Characterization of microstructural effects in a percussion laser-drilled powder metallurgy Ni-based superalloy
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In the combustion zone of gas turbine engines for aircraft, it is essential to maintain a large temperature differential between the combustion gases and the Ni superalloy components so that fuel is used efficiently while avoiding degradation of the turbine blades, rotors, casings, etc. This is typically achieved using a combination of thermal barrier coatings (TBCs) and cooling holes [1, 2, 3]. In the latter case, air from the compressor section is forced through internal channels in the components and this emerges from arrays of fine (<500 μm in diameter) cooling holes, establishing a thin air layer between the combustion gases and the TBC. Current generation engines can contain in excess of 106 cooling holes and most of these are produced by electro-discharge machining (EDM) or laser drilling. The use of laser drilling is increasing because it enables holes to be drilled through components with TBCs (e.g. [4, 5]); this is a significant advantage over EDM where the holes must be...
KeywordsBase Metal Laser Welding Recast Layer Laser Drilling Transmission Electron Microscopy Foil
The authors would like to thank Robin Bright (University of Connecticut) and Dr. Paul Denney of the Connecticut Center for Advanced Technology (CCAT) for helpful discussions, Robert Wright of CCAT for assistance with producing the laser-drilled samples, and Pal O. Pedersen of FEI Company and Dr. Kai Song of Lehigh University for assistance with FIB sectioning. This material is based on research sponsored by CCAT’s National Center for Aerospace Leadership through Grant/Cooperative Agreement Number FA9550-06-1-0397 with the Air Force Office of Scientific Research. The U.S. government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright notation thereon. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the Air Force Research Laboratory or the U.S. government.
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