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Technical Briefs

Laser Beam Welding of Open-Porous Metallic Foams for Application in Cooling Structures of Combined Cycle Power Plants

[+] Author and Article Information
Uwe Reisgen, Simon Olschok, Stefan Longerich

Welding and Joining Institute (ISF), RWTH Aachen University, Aachen NRW D-52062, Germany

J. Eng. Gas Turbines Power 132(5), 054502 (Mar 03, 2010) (5 pages) doi:10.1115/1.3204512 History: Received March 20, 2009; Revised April 27, 2009; Published March 03, 2010; Online March 03, 2010

Within the Collaborative Research Centre 561, “Thermally highly loaded, porous and cooled multilayer systems for combined cycle power plants,” open-porous and high-temperature stable Ni-based structures are being developed for the requirements of effusion cooling. A two-dimensional cooling strategy for the walls of combustion chambers, which allows the outflow of the cooling medium over the complete wall area of the combustion chamber, could be realized by an open-porous metallic foam structure. The open-porous metallic foam is produced by the “slip reaction foam sintering” process, a powder metallurgical process. To join several foams to assemble structural elements, laser beam welding has been used. Different joining strategies have been examined to find out the most suitable method to join these foams. In this paper, the process setups, settings of the different strategies, and results of trials (seam geometry and strength tests) are discussed. The need for graded structures to combine the essential permeability and adequate weldability is also shown.

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Copyright © 2010 by American Society of Mechanical Engineers
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Figures

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Figure 1

Schematic diagram of the multilayer cooling system of SFB 561 consisting of thermal barrier coating with bond coat, open-porous metallic foam, and substrate

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Figure 2

Scheme of the SRFS process (7)

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Figure 3

Process geometry for (a) welding variation 1 and (b) welding variation 2

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Figure 4

Specimen welded using variation 1: (a) macrosection and (b) top view

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Figure 5

Specimen welded using variation 1; t=15 mm, 8 mm fusion depth: (a) macrosection and (b) SEM analysis

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Figure 6

(a) Macrosection of a specimen welded with variation 2. (b) Cavity formation through excessive energy input into the foam

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Figure 7

(a) Setup concept for the determination of the shear strength. (b) Specimen loading from underneath. (c) Specimen loading from the upper side.

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Figure 8

(a) Results of the tensile shear tests of the specimens welded with strategy 1. (b) Results of the tensile shear tests of the specimens welded with strategy 2.

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Figure 9

Typical rupture of the foam, bottom view

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