Brake disc for a motor vehicle and method for producing such a brake disc
Patent Information
- Application Number
- EP2024716772
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-04-25
- Filing Date
- 2024-04-03
- Publication Date
- 2026-03-04
AI Technical Summary
Current brake discs for motor vehicles emit harmful fine particles (PM10) during braking, which are dangerous for respiratory health, and existing solutions such as particle capture devices and expensive particle filters are inadequate, especially for powerful vehicles.
A brake disc with a two-layer coating comprising a chromium-rich steel matrix and carbide reinforcements, such as niobium or titanium carbide, applied using the EHLA laser deposition technique, which reduces wear and particle emission by enhancing mechanical and thermal resistance.
The coated brake disc effectively limits wear and reduces fine particle emissions during braking, offering improved mechanical resistance and thermal performance without increasing costs, thus addressing the limitations of existing solutions.
Smart Images
Figure EP2024059026_31102024_PF_FP_ABST
Abstract
Description
[0001] Brake disc for a motor vehicle and method of manufacturing such a brake disc
[0002] The present invention relates, in general, to the control of polluting emissions from a motor vehicle and, more specifically, to the emission of fine particles when braking by a motor vehicle.
[0003] In particular, the invention relates to a brake disc for a motor vehicle and a method of manufacturing such a brake disc.
[0004] In a motor vehicle, wear of the brake disc and the friction between the brake pads and the brake disc during braking cause the release of polluting particles into the atmosphere.
[0005] Emissions of particles smaller than 10 pm (PM10), known as fine particles, are particularly dangerous for the respiratory tracts of populations.
[0006] Therefore, as part of a future Euro 7 standard, new European regulations aim to limit fine particle emissions from braking of private and commercial vehicles.
[0007] There is a device for capturing the released particles, based on the operation of suction turbines triggered during braking.
[0008] However, this device is bulky and captures particles only during braking.
[0009] Another solution is to integrate particle filters into the braking system.
[0010] However, these filters are particularly expensive.
[0011] There are also cast iron brake discs, which contain additional elements such as vanadium.
[0012] Although doping cast iron improves the wear and thermal fatigue properties of the brake disc and thus reduces the release of particles, this solution is not sufficient for the most powerful motor vehicles.
[0013] The invention therefore aims to remedy these drawbacks and to propose a solution aimed at optimizing the limitation of wear on brake discs, particularly for motor vehicles, and reducing the release of fine particles.
[0014] There is therefore provided a brake disc for a motor vehicle comprising at least one external surface comprising a coating, the coating comprising: a first layer arranged on all or part of the external surface, the first layer comprising a steel having a chromium content of between 10 and 20% by mass relative to the total mass of the steel; a second layer arranged on the first layer, the second layer comprising a steel matrix having a chromium content of between 10 and 20% by mass relative to the total mass of the steel, and a content of between 15 and 40% by volume of at least one carbide relative to the total volume of the second layer, the carbide being chosen from the following compounds: silicon carbide, chromium carbide, tungsten carbide, niobium carbide, titanium carbide or a mixture thereof, preferably chosen from niobium carbide, titanium carbide or a mixture thereof;the coating being obtained using a very high-speed laser material deposition technique known as EHLA.;
[0015] Preferably, the coating is a two-layer coating comprising only said first layer and said second layer.
[0016] According to one characteristic, the steel of the first layer and / or the steel of the second layer may be a ferritic steel.
[0017] Preferably, the ferritic steel is a steel consisting of a chromium content of between 16 and 18% by mass, a silicon content of less than or equal to 1% by mass, a nickel content of less than or equal to 0.6% by mass, a manganese content of less than or equal to 1% by mass, a carbon content of less than or equal to 0.08% by mass, a molybdenum content of less than or equal to 1% by mass, a phosphorus content of less than or equal to 0.045% by mass, a sulfur content of less than or equal to 0.03% by mass, a titanium content of less than or equal to 0.01% by mass, optionally other additional elements such as copper, vanadium, niobium, or tin, the remainder being iron as well as unavoidable impurities.
[0018] In one embodiment, the second layer may comprise a titanium carbide content of between 15 and 25% by volume, preferably between 17 and 23% by volume, more preferably between 19 and 21% by volume, relative to the total volume of the second layer.
[0019] In another embodiment, the second layer may comprise a niobium carbide content of between 25 and 35% by volume, preferably between 27 and 33% by volume, more preferably between 29 and 31% by volume, relative to the total volume of the second layer.
[0020] In another embodiment, the second layer may comprise a mixture of carbides, the content of each carbide in the mixture of carbides being between 5 and 20% by volume, preferably between 5 and 10% by volume, relative to the total volume of the second layer.
[0021] According to one characteristic, the second layer may comprise a mixture of niobium carbide and titanium carbide, the niobium carbide content being between 5 and 20% by volume, preferably between 5 and 10% by volume relative to the total volume of the second layer, and a titanium carbide content of between 5 and 20% by volume, preferably between 5 and 10% by volume relative to the total volume of the second layer.
[0022] Advantageously, the material of the brake disc on which the coating is arranged may be cast iron, preferably cast iron with lamellar graphite.
[0023] Preferably, the brake disc may comprise first and second opposite faces respectively comprising first and second external surfaces, each of the first and second external surfaces comprising a friction track intended to cooperate with a brake pad, the coating being arranged at least partially on the friction tracks, preferably only arranged on the friction tracks.
[0024] The invention also relates to a method of manufacturing a brake disc as previously described, comprising the formation of the first layer and the second layer of the coating by a very high speed laser material deposition technique called EHLA.
[0025] Preferably, the step of forming the second layer of the coating of the manufacturing process comprises the use of cermets.
[0026] The invention also relates to a motor vehicle comprising at least one brake disc as previously described.
[0027] Other aims, advantages and characteristics will emerge from the description which follows, given purely for illustrative purposes and with reference to the attached drawings in which:
[0028] [Fig 1] is a schematic sectional view of a brake disc for a motor vehicle according to one embodiment of the invention.
[0029] [Fig 2] is a detailed view of a friction track of a brake disc shown in Figure 1.
[0030] [Fig 3] represents the mode of operation of the EHLA technique.
[0031] In what follows, and unless otherwise indicated, the limits of a domain of values are included in this domain, notably in the expression "included between".
[0032] Furthermore, the expression "at least one" used in this description is equivalent to the expression "one or more".
[0033] Figure 1 illustrates a brake disc 1 for a motor vehicle, comprising at least one external surface.
[0034] In the illustrated example, the brake disc 1 is an annular structure comprising a first face 2 and a second face 3 opposite the first face 2.
[0035] The first face 2 comprises a first external surface 2a and the second face 3 comprises a second external surface 3a. The first and second external surfaces 2a and 3a each comprise a friction track, respectively a first friction track 4 and a second friction track 5, intended to cooperate with a brake pad (not shown).
[0036] Each friction track 4, 5 forms a contact zone with a brake pad so that the friction of the fixed brake pads on the first and second friction tracks 4, 5 of the movable brake disc 1 leads to braking of the motor vehicle.
[0037] The first and second external surfaces 2a and 3a of the brake disc 1 are coated, at least partially, with a coating 6.
[0038] Advantageously, the coating 6 is formed on the friction tracks 4 and 5.
[0039] The coating 6 is preferably formed only on the friction tracks 4 and 5 in order to limit the cost of the brake disc 1.
[0040] The coating 6 may be formed on all or part of the friction tracks 4 and 5, preferably on all of the friction tracks 4 and 5.
[0041] The material of the brake disc 1 on which the coating 6 is formed is preferably cast iron. Cast iron is a particularly economical material and its high thermal conductivity properties make it possible to store calories and dissipate the heat produced by friction during braking.
[0042] Advantageously, the material of the brake disc 1 on which the coating 6 is formed may be lamellar graphite cast iron, such as GJL 150 cast iron.
[0043] GJL 150 cast iron consists of a carbon content of 3.7% by mass, a silicon content of 1.87% by mass, a manganese content of 0.61% by mass, a sulfur content of less than 0.1% by mass, a phosphorus content of less than 0.1% by mass, a copper content of less than 0.1% by mass, a nickel content of 0.1% by mass, a chromium content of less than 0.1% by mass, a molybdenum content of less than 0.1% by mass, a titanium content of less than or equal to 0.1% by mass, a vanadium content of less than 0.1% by mass, a niobium content of less than 0.1% by mass, a selenium content of less than 0.1% by mass, the remainder being iron as well as unavoidable impurities.
[0044] The coating 6 comprises a first layer 7 arranged in contact with the first and second external surfaces 2a and 3a.
[0045] The first layer 7 comprises a steel having a chromium content of between 10 and 20% by mass relative to the total mass of the steel of the first layer 7.
[0046] Preferably, the steel of the first layer 7 is a ferritic steel. By ferritic steel is meant a steel whose crystal structure is centered cubic and having a chromium content of between 10 and 20% by mass relative to the total mass of the steel.
[0047] Ferritic steels are particularly advantageous given their low tendency to crack, notably due to their low coefficient of thermal expansion, close to that of the cast iron used.
[0048] Preferably, the ferritic steel of the first layer may be a ferritic stainless steel consisting of a chromium content of between 16 and 18% by mass, a silicon content of less than or equal to 1% by mass, a nickel content of less than or equal to 0.6% by mass, a manganese content of less than or equal to 1% by mass, a carbon content of less than or equal to 0.08% by mass, a molybdenum content of less than or equal to 1% by mass, a phosphorus content of less than or equal to 0.045% by mass, a sulfur content of less than or equal to 0.03% by mass, a titanium content of less than or equal to 0.01% by mass, optionally other additional elements such as copper, vanadium, niobium, or tin, the remainder being iron as well as unavoidable impurities.
[0049] Preferably, the total unavoidable impurities represent less than 0.15% by mass.
[0050] Preferably, each unavoidable impurity is present at less than 0.05% by mass.
[0051] According to one example, the ferritic steel of the first layer 7 may be a ferritic stainless steel generally known as 430L steel or by its European designation X2Crl 7, consisting of a chromium content of 16.29% by mass, a silicon content of 0.94% by mass, a nickel content of 0.53% by mass, a manganese content of 0.28% by mass, a carbon content of 0.08% by mass, a molybdenum content of 0.06% by mass, a phosphorus content of 0.031% by mass, a sulfur content of 0.02% by mass, a titanium content of 0.003% by mass, the remainder being iron as well as unavoidable impurities, the percentages being defined relative to the total mass of the steel.
[0052] The coefficient of thermal expansion of ferritic steels is close to or similar to that of cast iron.
[0053] In particular, the thermal expansion coefficient of 430L steel, which is equal to 10.4.10-6 K-l, is very close to that of GJL 150 lamellar graphite cast iron, which is equal to 10.7.10-6 K-l. This has a favorable effect in limiting the number and depth of cracks.
[0054] The coating 6 further comprises a second layer 8 arranged on the first layer 7. The first layer 7 forms an adhesion layer between the first and second external surfaces 2a and 3a of the brake disc 1 and the second layer 8.
[0055] The second layer 8 comprises a steel matrix having a chromium content of between 10 and 20% by mass relative to the total mass of the steel.
[0056] Preferably, the steel of the matrix of the second layer 8 and the steel of the first layer 7 are identical so as to increase the affinity and therefore the adhesion between the first and second layers 7 and 8.
[0057] In this way, the steel of the second layer 8 is preferably a ferritic steel.
[0058] Preferably, the ferritic steel of the second layer 8 may be a ferritic stainless steel consisting of a chromium content of between 16 and 18% by mass, a silicon content of less than or equal to 1% by mass, a nickel content of less than or equal to 0.6% by mass, a manganese content of less than or equal to 1% by mass, a carbon content of less than or equal to 0.08% by mass, a molybdenum content of less than or equal to 1% by mass, a phosphorus content of less than or equal to 0.045% by mass, a sulfur content of less than or equal to 0.03% by mass, a titanium content of less than or equal to 0.01% by mass, optionally other addition elements different from the aforementioned elements such as copper, vanadium, niobium, or tin, the remainder being iron as well as unavoidable impurities.
[0059] Preferably, the total unavoidable impurities represent less than 0.15% by mass.
[0060] Preferably, each unavoidable impurity is present at less than 0.05% by mass.
[0061] According to one example, the ferritic steel of the second layer 8 may be a ferritic stainless steel generally known as 430L steel, consisting of a chromium content of 16.29% by mass, a silicon content of 0.94% by mass, a nickel content of 0.53% by mass, a manganese content of 0.28% by mass, a carbon content of 0.08% by mass, a molybdenum content of 0.06% by mass, a phosphorus content of 0.031% by mass, a sulfur content of 0.02% by mass, a titanium content of 0.003% by mass, the remainder being iron as well as unavoidable impurities, the percentages being defined relative to the total mass of the steel.
[0062] In addition, the second layer 8 comprises a content of between 15 and 40% by volume of at least one carbide relative to the total volume of the second layer. The carbide(s) are chosen from the following compounds: silicon carbide, chromium carbide, tungsten carbide, niobium carbide, titanium carbide or a mixture thereof.
[0063] Silicon carbide, chromium carbide, tungsten carbide, niobium carbide and titanium carbide have the advantage of being readily available in powder form, facilitating their deposition on the brake disc 1 by thermal spraying.
[0064] Silicon carbide, chromium carbide and titanium carbide are also particularly advantageous given their moderate cost and high mechanical strength properties.
[0065] Preferably, the carbide(s) are chosen from niobium carbide and titanium carbide, showing very good mechanical resistance performance, or a mixture thereof.
[0066] Even more preferably, the carbide chosen is titanium carbide, which has similar mechanical and thermal properties to niobium carbide but is less expensive.
[0067] In one embodiment, the second layer 8 may comprise a titanium carbide content of between 15 and 25% by volume, preferably between 17 and 23% by volume, more preferably between 19 and 21% by volume, relative to the total volume of the second layer 8.
[0068] According to one example, the second layer 8 may comprise a titanium carbide content equal to 20% by volume relative to the total volume of the second layer 8.
[0069] In another embodiment, the second layer 8 may comprise a niobium carbide content of between 25 and 35% by volume, preferably between 27 and 33% by volume, more preferably between 29 and 31% by volume, relative to the total volume of the second layer.
[0070] According to one example, the second layer 8 may comprise a niobium carbide content equal to 30%.
[0071] In another embodiment, the second layer may comprise a mixture of carbides, the content of each carbide in the mixture of carbides being between 5 and 20% by volume, preferably between 5 and 10% by volume, relative to the total volume of the second layer.
[0072] By mixing several types of carbides with lower proportions, it is possible to obtain a more economical coating 6.
[0073] According to one embodiment, the second layer 8 may for example comprise a mixture of niobium carbide and titanium carbide, the niobium carbide content being between 5 and 20% by volume, preferably between 5 and 10% by volume relative to the total volume of the second layer, and a titanium carbide content of between 5 and 20% by volume, preferably between 5 and 10% by volume relative to the total volume of the second layer.
[0074] According to one example, the second layer 8 may comprise a mixture of niobium carbide and titanium carbide, the niobium carbide content being 5% by volume and the titanium carbide content being 10% by volume, relative to the total volume of the second layer 8.
[0075] The first layer 7 forms an adhesion layer between the first and second external surfaces 2a and 3a and the second layer 8.
[0076] The thermal expansion coefficients close to the substrate formed by the first and second external surfaces 2a and 3a and of the first layer 7 contribute to increasing this adhesion.
[0077] The second layer 8 forms a first resistant barrier making it possible to reduce the appearance of cracking due to friction between the coated brake disc 1 and the brake pads.
[0078] In addition to the second layer 8, the first layer 7 forms a second mechanical resistance barrier making it possible to reduce the occurrence of cracking.
[0079] Preferably, the coating 6 is a two-layer coating comprising only said first layer and said second layer.
[0080] The two-layer structure of the coating 6 makes it possible to limit the number of interfaces at which porosities may be present and cause the coating 6 to decohere, making it fragile when faced with mechanical stresses. The two-layer structure therefore makes it possible to obtain a coating 6 that is more mechanically resistant than a structure comprising a number greater than two interfaces.
[0081] The thickness of the coating 6 is between 300 and 500 μm, preferably between 350 and 450 μm.
[0082] Preferably, the thickness of the first layer 7 is between 100 and 200 μm.
[0083] Preferably, the thickness of the second layer 8 is between 100 and 200 μm.
[0084] Coating 6 is obtained using a very high-speed laser material deposition technique called EHLA.
[0085] In the present invention, the term “extreme high-speed laser application process” means a thermal projection technique also known under the English name “Extreme high-speed laser application process” and under the acronym EHLA.
[0086] With reference to Figure 3, the EHLA technique is based, like the Laser Cladding technique from which it derives, on the use of a high-power industrial laser 9 to melt and / or weld metal powders. The powders entrained by a gas, such as argon, form a powder flow 10 projected onto a substrate, thus creating a superposition of metallurgical bonds. This process allows the creation of a heat-affected zone 1 1 with the substrate ensuring good adhesion to the substrate, such as the first and second external surfaces 2a, 3a.
[0087] The EHLA laser deposition technique allows a deposition speed of up to 200 m / min and a surface area of up to 500 cm to be achieved. 2 / min, which is 100 times faster than conventional laser cladding. Indeed, certain parameters such as laser power or powder flow rate are higher.
[0088] Unlike the conventional Laser Cladding technique, in the EHLA technique, the particles are melted before coming into contact with the substrate, approximately 1 mm from the substrate. The entire powder flow 10 converges towards a region 12 at a distance from the substrate. The particles present in the powder flow 10 thus melted are then transported by the gas and fall into the melting pool 13. Since the substrate is also already heated by the laser 9, the heat-affected zone 11, which corresponds to a melting zone between a portion of the projected powder and a portion of the substrate, is finer than in the Laser Cladding process, and the energy absorbed by the substrate is less.
[0089] The very thin, or even non-existent, heat-affected zone 1 1 obtained via the EHLA technique makes it possible, during the formation of the coating 6, not to deform the material of the brake disc 1 , such as cast iron, on which the coating 6 is formed, and not to modify its properties, in particular its properties of resistance to deformation.
[0090] Such a coating 6 obtained by the EHLA technique has optimized mechanical resistance properties, in particular in the face of thermomechanical stresses and wear, which makes it possible to limit the emission of polluting particles by the brake disc 1 during braking as well as outside the braking phases of the motor vehicle.
[0091] The invention also relates to a method of manufacturing a brake disc as previously described, comprising the formation of the first layer 7 and the second layer 8 of the coating 6 by the very high speed laser material deposition technique known as EHLA.
[0092] Advantageously, the manufacturing method comprises the formation of the coating 6 on the first friction track 4, and the formation of the coating 6 on the second friction track 5.
[0093] In the manufacturing method, the material of the first layer 7 and the material of the second layer 8 are projected in powder form. The powder projected to form the first layer 7 comprises a steel having a chromium content of between 10 and 20% by mass relative to the total mass of the steel.
[0094] The powder projected to form the second layer 8 comprises steel, intended to form the matrix of the second layer 8 after projection, comprising a chromium content of between 10 and 20% by mass relative to the total mass of the steel.
[0095] The powder projected to form the second layer 8 also comprises a content of between 15 and 40% by volume of at least one carbide relative to the total volume of the second layer, the carbide intended to form reinforcements in the steel matrix after projection, being chosen from the following compounds: silicon carbide, chromium carbide, tungsten carbide, niobium carbide, titanium carbide or a mixture thereof, preferably chosen from niobium carbide, titanium carbide or a mixture thereof;
[0096] The characteristics previously described for the first layer 7 apply to the powder intended to form the first layer 7.
[0097] The characteristics previously described for the second layer 7 apply to the powder intended to form the second layer 8.
[0098] Preferably, the particle size of the powder intended to form the first layer 7 and of the powder intended to form the second layer 8 is between 10 and 60 μm.
[0099] Preferably, the particles of the powder intended to form the first layer 7 and of the powder intended to form the second layer 8 are predominantly spherical in shape.
[0100] The material of the second layer 8 in powder form preferably incorporates the carbide(s) in cermet form.
[0101] Cermet means a powder comprising ceramic reinforcements incorporated in a metallic phase.
[0102] In one example, the cermet may comprise carbide particles inserted into a matrix comprising iron and chromium, thereby forming agglomerates.
[0103] Preferably, the cermet matrix comprises predominantly iron and chromium.
[0104] By majority, we mean a matrix whose sum of iron and chromium contents represents a value greater than or equal to 50% by weight of the cermet.
[0105] Preferably, the step of forming the second layer 8 of the manufacturing method comprises the use of cermets.
[0106] In other words, the powder material used to form the second layer 8 of the coating 6 incorporates the carbide(s) in the form of cermet. The use of cermets makes it possible to produce a regular deposit of constant thickness.
[0107] The integration of carbides in the form of spherical cermet in the steel facilitates their deposition by projection.
[0108] Preferably, the manufacturing method comprises a machining step carried out after the formation of the coating 6 in order to standardize its surface which may be irregular and to adjust its thickness.
[0109] After machining, the thickness of the coating 6 is between 300 and 500 μm, preferably between 350 and 450 μm.
[0110] It may be provided that such a brake disc is used in a transport vehicle other than a motor vehicle, and is particularly applied to the aeronautical or railway sector.
[0111] Examples:
[0112] Example 1: Two-layer coating 430L + 30 vol% NbC by EHLA projection
[0113] The coating of Example 1 was formed on a GJL 150 lamellar graphite cast iron brake disc. The coating comprises a first layer arranged in contact with the cast iron and made of 430L stainless steel. A second layer, arranged on the first layer, consists of a 430L steel matrix and niobium carbide reinforcements. The niobium carbide content is 30% by volume relative to the total volume of the second layer.
[0114] The deposition of the first layer and the deposition of the second layer were carried out successively by projection of the material of the first layer and the second layer in powder form using the EHLA technique.
[0115] In particular, the second layer was formed by spraying a powder mixture comprising 430L steel powder and niobium carbide powder. The niobium carbide powder was sprayed in the form of a cermet, i.e. comprising niobium carbide particles inserted into a matrix comprising iron and chromium to form agglomerates. The cermet-type powder used incorporates 80% by weight of niobium carbide and 20% by weight of FeCr relative to the total weight of the cermet.
[0116] A machining step was carried out in order to rectify the thickness obtained after projection. Considering the irregular surface of the first layer, the coating obtained after machining has a thickness between 350 and 400 pm.
[0117] The addition of niobium carbide to 430L steel increases the hardness of the second layer compared to the first layer. The resulting average hardness of the second layer is 485 HV1. Thermal damage tests and particle emission measurements during braking have shown the absence of cracks and the reduction of particle emissions.
[0118] The coated brake disc obtained using the EHLA technique therefore provides excellent capabilities in terms of resistance to thermal damage and in terms of particle emissions during braking.
[0119] Example 2: Two-layer coating 430L + 20 vol% TiC by EHLA projection
[0120] The coating of Example 2 was also formed on a brake disc made of GJL 150 lamellar graphite cast iron. The coating comprises a first layer arranged in contact with the GJL cast iron and made of 430L stainless steel. A second layer, arranged on the first layer, consists of a 430L steel matrix and titanium carbide reinforcements. The titanium carbide content is 20% by volume relative to the total volume of the second layer.
[0121] The deposition of the first layer and the deposition of the second layer were carried out successively by powder projection using the EHLA technique.
[0122] In particular, the second layer was formed by spraying a powder mixture comprising 430L steel powder and titanium carbide powder. The titanium carbide powder was sprayed in the form of a cermet, i.e. comprising titanium carbide particles inserted into a matrix comprising iron and chromium to form agglomerates. The cermet-type powder used incorporates 70% by mass of titanium carbide and 30% by mass of FeCr relative to the total mass of the cermet.
[0123] Similar to Example 1, a machining step was carried out in order to rectify the thickness obtained after projection. The coating obtained after machining has a thickness between 440 and 470 μm.
[0124] Thermal damage tests and particle emission measurements during braking have shown the absence of cracks and the reduction of particle emissions.
[0125] The coated brake disc obtained using the EHLA technique therefore provides excellent capabilities in terms of resistance to thermal damage and in terms of particle emissions during braking.
Claims
CLAIMS 1. Brake disc for a motor vehicle comprising at least one external surface (2a, 3a) comprising a coating (6), the coating (6) comprising: a first layer (7) arranged at least partially on the external surface (2a, 3a), the first layer (7) comprising a steel having a chromium content of between 10 and 20% by mass relative to the total mass of the steel;a second layer (8) arranged on the first layer (7), the second layer (8) comprising a steel matrix having a chromium content of between 10 and 20% by mass relative to the total mass of the steel, and a content of between 15 and 40% by volume of at least one carbide relative to the total volume of the second layer, the carbide being chosen from the following compounds: silicon carbide, chromium carbide, tungsten carbide, niobium carbide, titanium carbide or a mixture thereof, preferably chosen from niobium carbide, titanium carbide or a mixture thereof; the coating (6) being obtained according to a very high speed laser material deposition technique known as EHLA.; 2. Brake disc according to claim 1, in which the steel of the first layer (7) and / or the steel of the second layer (8) is a ferritic steel, preferably a ferritic steel consisting of a chromium content of between 16 and 18% by mass, a silicon content of less than or equal to 1% by mass, a nickel content of less than or equal to 0.6% by mass, a manganese content of less than or equal to 1% by mass, a carbon content of less than or equal to 0.08% by mass, a molybdenum content of less than or equal to 1% by mass, a phosphorus content of less than or equal to 0.045% by mass, a sulfur content of less than or equal to 0.03% by mass, a titanium content of less than or equal to 0.01% by mass, optionally other additional elements such as copper, vanadium, niobium, or tin, the remainder being iron as well as unavoidable impurities.
3. Brake disc according to claim 1 or 2, wherein the second layer (8) comprises a titanium carbide content of between 15 and 25% by volume, preferably between 17 and 23% by volume, more preferably between 19 and 21% by volume, relative to the total volume of the second layer (8).
4. Brake disc according to claim 1 or 2, wherein the second layer (8) comprises a niobium carbide content of between 25 and 35% by volume, preferably between 27 and 33% by volume, more preferably between 29 and 31% by volume, relative to the total volume of the second layer (8).
5. Brake disc according to claim 1 or 2, wherein the second layer (8) comprises a mixture of carbides, the content of each carbide in the mixture of carbides being between 5 and 20% by volume, preferably between 5 and 10% by volume, relative to the total volume of the second layer (8).
6. Brake disc according to claim 5, in which the second layer (8) comprises a mixture of niobium carbide and titanium carbide, the niobium carbide content being between 5 and 20% by volume, preferably between 5 and 10% by volume relative to the total volume of the second layer, and a titanium carbide content of between 5 and 20% by volume, preferably between 5 and 10% by volume relative to the total volume of the second layer (8).
7. Brake disc according to any one of the preceding claims, wherein the material of the brake disc (1) on which the coating (6) is arranged is cast iron, preferably cast iron with lamellar graphite.
8. Brake disc according to any one of the preceding claims, comprising first and second opposite faces (2, 3) respectively comprising first and second external surfaces (2a, 3a), each of the first and second external surfaces (2a, 3a) comprising a friction track (4, 5) intended to cooperate with a brake pad, the coating (6) being arranged at least partially on the friction tracks (4, 5), preferably only arranged on the friction tracks (4, 5).
9. Method of manufacturing a brake disc according to any one of the preceding claims, comprising the formation of the first layer (7) and the second layer (8) of the coating (6) by a very high speed laser material deposition technique known as EHLA.
10. A manufacturing method according to claim 9, wherein the step of forming the second layer (8) of the manufacturing method comprises the use of cermets. 1 1. Motor vehicle comprising at least one brake disc (1) according to any one of claims 1 to 8.