Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt
  • C22C38/105—Ferrous alloys, e.g. steel alloys containing cobalt containing Co and Ni
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C19/00—Alloys based on nickel or cobalt
  • C22C19/03—Alloys based on nickel or cobalt based on nickel
  • C22C19/05—Alloys based on nickel or cobalt based on nickel with chromium
  • C22C19/058—Alloys based on nickel or cobalt based on nickel with chromium without Mo and W
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C30/00—Alloys containing less than 50% by weight of each constituent

Definitions

• This invention relates to the field of controlled expansion superalloys.
• this invention relates to controlled thermal expansion nickel-iron-cobalt superalloys.
• CTE coefficients of thermal expansion
• SAGBO stress accelerated grain boundary oxidation
• INCOLOY alloy 905 containing only 0 to 3 wt% cobalt, represents the commercial product of the '459 patent. (INCOLOY is a trademark of the Inco group of companies.) But due to its prolonged heat treating requirements, INCOLOY alloy 905 lacks cost effectiveness for turbine engine applications. For example, INCOLOY alloy 905 typically requires aging times in excess of 300 hours to ensure adequate impact strength. Because of these painfully slow aging procedures, INCOLOY alloys 907 and 909, that contain cobalt for accelerating aging kinetics, quickly replaced INCOLOY alloy 905.
• U.S. Patent No. 5,283,032 discloses a cobalt-chromium modified low CTE alloy.
• a commercially available embodiment of this patent nominally contains: 29 wt% cobalt, 25 wt% nickel, 5.5 wt% chromium, 4.8 wt% niobium, 0.8 wt% titanium, 0.5 wt% aluminum, 0.3 wt% silicon and balance iron ('032 alloy).
• Alloy 783 provides a low-CTE superalloy having good general oxidation resistance, excellent crack growth resistance, good strength and decreased density. With a nominal cobalt concentration of 34 wt% however, alloy 783 is also a relatively expensive alloy.
• the alloy of the invention provides a controlled-coefficient of thermal expansion alloy that age hardens.
• This alloy consists essentially of, by weight percent, about 32 to 55 nickel, about 6 to 16 cobalt, about 1.2 to 7 chromium, about 0.25 to 1.5 aluminum, about 0.25 to 3 titanium, about 2 to 8 total (niobium + 1 ⁇ 2 tantalum), about 0.1 to 1.2 silicon and balance iron and incidental impurities with iron being about 28 to 50.
• the ingots of Table 1 were vacuum induction melted (VIM) and cast as 4" (10.2 cm) diameter, 22 kg ingots. (This specification contains compositions expressed in weight percentage, unless specifically noted otherwise.)
• the following heat treatment prepared the samples of heats 1 to 6: 1) 1825°F (996°C) for 1 hour of annealing; 2) air cooled to room temperature; 3) aged at 1375°F (746°C) for 8 hours; 4) furnace cooled to 1150°F (621°C); 5) held at 1150°F (621°C) for 8 hours of secondary aging; and 6) air cooled to room temperature.
• Table 2 provides inflection temperatures and coefficients of thermal expansion for the heat treated samples of heats 1 to 6 below.
• All of the alloys of Table 2 had a coefficient of thermal expansion of less than 13.6 x10 -6 cm/cm/°C at 371°C. Most advantageously, the alloys have a coefficient of thermal expansion of less than 10 x10 -6 cm/cm/°C at 371°C.
• Heats 1 to 3 and 6 provided properties similar to '032 alloy's published specification of 580-640 °F (304-338°C) inflection temperature and a CTE of 4.25 to 4.75 x10 -6 in/in/°F at temperatures between 400 and 600°F (7.65 to 8.55 x10 -6 cm/cm°C between 204 and 316°C). These alloys however, achieve this inflection temperature range with a stable nickel-iron-cobalt matrix.
• Table 3 below provides the room temperature tensile properties of alloys at room temperature given the same heat treatment as Table 2.
• Table 4 below provides the 1250°F (677°C) properties of the alloys of Heats 1 to 6 after receiving the heat treatment of Tables 2 and 3.
• the alloys of Heats 1 to 6 provide relatively good high temperature properties with the stable nickel-iron-cobalt matrix.
• Table 5 below provides the 1300°F (704°C) tensile properties of Heats 1, 2 and 4 to 6 heat treated with the heat treatment of Tables 2 to 4.
• Tables 6 and 7 below provide the elevated temperature combination smooth notch bar test data for alloys as heat treated with the heat treatment of Tables 2 to 5.
• Tables 6 and 7 illustrate that the alloys of Heats 1 to 6 are notch ductile and resistant to SAGBO failure.
• Tables 8 and 9 below illustrate the effect of aging treatment temperature on stress rupture properties.
• Tables 8 and 9 illustrate that these alloys provide flexible annealing and aging times. Aging temperatures of 1325°F (718°C), 1375°F (746°C) or 1425°F (774°C) effectively aged the alloys.
• a specific Ni-Fe-Co alloy for replacing the '032 alloy consists essentially of about 39.2 to 40 nickel, about 10 to 11.7 cobalt, about 4.8 to 5.2 niobium, about 3.3 to 3.7 chromium, about 1.2 to 1.6 titanium, about 0.4 to 0.65 aluminum, about 0.35 to 0.45 silicon, about 0 to 0.3 copper, about 0 to 0.2 molybdenum, about 0 to 0.02 carbon, about 0 to 0.015 phosphorus, about 0 to 0.002 sulfur, about 0.0001 to 0.0025 boron and balance iron and incidental impurities.
• Ni-Fe-Co alloys provide superalloys having controlled CTE, SAGBO resistance, corrosion resistance and good strength properties.
• these Ni-Fe-Co alloys provide improved creep resistance while maintaining phase stability and rupture ductility at elevated temperatures.
• treating these Ni-Fe-Co alloys with relatively quick heat treatments produces material suitable for demanding turbine engine applications.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Turbine Rotor Nozzle Sealing (AREA)

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Citations (6)

• 1998
  • 1998-01-15 EP EP98300279A patent/EP0856589A1/fr not_active Withdrawn
  • 1998-01-27 JP JP1453198A patent/JPH10212544A/ja active Pending

Patent Citations (6)

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