scholarly journals High power selective laser melting of crack sensitive nickel-base alloy CM247LC, including dimensional analysis and modelling

2021 ◽  
Author(s):  
Marcel Gerstgrasser ◽  
Michael Cloots ◽  
Raphael Jakob ◽  
Josef Stirnimann ◽  
Konrad Wegener
Keyword(s):  
High Power ◽  
Laser Power ◽  
Crack Density ◽  
Spot Size ◽  
Laser Spot ◽  
Beam Diameter ◽  
Crack Healing ◽  
Laser Spot Size ◽  
Pool Depth ◽  
Melt Pool

Abstract Compared to reference parameters in the low power and scan velocity range, which lead to dense and crack-free CM247LC LPBF samples due to in-situ crack healing, high power, high scan velocities and increased laser beam diameters are investigated, to decrease the production time further. By keeping the maximum laser intensity from the reference and the laser power to scan velocity ratio constant, the intensity approach provides an initial estimation for the laser spot size regarding the measured Archimedean density and crack density in the high power and high scan velocity range. The investigated cracks are identified as re-melting cracks. Solidification or hot cracks are not observed, since the crack healing effect for those kinds of cracks still occurs. Furthermore, a melt pool depth range is discovered, where not only solidification cracks can be avoided, but also re-melting cracks, which are resulting from higher laser power inputs. This theory can be proven by further laser spot size optimization, where the melt pool depth comes closer to the mentioned range. The Archimedean density and crack density results, in case of the 600 W power parameter with 2400 mm/s scan velocity and a beam diameter of 164 µm, are close to the one obtained from the reference with 200 W, a scan velocity of 800 mm/s and a laser spot of 90 µm. With the intensity approach and laser beam diameter optimization, the production time can be reduced by 300%. Based on dimensional analysis, a model, which combines the samples density with the crack density through the melt pool depth, is presented. Six main and two additional process and laser parameters are taken into relation. The result from the model and the measured values from experiments are in good agreement. Additionally, the influence of the doubled layer thickness and an increased hatch distance by 50% with varying scan velocities on the Archimedean density and crack density is analysed.

Microstructure of Laser Treated ZE41A-T5 Magnesium Alloy

2010 ◽  
Vol 654-656 ◽  
pp. 759-762 ◽  
Author(s):  
Y. Durandet ◽  
S. Sun ◽  
M. Brandt
Keyword(s):  
Magnesium Alloy ◽  
Laser Power ◽  
Chemical Elements ◽  
Spot Size ◽  
Laser Spot ◽  
Thermal Shrinkage ◽  
Laser Spot Size ◽  
Melt Pool ◽  
Scan Rate ◽  
Melting And Solidification

Modification of the microstructure of ZE41A-T5 magnesium alloy substrates was investigated by laser surface re-melting and solidification using a 2.5 kW Nd:YAG laser. The effects of laser power, high scan rate and beam configuration were examined. The microstructure of laser treated ZE41 consisted of small precipitates dispersed in a fine dendritic α-magnesium matrix at high scan rates. The redistribution of chemical elements depended mainly on the dwell time in the liquid stage. At high scan rates, long dwell times were achieved by splitting the laser beam into two spots trailing in the scan direction which resulted in a more homogenous distribution of Mg, Zn and Zr. Cracking due to thermal shrinkage during solidification was prevented by reducing the temperature of the melt pool. This was achieved by lowering the laser power, increasing the scan rate and laser spot size. Increasing the laser spot size in the scan direction was conducive to producing homogeneous microstructures without cracks.

Laser spot size and laser power dependence of ion formation in high resolution MALDI imaging

2010 ◽  
Vol 294 (1) ◽  
pp. 7-15 ◽  
Author(s):  
Sabine Guenther ◽  
Martin Koestler ◽  
Oliver Schulz ◽  
Bernhard Spengler
Keyword(s):  
High Resolution ◽  
Laser Power ◽  
Spot Size ◽  
Laser Spot ◽  
Maldi Imaging ◽  
Power Dependence ◽  
Laser Spot Size ◽  
Ion Formation

The Effect of Optical Design on Micromanipulator Spot Size Using CO2 Laser Irradiation

2002 ◽  
Vol 126 (6) ◽  
pp. 593-597 ◽  
Author(s):  
Kenneth K. H. Chao ◽  
Eric Cheung ◽  
William B. Armstrong ◽  
Brian J. F. Wong
Keyword(s):  
Laser Irradiation ◽  
Laser Power ◽  
Focal Length ◽  
Optical Design ◽  
Spot Size ◽  
Laser Spot ◽  
Photographic Film ◽  
Laser Spot Size ◽  
Incremental Change ◽  
Reflective Design

OBJECTIVE: The study goal was to compare the laser spot size created using reflective and refractive micromanipulators with a CO2 laser and to determine the sensitivity of spot size to laser power. STUDY DESIGN AND SETTING: A CO2 laser and operating microscope (400-mm focal length) was coupled to either a reflective (Cassegrain-like) or refractive micromanipulator. Laser spot size was determined by measuring the region of ablation created by laser irradiation of wood (dry tongue depressors), exposed photographic film, and agar gel using optical micrometry. Laser power varied from 0.5 to 20 W with pulse durations of 0.1 and 0.5 second. RESULTS: The reflective micromanipulator demonstrated overall smaller spot sizes for a given laser power and lower incremental change in spot size with increasing power. The reflective design demonstrated less sensitivity to increases in laser power. CONCLUSIONS: Micromanipulator optical design can result in significant differences in laser spot size. The reflective device used in this study demonstrated less sensitivity to increasing laser power.

Modelling of the laser spot size dependence of retinal thermal damage

2005 ◽  
Author(s):  
Karl Schulmeister ◽  
Bernhard Seiser ◽  
Florian Edthofer ◽  
David J. Lund
Keyword(s):  
Size Dependence ◽  
Thermal Damage ◽  
Spot Size ◽  
Laser Spot ◽  
Laser Spot Size

scholarly journals Long lifetime of bialkali photocathodes operating in high gradient superconducting radio frequency gun

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
E. Wang ◽  
V. N. Litvinenko ◽  
I. Pinayev ◽  
M. Gaowei ◽  
J. Skaritka ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Electron Beams ◽  
Spot Size ◽  
Laser Spot ◽  
Laser Spot Size ◽  
High Quantum Efficiency ◽  
High Brightness ◽  
High Charge ◽  
Superconducting Radio Frequency ◽  
Long Lifetime

AbstractHigh brightness, high charge electron beams are critical for a number of advanced accelerator applications. The initial emittance of the electron beam, which is determined by the mean transverse energy (MTE) and laser spot size, is one of the most important parameters determining the beam quality. The bialkali photocathodes illuminated by a visible laser have the advantages of high quantum efficiency (QE) and low MTE. Furthermore, Superconducting Radio Frequency (SRF) guns can operate in the continuous wave (CW) mode at high accelerating gradients, e.g. with significant reduction of the laser spot size at the photocathode. Combining the bialkali photocathode with the SRF gun enables generation of high charge, high brightness, and possibly high average current electron beams. However, integrating the high QE semiconductor photocathode into the SRF guns has been challenging. In this article, we report on the development of bialkali photocathodes for successful operation in the SRF gun with months-long lifetime while delivering CW beams with nano-coulomb charge per bunch. This achievement opens a new era for high charge, high brightness CW electron beams.

Laser spot size and scaling laws for laser beam additive manufacturing

2022 ◽  
Vol 73 ◽  
pp. 26-39
Author(s):  
Jordan S. Weaver ◽  
Jarred C. Heigel ◽  
Brandon M. Lane
Keyword(s):  
Additive Manufacturing ◽  
Laser Beam ◽  
Scaling Laws ◽  
Spot Size ◽  
Laser Spot ◽  
Laser Spot Size

Computer Simulation of Laser Induced Temperatures for the Laser Direct Writing technique

1987 ◽  
Vol 101 ◽  
Author(s):  
Didier Tonneau ◽  
Geoffroy Auvert
Keyword(s):  
Laser Power ◽  
Quartz Substrate ◽  
Equilibrium Temperature ◽  
Spot Size ◽  
Heat Diffusion ◽  
Laser Spot ◽  
Maximum Temperature ◽  
Substrate Thickness ◽  
Direct Writing ◽  
Gaussian Laser Beam

ABSTRACTLaser induced temperatures in substrates irradiated with a scanning gaussian laser beam were calculated by the finite element method. A quartz substrate of a given thickness and covered with a one - micron - thick silicon coating was assumed to be either placed on a heat sink or thermally insulated. The maximum temperature in the center of the laser spot was found to be proportional to the laser power for a spot size larger than the silicon thickness. Furthermore at a given laser power, the temperature decreased with increasing laser spot diameter and the time to reach the equilibrium temperature increases with the spot radius for radii less than the substrate thickness. The laser induced temperature was found to be affected by laser - scan speeds for speed values above the heat diffusion rate.

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