◽  
Processing Parameters ◽  
Surface Finishing ◽  
Polished Surface ◽  
Laser Polishing ◽  
Starting Position ◽  
Double Spiral ◽  
The Difference ◽  
Thermocapillary Forces ◽  
Surface Morphologies

As a surface finishing technique for rapid remelting and re-solidification, laser polishing can effectively eliminate the asperities so as to approach the feature size. Nevertheless, the polished surface quality is significantly sensitive to the processing parameters, especially with respect to melt hydrodynamics. In this paper, a transient two-dimensional model was developed to demonstrate the molten flow behavior for different surface morphologies of the Ti6Al4V alloy. It is illustrated that the complex evolution of the melt hydrodynamics involving heat conduction, thermal convection, thermal radiation, melting and solidification during laser polishing. Results show that the uniformity of the distribution of surface peaks and valleys can improve the molten flow stability and obtain better smoothing effect. The high cooling rate of the molten pool resulting in a shortening of the molten lifetime, which prevents the peaks from being removed by capillary and thermocapillary forces. It is revealed that the mechanism of secondary roughness formation on polished surface. Moreover, the double spiral nest Marangoni convection extrudes the molten to the outsides. It results in the formation of expansion and depression, corresponding to nearby the starting position and at the edges of the polished surface. It is further found that the difference between the simulation and experimental depression depths is only about 2 μm. Correspondingly, the errors are approximately 8.3%, 14.3% and 13.3%, corresponding to Models 1, 2 and 3, respectively. The aforementioned results illustrated that the predicted surface profiles agree reasonably well with the experimentally measured surface height data.

Numerical Analysis of Effect of Different Initial Morphologies on Molten Pool Flows

2020 ◽  
Vol 861 ◽  
pp. 491-498
Author(s):  
Kai Li ◽  
Zhen Yu Zhao ◽  
Hou Ming Zhou ◽  
Hao Zhou ◽  
Jing Cheng Jin
Keyword(s):  
Heat Transfer ◽  
Flow Velocity ◽  
Molten Pool ◽  
Flow Characteristics ◽  
Polished Surface ◽  
Initial Shape ◽  
Factors Affecting ◽  
Smooth Plane ◽  
Surface Morphologies

The different initial morphologies of polished surface is one of the important factors affecting the quality of laser polishing. In order to investigate the flow characteristics of the molten pool with different morphologies, a two-dimensional (2D) axisymmetric numerical model is established based on the COMSOL software. The nonisothermal flow interface is used to couple the heat transfer and fluid flow, and simulate the evolution process of the molten pool with three different surface morphologies. The results show that the initial shape is a smooth plane, the flow velocity of the molten pool is stable and always in thermocapillary regime, then the protrusions were generated at the edge of the molten pool. Likewise, with the increase of the surface curvature, the capillary becomes the main driving force to eliminate the surface asperities. While the flow velocity and instability of the molten pool enhance, and the depth of the molten pool increases with the heat transfer generated by the mass flow along the z-axis direction.

scholarly journals Laser Polishing of Laser Powder Bed Fusion AlSi10Mg Parts—Influence of Initial Surface Roughness on Achievable Surface Quality

2021 ◽  
Vol 12 (01) ◽  
pp. 15-41
Author(s):  
Markus Hofele ◽  
Andre Roth ◽  
Jochen Schanz ◽  
David K. Harrison ◽  
Anjali K. M. De Silva ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Surface Quality ◽  
Initial Surface ◽  
Powder Bed Fusion ◽  
Laser Powder Bed Fusion ◽  
Powder Bed ◽  
Laser Polishing

Numerical Simulation of the Influence of Different Surface Morphologies on Molten Pool Flow under Moving Heat Source

2021 ◽  
Vol 904 ◽  
pp. 9-13
Author(s):  
Jie Yin ◽  
Zhen Yu Zhao ◽  
Hou Ming Zhou ◽  
Kai Li ◽  
Hao Zhou
Keyword(s):  
Heat Source ◽  
Surface Topography ◽  
Capillary Force ◽  
Molten Pool ◽  
Moving Heat Source ◽  
Element Analysis ◽  
Thermocapillary Force ◽  
Initial Shape ◽  
Transient Model ◽  
Laser Polishing

In order to study the influence of different initial topography on the molten pool flow under a moving heat source, the finite element analysis method was used to establish a two-dimensional transient model of laser polishing to simulate the evolution of the surface topography of the material during laser polishing. In the simulation process, a moving laser beam was used as the heat source, and the free surface of the actual material was profiled through a three-dimensional profiler. A very similar simulation model surface was constructed, coupled with the flow field and temperature field in the laser polishing process, and the capillary force was considered comprehensively. Combined with thermocapillary force. The results show that under the combined action of capillary force and thermocapillary force, the surface of the polished material has a peak-filling effect, which makes the surface of the material achieve a good polishing effect. The initial shape will affect the polishing effect, the greater the curvature, the faster the flow rate of the molten pool. In molten pools with large spatial curvatures, capillary forces dominate. Keywords: Laser polishing; molten pool; surface topography; numerical analysis; capillary force; thermocapillary force.

scholarly journals Numerical Simulation and Verification of Laser-Polishing Free Surface of S136D Die Steel

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 400
Author(s):  
Hao Zhou ◽  
Houming Zhou ◽  
Zhenyu Zhao ◽  
Kai Li ◽  
Jie Yin
Keyword(s):  
Numerical Simulation ◽  
Surface Morphology ◽  
Molten Pool ◽  
Orthogonal Experiment ◽  
Material Surface ◽  
Beam Radiation ◽  
Transient Model ◽  
Laser Polishing ◽  
Die Steel ◽  
Pool Depth

As a novel polishing technology, polishing by laser beam radiation can be used to improve the sample surface finish without causing material losses. In order to study the effect of laser polishing on the surface morphology of S136D die steel, an L16(44) orthogonal experiment was designed to describe the variation trend of surface roughness with energy density. The two-dimensional transient model of laser polishing was established to simulate the evolution process of material surface morphology during laser polishing by combining numerical simulation with the experiment. The model uses a moving laser heat source to study the effects of capillary pressure and thermocapillary pressure in the laser polishing process. The experimental results show that the minimum roughness can be reduced to 0.764 μm, and the error between the actual molten pool depth and the simulated molten pool depth is 5.3%.

scholarly journals Improvement of polymer properties for powder bed fusion by combining in situ PECVD nanoparticle synthesis and dry coating

2021 ◽  
Author(s):  
Juan S. Gómez Bonilla ◽  
Björn Düsenberg ◽  
Franz Lanyi ◽  
Patrik Schmuki ◽  
Dirk W. Schubert ◽  
...  
Keyword(s):  
Nanoparticle Synthesis ◽  
Powder Bed Fusion ◽  
Dry Coating ◽  
Powder Bed ◽  
Polymer Properties

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.

Towards process consistency and in-situ evaluation of porosity during laser powder bed additive manufacturing

2020 ◽  
Vol 25 (8) ◽  
pp. 679-689
Author(s):  
J. Raplee ◽  
J. Gockel ◽  
F. List ◽  
K. Carver ◽  
S. Foster ◽  
...  
Keyword(s):  
Additive Manufacturing ◽  
Powder Bed
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