Classifications

• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23B—PRESERVING, e.g. BY CANNING, MEAT, FISH, EGGS, FRUIT, VEGETABLES, EDIBLE SEEDS; CHEMICAL RIPENING OF FRUIT OR VEGETABLES; THE PRESERVED, RIPENED, OR CANNED PRODUCTS
  • A23B4/00—General methods for preserving meat, sausages, fish or fish products
  • A23B4/03—Drying; Subsequent reconstitution
  • A23B4/031—Apparatus for drying
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J3/00—Processes of utilising sub-atmospheric or super-atmospheric pressure to effect chemical or physical change of matter; Apparatus therefor
  • B01J3/06—Processes using ultra-high pressure, e.g. for the formation of diamonds; Apparatus therefor, e.g. moulds or dies
  • B01J3/062—Processes using ultra-high pressure, e.g. for the formation of diamonds; Apparatus therefor, e.g. moulds or dies characterised by the composition of the materials to be processed
• • 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
• • 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
  • B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
  • B22F5/007—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of moulds
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B27—WORKING OR PRESERVING WOOD OR SIMILAR MATERIAL; NAILING OR STAPLING MACHINES IN GENERAL
  • B27J—MECHANICAL WORKING OF CANE, CORK, OR SIMILAR MATERIALS
  • B27J1/00—Mechanical working of cane or the like
  • B27J1/003—Joining the cane side by side
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2203/00—Processes utilising sub- or super atmospheric pressure
  • B01J2203/06—High pressure synthesis
  • B01J2203/0605—Composition of the material to be processed
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2203/00—Processes utilising sub- or super atmospheric pressure
  • B01J2203/06—High pressure synthesis
  • B01J2203/0605—Composition of the material to be processed
  • B01J2203/062—Diamond
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2203/00—Processes utilising sub- or super atmospheric pressure
  • B01J2203/06—High pressure synthesis
  • B01J2203/0605—Composition of the material to be processed
  • B01J2203/063—Carbides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2203/00—Processes utilising sub- or super atmospheric pressure
  • B01J2203/06—High pressure synthesis
  • B01J2203/0605—Composition of the material to be processed
  • B01J2203/0645—Boronitrides
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J2203/00—Processes utilising sub- or super atmospheric pressure
  • B01J2203/06—High pressure synthesis
  • B01J2203/065—Composition of the material produced
  • B01J2203/0655—Diamond
• • 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
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy

Definitions

• the present invention relates to a method for preparing a sintered body having high hardness, in which a hard layer of polycrystalline diamond (hereinafter, referred as
• the present invention relates to a method for preparing a sintered body having high hardness, wherein the abnormal growth of diamond particles during the sintering process can be suppressed.
• WC/Co type ultra-hard substrate is widely used as a material for tools.
• Fig. 1 is a schematic view of illustrating such sintered body with high hardness in conventional arts.
• a conventional sintered body with high hardness is prepared by: positioning a raw material powder where a diamond powder and a binding powder comprising cobalt as a main ingredient are mixed, on a WC/Co type ultra-hard substrate; and charging the substrate into a fire resistant metal crucible made of a material having a high melting point of 2000 ° C or more, for example Ta, Mo, Nb and the like to sinter it under the conditions of high temperature and high pressure, where diamond is stable.
• a main binding material of the PCD sintered layer may be those diffused out of the ultra-hard substrate, or cobalt that is contained in the binding powder of the raw material powder.
• Cobalt is melted under said sintered temperature and pressure condition to form a liquid phase of cobalt, which is served as a catalyst for the PCD forming reaction.
• the level of activity of diamond in such liquid cobalt becomes very high, therefore the growth and binding reactions of diamond particles, which were diffused into the liquid cobalt, are promoted to finally form a polycrystalline.
• the crucible is made of a material having a high melting point of 2000 ° C or more, it can be stably maintained without being melted during the PCD sintering process.
• the method of conventional arts has a problem of abnormal growth of particles near the surface ofthe diamond adjacent to the crucible.
• the particle growth of diamond is occurred, it is impossible to produce a sintered body thereof having microcrystallines with a targeted particle size.
• the roughness in the cross-section ofthe material is deteriorated.
• the particle growth inhibiting materials could be segregated in the PCD layer, which causes a problem of deteriorating the homogeneosity in mechanical characteristics of the sintered body.
• the particle growth inhibiting materials are minutely milled to the smaller size relative to the diamond powder and mixed in homogenous way, however, the problem of segregation ofthe materials is not completely solved.
• materials other than cobalt i.e. a binding material are packed into the gap between diamond particles, thereby causing another problem of deteriorating the compactness of sintering.
• the present invention has been designed to solve those problems of conventional arts.
• the present invention is to provide a method of preparing a sintered body having high hardness, in which particle growth can be suppressed by using a crucible suppressing the generation of a pool of liquid cobalt, which is the cause of the particle growth.
• the method of preparing a sintered body with high hardness to achieve said object according to the present invention comprises:
• a step of preparing a raw material powder for sintering which comprises a diamond powder
• a step of forming a hard layer of PCD on said ultra-hard substrate by charging the ultra- hard substrate with the raw material powder for sintering into a crucible made of a sintered body comprised of: at least one material selected from a group consisting of catalyst transition metals from Period of 4-6 of Group 4A-6A of Periodic table of elements, and carbides, nitrides and carbo-nitrides thereof and each solid solution thereof; and at least one binding material selected from Fe, Co and Ni, and then carrying out sintering under the conditions of high temperature and high pressure, where diamond is stable.
• the amount ofthe binding material is 5-30wt% in the crucible composition.
• the average particle size of the diamond powder is preferably 3 m or less.
• the raw material powder for sintering preferably comprises a powder of binding material comprised of at least one selected from a group consisting of a catalyst transition metal from Period of 4-6 in Group 3 A ⁇ 7A and Group 8 of Periodic table of elements, and carbides, nitrides, borides and carbo-nitrides thereof and each solid solution thereof.
• the present inventors have found that the cause of particle growth being occurred around the surface of diamond is based on the formation of a liquid pool of cobalt formed along the wall of a crucible made of a fire resistant metal, wherein the cobalt is melted out from the ultra-hard substrate or the binder. Because the level of activity of the diamond particles is very much increased in the liquid pool of cobalt, it has been thought that diamond particles adjacent to the liquid pool become grow in abnormal way.
• the liquid pool of cobalt is formed by a phenomenon, so-called 'squeeze out'.
• 'squeeze out' means that as the diamond particles are getting closer to each other upon the process of sintering, the cobalt component between the diamond particles is squeezed out.
• the conventional crucible is comprised of a pure metal selected from, for example Mo, Ta, Nb and the like, or alloys thereof, which are stable and compact at sintering temperature, the liquid cobalt which has been squeezed out to the outside starts to form a liquid pool thereof along the wall of the crucible.
• the present inventors made a research on how to prevent or reduce the liquid pool of cobalt formed along the wall of a crucible. As a result of such investigation, the inventors have found that, when a crucible used for sintering is one being capable of absorbing the liquid pool of cobalt, the squeezed-out liquid cobalt can be absorbed and the particle growth can be prevented.
• suitable is a crucible made of sintered body comprised of: at least one material selected from a group consisting of catalyst transition metals from Period of 4-6 of Group 4A ⁇ 6A of Periodic table of elements, and carbides, nitrides and carbo- nitrides thereof and each solid solution thereof; and at least one binding material selected from Fe, Co and Ni.
• a material having a high melting point which is comprised of catalyst transition metals from Period of 4 ⁇ 6 of Group 4A ⁇ 6A of Periodic table of elements, and carbides, nitrides and carbo-nitrides thereof and each solid solution thereof, remains as a solid state without being melted under a PCD sintering condition of 1000 ⁇ 1700°C and 3 ⁇ 10Gpa, and has a function of inhibiting the particle growth.
• Fe, Co and Ni in the crucible made of a sintered body are materials, which form a isomorphous solid solution with cobalt that is a binding material of the diamond powder and are melted under said sintering conditions.
• the crucible Before sintering, the crucible has a structure where a material having a high melting point is studded in a binding material having a low melting point, wherein the binding material is intervened between the materials having a high melting point so as to make interconnections between the materials having a high melting point.
• the binding material component of the crucible is made of at least one of
• the wall of the cmcible is composed of nearly 100% of cobalt
• the particles of the material having a high melting point in the binding material are filtrated into the liquid material formed along the wall of the crucible, and the liquid cobalt of the wall of the cmcible flows into the liquid of the binding material in the crucible.
• the preferred amount ofthe binding material is in the range of 5 ⁇ 30wt%.
• the characteristic feature of the invention is that the particle growth is inhibited by making an intervention of a material for inhibiting the particle growth or a material for obstructing the formation ofthe liquid cobalt pool only on the area around the surface of the PCD layer where considerable particle growth is mainly occurred, i.e. the area where the liquid cobalt pool is formed, as well as by making the liquid cobalt pool flown to the cmcible direction, being contrary to the conventional methods for inhibiting particle growth by making an intervention of a material for inhibiting particle growth between diamond powders.
• the present invention is advantageous since it eliminates the problems occurred in prior arts such as segregation of a material for inhibiting particle growth or decrease in sintering compactness.
• the present invention has special meaning particularly in case of sintering a diamond powder having fine particle size of 3 / an or less.
• the raw material powder can be comprised of a pure diamond powder without additional powder of a binding material.
• a binding material usually added to the raw material powder for sintering is a catalyst metal such as Fe, Co, Ni and the like, however, other catalyst metals may be further added to impart other characteristics to the raw material powder.
• the powder of a binding material may use at least one selected from transition metals from Period of 4-6 of Group 3A-7A and 10 of Periodic table of elements, and carbides, nitrides, borides and carbo-nitrides thereof and each solid solution thereof. Description of Drawings
• Fig. 1 is a schematic view of illustrating a method for preparing a sintered body according to conventional arts
• Fig. 2 is a schematic view of illustrating a method for preparing a sintered body according to the present invention
• Fig. 3 a is an electro-microscopic picture of a sintered body prepared according to a method of conventional arts
• Fig. 3b is an electro-microscopic picture of a sintered body prepared according to the method ofthe present invention.
• a powder of a binding material comprising a cobalt powder having 1.5 zm of the average particle size and a WC powder having 0.8 .m of the average particle size was mixed with diamond powders having each 2 ⁇ m and 4/a ⁇ of the average particle size, according to the composition shown in the above table to provide a raw material powder for sintering.
• the raw material powder for sintering is loaded onto an ultra-hard substrate of WC-8wt% Co, and the resulted substrate with the mixed raw material powder is charged into a cmcible of Wc-6wt% Co and of Ta, respectively. Then they were undergone a sintering process under the condition of 1600°C and 6Gpa for 1 hour by using a belt-type high pressure apparatus.
• Fig. 3b is a picture showing the cross-section of a sintered body made of a raw material powder for sintering having the composition of specimen A in the above table. As shown in Fig. 3b, it can be recognized that particle growth was hardly occurred. In the meantime, in specimens A and B which were charged into each Ta cmcible, particle growth as much as approximately 100 / a ⁇ or more was seriously occurred. Fig.
• 3 a is a picture showing the cross-section of a sintered body made of a raw material powder for sintering having the composition of specimen B in the above table, and it can be recognized that particle growth was seriously occurred.

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• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Wood Science & Technology (AREA)
• Zoology (AREA)
• Food Science & Technology (AREA)
• Polymers & Plastics (AREA)
• Forests & Forestry (AREA)
• Powder Metallurgy (AREA)
• Cutting Tools, Boring Holders, And Turrets (AREA)

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• 2004
  • 2004-01-13 KR KR1020040002148A patent/KR100568970B1/ko not_active IP Right Cessation
• 2005
  • 2005-01-11 WO PCT/KR2005/000079 patent/WO2005068113A1/en active Application Filing
  • 2005-01-11 EP EP05721763A patent/EP1715972A1/de not_active Withdrawn

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