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
  • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
  • B22F10/10—Formation of a green body
  • B22F10/18—Formation of a green body by mixing binder with metal in filament form, e.g. fused filament fabrication [FFF]
• • 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
  • B22F3/20—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces by extruding
• • 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
  • B22F3/22—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces for producing castings from a slip
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B33—ADDITIVE MANUFACTURING TECHNOLOGY
  • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
  • B33Y10/00—Processes of additive manufacturing
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/05—Mixtures of metal powder with non-metallic powder
  • C22C1/051—Making hard metals based on borides, carbides, nitrides, oxides or silicides; Preparation of the powder mixture used as the starting material therefor
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C29/00—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides
  • C22C29/02—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides
  • C22C29/06—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds
  • C22C29/08—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on carbides or carbonitrides based on carbides, but not containing other metal compounds based on tungsten carbide
• • 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 the production of tungsten carbide based or cermet hard metal tools or components using the powder injection moulding or extrusion method and a method for producing a binder system therefore.
• Hard metals based on tungsten carbide are composites consisting of small ( ⁇ m-scale) grains of at least one hard phase in a binder phase. These materials always contain the hard phase tungsten carbide (WC) .
• tungsten carbide WC
• other metal carbides with the general composition (Ti, Nb, Ta, W) C may also be included, as well as metal carbonit ⁇ des, e.g., Ti(C, N).
• the binder phase usually consists of cobalt (Co).
• Other binder phase compositions may also be used, e.g., combinations of Co, Ni, and Fe, or Ni and Fe.
• Industrial production of tungsten carbide based hard metals often includes blending of given proportions of powders of raw materials and additives in the wet state using a milling liquid.
• This liquid is often an alcohol, e.g. ethanol or water, or a mixture thereof.
• the mixture is then milled into a homogeneous slurry.
• the wet milling operation is made with the purpose of deagglomerating and mixing the raw materials intimately. Individual raw material grains are also disintegrated to some extent.
• the obtained slurry is then dried and granulated, e.g. by means of a spray dryer.
• the granulate thus obtained may then be used in uniaxial pressing of green bodies or for extrusion or injection moulding.
• Injection moulding is common in the plastics industry, where material containing thermoplastics or thermosetting polymers are heated and forced into a mould with the desired shape.
• the method is often referred to as Powder Injection Moulding (PIM) when used in powder technology.
• PIM Powder Injection Moulding
• the method is preferably used for parts with complex geometry.
• Injection moulding is performed using the mixed feedstock.
• the material is heated to 100-240 0 C and then forced into a cavity with the desired shape.
• the thus obtained part is cooled and then removed from the cavity.
• Removing the binder from the obtained part can be obtained by extraction of the parts in a suitable solvent and/or by heating in a furnace with a suitable atmosphere. This step is often referred to as the debinding step.
• Extrusion of the feedstock comprises steps 1, 3 and 4 above. Instead of forcing the feedstock into a cavity of the desired shape, the feedstock is continuously forced through a die with the desired cross section.
• the solids loading, ⁇ , of the feedstock is the volumetric amount of hard constituents, compared to the organic constituents, ⁇ can be cal- culated using the following equation:
• P s is the density of the cemented carbide as sintered
• p v is the mean density of the organic constituents
• p ⁇ is the density of the feedstock, measured with a helium pycnometer.
• Pores close to the surface of the green body will instead collapse to form surface pores, as will pores located directly in the surface of the green body.
• the pores in the surface will severely decrease the macroscopic mechanical strength of the sintered material.
• the metallic binder filled former pores in the bulk of the material will decrease the mechanical strength of the sintered material as well.
• Figure 1 shows a LOM, light optical micrograph, with a magnification about 100Ox of the microstructure of a cemented carbide according to prior art.
• Figure 2 shows a LOM, light optical micrograph, with a magnification about 100Ox of the microstructure of a cemented carbide according to the invention.
• the method according to the present invention comprises the following steps :
• the organic binders are added in the beginning of the screw and the powdered hard constituents are added by side feeders, making sure the powders are mixed into a melt and also making sure the temperature does not fall below the melting temperature of the organic binders.
• the powdered hard constituents can be added through several side feeders along the twin screw extruder or the material can be run through the twin screw extruder several times to make sure the temperature does not fall below the melting temperature of the organic bind- ers.
• the powdered hard constituents are pre heated before being added to the molten organic binder to make sure that the temperature does not fall below the melting temperature of the organic binders.
• the material is then formed into pellets with a size of approximately 4x4 mm.
• the part obtained in injection moulding is cooled and then removed from the cavity.
• the extrudates are cut in pieces of desired length.
• the invention can be used for all compositions of cemented carbide and all WC grain sizes commonly used as well as for titanium carbonitride based materials .
• the WC or Ti (C, N) grain size shall be 0.2-1.5 ⁇ m with conventional grain growth inhibitors .
• the WC or Ti (C, N) grain size shall be 1.5-4 ⁇ m.
• a WC-13 wt-% Co submicron cemented carbide powder was made by wet milling 780 g Co-powder (OMG extra fine), 38.66 g Cr 3 C 2 (H C Starck) , 5161 g WC (H C Starck DS80), 20.44 g W metal powder, 16 g Fisher-Tropsch wax (Sasol Hl) and 22 g stearic acid in 1.6 1 milling liquid consisting of ethanol and water (80:20 by weight) for 40 h.
• the stearic acid is added in this stage of the process to work as a granule forming agent, when spray drying the slurry.
• the resulting slurry was sprayd ⁇ ed to a granulated powder.
• Example 1 The powder made in Example 1 was mixed by kneading 2500 g powder from Example 1 with 50.97 g Polypropylene-polyethylene copolymer (RD360 MO, Borealis) and 50.97 g Paraffin wax (Sasol Wax) in a Z-blade kneader mixer (Werner & Pfleiderer LUK 1,0) .
• the Z-blade kneader was heated to 170'C and the raw material was added.
• the mixer was run until a smooth viscous feedstock developed. This resulted in a feedstock with a density of 8.23 g/ml, corresponding to a ⁇ of 0.553.
• Example 1 The powder made in Example 1 was mixed by kneading 2500 g powder from Example 1 with 50.97 g Polypropylene-polyethylene copolymer (RD360 MO, Borealis) and 45.87 g Paraffin wax (Sasol Wax) and 5.06 g petroleum jelly (Merkur VARA AB) in a Z-blade kneader mixer (Werner & Pfleiderer LUK 1,0). The Z-blade kneader was heated to 170'C and the organic binders were added to the mixer. The polymer was added first and then the waxes .
• Example 4 (Comparative) The feedstock made in example 2 was fed into an injection moulding machine (Battenfeld HM 60/130/22). The machine was used for the injection moulding of a Seco Tools Mimmaster 10 mm endmill green body.
• Example 5 The feedstock made in example 3 was fed into an injection moulding machine (Battenfeld HM 60/130/22) .
• the machine was used for the injection moulding of a Seco Tools Mimmaster 10 mm endmill green body.
• Example 6 (Comparative) The parts from example 4 were debound by extraction and sintered in a Sinter-HIP furnace (PVA COD733R) at 1420 0 C with a total soaking time of 60 min. After 30 min at the peak hold temperature, the furnace pressure was raised to 3 MPa Ar.
• PVA COD733R Sinter-HIP furnace
• the parts were cut for inspection.
• the parts from example 4 were free from carbon pores, eta-phase and pores, i.e. AOO BOO COO according to ISO 4505.
• the parts showed Co-lakes and open surface pores. See figure 1.
• the parts from example 5 were debound by extraction and sintered in a Sinter-HIP furnace (PVA COD733R) at 1420 0 C with a total soaking time of 60 min. After 30 min at the peak hold temperature, the furnace pressure was raised to 3 MPa Ar.
• PVA COD733R Sinter-HIP furnace
• the parts from example 5 were free from carbon pores, cracks, eta-phase and pores, i.e. AOO BOO COO according to ISO 4505. There were no surface pores and the microstructure showed an even cobalt distribution. See figure 2.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Powder Metallurgy (AREA)

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• 2009
  • 2009-11-18 JP JP2011537397A patent/JP2012509408A/ja not_active Withdrawn
  • 2009-11-18 US US13/130,687 patent/US20110248422A1/en not_active Abandoned
  • 2009-11-18 WO PCT/SE2009/051307 patent/WO2010059116A1/en active Application Filing
  • 2009-11-18 CN CN2009801465889A patent/CN102223971A/zh active Pending
  • 2009-11-18 KR KR1020117011434A patent/KR20110089281A/ko not_active Application Discontinuation
  • 2009-11-18 EP EP09827829A patent/EP2367652A1/en not_active Withdrawn

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