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High-Purity Chromium Metal Supply Issues for Gas-Turbine Superalloys (1995) / Chapter Skim
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2 SPECIFICATIONS FOR HIGH-PURITY CHROMIUM METAL
Pages 19-28

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From page 19...
... Additional applications include ship propulsion, natural gas transmission, and electrical power generation. Aircraft engines are well known for their rapid evolution while maintaining a high degree of reliability.
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From page 20...
... 20 IliBh Punly a~rorru~ AIctal: Supply Issues for Gas-Turbine Superalloys I:: ._ of a 3 a: ._ o :` u, 4)
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From page 21...
... Limiting Property Fan/Drum Rotor Compressor Blade Combustor Outer Air Seal Turbine Vane Turbine Blade Turbine Disc Shaft Bearings Case 50 600 1100 1250 1200 1100 600 250 250 600 Ti or Al Ti or Ni Ni or Co ZrO2 Co or Ni Ni Ni Fe Fe Ni Foreign object damage, low-cycle fatigue High-frequency fatigue Melting, oxidation Melting, erosion Melting, oxidation Creep, thermal mechanical fatigue, low-cycle fatigue, high-frequency fatigue, oxidation, hot corrosion Low~ycle fatigue Stiffness Wear resistance Toughness, thermal mechanical fatigue
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From page 22...
... These materials are dependent on very low impurity levels in order to avoid incipient melting, fatigue crack initiation at oxides, and oxide spallation in the cyclic temperature environment of engine operation. Second, inclusions are one of the limiting microstructural features for ductility, fatigue life, or creep-rupture.
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From page 23...
... Specifications for High-Purity Chromium Metal 23 Shallow Surface Dross FIGURE 2-2 Photomicrographs depicting deep lacy and shallow surface dross. Reprinted courtesy of Pratt & Whitney.
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From page 24...
... The original equipment manufacturers and the primaryalloy producers have determined stringent specifications for each major additive, with the minimum and maximum values allowed for each intentional alloying element and a maximum for each (known) undesirable impurity.
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From page 25...
... . 25 FIGURE 2-3 Photomicrographs of jet engine turbine blade showing intergranular stress-rupture cracks.
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From page 26...
... 26 High-Purity Chronuum Metal: Supply Issues for Gas-Turbirze Superalloys u, 3 .= 3 .D ~ m 0)
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From page 27...
... of the aerospace-grade chromium metal domestically consumed. While alum~nothermic material of equivalent quality to the electrolytic material may now be available, changes in such critical applications must be mutually acceptable to producer and user and would require extensive qualification studies involving production and testing of alloys, test specimens, final cast and forged products, and possibly engines containing them.
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Key Terms

  • aircraft engine
  • future demand
  • aircraft engines
  • limiting properties
  • exposure temperatures

  • specified materials
  • engine operation
  • mechanical fatigue
  • engine builders
  • thermal mechanical

  • incipient melting
  • drum rotors
  • metal plays
  • electrolytically produced
  • undesirable impurity

  • rotating blades
  • metal based
  • aerospace industry
  • starting materials
  • rapidly expanding

  • metric tons
  • component failures
  • equipment manufacturers
  • grain boundaries
  • blades attached

  • intentional alloying
  • extensive qualification
  • modest decline
  • generate significant
  • thrust reversers


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