US20090018010A1 - Metal Borides - Google Patents

Metal Borides Download PDF

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US20090018010A1
US20090018010A1 US12/158,486 US15848606A US2009018010A1 US 20090018010 A1 US20090018010 A1 US 20090018010A1 US 15848606 A US15848606 A US 15848606A US 2009018010 A1 US2009018010 A1 US 2009018010A1
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boride
particles
metal
reaction
alkali
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Frank Schrumpf
Wolfgang Kiliani
Stefan Frassle
Thomas Schmidt
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HC Starck GmbH
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HC Starck GmbH
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Assigned to H. C. STARCK GMBH reassignment H. C. STARCK GMBH ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: FRAESSLE, STEFAN, KILIANI, WOLFGANG, SCHMIDT, THOMAS, SCHRUMPF, FRANK
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    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
    • C01B35/00—Boron; Compounds thereof
    • C01B35/02—Boron; Borides
    • C01B35/04—Metal borides
    • 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
    • C22C29/14—Alloys based on carbides, oxides, nitrides, borides, or silicides, e.g. cermets, or other metal compounds, e.g. oxynitrides, sulfides based on borides
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C24/00—Coating starting from inorganic powder
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C24/00—Coating starting from inorganic powder
    • C23C24/02—Coating starting from inorganic powder by application of pressure only
    • C23C24/04—Impact or kinetic deposition of particles
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
    • C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
    • C23C4/06—Metallic material
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/12—All metal or with adjacent metals
    • Y10T428/12014—All metal or with adjacent metals having metal particles
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
    • Y10T428/2982—Particulate matter [e.g., sphere, flake, etc.]

Definitions

  • the present invention relates to borides of metals of transition group four having a high content of monocrystalline, coarse powder particles with a volume of >1.5* 10 ⁇ 3 mm 3 , the surfaces of the particles being smooth and glossy and the corners and edges of the particles being rounded.
  • Ceramics materials have been used for a long time to manufacture wear-resistant machine or apparatus parts.
  • Pipes or elbows, stirring devices, stirrer vessels, flow breakers, nozzles, balls in valves, punching, milling or cutting tools, sifter wheels or deflectors in mills are often manufactured entirely of ceramics or covered with ceramics tiles in order to extend the useful life of the parts in question.
  • the nature of the radiographic phases and the form of the crystals are also relevant to the physical properties of the structural or covering component to be manufactured.
  • the hardness and strength of a material are essentially determined by the possibilities that a crack which forms has of penetrating into the particles and propagating.
  • One method of suppressing crack propagation is to produce the ceramics component from a large number of extremely fine crystals. As a result, a crack that forms is able to propagate over only a very short distance before it reaches a phase boundary and is accordingly prevented from propagating further.
  • This method is carried out in the hard metal industry, for example, where particularly high hardnesses and strengths are achieved using very fine tungsten carbide having particle sizes below 1 ⁇ m, in particular below 0.5 ⁇ m, with cobalt as binder.
  • the preparation of monocrystalline particles by crystal growth has the additional advantage that, with controlled growth, smooth surfaces are usually formed which, with suitable process management, are largely free of defects. In comparison with polycrystalline-agglomerated particles or compared to glasses, such crystals exhibit more homogeneous surface structures. As a result of the smoother surface of the grown crystals, the number of superficial dislocations or other defects, which can act as starting points for cracks, is minimised.
  • the term “monocrystalline” within the scope of the present patent specification is not to be understood as meaning the usual properties of a “monocrystal”, such as “free of dislocations” or “untwinned”, which are conventional among experts in crystallography/mineralogy.
  • microcrystalline used here simply serves as a distinction with respect to particles “agglomerated from small crystals” or “obtained from a large cast block by breaking up and grinding”.
  • the term “monocrystalline” is accordingly to be understood as being a simplification of the description: “Particles which, starting from seed crystals, grow layer by layer in the reaction zone by the addition of material at atomic level and in the process lose specific surface area and accordingly surface energy.”
  • Polycrystalline agglomerated or glass-like particles are generally obtained when ceramics melts are cooled and the resulting pieces, which are of large volume, are processed by breaking up, grinding and sieving to form powders. Such powders are recognisable by the sharp corners and edges of the particles. These sharp corners and edges are disadvantageous because they constitute sites of high surface energy, which likewise means that breaking and crack formation occur more readily.
  • the ceramics hard material “cast tungsten carbide”, W 2 C/WC, constitutes a combination of the advantages of both the strategies mentioned above.
  • This material can be used in a finely crystalline modification which, owing to the fine crystals distributed in a feather-like manner, exhibits a high degree of hardness. This structure is obtained upon solidification from the melt.
  • a disadvantage of this material is the sharp corners and edges which occur after grinding and sieving. Particularly high wear resistance is achieved with this material when the particles additionally have a spherical outer shape. This is achieved in the case of spherical cast tungsten carbide by melting again for a very short time. The spherical form makes it more difficult for a crack induced by pressure or stress to form or penetrate into the particles.
  • TiB 2 is a ceramics material which almost achieves the hardness of diamond, has a melting temperature of about 2900° C. and is electrically conductive and extremely chemically resistant. On account of its electrical conductivity, sintered parts of TiB 2 can be processed by electroabrasive processes to form complex components. The chemical reaction passivity allows molten metals, such as copper, aluminium or zinc, to be handled in apparatuses made of TiB 2 .
  • TiB 2 is suitable as a conductive component in mixed ceramics together with boron nitride, in order to produce, for example, evaporator dishes for molten aluminium.
  • the high corrosion resistance, in conjunction with the electrical conductivity, is used advantageously in this application.
  • TiB 2 As a constituent of particularly resistant components of ceramics or cermets. Powders that are very fine and have mean particle sizes D 50 of a few micrometres, in some cases even in the nanometre range, are generally used here. Coarse TiB 2 grains can be used for electrode coatings or as a substitute for the carbon electrode in aluminium electrolysis, because TiB 2 is wetted by liquid aluminium and the electrical resistance of the cell can be reduced. This use is described in European Patent EP-A-0232223. The preparation of TiB 2 -containing composites for use in aluminium electrolysis cells is described, for example, in EP-A-0115702, EP-A-0308014 and WO 97/08114.
  • Titanium boride powder which has been prepared by breaking up, grinding and sieving cast titanium boride is available commercially.
  • the particles have a size of approximately from 150 ⁇ m to over 1 mm.
  • Microscope pictures clearly show the shell-like broken surface structure and the glass-like, sharp corners and edges of the particles ( FIG. 5 ).
  • the rough surface reduces the wear resistance of the ceramics for the reasons described above.
  • U.S. Pat. No. 5,087,592 describes a process in which a platelet-like TiB 2 can be prepared from TiO 2 , carbon and B 2 O 3 at temperatures of from 1600 to 1700° C. with the addition of alkali carbonate.
  • the product consists of hexagonal platelets having a diameter of from 5 to 30 ⁇ m. Some of the platelets have sintered together to form larger agglomerates. These agglomerates are relatively soft, however, and, as is to be expected, break up relatively easily, for example when ground in a jet mill. Virtually no particles having sizes over 80 ⁇ m are present in the powder mixture.
  • the object of the invention was to provide borides of the metals of transition group four (IVb) of the periodic table of the elements, which borides are in the form of a coarsely crystalline powder having smooth surfaces and rounded edges.
  • a further object of the invention was, therefore, to provide a process for the production of such materials.
  • the objects of the present invention have been achieved by the provision of borides of metals of transition group four of the periodic table, wherein at least 55 wt. % of the particles have a grain size of more than 106 ⁇ m, determined by sieve analysis according to ASTM B 214, and these particles consist of grown, monocrystalline grains.
  • the borides according to the present invention are obtained by a process for the preparation of a boride of metals of transition group four by reacting boron carbide with at least one oxide of a metal of transition group four in the presence of carbon, wherein the reaction is carried out in the presence of an alkali or alkaline earth salt having a high boiling point of at least 1800° C., boron carbide is used in excess, and the reaction is carried out at a temperature of more than 2000° C.
  • the object of producing, at very high temperatures, a reaction atmosphere which allows the resulting boride of a metal of transition group four of the periodic table (in particular TiB 2 ) to form coarse crystals by Ostwald ripening was achieved by bringing the temperature of the reaction mixture close to the melting point of the boride of a metal of transition group four of the periodic table.
  • At least 40 wt. %, but advantageously up to 100 wt. %, in particular at least 55 wt. %, or from 50 wt. % to 90 wt. % or from 60 wt. % to 70 wt. %, of the particles of the boride according to the invention have a grain size of more than 106 ⁇ m.
  • the grain size is determined by sieve analysis according to ASTM B 214. According to the invention, it is precisely these particles that must consist of grown, monocrystalline grains and may not consist of agglomerates of smaller individual grains, which are also referred to as “raspberries” on account of their raspberry-like appearance in microscopy.
  • the proportion of raspberries according to the invention is advantageously less than 15%, or less than 10%. These raspberries occur in particular in the sieve fraction greater than 106 ⁇ m and consist of agglomerated primary crystals having a size of from 2 ⁇ m to 30 ⁇ m.
  • less than 10% of these particles consist of raspberry-like agglomerated primary crystals having a size of from 2 ⁇ m to 30 ⁇ m.
  • Metals of transition group four of the periodic table of the elements are understood as being titanium, zirconium, hafnium or mixtures thereof.
  • the borides of these metals that is to say TiB 2 , ZrB 2 , HfB 2 , can be obtained with the described properties. If a mixture of at least two oxides of different metals is used in the process according to the invention, then substitution mixed crystals can be obtained, the ratio of the metals to one another in the reaction mixture reflecting the ratios in the mixed crystal.
  • the formula for the resulting boride is then Ti X Zr Y Hf 1-X-Y B 2 , wherein X and Y are less than 1 and the sum of all the metals is always 1.
  • TiB 2 and ZrB 2 can advantageously be obtained according to the invention.
  • the mean grain size of the sieve analysis according to ROTAP ASTM B 214 is from 100 ⁇ m to 500 ⁇ m or from 200 ⁇ m to 355 ⁇ m.
  • the monocrystalline boride grains according to the invention can readily be distinguished by microscopy from conventional borides having sharp edges and a shell-like break, and can also readily be distinguished from the raspberries by their characteristic gloss in incident light, smooth surfaces and round corners and edges.
  • FIG. 4 shows a TiB 2 according to the invention.
  • FIG. 5 shows a commercially available TiB 2 according to the prior art.
  • the borides according to the invention have a particle size distribution in which the D 10 value is from 2 ⁇ m to 50 ⁇ m, in particular from 10 ⁇ m to 35 ⁇ m or from 20 ⁇ m to 50 ⁇ m or from 30 ⁇ m to 45 ⁇ m; the D 50 value is from 4 ⁇ m to 300 ⁇ m, in particular from 200 ⁇ m to 300 ⁇ m or from 140 ⁇ m to 240 ⁇ m; the D 90 value is from 8 ⁇ m to 750 ⁇ m, in particular from 250 ⁇ m to 650 ⁇ m or from 300 to 600 ⁇ m or from 370 ⁇ m to 580 ⁇ m.
  • the process according to the invention is carried out at a temperature of approximately 2000° C. or more, advantageously at from approximately 2100° C. to approximately 2750° C., in particular at from approximately 2200° C. to 2650° C. or at from approximately 2400° C. to approximately 2600° C. or from approximately 2300° C. to approximately 2500° C.
  • the temperature measurement is carried out by measuring the temperature of the surface of the reaction mixture through the waste gas opening in the lid of the crucible using a pyrometer, an emission factor of from approximately 0.3 to approximately 0.5 being expedient.
  • the described temperatures were measured by means of a pyrometer at the surface of the reaction mixture and with an emission factor of 0.37.
  • an alkali or alkaline earth metal salt is added during the process, which salt must not evaporate to an appreciable degree before or during the reaction. Therefore, this salt or salt mixture must have a boiling point of at least approximately 1800° C., advantageously at least approximately 1900° C., in particular from 2100° C. to 2750° C. or from 2200 to 2650° C. or from 2400 to 2600° C. or from 2300 to 2500° C. Oxides, hydroxides or carbonates of alkali or alkaline earth metals which have a sufficiently high boiling point are advantageous.
  • Sodium oxide which is used in U.S. Pat. No. 5,087,592, is poorly suitable owing to its boiling point of only about 1270° C.
  • lithium oxide (boiling point>2100° C.), magnesium oxide (boiling point>3500° C.), calcium oxide (boiling point 2850° C.), calcium hydroxide and calcium carbonate in particular are highly suitable.
  • the alkali or alkaline earth metal salt reacts predominantly to form the borate, for example CaBO 3 , which becomes concentrated in the form of a liquid phase at the grain boundaries of the intermediate phase between the monoxide of the metal of transition group four of the periodic table and the borate of the metal of transition group four of the periodic table (e.g. TiO and TiBO 3 ) and accelerates significantly the gas phase transport of the reactants below the melting temperature of the boride of the metal of transition group four of the periodic table.
  • a purification procedure for the growing boride of the metal of transition group four similar to zone refining takes place at the phase boundary.
  • crystal growth is accelerated at the temperatures used in the process according to the invention, so that the proportion of crystals having a particle volume greater than 1.5*10 ⁇ 3 mm 3 in the unground reaction product can be increased to more than 50%.
  • the borides according to the invention have a low content of alkali or alkaline earth metal ions, which is less than 100 ppm, advantageously from 10 ppm to 90 ppm, in particular from 20 ppm to 50 ppm or from 30 ppm to 65 ppm.
  • the boiling point of the oxides must lie within the same range as the above-mentioned ranges for the boiling points of the salts used.
  • the alkali or alkaline earth metal salt will be present in the reaction mixture in amounts of generally 1 wt. % or less, such as, for example, from 0.025 wt. % to 0.25 wt. %. Based on the use of calcium salts, amounts of from 0.03 wt. % to 0.1 wt. %, but also a calcium content of from 300 ppm to 900 ppm, yield good results.
  • the reaction is additionally carried out in the presence of carbon, because the carbon content of the boron carbide is not sufficient to reduce the oxide of the metal of transition group four of the periodic table of the elements.
  • the carbon can generally be used in any commercially available form which has the necessary purity and particle size in order to be mixed with the other reactants and reacted under the reaction conditions. Examples which may be mentioned here include graphite, carbon black or coal dust. It is advantageous to use, for example, flame black, which has low heavy metal contents of each less than 10 ppm, which is advantageous.
  • B 2 O 3 or B(OH) 3 can be present in the reaction mixture in order to facilitate the start of the reaction.
  • B 2 O 3 or B(OH) 3 can be present in the reaction mixture in order to facilitate the start of the reaction.
  • B 2 O 3 can be added.
  • B(OH) 3 can also be used.
  • oxide of a metal of transition group four of the periodic table of the elements there can be used in principle any obtainable material, that is to say any oxide of titanium, zirconium or hafnium, in particular titanium dioxide or zirconium dioxide.
  • These generally have BET surface areas of from 0.1 m 2 /g to 8 m 2 /g, in particular from 1 m 2 /g to 6 m 2 /g or from 2 m 2 /g to 5 m 2 /g or from 3 m 2 /g to 4 m 2 /g.
  • reaction time is generally between 4 and 36 hours, in particular from 5 hours to 12 hours, or from 14 to 24 hours or from 16 to 22 hours or from 20 to 26 hours.
  • the borides according to the invention are particularly insensitive to mechanical, abrasive or impact stress, so that fragmentation or the breaking off of very small particles are rarely observed. Ceramics or cermets that comprise such borides according to the invention are therefore particularly wear- and impact-resistant.
  • the present invention accordingly relates also to the use of borides according to the invention, in admixture with a metal binder component, in the production of cermets by hot pressing, high-temperature isostatic pressing or sintering.
  • the present invention relates further to the use of a boride according to the invention in the production of wettable powders for surface coating by plasma spraying, HVOF spraying or cold gas spraying, wherein the titanium boride is bonded to the surface in the form of a ceramics hard material in a metal binder component and, owing to its particularly smooth crystal surface and its particularly round corners and edges, brings about particularly preferred frictional, sliding and wear properties of the coating.
  • the present invention relates in addition to a surface coating comprising a boride according to the invention. Such coatings can be applied by means of thermal spraying processes, such as, for example, plasma spraying, HVOF spraying or cold gas spraying, for which corresponding wettable powders are used.
  • the present invention therefore relates also to wettable powders comprising a boride according to the invention and at least one metal powder as binder component.
  • the present invention relates to cermets comprising a boride according to the invention, in particular comprising a titanium boride or zirconium boride according to the invention, in particular a titanium boride.
  • Suitable metal binders are binder components comprising iron, copper, chromium, nickel, aluminium, yttrium, vanadium, rhenium or their alloys with one another or with other metals, such as, for example, steels, such as, for example, stainless steel, V4A steel, V2A steel, alloys known as MCrAlY or alloys marketed under the trade names Inconel® and Hastalloy®.
  • a specific embodiment of the invention relates to a compound of formula Ti X Zr Y Hf 1-X-Y B 2 , wherein X and Y are less than 1 and the sum of all the metals is always 1, wherein from 50 wt. % to 100 wt. % of the particles have a grain size of more than 106 ⁇ m, determined by sieve analysis according to ASTM B 214, and these particles consist of grown, monocrystalline grains;
  • a further embodiment of the invention relates to zirconium boride or titanium boride, wherein the proportion of crystals having a particle volume greater than 1.5*10 ⁇ 3 mm 3 in the unground reaction product is more than 50%;
  • the particles have a grain size of more than 106 ⁇ m, determined by sieve analysis according to ASTM B 214, and these particles consist of grown, monocrystalline grains; and/or the proportion of raspberries is advantageously less than 15% according to the invention.
  • a further specific embodiment of the invention relates to zirconium boride or titanium boride
  • the proportion of crystals having a particle volume greater than 1.5*10 ⁇ 3 mm 3 in the unground reaction product is more than 50%; or from 50 wt. % to 100 wt. % of the particles have a grain size of more than 106 ⁇ m, determined by sieve analysis according to ASTM B 214, and these particles consist of grown, monocrystalline grains; and/or the particle size distribution exhibits a D 10 value of from 20 ⁇ m to 250 ⁇ m, a D 50 value of from 40 ⁇ m to 400 ⁇ m and a D 90 value of from 80 ⁇ m to 750 ⁇ m.
  • a further specific embodiment of the invention relates to zirconium boride or titanium boride
  • the proportion of crystals having a particle volume greater than 1.5*10 ⁇ 3 mm 3 in the unground reaction product is more than 50%; or from 50 wt. % to 100 wt. % of the particles have a grain size of more than 106 ⁇ m, determined by sieve analysis according to ASTM B 214, and these particles consist of grown, monocrystalline grains; and/or the particle size distribution exhibits a D 10 value of from 80 ⁇ m to 200 ⁇ m, a D 50 value of from 100 ⁇ m to 300 ⁇ m and a D 90 value of from 250 ⁇ m to 500 ⁇ m; or the particle size distribution exhibits a D 10 value of from 120 ⁇ m to 170 ⁇ m, a D 50 value of from 160 ⁇ m to 260 ⁇ m and a D 90 value of from 400 ⁇ m to 600 ⁇ m; or the particle size distribution exhibits a D 10 value of from 140 ⁇ m to 200 ⁇ m, a D 50 value of from 200 ⁇ m to 280 ⁇ m and a
  • a further specific embodiment of the invention relates to zirconium boride or titanium boride
  • the proportion of crystals having a particle volume greater than 1.5*10 ⁇ 3 mm 3 in the unground reaction product is more than 50%; or from 50 wt. % to 100 wt. % of the particles have a grain size of more than 106 ⁇ m, determined by sieve analysis according to ASTM B 214, and these particles consist of grown, monocrystalline grains; and/or the particle size distribution exhibits a D 10 value of from 80 ⁇ m to 200 ⁇ m, a D 50 value of from 100 ⁇ m to 300 ⁇ m and a D 90 value of from 250 ⁇ m to 500 ⁇ m; or the particle size distribution exhibits a D 10 value of from 120 ⁇ m to 170 ⁇ m, a D 50 value of from 160 ⁇ m to 260 ⁇ m and a D 90 value of from 400 ⁇ m to 600 ⁇ m; or the particle size distribution exhibits a D 10 value of from 140 ⁇ m to 200 ⁇ m, a D 50 value of from 200 ⁇ m to 280 ⁇ m and a
  • a further specific embodiment of the invention relates to a process for the preparation of a boride of metals of transition group four by reacting boron carbide with at least one oxide of a metal of transition group four in the presence of carbon, wherein the reaction is carried out in the presence of an alkali or alkaline earth metal salt having a high boiling point of at least 1800° C., boron carbide is used in excess, and the reaction is carried out at a temperature of more than 2000° C.,
  • a further specific embodiment of the invention relates to a process for the preparation of a boride of metals of transition group four, comprising the steps
  • a further specific embodiment of the invention relates to a process for the preparation of a boride of metals of transition group four, comprising the steps
  • a further specific embodiment of the invention relates to a process for the preparation of a boride of metals of transition group four, comprising the steps
  • a further specific embodiment of the invention relates to a cermet obtained from a mixture comprising a zirconium boride or titanium boride,
  • the proportion of crystals having a particle volume greater than 1.5*10 ⁇ 3 mm 3 in the unground reaction product is more than 50%; or from 50 wt. % to 100 wt. % of the particles have a grain size of more than 106 ⁇ m, determined by sieve analysis according to ASTM B 214, and these particles consist of grown, monocrystalline grains; and a metal binder comprising iron, copper, chromium, nickel, aluminium, yttrium, vanadium, rhenium or alloys thereof with one another or with other metals, which binder has a D 50 value of from 20 ⁇ m to 50 ⁇ m; or a metal binder comprising stainless steel, V4A steel, V2A steel, alloys known as MCrAlY or alloys marketed under the trade names Inconel® or Hastalloy®, which binder has a D 50 value of from 20 ⁇ m to 50 ⁇ m; and the ratio between the zirconium boride or titanium boride and the metal bin
  • the temperature measurement is carried out by measuring the temperature of the surface of the reaction mixture through the waste gas opening in the lid of the crucible using a pyrometer, an emission factor of from approximately 0.3 to approximately 0.5 being expedient.
  • the described temperatures were measured at the surface of the reaction mixture using a pyrometer and with an emission factor of 0.37.
  • FIG. 1 shows grains of this product at 500 times magnification.
  • the product has the following grain size distribution: D 10 : 2.0 ⁇ m; D 50 : 4.75 ⁇ m; D 90 : 8.88 ⁇ m.
  • the reaction is complete.
  • the resulting sintered block is worked up by breaking up, grinding and sieving. Approximately 218 g of TiB 2 are obtained.
  • the yield in the case of the B 2 O 3 route in a MF furnace is markedly lower and accordingly the specific costs are higher than with the B 4 C process.
  • a fine product is obtained, the crystals of which are approximately from 1 to 5 ⁇ m in size.
  • the resulting sintered block is worked up by breaking up, grinding and sieving. From 550 to 600 g of TiB 2 are obtained. It is noticeable that more than half of the coarse particles consist of raspberry-like agglomerated primary grains. The size of the fine primary grains is in the range of from approximately 2 to 30 ⁇ m. The grown monocrystalline grains of the coarse fraction exhibit smooth surfaces and rounded corners and edges.
  • FIG. 2 shows grains and raspberries of this product at 20 times magnification. The product has the following grain size distribution: 53.8 wt. % ⁇ 106 ⁇ m; 33.8 wt. % 106-250 ⁇ m; 12.4 wt. %>250 ⁇ m.
  • the resulting sintered block is worked up by breaking up, grinding and sieving. From approximately 550 to 600 g of TiB 2 are obtained. The yield of grains>106 ⁇ m is 84.6%. The calcium content of the product was 38 ppm. The yield of grains 106-800 ⁇ m in the total mass is 73.4%. It is noticeable that almost none of the coarse particles consist of raspberry-like agglomerated fine primary grains, but almost all are monocrystalline grains having smooth surfaces and rounded corners and edges. Grains of the 200-800 ⁇ m fraction are shown in FIG. 3 . The product has the following grain size distribution: 13.4 wt. % ⁇ 106 ⁇ m; 30.2 wt. % 106-250 ⁇ m; 56.4 wt. %>250 ⁇ m.
  • the mixture is homogenised in a mixer and transferred to a graphite crucible.
  • the crucible is closed with a graphite lid having a hole.
  • the reaction is heated to from approximately 2400 to 2500° C. (measured through the opening in the lid using a pyrometer) with the increased heating capacity of about 50 KW in the medium frequency field.
  • the resulting sintered block is worked up by breaking up, grinding and sieving. From approximately 560 to 600 g of TiB 2 are obtained. The yield of grains>250 ⁇ m is 52.4%. The yield of grains 106-800 ⁇ m in the total mass is 67.8%. It is noticeable that almost none of the coarse particles consist of raspberry-like agglomerated fine primary grains, but almost all are monocrystalline grains with smooth surfaces and rounded corners and edges. Grains of the 106-800 ⁇ m fraction are shown in FIG. 4 . The glossy, smooth surface and the round corners and edges are very clearly visible. The product has the following grain size distribution, measured by laser diffraction using a Microtrac X100: D 10 : 116 ⁇ m; D 50 ; 262 ⁇ m; D 90 : 483 ⁇ m.
  • Cermet platelets on which wear resistance studies can be carried out are produced by, for example, coarse borides being sintered with metallic binders. Fine boride particles can be added in addition. These fine particles fill packing gaps between the coarse boride particles and thereby increase the total content of wear-resistant constituents in the final cermet. Cermets of this kind are also described in the patent specification WO2004/104242.
  • the mixture compositions are recited below.
  • Each of the four mixtures is sintered in a graphite matrix in a hot press at 250 kp/cm 2 and 1250° C. under argon to form round cermet discs about 5 mm in thickness.
  • Table 1 gives an overview of the powder mixtures used for producing the cermet platelets and of the resulting cermets.
  • the round discs obtained by hot pressing are cut with a high-pressure water jet saw using the abrasive cutting process (450 g/min Indian granite, 80 mesh) at a pressure of 3500 bar, nozzle diameter 0.3 mm, forward feed speed 20-25 mm/min, into rectangular platelets 50*25 mm 2 in size. It emerged that the platelets of the cermet of Example 5 could not be cut through under these conditions even at a reduced forward feed speed of 15 mm/min. This cermet was therefore cut using a diamond severing disc.
  • abrasive cutting process 450 g/min Indian granite, 80 mesh
  • the rectangular platelets are subjected to a wear test on a friction roller test rig in accordance with the ASTM G65 A standard, where abrasion of the cermet platelets is determined in terms of milligrams of weight lost.
  • Comparison Example 4 utilizes a commercially available, coarser molten titanium boride in accordance with the prior art (ESK, Kempten, Grade M9).
  • the cermet according to Example 5 (containing titanium boride in accordance with Example 3 of the invention) has the least abrasion. Cutting with the water jet showed straightaway that the cermet according to Example 5 is extremely resistant. The disc could not be cut using the water jet. A diamond saw had to be used.
  • FIGS. 6 and 7 show the surfaces of the hot-pressed cermets according to Example 5 and Comparison Example 4. Cermets produced with titanium boride according to the invention are seen to have a particularly large fraction of surviving coarse TiB 2 crystals. Although the unsintered powder mixture of the comparative cermet platelet in accordance with Comparison Example 4 ( FIG. 7 ) likewise contains a third of coarse titanium boride, the hot-pressed sample is found to contain distinctly fewer of these particularly wear-resistant particles.
  • the molten, coarse titanium boride has a rough surface which, at the elevated temperatures of the sintering operation, is particularly ready to react with metals. As a result, the originally coarse crystals are partially or completely broken up and are no longer available for wear protection.
  • the extremely smooth surface of the titanium borides according to the invention offers an aggressive metal matrix only very little area to attack during sintering or hot pressing.

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US20080003125A1 (en) * 2006-06-30 2008-01-03 Peterson John R Erosion resistant cermet linings for oil & gas exploration, refining and petrochemical processing applications
CN113751711A (zh) * 2020-06-04 2021-12-07 河南领科材料有限公司 一种聚晶立方氮化硼复合片及制备方法

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US8598022B2 (en) 2009-10-27 2013-12-03 Advanced Technology Materials, Inc. Isotopically-enriched boron-containing compounds, and methods of making and using same
KR101902022B1 (ko) 2010-08-30 2018-09-27 엔테그리스, 아이엔씨. 고체 물질로부터 화합물 또는 그의 중간체를 제조하기 위한 장치 및 방법, 및 이러한 화합물과 중간체를 사용하는 방법
DE102010052555A1 (de) * 2010-11-25 2012-05-31 Mtu Aero Engines Gmbh Herstellung von Spritzpulvern zum Kaltgasspritzen
TWI583442B (zh) * 2011-10-10 2017-05-21 恩特葛瑞斯股份有限公司 Ｂ２ｆ４之製造程序
CN103754891B (zh) * 2014-01-09 2016-02-10 航天材料及工艺研究所 一种硼/碳热还原法低温制备硼化铪粉体的方法
KR101659334B1 (ko) 2014-12-07 2016-09-23 (주)엔티케이코퍼레이션 집진 영역 확장 구조의 환형 에어나이프
KR20160014758A (ko) 2016-01-25 2016-02-11 황창배 간섭 회피 구조를 가진 에어나이프
CN108349820B (zh) 2016-01-27 2021-11-30 第一稀元素化学工业株式会社 硼化锆及其制备方法
ES2965904T3 (es) * 2017-05-11 2024-04-17 Hyperion Materials & Tech Sweden Ab Un cuerpo de borocarburo de wolframio y hierro para aplicaciones de blindaje nuclear

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US7842139B2 (en) * 2006-06-30 2010-11-30 Exxonmobil Research And Engineering Company Erosion resistant cermet linings for oil and gas exploration, refining and petrochemical processing applications
CN113751711A (zh) * 2020-06-04 2021-12-07 河南领科材料有限公司 一种聚晶立方氮化硼复合片及制备方法

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