EP0061988A1 - Sinterzyklus mit einem heiss isostatischen Druckschritt bei niedrigem Druck - Google Patents

Sinterzyklus mit einem heiss isostatischen Druckschritt bei niedrigem Druck Download PDF

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Publication number
EP0061988A1
EP0061988A1 EP82630022A EP82630022A EP0061988A1 EP 0061988 A1 EP0061988 A1 EP 0061988A1 EP 82630022 A EP82630022 A EP 82630022A EP 82630022 A EP82630022 A EP 82630022A EP 0061988 A1 EP0061988 A1 EP 0061988A1
Authority
EP
European Patent Office
Prior art keywords
sintering
tungsten carbide
psi
solidus
vacuum
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP82630022A
Other languages
English (en)
French (fr)
Inventor
William A. Reich
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
General Electric Co
Hughes Tool Co
Original Assignee
General Electric Co
Hughes Tool Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by General Electric Co, Hughes Tool Co filed Critical General Electric Co
Publication of EP0061988A1 publication Critical patent/EP0061988A1/de
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/12—Both compacting and sintering
    • B22F3/14—Both compacting and sintering simultaneously
    • B22F3/15—Hot isostatic pressing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/24—After-treatment of workpieces or articles

Definitions

  • This invention relates to a method of sintering a material from powder and of the liquid phase sintering type,e.g., a mixture of tungsten carbide powder and co- ! balt powder, the resulting material being commonly referred to as cemented tungsten carbide.
  • the primary beneficial effects of such a HIP treatment is to reduce or eliminate any small pores which may remain after sintering, and, more significantly, to reduce or eliminate any larger randomly spaced holes, slits or fissures which may be present in the sintered cemented tungsten carbide articles.
  • An object of the present invention is the achievement of many of the benefits of a conventional HIP treatment through a process which avoids the use of the high operating pressures and long cycle times typically associated therewith.
  • Another object of the present invention is to provide an overall more efficient method for sintering and hot isostatic pressing articles.
  • a collateral object of the present invention is to provide a method for healing occasional closed clean flaws in sintered articles which avoids conditions which may lead to undesirable grain growth.
  • an object of the present invention is to provide a method for producing articles formed of tungsten carbide and cobalt powders in which closed clean flaws are removed without resort to a conventional high pressure HIP treatment separate ; from and following conventional sintering.
  • tungsten carbide powder and cobalt powder are mixed, poured into a mold and mechanically pressed to consolidate the powder mixture into a briquette having the form of the mold.
  • the cobalt content ranges up to about 25% by weight of the mixture.
  • the pressed briquette is then sintered in vacuum or in a protective gas atmosphere.
  • the sintering cycle involves peak temperatures of 1350°C to 1450°C, depending on the alloy composition, and times at peak temperature of an hour or more.
  • the powders typically contain a wax to improve their initial compacted integrity, sometimes referred to as "green strength".
  • This wax may be driven off as a separate dewaxing operation at elevated temperatures (approximately 500°C) in a hydrogen atmosphere prior to sintering or in the sintering furnace as an initial, intermediate temperature step before application of the full sintering tempera- ture.
  • a liquid phase forms, consisting of a solution of the carbide in cobalt, and densification of the body follows.
  • the carbide precipitates from solution in the cobalt, and in the case of tungsten carbide and cobalt alloys, the final fully dense structure consists of tungsten carbide in essentially pure cobalt. If the sintering temperature is too high undesirable coarsening of the structure may occur and if it is too low "under-sintering" occurs, evidenced by excessive porosity.
  • the resulting cemented tungsten carbide material may still have a small degree of porosity which is undesirable.
  • the porosity that remains can be characterized either as small evenly distributed pores ranging up to about 25 microns in major dimension or as large randomly spaced holes, slits or fissures as large as 0.25mm as to 2.5mn in major dimension.
  • the large flaws (sometimes hereinafter referred to as large closed clean flaws) consisting of large, randomly spaced holes, slits and fissures have the most serious adverse effects on surface integrity and strength because of their size and random distribution. It is to the elimination or reduction of these large flaws that the present invention is primarily addressed.
  • the present invention provides a process which eliminates the necessity of resorting to the high pressures and long cycle times encountered in conventional HIP treatment in order to heal the randomly spaced closed clean flaws which may remain after conventional vacuum sintering. While the theoretical mechanism is not precisely known, the applicant has observed that a cemented tungsten carbide body appears to exhibit lower strength at sintering temperature during initial sintering than it does when cooled and subsequently heated to the same temperature. The material could be said to have taken a "set” during cooling from the initial sintering temperature. The "structure" of the body at temperature during initial sintering is thought to be unique to that condition such that the application of relatively minor gas pressure after initial sintering has progressed, and before cooling the body to the solid state, results in successful closure of large flaws.
  • the large flaws can be successfully healed as an adjunct to the initial sintering cycle by subjecting the tungsten carbide and cobalt material to gas pressure of 100-1000 psi for 15-60 minutes after vacuum sintering has been completed but! without lowering the temperature of the material below the solidus.
  • Example 1 Conventional vacuum sintering to show a large flaw- Carboloy® 100 powder
  • Example 2 Process of present invention showing healing of large flaw- Carboloy® 100 powder.
  • the resulting cemented tungsten carbide bar from Example; 2 has a healed flaw shown in Figs. 2. (75X), 3 (300X) and 4 (1500X).
  • Example 3 Conventional vacuum sintering to show large flaw - Carboloy®55A powder.
  • Example 4 Process of present invention showing healing of large flaw - Carboloy® 55A powder.
  • the resulting cemented tungsten carbide bar from Example 4 has a healed flaw shown in Figs. 6 (75X), 7 (300X) and 8 ((1500X).
  • Example 5 Process of present invention showing healing of large flaw - Carboloy® 100 powder.
  • the resulting cemented tungsten carbide bar from Example 5 has a healed flaw shown in Figs. 9 (75X), 10(300X) and 11 (1500X).
  • articles treated' by the sintering/low pressure HIP method according to the present invention appear to be free of the localized patches of coarse grains sometimes observed in articles made from the same starting materials only treated by conventional, separate, vacuum sintering and high pressure HIP operations. Freedom from this localized coarse grain structure is viewed as a significant advantage in terms of the strength of the article inasmuch as such grain structure can have deleterious effects very similar to the randomly oriented flaws sought to be reduced or eliminated by the HIP treatment. It is believed that the avoidance of the extended holding times at the typical HIP temperature and pressure may account for the more desirable grain structure observed in articles treated according to the present invention. ;

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Mechanical Engineering (AREA)
  • Powder Metallurgy (AREA)
EP82630022A 1981-03-24 1982-03-22 Sinterzyklus mit einem heiss isostatischen Druckschritt bei niedrigem Druck Withdrawn EP0061988A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US24702881A 1981-03-24 1981-03-24
US247028 1994-05-19

Publications (1)

Publication Number Publication Date
EP0061988A1 true EP0061988A1 (de) 1982-10-06

Family

ID=22933248

Family Applications (1)

Application Number Title Priority Date Filing Date
EP82630022A Withdrawn EP0061988A1 (de) 1981-03-24 1982-03-22 Sinterzyklus mit einem heiss isostatischen Druckschritt bei niedrigem Druck

Country Status (8)

Country Link
EP (1) EP0061988A1 (de)
JP (1) JPS57194201A (de)
AR (1) AR227100A1 (de)
AU (1) AU8184382A (de)
BR (1) BR8201605A (de)
DE (1) DE61988T1 (de)
IL (1) IL65333A0 (de)
ZA (1) ZA821967B (de)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0172164A1 (de) * 1984-02-10 1986-02-26 LUETH, Roy C. Metallurgisches verfahren
EP0235165A1 (de) * 1985-08-29 1987-09-09 Gorham Advanced Materials Institute, Inc. Sinterverfahren unter druck
EP0239881A1 (de) * 1986-03-21 1987-10-07 Uddeholm Tooling Aktiebolag Verfahren zur Herstellung von Formkörpern durch heissisostatisches Pressen von Metallpulver in eine Form
GB2238319A (en) * 1989-11-23 1991-05-29 T & N Technology Ltd Hot isostatically pressed silicon nitride
DE4437053A1 (de) * 1994-10-18 1996-02-08 Widia Gmbh WC-Hartlegierung, Verfahren zu seiner Herstellung und seiner Verwendung
US7682557B2 (en) 2006-12-15 2010-03-23 Smith International, Inc. Multiple processes of high pressures and temperatures for sintered bodies
CN104128610A (zh) * 2014-07-16 2014-11-05 承德昊天硬质合金制品有限公司 合金球齿的制备方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS61130403A (ja) * 1984-11-28 1986-06-18 Hitachi Metals Ltd 高密度材の焼結方法

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3469976A (en) * 1967-07-31 1969-09-30 Du Pont Isostatic hot pressing of metal-bonded metal carbide bodies
GB1300864A (en) * 1969-03-03 1972-12-20 Asea Ab Method of sintering powder bodies
FR2288585A1 (fr) * 1974-10-24 1976-05-21 Howmet Corp Procede de traitement isostatique a chaud de pieces de fonderie
FR2387720A1 (fr) * 1977-04-22 1978-11-17 Krupp Gmbh Procede de fabrication d'elements en metal dur de haute resistance

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3469976A (en) * 1967-07-31 1969-09-30 Du Pont Isostatic hot pressing of metal-bonded metal carbide bodies
GB1300864A (en) * 1969-03-03 1972-12-20 Asea Ab Method of sintering powder bodies
FR2288585A1 (fr) * 1974-10-24 1976-05-21 Howmet Corp Procede de traitement isostatique a chaud de pieces de fonderie
FR2387720A1 (fr) * 1977-04-22 1978-11-17 Krupp Gmbh Procede de fabrication d'elements en metal dur de haute resistance

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0172164A1 (de) * 1984-02-10 1986-02-26 LUETH, Roy C. Metallurgisches verfahren
EP0172164A4 (de) * 1984-02-10 1986-07-23 Roy C Lueth Metallurgisches verfahren.
EP0235165A1 (de) * 1985-08-29 1987-09-09 Gorham Advanced Materials Institute, Inc. Sinterverfahren unter druck
EP0235165A4 (de) * 1985-08-29 1988-08-23 Gorham Int Inc Sinterverfahren unter druck.
EP0239881A1 (de) * 1986-03-21 1987-10-07 Uddeholm Tooling Aktiebolag Verfahren zur Herstellung von Formkörpern durch heissisostatisches Pressen von Metallpulver in eine Form
US4723999A (en) * 1986-03-21 1988-02-09 Uddeholm Tooling Aktiebolag Method of powder metallurgically manufacturing an object
GB2238319A (en) * 1989-11-23 1991-05-29 T & N Technology Ltd Hot isostatically pressed silicon nitride
EP0430318A1 (de) * 1989-11-23 1991-06-05 T&N TECHNOLOGY LIMITED Verfahren zur Herstellung von geformten Gegenständen aus sinterfähigem Pulver
US5089197A (en) * 1989-11-23 1992-02-18 T & N Technology Manufacture of shaped articles from sinterable powder
GB2238319B (en) * 1989-11-23 1994-01-19 T & N Technology Ltd Manufacture of shaped articles from sinterable powder
DE4437053A1 (de) * 1994-10-18 1996-02-08 Widia Gmbh WC-Hartlegierung, Verfahren zu seiner Herstellung und seiner Verwendung
US7682557B2 (en) 2006-12-15 2010-03-23 Smith International, Inc. Multiple processes of high pressures and temperatures for sintered bodies
CN104128610A (zh) * 2014-07-16 2014-11-05 承德昊天硬质合金制品有限公司 合金球齿的制备方法

Also Published As

Publication number Publication date
AR227100A1 (es) 1982-09-15
IL65333A0 (en) 1982-05-31
ZA821967B (en) 1983-01-26
BR8201605A (pt) 1983-02-08
AU8184382A (en) 1982-09-30
DE61988T1 (de) 1983-04-14
JPS57194201A (en) 1982-11-29

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Inventor name: REICH, WILLIAM A.