JLA Vol:19 Iss:2 (Welding of titanium and other refractory metals with a free pulse shaping laser)

Authors:
Karsten Richter
Lasag AG, Switzerland

Uwe Reisgen
Wilfried Behr
Forschungszentrum Ju¨lich GmbH, Germany

Ronald Holtz
Lasag AG, Switzerland

Refractory metals are used as construction materials for specific applications. Amongst the refractory metals, titanium has a special status due to its multi-faceted property profile and its comparatively low price. Titanium materials have outstanding properties, such as excellent resistance to corrosion and very high strength at low densities, which lead to their preferred use in chemical engineering and as a structural material in lightweight construction. Due to the high affin...

JLA Vol:23 Iss:1 (Review of laser microscale processing of silicon carbide)

Authors:
B. Pecholt
S. Gupta
P. Molian
Department of Mechanical Engineering, Laboratory for Lasers, MEMS and Nanotechnology, Iowa State University, Ames, Iowa 50011

A review of various laser techniques for microscale processing of SiC for microelectronics and microelectromechanical-system applications is presented. SiC is an excellent material for harsh environments due to its outstanding mechanical, thermal, and chemical properties. However, its extreme thermodynamic stability and inert properties created difficulties in conventional microfabrication methods which provided an opportunity for the exploration of laser processing as an alternative. Many aspects...

JLA Vol:7 Iss:3 (Characterization of chromium bearing surface alloys produced by laser alloying on low carbon steel substrates)

Authors:
G. L. Goswami
Dilip Kumar
A. L. Pappachan
A. K. Grover
K. Sridhar
Array

High‐chromium ferritic alloys were produced on mild steel substrates by laser surface alloying. For this, chromium‐plated mild steel samples were treated with a pulsed Nd:YAG laser (300 W maximum power) by varying the average power level from 21.6 W to 30.0 W. The chromium content of the surface alloys was in the range of 3.0–27.0 wt%, with fairly uniform depth of alloying. Microscopy showed very fine austenite needles within elongated/equiaxed ferrite grains in the laser‐alloyed zone (LAZ). X‐ray diffraction indi...

JLA Vol:1 Iss:2 (Summary of Laser Plume Effects and Safety Session)

Authors:
Richard P. Felten
Senior Chemist, Radiation Biology Branch, Center for Devices and Radiological Health, Food and Drug Administration

JLA Vol:17 Iss:4 (Faster and damage-reduced laser cutting of thick ceramics using a simultaneous prescore approach)

Authors:
V. Pereles-Santiago
M. Washington
P. Brugan
G. Cai
R. Akarapu
S. Pulford
A. E. Segall
The Pennsylvania State University, University Park, Pennsylvania 16802

Laser machining of structural ceramics is increasingly gaining acceptance as an alternative to traditional machining methods. However, despite the great promise of lasers for a variety of cutting and drilling procedures, premature fractures and prohibitively low cutting speeds are still among the greatest obstacles encountered, particularly when thick cross sections are involved. While many factors contribute to the fractures encountered during ...

JLA Vol:22 Iss:2 (Keyhole behavior in deep penetration CO₂ laser welding)

Authors:
Hiroshi Honda
Susumu Tsukamoto
Isao Kawaguchi
Goro Arakane
Structural Metals Center, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan

A slender keyhole formed by deep penetration laser welding fluctuates violently and is apt to form porosity. To reveal the keyhole depth behavior, the authors observed the keyhole images simultaneously by using a microfocus x-ray transmission imaging system and plasma plume images in deep penetration CO₂ laser welding at various welding speeds. Plasma light emission was also measured by using photodiodes. The upper part of the keyhole was found to fluctuat...

JLA Vol:9 Iss:6 (Scaling laws for thick‐section cutting with a chemical oxygen–iodine laser)

Authors:
A. Kar
J. A. Rothenflue
W. P. Latham

Almost all laser‐assisted materials processing involves melting, vaporization and plasma formation which affect the utilization of laser energy for materials processing. To account for the effect of these phases, an effective absorptivity is defined, and a simple mathematical model is developed for the cutting of thick‐section stainless steel using a high power chemical oxygen—iodine laser (COIL). The model is based on an overall energy balance, and it relates the cutting depth with various process parameters that can be used to predictively scale the laser materials processing performance to ...

JLA Vol:3 Iss:3 (Safety of Medical Excimer Lasers with an Emphasis on Compressed Gases)

Authors:
David H. Sliney
Laser Microwave Division, US Army Environmental Hygiene Agency, Aberdeen Proving Ground, MD 21010‐5422

Terrance N. Clapham
VISX, Inc., 919 Kifer Road, Santa Clara, CA 94086

Excimer lasers which emit short ultraviolet radiation (UVR) are currently being used in experimental and developmental surgical applications. Although UVR exposure is possible, it is not normal in laser angioplasty (cardiovascular surgery) and is insignificant in photokera‐toplasty (ophthalmic surgery). However, significant potential hazards exist with the use of excimer laser gases such as fluorine and HCI. Stringent safeguards for handling and use are ...

JLA Vol:15 Iss:4 (Laser–material interaction and process sensing in underwater Nd:yttrium–aluminum–garnet laser welding)

Authors:
Xudong Zhang
Wuzhu Chen
Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China

Eiji Ashida
Fukuhisa Matsuda
Tarasaki R&D Center, JAPEIC, Hitachinaka, Ibaraki 312-0003, Japan

Laser–material interaction and process sensing technology for local-dry underwater Nd:yttrium–aluminum–garnet laser beam welding were studied. The optical emissions induced by laser–water interaction were detected with an infrared (IR) optical sensor and observed with a charge coupled device camera. It was found that under laser irradiation, a kind of water–vapor plasma formed immediately above the ...

JLA Vol:20 Iss:1 (Practical and theoretical investigations into inert gas cutting of 304 stainless steel using a high brightness fiber laser)

Authors:
Martin Sparkes
Markus Gross
Steven Celotto
Tao Zhang
William O’Neill
Centre for Industrial Photonics, Institute for Manufacturing, Department of Engineering, University of Cambridge, Cambridge, CB2 1RX, United Kingdom

A 2.2 kW fiber laser was used in a series of inert cutting trials on stainless steels of section thicknesses in the range of 6–10 mm. Variations in the cutting performance with changing gas pressure, focal position, and nozzle diameter were investigated. Results showed the difficulties associated in cutting with high brightness lasers, specifically in obtaining full melt eject through narr...