EP3765428A1

EP3765428A1 - Sic-bound diamond hard material particles, porous component formed with sic-bound diamond particles, method of producing same and use thereof

Info

Publication number: EP3765428A1
Application number: EP19713380.4A
Authority: EP
Inventors: Björn Matthey; Steffen Kunze; Mathias Herrmann
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 2018-03-14
Filing date: 2019-03-14
Publication date: 2021-01-20
Also published as: CN112119051A; JP2021517546A; US20210002534A1; KR20200143390A; DE102018203882A1; JP7335885B2; WO2019175333A1; BR112020018495A2; RU2020132167A

Abstract

The invention relates to SiC-bound diamond hard material particles, a porous component formed with SiC-bound diamond particles, methods for producing same and the use thereof. Diamond hard material particles and components have a composition of 30 vol. % to 65 vol. % diamond, 70 vol. % to 35 vol. % SiC and 0 to 30 vol. % Si, and a component has a porosity in the range of 10% to 40%.

Description

The invention relates to SiC-bonded diamond hard particles, porous construction formed with SiC-bonded diamond particles, process for their preparation as well as their use.

Usually, the most diverse hard material particles are embedded alone or in the form of granules or in a material matrix, used for under different applications, in particular for a machining in the form of loops. Among others, diamond particles which are known to have a very high hardness are used as the hard material particles. Dia mant alone but may have disadvantages in various applications, which may be disadvantageous, for example, in thermal cycling or binding behavior in a matrix material. In addition, diamond particles can also chemically under certain environmental conditions decompose or dissolve from a matrix or a composite material.

It is therefore an object of the invention to provide granules or components available that have ver compared with pure granulated from diamond particles improved properties that can be adapted to specific applications.

According to the invention, this object is achieved with hard material particles having the features of claim 1, a component having the features of claim 14. Claim 4 defines a manufacturing method for hard material particles and claim 16 for components. Claim 23 relates to uses of hard material particles and components. Advantageous embodiments and Weiterbildun conditions can be realized with designated in subordinate claims characteristics.

With the invention, super hard abrasive materials of SiC bonded diamond can be provided.

The hard material particles according to the invention are formed from SiC bonded diamond and can be obtained in particle sizes between 20 pm and 5 mm. The hard material particles are formed with 30% by volume - 65% by volume of diamond, 70% by volume - 35% by volume of SiC and 0% by volume to 30% by volume of Si. Preferred are 40% by volume - 60% by volume of diamond 60% by volume - 40% by volume of SiC and 2% by volume to 20% by volume of Si.

The particle size distribution of the diamond particles may be multimodal to increase the packing density of interconnected diamond particles in hard particles.

Advantageous is a fine fraction which is 0.1 to 0.3 times the size of the diameter of a coarse diamond particle fraction and has a content of 5% by volume to 50% by volume of the coarse particle size fraction. Advantageously, 5% by volume to 30% by volume of the coarse particle size fraction should be used in a multimodal particle size fraction.

Here are diamond particles on surface areas in individual hard particles with the SiC formed during the thermal treatment and Si cohesively connected to each other.

In this case, and should not advantageous the entire surface areas of diamond particles with the reactively formed SiC cohesively miteinan be connected. As a result, quasi predetermined breaking points can be formed, which can lead to a break at sufficiently high mechanical load. For example, in a grinding process, diamond particles and / or regions of SiC can break out of the cohesive bond, which can advantageously have an effect during grinding.

The average particle size d ₅₀ of diamond particles in the material should be kept in the range 5 pm to 500 pm, preferably 5 pm-100 pm. The particle size distribution of the diamond particles in a hard material particle may be multimodal to increase the packing density. It is thus possible to use at least two different particle size fractions.

Particularly advantageous is a fine and a coarser particle size fraction of diamond particles, the finer particle size fraction should have 0.1 to 0.3 times the size of the diameter of the coarse particle size fraction and with a share of 5 vol .-% - 50 vol .-% of coarse

Particle size fraction may be contained in a hard material particles. Very particular advantageous are 5 vol .-% - 30 vol .-% of the coarse particle size fraction complied with.

In the preparation of the granules, the procedure is that a suspension in which diamond particles and an organic binder are contained, or Dia mantpartikel which are used with a suspension or a dispersion in which a orgasmic African binder is used. In the granulation and drying process, there is a partial or complete Beschich tion of diamond grains. As a result, these are held together as granules th.

In a thermal treatment in an oxygen-free atmosphere, it follows a pyrolysis in which components of the organic binder thermally decomposes and in the pyrolysis of the organic binder in situ formed ter carbon in a glassy form on surfaces of diamond particles off-. puts.

During this thermal treatment or in a subsequent two thermal treatment with added powdered silicon, a siliconization is carried out. The addition of the powdered silicon can be done before the siliconization.

With the carbon deposited on surfaces of diamond particles, silicon carbide is formed by chemical reaction, so that hard material particles containing 30% by volume - 65% by volume of diamond, 70% by volume - 35% by volume of SiC and 0 to 30 Vol .-% Si are formed can be obtained.

The resulting diamond granules should be mixed with powdered silicon and, if appropriate, in addition with particulate spacers so that the granules are not or only minimally destroyed and they at least partially separate the diamond particles. This simplifies or allows a separation of the resulting SiC-bonded diamond hard particles without intensive grinding or the like, which would lead to strong wear on aggregates.

The organic binder and / or its amount to which the diamond particles are coated or contained in the suspension should be selected so that the organic binder is used as carbon source in a proportion of between 1.5% by mass and 20% by mass Relative to the total mass of a set diamond particles is used. The SiC used for the binding of the diamond particles is obtained essentially from the chemical reaction of the carbon released during the pyrolysis with silicon. This improves the properties of the hard material particles thus obtained, as follows:

Increased thermal stability,

- Specifically adjustable fracture behavior of the hard particles, (If di amides containing larger amounts of catalyst (Fe, Ni) are used, then these are weakened internally and it can by the variation of the siliciding temperature between 1425 ° C and 1650 ° C, the Breaking the diamond particles under Anwendungsbedin conditions are controlled (higher temperature lead to breakage under lower load)

By extending the hold time during siliconization at temperatures> 1525 ° C, the incorporation of the diamond particles in the SiC matrix can be influenced. Higher temperatures for longer times lead to faster break-out of the diamond particles under severe tribological stress. When siliconizing at 1650 ° C and 20 min holding time, interfaces of non-diamond carbon are formed in a thickness of> 50 nm. This causes the diamond particles are released when the SiC bond is partially worn. With siliconization <= 1600 ° C and siliconizing times of <60 min, there is a firm involvement of the diamond particles, so that there is no falling out of the diamond particles, even if the hard SiC bond is partially worn. Integral Knoop hardnesses of> 40-45 GPa can be measured for such hard particles.

The associated reduced strength of the bond between the diamond particles and the SiC and the Si sometimes has a positive effect when the hard material particles are used in a grinding process.

In addition to bonding with the reactively formed SiC, the diamond particles in hard-material particles may additionally be bonded to Si in a material-bonded manner, which has not been reacted in a reactive manner. However, this free Si is typically separated from the diamond by an SiC layer thick to nm.

Advantageously, a maximum of 90%, more preferably 80% maximum of the surfaces of the diamond particles should be materially bonded to SiC and Si. For this purpose, the added amount and type of organic binder and silicon can be selected accordingly. The organic binder forms the main source of carbon for the reactive in situ formation of SiC. In addition, a superficial reaction of the diamond particles with the Si occurs during the infiltration to SiC. This ensures the solid chemical bonding of the diamond particles to the SiC. The carbon from the binder reduces the amount of reactive diamond and thus allows higher diamond contents to be achieved.

The reaction preferably leads to the formation of β-SiC. A granulate possibly mixed SiC (usually the low-cost a-SiC) can also be incorporated into the formed SiC matrix / network. However, this reduces the density of the diamond particles so that, as a rule, it does not bring any advantage over them. For special applications, in particular to reduce the price but you could add a-SiC.

The preparation of the hard material particles can by granulation with minimal amounts of organic binder and solvent content means

Dish granulator or e.g. in an Eirich mixer or by fluidized bed or spray granulation. It is also a pressing of the granules and then subsequent crushing possible. This can be higher

Diamond particle densities are achieved.

The organic binder, which is pyrolyzed in an inert atmosphere at 400 ° C - 1400 ° C, may result in a non-diamond content of 1.5% by mass to 20% by mass, based on the diamond content in the pyrolyzed state.

The particle size distribution of the individual silicided hard material particles can be determined by means of classification / comminution, e.g. refined by screening and adapted to the needs. Before classification, a mechanical separation can be carried out, for example with a jaw crusher.

As the organic binder which can be used in the invention may be an organic chemical compound or a mixture selected from polyvinyl alcohol, acetate, polyethylene glycol, a sugar, cellulose, and phenolic resins. The term binder is here used as a collective term for the ge used organic components, since the bond between the diamond particles in the granulated state is the main function. The organic components can also be found next to the actual binder,

Dispersing agents, wetting agents, plasticizers (e.g., PEG), defoaming agents.

Hard material particles are infiltrated with silicon. For this purpose, the granules with ore particles and the organic binder formed granules before or preferred after pyrolysis in the thermal treatment with Si powder having an average particle size d ₅₀ in the range of 5 pm - 1000 pm, preferably in the range 10 pm - 150 pm and in this range with a volume of 10 vol .-% - 200 vol. -% preferably 20 vol .-% - 100 vol.% Of the content of Dia mantpartikeln be added and mixed.

Preferably, the silicon powder should have a particle size which is between 5 pm and twice the particle size of the granules of the granules formed with diamond particles and the organic binder in order to ensure sufficient spacing between the individual granules. The distances are conducive to easy comminution after siliciding. The content of silicon should not exceed twice that which is necessary to carry out the reactive bond. Better is 1.5 times or even only 1.1 times.

The infiltration can be carried out in the thermal treatment, in which the Pyroly se is carried out, but also in a second subsequently performed th thermal treatment. In the further thermal treatment rule, a maximum temperature of 1650 ° C and FITS preferred should vacuum conditions are met.

It can also be used coarse silicon powder. In addition, however, a particle size fraction of fine silicon powder should be used in the range 5 pm - 20 pm with a volume of 10 vol .-% - 30 vol .-% of the SiC diamond granules. This finer fraction makes it possible, by the remaining porous oxide / SiC surface layers of the original Si grains, to easily singulate the SiC-bonded diamond hard-material particles.

To make the SiC bonded diamond hard particles easier after the

To be able to singulate siliconization, components can be admixed before the siliconization or pyrolysis as spacers, which are difficult to wet by Si, do not form an alloy with Si and do not react with Si. Such chemical elements or compounds can be used for coating in order to minimize a firm connection (sticking) of the granules to one another. For this purpose, chemical elements or compounds can be preferably selected from BN, Si ₃ N ₄ , AlN, Al ₂ 0 ₃ , Si0 ₂ , Zr0 ₂ and a nitride, carbide of the transition metals, in particular groups 4 and 5 of the periodic table (in particular of Ti, Zr, Hf, V, Nb).

This route is particularly effective when the Si necessary for the reaction bonding has already been added to the granules and does not have to be supplied from the outside to the granules during the siliconization.

Since SiC or SiC-Si0 ₂ sheaths can remain around the silicon particles, the silicated granulate streams can easily be comminuted and then classified (eg, jaw crusher, sieve, air classifier, etc.) when the Si particles have been mixed into the granules ,

The obtained SiC bonded hard material particles may still be agglomerated after the siliconization. Therefore, they should usually be mechanically comminuted and then classified (e.g., jaw crusher, ball mill, sieve,

Air classifier, etc.). By the measures described above, this goes without great abrasion and wear on the units.

Additionally, excess Si can be partially or completely dissolved out with alkaline solutions (e.g., 20% NaOH) at room temperature or elevated temperatures in the range of 60 ° C to boiling point. This too can be used to separate the hard material particles.

The resulting hard particles can be used as abrasives, but they can also be introduced as a hard material particles in other matrix materials and so novel with plastic, metal or ceramic gebun dene grinding wheels / discs are produced.

The SiC-bonded diamond hard material particles can be processed into grinding wheels, for example with a glass matrix or metal matrix.

The hard materials according to the invention have, in addition to the advantage of better grinding behavior, the advantage of greater thermal stability in comparison to pure diamond.

The introduction of the SiC bonded diamond hard material particles into a mat Rixwerkstoff can be done according to typical ceramic technologies. These hard material particles can also be added separately to a dried granulate before molding. However, they can also be supplied to the starting composition and then further processed with correspondingly common ceramic molding technologies, such as, for example, by granulation, pressing, slip casting, extrusion, injection molding, hot casting or by means of additive manufacturing processes.

Since the SiC bonded diamond hard material particles essentially consist of diamond and SiC, they have a different fracture behavior than pure diamond granules. Thereby, the grinding wheels, which can be formed with a fiction, contemporary granules, under certain conditions more effective than those formed with pure diamond.

The fracture behavior of the SiC bonded diamond hard material particles can be adjusted. In addition, different diamond qualities can be set to also adjust the fracture behavior of the hard particles.

By means of thermal treatment, the bond between diamond particles and SiC can be adjusted. When diamond particles containing larger residuals of catalyst (Fe, Ni) are used, they can be internally reduced and, by varying the siliciding temperature between 1425 ° C and 1650 ° C, breaking the diamonds under application conditions controlled (higher temperatures lead to breaking under a lower load).

By extending the hold time in the siliconization at temperatures> 1550 ° C, the involvement of the diamond particles in the SiC matrix can influence the who. Longer times and higher temperatures lead to faster break-out of the diamond particles under severe tribological stress. When siliconizing at 1650 ° C and holding for 20 minutes, non-diamond carbon interfaces may form in a thickness of> 50 nm. This causes the diamond particles to be released when the SiC bond is partially worn. With siliconization <= 1600 ° C and siliconizing times of <60 min, there is a solid involvement of the diamond particles, so that it no falling out of the diamond particles can come, even if the SiC bond is partially worn. Integral Knoop hardnesses of> 40 GPa - 45 GPa can be measured for such hard particles.

For certain grinding applications, SiC bonded diamond hard particles of defined shape are advantageous. By means of ceramic molding processes, in particular extrusion or casting or pressing, the particles can be brought into any desired shape, preferably spherical, cylindrical, prismatic, pyramidal, in particular by extrusion or by casting prior to siliconizing.

The hard material particles can also be used as an additive to other materials to increase the stiffness, hardness or wear resistance who the. This can e.g. in metals as particle reinforcement or in other materials intended to have anti-burglary function (e.g., concrete) or to provide extremely durable rough surfaces, for example to prevent wet slides in safety-related areas.

Through the siliconization, an agglomerate formed with diamond particles can be enclosed with SiC. As a result, an abrasive grain has a higher thermal stability or is much more stable when interacting with oxydic or metallic matrices. This improves the incorporation of hard particles in critical matrix materials, such as carbide, Al ₂ 0 ₃ , etc ..

Inside hollow hard material particles can by application of a suspension, in addition to diamond particles also an organic binder is contained, on silicon particles with a particle size in the range 50 pm - 150 pm or the use of a suspension in addition to diamond particles, organic binder also in the thermal treatment decomposing powdered poly merer material, preferably polyurethane is included and subsequent thermal treatment in which a pyrolysis and a reactive formation of SiC takes place, are produced. Polystyrene, polymethyl methacrylate, polyethylene or polypropylene or starch may also be added as a preferred polymeric material. Polymeric material should have a medium

Particle size d _{50 are added} in the range 30 pm to 100 pm before thermal treatment and pyrolyzed during the thermal treatment. Also, this form of hard material particles has advantageous properties in an application for grinding processing, as well as the strength of the cohesive connection between diamond particles and in particular the SiC and optionally with the Si is reduced. As a result, an improved erosion of diamond particles during grinding can be achieved, which is beneficial because of the formation of new cutting.

The effect is similar to the use of reduced surface areas where cohesive connections have been formed, as already described.

From SiC bonded diamond but also directly grinding wheels can be produced as porous components. Such components have a porosity in the range 10% to 40%, preferably between 10% and 30%, an average Po rengröße between 10 pm - 100 pm, preferably between 20 pm - 50pm. They consist of 30% by volume - 65% by volume of diamond 70% by volume - 35% by volume of SiC and 1% by volume to 30% by volume of Si, preferably 40% by volume - 60 % By volume of diamond, 60% by volume

40% by volume of SiC and 2% by volume to 20% by volume of Si, and the diamond particles contained have an average particle size in the range from 5 μm to 500 μm, preferably in the range from 30 μm to 100 μm, particularly preferably > 50 pm - 200 pm.

A material formed with the SiC bonded diamond particles may contain, for example, 20 vol .-% - 50 vol .-% of at least one soft phase, which primarily wears at tribological or abrasive stress and thus creates pores in the material can with a mean particle size of 10 pm

- 50 pm, preferably 15 pm - 30 pm or 10 pm - 20 pm be formed of hard material particles. This embodiment is particularly advantageous for SiC bonded diamond grinding wheels.

This soft phase (s), which has a lower mechanical strength in comparison to the diamond particles and the SiC, / may have non-diamond carbon, BN, Si ₃ N ₄ , which may also be sintered, Al ₂ 0 ₃ , or transitional alumina, dense or porous glass spheres, high melting silicide or boride (eg TiSi ₂ , MoSi ₂ , WSi ₂ , TiB ₂ , W ₂ B ₅ , WB ₂ , Zr0 ₂ ) with a variety of dopants, at least one other high melting oxide or silicate (eg MgO, talc, ...), at least one transition metal carbide or oxicarbide or nitride or boride in particular the group 4 and 5 of the Periodic Table (in particular of Ti, Zr, Hf, V, Nb). As a phase in this sense, a porosity can be considered as it can lead to the same result in the product.

Preferably, 20% by volume to 30% by volume of this phase (s) (apart from diamond, SiC and Si) can be contained in one material. ,

The production of a component can also be carried out so that diamond particles with SiC, an organic binder and particles of an organic material, be preferentially powdered plastic as pore formers, in particular polystyrene, polymethyl methacrylate, polyurethane, polyethylene or polypropylene or starch preferably having an average particle size d ₅₀ be mixed in the range 30 pm to 100 pm before the thermal treatment and formed by a molding process. This shaped body is then subjected to a thermal treatment in an oxygen-free atmosphere in which a pyrolysis of the organic constituents takes place and in the pyrolysis of the organic binder formed in situ carbon deposits in a glassy form on surfaces of diamond particles. During this thermal treatment or in a subsequent second thermal treatment with externally supplied preferably pulverulent silicon, a siliconization is carried out. In this case, with the carbon deposited on surfaces of diamond particles and the diamond by chemical reaction silicon carbide is formed, so that

the component material has a composition of 30% by volume - 65% by volume of diamond, 70% by volume - 35% by volume of SiC and 0 to 30% by volume of Si and a porosity in the range from 10% to 40% having.

Particles of an organic material, in particular powdered plastic should be te with a share in the range 20 vol .-% to 40 vol .-% who added the.

The starting material for the production of the components can be admixed with silica powder with a mean particle size d ₅₀ between 20 pm and 100 pm before the shaping, the particle size of which is retained during the shaping and can thus be formed during the siliconization of pores. Otherwise, the same parameters and procedures can be selected in the manufacture of components, as they can be used for the production of hard material particles, which in particular features of claims 5 to 7, in part from claim 8 to 11 and 13 concerns.

In order to produce grinding wheels, the granules should preferably be subjected to a shaping process prior to siliconization prior to pyrolysis, e.g. Pressing, isostatic pressing, extruding or molding subjected to the who. This is followed by the siliconization, which leads to a three-dimensional Bin tion of diamond particles in a SiC matrix / scaffold, as in the above-described hard material particles within the particles. The introduction of the pore former or the soft phase, which primarily wears at tribological or abrasive stress and thus creates pores in the material, in a matrix material, it can follow according to typical ceramic technologies. These can also be added separately to a dried granulate before pressing.

The granules formed at least with diamond particles and organic binder can be silicon or silicide particles supplied in a number and size, which corresponds to the number of desired pores. By Kapil larkräfte can then take place during a heat treatment, preferably in a vacuum in situ infiltration of the material and there is no need to add silicon from the outside.

The pores or the faster-wearing particles replacing them can be generated as follows:

1) Pore formers (organic particles such as PMMA, starch, polypropylene, polystyrene) may be added which may pyrolyze and form dense surface layers during siliconization, which may cause the formation of a

Preventing silicon infiltration or for the Si poorly wetted Oberflä surfaces, such as BN or Si0 ₂ form.

2) the granules may be supplied with Si or silicide particles in a number and size corresponding to the number of pores. Capillary forces are then used to in situ infiltrate the workpiece during a heat treatment, preferably in a vacuum, and no Si need be added from the outside. the.

3) The introduction of faster-wearing particles in the component material can be done according to typical ceramic technologies. These particles can be mixed in between the granulated diamond granules or hard material particles, for example dry, or the starting suspension can be added. This is followed by shaping and further processing by means of pyrolysis / siliconization.

4) It is also possible to mix the SiC bonded diamond hard material particles according to the invention in the finished form with diamond particles and binder and then to shape these and then pyrolyzed according to and silicify accordingly. The necessary Si can be supplied either from the outside, or even directly in the diamond particle binder mixture, suspension are introduced. In the latter case, the Si particle sizes should approximate the desired pore size.

In addition, excess Si can be partially or completely dissolved out with alkaline solutions (e.g., 20% NaOH) at room temperature or elevated temperatures (60 ° C - boiling temperature) so as to clear the pores.

In the same way, the porosity of SiC-bonded hard material particles can be achieved.

The SiC bound diamond granules and porous construction parts according to the invention may also be used in multiple layers on / in one component. A substrate made of SSiC or SiSiC or also short or long fiber reinforced SiC ceramic to achieve a higher rigidity or better connection to tools, can thereby form a base on which hard material particles can be arranged and fixed.

SiC bonded hard particles or components can be advantageously used as abrasive grains, for the production of abrasive articles, with hard material particles Verstärkk th components for protection and applications for wear protection, as an abrasive, grinding pin or for protection and applications for wear protection. The invention will be explained in more detail by way of examples.

Showing:

Figure 1 in schematic form possibilities for the production of SiC bound diamond hard particles and

Figure 2 in schematic form possibilities for producing a

Component.

In the left-hand illustration of Figure 1, the granules consisting of Dia mantpartikeln and a pyrolysed binder (thick black border of the diamonds) are shown. They are separated by Si and spacers S. This is the state before the siliconization and reactive formation of SiC.

During the siliconization, powdery Si and vitreous carbon formed on surfaces of diamond particles during pyrolysis and diamond partially formed form a SiC matrix in which the diamond particles are incorporated. Even after the silicification they are parried by the placeholders and therefore easy to separate.

In the left-hand representation of FIG. 2, a shaped body is made of a mixture consisting of diamond particles which have a glass-like carbon layer on their surface by means of pyrolyzed binder. In addition, particles P of polyurethane are included as pore formers.

In the right-hand illustration of Figure 2, the state after a siliconization is shown. The diamond particles are embedded in a matrix formed with reactively formed SiC. In the matrix, islands of Si and pores are contained. Si and the pores Po form quasi "predetermined breaking points", so that with a mechanical and / or tribological stress diamond particles break out together with SiC residues from the component material and can be achieved by adapting to abrasive or tribological requirements during use For example, the pores may serve as reservoirs for abrasion or cooling or additional abrasives.

example 1 For the production of diamond powder with an average particle size d ₅₀ of 50 pm is granulated together with an organic binder. The Diamantpul ver is thereby mixed aqueous or in a solvent with the organic Bin and agglomerated via a Granulationstechnologie (eg Sprühgranulie tion, fluidized bed granulation, build-up granulation, etc.). The granules thus obtained have an average particle size of 500 pm. The granules produced are then pyrolyzed under Ar atmosphere at 800 ° C, wherein the organic constituents of the binder are converted into a glasarti gene carbon. This vitreous carbon acts as a binder phase between the diamond granules in the agglomerates or a bed thereof and reacts further to silicon carbide during the reactive silicon infiltration. The siliconization is carried out under vacuum conditions at 1550 ° C as bulk material. For this purpose, the carbon-coated diamond granules produced are mixed with a mixture of coarse silicon powder having an average particle size d ₅₀ of about 200 μm and a further fine fraction of powdered silicon having an average particle size d ₅₀ of 10 μm. In this case, the fine fraction of the silicon powder acts primarily as a spacer to prevent bridge formation between the individual granules formed with crystallized silicon and SiC. As a result, the SiC bonded diamond hard particles can be easily singled in the jaw crusher and then classified by sieving again. As a result, a narrow grain band can be produced, for example with particle sizes between 450 pm and 550 pm.

The SiC bound diamond hard particles consist of diamond and reactively formed silicon carbide and residual silicon not reacting with silicon carbide.

Example 2

For the preparation of hollow sphere granules a build-up granulation should be used. For this purpose, diamond powder with an average particle size d ₅₀ of 50 μm is dispersed with an organic binder in a suspension for the production. In the following, by means of build-up granulation, a two-component agglomerate is obtained, wherein the suspension containing diamond particles during the granulation on coarse silicon particles with a average particle size d ₅₀ of 100 miti sprayed during the granulation (fluidized bed granulation).

The granules obtained had an average particle size d ₅₀ of 500 pm. The granules thus prepared are then pyrolyzed under non-oxidizing atmosphere at 800 ° C, wherein the organic constituents of the binder Be are converted into a glassy carbon. This glassy carbon acts as a binder phase between the diamond particles on the surfaces of which a coating of this glassy carbon has formed and this carbon reacts during the reak tive silicon infiltration on to silicon carbide.

During the final heat treatment under vacuum conditions at 1550 ° C, the resulting granules are silicided from the inside out. To support the siliconization, a further fine fraction of pulverförmi gem silicon having an average particle size of 10 pm, added to who. In this case, the fine fraction of the silicon powder primarily acts as a spacer to prevent bridging between granules consisting of diamond, crystallized silicon and SiC.

Due to the technology used in built-up granulation, silicization results in the formation of hollow granules from the inside. The granules produced, consist of diamond and reactive silicon silicon carbide and possibly, remaining unreacted silicon. They can be classified and applied after siliciding.

Residual adherent unreacted Si could be dissolved in 20% NaOH at 60 ° C. within 1 h with stirring.

Example 3

The production of porous diamond abrasive bodies is based on a diamond-containing suspension. In this will be a bimodal

Diamond particle size fraction consisting of mean particle sizes d ₅₀ of 50 pm and 5 pm used. Furthermore, as a further solid material component is a silicon powder having an average particle size d ₅₀ of 100 pm in the suspension. As a placeholder is a polystyrene powder with a average particle size d _{50 used} by 200 pm. The ratios of the solids diamond to silicon to polystyrene amount to 2 to 2 to 1 volume. As binder in the aqueous suspension comes an aqueous

Polyvinyl acetate dispersion which crosslinks on drying, used.

The processing and shaping of the suspension takes place by slip casting. During the final heat treatment, the diamond-containing molding is pyrolyzed under non-oxidizing atmosphere at 800 ° C and then reaction-bonded under vacuum conditions at 1550 ° C. During pyrolysis, the organic binder transforms into a glassy carbon with the outgassing of volatile constituents. This glassy carbon acts as a binder phase between the diamond particles in the agglomerates and reacts during the subsequent reactive

Silicon infiltration on to silicon carbide. The polystyrene spacers are almost completely broken down into volatiles so that they are present as pores in an abrasive article formed with the granules. In the reactant compound, the silicon present in the material melts and reacts with the existing carbon formed from the pyrolyzed organic binder and settles on diamond particle surfaces. This forms a porous diamond SiC-Si-containing composite material, which can be used as an abrasive body.

Example 4

The production of porous diamond abrasive bodies takes place on the basis of a diamond-containing suspension. This is a bimodal diamond particle size fraction with diamond particles of a middle

Particle size d ₅₀ of 50 pm and 5 pm used. Furthermore, a silicon powder having an average particle size d ₅₀ of 100 μm is in the suspension as the second solid component. The mass ratios of the solids diamond to silicon are 2 to 1.

As organic binder in the aqueous suspension comes a

Polyvinyl acetate dispersion which crosslinks on drying, used. The Sus pension is further added a surfactant as a foaming agent. The suspension is foamed by means of a high-speed stirrer and then poured into a non-sucking mold and freeze-dried net. After removal from the mold, the heat treatment steps follow. In this case, the diamond-containing molded part is pyrolyzed under non-oxidizing atmosphere at 800 ° C and then reaction bonded under vacuum conditions at 1550 ° C. In pyrolysis, the organic constituents of the binder transform under gasification of volatiles into a glassy carbon coated with the surfaces of the diamond particles who the. In the reaction bonding during the heat treatment, the present silicon melts and reacts with the existing carbon of the pyrolyzed binder and the diamond particle surfaces. This forms a porous diamond SiC-Si-containing composite material.

Example 5

The production of porous diamond abrasive bodies is based on a diamond-containing granules. The granules are agglomerated by conventional granulation technology (e.g., spray granulation, fluid bed granulation, granulation, etc.) and have an average size of 200 μm-1000 μm. The produced granules include a

Diamond particle size fraction with a mean particle size d ₅₀ of 50 pm, a silicon particle size fraction with a mean particle size d ₅₀ of 50 pm and a particle size fraction of a polystyrene powder with a mean particle size d ₅₀ of 100 pm. The granules are bound by an organic sugar-based binder in aqueous suspension. The ratios of the solids diamond to silicon to polystyrene amount to 1 to 1 to 1 volume.

The granules produced are then formed by a pressing process (eg by isostatic pressing or uniaxial pressing) to a Formkör by. Subsequently, the pyrolysis takes place under non-oxidative atmosphere at 800 ° C. In this case, organic constituents of the bin are converted to a vitreous carbon with the outgassing of volatile constituents, with which surfaces of diamond particles are coated. The polystyrene particles as placeholders are almost completely split into volatile components, so that they are present as pores in the finished product. at In the following reaction bonding, the silicon present in the material melts and reacts with the existing carbon obtained from the pyrolyzed binder, and diamond particle surfaces are coated with silicon carbide. This forms a porous diamond SiC-Si-containing composite material.

Claims

claims

1. SiC bonded diamond hard material particles having a composition of 30% by volume - 65% by volume of diamond, 70% by volume - 35% by volume of SiC and 0 to 30% by volume of Si, and diamond particles individually Hard material particles with the SiC and Si formed during the thermal treatment are bonded together in a material-locking manner and have a particle size in the range from 50 μm to 5000 μm, preferably <2000 μm, more preferably <1000 μm.

2. SiC bound diamond hard material particles according to claim 1, characterized in that an average particle size d ₅₀ of diamond particles in the hard particles in the range of 5 pm to 500 pm is maintained.

3. SiC bonded diamond hard material particles according to one of the preceding claims, characterized in that a maximum of 90% of the upper surface of the diamond particles are materially bonded to SiC.

4. A process for producing SiC-bonded diamond hard particles according to one of the preceding claims, characterized in that diamond particles are mixed with an organic binder and formed into granules by a drying and granulation process, subjected to a thermal treatment in an oxygen-free atmosphere in which a pyrolysis of the organic constituents takes place and carbon formed in situ from the organic binder in the pyrolysis is deposited in glassy form on surfaces of diamond particles and during this thermal treatment or during a subsequent thermal treatment with admixed powdery particles. silicon and particulate spacers (S) carried out a siliconization and is thereby formed with the diamond deposited on surfaces of diamond particles Koh and / or with the diamond particles by chemical reaction of silicon carbide, so that the hard material particles are formed

Diamond particles in the individual hard material particles with the SiC reactively formed during the thermal treatment and the silicon material are joined together so that the formed Gra nulate means of the added silicon and / or the placeholders (S) on their surface predominantly or completely separated or in are kept at a distance from each other.

5. The method according to claim 4, characterized in that for place holder (S) chemical elements or compounds are used which are difficult to be wetted by Si, do not form an alloy with Si and / or will not react with Si to form a solid compound of To minimize granules together, these chemical ele ments or compounds are preferably selected from hexagona lem BN, Si ₃ N ₄ , AIN, Al ₂ 0 ₃ , Si0 ₂ , Zr0 ₂ and a nitride, carbide of the transition metals, in particular the group 4 and 5 of the periodic system.

6. The method according to claim 4 or 5, characterized in that the organic binder and its amount are selected so that the organic binder as a carbon source in a proportion of between 1.5% by mass and 20% by mass in relation to the total mass of dianthone particles used is used.

7. The method according to any one of claims 4 to 6, characterized in that diamond particles in at least two different

Particle size fractions, preferably a coarse and a fine particle size fraction, particularly preferably a fine

Particle size fraction which has 0.1 to 0.3 times the size of the diameter of the coarse particle size fraction and a proportion of 5 V o \ .-% - 50 vol .-% of the coarse particle size fraction, are used sets.

8. The method according to any one of claims 4 to 7, characterized in that the granulated particles before the siliconization silicon powder having an average particle size d ₅₀ in the range of 5 pm - 1000 pm, preferably be in the range 10 pm - 150 pm and in this area is added with a volume of 10 vol .-% - 200 vol .-%, preferably 60 vol .-% - 160 vol .-% of the content of diamond particles.

9. The method according to any one of claims 4 to 8, characterized in that the hard material particles are gebil det with at least one further phase, which is preferably selected from B ₄ C, TiC and TiB ₂ .

10. The method according to any one of claims 4 to 9, characterized in that diamond particles having an average particle size of 10 pm - 50 pm, preferably 15 pm - 30 pm or more preferably 10 pm - 20 pm are used.

11. The method according to any one of claims 4 to 10, characterized in that the hard material particles are brought into a defined shape, preferably spherical, cylindrical, prismatic, pyramidal in particular by Extrusi on or by casting.

12. The method according to any one of claims 4 to 11, characterized in that the involvement of the diamond particles and / or a possible partial breaking out of the diamond particles in / from a matrix formed with the reactively formed SiC and Si during a mechanical / tribological stress, by the maximum temperature in the siliconization and the purity of the diamond particles used is / are influenced.

13. The method according to any one of claims 4 to 12, characterized in that inside hollow hard material particles by applying a suspen sion, in addition to diamond particles is also an organic binder hold ent, on silicon particles having a particle size in the range 50 pm - 150 pm or by admixing particles of a pulverulent organic substance which decomposes during the thermal treatment, preferably polymethyl methacrylate, polyurethane, polyethylene or polypropylene or starch and

subsequent thermal treatment in which a pyrolysis, the Mi rule with Si powder and the spacer (S) and a reactive Bil formation of SiC is carried out; wherein the proportion of zugege benem powdered silicon volume of 10 vol .-% - 200 vol .-%, preferably 60 vol .-% - 160 vol .-% of the content of diamond particles to be given.

14. Porous component is formed from SiC-bonded diamond particles, and the component has a porosity in the range of 10% to 40%, preferably between 10% and 30%,

has an average pore size between 10 pm - 100 pm, preferably between 20 pm - 50 pm and

from 30% by volume to 65% by volume of diamond, 70% by volume to 35% by volume of SiC and 0% by volume to 30% by volume of Si, preferably from 40% by volume to 60% by volume % Diamond, 60% by volume, 40% by volume SiC and 2% by volume to 20% by volume Si, and the diamond particles contained have an average particle size in the range from 5 μm to 500 μm, preferably in the range 30 pm - 100 pm, particularly preferably> 50 pm - 200 pm.

15. Component according to claim 14, characterized in that at least one further phase with dummy function, which primarily wears at tribological or abrasive stress and thus forms pores in the material, is contained, wherein the further phase (s) with non-diamond nem carbon, Si. ₃ N ₄ , which may also be sintered, Al ₂ 0 ₃ or transitional alumina, dense or porous glass beads, melt the silicide or boride, in particular TiSi ₂ MoSi ₂ , WSi ₂ , TiB ₂ , W ₂ B ₅ , WB ₂ or Zr0 ₂ with a variety of dopants, at least one ren refractory oxide or silicate, in particular MgO or talc, at least one transition metal carbide, oxicarbide, nitride or boride is / are formed.

16. A method for producing a component according to one of claims 14 or 15, characterized in that

Diamond particles with SiC, an organic binder and particles of an organic material, preferably with powdered plastic as Po renbildner, in particular polystyrene, Polyemthylmethacrylat, Polyure than, polyethylene or polypropylene or starch preferably having an average particle size d ₅₀ in the range 30 pm to 100 pm before Ther mixing treatment mixed and then formed over a molding process, then

be subjected to a thermal treatment in an oxygen-free atmosphere in which a pyrolysis of the organic constituents takes place le and in the pyrolysis of the organic binder in situ formed carbon in glassy form deposits on surfaces of Dia mantpartikeln and during this thermal treatment or at a follow The second thermal treatment with externally supplied Sili cium carried out a siliconization and thereby carbon is deposited with the deposited on surfaces of diamond particles Koh and the diamond by chemical reaction of silicon carbide, so that

the component material has a composition of 30% by volume - 65% by volume of diamond, 70% by volume - 35% by volume of SiC and 0 to 30% by volume of Si and a viscosity in the range from 10% to 40% having.

17. The method according to claim 16, characterized in that the organic binder and its amount are selected such that the organic binder is used as the carbon source with a proportion of between 1.5% by mass and 20% by mass relative to the total mass Dia mantpartikeln is used.

18. The method according to any one of claims 16 or 17, characterized in that diamond particles in at least two different particle size fractions, preferably a coarse and a fine Particle size fraction, more preferably a fine

Particle size fraction, which has 0.1 to 0.3 times the size of the diameter of the coarse particle size fraction and a proportion of 5 vol .-% - 50 vol .-% of the coarse particle size fraction, is set to be.

19. The method according to any one of claims 16 to 18, characterized in that particles of an organic material, preferably powdered plastic, in particular polystyrene, polymethylmethacrylate, Polyure than, polyethylene or polypropylene or starch in a proportion in the range 20 vol .-% to 40 Vol .-% is added.

20. The method according to any one of claims 16 to 19, characterized in that a further phase (s) with non-diamond carbon, B ₄ C, TiC and TiB ₂ , Si ₃ N ₄ , which may also be sintered, Al ₂ 0 ₃ or transitional alumina, dense or porous glass spheres, high-melting the silicide or boride, in particular TiSi ₂ MoSi ₂ , WSi ₂ , TiB ₂ , W ₂ B ₅ , WB ₂ or Zr0 ₂ with a variety of dopants, at least one other high-melting oxide or silicate, in particular MgO or talc, at least one transition metal carbide, oxicarbide, nitride or boride is homogeneously admixed prior to molding.

21. The method according to any one of claims 16 to 20, characterized in that the integration of the diamond particles and / or a possible partial breaking of the diamond particles in / from a matrix formed with the reactively formed SiC and Si during a mechanical / tribological stress, by the maximum temperature in the siliconization and the purity of the diamond particles used is / are influenced.

22. The method according to any one of claims 16 to 21, characterized in that the starting material is mixed with silicon powder having an average particle size d ₅₀ between 20 pm - 100 pm prior to shaping, the particle size during the shaping is maintained ten and thus during the silicification pores form.

23. The use of SiC bonded hard material particles according to any one of claims 1 to 4 or components according to any one of claims 14 to 15 as abrasive grains, for the production of abrasive articles, reinforced with hard particles particles for wear protection and wear protection applications, as an abrasive, grinding pin or

Protection and wear applications.