US3552953A - Cobalt-chromium base alloy and articles produced therefrom - Google Patents

Cobalt-chromium base alloy and articles produced therefrom Download PDF

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Publication number
US3552953A
US3552953A US790369A US3552953DA US3552953A US 3552953 A US3552953 A US 3552953A US 790369 A US790369 A US 790369A US 3552953D A US3552953D A US 3552953DA US 3552953 A US3552953 A US 3552953A
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cobalt
percent
chromium
phase
alloy
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US790369A
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Franklin D Lemkey
Earl R Thompson
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Raytheon Technologies Corp
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United Aircraft Corp
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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B21/00—Unidirectional solidification of eutectic materials
    • C30B21/02—Unidirectional solidification of eutectic materials by normal casting or gradient freezing
    • 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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C27/00—Alloys based on rhenium or a refractory metal not mentioned in groups C22C14/00 or C22C16/00
    • C22C27/06—Alloys based on chromium

Definitions

  • alloys like certain eutectics as indicated in the patent to Kraft 3,124,- 452, may be solidified to produce articles of pronounced anisotropy.
  • a dispersed carbide phase (Cr, Co)-;C aligns in a cobalt-base solid solution matrix.
  • the alloys of the cobalt-chromium-carbon system offer great potential utility in the advanced gas turbine engines.
  • the particular applications and the particular needs in a given application will, of course, vary.
  • the strength characteristics of such articles are usually preferential as to direction and, in those articles where increased omnidirectional strength is of more fundamental importance, the anisotropic articles may often be less preferred than components exhibiting a lesser degree of directional orientation.
  • the present invention generally contemplates alloys nominally of the cobalt-chromium-carbon type which substantially solidify according to the eutectic-type reaction wherein two primary phases freeze simultaneously from a multi-component system to form a matrix phase consisting of a cobalt base alloy and a dispersed phase consisting of a mixed carbide of the M C type.
  • the alloys of this invention solidify such that the carbide is randomly dispersed throughout the matrix or, upon unidirectional solidification, is dispersed in a skeletal distribution in the matrix. As such, these alloys display substantial omnidirectional strength.
  • the unmodified ternary alloys of this invention in terms of the basic cobalt, chromium, carbon relationship, occupy a limited segment on the eutectic trough which exists in the ternary phase diagram of this system. Accordingly, the ternary alloys lie below the liquidus trough and within the two phase field, solidifying, in fundamental terms, according to the monovariant eutectic reaction:
  • the ternary alloy composition by weight, solidifying by this reaction consists essentially of, 45.2-49.2 percent cobalt, 49-53 percent chromium and about 1.8 percent carbon.
  • the particularly preferred ternary alloy is formulated at the composition, by weight, 49.2 percent cobalt, 49 percent chromium, and 1.8 percent carbon.
  • the present basic alloy is tolerant toward the addition or substitution of certain materials, and, in certain applications some change from the basic ternary composition is desirable.
  • alloys in terms of the melt composition, may be generated from a formulation comprising by weight, 45-55 percent chromium, 1.7-2.2 percent carbon, up to 10 percent nickel, up to 5 percent iron, up to 2 percent aluminum, yttrium and the rare earth elements, balance essentially cobalt.
  • FIG. 1 is a photomicrograph of a unidirectionally solidified specimen of the ternary alloy at the preferred composition taken transverse to the direction of growth X 500).
  • FIG. 2 is a photomicrograph of the same specimen taken in longitudinal section (X500). 5
  • FIG. 3A is a space model phase diagram illustrating a eutectic trough, e-e in a ternary system.
  • FIG. 3B is an isopleth taken along the dotted lines of FIG. 3A.
  • FIG. 3C is a projection of the eutectic trough and the solubility curves on the basal triangle.
  • FIG. 4 is the liquidus diagram for the cobalt-chromiumcarbon system.
  • FIG. 5 is a graph demonstrating the tensile strength of the ternary alloy as a function of temperature.
  • FIG. 6 is a graph depicting the stress-rupture life of the alloys of this invention as compared to a number of competitive alloys.
  • FIG. 7 is a chart demonstrating the results of vane cyclic sulfidation-erosion testing of these alloys as a function of time.
  • FIG. 8 is a graph illustrating the extent of specimen bowing in thermal fatigue testing of various alloys, the arrows indicating the onset of surface cracking.
  • the present approach contemplates the solidification of a melt whose composition substantially corresponds to that at the eutectic trough of some phase diagrams, such a trough being illustrated by way of example by the line e-e of the model ternary diagram of FIG. 3A, which shows a three phase region passing continuously from one binary eutectic horizontal to the other along the line 2-2
  • the vertical section or isopleth indicated by the dotted lines of FIG. 3A is reproduced as FIG. 3B.
  • a liquid of composition X will solidify over the temperature range T to T2-
  • the equilibrium solidification of composition X may be conveniently described by referring to FIG.
  • 3C which is a projection of the eutectic trough and the solubility curves on the basal triangle. Also shown are the tie triangles whose vertices indicate the composition of the liquid and two solid phases in equilibrium. At each temperature level there is a tie triangle. These triangles reduce to the eutectic horizontal in the terminal binary phase diagrams. For the solidification of composition X only the tie triangles corresponding to the beginning of freezing, T and the termination of freezing, T have been shown in FIG. 3C. There are in fact a continuous series of tie triangles between these temperatures.
  • the term monovariant eutectic reaction may conveniently be utilized to describe the above-mentioned solidification reaction in the ternary system including the basic ternary alloys of this invention, the term is not always applicable to the higher order systems.
  • the present formulation does not result in the aligned fibrous carbide phase of the prior compositions but rather in a randomly dispersed mixed carbide phase or, in the case of the unidirectionally solidified structure, in a skeletal distribution of the carbide.
  • the present castings exhibit a greater degree of isotropy and omnidirectional strength than the aligned structures including the M- C carbide.
  • the fundamental premise of the present invention therefore, resides in the formation and random dispersion of the M C -type carbides in a cobalt base alloy matrix of high chromium content. In directionally solidified form these carbides will normally be distributed in a skeletal structure.
  • the basic alloy system from which these structures are formed is the ternary alloy of cobalt, chromium and carbon solidifying accordinging to the monovariant eutectic reaction, particularly in the compositional range, by weight, of 45.2-49.2 percent cobalt, 49-53 percent chromium, and about 1.8 percent carbon.
  • Its elastic modulus at room temperature is 40x10 p.s.i. which compares favorably with the reported elastic moduli of the commercial cobalt-base superalloys in the range of 3.0-36 10 p.s.i. In terms of density, the present alloy density of 7.91 g./cc.
  • the basic ternary composition exhibits a reasonable tolerance insofar as modifications to the basic alloy chemlstry are concerned.
  • modifications to the basic alloy chemlstry are concerned.
  • articles formed of the basic ternary composition unidirectionally solidified at about 10 cm./hr. have displayed unacceptable creep-rupture properties in the intermediate temperature range of 1500-1600 F. While the reasons for this behavior are not fully understood, the behavior is believed to be associated with the allotropic transformation of the cobaltchromium solid solution.
  • modification of the alloy is suggested. Accordingly, the basic alloy was modified, in some instances, to include nickel, a face-centered cubic stabilizer. Nickel substitutions of up to about 10 weight percent are readily tolerated and serve to reduce the transformation temperature and thus to shift it out of the critical range.
  • transformation temperature is similarly and more efiiciently reduced by substituting iron for a portion of the cobalt in these alloys.
  • additions of aluminum, yttrium and therare earth'elements may advantageously be added to these alloys. Such additions are primarily included as modifiers of the solid solution matrix, aluminum, yttrium and the rare earth elements, such as lanthanum frequently being added to the superalloys to promote their oxidation/erosion resistance.
  • An alloy substantially solidifying according to the reaction L a+;8 where on comprises an alloy consisting essentially of, by weight, 25-35 percent chromium, up to about 10 percent nickel, up to about 5 percent iron and up to about 2 percent aluminum, yttrium and the rare earth elements and where [3 consists of a dispersed carbide of the M C type where M includes cobalt, chromium and the other stable carbide-forming elements of the a phase.
  • a unidirectionally solidified metallic article having a substantially two phase microstructure consisting of a. matrix phase and a dispersed phase, the matrix phase consisting essentially of a cobalt-chromium-base alloy, the dispersed phase consisting essentially of a mixed carbide of the generic type (Cr, Co) C in a substantially skeletal distribution.
  • a unidirectionally solidified metallic article having a substantially two phase microstructure consisting of a matrix phase and a dispersed phase, the matrix phase consisting essentially of a cobalt-base alloy containing, by weight, 25-35 percent chromium, up to about 10 percent nickel, up to about 5 percent iron, and up to about 2 percent aluminum, yttrium and the rare earth elements, the dispersed phase consisting of a mixed carbide of the C C type Where M includes cobalt, chromium and the other stable carbide forming elements of the matrix phase alloy.
  • An alloy consisting essentially of, by weight, 45-55 percent chromium, 1.7-2.2 percent carbon, up to 10 percent nickel, up to 5 percent iron and up to 2 percent aluminum, yttrium and the rare earth elements, balance essentially cobalt, said alloy having a microstructure of a dispersion of the M C type carbides in a cobalt base alloy matrix of high chromium content.
  • I References Cited 9.
  • Analloy according to claim wherein the chromium UNITED STATES PATENTS content is about 49 percent by Weight and the carbon cony 5 tent is about 1.8 percent by weight. 3124452 3/1964 Kraft 75"134 10.
  • An alloy consisting of, by weight, 49-53 percent 3434827 3/1969 'Lemkey 75' 134 romium, 1.8-2 percent carbon, balance essentially 5 3,434,892 3/ 19 69 Heimke 7 5 134 balt, said alloy having a microstructure of a dispersion of the M C type carbides in a cobalt base alloy matrix of RICHARD N Pnmary Exammer high chromium content. v y Y 11. A eutectic alloy consisting essentially of, by Weight, 10 X- about 49.2 percent cobalt, 49 percent chromium, and 1.8 135, percent carbon.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Mechanical Engineering (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Manufacture Of Alloys Or Alloy Compounds (AREA)
  • Turbine Rotor Nozzle Sealing (AREA)
  • Heat Treatment Of Nonferrous Metals Or Alloys (AREA)
  • Manufacture And Refinement Of Metals (AREA)
US790369A 1969-01-10 1969-01-10 Cobalt-chromium base alloy and articles produced therefrom Expired - Lifetime US3552953A (en)

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US (1) US3552953A (ja)
JP (1) JPS5013215B1 (ja)
BE (1) BE744234A (ja)
CA (1) CA924128A (ja)
CH (1) CH573983A5 (ja)
DE (1) DE2000325B2 (ja)
FR (1) FR2033230A1 (ja)
GB (1) GB1294293A (ja)
NL (1) NL150516B (ja)
SE (1) SE365556B (ja)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3649225A (en) * 1969-11-17 1972-03-14 United Aircraft Corp Composite coating for the superalloys
US3844845A (en) * 1973-11-15 1974-10-29 Gen Electric Directional composites by solid-state up-transformation
US3847679A (en) * 1973-11-15 1974-11-12 Gen Electric Directional eutectoid composites by solid-state up-transformation
US3891431A (en) * 1971-05-10 1975-06-24 Bbc Brown Boveri & Cie Method of, and apparatus for, controlling the crystalline structure of alloys, and alloys so produced
US3976516A (en) * 1973-10-17 1976-08-24 Bbc Brown Boveri & Company Limited High temperature alloy
US4016014A (en) * 1974-02-11 1977-04-05 Bbc Brown Boveri & Company Limited High temperature alloy
US4088606A (en) * 1974-05-06 1978-05-09 Gould Inc. Cobalt base nox reducing catalytic structure

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS51108228U (ja) * 1975-02-28 1976-08-30

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3649225A (en) * 1969-11-17 1972-03-14 United Aircraft Corp Composite coating for the superalloys
US3891431A (en) * 1971-05-10 1975-06-24 Bbc Brown Boveri & Cie Method of, and apparatus for, controlling the crystalline structure of alloys, and alloys so produced
US3976516A (en) * 1973-10-17 1976-08-24 Bbc Brown Boveri & Company Limited High temperature alloy
US3844845A (en) * 1973-11-15 1974-10-29 Gen Electric Directional composites by solid-state up-transformation
US3847679A (en) * 1973-11-15 1974-11-12 Gen Electric Directional eutectoid composites by solid-state up-transformation
US4016014A (en) * 1974-02-11 1977-04-05 Bbc Brown Boveri & Company Limited High temperature alloy
US4088606A (en) * 1974-05-06 1978-05-09 Gould Inc. Cobalt base nox reducing catalytic structure

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NL7000254A (ja) 1970-07-14
GB1294293A (en) 1972-10-25
DE2000325A1 (de) 1970-09-10
JPS5013215B1 (ja) 1975-05-17
SE365556B (ja) 1974-03-25
CA924128A (en) 1973-04-10
CH573983A5 (ja) 1976-03-31
NL150516B (nl) 1976-08-16
BE744234A (fr) 1970-06-15
DE2000325B2 (de) 1972-06-29
FR2033230A1 (ja) 1970-12-04

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