Hard material-coated braking element and method for producing a hard material-coated braking element

Abstract

The invention relates to the field of vehicle technology and industrial plant engineering and relates to a hard material-coated braking element. The object of the invention is to provide a braking element, which has an improved service life with reduced manufacturing costs. The object is achieved by a hard material-coated braking element, comprising a metal base body which has at least one region designed as a friction surface, on which at least one wear-protection layer is arranged by means of a thermal coating method, wherein the wear-protection layer is formed from at least one metal matrix material and hard material particle agglomerates at least partially embedded therein, which are connected to the metal material matrix in a materially bonded manner. The hard material particle agglomerates are formed from at least one hard material A, one hard material B and hard material mixed crystals of the hard materials A and B, wherein the hard material A is present in a larger volume fraction than the hard material B in the hard material particle agglomerate. The braking element can, for example, be used in a braking system for motor vehicles and rail vehicles or in a braking system for industrial plants.

Description

[0001] Hard-coated brake body and method for producing hard-coated brake bodies

[0002] Description

[0003] The present invention relates to the field of automotive engineering and industrial plant engineering and concerns a hard-coated brake element, which can be, for example, a brake disc or brake drum. The hard-coated brake element according to the invention can be used, for example, in a braking system of motor vehicles and rail vehicles, in a disc brake system on bicycles, or in a braking system of industrial plants or wind turbines.

[0004] Brake calipers have several functional areas. For example, brake calipers are mounted on the front and rear axles of motor vehicles and have a contact surface that is in contact with the wheel rim or wheel hub.

[0005] Conventional brake discs are designed as solid, non-ventilated or internally ventilated brake discs and can be made of a metallic or ceramic material. Conventional brake drums are designed as solid, sometimes with cooling structures on the outside of the drum, and are made of a metallic material.

[0006] The friction surfaces of the brake bodies have a coating that wears more and more as the braking process progresses, and which, in conjunction with the brake pads, achieves the braking effect.

[0007] Various brake bodies are known from the state of the art which have a wear-resistant coating.

[0008] From DE 197 11 830 A1, a sintered friction body, in particular a brake lining for a brake body made of fiber-reinforced ceramic, is known, which contains primary carbon and metal particles that are at least partially reaction-bonded with the primary or pyrolytically formed carbon. i From DE 100 56 161 A1, a brake disc and a method for its production are known, in which a brake disc body made of a cast iron material is provided with a metallic, non-ceramic coating, at least in sections and at least on one of its axial outer surfaces. To prepare the contact surface of the base body to be coated, the existing oxide layer or other contaminants are removed from the contact surface and the contact surface is roughened by irradiation with fine particles in order to increase the adhesion of the wear protection layer. The wear protection layer is then applied by means of flame, arc, or

[0009] Plasma injection molding coating process sprayed onto the contact surface of the base body.

[0010] WO 2012 156 114 A1 discloses a brake disc and a method for producing a brake disc, in which a base body has at least one contact surface to which a wear-resistant layer is applied. To achieve the bond between the wear-resistant layer and the base body, at least one contact surface of the base body is pretreated. The at least one pretreated contact surface of the base body has a surface topography modified by laser radiation with at least one predetermined parameter to improve the positive adhesion between the wear-resistant layer and the base body.

[0011] Also known from DE 10 2019 207 291 A1 is a friction brake body for a friction brake of a motor vehicle, in particular a brake disc, comprising a base body made in particular of gray cast iron and at least one wear protection layer formed on a friction contact surface of the base body. The wear protection layer is made of ferritic-austenitic steel and has embedded hard material particles, in particular finely distributed hard material particles.

[0012] A disadvantage of the brake bodies known from the prior art is that the wear protection layer has a short service life and high manufacturing costs. The object of the present invention is to provide a brake body that has an improved service life and reduced manufacturing costs.

[0013] This object is achieved by the invention defined in the patent claims. Advantageous embodiments are the subject of the dependent claims, whereby the invention also includes combinations of the individual dependent claims in the sense of an AND connection, as long as they are not mutually exclusive.

[0014] The object of the invention is achieved by a novel brake body and a new method for producing such brake bodies, which has an improved service life and with which such brake bodies can be produced cost-effectively and in a time-efficient manner.

[0015] This is achieved by a hard material coated brake body, comprising a metallic base body which has at least one region designed as a friction surface, on which at least one wear protection layer is arranged by means of a thermal coating process, wherein the wear protection layer is formed from at least one metallic matrix material and hard material particle agglomerates at least partially embedded therein, which are materially bonded to the metallic matrix material, wherein the hard material particle agglomerates are formed from at least one hard material A, at least one hard material B and hard material mixed crystals of at least the hard material A and hard material B, wherein the hard material A is present in a larger volume fraction than the hard material B in the hard material particle agglomerate.

[0016] Advantageously, the hard material particle agglomerates additionally comprise at least one metallic filler material and / or an alloying element.

[0017] The hard material particle agglomerates can also advantageously have a spherical particle morphology.

[0018] In an advantageous embodiment, hard material A and hard material B are selected from the group of carbides, nitrides, or carbonitrides. In a particularly advantageous embodiment of the hard-coated brake body, carbide A is TiC, and carbide B is selected from Mo2C, WC, Cr3C2, NbC, and / or TaC.

[0019] It is also advantageous if at least one bonding layer is provided as a buffer layer between the metallic base body and the wear protection layer.

[0020] It is also advantageous if the metallic filler material, the bonding layer and / or the metallic matrix material is an Fe-based material, particularly advantageously a stainless steel material, wherein the stainless steel material particularly advantageously has the material quality of EN 1 .4016, EN 1 .4404 or EN 1 .4435.

[0021] In an advantageous embodiment of the invention, the carbide B is present at 1 vol.% to 30 vol.%, based on the total composition of the hard material particle agglomerates.

[0022] Advantageously, in the case of the hard-coated brake body, 10% - 60% of the surface of the wear protection layer is made up of hard material particle agglomerates.

[0023] Furthermore, it is advantageous if the hard material particle agglomerates are homogeneously distributed or graded embedded in the metallic matrix material.

[0024] In an advantageous embodiment, the hard material particle agglomerates have a thermal conductivity of < 120 W / mK.

[0025] Advantageously, the hard material particle agglomerates have a diameter of 10 pm to 100 pm, particularly advantageously a diameter of 45 pm to 90 pm. It is also advantageous if the bonding layer has a layer height of < 100 pm.

[0026] Furthermore, it is advantageous if the wear protection layer has a layer height of 25 pm to 175 pm.

[0027] It is also advantageous if the wear protection layer and / or the bonding layer has wear detection features.

[0028] According to the invention, a method for producing a hard material-coated brake body is also provided, comprising the following method steps: a) Providing a metallic base body which has at least one region designed as a friction surface, b) Providing prefabricated hard material particle agglomerates which have at least one hard material A, at least one hard material B and hard material mixed crystals of the hard materials A and B, c) Simultaneously arranging the hard material particle agglomerates and the metallic matrix material via at least two separate feed devices by means of a thermal coating method on at least the region designed as a friction surface, whereby a material-to-material connection and wear-protection layer is produced, d) Machining the surface of the wear-protection layer.

[0029] In an advantageous embodiment of the method, it can be provided that hard material particle agglomerates are provided from at least one hard material A, at least one hard material B and hard material mixed crystals from at least the hard material A and hard material B, wherein the hard material A is present in a larger volume fraction than the hard material B in the hard material particle agglomerate.

[0030] Advantageously, a bonding layer is arranged as a buffer layer between the area of ​​the base body designed as a friction surface and the wear protection layer. It is also advantageous if the bonding layer and / or the wear protection layer are applied in a locally generated protective gas atmosphere.

[0031] In an advantageous embodiment of the process, the metallic base body is preheated before thermal coating.

[0032] A particularly advantageous thermal coating process is laser cladding.

[0033] It is also advantageous if the surface of the wear protection layer is machined by surface grinding.

[0034] According to the invention, a brake body is provided that comprises a metallic base body. The metallic base body has at least one region formed as a friction surface, on which at least one wear-resistant layer comprising hard material particle agglomerates is applied by means of a thermal coating process.

[0035] In the context of the invention, a hard material is to be understood as meaning particles formed in such a way that at least one hard material A, at least one hard material B and mixed crystals formed from the hard materials A and B are present, wherein a metallic additional material or alloying elements may also be present.

[0036] The hard material mixed crystals are formed in the edge area of ​​the hard materials A and B.

[0037] Essential to the invention for the improved mechanical properties of the hard material particle agglomerates and thus of the wear protection layer is that the hard material A is present in a larger volume fraction than the hard material B in the hard material particle agglomerate.

[0038] Advantageously, it can be provided that at least one bonding layer is arranged as a buffer layer between the metallic base body and the wear protection layer in order, for example, to achieve improved adhesion and thus reduce the risk of delamination.

[0039] The at least one wear-resistant layer and any bonding layer provided are applied using a thermal coating process, advantageously using laser cladding. The thermal coating process, and advantageously laser cladding, offers the technical advantage of allowing highly targeted and individually homogeneous or even graded layers to be applied to the base body. These layers are permanently bonded to one another by means of a material bond, effectively preventing delamination of the layers with the base body.

[0040] The thermal input of the thermal coating process leads to a material bond between the layer and the substrate and, particularly in laser cladding, has the significant advantage over thermal spraying that deformation of the hard particle agglomerates according to the invention is effectively prevented. A further advantage of laser cladding is that the adjusted intensity distribution of the laser spot virtually eliminates adverse chemical and mechanical properties of the hard particle agglomerates, such as carburization, hardening, and reduced corrosion resistance of the wear-resistant layer, particularly with regard to an Fe-based matrix metal. Thus, an improved material utilization rate is achieved, which significantly reduces manufacturing costs.

[0041] The wear protection layer is formed from at least one metallic matrix material and prefabricated hard particle agglomerates at least partially embedded therein. The prefabricated hard particle agglomerates were produced in a preliminary process step by spray granulation and sintering, which advantageously creates a spherical particle morphology. The spherical particle morphology of the hard particle agglomerates has the significant advantage of almost completely eliminating the previously disadvantageous irregular and sharp-edged particle morphology, rough, irregular, intact hard particle surfaces, and wear protection layers exhibiting defects.

[0042] The advantageous spherical particle morphology of the hard material particle agglomerates leads to an improved service life of both the brake body during use and the tool during possible surface finishing during production. Furthermore, the formation of a spherical particle morphology during the final finishing of the wear protection layer results in improved dimensional stability and a reduced tendency for the hard material particle agglomerates to fracture, thus preventing damage and / or breakage of the hard material particle agglomerates from the wear protection layer and ensuring a higher proportion of intact hard material particle agglomerates in the tribological system.

[0043] Another significant technical advantage of using spray granulation and sintering in the upstream production of the hard material particle agglomerates is that the hard material particles are formed as agglomerates consisting of at least one hard material A, at least one hard material B, and hard material mixed crystals of the hard materials A and B. Advantageously, the hard material particle agglomerate can contain a metallic filler material and / or alloying elements. The metallic filler material and / or alloying elements can also be present in agglomerated form in the hard material particle.

[0044] Particular technical advantages and effects are achieved in terms of wear protection when the hard material particle agglomerates are formed from at least one carbide A, at least one carbide B and solid solution carbides from at least the carbides A and B and the carbide A is present in a larger volume fraction than the carbide B in the hard material particle agglomerate.

[0045] It was surprisingly discovered that the use of hard particle agglomerates and solid solution carbides, advantageously with TiC as carbide A and Mo2C, WC, Cr3C2, NbC, and / or TaC as carbide B, creates a very fine-grained structure with a homogeneous microstructure. Such hard particle agglomerates exhibit high hardness and fracture toughness with a higher density than carbide A, thereby significantly improving the service life of the wear protection layer and the thermal resilience of the brake body. Furthermore, the high density of the hard particle agglomerates reduces sedimentation and demixing, thus improving storage stability as well as dosing and conveying capabilities during the thermal coating process.

[0046] It is also conceivable that CrsC2 is present as carbide A, although in this case it is excluded that CrsC2 also forms carbide B or is present as a mixed crystal carbide of carbide A and B.

[0047] A particularly good material connection of an advantageously provided bonding layer with the metallic base body and with the wear protection layer is achieved in that at least the metallic matrix material and / or the additional material is an Fe-base material, wherein the metallic matrix material is particularly advantageously a stainless steel material with the material quality of EN 1.4016, EN1.4404 or EN 1.4435.

[0048] Particularly advantageous properties of the hard material particle agglomerates, such as a high melting and decomposition temperature with high hardness and improved thermal expansion behavior, are advantageously achieved when the carbide B is present at 1 vol.% to 30 vol.%, based on the total composition of the hard material particle agglomerates.

[0049] A long service life with reduced corrosion tendency of the brake body can be achieved by forming 10% - 60% of the surface of the wear protection layer from hard material particle agglomerates and / or the hard material particle agglomerates having a diameter of 10 pm to 100 pm, advantageously 45 pm to 90 pm.

[0050] The hard material particle agglomerates can advantageously be homogeneously distributed or embedded in a graded manner in the metallic matrix material. According to the invention, a graded distribution of the hard material particles means that the gradation is realized within the layer thickness of the metallic matrix material and / or within the circumference of the friction surface of the brake body. Such gradation has the significant technical advantage that the thermal balance within the brake body can be adjusted and adapted to the varying thermal load, thus allowing the brake bodies to be individually configured for different applications. The hard material particle agglomerates embedded in the metallic matrix material advantageously have a thermal conductivity of < 120 W / mK.

[0051] To achieve a permanent, material-to-material bond between the bonding layer and the cast material of the metallic base body and the wear-resistant layer, the bonding layer can advantageously have a layer thickness of < 100 pm. To reduce the overall weight and stresses in the brake body, the wear-resistant layer can advantageously have a low layer thickness of 25 pm to 175 pm.

[0052] In order to increase traffic and maintenance safety, it can advantageously be provided that the wear protection layer and / or the bonding layer has wear detection features by means of which the wear limit of the brake body or the wear protection layer can be identified.

[0053] According to the invention, a method for producing a hard material-coated brake body is also provided, which is characterized by the following method steps: a) Providing a metallic base body which has at least one region designed as a friction surface, b) Providing prefabricated hard material particle agglomerates which have at least one hard material A, at least one hard material B and hard material mixed crystals of the hard materials A and B, c) Simultaneously arranging the hard material particle agglomerates and the metallic matrix material via at least two separate feed devices by means of a thermal coating method on at least the region designed as a friction surface, whereby a material-to-material connection and wear-protection layer is produced, d) Machining the surface of the wear-protection layer.Advantageously, the arrangement of a bonding layer on the metallic base body can be provided as a buffer layer. It can also advantageously be provided that the bonding layer and / or the wear-resistant layer are applied under a locally generated protective gas atmosphere, which is supplied to the process in situ during coating, advantageously by laser deposition welding, via a gas supply line coupled to the at least one supply device. The locally generated protective gas flow, aligned coaxially with the coating flow, prevents oxygen from being introduced into the coating process due to turbulence occurring during laser deposition welding.Furthermore, the in-situ introduction of the locally generated shielding gas during the process creates an additional gas flow directly at the feeder, resulting in a larger, lower-oxygen shielding gas coverage of the coating zone, providing a more effective and cost-effective process. Thus, the use of the shielding gas leads to a reduction in oxygen and thus to greater oxidation resistance of the wear protection layer.

[0054] It was also discovered that the low oxygen content in the coating zone, particularly during laser cladding under a locally generated inert gas atmosphere, leads to improved wetting of the melt with the base material of the metallic substrate and / or the bonding layer. This has the technical advantage of significantly reducing the oxidation of the hard material particle agglomerates and the associated smoke formation. As a result, an improved wear protection layer is produced, which is characterized, among other things, by low porosity and a low defect rate.

[0055] In an advantageous process step, it can also be provided that the metallic base body is preheated before coating. The technical effect of preheating the metallic base body before thermal coating is that the coating cycle time is reduced, which enables higher product output and thus a reduction in time and costs. Furthermore, temperature-induced stresses are reduced, which lead to significantly improved dimensional stability of the brake body. The invention is explained in more detail below using an exemplary embodiment.

[0056] Example

[0057] To produce a hard-coated brake body, a brake disc blank with formed friction surfaces made of a cast material is prepared in a thermal coating system as the metallic base body. Hard particle agglomerates with spherical particle morphology are stored in a pre-production process involving spray granulation and sintering, which are fed in powder form to a first feed device. The hard particles consist of an agglomerate of carbide A, which is TiC, carbide B, which is WC, and stainless steel 316 L, which corresponds to material grade EN 1.4404. Carbide B accounts for 10 vol.% of the total composition of the hard particles, and the hard particle agglomerate contains 10 vol.% of stainless steel 316 L.The hard material particle agglomerates present are present as individual carbides A and B with solid solution carbides of carbides A and B, have the composition TiC-WC and exhibit a particle diameter between 45 pm and 90 pm. In addition, a stainless steel material of material grade EN 1.4404 is provided to a second feed device for the production of the bonding layer and as a metallic matrix material for the wear protection layer. In a first process step, the brake disc is preheated to approximately 165°C and then, by laser deposition welding via the second feed device under a locally generated protective gas atmosphere, a bonding layer with a layer thickness of 85 pm is applied in the area of ​​the friction surface of the brake disc. During the coating of the bonding layer, the bonding layer is bonded in situ to the cast material of the brake disc blank.The wear protection layer with the hard material particle agglomerates is then applied to the bonding layer using laser deposition welding under a locally generated protective gas atmosphere. The metallic matrix material is fed separately via the second feeder and the hard material particle agglomerates via the first feeder. The proportion of hard material particle agglomerates relative to the metallic matrix material is < 40 vol.% of the wear protection layer. After the wear protection layer has been applied, the surface is fully machined using surface grinding. Finishing requires only a removal of 50–65 μm to completely eliminate axial runout errors and layer thickness differences.After finishing, the brake disc has a 2-layer wear protection layer with a total layer thickness of < 300 pm, whereby the wear protection layer has a layer thickness of at least 100 pm.

Claims

Patent claims 1. Hard material coated brake body, comprising a metallic base body which has at least one region designed as a friction surface, on which at least one wear protection layer is arranged by means of a thermal coating process, wherein the wear protection layer is formed at least from a metallic matrix material and hard material particle agglomerates at least partially embedded therein, which are materially bonded to the metallic matrix material, wherein the hard material particle agglomerates are formed from at least one hard material A, at least one hard material B and hard material mixed crystals of at least the hard material A and hard material B, wherein the hard material A is present in a larger volume fraction than the hard material B in the hard material particle agglomerate.

2. Hard material coated brake body according to claim 1, wherein the hard material particle agglomerates additionally comprise at least one metallic filler material and / or an alloying element.

3. Hard material coated brake body according to claim 1, wherein the hard material particle agglomerates have a spherical particle morphology.

4. Hard material coated brake body according to claim 1, wherein the hard material A and the hard material B are selected from the group of carbides, nitrides or carbonitrides.

5. Hard material coated brake body according to claim 1, wherein the hard material particle agglomerates are formed from at least one carbide A, at least one carbide B and solid solution carbides from at least the carbides A and B and the carbide A is present in a larger volume fraction than the carbide B in the hard material particle agglomerate.

6. Hard-coated brake body according to claim 5, wherein the carbide A is TiC.

7. Hard-coated brake body according to claim 5, wherein the carbide B is Mo2C, WC, Cr3C2, NbC and / or TaC.

8. Hard material coated brake body according to claim 1, wherein at least one bonding layer is provided as a buffer layer between the metallic base body and the wear protection layer.

9. Hard-coated brake body according to claim 1 or 2, wherein the metallic filler material, the bonding layer and / or the metallic matrix material is an Fe-base material, particularly advantageously a stainless steel material.

10. Hard-coated brake body according to claim 9, wherein the stainless steel material has the material quality of EN 1.4016, EN 1.4404 or EN 1.4435.

11. Hard material coated brake body according to claim 1, wherein the hard material B is present in an amount of 1 vol.% to 30 vol.%, based on the total composition of the hard material particle agglomerates.

12. Hard material coated brake body according to claim 1, wherein 10% - 60% of the surface of the wear protection layer is formed from hard material particle agglomerates.

13. Hard material coated brake body according to claim 1, wherein the hard material particle agglomerates are homogeneously distributed or graded embedded in the metallic matrix material.

14. Hard material coated brake body according to claim 1, wherein the hard material particle agglomerates have a thermal conductivity of < 120 W / mK.

15. Hard material coated brake body according to claim 1, wherein the hard material particle agglomerates have a diameter of 10 pm to 100 pm, advantageously 45 pm to 90 pm.

16. Hard material coated brake body according to claim 1, wherein the bonding layer has a layer height of < 100 pm.

17. Hard material coated brake body according to claim 1, in which the Wear protection layer has a layer height of 25 pm to 175 pm.

18. Hard material coated brake body according to claim 1, in which the Wear protection layer and / or the bonding layer has wear detection features.

19. Method for producing a hard material coated brake body, comprising the following method steps: a) Providing a metallic base body which has at least one region designed as a friction surface, b) Providing prefabricated hard material particle agglomerates which have at least one hard material A, at least one hard material B and mixed crystals of the hard materials A and B, c) Simultaneously arranging the hard material particle agglomerates and the metallic matrix material via at least two separate feed devices by means of a thermal coating method on at least the region designed as a friction surface, whereby a material-to-material connection and wear-protection layer is produced, d) Machining the surface of the wear-protection layer.

20. The method according to claim 19, wherein prefabricated hard material particle agglomerates are provided which comprise at least one hard material A, at least one hard material B and mixed crystals of the hard materials A and B, wherein the carbide A is present in a larger volume fraction than the carbide B in the hard material particle agglomerate.

21. The method according to claim 19, wherein a bonding layer is arranged as a buffer layer between the region of the base body designed as a friction surface and the wear protection layer.

22. Method according to claim 19, wherein the arrangement of the bonding layer and / or the wear protection layer is carried out under a locally generated protective gas atmosphere.

23. The method according to claim 19, wherein the metallic base body is preheated before thermal coating.

24. The method according to claim 19, wherein the thermal coating is carried out by laser deposition welding.

25. The method according to claim 19, wherein the surface of the wear protection layer is machined by surface grinding.