Classifications

• • 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
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/05—Metallic powder characterised by the size or surface area of the particles
• • 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
  • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
  • B22F1/05—Metallic powder characterised by the size or surface area of the particles
  • B22F1/054—Nanosized particles
• • 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
  • B22F3/10—Sintering only
  • B22F3/1017—Multiple heating or additional steps
  • B22F3/1028—Controlled cooling
• • 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
  • B22F3/10—Sintering only
  • B22F3/1035—Liquid phase sintering
• • 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
• • 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
  • C22C19/00—Alloys based on nickel or cobalt
  • C22C19/07—Alloys based on nickel or cobalt based on cobalt
• • 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
• • 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
  • C22C29/067—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 comprising a particular metallic binder
• • A—HUMAN NECESSITIES
  • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
  • A01B—SOIL WORKING IN AGRICULTURE OR FORESTRY; PARTS, DETAILS, OR ACCESSORIES OF AGRICULTURAL MACHINES OR IMPLEMENTS, IN GENERAL
  • A01B15/00—Elements, tools, or details of ploughs
• • 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
  • B22F2003/248—Thermal after-treatment
• • 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
  • B22F2005/001—Cutting tools, earth boring or grinding tool other than table ware
• • 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
  • B22F9/04—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling
  • B22F2009/043—Making metallic powder or suspensions thereof using physical processes starting from solid material, e.g. by crushing, grinding or milling by ball milling
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B28—WORKING CEMENT, CLAY, OR STONE
  • B28D—WORKING STONE OR STONE-LIKE MATERIALS
  • B28D1/00—Working stone or stone-like materials, e.g. brick, concrete or glass, not provided for elsewhere; Machines, devices, tools therefor
  • B28D1/18—Working stone or stone-like materials, e.g. brick, concrete or glass, not provided for elsewhere; Machines, devices, tools therefor by milling, e.g. channelling by means of milling tools
  • B28D1/186—Tools therefor, e.g. having exchangeable cutter bits
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02F—DREDGING; SOIL-SHIFTING
  • E02F9/00—Component parts of dredgers or soil-shifting machines, not restricted to one of the kinds covered by groups E02F3/00 - E02F7/00
  • E02F9/28—Small metalwork for digging elements, e.g. teeth scraper bits

Definitions

• the invention relates to a sintered carbide material, in particular a hard metal, with 70-95% by weight of tungsten carbide in dispersed form and a binder phase, the binder phase having a metallic binder material, in particular Co.
• EP 2 691 198 B1 describes such a sintered carbide material, namely a hard metal body, and a method for its production.
• a powder is mixed comprising coarse-grain tungsten carbide, a superstoichiometric proportion of carbon and cobalt powder.
• tungsten in powder form was added to the powder.
• the tungsten powder and the cobalt powder had an average particle size of about 1 pm.
• the coarse-grain tungsten carbide had an average particle size of 40.8 ⁇ m.
• this powder was ground in a ball mill, and hexane and paraffin wax were added thereto. A green compact was pressed from this mixture and this green compact was then sintered. Subsequent to the sintering process, the obtained cemented carbide material was subjected to a heat treatment. It was heated to 600°C and held at this temperature for 10 hours.
• the sintered carbide material was subjected to an analysis. It has been shown that the sintered carbide material has nanoparticles in the binder phase, with the nanoparticles having a size of less than 10 nm.
• the nanoparticles were formed by the eta phase (Co 3 W 3 C) or (Co 6 W 6 C) or theta phase (Co 2 W 4 C).
• the grain size of the nanoparticles was less than 10 nm.
• the nanoparticles are accompanied by a strengthening of the binder phase.
• the hardness of the sintered carbide material can thus be increased.
• the disadvantage of these materials is the lack of thermal stability of the nanoparticles. As a result, they are only suitable to a limited extent for high-temperature applications or for applications in which a high temperature input occurs. Very high temperatures occur on the tool surface due to friction when working rock and milling asphalt and concrete.
• the hard material tungsten carbide has a high hot hardness at these temperatures and is not very affected by it.
• the strength of the metallic binder drops dramatically at these temperatures.
• the reduced strength of the metallic binder leads to increased abrasive wear and/or extrusion of the binder phase as a result of the stresses caused by use. As a result, the tungsten carbide grains can no longer be held in the hard metal.
• a sintered carbide material in particular hard metal, which has a reinforced binder phase.
• the binder phase is strengthened by the intermetallic phase material.
• the intermetallic phase material forms a crystalline intercalation in the metallic binder.
• This intermetallic phase material has a significantly higher strength compared to the metallic binder material in which it is embedded. On the surface of the cemented carbide material exposed to wear attack, for example, the intermetallic phase material reduces erosion or extrusion of the metallic binder material when used, for example, in a tillage tool.
• the movement of the tillage tool and the loosened soil material as well as the remaining soil material creates an abrasive and mechanical load on the sintered carbide material.
• the tungsten carbide grains counteract this wear attack with sufficient wear resistance.
• the problem here is the binding material, which has a significantly lower strength than tungsten carbide. Since, according to the invention, the intermetallic phase material is now integrated in the binder phase, rapid erosion or extrusion of the metallic binder material is prevented.
• the intermetallic phase material also strengthens the internal structure of the cemented carbide material. If severe, sudden stresses occur, the crystals of the intermetallic phase material reduce or prevent the tungsten carbide particles from sliding off in the area of the binder phase connecting them, and thus excessive plastic deformation of the binder phase. In particular, the individual crystals of the intermetallic phase material support one another. This has a considerable advantage, particularly at high tool application temperatures, since the strength of the cobalt in the binder phase is reduced at such temperatures, but the intermetallic phase material still reliably provides sufficient support for the binder material.
• the wear resistance of the sintered carbide material can be achieved with the solution according to the invention.
• the use of the sintered carbide material according to the invention in the form of a cutting tip of a pick for road milling machines results in up to 50% higher wear resistance! It has been shown that such a significant increase in wear resistance can be achieved both when milling asphalt and concrete road surfaces.
• the working areas of tools for machining, loosening, conveying and processing vegetable or mineral materials or building materials can be designed, in particular in the field of agriculture or forestry or road, mining or tunnel construction.
• the proportion of metallic binder material in the sintered carbide material is 1-28% by weight, preferably 1-19% by weight.
• the entire proportion or almost the entire proportion of this metallic binder material can be formed by Co.
• the binder material has other components in addition to Co, in particular dissolved W, C, Ni, Al and/or Fe.
• crystal lattices Al,X
• X in the form of W as well as Mo and/or Nb and/or Ti and/or Ta and/or Cr and/or V is present.
• the binder phase has two or more intermetallic phase materials or only a single intermetallic phase material.
• a cemented carbide material according to the invention can be characterized in that the proportion of intermetallic phase material in the binder phase is in the range between 25% by weight and 70% by weight, preferably 30% by weight and 70% by weight, more preferably in the range between 35% by weight % and 60% by weight, particularly preferably in the range between 40% by weight and 50% by weight.
• the remaining proportion of the binder phase in the range between 70% by weight and 30% by weight can be formed by the metallic binder material.
• the metallic binder material which, in accordance with the above statements, may contain Co and optionally further components.
• sintered carbide materials are formed which can be used over a wide range of applications to protect components from wear.
• anti-wear applications can be realized in which the sintered carbide material can be used for anti-wear armoring of surfaces, for example of screen carriers in high-performance screens, for example in the processing of oil sand.
• Applications according to the invention are also conceivable in which the surfaces of soil working tools are covered with the sintered carbide material, at least in certain areas.
• a sintered carbide material according to the invention can also be characterized in that the proportion of intermetallic phase material in the binder phase is in the range between 35% by weight and 60% by weight.
• the remaining proportion of the binder phase in the range between 65% by weight and 40% by weight is formed by the metallic binder material, which, in accordance with the above statements, can contain Co and optionally other components.
• sintered carbide materials are formed, with which sophisticated tillage tools can be created, in which severe shock-type loads often act on the tool. For example, this excavator teeth of buckets, tools from Crushers, shredders, mulchers, milling machines, drills can be equipped with one or more such cemented carbide materials.
• a sintered carbide material according to the invention can also be characterized in that the proportion of intermetallic phase material in the binder phase is in the range between 40% by weight and 50% by weight.
• the remaining proportion of the binder phase in the range between 60% by weight and 50% by weight is formed by the metallic binder material, which, in accordance with the above statements, can contain Co and optionally other components.
• sintered carbide materials are formed with which high-performance tools, for example cutting elements for soil cultivation, in particular picks, drill bits for augers or agricultural soil cultivation tools (ploughshares, cultivator tips, rotary harrow tines... .), can be created. It is conceivable that, for example, the cutting tip of such picks consists of a material body made of the sintered carbide material according to the invention.
• the metallic binder material and/or the intermetallic phase material has Nb and/or Ti and/or Ta and/or Mo and/or V and/or Cr, with preferably one or more of these materials in the dissolved form in the binder phase and/or in the carbide form in the binder phase.
• one or more of the aforementioned components is/are integrated into the crystal lattice of at least part of the intermetallic phase material.
• the titanium atom or another material from the aforementioned group
• the intermetallic phase material can be separated out more effectively, since the start of the precipitations already takes place at higher temperatures and the diffusion rate is significantly higher here.
• this measure allows the sintering process to be set stoichiometrically with regard to the proportion of carbon because the titanium (or the other material mentioned above) takes over the job of the tungsten.
• this measure can significantly increase the heat resistance of the sintered carbide material.
• the proportion of carbon is set stoichiometrically or substoichiometrically. With this measure, graphite precipitations in the sintered material are prevented or minimized due to the over-stoichiometric carbon content.
• the inventors have recognized that such inclusions have an adverse effect on the breaking strength of the sintered carbide material.
• the proportion of carbon in the sintered carbide material is in the range between:
• 0.012*binder content by weight preferably in the range between:
• the proportion of Mo and/or Nb and/or Ti and/or Ta and/or Cr and/or V in the binder phase is ⁇ 15 at%.
• the elements mentioned above basically form carbides.
• Material composition is selected in such a way that these elements, corresponding to the solubility product and their affinity for carbon, are dissolved in small amounts in the intermetallic binder phase and they can thus be incorporated into the crystal lattice of the intermetallic phase material and/or be dissolved in the metallic binder phase.
• a cemented carbide material is desired that has a high toughness of the binder phase, then the proportion of the carbide form should be kept small. The materials should then be present in a total proportion of 15 at%. Provision can advantageously be made for the coercive field strength H CM of the sintered carbide material to be:
• the coercive field strength is usually used to indirectly determine the average grain size of the WC for a given binder content.
• the intermetallic phase material brings about a significant increase in the coercive field strength.
• the coercive field strength can thus be evaluated indirectly as a measure of the strengthening of the binder phase as a result of the embedded intermetallic phase material.
• the higher the coercivity the larger the total interface between metallic binder material, intermetallic phase material and WC.
• a high number of precipitated intermetallic phase material leads to a good support of the individual crystals of the intermetallic phase material against each other in the binder phase, especially at high temperatures (especially at high tool application temperatures).
• Coercive field strengths of the sintered carbide material H CM [kA/m] > (1.5 + 0.04*B) + (12.5- 0.5*B)/D + 4 [kA/m] can primarily be used, for the wear protection applications mentioned above, for example for wear plating.
• Coercive field strengths of the cemented carbide material preferably H CM [kA/m] > (1.5 + 0.04*B) + (12.5-0.5*B)/D + 6 [kA/m] can primarily be used , for the demanding tillage tools mentioned above.
• Coercive field strengths of the cemented carbide material preferably H CM [kA/m] > (1.5 + 0.04*B) + (12.5-0.5*B)/D + 10 [kA/m] can primarily be used , for the high-performance tools mentioned above.
• the coercive field strength of the sintered carbide material is 20% higher than the coercive field strength of a hard metal body that has the same composition and WC grain size as the sintered carbide material, with the binder phase consisting solely of metallic binder is formed; however, this has no intermetallic phase material.
• a cemented carbide body having the same composition is therefore a cemented carbide body with 70-95% by weight of tungsten carbide in dispersed form and a binder phase, the binder phase having metallic binder material without intermetallic phase material, the proportion of metallic binder material in the sintered carbide material is 5-30% by weight and the binder material otherwise has the same or approximately the same composition as the binder material of the sintered carbide material according to the invention.
• a sintered carbide material according to the invention can be named in this context, which has tungsten carbide in dispersed form and a cobalt binder as the hard material.
• the coercivity indirectly indicates the content/fraction of intermetallic phase material in the binder phase.
• the degree of reinforcement of the binder phase is indirectly indicated with the coercive field strength.
• the cemented carbide material can be designed in such a way that the hot compressive strength of the cemented carbide material is > 1650 [MPa] at a temperature of 800 °C and a strain rate of 0.001 [1/s] and/or that the hot compressive strength of the cemented carbide material at a temperature of 800 °C and a strain rate of 0.01 [1/s] > 1600 [MPa] (measurement for a cylindrical specimen with a diameter of 8 mm and a height of 12 mm).
• a sintered carbide material in particular cutting tips for road milling tools, are manufactured in which the proportion of metallic binder material in the binder phase is 5-7% by weight and the proportion of WC in the range of 93-95% by weight, with WC preferably being used here in coarse grain form with an average particle size in the range between 2- 5pm available.
• the advantageous effects described above are particularly pronounced in the case of coarse-grain hard metal.
• the dispersed tungsten carbide in the sintered carbide material is in grain form with an average particle diameter, measured according to DIN ISO 4499 Part 2, in the range between 1 and 15 ⁇ m, preferably in the range between 1.3 and 10 pm, particularly preferably in the range between 1.3 and 2.5 pm or in the range between 2.5 and 6 pm.
• the intermetallic phase (M,Y) 3 (AI,X) has a crystal structure L1 2 (space group 221) according to ICSD (Inorganic Crystal Structure Database), then there is a microstructure in the binder phase in which the Distribute crystals of the intermetallic phases evenly and support each other effectively in the metallic binder material when the sintered carbide body is subjected to heavy loads.
• ICSD Inorganic Crystal Structure Database
• the intermetallic phase material has a maximum size of 1500 nm, preferably a maximum size of 1000 nm.
• the sintered carbide material is free or as free as possible of eta phase and/or Al 2 O 3 .
• the inventors have recognized that the maximum proportion of the eta phase or the maximum proportion of Al 2 03 is a maximum of 0.6% by volume based on the total cemented carbide material should be. If both substances are present in the sintered carbide material, it is advantageous if the sum of eta phase material and Al2O3. is a maximum of 0.6% by volume.
• the particle size of Al2O3 and/or the eta phase material is advantageously a maximum of 5 times the mean WC grain size, with the mean WC grain size and the particle size of Al2O3 and/or the eta phase material being determined using the line intersection method (according to DIN ISO 4499 part 2) can be determined.
• the toughness of the sintered carbide material can be negatively influenced by the eta phase or Al 2 O3. With higher eta phase proportions, the sintered carbide material is only conditionally suitable for use in demanding tillage tools. The same also applies to Al 2 O3.
• the cemented carbide material may be a hard metal with a reinforced binder phase. This strengthening occurs through the precipitation of intermetallic phase material during cooling in the sintering process.
• a nominal composition of 70-95% by weight of WC, 1-28% by weight of metallic binder and 1-28% by weight of intermetallic phase can be selected when the raw materials are weighed.
• the metallic binder can contain the elements Co and optionally Fe and/or other components.
• the intermetallic phase is Ni 3 AI when weighed.
• sintered carbide material can also be such that the binder phase has the following chemical element composition:
• the proportion of oxygen in the binder phase is ⁇ 2% by weight, preferably ⁇ 1.5% by weight.
• the inventors have recognized that it is advantageous if there is no Al 2 O 3 in the binder phase or if Al 2 O 3 is only present in very small amounts. This material reduces the ductility or toughness of the binder and the cemented carbide material becomes more brittle. Thus, Al 2 O 3 weakens the binder phase and thus the strength of the sintered carbide material. If the level of oxygen in the binder phase is minimized as suggested, the formation of this species will be prevented or minimized.
• Binder components for example W and/or C, particularly preferably Ni>40% by weight, Al>6.5% by weight, remainder Co and dissolved binder components, for example W and/or C, it being possible in particular to provide that the ratio of Mass fractions Al to Ni > 0.10.
• WC powders of different grain sizes can be used as starting materials for the production of the powder mixture, in particular coarse-grain WC with a particle size FSSS > 25 pm.
• the starting powder for the binder phase is extra-fine cobalt powder (FSSS 1.3 pm) and nickel-aluminum powder, for example Ni-13Al powder with an aluminum content of approx. 13.3% by weight.
• the particle size of the Ni-Al powder is FSSS ⁇ 70 ⁇ m, preferably less than FSSS 45 ⁇ m.
• W metal powder (FSSS ⁇ 2pm) and lamp black are used to set and adjust a specific carbon content.
• alloy the binder phase with alloying elements such as Ti, Ta, Mo, Nb, V, Cr, their carbide powder or their W-containing mixed carbides with particle sizes ⁇ 3 pm are used.
• the powder mixture is produced according to the state of the art by wet grinding, preferably in a ball mill fitted with hard metal balls. Ethanol and hexane are used as grinding media. Other possible grinding media would be acetone or aqueous media with suitable inhibitors.
• the grinding parameters (duration, ratio of grinding balls to material to be ground, grinding medium) and the ratio of WC to Ni-Al powder are based on the WC grain size to be set in the sintered carbide material.
• pre-grinding VM If the alloy adjustment and the addition of the pressing aid have not already been carried out in the first grinding step (pre-grinding VM), this can also be done in the second step.
• the slip obtained during wet grinding is dried according to the state of the art and converted into a powder ready for pressing. This is preferably done by the process of spray drying.
• Shaping is preferably done directly, by axial pressing on mechanical, hydraulic or electromechanical presses.
• Sintering takes place between 1350 and 1550 °C in a vacuum, preferably in industrial sinter-HIP furnaces, in which, following liquid-phase sintering, an overpressure is created by means of an inert gas inlet, with any residual porosity being able to be eliminated.
• FIGS. 2 and 3 Two different sintered carbide materials according to the invention, in the form of flart metals, are illustrated in FIGS. 2 and 3 on the basis of such scanning electron microscope images.
• the binder phase of such a flart metal can be clearly seen, in which the intermetallic phase material (lighter phase) 10 and the metallic binder material 30 (dark) can be seen.
• the WC grains 20 are connected to one another via the binder phase.
• the crystals of the intermetallic phase material (M,Y) 3 (AI,X) have a crystal structure L12 (space group 221) according to ICSD (Inorganic Crystal Structure Database).
• the (M,Y) 3 (Al,X) content in the binder phase is >40% and the carbon balance is adjusted to be stoichiometric or substoichiometric.
• the amount of alloy that can be used depends on the respective solubility product of the metal carbides. Even if these seem negligible in terms of their magnitude, there are surprisingly clear effects that cannot be attributed to a grain-refining effect.
• the proportion of intermetallic phase material in the binder can be reduced and even be below 40%. Furthermore, in the presence of Ti or Ta, for example, the carbon balance no longer has to be substoichiometric, because these elements take over the role of tungsten as a stabilizer.
• Both measured variables are also determined for the characterization of the sintered carbide material according to the invention on a Koerzimat® 1.097 from Förster.
• Another parameter for characterizing the material is the density, which is determined by weighing according to the Archimedean principle.
• the hardness of the material is determined according to the standard applicable to hard metals on metallographically prepared polished samples.
• the hardness test according to Vickers HV10 with a test load of 10kp is preferably used (ISO 3878)
• the porosity of the sintered material (standard DIN-ISO 4499-4) and aluminum oxide particles are also determined and assessed using a light microscope on polished samples. Comparison images for A and B porosity can be used to estimate the volume percentage of aluminum oxide in the structure, with A08 and B08 approximately corresponding to a volume percentage of 0.6 volume percent. For light microscopic examination of the eta phase, this is etched with Murakami solution in accordance with the standard (DIN-ISO 4499-4). The average WC grain size is determined according to DIN ISO 4499-2.
• REM scanning electron microscope
• the proportions of the intermetallic phase in the binder and the maximum size of the separated particles are also determined using SEM images, but using an in-lense BSE detector. For this purpose, recordings are made at several points on the sample and the evaluation is carried out on a representative section by means of image processing and determination of the surface areas through tonal value delimitation.
• Example 2 Example 3
• Example 4 6-50 Ti 8.5-40 15-50 6-50 C-S 6-50
• Example 5 Example 6
• Example 8 Example 9

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