Rbsic component comprising an sic coating, use of an sic coating, and method for manufacturing a component

Abstract

The invention relates to a component (1) comprising a component body (2) made of a reaction bonded silicon carbide (RBSiC), the component body (2) having a body surface (3) at least partially coated with a coating (4), the coating (4) consisting of silicon carbide (SiC) with a layer thickness of at least 25 µm. The invention also relates to the use of such an SiC coating and to a method for manufacturing a component comprising an SiC coating.

Description

[0001] RBSiC component with SiC coating, use of a SiC coating and method for producing a component

[0002] The invention relates to a component having a component body made of reaction-bonded silicon carbide (RBSiC) according to the preamble of claim 1, a use according to claim 23 and a method for producing a component having a component body made of reaction-bonded silicon carbide (RBSiC) according to claim 24.

[0003] Various components made of reaction-bonded silicon carbide (RBSiC) are known from the state of the art. RBSiC exhibits good temperature stability up to 1380 °C, a low coefficient of thermal expansion, high rigidity (Young's modulus > 380 GPa), and high hardness. For this reason, RBSiC-based products are used in many highly stressed applications, including burners and radiant tubes in industrial furnaces, rollers for roller kilns, kiln furniture for sintering porcelain and cordierite, and mechanical seals. A further advantage of RBSiC is its low shrinkage (< 1%) during the manufacturing process, allowing the production of very large components with high dimensional accuracy.

[0004] However, the properties of RBSiC are insufficient for many applications. In such cases, state-of-the-art components are manufactured from sintered silicon carbide (SSiC). Compared to RBSiC, SSiC exhibits greater hardness, greater strength, better chemical resistance, and higher temperature resistance. A disadvantage is the high cost of manufacturing components from SSiC, because its shrinkage during the manufacturing process is significantly greater than that of RBSiC. The SSiC material shrinks by more than 10% during the sintering process, usually around 20%. This results in difficulties, particularly in the production of large components, due to cracking, component stresses, and insufficient dimensional accuracy. The result is high production waste.

[0005] In practice, RBSiC is therefore predominantly used for larger and more complex components, as long as it achieves the necessary product properties.

[0006] The object of the invention is therefore to provide a solution that enables large and cost-effective components with low scrap rates, high dimensional accuracy, and increased hardness, greater strength, better chemical resistance, and higher temperature resistance compared to components made of RBSiC. Furthermore, the goal is to achieve lighter components with comparable strengths compared to RBSiC, thereby reducing resource consumption, which contributes to improving the ecological footprint and saving material costs.

[0007] Main features of the invention are set forth in the characterizing part of claim 1 and claims 23 and 24. Embodiments are the subject of claims 2 to 22 and 25 to 29.

[0008] In a component having a component body made of a reaction-bonded silicon carbide (RBSiC), the invention provides that the component body has a body surface that is at least partially coated with a coating, wherein the coating consists of silicon carbide (SiC) with a layer thickness of at least 25 pm.

[0009] The advantage of this is that the component body can be manufactured from RBSiC with high dimensional accuracy and low scrap, as is well known. Coating the body surface with SiC increases the surface hardness and chemical resistance in the area of ​​the coated body surface. Furthermore, the coating locally and thus overall increases the component strength, as the SiC coating acts, for example, like a kind of exoskeleton or exoshell relative to the component body. Because the thermal expansion coefficients (CTEs) of the RBSiC and the SiC coating are close to each other (difference less than 1*10 A- 5 W / mK), even very large RBSiC components can be coated without layer delamination, and special strength properties can be achieved in the composite. In particular, this allows for the creation of particularly lightweight yet high-strength components. The use of RBSiC material can be reduced and is, to a certain extent, offset by the SiC coating. A coating of 25 pm or more can already provide effective protection against furnace atmospheres and the resulting alloy formation.

[0010] The component body can, in particular, be a base body made of reaction-bonded silicon carbide (RBSiC). The base body can be produced from an initially porous green body by infiltration with silicon (Si) and firing. The base body is then solid and gas-tight. The green body characterizes a state before firing, with this precursor consisting, for example, of SiC powder, carbon, and organic additives, optionally also silicon. The infiltration and reaction take place subsequently.

[0011] According to a specific development, it is provided that the layer thickness is at least 50 pm, more preferably at least 100 pm, even more preferably at least 300 pm, and particularly preferably at least 500 pm.

[0012] With increasing layer thickness, the component strength is further increased, and the coating exhibits greater durability under chemical and mechanical stress. For layer thicknesses > 100 μm, and better > 300 μm, the SiC coating provides, for example, efficient protection against abrasive particles. For example, SiC synthesized via vapor deposition typically exhibits strength values ​​of

[0013] > 500 MPa. Thus, with a SiC coating thickness of 120 pm, the characteristic strength of standardized RBSiC bending rods was increased by 10% compared to the uncoated grade; with a SiC coating thickness of 600 pm, a strength increase of 50% was achieved. In absolute terms, this means an increase in the characteristic bending strength to 306 MPa in the coated version compared to 208 MPa in the uncoated test specimens.

[0014] According to a more detailed embodiment, the body surface has subregions oriented in different spatial directions, with the coating being arranged at least in subregions that point in at least two of six spatial directions. This contributes in particular to a multidimensional increase in strength. Depending on the application, components are subjected to different loads. During component design, the areas of the component body with the most critical loads can be identified and reinforced using the SiC layer.

[0015] For example, in components subject to multidimensional loading, it is particularly advantageous to apply the SiC coating in several spatial directions to strengthen the component. For this purpose, it is optionally possible for the coating to be applied in sub-regions that point in at least three of the six spatial directions, preferably at least four of the six spatial directions, more preferably five of the six spatial directions, and particularly preferably in all six spatial directions.

[0016] Furthermore, optional component designs are available in which the coating is arranged at least in a partial area of ​​the body surface that belongs to a stiffening structure of the component body, for example a stiffening structure from the group of rib, web, strut, tension rod, compression rod, honeycomb, edge or thickening.

[0017] In a special further development, the stiffening structure is a skeleton, a framework, or a bionic structure.

[0018] With regard to the coating, it is preferably provided that the silicon carbide (SiC) of the coating has a purity of 98%, preferably 99%, and particularly preferably 99.9%. The purity can be determined using X-ray fluorescence analysis (XRF) and ICP spectroscopy (Inductive Coupled Plasma). If such a high-purity SiC coating is used, relatively inexpensive RBSiC can be used for the component body, for example with a purity of < 99% (sum of Si and SiC), or impurities of > 100 ppm or even > 1% in the semiconductor sector (particularly diffusion furnaces). A coating with a minimum thickness of 50 pm ensures that no impurities from the substrate material reach the sensitive Si wafers. In this way, paddles, wafer boats, reactor tubes, or similar items can be manufactured cost-effectively. In concrete terms, this allows starting raw materials, i.e.essentially SiC and Si powder with more than 0.5%, but preferably less than 5%, more preferably less than 3% and particularly preferably less than 1% total contamination are used, without the wafers being contaminated in the process.

[0019] The coating preferably has a maximum thickness of 2 mm. These coating thicknesses can be applied homogeneously and without cracking, thus fulfilling the desired functions. Furthermore, the coating's benefit-to-manufacturing cost ratio is favorable. Relative to the component body, the predominant material weight fraction can thus consist of RBSiC (RBSiC compared to SiC > 70%, preferably > 80%, and particularly preferably > 95%).

[0020] Another optional parameter of the coating is that it has a grain size of no more than 20 pm, preferably no more than 10 pm, more preferably no more than 7 pm, even more preferably no more than 4 pm, and most preferably no more than 1 pm. This results in good mechanical properties of the coating. The advantage is that the strength of the component is significantly higher than the strength of the uncoated component body due to the appropriate grain size of the coating.

[0021] The grain size of the starting powder for the component body can be determined in the preliminary stage by laser diffraction particle size analysis or laser granulometric measurement of the raw material. After the component body and coating have been manufactured, and also on the final component, the grain sizes can be measured by microsection and light or electron microscopy.

[0022] It is advantageous for the component body to have an average grain size, in particular the average grain size D50, of at least 25 pm, preferably at least 50 pm, more preferably at least 70 pm, even more preferably at least 90 pm, and particularly preferably at least 100 pm. The value D50 indicates the average particle size. D50 means that 50% of the particles are smaller than the specified value. The maximum grain size of the component body should be 700 pm.

[0023] According to a special embodiment, the component body has a purity of less than 99% silicon carbide (SiC). This makes it inexpensive to manufacture. Increased material purity requirements can be met in the area of ​​the body surface by applying a suitable coating.

[0024] The component proves to be particularly advantageous if the component body is at least partially a 3D printed part or if a green body of the component body is at least partially based on a 3D printed part. Such a 3D printed part can be characterized in particular by its body surface having layer steps along applied layers. This is also how it can be recognized. The advantage of the 3D printed part is that complex structures can be efficiently formed from RBSiC, in particular by subsequently subjecting a printed green body to an infiltration firing. These complex structures can then be improved in terms of strength, temperature resistance, hardness and chemical resistance. The SiC-coated RBSiC component body achieves material properties similar to those of an SSiC component, even for components that cannot be manufactured from SSiC at all due to their shape.In combination with 3D printing, numerous new design features can be implemented, for example to increase the loading density or reduce the thermal mass. Until now, this has required the use of expensive and complex to produce high-purity RBSiC, which at the same time limits design freedom. The 3D printing process is preferably a powder bed-based method. The powder bed-based 3D printing process typically results in RBSiC grades with a lower flexural strength of < 250 MPa compared to RBSiC produced conventionally, i.e., via extrusion, pressing, or slip casting. The positive effect of the strength increase due to the SiC coating is therefore relatively greater for component bodies produced using the 3D printing process than for component bodies made from material with an already high initial strength.

[0025] While advantages can be achieved even with small coated surface areas, the strength-enhancing and hardness-enhancing properties are particularly evident with a larger coated surface area of ​​the component body. Therefore, designs are possible in which at least 70%, preferably 80%, more preferably at least 85%, even more preferably at least 90%, even more preferably at least 95%, and particularly preferably 100% of the body surface is coated with the coating.

[0026] Specifically, the coating can be a CVD (chemical vapor deposition) or PVD (physical vapor deposition) layer. CVD SiC coatings reduce the tendency of RBSiC, quartz, or SSiC to segregate impurities and also improve the corrosion resistance of the component body. In this respect, the coating can serve as a corrosion protection layer.

[0027] High strength is achieved with the coating, especially when the coating is continuous. This allows for a homogeneous structure within the coating.

[0028] The invention is particularly suitable for cases in which the component is a satellite carrier; or the component is an antenna carrier; or the component is a roller for a continuous furnace or roller furnace; or the component is a component or workpiece holder of a diffusion furnace, e.g. a paddle, baffle boat, tube or liner for a diffusion furnace; or the component is a burner or radiant tube in a furnace; or the component is a sliding ring or a counter ring of a mechanical seal.

[0029] For satellite and antenna mounts, the high strength combined with low weight is a decisive advantage, especially in space applications. The high hardness combined with low abrasion of the coating makes mechanical seals particularly wear-resistant. In furnace applications, the chemical resistance and temperature resistance, in particular, represent a significant advance.

[0030] In a further aspect, the invention relates to the use of a coating of silicon carbide (SiC) with a layer thickness of at least 25 pm for coating a body surface of a component body made of a reaction-bonded silicon carbide (RBSiC) of a component, for: a) increasing the hardness of the body surface of the component; and / or b) increasing the strength of the component; and / or c) improving the chemical resistance of the body surface of the component; and / or d) increasing the temperature resistance of the component.

[0031] The advantageous coating of a component body made of RBSiC with SiC thus leads to low scrap rates, high dimensional accuracy, and greater strength, increased hardness, better chemical resistance, and higher temperature resistance compared to components made of RBSiC, even for large components. The use of the silicon carbide (SiC) coating with a layer thickness of at least 25 μm contributes to less material usage and a resource-efficient, particularly lightweight component design and manufacture.

[0032] The use according to the invention can optionally comprise the individual device features of the component, as specified above and below. In particular, the use can optionally also relate to the technical features of the coating, as specified above and below, isolated from the component and the component body.

[0033] Furthermore, the invention relates to a method for producing a component, comprising the following steps: a) producing a component body by a. producing a powder-based green body made of silicon carbide (SiC) and a carbon source; b. carrying out a reaction firing with infiltration of the green body with silicon (Si) to produce a base body made of reaction-bonded silicon carbide (RBSiC); b) at least partially coating a body surface of the component body with a coating of silicon carbide (SiC) with a layer thickness of at least 25 pm. The technically advantageous coating of a component body or base body made of RBSiC with SiC thus leads to low scrap rates, high dimensional accuracy, and increased hardness, greater strength, better chemical resistance, and higher temperature resistance compared to components made of RBSiC, even for large components.The process contributes to less material usage and a component that is designed and manufactured in a resource-saving and particularly lightweight manner.

[0034] The carbon source in the powder-based green body can, for example, be introduced by an impregnation step to incorporate free carbon (C) in a powder-based precursor body made of silicon carbide (SiC).

[0035] The method according to the invention can optionally be designed in such a way that the individual device features of the component are achieved as stated above and below.

[0036] Specifically, the method can provide for the body surface to have subregions oriented in different spatial directions, with the coating being applied at least in subregions oriented in at least two of the six spatial directions. This contributes to improved component properties in multiple spatial directions.

[0037] According to one method embodiment, the surface of the component intended for coating is at least partially or completely ground prior to coating. This can improve the flatness of the coating. The latter improves the strength of the coating under bending and tensile stresses, etc., and prevents cracking in the coating. Grinding, in particular, prevents surface roughness from exerting notch effects on the coating. Furthermore, this allows for a thinner layer thickness, which is more cost-effective.

[0038] The green body can optionally be manufactured by printing using a 3D printing process. The carbon source can optionally be introduced after 3D printing, for example, by impregnating the printed part. This allows for the creation of complex and bionic structures. The 3D printing process is preferably a powder-bed-based process. Printing should be followed by an infiltration process and firing, during which the printed green body is infiltrated with silicon (Si). This increases the density and strength of the component body. It proves particularly advantageous if the coating is carried out using a CVD (chemical vapor deposition) or a PVD (physical vapor deposition) process. This allows complex component structures to be coated homogeneously in a simple manner. Areas of the component body that are not to be coated can optionally be covered with stencils.

[0039] In particular, the method may provide for the component to be designed according to the description above and below. Reference is made here to the advantages stated therein.

[0040] The advantageous invention will first be presented in more detail using some examples:

[0041] RBSiC rolls

[0042] By coating RBSiC rollers with at least 25 pm, preferably at least 50 pm CVD-SiC, it is possible to protect them against aggressive media such as those encountered, for example, during the calcination of cathode material for lithium-ion battery production. Materials such as cobalt, nickel, aluminum, manganese, and lithium are frequently used here. When conventional RBSiC rollers are used, these materials tend to form alloys with the Si, thereby partially creating eutectics and thus reducing durability. Abrasion from the commonly used cordierite or mullite crucibles also produces highly abrasive particles that attack the rollers and reduce their service life. Furthermore, the aggressive furnace atmosphere created during calcination of the materials reduces the service life of the RBSiC rollers.

[0043] A coating > 25 pm or better > 50 pm can already provide effective protection against the furnace atmosphere and alloy formation; with > 100 pm, better > 300 pm, efficient protection against abrasive particles is also provided. Overall, this can significantly extend the service life of the rollers. At the same time, component production for the RBSiC component body can be made much more cost-effectively by using a powder of lower purity. The high layer thickness also helps to increase the strength of the rollers and thus to use smaller cross-sections, e.g. a reduction of 10%, than would be the case with RBSiC. This reduces the thermal mass in the furnace. Alternative pure silicon carbide rollers (SSiC) would be significantly more expensive than SiC-coated RBSiC component bodies.

[0044] Components for space technology

[0045] Another highly advantageous application of the invention is space technology. Due to the complex load introduction scenarios and the need for the lowest possible mass, thus optimized designs, the possibility of 3D printing the green body is particularly advantageous here. This allows the creation of bionic structures with high rigidity and strength while simultaneously being lightweight (e.g., 30% less than a comparable aluminum structure). Due to the increased strength resulting from the applied SiC layer, e.g., in the CVD process, either the mass of the structures can be reduced (reduced wall thicknesses, more delicate webs, etc.) or existing designs can be further reinforced. This effect can also be applied to simple geometries from other forming processes.It is advantageous here that the highest loads relevant to the ceramic, in the form of tensile stresses, always occur in the outer part of the component (the so-called edge fiber). If these outer volumes are made of a higher-strength material, the overall component strength increases. By using a fine CVD-SiC coating with grain sizes < 20 pm, preferably < 10 pm, even better < 1 pm, and with high purity (> 95%, preferably > 99%), the strength of the overall component can be significantly increased.

[0046] Cantilever paddle for use in the diffusion furnace

[0047] A ceramic body based on a reaction-bonded composite material, consisting essentially of SiC and free Si, is manufactured using a powder-bed-based 3D printing process. The layered structure begins with a formless grain consisting of SiC. The powder is based on a grain size distribution known from a technical refractory ceramic under the designation 100 / F, and thus has characteristic values ​​of d10 = 75 pm, d50 = 115 pm, d90 = 160 pm. The selective solidification of the grains occurs at locations specified by a CAD model through the dropwise addition of an organic binder, preferably furan resin, which is applied via inkjet print heads. The CAD model used here, which corresponds to the final component geometry, allows the creation of complex-shaped structures.Following these two sub-steps, the build surface is lowered by a previously defined layer thickness, for example 300 pm. This sequence of steps is repeated iteratively until the layer-by-layer implementation of the CAD model is complete. The complexly shaped precursor obtained in this way has a porosity of approximately 45 vol.% and is then infiltrated with an aqueous dispersion consisting of 30 wt.% colloidal carbon, a dispersing agent, and a wetting agent. After a first impregnation process, a complexly shaped, ceramic precursor is obtained, consisting of approximately 87 wt.% of the original SiC powder and approximately 13 wt.% colloidal carbon. After a drying process and a possible second impregnation step, this ratio changes to 79 / 21 wt.%, and after a possible third impregnation step to 76 / 24 wt.%.Depending on the size of the paddie, it may be expedient to segment it beforehand and print it in several, preferably two, parts. Then, as described here, impregnate it and thus enrich it with carbon. Following drying, these sub-segments must then be joined using organic aids (known to those skilled in the art as so-called garnishing). A further manufacturing variant using this joining technique allows the segmentation of the paddie such that one of the segments is produced using an alternative forming process, for example an extrusion process, while the other, more complexly shaped segment of the paddie is produced using the 3D printing process described here. This type of segmentation can reduce manufacturing costs, as each forming process is used according to its specific, cost-effective advantages.

[0048] After a final drying process, the complexly shaped preform (green body), obtained via one of the manufacturing routes described here, is converted into a ceramic component body based on a reaction-bonded composite material consisting essentially of SiC and free Si via a reaction firing process. After completion of this reaction firing process, the joint between the segments is no longer macroscopically detectable, resulting in a quasi-monolithic component. This component is then coated with SiC using chemical vapor deposition (CVD), with the layer thickness of the preferably crystalline SiC being between 150 pm and 600 pm. The resulting complexly shaped and coated cantilever paddle can be used to guide semiconductor "wafer boats" into and out of so-called diffusion furnaces or general furnace reactors.Another particularly advantageous feature is that the use of the CVD-SiC layer allows for comparatively small amounts of pure SiC, Si, and C raw materials to be used in the manufacture of the component body. These raw materials are typically contaminated by compounds of the elements V, Ti, Al, Fe, Na, Ca, Zr, Cu, and Ni, with the total impurity content reaching up to 3 wt.%, and in individual cases even up to 5 wt.%. The CVD-SiC layer prevents these impurities from penetrating the process chamber, thus preventing contamination of the processed wafers.

[0049] Support roller for roller furnaces manufactured by extrusion process

[0050] A ceramic body based on a reaction-bonded composite material, consisting essentially of SiC and free Si, is manufactured using an extrusion process. A plastic mass, consisting essentially of SiC powder with an average particle size of 40 μm, carbon with an average particle size of < 1 μm, and organic additives for plasticizing the mass, is extruded into a strand with a tubular cross-section using an extruder at a pressure of 40 to 55 bar. The inner and outer diameters can be varied within a range of 10 mm to 80 mm, with a roll length of up to 5000 mm.After completion of the shaping process and a subsequent drying process, the cylindrical preform obtained via one of the manufacturing routes described here is converted into a ceramic component body based on a reaction-bonded composite material consisting essentially of SiC and free Si via a reaction firing process. This component body is then coated with SiC using chemical vapor deposition (CVD), with the layer thickness of the preferably crystalline SiC being between 150 μm and 800 μm. The resulting CVD-coated roller offers increased rigidity compared to conventional, uncoated rollers based on RBSiC, thus reducing deflection under load and providing increased flexural and fatigue strength.The coated roller also offers significantly increased corrosion and abrasion resistance and is therefore particularly suitable for use in roller kilns for the calcination of CAM (cathode active material, i.e. metal oxides or phosphates based on lithium, nickel, cobalt, manganese, aluminum, iron and other elements that are corrosive to RBSiC).

[0051] Mirrors manufactured using 3D printing

[0052] A ceramic body based on a reaction-bonded composite material, consisting essentially of SiC and free Si, is manufactured using a powder bed-based 3D printing process. In this way, a concave mirror structure is created which has a topologically optimized, complexly shaped rib structure on the back of the mirror surface, e.g. a honeycomb structure, whereby the overall structure has a high specific stiffness and strength, while at the same time the weight is minimized. By using the joining process described above and a subsequent reaction firing, monolithic mirror structures with a diameter of up to 2500 mm can be produced, for example. After completion of the reaction firing, the mirror structure (a component body) based on a reaction-bonded composite material, consisting essentially of SiC and free Si, is optionallyPre-ground and then coated with SiC using chemical vapor deposition (CVD), with the layer thickness of the preferably crystalline SiC being between 150 μm and 2000 μm. The resulting CVD-coated mirror structure, particularly including the coated stiffening or rib structure, offers increased specific stiffness and strength compared to conventional RBSiC structures. Furthermore, the SiC surface applied by CVD, which is at least essentially defect- and pore-free, enables the realization of homogeneous optical surfaces with a root mean square roughness of less than 5 Ångströms and a polishing quality of P2 or P3. Frame structure manufactured using 3D printing.

[0053] A ceramic body based on a reaction-bonded composite material, consisting primarily of SiC and free Si, is manufactured using a powder-bed-based 3D printing process. This creates a geometrically complex frame structure, such as that required for coordinate measuring machines and in the field of semiconductor technology, particularly for EUV lithography systems. Compared to conventional subtractive manufacturing, the 3D printing process enables the creation of weight-reduced and even topologically optimized geometries. The use of the joining process described above, along with a subsequent reaction firing, also enables the production of particularly large, monolithic frame structures with edge lengths of up to 2000 mm.After the reaction firing is complete, the frame structure based on a reaction-bonded composite material consisting essentially of SiC and free Si is coated with SiC using chemical vapor deposition (CVD), with the layer thickness of the preferably crystalline SiC being between 150 μm and 1000 μm. The resulting CVD-coated frame structure offers increased specific stiffness and strength compared to conventionally manufactured RBSiC frame structures. In this way, the high demands placed on the stiffness and strength of such frame structures by applications in the field of EUV lithography and industrial metrology can be met in a particularly favorable manner. The SiC CVD coating is particularly suitable for frame structures for EUV lithography to prevent the separation of contaminants, particles, etc.from the substrate into the sensitive cleanroom process environment. The high tensile adhesive strength of the SiC layer on the RBSiC substrate surface is particularly advantageous in this context.

[0054] Further application examples

[0055] Examples of the use of the described invention are frame structures (so-called "optical benches") for mounting optical components, measuring systems, or the like. Further applications are in the field of mechanical engineering, e.g. pinions, air bearings, frame structures, etc. These components can then be used, for example, in CMM measuring systems (also: Coordinate Measuring Machine (English), or Koordinaten-Messsystem (German)), lithography systems, or similar precision machines. Another possibility is the use of the coated components for wafer chucks, wafer tables, or other components that come into contact with wafers. In addition to the higher mechanical strength, it is advantageous to rely on a high purity of the coating (> 99%, better > 99.9%) to prevent contamination of the wafers. This enables the use of an RBSiC base material with potentially significantly lower purity for the component body.

[0056] Further features, details, and advantages of the invention will become apparent from the wording of the claims and from the following description of an embodiment with reference to the drawings. They show:

[0057] Fig. 1 shows a component with a component body made of RBSiC and with SiC coating, namely a cantilever paddle;

[0058] Fig. 2 shows a component with a component body made of RBSiC and with SiC coating, namely a support roller for roller furnaces;

[0059] Fig. 3 shows a component with a component body made of RBSiC and with SiC coating, namely a plate with a bionic stiffening structure on the back;

[0060] Fig. 4 shows a component with a component body made of RBSiC and with SiC coating, namely a concave mirror; and

[0061] Fig. 5 a component with a component body made of RBSiC and with SiC coating, namely a frame structure.

[0062] Figs. 1 to 5 each show a component 1 with a component body 2 made of reaction-bonded silicon carbide (RBSiC), which has a body surface 3 completely coated with a coating 4. The continuously produced coating 4 of silicon carbide (SiC) has a layer thickness of at least 25 μm. Additionally, Figs. 1 to 5 each show a schematically illustrated section at the marked position AA, which contains the same reference numerals.

[0063] As can be seen, the body surface 3 has subregions oriented in different spatial directions, with the coating 4 being applied in subregions that point in all six spatial directions. According to Figs. 1 and 3 to 5, these include subregions of the body surface 3 that belong to a stiffening structure 5 of the component body 2 in the form of ribs, edges, or lattice structures. Only the support roller according to Fig. 2 does not have such stiffening structures.

[0064] The coating 4 preferably has the following further properties: the silicon carbide (SiC) of the coating 4 should have a purity of 98%, preferably 99% and particularly preferably 99.9%; the coating 4 should have a layer thickness of a maximum of 2 mm; the coating 4 should have a grain size of a maximum of 20 pm, preferably a maximum of 10 pm, more preferably a maximum of 7 pm, even more preferably a maximum of 4 pm and particularly preferably a maximum of 1 pm; the coating 4 should be a CVD layer or PVD layer.

[0065] The component body 2 preferably has the following additional properties: the component body 2 should have an average grain size of at least 10 pm, preferably at least 50 pm, more preferably at least 70 pm, even more preferably at least 90 pm, and particularly preferably at least 100 pm; and the component body 2 may well have a purity of less than 99%.

[0066] The left-hand section of component 1 shown in Fig. 1 is designed as a round bar or round tube. This section of component body 2 can be produced by continuous casting. The right-hand section of component 1 has a more complex structure with angles, stiffening structures 5, and a hole. This part of component body 2 can be a 3D-printed part. The two parts of component body 1 can then be joined by garnishing and a reaction firing of component body 2.

[0067] Component 1 shown in Fig. 1 is a workpiece holder for a diffusion furnace, in particular a so-called cantilever paddle. The coating 4 serves simultaneously as a corrosion protection layer, purification layer, strength layer, abrasion protection layer, and temperature resistance layer.

[0068] The component shown in Fig. 2 is a support roller for diffusion furnaces. The component body 2 is encapsulated by the coating 4. The peripheral area of ​​the coating 4 forms the running surfaces of the roller. The inner parts of the coating 4 serve primarily to encapsulate the component body 2 to prevent precipitation and to stiffen the component body 2.

[0069] The stiffening structure 5 according to Fig. 3 also has outer and inner regions of the coating 4. In this way, the clamps of the stiffening structure 5 are stabilized on the inside and outside with the coating 4.

[0070] In the concave mirror shown in Fig. 4, the coating of the rear stiffening structure 5 is particularly important. This contributes to the high thermal stability and dimensional accuracy of the concave mirror. The hollow surface of the concave mirror can optionally also be provided with the coating 4, as shown. The frame structure shown in Fig. 5 is a very complex component with extensive stiffening structures, stop surfaces, and attachment points.

[0071] The invention is not limited to one of the embodiments described above, but can be modified in many ways.

[0072] All information arising from the claims, the description and the drawing

[0073] Features and advantages, including design details, spatial arrangements and method steps, can be essential to the invention both individually and in a wide variety of combinations.

[0074] Reference symbols list Component Component body Body surface Coating Stiffening structure

Claims

Patent claims 1. Component (1) with a component body (2) made of a reaction-bonded silicon carbide (RBSiC), characterized in that the component body (2) has a body surface (3) coated at least partially with a coating (4), wherein the coating (4) consists of silicon carbide (SiC) with a layer thickness of at least 25 pm.

2. Component (1) according to claim 1, characterized in that the layer thickness is at least 50 pm, more preferably at least 100 pm, even more preferably at least 300 pm, and particularly preferably at least 500 pm.

3. Component (1) according to one of claims 1 or 2, characterized in that the body surface (3) has partial regions which are oriented in different spatial directions, wherein the coating (4) is arranged at least in partial regions which point in at least two of six spatial directions.

4. Component (1) according to claim 3, characterized in that the coating (4) is arranged in partial areas which point in at least three of the six spatial directions, preferably at least four of the six spatial directions, more preferably five of the six spatial directions, and particularly preferably in all six spatial directions.

5. Component (1) according to one of the preceding claims, characterized in that the coating (4) is arranged at least in a partial area of the body surface (3) which belongs to a stiffening structure (5) of the component body (2), for example a rib, a web, a strut, a tension rod, a compression rod, a honeycomb, an edge or a thickening.

6. Component (1) according to claim 5, characterized in that the stiffening structure (5) is a framework, a scaffold, or a bionic structure.

7. Component (1) according to one of the preceding claims, characterized in that the silicon carbide (SiC) of the coating (4) has a purity of 98%, preferably 99% and particularly preferably 99.9%.

8. Component (1) according to one of the preceding claims, characterized in that the coating (4) has a layer thickness of maximum 2 mm.

9. Component (1) according to one of the preceding claims, characterized in that the coating (4) has a grain size which is at most 20 pm, preferably at most 10 pm, more preferably at most 7 pm, even more preferably at most 4 pm and particularly preferably at most 1 pm.

10. Component (1) according to one of the preceding claims, characterized in that the component body (2) has an average grain size of at least 25 pm, preferably at least 50 pm, more preferably at least 70 pm, even more preferably at least 90 pm and particularly preferably at least 100 pm.

11. Component (1) according to one of the preceding claims, characterized in that the component body (2) has a purity of less than 99% silicon carbide (SiC).

12. Component (1) according to one of the preceding claims, characterized in that the component body (2) is at least partially a 3D-printed part or a green body of the component body (2) is at least partially based on a 3D-printed part.

13. Component (1) according to one of the preceding claims, characterized in that at least 70%, preferably 80%, more preferably at least 85%, even more preferably at least 90%, even more preferably at least 95%, and particularly preferably 100% of the body surface (3) is coated with the coating (4).

14. Component (1) according to one of the preceding claims, characterized in that the coating (4) is a CVD layer or PVD layer.

15. Component (1) according to one of the preceding claims, characterized in that the coating (4) is a corrosion protection layer.

16. Component (1) according to one of the preceding claims, characterized in that the coating (4) is formed coherently.

17. Component (1) according to one of the preceding claims, characterized in that the component (1) is a satellite carrier.

18. Component (1) according to one of claims 1 to 16, characterized in that the component is an antenna carrier.

19. Component (1) according to one of claims 1 to 16, characterized in that the component (1) is a roller for a continuous furnace or roller furnace.

20. Component (1) according to one of claims 1 to 16, characterized in that the component (1) is a component or workpiece holder of a diffusion furnace.

21. Component (1) according to one of claims 1 to 16, characterized in that the component (1) is a burner or radiant tube in a furnace.

22. Component (1) according to one of claims 1 to 16, characterized in that the component (1) is a sliding ring or a counter ring of a mechanical seal.

23. Use of a coating (4) made of silicon carbide (SiC) with a layer thickness of at least 25 pm for coating a body surface (3) of a component body (2) made of a reaction-bonded silicon carbide (RBSiC) of a component (1), for: a) increasing the hardness of the body surface (3) of the component (1); and / or b) increasing the strength of the component (1); and / or c) improving the chemical resistance of the body surface (3) of the component (1); and / or d) increasing the temperature resistance of the component (1).

24. A method for producing a component (1) comprising the following steps: a) producing a component body (2) by a. producing a powder-based green body made of silicon carbide (SiC) and a carbon source; b. carrying out a reaction firing with infiltration of the green body with silicon (Si) to produce a base body made of reaction-bonded silicon carbide (RBSiC); b) at least partially coating a body surface (3) of the component body (2) with a coating (4) made of silicon carbide (SiC) with a layer thickness of at least 25 pm.

25. Method according to claim 24, characterized in that the body surface (3) has partial areas which are oriented in different spatial directions, wherein the coating (4) is applied at least in partial areas which point in at least two of the six spatial directions.

26. Method according to one of claims 24 or 25, characterized in that the body surface (3) of the component body (2) intended for coating is at least partially or completely ground before coating.

27. Method according to one of claims 24 to 26, characterized in that the green body is manufactured by printing in a 3D printing process.

28. Method according to one of claims 24 to 27, characterized in that the coating is carried out by a CVD process or a PVD process.

29. Method according to one of claims 24 to 28, characterized in that the component (1) is designed according to one of claims 1 to 22.

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