WO2009068154A2 - Poudre de co thermiquement stable - Google Patents

Poudre de co thermiquement stable Download PDF

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Publication number
WO2009068154A2
WO2009068154A2 PCT/EP2008/009262 EP2008009262W WO2009068154A2 WO 2009068154 A2 WO2009068154 A2 WO 2009068154A2 EP 2008009262 W EP2008009262 W EP 2008009262W WO 2009068154 A2 WO2009068154 A2 WO 2009068154A2
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WO
WIPO (PCT)
Prior art keywords
oxide
powder
dispersion strengthened
solution
oxide powder
Prior art date
Application number
PCT/EP2008/009262
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English (en)
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WO2009068154A3 (fr
Inventor
Anja Serneels
Bert-Jan Kamphuis
Original Assignee
Umicore
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.)
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Publication date
Application filed by Umicore filed Critical Umicore
Publication of WO2009068154A2 publication Critical patent/WO2009068154A2/fr
Publication of WO2009068154A3 publication Critical patent/WO2009068154A3/fr

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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
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/026—Spray drying of solutions or suspensions
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C32/00—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ
    • C22C32/001—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides
    • C22C32/0015—Non-ferrous alloys containing at least 5% by weight but less than 50% by weight of oxides, carbides, borides, nitrides, silicides or other metal compounds, e.g. oxynitrides, sulfides, whether added as such or formed in situ with only oxides with only single oxides as main non-metallic constituents
    • C22C32/0026—Matrix based on Ni, Co, Cr or alloys thereof

Definitions

  • the invention relates to an oxide dispersion strengthened Co powder as a binder material in the manufacture of diamond tools and a precursor, and a process used for preparing such powder.
  • Standard Co powder has sufficient hardness at sintering temperatures up to 850°C, but for higher sintering temperatures, which are needed when a considerable amount of WC has to be added, the hardness drops because of excessive grain growth.
  • powders having hardness values exceeding those of the current available Co powders especially, but not only, when sintered at higher sintering temperatures.
  • Oxide dispersion strengthening is a widely known strengthening mechanism for metals and alloys. This was already mentioned in US 3,741,748 specifically for powder with anisodimensional platelets as host particles. Another example can be found in JP62- 050434, where MgO is forcedly injected in a molten metal bath based on the composition of Haynes® alloy 188 to provide for a dispersion strengthened cobalt base alloy. The difficulty lies in the homogeneous distribution of fine oxide. Metals or alloys made by casting suffer from segregation and/or agglomeration of the relatively lighter oxide phase prior to casting. Powders to which an oxide is added in the final stage by mixing different powders do not show a homogeneously distributed fine oxide phase.
  • the object of the present invention is to provide fine Co powder, containing metal oxide as a grain growth inhibitor during hot pressing, also called pressure sintering, in which a piece is sintered by simultaneously applying heat and pressure.
  • the Co powder is made based on a novel process that allows the formation of a fine and homogeneously distributed oxide phase.
  • a dispersion strengthened Co - M oxide powder having:
  • M is one element selected from the list consisting of Mg, Mn, Ca, Cr, Al , Y, Si, Na, Ti, Zr, Zn and V; or
  • M is at least two elements selected from the list consisting of Mg, Mn, Ca, Cr, Al , Y, Si, Na, Ti, Zr, Zn and V; the other components in the powder consisting of Co, oxygen and unavoidable impurities.
  • the average particle size is preferably less than 10 ⁇ m, more preferably less than 5 ⁇ m and most preferably less than 2 ⁇ m.
  • the Co - M oxide powder comprises less than 1.2 wt% of M, and more preferably than 0.5 wt% of M.
  • the element M is Mg.
  • the invention also covers the use of an oxide dispersion strengthened Co - M oxide powder, wherein M is one or more oxide forming elements selected from the list consisting of Mg, Mn, Ca, Cr, Al , Y, Si, Na, Ti, Zr, Zn and V, in the manufacture of sintered pieces, whereby said M oxide is homogeneously dispersed in the Co - M oxide powder.
  • the sintering temperature should be above 800°C, preferably between 850°C and HOO 0 C, and more preferably between 85O 0 C and 950°C.
  • the Co - M oxide powder has an average particle size of less than 10 ⁇ m, more preferably less than 5 ⁇ m, and most preferably less than 2 ⁇ m.
  • the Co - M oxide powder comprises preferably less than 1.2 wt% of M, more preferably less than 0.5 wt% of M.
  • the element M is Mg.
  • the Co - M oxide powder is prepared by heating a cobalt phase precursor in a reducing atmosphere, said precursor having a homogenous distribution of M in a cobalt phase. This precursor could be a mixed Co-M salt prepared by
  • the mixed Co-M salt preferably represents a mixed hydroxide, a mixed oxalate or a mixed carbonate.
  • the precursor is a mixed Co-M oxide prepared by
  • aqueous solution of the powder constituents Co and M said solution being either one or a mixture of a chloride solution, a sulphate solution, and a nitrate solution;
  • the processes used to make the Co - M oxide powder are proven to be economic on a large industrial scale.
  • the powder according to the invention gives a high sintered hardness, in particular when high sintering temperatures, e.g. above 850°C are used.
  • the invention also covers the use of the Co - M oxide powder described above in the manufacture of diamond containing cutting tools.
  • the particle size of the powder is less than 20 ⁇ m as measured with the Fisher SSS, in order that the powder is sinterable at moderate temperatures; advantageously it is less than 10 ⁇ m.
  • the loss of mass by reduction in hydrogen of less than 2% corresponds to a sufficiently low oxygen content of the Co phase; higher oxygen contents would allow the diamonds to degrade during the sintering operation.
  • the above mentioned M oxide is necessary to avoid excessive grain growth during sintering. If grain growth is limited, hardness remains high. Particularly at sintering temperatures of 850°C and above, the presence of the oxide dispersion gives hardness values clearly above those of standard Co powders. If the sintered hardness of a powder remains high at high sintering temperatures, the powder is called thermally stable.
  • Sintered hardness can be tuned by changing the oxide dispersion content and by influencing the morphology of the precursor by selecting appropriate conditions in the precipitation process. In such way hardness levels well above the current available hardness levels of sintered Co powders can be obtained.
  • the powder of the invention may be prepared by heating, in a reducing atmosphere, a precursor containing Co and the oxide forming element(s), with the oxide forming element(s) dispersed very finely in the Co containing compound.
  • the oxide forming element(s) is chosen in such a way that it forms an oxide that does not transform to a metal in the reducing conditions needed to form Co metal powder, nor during the typical sintering conditions to form the diamond tool segments.
  • Suitable stabilising elements are therefore Mg, Mn, Ca, Cr, Al , Y, Si, Na, Ti, Zr, Zn and V.
  • Th and U could be envisaged but are less desirable because of their radioactivity.
  • the precursors may, among other methods, be prepared by any or a combination of the following methods (a) to (f).
  • (a) Mixing an aqueous solution of a salt or salts of one or more constituents with an aqueous solution of a base, a carbonate, a carboxylic acid, a carboxylate, or a mixture of these, so that an insoluble or poorly soluble compound containing cobalt and the oxide forming element(s) is formed.
  • carboxylic acids or corresponding carboxylates are suitable that form an insoluble or poorly soluble compounds with the aqueous solution of the salt of the constituent.
  • Examples of a suitable carboxylic acid and carboxylate are oxalic acid or potassium oxalate. Acetic acid and metal acetates on the other hand are not suitable.
  • Spray drying is a suitable drying method. Not all salts of the constituents are suitable for the above mentioned procedures. Those salts that produce precursors that, after undergoing reduction, form a residue containing elements other than the intended ones or oxygen, are not suitable. The other salts are in principle suitable. Precursors may need further strainghtforward processing such as washing to remove impurities or milling to adapt the particle size to the required final product.
  • a mixture of precursors, provided the differences in composition are limited, may also be used.
  • Fig.1 Line scan (with a JEOL scanning electron microscope) showing the distribution of Mg and O in thermally stable Co powder according to this invention.
  • Fig.2 Microstructure of the invented powder (a) and of Extra Fine Cobalt powder produced by Umicore (b) after hot pressing during 3 minutes at 950°C.
  • Fig.3 Line scan showing the distribution of Mg and O in hot pressed powder of this invention.
  • Fig.4 Element mapping showing the distribution of Mg and O in hot pressed powder of this invention.
  • Fig.5 Fisher size as function of reduction temperature for Precursor No.1 (dotted line) and Precursor No.2 (solid line) of this invention.
  • Fig.6 Oxygen content as function of reduction temperature for Precursor No.1 (dotted line) and Precursor No.2 (solid line) of this invention.
  • Fig.7 Rockwell B hardness as function of hot pressing temperature with circles for the powders of this invention (dotted line for Precursor No.1 with reduction temperature 450°C and solid line for Precursor No.2 with reduction temperature 560°C) and with triangles for Extra fine Co powder from Umicore.
  • Fig.8 Resilience as function of hot pressing temperature with dotted line for Precursor No.1 with reduction temperature 450 0 C and solid line for Precursor No.2 with reduction temperature 560°C.
  • Fig.9 Fisher size (squares) and oxygen content (diamonds) as function of reduction temperature used for Co 09 7s Mg 00 2 5 (OH) 2 precursor powder.
  • Fig.10 Rockwell B hardness as function of hot pressing temperature with cross marks for Powder No.3 of this invention and with triangles for Extra fine Co powder from Umicore.
  • Figure 1 shows with a line scan (intensity vs. distance, taken in the middle of the picture above) that Mg and O are homogeneously distributed in an Co - MgO powder according to the invention.
  • Figure 2 shows the microstructure and the difference in grain size for a powder of this invention (a) and for Extra Fine Cobalt powder produced by Umicore (b), both hot pressed during 3 minutes at 950°C. The latter shows several coarse grains while the microstructure for the powder of this invention shows only very small grains. Excessive grain growth is inhibited by the presence of finely dispersed metal oxide particles.
  • This example relates to the preparation of a powder according to the invention by mixing a cobalt chloride solution (17Og Co/1) with a magnesium chloride solution (63g Mg/1) in a ratio giving the desired Co/Mg ratio of the end product and drying the mixed solution by spraying it in a furnace heated to 680 °C giving a dry mixed oxide powder.
  • the mixed oxide powder is washed, dried and milled.
  • Mg content of the oxide precursor powder is 0.17 wt% for Precursor No.l and 0.47 wt% for Precursor No.2.
  • the physical properties of the oxide precursor powders are given in Table 1. Table 1: Physical properties of oxide precursors.
  • Example 2 This example relates to the reduction of the oxide precursors prepared in Example 1 in a furnace at different temperatures, in a stream of hydrogen, for 7.5 hours. Fisher size and oxygen content thus obtained are shown in Figure 5 and Figure 6 respectively for Precursor No.l (dotted line) and Precursor No.2 (solid line). The oxygen content is measured with Leco equipment according to a Leco Application Note on 'Ultra Low Nitrogen and Oxygen in Iron, steel, Nickel-Base, and Cobalt-Base Alloys'. This does not show the oxygen present in difficult to reduce oxides of metals like Zr, Ta, Ti, Mg,....
  • the oxygen content can be measured according to a Leco Application note 'Determination of Oxygen and Nitrogen in Reactive/Refractory Metals and Their Alloys'. Using this method higher oxygen content is obtained.
  • the Mg content of the obtained Co powders is 0.2 wt% and 0.65 wt% respectively.
  • the reduction temperature is chosen to give the lowest oxygen content for a Fisher size below or close to 1.5 ⁇ m.
  • Example 3 This example relates to a series of tests comparing the hardness after hot pressing for the powders of this invention prepared as indicated in Example 2 and for Extra Fine Cobalt powder produced by Umicore, which is considered as the standard powder for the manufacture of diamond tools.
  • Disc-shaped compacts diameter 20 mm, were sintered by hot pressing for 3 minutes at 750, 800, 850, 900 and 950°C in graphite moulds, under a pressure of 35MPa.
  • Rockwell B hardness vs. sintering temperature is shown in Figure 7 with circles for the powders of Example 2 (dotted line for Precursor No.l with reduction temperature 450°C and solid line for Precursor No.2 with reduction temperature 560°C) and with triangles for Extra fine Co powder from Umicore.
  • the resilience values obtainable with the powder of the invention are lower than those of Extra Fine Cobalt powder produced by Umicore, which are typically 60 J/cm 2 , but are higher than some of the commercially available pre-alloyed powders for diamond tools, for example 10 J/cm 2 for Cobalite ® OLS.
  • This example relates to the preparation of a powder according to this invention.
  • a precursor is produced by dissolving suitable amounts of cobalt sulphate and magnesium sulfate in water.
  • the precipitate is separated from the mother liquor.
  • the solid is dried, e.g. in a convection oven to a constant mass.
  • the solid has a molar composition: Co 0 975 Mg 0025 (OH) 2 . It was reduced at different temperatures during 7.5 hours under hydrogen atmosphere. Fisher size (squares, axis on the right) and oxygen content (diamonds, axis on the left) at different reduction temperatures are shown in Figure 9.
  • the Mg content of the obtained Co powder (Powder No.3) is 1.04 wt%.
  • the example relates to a series of tests showing the sinterability of a powder produced according to Example 5 (with 1.04 wt% Mg) in the same conditions as Example 3, with a reduction temperature of 850°C. Density and hardness after hot pressing at the indicated temperature for this Powder No.3 are given in Table 2 below and Rockwell B hardness is shown in Figure 10. Hardness values are very high compared to commercially available Co powder (triangles) and remain high for high sintering temperatures. Sintered density (geometrical and Archimedes) is noted in table 2 relative to a theoretical density of 8.68 g/cm 3 .
  • This Example relates to the preparation of a Co powder containing a metal oxide by mixing 99.8 wt% Co EF powder made by Umicore with 0.2 wt% nano-sized SiO 2 powder.
  • the mixing was performed in a Turbula mixer both with and without the addition of WC balls. In both cases agglomeration of the SiO 2 powder was visually detected by the appearance of light coloured clusters in the Co powder.
  • Disc-shaped compacts were sintered in the same conditions as in Example 3. Sintered density and hardness are shown in Table 3 indicating a drastic drop in hardness for hot pressing at 950°C. Thus the desired thermally stable behaviour is not obtained.
  • Table 3 Hot pressed density and hardness for a mixed Co and SiO 2 powder.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Manufacture Of Metal Powder And Suspensions Thereof (AREA)
  • Powder Metallurgy (AREA)

Abstract

L'invention porte sur l'utilisation d'une poudre de Co renforcée par une dispersion d'oxyde comme liant dans la fabrication d'outils diamantés par frittage sous pression. L'invention porte sur un procédé de fabrication de poudre de Co renforcée par une dispersion d'oxyde, l'oxyde étant fin et distribué de façon homogène dans la poudre de Co. La présence de l'oxyde évite une croissance de grain excessive pendant le frittage aux températures élevées, maintenant la dureté suffisamment élevée.
PCT/EP2008/009262 2007-11-26 2008-11-04 Poudre de co thermiquement stable WO2009068154A2 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
EP07022838 2007-11-26
EP07022838.2 2007-11-26
US99666407P 2007-11-29 2007-11-29
US60/996,664 2007-11-29
EP08009328 2008-05-21
EP08009328.9 2008-05-21

Publications (2)

Publication Number Publication Date
WO2009068154A2 true WO2009068154A2 (fr) 2009-06-04
WO2009068154A3 WO2009068154A3 (fr) 2009-08-13

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Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105014082A (zh) * 2014-04-25 2015-11-04 河北工程大学 一种低温结晶真空脱水法制备弥散强化铁基合金用预合金粉末的方法
CN105834446A (zh) * 2016-04-12 2016-08-10 同济大学 一种超薄层状NiO-CoOx纳米片负载NiCo纳米粒子复合材料的合成方法
CN108115142A (zh) * 2017-12-25 2018-06-05 富耐克超硬材料股份有限公司 金刚石复合片及其制备方法
CN109128208A (zh) * 2017-06-16 2019-01-04 荆门市格林美新材料有限公司 一种掺杂铝的钴粉的制备方法
CN114873652A (zh) * 2022-06-02 2022-08-09 兰州理工大学 一种高振实密度钴氧化物的制备方法

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4343594C1 (de) * 1993-12-21 1995-02-02 Starck H C Gmbh Co Kg Kobaltmetallpulver sowie daraus hergestellte Verbundsinterkörper
WO1997021844A1 (fr) * 1995-12-08 1997-06-19 N.V. Union Miniere S.A. Poudre pre-alliee et son utilisation pour la fabrication d'outils diamantes

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4343594C1 (de) * 1993-12-21 1995-02-02 Starck H C Gmbh Co Kg Kobaltmetallpulver sowie daraus hergestellte Verbundsinterkörper
WO1997021844A1 (fr) * 1995-12-08 1997-06-19 N.V. Union Miniere S.A. Poudre pre-alliee et son utilisation pour la fabrication d'outils diamantes

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN105014082A (zh) * 2014-04-25 2015-11-04 河北工程大学 一种低温结晶真空脱水法制备弥散强化铁基合金用预合金粉末的方法
CN105014082B (zh) * 2014-04-25 2018-01-16 河北工程大学 一种低温结晶真空脱水法制备弥散强化铁基合金用预合金粉末的方法
CN105834446A (zh) * 2016-04-12 2016-08-10 同济大学 一种超薄层状NiO-CoOx纳米片负载NiCo纳米粒子复合材料的合成方法
CN109128208A (zh) * 2017-06-16 2019-01-04 荆门市格林美新材料有限公司 一种掺杂铝的钴粉的制备方法
CN108115142A (zh) * 2017-12-25 2018-06-05 富耐克超硬材料股份有限公司 金刚石复合片及其制备方法
CN108115142B (zh) * 2017-12-25 2019-12-24 富耐克超硬材料股份有限公司 金刚石复合片及其制备方法
CN114873652A (zh) * 2022-06-02 2022-08-09 兰州理工大学 一种高振实密度钴氧化物的制备方法

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