Brake disc, means of transport and method for coating a brake disc

Abstract

A brake disc (1), a means of transport, and a method for coating a brake disc (1) are proposed. The method comprises the following steps: removing graphite clusters (2) from the brake disc (1) and applying a hard material layer (3) to the brake disc (1) using a laser deposition welding process.

Description

[0001] The present invention relates to a brake disc, a means of transport, and a method for coating a brake disc. In particular, the present invention relates to reducing the production of particulate matter due to brake wear during use of a braking system of a means of transport.

[0002] Today's vehicles, especially road vehicles, use brake discs in series production, which are typically made of gray cast iron (GG15). When a brake disc is used on a vehicle, brake disc wear is produced, which is released into the environment as particulate matter. Considerable efforts are currently being made to prevent or capture this particulate matter in order to reduce emissions.

[0003] Furthermore, the use of laser cladding to deposit hard coatings on workpieces is known in the art. Laser cladding is also referred to as laser material deposition (LMD) or HS-LMD. An alternative coating method is cold gas spraying (CGS).

[0004] Depending on the casting process, gray cast iron, especially GG15, contains small graphite pockets within the material, particularly in the machined workpiece surface. These pockets can range in diameter from 0.02 to 1 mm. When using a melt-out "blasting or coating technique," the laser, for example, also melts the GG15 material or its graphite pockets. This leads to the problem that the graphite pockets evaporate when the surface melts and create a gas bubble, which is also referred to as a blowup or blowout. This can cause an invisible gas bubble or a crack in the hard material coating, or a predetermined breaking point / delamination in the coating. Alternatively or additionally, the entire layer (bonding and friction layer) can be pre-damaged. Detecting these potential defects is difficult and, in particular, difficult to automate.

[0005] It is an object of the present invention to provide a brake disc with a reduced tendency to emit particulate matter. In particular, it is an object of the present invention to enable a hard material coating on a brake disc to be applied reliably and with high quality.

[0006] The above object is achieved according to the invention by a method having the features according to claim 1, a brake disc having the features according to claim 9 and a means of transport having the features according to claim 10.

[0007] The subclaims show preferred developments of the invention.

[0008] According to the method according to the invention, a brake disc is coated as follows: Graphite nests are first removed from the surface of the brake disc, leaving empty cavities in their place. The graphite nests can be removed, for example, by the application of heat and / or mechanical forces. In a second step, a hard material layer is applied to the brake disc pretreated in this way using a laser cladding process. Due to the fact that the graphite nests are no longer contained in the surface of the brake disc at this point, they cannot outgas and cannot prevent the formation of a closed hard material layer that is solidly and permanently bonded to the brake disc. The result is a hard material-coated brake disc that has a significantly lower tendency to emit particulate matter than brake discs known from the prior art.The lubricating effect of the graphite nests, which was always intended in the prior art, can be dispensed with according to the invention, since a completely sealed brake disc surface is created.

[0009] The removal of graphite clusters can be achieved by means of a laser pre-treatment of the brake disc. For example, the surface of the brake disc is heated using a second laser or in a process step prior to the laser cladding process in such a way that exposed graphite clusters evaporate in the process. This pre-treatment can heat the surface of the brake disc more intensely than is the case during the laser cladding process. In particular, the laser intensity during the pre-treatment can be set higher than the laser intensity during the laser cladding process. The brake disc can be rotated during the pre-treatment as well as during the laser cladding process. In particular, it can be clamped while it rotates and its surface is machined.In particular, both the laser pretreatment and the laser deposition welding process can be carried out from smaller radii towards larger radii.

[0010] However, the removal of graphite nests can also be achieved using an intensive washing process. This can be performed as an alternative to or in addition to the laser pretreatment described above. For example, the washing process can be performed before or after the laser pretreatment. The washing process can use water as a washing solution / solvent / anti-corrosion agent. A waterjet head can be used, in which one or more nozzles (flat jet or round jet) are arranged. This allows a larger surface area to be exposed to a water jet per unit of time, which accelerates the high-pressure washing process.

[0011] The nozzles can have an outlet opening with a diameter of 0.4 to 0.8 mm. The waterjet head can have one nozzle, two nozzles, three nozzles, four nozzles, or more nozzles. The nozzles can be spaced from the surface of the brake disc at a distance of 20 mm to 40 mm, in particular between 25 mm and 30 mm. The feed rate can be in the range of 5 mm / s to 40 mm / s, in particular between 10 mm / s and 30 mm / s. The pressures used can be in the range between 200 bar and 1000 bar, in particular between 300 bar and 600 bar. The laser pretreatment or the high-pressure washing process can also be used to remove a layer applied to the brake disc for the purpose of corrosion protection and to promote the adhesion of the hard material layer to the brake disc. The hard material layer can be made of stainless steel and / or a ceramic and / or a lightweight layer.The hard material coating can consist of at least one single layer, usually two layers. The hard material coating is characterized by the fact that it consists of a metallic compound, usually a steel or a titanium material. The actual wear layer can be a two-phase material, which usually has a proportion of between 10 and 70 vol% carbide reinforcement, e.g., TiC, WC, SiC, NiC. The hard material top layer is designed in particular to protect the surface of the brake disc from abrasion, even during operation or use, and thus to prevent or reduce the formation of fine dust.

[0012] According to a second aspect of the present invention, a brake disc is proposed which is obtainable by a method as described above. The brake disc therefore has emptied graphite nests which are sealed by a hard material layer covering the surface.

[0013] According to a third aspect of the present invention, a means of transportation is proposed which has at least one brake disc according to the second aspect of the invention or has a brake disc produced by a method according to the invention. In this way, the features, combinations of features, and the resulting advantages of the method according to the invention and of the brake disc according to the invention are also evident for the means of transportation in a corresponding manner, so that reference is made to the above explanations to avoid repetition. Short description of the characters

[0014] Further details, advantages, and features of the present invention will become apparent from the following description of exemplary embodiments with reference to the drawings. Fig. 1 a schematic representation of an embodiment of a means of transport according to the invention with an embodiment of a brake disc according to the invention; Fig. 2 a sectional side view of a method step according to the invention for providing a brake disc for carrying out a method according to the invention; Fig. 3 a sectional side view of a method step according to the invention for removing graphite nests from the brake disc; and Fig. 4 a sectional side view of a method step according to the invention for applying a hard material layer to the pretreated brake disc. Embodiments of the invention:

[0015] Fig. 1 shows a passenger car as an exemplary embodiment of a means of transport 10 according to the invention, which has an exemplary embodiment of a brake disc 1 manufactured according to the invention on its front axle. The production of the brake disc 1 is explained in detail below.

[0016] Fig. 2 shows a sectional side view of a brake disc 1 coated with a material 9 as corrosion protection during the preparation 100. Graphite nests 2 are arranged in the surface of the brake disc material, which could outgas during a subsequent build-up welding process and adversely affect the result.

[0017] Fig. 3 shows a sectioned side view of the brake disc 1 from Fig. 2, after the material 9 has been removed by water jets 6 using a water jet head 7 with four nozzles 8. The graphite nests 2 have left behind 200 open cavities 11 as a result of the removal, which do not cause any problems due to outgassing during subsequent surface heating.

[0018] Fig. 4 shows a sectional side view of an application 300 of a hard material layer 3, onto the brake disc 1 made of Fig.3. The brake disc 1 is rotated according to arrow P, as it will later be rotated on the means of transport. Using a first laser 5 for pretreating the brake disc 1, a laser beam 13 with a high intensity is directed onto the surface of the brake disc 1. The laser 5 is guided ahead of a second laser 4, which directs a weaker laser beam 12 onto the surface of the brake disc 1 for the purpose of build-up welding, so that the laser beam 13 has already dried and heated the surface of the brake disc 1 and has evaporated any graphite nests remaining in the surface. The laser beam 12 used for build-up welding has a lower intensity and fuses the surface of the brake disc 1 with the particles (not shown), which form the hard material layer 3 due to the effect of heat. List of reference symbols: 1 brake disc 2 graphite nest 3 Hard material layer 4, 5 lasers 6 Water (jet) 7 Water jet head 8 nozzles 9 Material for corrosion protection 10 means of transport 11 cavities 12, 13 Laser beam 100 - 300 process steps P Arrow

Claims

[1] Method for coating a brake disc (1) comprising the steps - Removing (200) graphite nests (2) from the brake disc (1) and - Applying (300) a hard material layer (3) to the brake disc (1) by means of a laser deposition welding process. [2] Method according to claim 1, wherein the removal is carried out by means of a laser pre-treatment of the brake disc (1), wherein in particular a laser (5) is used for the pre-treatment which has a higher intensity than a laser (4) used for the laser deposition welding process. [3] Method according to claim 1 or 2, wherein the removal of the graphite nests (2) is carried out by means of a high-pressure washing process. [4] The method according to claim 3, wherein the high pressure washing process - Water (6) as washing solution and / or - Corrosion protection medium to prevent premature corrosion of the grey cast iron and / or - Abrasive to wash out soft phases on the brake disc and / or - a water jet head (7) with one or more nozzles (8) is used. [5] Method according to one of the preceding claims 3 or 4, wherein the high-pressure washing process is carried out at pressures of 300 bar to 1500 bar, in particular in the range of 500 bar to 900 bar. [6] Method according to one of the preceding claims, wherein the brake disc (1) during the removal of the graphite nests (2) - rotates and / or - machining from smaller radii to larger radii and / or - is processed by one side or both sides at the same time. [7] Method according to one of the preceding claims further comprising the step - Providing (100) the brake disc (1), which is made in particular from a turned grey cast iron, in particular GG15 or EN-GJL-150 UHC, and is preferably coated with a material (9) for the purpose of reducing fine dust and / or protecting against corrosion. [8] Method according to one of the preceding claims, wherein the hard material layer (3) - stainless steel and / or - a ceramic and / or - a lightweight layer and / or - a mixture of several materials, in particular e.g. steel matrix with carbide reinforcement. [9] Brake disc obtainable by a method according to one of the preceding claims. [10] Means of transport (10) comprising a brake disc (1) according to claim 9.

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