US3718461A - Cobalt-base alloys - Google Patents

Cobalt-base alloys Download PDF

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Publication number
US3718461A
US3718461A US00173159A US3718461DA US3718461A US 3718461 A US3718461 A US 3718461A US 00173159 A US00173159 A US 00173159A US 3718461D A US3718461D A US 3718461DA US 3718461 A US3718461 A US 3718461A
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United States
Prior art keywords
cobalt
alloy
alloys
chromium
tungsten
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Expired - Lifetime
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US00173159A
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English (en)
Inventor
M Dewey
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Fulmer Research Institute Ltd
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Fulmer Research Institute Ltd
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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

Definitions

  • This invention is concerned with cobalt-base alloys which have excellent resistance to oxidation and hot-corrosion attack, combined with high mechanical strength up to temperatures of 900 C.
  • Alloys based on a cobalt or nickel matrix are known; certain of them are known as superalloys because of their use for components operating at a high temperature, such as in gas turbine engines.
  • Such cobalt or nickel matrix alloys are generally of two types:
  • alloys in which chromium is added to the cobalt or nickel to provide resistance to oxidation and hot-corrosion attack the alloys containing chromium in an amount of from 20 to 30%.
  • Other alloying additions in particular tungsten, manganese, silicon, molybdenum, iron and carbon, may be made for matrix strengthening and improved high temperature properties.
  • cobalt or nickel-base alloys have not been available which combine the optimum properties of these two types of alloy, that is which combine high strength at room and elevated temperature with high resistance to oxidation and to hot-corrosion, for example by halides.
  • a range of cobalt-base alloys has now been developed, which alloys have this advantageous combination of properties.
  • the new cobalt-base alloys of the invention consist, by weight, of:
  • chromium 15.0 to 35.0%preferably from 18.0 to
  • aluminium 5.0 to l2.0%-preferably from 6.0 to 12.0%
  • the balance being cobalt, which constitutes at least 45% of the alloy, and unavoidable impurities.
  • the alloys may additionally contain up to 15% of iron and/or up to 15% of nickel.
  • aluminium which serves to strengthen the matrix by the precipitation of intermetallic compounds and also imparts high resistance to oxidation and hot corrosion.
  • Aluminium also imparts hardness to these alloys and both aluminium and tungsten impart hardness. This is due to a microstructure consisting of an intimate mixture of grains and particles of cobalt, also containing in solid solution the elements chromium, tungsten, manganese, aluminium and, if present in the alloycomposition, iron and nickel, and grains and particles of the ordered body centred cubic compound CoAl, which can also contain in solid solution the elements chromium, tungsten, manganese, iron and nickel.
  • Alloy A Percent Carbon 0.01 Chromium 20.1 Tungsten 7.5 Iron 8.2 Nickel F- 10.3 Manganese 0.5 Aluminium 6.0
  • Ingots were prepared of these alloys in a conventional manner which may be summarised as follows: melting and alloying were carried out in an induction heated vacuum furnace. The melt temperature was maintained at 1550 C. and the alloys were cast into ingot moulds made of steel to form ingots 2" in diameter. These ingots were then extruded at 1300 C. to rod 0.5" in diameter. Samples of the rod were heat treated at a temperature of 1250 C. followed by air cooling to room temperature, re-heated to a temperature between 700 and 980 C. and aged for times of 1 to 90 hours. These alloys were tested for resistance to oxidation at temperatures up to at least 1000 C. in comparison with the commercially available alloys, Stellite 31 and Nimonic 90, both of which are widely used because of their good high temperature oxidation resistance.
  • the nominal compositions of the alloys Stellite 31 and Nimonic 90 are:
  • the high temperature oxidation test consisted of heating cylindrical samples of known weight in air at 1000 C. for 25 hours, after which they were removed from the furnace and allowed to cool to room temperature. The oxide film formed on each sample was examined for evidence of spalling and the weight of each sample re-determined. This sequence was repeated four times, when the test was stopped, at which point the sample had been oxidised for a total time of 100 hours. The samples were then sectioned and metallographically examined and the depth of internal oxidation measured. The results were:
  • the alloys according to the present invention also have the advantage that oxidation occurs uniformly without preference for the grain boundaries.
  • oxidation occurs uniformly without preference for the grain boundaries.
  • preferential intergranular oxidation occurs and this is particularly detrimental to the mechanical properties after oxidation.
  • These tests were carried out in a rig specially designed to simulate the operating conditions in a gas turbine engine. Cylindrical samples of known weight were spun during the test, which was conducted at a temperature of 870 C. with 4 parts of synthetic sea salt DEF 1053 per million parts of air injected into the burner.
  • alloys A to D were also determined at room and elevated temperatures and are summarised in Tables II and III in comparison with those of Stellite 31 and Nimonic 90.
  • a cobalt-base alloy which has a high resistance to oxidation and hot corrosion attack and has a high mechanical strength at temperatures up to 900 C., which alloy consists of, by weight:
  • the balance being cobalt, which constitutes at least 45% by weight of the alloy, and unavoidable impurities.
  • An alloy according to claim 11 which contains from 28.0 to 32.0% chromium.
  • An alloy according to claim 11 which contains from 5.0 to 10.0% tungsten.
  • An alloy according to claim 1 which contains from 6.5 to 8.0% aluminium.
  • a cobalt-base alloy which has a high resistance to oxidation and hot-corrosion attack and has a high mechanical strength at temperatures up to 900 C., which alloy consists of, by weight:
  • An alloy according to claim 6 which contains from 18.0 to 22.0% chromium.
  • An alloy according to claim 6 which contains from 28.0 to 32.0% chromium.
  • An alloy according to claim 6 which contains from 5.0 to 10.0% tungsten.
  • An alloy according to claim 6 which contains from 6.5 to 8.0% aluminium.
  • a cobalt-base alloy which has a high resistance to oxidation and hot-corrosion attack and has a high mechanical strength at temperatures up to 900 C., which alloy consists of, by weight:
  • the balance being cobalt, which constitutes at least 45% by weight of the alloy, and unavoidable impurities.
  • a cobalt-base alloy according to claim 11 which consists substantially of:
  • a cobalt-base alloy according to claim 11 which consists substantially of:
  • a cobalt-base alloy according to claim 11 which consists substantially of:
  • a cobalt-base alloy according to claim 11 which consists essentially of:
  • a cobalt-base alloy according to claim 11 which consists essentially of:

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Powder Metallurgy (AREA)
  • Diaphragms For Electromechanical Transducers (AREA)
  • Manufacturing Of Magnetic Record Carriers (AREA)
US00173159A 1970-08-24 1971-08-19 Cobalt-base alloys Expired - Lifetime US3718461A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB4069970 1970-08-24

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US3718461A true US3718461A (en) 1973-02-27

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US00173159A Expired - Lifetime US3718461A (en) 1970-08-24 1971-08-19 Cobalt-base alloys

Country Status (5)

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US (1) US3718461A (fr)
BE (1) BE771657A (fr)
DE (1) DE2142041A1 (fr)
FR (1) FR2105978A5 (fr)
GB (1) GB1302934A (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4152181A (en) * 1977-12-27 1979-05-01 United Technologies Corporation Cobalt alloy heat treatment
US20050211045A1 (en) * 2002-07-01 2005-09-29 Guangshan Zhu Composite circular slicer knife
US20120202008A1 (en) * 2009-10-16 2012-08-09 Garcia Aparicio Juan Carlos Parts with different surface finishes and the procedure to obtain them

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4339509A (en) 1979-05-29 1982-07-13 Howmet Turbine Components Corporation Superalloy coating composition with oxidation and/or sulfidation resistance

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4152181A (en) * 1977-12-27 1979-05-01 United Technologies Corporation Cobalt alloy heat treatment
US20050211045A1 (en) * 2002-07-01 2005-09-29 Guangshan Zhu Composite circular slicer knife
US7257899B2 (en) * 2002-07-01 2007-08-21 Premark Feg L.L.C. Composite circular slicer knife
US20120202008A1 (en) * 2009-10-16 2012-08-09 Garcia Aparicio Juan Carlos Parts with different surface finishes and the procedure to obtain them
US9283620B2 (en) * 2009-10-16 2016-03-15 Phibo Cad-Cam, S.L. Parts with different surface finishes and the procedure to obtain them

Also Published As

Publication number Publication date
FR2105978A5 (fr) 1972-04-28
BE771657A (fr) 1971-12-31
DE2142041A1 (de) 1972-03-02
GB1302934A (fr) 1973-01-10

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