Process for producing a ceramic brake component

Abstract

Method for producing a ceramic brake component (2), in particular a friction unit, the method comprising the following steps: Providing (S2) a green body (1), Converting (S3) the green body (1) into a porous carbon body, wherein the green body (1) and / or the carbon body is provided with the desired shape of the brake component, and Infiltrating (S4) the carbon body with at least one liquid and / or gaseous substance, wherein the green body (1) comprises at least one polymer-based binder and at least one carbonizable biologically based filler material.

Description

Technical area

[0001] The present invention relates to a method for producing a brake component. Technical background

[0002] In known braking systems for vehicles, aircraft, rail vehicles, and / or other industrial applications such as elevators or machine tools, it is known to provide a friction unit designed for frictional engagement with a counter-body. During braking, the kinetic energy of the vehicle, aircraft, rail vehicles, and / or other industrial applications such as elevators or machine tools is converted into heat through friction, which is absorbed by the brake disc and brake pads. Therefore, the friction characteristics of the brake material and its ability to store and dissipate heat are one of the limiting factors of a brake assembly.

[0003] In general, brake materials must therefore possess very good thermomechanical properties, high and consistent friction characteristics, and good abrasion resistance. These friction units can be made of metal and / or ceramic composites. These ceramic composites can be manufactured from a porous carbon body that corresponds to the final contour of the friction unit, the pores of which are infiltrated with another substance to form the friction unit by initiating a chemical reaction with the carbon of the carbon body. In known friction units, a phenolic resin powder is typically mixed with short carbon fibers obtained through a pyrolysis process. This mixture is cured and pyrolyzed to obtain a porous carbon body, which is then typically infiltrated with silicon in any aggregate state to produce a silicon carbide or doped silicon carbide ceramic.

[0004] However, the production of both the carbon fibers used and the ceramic components for the friction unit is energy-intensive, so that the production of a ceramic brake component is, on the one hand, relatively expensive and, on the other hand, has a relatively large CO2 equivalent balance.

[0005] It is therefore an object of the present invention to provide a cost-effective method for producing a brake component with fewer manufacturing steps and with improved physical and / or mechanical properties, which has an improved CO2 equivalent balance. Summary of the invention

[0006] This object is achieved by a method for producing a ceramic brake component according to patent claim 1.

[0007] The following describes a method for manufacturing a ceramic brake component. The brake component can be, in particular, a friction unit, such as a friction disc, a brake disc, a brake pad, or the like. The method comprises the following steps: Providing a green body, Converting the green body into a porous carbon body, whereby the green body and / or the carbon body is provided with the desired shape of the brake component and Infiltrating the carbon body with at least one liquid and / or gaseous substance.

[0008] In order to improve properties that influence the performance and / or usability of the brake component, such as thermal conductivity, abrasion resistance, and / or friction coefficient, while simultaneously producing the brake component cost-effectively and with an improved CO2 equivalent balance, the green body comprises at least one polymer-based binder and at least one carbonizable, bio-based filler material. In particular, the polymers used can be bio-based polymers, such as lignin, lignin derivatives, non-bio-based polymers, such as PEEK, and / or mixtures thereof. In the following, the term "CO2 balance" refers to a CO2 equivalent balance.

[0009] For example, the green body can be provided directly in the desired shape of the brake component. Furthermore, it is also possible to form the desired shape of the brake component from the provided green body. Alternatively or additionally, the desired shape of the brake component can also be machined from the carbon body. Since the volume of the green body may change during conversion into the porous carbon body, forming the carbon body can ensure that the brake component has the desired dimensions. The volume change that can occur during conversion of the green body into the carbon body can depend, among other things, on the polymer-based binder used, the amount of binder used, the bio-based filler used, the manufacturing process for the green body, etc.

[0010] The liquid or gaseous substance can be a metal, semi-metal, metal salt, polymer, hydrocarbons, or the like. Furthermore, the substance can be a mixture of several substances. For example, the substance can comprise silicon, aluminum, magnesium, titanium, copper, alloys, and / or semi-metal-containing substances such as silicon tetrachloride, which are particularly suitable for infiltrating a carbon body. In particular, if the carbon body is to be infiltrated with a mixture of several substances, at least one substance can be a main substance, and the other substances can be present as additives with a proportion of up to 20 wt.%. For example, silicon can be used as the main substance, and metal and / or metal alloys as additives. The additives can be particularly suitable for modifying the material properties of the finished brake component.For example, a suitable choice of additives can improve a friction coefficient of the surface and / or a surface layer and / or a thermal conductivity of the brake component and / or abrasion resistance.

[0011] The bio-based filling material can, in particular, be fibers, fabrics, or particles such as cellulose, cellulose fiber, lignin, and / or other natural fibers, such as wood, sawdust, wood dust, oil palm, corn stalks, bagasse, bamboo, coconut coir (coconut shell). The most important biofibers are cellulose fibers, corn husks, palm kernel fibers, coconut shells, cocoa palms, sugar cane, pineapple, banana, rice husks, rice straw, and plants (stems, leaves, seeds, fruits, stems, grass, reeds). In particular, the bio-based filling material can be a mixture of various bio-based fibers, fabrics, knits, felts, fabrics, and / or particles.

[0012] Preferably, the bio-based filler material can consist of particles and / or fibers of different sizes. This can have the advantage of allowing the number, size, and / or distribution of the pores in the porous carbon body to be adjusted.

[0013] Depending on the size of the starting material for the filler, the bio-based filler can be pressed directly with the polymer-based binder, or the bio-based filler can be comminuted using suitable methods to achieve a desired particle size. Additionally or alternatively, the filler, particularly if it consists of fibers, can be woven and / or felted and / or knitted. Since the bio-based filler is a sustainable material, the CO2 balance of the brake component and its production can be improved. Furthermore, a brake component that is at least partially made from a green body that at least partially contains bio-based filler has tailored properties, such as a tailored coefficient of friction and / or improved thermal conductivity.

[0014] Furthermore, by appropriately selecting the polymer binder content, particle size, filler material shape and other process parameters during production of the green body, such as temperature, pressure, atmospheric composition, etc., the properties of the finished brake component, such as thermal conductivity, the number, size and / or distribution of the pores or a friction coefficient, can be adapted.

[0015] The polymer-based binder preferably comprises at least one thermoset and / or a cross-linkable thermoplastic. Thermoset binders advantageously have the advantage of retaining their shape under the influence of heat, so that when the green body is converted into the porous carbon body, the shape of the green body is essentially retained. This makes it possible, in particular, to obtain a green body that is structurally stable enough to be converted into a porous carbon body without distortion.

[0016] Alternatively or additionally, phenolic resins, lignin, lignin derivatives, and / or dimensionally stable, cross-linkable, curable plastics such as PEEK can be used as polymer-based binders. A mixture of a thermoplastic binder and a thermosetting binder can also be used as a binder.

[0017] According to a preferred embodiment, the green body is produced by extrusion, pressing, cutting, turning, milling, 3D printing, and / or another additive manufacturing process. This makes it possible to provide a green body that can have any desired shape. Depending on the type of biological filler material, the green body may still be surrounded by loose particles of the filler material after the binder has cured or dried. Therefore, depending on the green body manufacturing process, it may be necessary to remove the green body at least partially from residues of the filler material, for example, if the green body is formed from a powder bed, and / or to separate it from loose, non-solidified particles. However, it should be noted that this step may be omitted with other green body manufacturing processes.The green body may then be subjected to a (fine) cleaning to remove adhering particle residues. This can be achieved, for example, by vacuuming off loose particles. However, there are no restrictions on the type of cleaning, and all known methods can be used.

[0018] Furthermore, depending on the selected manufacturing process for the green body, at least one additive can be added to the composition of the at least one polymer-based binder and the at least one carbonizable bio-based filler material, which additive is suitable for making the composition usable for the selected manufacturing process. For example, if the green body is formed by 3D printing, at least one additive for 3D printing can be added to the at least one polymer-based binder and the at least one carbonizable bio-based filler material.

[0019] Preferably, the proportion of the bio-based filler material in the green body is between at least 5 wt.% and 90 wt.%. Depending on the application, the proportion of the bio-based filler material in the green body can more preferably be between 40 and 90 wt.%. In particular, the bio-based filler material can have a particle size between 0.0001 and 2.0 mm, preferably between 0.05 and 0.5 mm.

[0020] Preferably, the green body can be cured / hardened after its production at a temperature greater than 100°C (> 100°C). According to a further preferred embodiment, the conversion of the green body into the porous carbon body is carried out by pyrolyzing the green body. The pyrolysis process is preferably carried out in a virtually oxygen-free atmosphere. A virtually oxygen-free atmosphere is understood in particular to mean an atmosphere that has less than 3% residual oxygen. This can, for example, be a protective gas atmosphere and / or a vacuum. For example, the protective gas atmosphere can comprise argon, nitrogen or other suitable gases or gas mixtures or a vacuum. Furthermore, the pyrolysis process can be carried out at a temperature of at least 400°C, in particular at a temperature between 500°C and 3000°C.This allows sufficient conversion of the contained carbon to form the porous carbon body.

[0021] Furthermore, the carbon body can be infiltrated with at least silicon. Preferably, the infiltration of the carbon body can be carried out with liquid and / or gaseous silicon. In particular, the liquid and / or gaseous silicon can comprise additives. Silicon carbide is formed by infiltrating the porous carbon body with silicon. Silicon carbide ceramic is characterized in particular by its hardness and abrasion resistance, chemical stability, and temperature resistance. Compared to the conventional materials used in standard brake components, the proposed brake component has tailored properties, such as a tailored coefficient of friction and / or improved thermal conductivity. Furthermore, the biological filler material used can also achieve an improved CO2 balance.

[0022] When silicon is infiltrated into the porous carbon body, the carbon can react with the silicon to form SiC (silicon carbide). The carbon body, located above the melting temperature of silicon and essentially above the surface of a silicon bath, absorbs silicon through capillary action. This typically results in a composite material that contains, in addition to SiC, unreacted carbon and free silicon. This is therefore referred to as a C / Si / SiC composite.

[0023] Further advantages of a brake component manufactured according to the described process are the possibility of reducing the occurrence of brake dust and / or chipping or damage, such as delamination.

[0024] Furthermore, the method may further comprise at least one optional post-processing step, in particular applying an antioxidant layer, in order to obtain the brake component.

[0025] Furthermore, a green body is also proposed which is produced according to the method described above, wherein the green body comprises at least one polymer-based binder and at least one carbonizable biologically based filler material.

[0026] Further advantages and advantageous embodiments are set forth in the description, the drawings, and the claims. In particular, the combinations of features set forth in the description and the drawings are purely exemplary, so the features may also be present individually or in other combinations. Short character description

[0027] The invention will be described in more detail below with reference to exemplary embodiments illustrated in the drawings. The exemplary embodiments and the combinations shown in the exemplary embodiments are purely exemplary and are not intended to define the scope of the invention. This scope is defined solely by the appended claims.

[0028] They show: Fig. 1: a flowchart of a method for producing a brake component according to an embodiment, Fig. 2: a green body for the process for producing a brake component, and Fig. 3: a brake component manufactured according to the process according to Fig. 1. Detailed description of the invention

[0029] In the following, identical or functionally equivalent elements are identified by the same reference symbols.

[0030] Fig. Figure 1 shows the steps for manufacturing a brake component according to one embodiment. The brake component can, in particular, be a friction disc for a brake system.

[0031] First, in a first step S1, a composite material is produced by mixing at least one polymer-based binder and at least one biologically based filler material together.

[0032] The bio-based filling material can, in particular, be fibers, fabrics, substances, or particles such as cellulose, cellulose fiber, lignin, lignin derivatives, and / or other natural fibers, such as wood, sawdust, wood dust, oil palm, corn stalks, bagasse, bamboo, coconut coir (coconut shell). The most important biofibers are cellulose fibers, corn husks, palm kernel fibers, coconut shells, cocoa palms, sugar cane, pineapple, banana, rice husks, rice straw, and plants (stems, leaves, seeds, fruits, stems, grass, reeds). In particular, the bio-based filling material can be a mixture of various bio-based fibers, fabrics, substances, and / or particles.

[0033] The polymer-based binder is preferably a thermoset, such as phenolic resins, lignin, and / or lignin derivatives, which represents a bio-based binder. Alternatively, other dimensionally stable, cross-linkable, curable plastics, such as PEEK, or a mixture of a thermoplastic binder and a thermoset binder can be used.

[0034] Preferably, the proportion of the biologically based filling material in the composite material is between 5 wt.% and 90 wt.% and has a particle size between 0.0001 and 2.0 mm, preferably between 0.05 and 0.5 mm.

[0035] In step S2, a green body of the brake component is produced from the composite material by extrusion, pressing, cutting, turning, milling, 3D printing, and / or another additive manufacturing process, followed by curing of the binder. Depending on the type of biological filler material, the green body may still be surrounded by loose particles of the filler material after the binder has cured or dried. Therefore, depending on the manufacturing process of the green body, the green body can be removed from a powder bed of the filler material or separated from the loose, unconsolidated particles. Furthermore, a (fine) cleaning of the green body can follow to remove adhering particle residues. Cleaning can be performed, for example, by vacuuming the loose particles with a vacuum cleaner. However, the type of cleaning is not restricted, and all known methods can be used.

[0036] Subsequently, in a step S3, the green body is converted into a porous carbon body by pyrolysis. This can preferably be carried out in an oxygen-free atmosphere. A protective gas atmosphere, for example, consisting of argon, nitrogen, or other suitable gases or gas mixtures, and / or a vacuum can be used. The pyrolysis process is advantageously carried out at a temperature of at least 400°C. This allows sufficient conversion of the contained carbon to form the porous carbon body. Alternatively, the desired shape of the brake component can also be subsequently machined from an already produced carbon body.

[0037] Finally, to obtain the braking component, the carbon body is infiltrated with at least liquid silicon in step S4. In particular, the liquid silicon may contain additives such as metals, metal alloys, metal salts, or the like.

[0038] Alternatively, the carbon body can be infiltrated with gaseous silicon. When the carbon body is infiltrated with silicon, silicon carbide, in particular, is formed. Silicon carbide ceramics are characterized by their hardness and abrasion resistance, chemical stability, and temperature resistance. This typically results in a composite material that contains SiC, unreacted carbon, and free silicon. It is therefore referred to as a C / Si / SiC composite.

[0039] The additives can be particularly suitable for modifying the material properties of the finished brake component. For example, by appropriately selecting the additives in the overall composition, a friction coefficient of the surface and / or a surface layer and / or a thermal conductivity of the brake component can be tailored. Alternatively, the green body 1 can also be infiltrated with other liquid or gaseous substances such as metals, semimetals, metal salts, polymers, hydrocarbons, or the like. Furthermore, the green body can also be infiltrated with a mixture of several substances.

[0040] Fig. 2 shows a green body 1 obtained after step S2 and Fig. 3 shows the finished brake component 2. As can be seen from the comparison of the Fig. 2 and Fig.As can be seen in Figure 3, the green body 1 does not lose its basic shape when converted into the porous carbon body by a pyrolysis process. However, it is possible that the volume of the green body 1 changes during conversion into the porous carbon body. The volume change that can occur during conversion of the green body 1 into the carbon body can depend, among other things, on the polymer-based binder used, the bio-based filler used, the manufacturing process for the green body, etc.

[0041] In summary, a manufacturing process for a brake component is proposed that makes it possible to obtain a brake component that not only has tailored physical and / or mechanical properties, such as a tailored friction coefficient and / or improved thermal conductivity, but can also be produced cost-effectively and with an improved CO2 equivalent balance.

[0042] Since the bio-based filler material is a sustainable material, the CO2 equivalent balance of the brake component and its production can be improved. Compared to the conventional friction units used in brake components, in which the carbon fibers used are produced through an additional energy- and emissions-intensive pyrolysis process, the biological filler material used can achieve an improved CO2 equivalent balance. Further advantages of a brake component manufactured using the described process include the possibility of reducing the occurrence of brake dust and / or chipping or damage, such as delamination. Furthermore, the brake components obtained using the process described above can exhibit improved thermal conductivity compared to known brake components. List of reference symbols S1 -S4 process steps 1 green body 2 bearing component

Claims

[1] Method for producing a ceramic brake component (2), in particular a friction unit, the method comprising the following steps: Providing (S2) a green body (1), Converting (S3) the green body (1) into a porous carbon body, wherein the green body (1) and / or the carbon body is provided with the desired shape of the brake component, and Infiltrating (S4) the carbon body with at least one liquid and / or gaseous substance, characterized by , that the green body (1) comprises at least one polymer-based binder and at least one carbonizable biologically based filler material. [2] The method of claim 1, wherein the biologically based filler material comprises wood, cellulose, cellulose fiber, lignin and / or natural fibers. [3] The method according to claim 1 or 2, wherein the polymer-based binder comprises at least one thermoset and / or a crosslinkable thermoplastic. [4] Method according to one of the preceding claims, wherein the green body (1) is produced by extrusion, pressing, cutting, turning, milling, 3D printing and / or an additive manufacturing process. [5] Method according to one of the preceding claims, wherein a proportion of the biologically based filling material in the green body (1) is at least 5 wt.%, preferably between 5 and 90 wt.%. [6] Method according to one of the preceding claims, wherein converting the green body (1) into the porous carbon body comprises pyrolyzing the green body (1). [7] Process according to claim 6, wherein the pyrolysis process is carried out under an oxygen-free atmosphere, in particular under a protective gas atmosphere and / or in a vacuum. [8] A process according to claim 6 or 7, wherein the pyrolysis process is carried out at a temperature of at least 400°C. [9] Method according to one of the preceding claims, wherein the carbon body is infiltrated at least with silicon. [10] Method according to one of the preceding claims, wherein the method further comprises at least one optional post-processing step, in particular polishing, honing, grinding, etc., in order to obtain the brake component. [11] Green body (1) for the method for producing a brake component (2), in particular a friction unit according to one of claims 1 to 10, wherein the green body (1) comprises at least one polymer-based binder and at least one carbonizable biologically based filler material.

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