27 Superalloy Case Study

27 Superalloy Case Study - 530.352 Materials Selection...

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530.352 Materials Selection Lecture #27: Superalloy Case Study Wednesday Nov 16 th , 2005
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The Boeing 777 Powered by two GE 90’s
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777’s are powered by 2 GE90’s:
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Low Pressure Turbine High Pressure Turbine Combustor High Pressure Compressor Low Pressure Compressor or Booster Fan Fan Air Core Air GE 90 Jet Engine :
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Efficiency of a heat engine 1 2 1 T T T Efficiency -
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Three ways to increase efficiency: TBC
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Improvements in superalloy creep strength:
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Improvements in creep strength: Alloy development based on fundamental understanding of creep applied empirically. Form stable precipitates (Ni 3 Al, Ni 3 Ti, M 23 C 6 , MoC, TaC) Have as many heavy atoms in solid solution as possible (Hf, W, Co, Cr, Ta, etc.) Form a protective oxide surface (Cr 2 O 3 or Al 2 O 3 )
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Improvements in creep strength: 10 μ m 1 μ m
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Solution Heat Treatment Aging Treatment Temperature Time T solvus Secondary γ ´ Tertiary γ ´ Primary γ ´ • Supersolvus heat treatment (no “primary” γ ’) • Secondary γ ’ develops upon cooling from supersolvus temperature • Tertiary γ ’ forms upon cooling and subsequent aging Microstructure development: Ref. Mills et al
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Superalloy developments:
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Improvements in creep strength:
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Changing grain size to mitigate creep: Equiaxed Directional solidification
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    Single crystal  Single crystal  turbine blade turbine blade Making single-crystalline turbine blades:
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Investment casting: http://www.alcoa.com/howmet/en/info_page/inv_cast.asp#
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Section of a blade with cooling channels:
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Internal cooling channels: casting:
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“TBCs are ‘bill-of-materials’ in many GEAE product lines: turbine blades, vanes, combustors. Designers love it, and want more. Engine run without TBC Engine run with TBC (150ºF reduction) Ref. Ram Darolia, GE Aircraft Engines Industrial perspective on the use of TBC’s:
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Strengthening of Gamma TiAl: Pros and Cons Curt Austin and Jim Williams TMS Annual Meeting San Antonio, TX 2/17/98 Aircraft Engines γ
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This note was uploaded on 04/08/2008 for the course MECHENG 352 taught by Professor Hemker during the Spring '08 term at Johns Hopkins.

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27 Superalloy Case Study - 530.352 Materials Selection...

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