Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
  • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
  • C22F1/10—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of nickel or cobalt or alloys based thereon
• • 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
  • C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
  • C22C19/055—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 20% but less than 30%
• • 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
  • C22C19/051—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W
  • C22C19/056—Alloys based on nickel or cobalt based on nickel with chromium and Mo or W with the maximum Cr content being at least 10% but less than 20%
• • 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
  • C22C19/07—Alloys based on nickel or cobalt based on cobalt

Definitions

• This invention relates to nickel-cobalt base alloys and particularly nickel-cobalt base alloys having excellent corrosion resistance combined with high strength and ductility at higher service temperatures.
• the Smith patent U.S. No. 3,356,542, issued December 5, 1967, discloses cobalt-nickel base alloys containing chromium and molybdenum.
• the alloys of the Smith patent are corrosion resistant and can be work strengthened under certain temperature conditions to have very high ultimate tensile and yield strength. These alloys can exist in one of two crystalline phases, depending on temperature. They are also characterized by a composition-dependent transition zone of temperatures in which transformation between phases occur. At temperatures above the upper transus, the alloy is stable in the face centered cubic (FCC) structure. At temperatures below the lower transus, the alloy is stable in the hexagonal close-packed (HCP) form.
• FCC face centered cubic
• HCP hexagonal close-packed
• the alloy of the present invention provides an alloy which retains satisfactory tensile and ductility levels and stress rupture properties at temperatures up to about 1300°F. This is a striking improvement in thermomechanical properties and is accomplished by modifying the composition so that the transus is raised to higher temperatures and the precipitation hardening effect is maximized. Thus, the iron and aluminum are reduced to incidental proportions, and titanium or columbium or both are increased to limits described below. Accordingly, as pointed out in my earlier patent, not all alloys whose composition falls within the ranges set out herein are encompassed by the present invention, since many of such compositions would include alloys containing embrittling phases.
• the calculation of the number uses the above formula except that the chemical symbol refers to the "effective atomic fraction" of the element in the alloy.
• This concept takes into account the postulated conversion of a portion of the metal atoms present, particularly nickel, into compounds of the type Ni3X, where X is titanium, columbium or aluminum. These compounds precipitate out of solid solution thus altering the composition of the remaining matrix to reduce the amount of nickel and effectively to increase the amount of the other transition elements.
• the remaining composition has an "effective atomic fraction" of these elements. Consequently many combinations of all the interacting elements can produce the same N v number (small effects on the N v due to carbon and boron are not significant and may be ignored in these calculations).
• the maximum of titanium when used without columbium and using the preferred analysis is 6%.
• the maximum for columbium without titanium is 10%.
• Either titanium or columbium may be used in this alloy, alone or in combination, but must be used so that the resulting N v number does not exceed 2.80.
• the alloy of this invention like those of Smith and my earlier patent is a multiphase alloy forming an HCP-FCC platelet structure.
• the alloys of the present invention broadly comprise the following chemical elements in the indicated weight percentage ranges: Carbon 0.05 max Cobalt 20-40 Molybdenum 6-11 Chromium 15-23 Iron 1.0 max Boron 0.005-0.020 Titanium 0-6 Columbium 0-10 Nickel Bal.
• the preferred aim analysis for melting the alloy of the invention is, in weight percent: Carbon 0.01 max Cobalt 36 Molybdenum 7.5 Chromium 19.5 Iron 1.0 max Boron 0.01 Titanium 3.8 Columbium 1.1 Nickel Bal.
• the alloy of this invention is melted by any appropriate technique such as vacuum induction melting and cast into ingots or formed into powder for subsequent formation into articles by an appropriate known powder metals technique. After casting as ingots, the alloy is preferably homogenized and then hot rolled into plates or other forms suitable for subsequent working.
• the alloy is preferably finally cold worked at ambient temperature to a reduction of cross-section of at least 5% and up to about 40%, although higher levels of cold work may be used but with some loss of thermomechanical properties. It may, however, be cold worked at any temperature below the HCP-FCC transformation zone.
• the alloys After cold working the alloys are preferably aged at a temperature between 800°F and 1350°F for about 4 hours. Following aging the alloys may be air cooled.
• An alloy composition according to this invention was prepared having the composition by weight: C Co Mo Cr Fe B Ti Cb Ni 0.006% 36.3% 7.35% 19.4% 1.04% 0.008% 3.79% 1.20% BAL
• This alloy was hot rolled and divided into two portions, one of which was cold worked to 36% and the other to 48%, aged at 1300°F and formed into test pieces identified by the terms "specimens” which are plain, cylindrical test specimens and “studs” which are threaded test specimens.
• this invention provides unique thermomechanical properties at temperatures in the neighborhood of 1300°F where presently available alloys are no longer serviceable. This provides service temperatures for jet engine fasteners and other parts for higher temperature service, thus making it possible to construct such engines and other equipment for higher operating temperatures and greater efficiency than heretofore possible.

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Citations (7)

• 1988
  • 1988-10-04 EP EP88202205A patent/EP0365716A1/de not_active Withdrawn
  • 1988-10-06 SE SE8803555A patent/SE465037B/sv not_active IP Right Cessation
  • 1988-11-24 JP JP29716188A patent/JPH02145738A/ja active Pending

Patent Citations (7)

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