Scanning Laser Epitaxy (SLE) is a layer-by-layer additive manufacturing process that allows for the fabrication of three-dimensional objects with specified microstructure through the controlled melting and re-solidification of a metal powders placed atop a base substrate. SLE can be used to repair single crystal (SX) turbine airfoils, for example, as well as the manufacture functionally graded turbine components. The SLE process is capable of creating equiaxed, directionally solidified, and SX structures. Real-time feedback control schemes based upon an offline model can be used both to create specified defect free microstructures and to improve the repeatability of the process. Control schemes can be used based upon temperature data feedback provided at high frame rate by a thermal imaging camera as well as a melt-pool viewing video microscope. A real-time control scheme can deliver the capability of creating engine ready net shape turbine components from raw powder material.

Systems and methods for additive manufacturing and repair of metal components

A comparative study on welding temperature fields, residual stress distributions and deformations induced by laser beam welding and CO2 gas arc welding

Numerical simulation of full penetration laser welding of thick steel plate with high power high brightness laser

A study on laser beam oscillating welding characteristics for the 5083 aluminum alloy: Morphology, microstructure and mechanical properties

Experimental and numerical investigations of welding distortion induced by CO2 gas arc welding in thin-plate bead-on joints

Thick-section stainless steels are widely used in the components and structures for nuclear power plants. Laser welding is being considered as a high-efficiency method instead of arc welding for some components, so as to improve the production efficiency and reduce the residual stresses of the heat-affected zone. In this paper, multipasses narrow-gap welding of 50 mm thick Type 316L plates with an 8 kW disk laser was first investigated. The effect of welding conditions on the weld bead geometry and welding defects was studied. It shows that lack of fusion could be prevented by optimizing the relationship between laser power intensity and the deposited metal volume. Butt joint of 50 mm thick plates with narrow gap could be performed with eight-layers welding at laser power of 6 kW and welding speed of 0.4 m/min. In order to reduce the weld passes further, gas jet assisted laser welding was tried to weld thick Type 316L plates with a 10 kW fiber laser. The result shows that butt-joint welding of 40 mm plates without filler wire could be carried out at 0.3 m/min welding speed with no porosity or other welding defects. As for 50 mm thick plate, a good weld bead could be obtained with bead-on-plate welding from both sides at 0.2 m/min welding speed.

Welding of thick stainless steel plates up to 50 mm with high brightness lasers

Investigation on twisting distortion of thin plate stiffened structure under welding

Investigation of laser welding phenomena of pure copper by x-ray observation system

Surface void suppression for pure copper by high-speed laser scanner welding

A laser welding method whereby an object being welded is bombarded by a laser and another heat source, wherein the object being welded is bombarded by the laser and the other heat source in a manner such that at least a portion of the weld pool formed by the laser bombardment and the weld pool formed by the other heat source overlap each other, and the object being welded is constantly bombarded by the laser at an area in front of the center of bombardment of the other heat source, in the direction in which the welding progresses

Zhang Xudong

Papers

Welding of thick stainless steel plates up to 50 mm with high brightness lasers

Investigation on twisting distortion of thin plate stiffened structure under welding

Investigation of laser welding phenomena of pure copper by x-ray observation system

Surface void suppression for pure copper by high-speed laser scanner welding

Laser welding method