Method for coating a surface of a metal main body

Abstract

The present invention relates to a method for coating at least one surface of a metal main body with a coating, wherein a powdery material containing at least one metal and at least one ceramic material is used to produce the coating, wherein the powdery material is at least partially melted and / or pressed together with the main body. According to the invention, the powdery material is a metal-ceramic composite powder having a metal proportion of at least 50% by volume and a ceramic proportion of not more than 50% by volume, in which ceramic particles are embedded in the metal matrix, wherein the metal matrix is an aluminium alloy, wherein in order to produce the metal-matrix ceramic composite powder, a metal-matrix ceramic composite material is produced by introducing ceramic particles into a molten metal matrix and stirring the resulting metal-matrix ceramic compound, and a semi-finished product is formed from the metal-matrix ceramic composite material, which semi-finished product is a melt or from which a melt is formed which is sprayed or atomised to form the metal-matrix ceramic composite powder, wherein the metal-matrix ceramic composite material is introduced into a container in a flowable state or is melted in a container, wherein the metal-matrix ceramic composite material remains in the container for a dwell time until a moulding compound or a moulded body having an lower region and an upper region is formed in the container, wherein the lower region has a different proportion of the ceramic particles than the upper region due to gravity and / or due to an electromagnetic field applied to or around the container, and wherein either the lower region or the upper region has a proportion of the ceramic particles of at least 15% by volume, but at most 50% by volume, and subsequently the upper region is separated from the lower region, wherein the upper or the lower region, whichever has the proportion of the ceramic particles of at least 30% by volume but at mo

Description

[0001] Method for coating the surface of a metallic substrate

[0002] The present invention relates to a method for coating at least one surface of a metallic base body with a coating, wherein a powdered material containing at least one metal and at least one ceramic material is used to produce the coating, wherein the powdered material is at least partially melted and / or pressed with the base body.

[0003] German patent application DE 44 13 306 C1 describes a method for applying a reinforcing layer to a component using high-speed flame spraying, in which a powder mixture of a reinforcing particle powder and a metal alloy powder is used. The powder mixture is melted during the high-speed flame spraying process. In the reinforcing layer formed on the component, the reinforcing particles are embedded in the metal matrix.

[0004] German patent application DE 100 45 049 A1 states that, to form a brake pad, a powder mixture consisting of an aluminum alloy powder and an aluminum-reactive ceramic powder can be applied to a metallic support body and pressed onto the support body using a pressure of 1 to 100 MPa at a reaction temperature sufficient to melt the aluminum powder particles. The metallic matrix formed on the support body contains at least 20 vol% aluminide in which finely dispersed ceramic particles are present.

[0005] The publication DE 196 01 793 A1 describes a flame spraying process in which a powdered composite material containing aluminium, iron, silicon and hexagonal boron nitride is used.

[0006] The subsequently published document DE 102023 119346 A1 describes a process for producing a metal matrix composite powder in which ceramic particles are introduced into a molten metal matrix, forming a metal matrix composite material in the form of a melt. This melt remains in a container until, due to gravity, areas with different ceramic particle fractions have formed within it. These areas are then separated. A semi-finished product is then formed from one of these areas, which has a ceramic particle fraction of at least 30 wt.%, and subsequently atomized or sprayed.

[0007] In publication CN 1 02441 643 A, a mold is formed in sand and then filled with molten metal. After cooling, the casting is subjected to a thermal spray treatment with powder to form a coating. The sprayed surface can be roughened, degreased, and / or preheated beforehand.

[0008] Publication CN 1 15989 103 A deals with the production of an alloy powder containing copper, nickel, and cobalt from a raw material obtained from shredded lithium-ion batteries. The raw material is melted, and then valuable metals with low oxygen affinity, such as Cu, Ni, and Co, are separated from less valuable metals with high oxygen affinity, such as aluminum.

[0009] German patent application DE 10 2008 035 849 A1 describes a method for coating the braking surfaces of brake discs or other friction elements of brakes, and a friction element for a brake. In this method, a coating is applied to a roughened surface of a steel brake disc by high-speed flame spraying of a powdered material. The powdered material used is a ceramic-metal composite consisting of more than 80% ceramic and less than 20% metal. The ceramic component is oxide-free, such as tungsten carbide. The high ceramic content is intended to achieve high mechanical strength in the coating produced by this known method.

[0010] The metal component is either a cobalt or a nickel alloy, with cobalt intended to improve the wear resistance of the ceramic-metal composite. In the known process, the use of nickel as a metal component aims to improve adhesion to the friction element and adhesion within the applied ceramic-metal composite. However, practical experience has shown that even when nickel is used as the metal component, the wetting of the friction element with the ceramic-metal composite is insufficient in the known process because the high ceramic content prevents bonding to the friction element material.

[0011] Furthermore, regardless of the metal component used, the high ceramic content of the ceramic-metal composite leads to a high porosity of the coating applied to the friction element, which results in a reduction of its wear resistance.

[0012] Using the known method, only relatively heavy brake discs can be produced due to the use of steel as the material for the base body of the brake disc.

[0013] Another disadvantage of the known method is that the high ceramic content in the ceramic-metal composite material leads to high wear of the tool used for coating production.

[0014] The object of the present invention is therefore to provide a method for coating a braking and / or friction surface of a metallic base body, resulting in high wear resistance of the coating and thus of the component, wherein the coating should adhere very well to the base body. A light metal should be usable as the material for the base body, so that the coated component has a low weight. Furthermore, only minimal wear should occur on the tool used for coating.

[0015] The problem is solved by a method for coating at least one surface of a metallic base body with a coating, wherein a powdered material containing at least one metal and at least one ceramic material is used to produce the coating, wherein the powdered material is at least partially melted and / or pressed with the base body, wherein the powdered material is a metal-ceramic composite powder with a metal content of at least 50 vol.% and a ceramic content of at most 50 vol.%, in which ceramic particles are embedded in the metal matrix, wherein the metal matrix is ​​an aluminum alloy.wherein the metal matrix ceramic composite powder is produced by introducing ceramic particles into a molten metal matrix and stirring the resulting metal matrix ceramic mass, and a semi-finished product is formed from the metal matrix ceramic composite material, which is a melt or from which a melt is formed, which is atomized or sprayed to form the metal matrix ceramic composite powder, wherein the metal matrix ceramic composite material is brought into a container in a flowable state or is melted in a container, wherein the metal matrix ceramic composite material remains in the container for a residence time until a molding mass or a molded body with a lower region and an upper region is formed in the container,wherein the lower region has a different proportion of ceramic particles than the upper region due to gravity and / or an electromagnetic field applied to or around the container, and wherein either the lower region or the upper region has a proportion of ceramic particles of at least 15 vol.% but not more than 50 vol.%, and wherein the upper region is subsequently separated from the lower region, wherein the portion of the upper or lower region that has a proportion of ceramic particles of at least 30 vol.% but not more than 50 vol.% forms the semi-finished product or is formed or pre-formed into the semi-finished product, wherein the coating process comprises diffusion welding, laser powder deposition welding, electron beam cladding, cold gas spraying, (high-speed) flame spraying, or a sintering process.in which the metal matrix ceramic composite powder is used to form the coating.

[0016] In contrast to the prior art known from publication DE 10 2008 035 849 A1, in which a powdered ceramic-metal composite material is used for coating, which consists predominantly of ceramic, whereby the metal is surrounded by the ceramic, the present method uses a metal matrix ceramic composite powder for coating, which has a maximum of 50 vol.% ceramic components, wherein these ceramic components, which are present as ceramic particles, are embedded in the metal matrix, i.e., completely surrounded by the metal of the metal matrix.

[0017] The metal matrix ceramic composite powder used according to the invention is predominantly a composite powder in which the ceramic particles are bonded to the aluminum alloy, meaning that the metal matrix and the ceramic are present in one and the same powder particle. This means that the metal matrix ceramic composite powder is not a mixture of ceramic and metal particles. The ceramic particles in the metal matrix ceramic composite powder act as reinforcing phases.

[0018] This means that during the coating process only the aluminum alloy and not the ceramic is in direct contact with the substrate to be coated, resulting in particularly good wetting of the substrate surface with the metal matrix ceramic composite powder and very good adhesion of the coating made of the metal matrix ceramic composite powder to the substrate.

[0019] Furthermore, the method according to the invention, through the use of the metal matrix ceramic composite powder, results in a significantly lower porosity of the applied coating than is the case with the method described in German publication DE 10 2008 035 849 A1. In the metal matrix ceramic composite powder used according to the invention, adjacent powder particles are in contact with each other, creating a metallurgical bond between the powder particles made of the same material during the formation of the coating, which involves at least partial melting and / or pressing with the substrate.

[0020] Accordingly, the inventive method results in a highly stable, wear-resistant coating despite the fact that the metal matrix ceramic composite powder used in the inventive method contains comparatively significantly less ceramic material than the ceramic-metal composite material used in publication DE 102008035849 A1.

[0021] Furthermore, the closely spaced aluminum alloy particles of the metal matrix ceramic composite powder, which enclose the ceramic particles, allow forces acting on the coating to be absorbed throughout. Unlike the method described in German patent DE 10 2008 035 849 A1, the metal of the metal matrix does not need to flow into the spaces between the ceramic particles. Therefore, the present invention achieves a higher mechanical strength of the coating with the same or even a lower ceramic content than in the prior art.

[0022] The coating forms a protective layer on the substrate. This protective layer can be a mechanical protective layer, such as a wear-resistant layer or an armor coating. Depending on the substrate material, the protective layer can also provide thermal protection, corrosion protection, and / or other types of protection.

[0023] The coating can have a thickness ranging from 100 pm to 10 mm. That is, the coating can be a few hundred micrometers thick. However, it can also be several millimeters thick.

[0024] The coating can be applied to the top and / or bottom surface of the base body. Alternatively, the coating can also be applied to an edge surface of the base body. In the latter case, the coating can be as thick as the base body.

[0025] The coating preferably contains no chromium, no nickel and no tungsten carbide, as these substances are harmful to health if the coating is abrasioned.

[0026] Particularly good adhesion of the coating to the base body is achieved if the base body is heated at least locally during the coating process and not cooled.

[0027] Particularly energy-efficient operation can be achieved if, in one embodiment of the inventive method, the base body is cast or forged and the coating is applied to the base body while it is still warm from the casting or forging process. In this way, the heat from the preceding casting or forging process step can be used for an advantageous coating.

[0028] In diffusion welding, the metal matrix ceramic composite powder is placed in a mold. The base material is then placed in the mold, followed by more metal matrix ceramic composite powder. The mold is then closed, pressing the materials inside against each other. The mold and its contents are then placed in a hot oven for several hours at a temperature below the liquidus temperature of the aluminum alloy in the metal matrix ceramic composite powder. During this process, thin intermetallic phases form at the material interfaces due to the thermal influence.

[0029] In laser powder deposition welding, each particle of the metal matrix ceramic composite powder is melted by means of a laser and applied in molten form to the base body, which is locally preheated according to the path of the laser beam, where a bond is created with the material of the base body.

[0030] In electron beam cladding, each particle of the metal matrix ceramic composite powder is melted by means of an electron beam and applied in molten form to the base body, which is locally preheated according to the path of the electron beam, where a bond is created with the material of the base body.

[0031] For example, a high-speed flame sprayer can be used as a flame sprayer.

[0032] One sintering process that can be considered is Spark Plasma Sintering (SPS), in which the metal matrix ceramic composite powder is first placed into a mold. Then the base material is placed into the mold, followed by more metal matrix ceramic composite powder. The mold is then closed, pressing the materials together. The base material and finally more metal matrix ceramic composite powder are placed into the mold, which is then closed, pressing the materials together.Subsequently, an electric current is passed through the dies of the mold into the component, which contains the base body and the metal matrix ceramic composite powder, for a few minutes. This heats up due to the resistance heat, creating a bond between the material of the metal matrix ceramic composite powder and the material of the base body.

[0033] By introducing the ceramic particles into the molten metal matrix and stirring the resulting metal matrix-ceramic mixture, a force-fit and form-fit bond is achieved between the ceramic particles and the metal matrix. The force-fit bond results from the ceramic particles being "clamped" by the higher coefficient of thermal expansion of the metal matrix, while the material bond results from the wetting of the ceramic particles by the metal matrix. This achieves particularly good adhesion of the metal matrix to the ceramic particles in the metal matrix composite material, which is maintained in the metal matrix-ceramic composite powder.

[0034] The process according to the invention is characterized in that the concentration of the ceramic particles reliably coated with the metal matrix material in the melt is increased before atomization or spraying compared to other processes. This is achieved here by introducing the stirred melt containing the ceramic particles into the container, in which a specific distribution of the ceramic particles results depending on the density of the ceramic particles.

[0035] If the ceramic particles are heavier than the metal matrix, a majority of the ceramic particles will sink to the bottom of the container during the residence time. If the ceramic particles are lighter than the metal matrix material, they will primarily accumulate in the upper part of the container during the residence time.

[0036] By subsequently separating the upper and lower regions of the molded body or molded material formed in the container, the region containing at least 15% by volume but no more than 50% by volume of ceramic particles—that is, the region with the highest concentration of ceramic particles—can be selected as a semi-finished product and used for further processing. In this further processing, either the upper or the lower region is used directly as a semi-finished product for the subsequent atomization or spraying, or it is reshaped or pre-formed into the semi-finished product, provided that the settling of the ceramic particles occurs in a container designed as a casting mold.If the ceramic particles settled in a crucible-shaped container and the material with the higher concentration of ceramic particles is still molten, it can be poured into a mold to solidify. The remaining portion with a lower concentration of ceramic particles can serve as the basis for producing the composite melt again or be used in a process where a lower concentration of ceramic particles is desired.

[0037] Based on the molded body / molding compound formed in the container, the separated portion of the molded body with the higher ceramic particle content can be remelted during subsequent processing. If a molded body has formed in the container, the resulting melt serves as a semi-finished product and is atomized or sprayed to form the metal matrix ceramic composite powder. Alternatively, the liquid molding compound with the higher ceramic particle content can be poured off to solidify into a molded body, without the need for subsequent division of the semi-finished product.

[0038] In the process according to the invention, the semi-finished product can be completely or partially melted again before atomizing or spraying.

[0039] The remelting of the semi-finished product and the immediately subsequent atomization or atomization can occur gradually. In such a case, it is advantageous if the semi-finished product is rod- or wire-shaped. This can be achieved in the process according to the invention by appropriate reshaping or primary forming of the semi-finished product.

[0040] Alternatively, during further processing, the flowable molding compound can be kept in a molten state from the container and at least partially atomized or sprayed immediately as a semi-finished product.

[0041] In an advantageous embodiment of the present invention, the separation of the upper and lower regions of a molded body formed in the container can be achieved mechanically, for example by breaking or splitting. If the molding compound in the container has not yet solidified, in another advantageous embodiment of the present invention, the upper and lower regions can be separated by casting. For example, a drain can be provided at the bottom of the container through which the lower region of the molding compound can drain. If the lower region has a higher ceramic particle content than the upper region, the molding compound draining from the bottom can be kept hot and immediately atomized to form the metal matrix ceramic composite powder.However, the outgoing lower section can also flow into, for example, a rod-shaped casting mold, solidify into the semi-finished product, and then the semi-finished product can be atomized or sprayed into the metal matrix ceramic composite powder.

[0042] Alternatively, the upper area can be extracted from the lower area using a suction pipe, poured off using a tilting device, or skimmed off mechanically or manually.

[0043] The coated surface of the base body preferably forms a braking or friction surface of a component. The component can be a disc clutch comprising two metallic base bodies, each of which is coated on its facing surfaces.

[0044] Preferably, the aluminium alloy is composed of more than 80 wt.% aluminium.

[0045] The proportion of ceramic particles in the metal matrix ceramic composite powder, depending on the specific application and the size of the respective ceramic particles, is preferably 15 to 50 vol.%.

[0046] Preferably, the ceramic particles are formed from at least one ceramic material selected from a group of ceramic materials comprising aluminum oxide, silicon carbide, boron nitride, titanium carbide, and zirconium oxide. In advantageous embodiments of the present invention, the metallic base body is formed from aluminum, an aluminum casting alloy, gray cast iron, or steel.

[0047] The metallic base body can be made from a pre-formed wrought alloy.

[0048] For example, the metallic base body is a brake disc and the coating is a brake surface coating of the brake disc.

[0049] In another advantageous embodiment of the invention, the coating adjoins an edge side of the base body and has the same thickness as the base body.

[0050] Preferred embodiments of the present invention are explained in more detail below with reference to the figures, wherein

[0051] Figures 1a to 1f schematically show steps of an embodiment of the inventive method with mechanical separation of areas of a molded body produced in a container;

[0052] Figures 2a to 2e schematically show steps of a further embodiment of the inventive method with casting-technical separation of areas of a molding compound produced in a container;

[0053] Figures 3a to 3d schematically show steps of a further embodiment of the inventive method with casting-technical separation of areas of a molding compound produced in a container and a powder particle filtration;

[0054] Figure 4 schematically shows a component in the form of a composite brake disc, manufactured using the method according to the invention, in a sectional side view; Figure 5 schematically shows a component in the form of a disc clutch, manufactured using the method according to the invention, in a sectional side view;

[0055] Figure 6 schematically shows another component produced using the inventive method in a cutaway side view;

[0056] Figure 1 shows a sectioned side view of an area of ​​a component manufactured according to the invention; and

[0057] Figure 8 shows a photograph of powder particles of a metal matrix ceramic composite powder used in the present invention.

[0058] Figures 1a to 1f schematically show steps of an embodiment of the method according to the invention. In step 1a, a metal matrix-ceramic composite material 1 is first produced. In this step, ceramic particles 3 are introduced into a metal matrix 2, which is an aluminum alloy matrix and is present in a device 1, by stirring with at least one stirrer 4. In the embodiment shown, the ceramic particles are made of aluminum oxide, but in other embodiments of the present invention, they can be made of a different ceramic material, such as silicon carbide, boron nitride, titanium carbide, or zirconium oxide.

[0059] As shown in Figure 1a, the melt can flow in an inclined channel 5. As further shown in Figure 1a, at least one basin 6 can be formed in the channel 5, into which the molten metal matrix 2 with the ceramic particles 3 embedded therein flows, and into which the respective stirrer 4 is immersed for stirring. At the end of the channel 5, a metal matrix-ceramic composite material 7 is present, in which the ceramic particles 3 are homogeneously embedded in the metal matrix 2 and are completely surrounded by the metal matrix 2. In the illustrated embodiment, the metal matrix-ceramic composite material 7 is still flowable at the end of the channel 5, i.e., in the illustrated embodiment, a so-called AMC (aluminum matrix composite) melt. In another embodiment of the invention, the metal matrix ceramic composite material 7 is cooled to form one or more ingots, which are subsequently remelted.

[0060] The flowable metal matrix ceramic composite material 7 is poured into a preferably heatable and / or insulated container 8, as shown schematically in Figure 1b. If the metal matrix ceramic composite material 7 is in the form of at least one ingot, it is melted in a heated container 8.

[0061] Container 8 is shown schematically in the figures and in reality preferably has a significantly greater depth t than width b. For example, the width b can be 10 mm and the depth 1700 mm.

[0062] The molten metal matrix ceramic composite material 7 remains in the container 8 for a residence time. During this time, the metal matrix ceramic composite material 7 can be kept in a molten state in the container 8 at a temperature above the solidus temperature. Since, as shown in the illustrated embodiment, the ceramic particles 3 have a greater mass than the metal matrix 2, they settle in a lower region 81 within the container 8 during the residence time. That is, they sink towards the bottom of the container 8. Within the upper region 82 of the container 8, the proportion of ceramic particles 3 is correspondingly lower than in the lower region 81. The lower region 81 forms a highly particle-reinforced metal matrix composite material melt, while the upper region 82 forms a nearly unreinforced to unreinforced metal matrix or metal matrix alloy.In the lower region 81, the proportion of ceramic particles 3 is at least 15 vol.%, but at most 50 vol.%. In other embodiments of the present invention, not shown, in which the ceramic particles 3 are lighter than the metal matrix 2, the proportion of ceramic particles 3 in the upper region 82 is higher than in the lower region 81, in this case at least 15 vol.%, but at most 50 vol.%. In the process step shown in Figure 1b, the metal matrix composite material 7 remains in the container 8 until it has solidified into a shaped body 10. The shaped body 10 is then removed from the container 8, as shown schematically in Figure 1c. The shaped body 10 can, for example, have the shape of a cylinder or a rod.

[0063] As schematically illustrated in Figure 1d, the upper region 82 is subsequently mechanically separated from the lower region 81 of the molded body 10. This mechanical separation can be carried out using a suitable separation method, for example by breaking the molded body 10, e.g., by snapping the lower region 81 off from the upper region 82, or by using a tool.

[0064] The separated area containing at least 15 vol.% but no more than 50 vol.% of the ceramic particles 3, i.e., in the illustrated embodiment, the separated lower area 81, is then processed into a semi-finished product 811 in the form of a rod or wire, as schematically shown in Figure 1e. This can be achieved by forming processes such as rolling, rotary swaging, or extrusion, or by primary forming processes such as casting. The resulting rod or wire has, for example, a diameter in the range of 1 to 10 mm. Since forming processes produce rods or wires of limited length, it is advantageous for the continuous execution of the subsequent process steps if several such rods or wires are joined, for example, by friction welding or laser welding to form a longer rod or wire, which is then used as the semi-finished product 811.

[0065] The semi-finished product 811 has the advantage that the concentration of the ceramic particles 3 is precisely defined. In the illustrated embodiment, the proportion of ceramic particles 3 in the semi-finished product 811 is at least 15 vol.%, for example at least 20 vol.%, but at most 50 vol.%.

[0066] The semi-finished product 811 is atomized in a subsequent process step, which is shown schematically in Figure 1f. A rod or wire feeding method is used for this purpose. In this process, a beginning of the semi-finished product 811, i.e., in this case, a rod or wire end, is fed continuously or in pulses to a melting device 11, which can be, for example, an induction coil or a plasma torch. The respective rod or wire end is melted by the melting device 11. The rod- or wire-shaped semi-finished product 811 is thus only melted locally and fed (semi-)continuously. This melting of the semi-finished product 811 can be carried out in a protective gas atmosphere.

[0067] The resulting semi-finished product melt 811' is atomized directly after melting in an atomizer 12, such as a cyclone separator, assisted by a jet of pressurized gas or water. In the atomizer 12, also referred to as an atomizer, pressurized gas or water atomization of the melt thus takes place.

[0068] Alternatively, the semi-finished product melt 811' can be atomized.

[0069] Alternatively, ingots of metal matrix ceramic composite material 8 can be melted in the container. The resulting molten metal matrix composite material 7 is then allowed to stand in the container 8 for a certain period and is subsequently skimmed off from the top of the container 8, provided the ceramic particles 3 have a greater mass than the metal matrix 2. The skimmed melt corresponds to the upper region 82 described above. The melt remaining in the container 8, which is more concentrated with ceramic particles 3 than the skimmed melt and corresponds to the lower region 81 described above, is then poured into an unheated mold, where it solidifies. After a certain residence time in the container 8, a concentration maximum of ceramic particles 3 is reached in the melt with the higher concentration of ceramic particles 3.Accordingly, the mold into which this melt is poured contains a material highly reinforced with ceramic particles 3, which can then be remelted and subsequently atomized or sprayed. Alternatively, the flowable molding compound with the high ceramic particle content can also be directly atomized or sprayed.

[0070] The metal matrix ceramic composite powder 14 produced during atomization or spraying contains a high proportion of ceramic particles 3, at least 15 vol.% but no more than 50 vol.%. A single metal matrix ceramic composite powder particle may contain one or more of these ceramic particles 3. However, the metal matrix ceramic composite powder 14 may also contain only metal powder particles consisting of the metal matrix 2. The proportion of the aluminum alloy in the metal matrix ceramic composite powder 14 is at least 50 vol.%. The metal matrix ceramic composite powder 14 is collected, for example, in a powder collection canister 13.

[0071] Figures 2a to 2e schematically show steps of a further embodiment of the method according to the invention. As in the process step shown in Figure 1a, a metal matrix-ceramic composite material 1 is first produced in the process step shown in Figure 2a. Here, ceramic particles 3 are introduced into a molten metal matrix 2 in a device 1 by stirring with at least one stirrer 4. As shown in Figure 2a, the melt can flow in an inclined channel 5. As further shown in Figure 2a, at least one basin 6 can be formed in the channel 5, into which the molten metal matrix 2 with the ceramic particles 3 introduced therein flows and into which the respective stirrer 4 is immersed for stirring.At the end of the channel 5, a metal matrix ceramic composite material 7 is present, in which the ceramic particles 3 are homogeneously incorporated into the metal matrix 2 and are completely surrounded by the metal matrix 2.

[0072] In the process step shown in Figure 2b, the flowable metal matrix ceramic composite material 7 is fed into a container 8', where it is kept flowable by continuous heating and / or by delaying cooling. Preferably, the molding compound is even superheated in the container 8'. The metal matrix ceramic composite material 7 remains in the container 8' for a certain residence time. If the ceramic particles 3 have a greater mass than the metal matrix 2, the ceramic particles 3 sink to a lower region 81' of the molding compound formed in the container 8'. Thus, sedimentation of the ceramic particles 3 coated with the metal matrix material occurs in the lower region 81'. In the lower area 81 ' the proportion of ceramic particles 3 is therefore higher than the proportion of ceramic particles 3 of an upper area 82' of the molding compound in the container 8' located above the lower area 81 '.In the lower region 81', the proportion of ceramic particles 3 is at least 15 vol.%, but no more than 50 vol.%. Calculations and experiments on the sedimentation of the ceramic particles 3 coated with the metal matrix 2 allow for the calculation of the proportion of ceramic particles 3 as a function of a height h within the molding compound in the container 8' and the residence time of the metal matrix-ceramic composite material 7 in the container 8'. This makes it possible, for example, to determine the size of the lower region 81' and the upper region 82', i.e., how much of the melt can be drained downwards or how much of the melt must be removed from the top.

[0073] The lower region 81' can, for example, comprise half, a third, or a quarter of the total molding compound contained in the container 8'. In the lower region 81', the proportion of ceramic particles 3 can be almost twice as high as in the upper region 82'.

[0074] In a subsequent process step, schematically depicted in Figure 2c, the lower section 81' is drained from the container 8'. In the illustrated embodiment, the melt of the upper section 82', which is only weakly reinforced with the ceramic particles 3, is retained in the container 8'. The drained lower section 81' of the molding compound then flows, as shown in Figure 2d, into a crucible 15 of a continuous casting apparatus 16.

[0075] Alternatively, the upper section 82' can also be skimmed from the container 8' before the lower section 8T is drained into the crucible 15.

[0076] In the crucible 15, the material drained from the container 8' is reheated. The reheated material then emerges from an outlet of the crucible 15. This emergence occurs so slowly that the drained molding compound solidifies upon exiting the crucible 15.

[0077] If ceramic particles 3 with a lower mass than the metal matrix 2 are used in the process according to the invention, more ceramic particles 3 are present in an upper region 82' within the container 8' after the residence time. In this case, the lower region 8T with the lower concentration of ceramic particles is first drained from the container 8', and then the upper region 82' is drained into the crucible 15. The outlet of the crucible 15 is connected to a mold 23, which may be cooled. Using the continuous casting device 16, a molded part produced from the lower region 8T of the molding compound after cooling is formed into a rod-shaped or other special-shaped semi-finished product 812 with a cross-section in the range of 1 mm to 2 mm. The semi-finished product 812 is removed mechanically via rollers 24 in a removal direction Z.

[0078] The semi-finished product 812 is atomized in a subsequent process step, shown schematically in Figure 2e. For this purpose, one end of the semi-finished product 812 is locally and continuously melted in a melting device 11, which can be, for example, an induction coil or a plasma torch. The resulting semi-finished product melt 812' is atomized in an atomizer 12, such as a cyclone separator, assisted by a pressurized gas or water jet.

[0079] Alternatively, the semi-finished product melt 812' can, for example, be atomized drop by drop.

[0080] The resulting metal matrix ceramic composite powder 14 contains a high proportion of ceramic particles 3, at least 15 vol.%, preferably at least 30 vol.%, but at most 50 vol.%. The proportion of ceramic particles 3 in the metal matrix ceramic composite powder 14 can also be at least 35 vol.%, at least 40 vol.%, or at least 45 vol.%, but not more than 50 vol.%. The proportion of aluminum alloy in the metal matrix ceramic composite powder 14 is at least 50 vol.%. One or more ceramic particles 3 can be contained within a single metal matrix composite powder particle. Nearly every, i.e., at least 90% of the powder particles of the metal matrix ceramic composite powder 14 contains at least one ceramic particle 3. The metal matrix ceramic composite powder 14 can also contain metal powder particles consisting solely of the metal of the metal matrix 2.

[0081] The metal matrix ceramic composite powder 14 is collected in a powder collection canister 13. Figures 3a to 3d schematically show steps of a further embodiment of the process according to the invention. As in the process steps of Figures 1a and 2a, a metal matrix ceramic composite material 1 is first produced in the process step shown in Figure 3a. Here, ceramic particles 3 are introduced into a metal matrix 2, which is present in the form of a melt, in a device 1 by stirring with at least one stirrer 4. As shown in Figure 3a, the melt can flow in an inclined channel 5. As further shown in Figure 3a, at least one basin 6 can be formed in the channel 5, into which the metal matrix material, present in the form of a melt, flows with the ceramic particles 3 introduced therein, and into which the respective stirrer 4 is immersed for stirring.At the end of the channel 5, a metal matrix ceramic composite material 7 is present, in which the ceramic particles 3 are homogeneously incorporated into the metal matrix 2 and are completely surrounded by the metal matrix 2.

[0082] In the process step shown in Figure 3b, the flowable metal matrix ceramic composite material 7 is fed into a container 8', where it is kept flowable by continuous heating of the container 8'. The metal matrix ceramic composite material 7 remains in the container 8' for a certain residence time. If the ceramic particles 3 have a greater mass than the metal matrix material, the ceramic particles 3 sink to a lower region 81' of a molding compound formed in the container 8'. In the lower region 81', the proportion of ceramic particles 3 is therefore higher than the proportion of ceramic particles 3 in an upper region 82' of the molding compound located above the lower region 81' in the container 8'. In the lower region 81', the proportion of ceramic particles 3 is at least 15 vol%, but at most 50 vol%.

[0083] As shown schematically in Figure 3c, the still-flowable metal matrix ceramic composite material 7 is poured directly into a cold-walled crucible 17 via an outlet of the container 8'. The cold-walled crucible 17 is, for example, a water-cooled copper crucible. The metal matrix ceramic composite material 7 is kept liquid in the cold-walled crucible 17 by means of induction heating or a plasma torch. Due to the water cooling of the wall of the cold-walled crucible 17, a so-called "skull" forms on the surface of the metal matrix composite material 7, which protects the metal matrix composite material 7 from contamination by dissolved copper. The metal matrix ceramic composite material 7 in the cold-walled crucible 17 forms a semi-finished product 813 in the form of a melt. This semi-finished product 813 is fed directly into an atomizer 12, such as a cyclone separator, supported by a pressurized gas or water jet, and atomized by it.Alternatively, the semi-finished product 813 can be atomized.

[0084] The resulting metal matrix ceramic composite powder 14 contains a high proportion of ceramic particles 3, at least 15 vol.% but no more than 50 vol.%. A single metal matrix ceramic composite powder particle may contain one or more of these ceramic particles 3. However, the metal matrix ceramic composite powder 14 may also contain only metal powder particles consisting solely of the metal from the metal matrix 2.

[0085] The metal matrix ceramic composite powder 14 is preferably collected in a powder collection canister 13.

[0086] In a subsequent process step, shown schematically in Figure 3d, the produced metal matrix ceramic composite powder 14 is passed through a filter unit 20 by an airflow 19 generated by an air nozzle 18. The filter unit 20 also includes an infrared camera 23. The airflow 19 agitates the powder particles of the metal matrix ceramic composite powder 14, with the lighter powder particles rising and the heavier powder particles falling. If the ceramic particles 3 are heavier than the metal matrix material, then the ceramic particles 3 coated with the metal matrix 2 are also heavier than pure metal powder particles that may also be present in the metal matrix ceramic composite powder 14. The infrared camera 23 detects the thermal behavior of the powder particles, which differs between pure metal powder particles and powder particles containing ceramic particles 3.Depending on the density and thermal behavior of the powder particles, they are then separated from one another, for example, by allowing the pure metal powder particles 14' to fall through a perforated bottom 21 of the filter device 20, be collected in a collection container 22 located below, and thereby be separated from the ceramic-reinforced powder particles. The method according to the invention can also have further embodiments. For example, individual process steps of the embodiments described above can be adopted or exchanged by one of the other embodiments.

[0087] Figure 4 schematically shows a component 100, which was manufactured using the method according to the invention, in a cut side view.

[0088] Component 100 has a base body 101 made of a light metal. In the illustrated embodiment, the base body 101 is made of aluminum, but in other embodiments of the present invention it can also be made of gray cast iron.

[0089] In the illustrated embodiment, the base body 101 is disc-shaped. More precisely, in the illustrated embodiment, the base body 101 is a brake disc. However, the base body can also be another wear-prone part of a component 100. In the illustrated embodiment, the base body 101 has a surface 101a, 101b on each side, on which a coating 102a, 102b is applied. The surface of each coating 102a, 102b forms a braking or friction surface of the brake disc, which interacts with a brake pad when the brake disc is in use. In other embodiments of the invention, the coating 102a or 102b can also be provided on only one surface 101a, 101b of the base body 101.

[0090] The coating 102a, 102b is each formed from a metal matrix ceramic composite powder 14 with a metal content of at least 50 vol.% and a ceramic content of at most 50 vol.%, wherein the metal matrix ceramic composite powder 14 was at least partially melted and / or pressed with the base body 101, depending on the coating technology.

[0091] Figure 5 schematically shows a component 100' in the form of a disc coupling, manufactured using the method according to the invention, in a sectional side view. The component 100' is a disc coupling. The component 100' is formed from two base bodies 101, 101', each of which is provided with the coating 102a, 102b on its mutually facing surfaces 101a, 101b.

[0092] Figure 6 schematically shows a further component 100” produced using the method according to the invention, in a sectional side view. The component 100” has a base body 101” which has a surface 101c on its edge side, provided with a coating 102c. The coating 102c is formed from a metal matrix ceramic composite powder 14 with a metal content of at least 50 vol.% and a ceramic content of at most 50 vol.%, wherein the metal matrix ceramic composite powder 14 was at least partially melted and / or pressed with the base body 101, depending on the coating technology. The coating 102c has a thickness d that corresponds to the thickness of the base body 101”.

[0093] Figure 7 shows a sectioned side view of a region of a component 100 produced according to the invention. A coating 102a formed on a base body 101 is visible. A metal matrix 2, which in the example shown is an aluminum alloy, is also visible, in which ceramic particles 3, made of SiC in the example shown, are embedded.

[0094] Figure 8 shows a photograph of powder grains of a metal matrix ceramic composite powder 14 used in the present invention. In each powder grain, at least one ceramic particle 3 is embedded in a metal matrix 2.

Claims

Patent claims 1. A method for coating at least one surface (101a, 101b, 101c) of a metallic substrate (101, 101', 101") with a coating (102a, 102b, 102c), wherein a powdered material containing at least one metal and at least one ceramic material is used to produce the coating (102a, 102b, 102c), wherein the powdered material is at least partially melted and / or pressed with the substrate (101, 101', 101"), wherein the powdered material is a metal matrix ceramic composite powder (14) with a metal content of at least 50 vol.% and a ceramic content of at most 50 vol.%, in which ceramic particles (3) are embedded in the metal matrix (2), wherein the metal matrix (2) is an aluminum alloy.wherein the metal matrix ceramic composite powder (14) is produced by introducing ceramic particles (3) into a molten metal matrix (2) and stirring the resulting metal matrix ceramic mass, a metal matrix ceramic composite material (7) is produced, and a semi-finished product (811, 812, 813) is formed from the metal matrix ceramic composite material (7), which is a melt or from which a melt is formed that is atomized or sprayed to form the metal matrix ceramic composite powder (14), wherein the metal matrix ceramic composite material (7) is brought into a container (8, 8') in a flowable state or is melted in a container (8, 8'), wherein the metal matrix ceramic composite material (7) Residence time in the container (8, 8') remains until a molding mass or a molded body (10) with a lower region (81, 81') and an upper region (82, 82') forms in the container (8), wherein the lower region (81,81 ') has a different proportion of the ceramic particles (3) due to gravity than the upper region (82, 82'), and wherein either the lower region (81, 81 ') or the upper region (82, 82') has a proportion of the ceramic particles (3) of at least 15 vol.%, but at most 50 vol.%, and subsequently the upper region (82, 82') is separated from the lower region (81, 81 '), wherein that part of the upper or the lower region (82, 82'; 81, 81 ') which has a proportion of the ceramic particles (3) of at least 15 vol.%, but at most 50 vol.%, forms the semi-finished product (811, 812, 813) or is formed or pre-formed to form the semi-finished product (811, 812, 813), characterized in that the coating a Diffusion welding, laser powder deposition welding, electron beam cladding, cold gas spraying, a (high-, comprising speed) flame spraying or a sintering process, in each case the metal matrix ceramic composite powder (14) is used to form the coating (102a, 102b, 102c).

2. Method according to claim 1, characterized in that the base body (101, 101 ', 101“) is heated at least locally and not cooled during coating.

3. Method according to claim 1, characterized in that the base body (101, 101 ', 101") is cast or forged and the coating is carried out on the base body (101, 101 ', 101") which is still warm from the casting or forging.

4. Method according to one of the preceding claims, characterized in that the aluminium alloy is composed of aluminium to more than 80 wt.%.

5. Method according to one of the preceding claims, characterized in that the ceramic particles (3) are formed from at least one ceramic material selected from a group of ceramic materials comprising aluminium oxide, silicon carbide, boron nitride, titanium carbide and zirconium oxide.

6. Method according to one of the preceding claims, characterized in that the metallic base body (101, 10T, 101") is made of aluminium, an aluminium alloy, grey cast iron or steel.

7. Method according to one of the preceding claims, characterized in that the metallic base body (101) is a brake disc and the coating (102a, 102b) is a brake surface coating of the brake disc.

8. Method according to one of the preceding claims, characterized in that the component (100') is a disc coupling having two metallic base bodies (101, 10T) which are each provided with the coating (102a, 102b) on their mutually facing surfaces (101a, 101b).

9. Method according to one of the preceding claims, characterized in that the coating (102c) adjoins an edge side of the base body (101") and has the same thickness (d) as the base body (101").

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