US3713815A - Cast cobalt-base eutectic type alloy - Google Patents

Cast cobalt-base eutectic type alloy Download PDF

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US3713815A
US3713815A US00132836A US3713815DA US3713815A US 3713815 A US3713815 A US 3713815A US 00132836 A US00132836 A US 00132836A US 3713815D A US3713815D A US 3713815DA US 3713815 A US3713815 A US 3713815A
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percent
cobalt
alloy
chromium
carbon
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US00132836A
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D Boone
D Koss
D Peacock
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RTX Corp
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United Aircraft Corp
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    • 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

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  • the present invention relates to, in general, the cobalt/ chromium/carbon alloys at substantially the monovariant eutectic composition and, in particular, to such alloys provided with high temperature oxidation-erosion resistance and as unidirectionally cast.
  • Another carbide reinforced cobalt/chromium/carbon alloy solidifying according to the monovariant eutectic reaction, at a nominal composition, by weight, of 41 percent chromium, 2.4 percent carbon, balance cobalt, known as UARL 73C, may be unidirectionally solidified to provide castings incorporating aligned lamellae of a M7C3-type carbide, (Cr,Co)qC3, embedded in a cobalt/chromium solid solution matrix, as described in the patent to Thompson et al. 3,564,940. These two patents both share a common assignee with the present invention.
  • these alloy systems are reasonably tolerant to the addition of certain other elements to the basic chemistry in the sense that certain additions do not unduly interfere with the basic phenomenon of solidication according to the monovariant eutectic reaction upon which the principal advantageous properties of the basic alloy is dependent. 'And this tolerance may be utilized to advantage to further improve the oxidation resistance of the basic alloy per se as well as its coatability with the well-known protective aluminide coatings, particularly for very high ternperature exposure.
  • the present invention contemplates a high strength cobalt-base alloy containing chromium, carbon, aluminum and an active ingredient such as yttrium, scandium and the rare earth elements, substantially solidifying according to the monovariant eutectic reaction.
  • alloy compositions generically contemplated are those wherein the cobalt, chromium and carbon content are fixed to provide solidiication according to the monovariant eutectic reaction, particularly within the general range of 35-53 percent chromium and 1.8-2.6 percent carbon, together with about 4-8 percent aluminum, and up to about 0.5 percent yttrium, scandium or a rare earth element, balance cobalt.
  • FIG. 1 is a photomicrograph of the alloy, Co-49Cr- 19C, illustrating the microstructure thereof comprising about 43 volume percent of a skeletal-like MZSCS carbide (Cr,Co)23Cs, in a cobalt solid solution matrix (1000x before reduction) (unetched).
  • FIG. 2 is a photomicrograph of an alloy of the composition Co-41Cr-2.4C showing an M703 carbide embedded in a cobalt/chromium solid solution matrix. This section was taken normal to the surface following exposure at 2012 F. for 20 hours in 0.1 atmosphere oxygen (500x before reduction) (unetched).
  • FIG. 3 is a photomicrograph of a transverse section of directionally solidified Co-45Cr-5.5Al-1.7C0.1Sc (1000x before reduction) (etched).
  • FIG. 4 shows the microstructure of a section normal to the surface of a Co46.4Cr-6Al-2C alloy exposed at 20l2 F. for 24 hours in stagnant air (1000x before reduction) (etched).
  • FIG. 5 is a graph summarizing the results of oxidation-erosion testing of the Co-46.5Cr6.2Al-2.lC-0.1Sc alloy at 2l00 F. together with coated and uncoated cornmercially available contemporary alloys.
  • the common and distinguishing feature of the alloys of the present invention within the ranges indicated is that, at a fixed pressure, they are basically monovariant thermodynamically and involve, with respect to the basic cobalt/ chromium/ carbon ternary system, the three phase equilibrium between the melt and two solids over a temperature and composition range and not, as in the binary or pseudo-binary systems, at a fixed temperature and composition.
  • those alloys of the composition, by weight, of 45-55 percent chromium, 1.7-2.2 percent carbon, balance cobalt may be solidified to form a skeletal dispersion of MZSCS type carbides in a cobaltbase matrix.
  • the composition containing 49 percent chromium, 1.9 percent carbon, balance cobalt, known as UARL 236C contains about 43 volume percent of the (Cr,Co)23C6 carbide.
  • the microstructure of this alloy is shown in FIG. 1.
  • alloys of the basic composition 35-45 percent chromium, 2.2-2.6 percent carbon, balance cobalt may be unidirectionally solidied in a cobalt/chromium matrix.
  • the alloy containing 41 percent chromium, 2.4 percent carbon balance cobalt is identified as UARL 73C.
  • the basic ternary alloys exhibit usable strengths to very high temperatures.
  • testing has proven that cobalt alloys which depend upon the formation of Cr203 for protection from corrosive attack cannot be utilized above about l800 F. because of severe degradation of the underlying substrate.
  • metallographic examination of the UARL 73C alloy exposed to a high temperature oxidizing environment shows evidence of surface chromium depletion and internal oxidation of the carbide particles. See FIG. 2.
  • coatings comprising protective aluminides are known to provide oxidation-erosion protection to temperatures in excess of 1800* F., coatability of the basic ternary alloys is in fact limited, particularly insofar as the generation of thick aluminide coatings is concerned.
  • the alloys ofthe present invention obtain their inherent oxidation-erosion resistance at temperatures above 1800 F. from the preferential formation upon oxidation not of chromium oxides but of alumina while at the same time retaining the basic metallurgical structure associated with the carbide reinforced cobalt-base matrix.
  • the coated conventional alloy specimens oxidize at the increased rate associated with the uncoated alloys while the alloy of the present invention continues to oxidize at the uniform and pre- 4 dictable rate.
  • This performance is shown graphically in FIG. 5 for the alloy consisting of, by weight, 46.5 percent chromium, 6.2 percent aluminum, 2.1 percent carbon, 0.1 percent scandium, balance cobalt.
  • the microstructure of the directionally solidified alloy comprising 45 percent chromium, 5.5 percent aluminum, 1.7 percent carbon, 0.1 percent scandium, balance cobalt is shown in FIG. 3. This may be compared with the microstructure of the alloy comprising 46.4 percent chromium, 6 percent aluminum, 2 percent carbon showing the condition of the alloy after oxidation, FIG. 4.
  • the WI-52 will be recognized as that having the nominal composition, by weight, of 21 percent chromium, 11 percent tungsten, 2 percent columbium plus tantalum, 1.75 percent iron, .45 percent carbon, balance cobalt.
  • the U-700 alloy consists of, 15 percent chromium, 15.3 percent cobalt, 3.4 percent titanium, 4.3 percent aluminum, 4.4 percent molybdenum, .07 percent carbon, .02 percent boron, balance nickel.
  • a unidirectionally solidified alloy article consisting essentially of, by weight, 45-55 percent chromium, 1.7- 2.2 percent carbon, 4-8 percent aluminum, up to about 0.5 percent yttrium, scandium or a rare earth element, balance essentially cobalt, said alloy having a microstructure comprising a dispersion of (Cr,Co)23C6 type carbides in a cobalt-base alloy matrix of high chromium and alu- References Cited minum content.
  • a unidirectionally solidified alloy article consisting UNITED STATES PATENTS essentially of, by Weight, 35-45 percent chromium, 2.2- 3552953 1/1971 Lemkey et al- 75-171 2.6 percent carbon, 4-8 percent aluminum, up to about 5 3564940 2/1971 Thompson et al '75*-171 0.5 percent yttrium, scandium or a rare earth element, balance essentially cobalt, said alloy having a microstruc- RICHARD o DEAN Prlmary Exammer ture comprising a dispersion of (Cr,C0)7C3 type carbides U S C] X R in substantial alignment in a cobalt-base alloy matrix of high chromium and aluminum content. 10 75-134 F, 176; 148-32

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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)
  • Manufacture Of Alloys Or Alloy Compounds (AREA)
US00132836A 1971-04-09 1971-04-09 Cast cobalt-base eutectic type alloy Expired - Lifetime US3713815A (en)

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US13283671A 1971-04-09 1971-04-09

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US (1) US3713815A (enExample)
JP (1) JPS4848321A (enExample)
BE (1) BE780682A (enExample)
CA (1) CA988746A (enExample)
CH (1) CH546828A (enExample)
DE (1) DE2216693A1 (enExample)
FR (1) FR2135139B1 (enExample)
IL (1) IL38970A0 (enExample)
IT (1) IT950948B (enExample)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2655397C2 (ru) * 2014-02-11 2018-05-28 Сименс Акциенгезелльшафт Улучшенная износостойкость высокотемпературной конструкционной детали, придаваемая кобальтовым покрытием

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
RU2655397C2 (ru) * 2014-02-11 2018-05-28 Сименс Акциенгезелльшафт Улучшенная износостойкость высокотемпературной конструкционной детали, придаваемая кобальтовым покрытием
US10100651B2 (en) 2014-02-11 2018-10-16 Siemens Aktiengesellschaft Wear resistance of a high-temperature component imparted by a cobalt coating

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BE780682A (fr) 1972-07-03
JPS4848321A (enExample) 1973-07-09
IT950948B (it) 1973-06-20
CH546828A (fr) 1974-03-15
FR2135139A1 (enExample) 1972-12-15
IL38970A0 (en) 1972-05-30
DE2216693A1 (de) 1972-10-19
CA988746A (en) 1976-05-11
FR2135139B1 (enExample) 1973-06-29

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