US3783032A - Method for producing directionally solidified nickel base alloy - Google Patents

Method for producing directionally solidified nickel base alloy Download PDF

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Publication number
US3783032A
US3783032A US00276752A US3783032DA US3783032A US 3783032 A US3783032 A US 3783032A US 00276752 A US00276752 A US 00276752A US 3783032D A US3783032D A US 3783032DA US 3783032 A US3783032 A US 3783032A
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nickel base
alloy
cast body
heat treatment
base alloy
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J Walker
T Sawyer
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General Electric Co
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General Electric Co
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    • 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

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  • the method involves forming a nickel base alloy; containing a carefully controlled combination of gamma, prime forming elements Al, Ti and Ta along with a critical amount of Cr, pouring the molten alloy into a mold and directionally solidifying it into a cast body, removing the low melting segregated phases from the directionally solidified cast body by a dissolution heat treatment to permit the segregated phases to dissolve in solid solution without incipient melting, and cooling the cast body to room temperature.
  • This invention relates to nickel base superalloys which are particularly useful in gas turbine engines. In designing these engines for jet aircraft, it is a requirement that the alloy have good long time rupture properties and have hot corrosion resistance. Thus substantial efforts have been made to improve the properties of the nickel base alloys.
  • the alloy which is treated by the process of the present invention is described in the Aldred et al. US. patent application cited above which is incorporated herein by reference.
  • the alloy consists essentially in weight percent of:
  • the alloy is further characterized in that the sum of Al and Ti is a minimum of 8.1%, the sum of Al, Ti, Ta and 'Nb is in the range of 11.7-12.5%, the sum of Ta and Nb is in the range of 3.6-4.4% and the sum of Mo and W is a minimum of 8.5%.
  • the preferred composition is set forth in Example 1 hereinbelow.
  • FIG. 1 is a photomicrograph (2000 of a cross section of the preferred nickel base alloy subjected to the Standard Heat Treatment;
  • FIG. 2 is a photomicrograph (2000 of a cross section of the preferred nickel base alloy subjected to the novel Dissolution Heat T reatment;
  • FIG. 3 is a graphic representation of the stress-rupture parameters of the preferred nickel base alloy subjected to the Standard Heat Treatment as compared to that subjected to the Dissolution Heat Treatment.”
  • the alloy described hereinabove is poured into a mold and directionally solidified into a cast body by a technique which would be obvious to a person skilled in the art.
  • an elongated columnar macro-grain structure is obtained with substantially unidirectional crystals aligned substantially parallel to the direction of maximum heat flow.
  • the low melting segregate phases are removed from the directionally solidified cast body by a Dissolution Heat Treatment to permit the segregated phases to dissolve in solid solution without incipient melting.
  • the cast body is heated to a temperature below the incipient melting temperature of the segregated phases for a time sulficient to dissolve a portion of the lower melting phases in the matrix whereby the incipient melting temperature of the resulting mass is increased.
  • the temperature is gradually raised, but maintained below the increased incipient melting temperature, until the low melting segregated phases form a substantially homogeneous mass with the matrix.
  • the initial temperature of the dissolution heat treatment is determined by heating the alloy to a predetermined temperature, and removing and microscopically examining it for incipient melting. If incipient melting has occurred, then the temperature is too high and must be decreased. On the other hand, if incipient melting has not occurred, the predetermined temperature may be increased. A starting temperature for the dissolution heat treatment may thus be selected which is just below the temperature at which incipient melting of the lowest melting phase occurs. The heat treatment then proceeds at increasing temperatures up to a point below the temperature at which the solid solution of the alloy melts, but proceeding at a rate sufiiciently slow to avoid melting the low melting phases on subsequent temperature increases, until all the low melting phases are substantially solutionized.
  • the novel heat treatment may be stepwise procedure with holding periods, e.g. 18 F. for 4 hours, or it may be a gradual continuous process, e.g. at a rate of 2.5 C. per hour.
  • holding periods e.g. 18 F. for 4 hours
  • it may be a gradual continuous process, e.g. at a rate of 2.5 C. per hour.
  • the values given are merely for purposes of illustration. For all practical use, the rate should be as rapid as possible and this rate may be determined routinely by a person skilled in the art.
  • the dissolution heat treatment can then be followed by a precipitation hardening heat treatment.
  • EXAMPLE I A preferred alloy having the following nominal composition in weight percent was vacuum melted in a magnesium oxide crucible using standard melting procedures.
  • the molten alloy was cast in a shell mold containing a number of cylindrical cavities approximately 4" in diameter and 6" long and cooled to room temperature.
  • the morphology of the grains in the rods thus formed was typically equiaxed.
  • Each of the ingots was cut into 1%" lengths and cylinders were electromachined therefrom. Mechanical test specimens were machined to produce test bars with the long axis parallel to the longitudinal direction in each ingot.
  • the alloy samples to be tested were heat treated in vacuum using the following schedule which is designated as the Standard Heat Treatment.
  • Step Temperature Time A Heat to 2,102 F Hold for 2 hours. B Heat to 2,228 F Hold for 1 hour. 0 Helium quench to room temperature-- D Heat to 1,994 F Hold for 4 hours. E Helium quench to room temperature F Heat to 1,652 F Hold for 16 hours. G Helium quench to room temperature Following the procedure of Example I, the preferred alloy composition was vacuum melted, cast, directionally solidified and then machined into test specimens. Thereafter, the alloy samples to be tested were heat treated in vacuum using the following schedule which is designated as the Dissolution Heat Treatment.
  • Step Temperature Time A Heart to 2,05% F Hold for 4 hours. B Raise temperature stepwise in 18 Hold for 4 hours at increments up to 2,282 F. each increment.
  • the Dissolution Heat Treatment varies from the Standard Heat Treatment by steps A, B and C. The remaining steps in both procedures are similar.
  • FIG. 3 shows the curve of the stress-rupture parameter for the samples subjected to the Dissolution Heat Treatment.
  • Example II Similar to Example I, a metallographic sample was cut in cross section and a photomicrograph (2000 magnification) is shown in FIG. 2. It is readily apparent that the nonequilibrium phases which were present in FIG. 1, have now been removed. The large island in the upper left-hand corner is identified as a carbide.
  • FIG. 3 A comparison between the samples subjected to the Standard Heat Treatment and the Dissolution Heat Treatment clearly indicates in FIG. 3 that the Dissolution Heat Treatment produces a substantially superior product. This phenomena is explained by the fact that the nonequilibrium phases shown in FIG. 1 have been removed by the novel Dissolution Heat Treatment as shown in FIG. 2. The presence of these nonequilibrium phases are considered to weaken the cast alloy bodies.
  • the low melting segregated phases are removed by heating the body to a temperature below the incipient melting temperature of said phases and for a time sufficient to dissolve a portion of the lower melting segregated phases in the matrix whereby the incipient melting temperature of the resulting mass is increased, and gradually raising the temperature of the heat treatment below the increased incipient melting temperature until the low melting segregated phases form a substantially homogeneous mass with the matrix.
  • thermo treatment comprises heating the cast body to a temperature of about 2084 F. and then raising the temperature stepwise up to a maximum of about 2282 F.

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  • Chemical & Material Sciences (AREA)
  • Mechanical Engineering (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Turbine Rotor Nozzle Sealing (AREA)
  • Manufacture And Refinement Of Metals (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Heat Treatment Of Nonferrous Metals Or Alloys (AREA)
US00276752A 1972-07-31 1972-07-31 Method for producing directionally solidified nickel base alloy Expired - Lifetime US3783032A (en)

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JP (1) JPS4953524A (show.php)
BE (1) BE802680A (show.php)
DE (1) DE2320455A1 (show.php)
FR (1) FR2194795B1 (show.php)
IL (1) IL42114A (show.php)
IT (1) IT987843B (show.php)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3920489A (en) * 1970-03-02 1975-11-18 Gen Electric Method of making superalloy bodies
US3985582A (en) * 1973-07-30 1976-10-12 Office National D'etudes Et De Recherches Aerospatiales (O.N.E.R.A.) Process for the improvement of refractory composite materials comprising a matrix consisting of a superalloy and reinforcing fibers consisting of a metal carbide
US4717432A (en) * 1986-04-09 1988-01-05 United Technologies Corporation Varied heating rate solution heat treatment for superalloy castings
US4755240A (en) * 1986-05-12 1988-07-05 Exxon Production Research Company Nickel base precipitation hardened alloys having improved resistance stress corrosion cracking
US20030145977A1 (en) * 2000-01-19 2003-08-07 Smashey Russell W. Directionally solidified superalloy weld wire

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1511562A (en) * 1974-07-17 1978-05-24 Gen Electric Nickel-base alloys
US4957567A (en) * 1988-12-13 1990-09-18 General Electric Company Fatigue crack growth resistant nickel-base article and alloy and method for making

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3920489A (en) * 1970-03-02 1975-11-18 Gen Electric Method of making superalloy bodies
US3985582A (en) * 1973-07-30 1976-10-12 Office National D'etudes Et De Recherches Aerospatiales (O.N.E.R.A.) Process for the improvement of refractory composite materials comprising a matrix consisting of a superalloy and reinforcing fibers consisting of a metal carbide
US4717432A (en) * 1986-04-09 1988-01-05 United Technologies Corporation Varied heating rate solution heat treatment for superalloy castings
US4755240A (en) * 1986-05-12 1988-07-05 Exxon Production Research Company Nickel base precipitation hardened alloys having improved resistance stress corrosion cracking
US20030145977A1 (en) * 2000-01-19 2003-08-07 Smashey Russell W. Directionally solidified superalloy weld wire
US8466389B2 (en) * 2000-01-19 2013-06-18 General Electric Company Directionally solidified superalloy weld wire

Also Published As

Publication number Publication date
JPS4953524A (show.php) 1974-05-24
FR2194795B1 (show.php) 1977-05-13
FR2194795A1 (show.php) 1974-03-01
BE802680A (fr) 1974-01-23
IT987843B (it) 1975-03-20
IL42114A (en) 1976-02-29
DE2320455A1 (de) 1974-02-14

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