Disc for disc brakes and method for manufacturing a disc for disc brakes

Abstract

The present invention relates to a disc (1) for disc brakes, comprising a braking band (2) provided with two opposite braking surfaces (2a, 2b), the braking band (2) being made of gray cast iron or steel, said disc comprising: a base layer (30), which covers at least one of the two braking surfaces (2a, 2b) of the braking band (2), wherein the base layer (30) comprises nickel-free steel, or steel having a nickel content not exceeding 15% by weight, or not exceeding 7.5% by weight, or not exceeding 5% by weight, and at least one carbide selected from titanium carbide (TiC), tungsten carbide (WC), chromium carbide, niobium carbide (NbC), molybdenum carbide (Mo2C), silicon carbide (SiC), the steel of the base layer (30) comprising at least 10% by weight of chromium (Cr), and an intermediate layer (300) interposed between the base layer (30) and at least one of the two braking surfaces (2b, 2b) of the braking band (2), wherein the intermediate layer (300) consists of nickel-free steel, or steel with a nickel content not exceeding 15% by weight, or not exceeding 7.5% by weight, or not exceeding 5% by weight.

Description

[0001] DISC FOR DISC BRAKES AND METHOD FOR MANUFACTURING A

[0002] DISC FOR DISC BRAKES

[0003] Description

[0004] Field of the invention

[0005] The present invention relates to a disc for disc brakes and to a method for manufacturing a disc for disc brakes.

[0006] Background art

[0007] A brake disc of a disc braking system of a vehicle comprises an annular structure, or braking band, and a central fixing element, known as the bell, by means of which the disc is fixed to the rotating part of a vehicle suspension, e.g., a hub. The braking band is provided with opposite braking surfaces adapted to cooperate with friction elements (brake pads), housed in at least one caliper body placed straddling such a braking band and integral with a non-rotating component of the vehicle suspension. The controlled interaction between the opposite brake pads and the opposite braking surfaces of the braking band determines a braking action through friction, which allows the vehicle to decelerate or stop.

[0008] The brake disc is generally made of gray cast iron or steel. Indeed, this material allows obtaining good braking performance (especially in terms of limiting wear) at a relatively low cost. Discs made of carbon or carbon ceramic materials offer much greater performance but at a much higher cost.

[0009] The limits of traditional discs, made of cast iron or steel, are related to excessive wear. As for the discs made of gray cast iron, another very negative aspect is related to excessive surface oxidation, resulting in the formation of rust. This aspect impacts both the performance of the brake disc and the appearance thereof, because the rust on the brake disc is unacceptable for users from an aesthetic point of view.

[0010] Attempts have been made to tackle such problems by providing discs made of gray cast iron or steel with a protective coating. The protective coating, on the one hand, serves to reduce disc wear and, on the other, to protect the base of gray cast iron from surface oxidation, thereby preventing the formation of a layer of rust.

[0011] However, the protective coatings currently available and applied on the discs, while offering wear resistance, are subject to flaking which causes the detachment thereof from the disc itself. Furthermore, such coatings are prone to the generation of thermal cracks during use and to the presence of cracks during the application thereof.

[0012] Flaking can contribute to the release, through rubbing, of nickel particles, a metal which greatly contributes to sensitization phenomena in the population .

[0013] However, in the field of steel production for brake discs, to date, the presence of nickel is considered essential, because it increases the strength and toughness of steel. Furthermore, nickel increases the resistance of steel to oxidation and corrosion, but, more importantly, nickel increases the abrasive resistance and heat resistance of steel, aspects which are highly relevant for the stresses to which brake discs are subjected in use.

[0014] Therefore, the need is particularly felt for discs made of gray cast iron or steel which are capable of reducing the release of nickel particles, but at the same time which are capable of ensuring adequate thermal and mechanical performance, including high resistance to disc wear and reliability over time.

[0015] Summary of the invention The problem above is solved by a disc for disc brakes and by a method for manufacturing a disc for disc brakes as outlined in the appended claims, the definitions of which form an integral part of the present description.

[0016] A first object of the invention is a disc for disc brakes, comprising a braking band provided with two opposite braking surfaces, the braking band being made of gray cast iron or steel, said disc comprising: a base layer which covers at least one of the two braking surfaces of the braking band, wherein the base layer comprises nickel-free steel, or steel having a nickel content not exceeding 15% by weight, or not exceeding 7.5% by weight, or not exceeding 5% by weight, and at least one carbide selected from titanium carbide (TiC), tungsten carbide (WC), chromium carbide, niobium carbide (NbC), molybdenum carbide (Mo2C), silicon carbide (SiC), the steel of the base layer (30) comprising at least 10% by weight of chromium (Cr), and an intermediate layer interposed between the base layer and at least one of the two braking surfaces of the braking band, wherein the intermediate layer consists of nickel-free steel, or steel with a nickel content not exceeding 15% by weight, or not exceeding 7.5% by weight, or not exceeding 5% by weight.

[0017] A second object of the present invention is a method for manufacturing a brake disc, comprising the following operating steps: a) providing a brake disc comprising a braking band provided with two opposite braking surfaces, the braking band being made of gray cast iron or steel; al) after step a), depositing on at least one of the two opposite braking surfaces an intermediate layer consisting of nickel-free steel, or steel having a nickel content not exceeding 15% by weight, or not exceeding 7.5% by weight, or not exceeding 5% by weight; b) after step al), depositing a particle composition comprising, or consisting of, MxCy-FeCr and nickel-free steel, or having a nickel content not exceeding 15% by weight, or not exceeding 7.5% by weight, or not exceeding 5% by weight, wherein M is selected from Ti, W, Cr, Nb, Mo, Si, x is an integer selected from 1, 2, and 3, and y is an integer selected from 1 and 2, on the intermediate layer of at least one of said braking surfaces by means of a laser deposition technique selected from: LMD (Laser Metal Deposition), HSLMD (High-Speed Laser Metal Deposition), High-Speed Laser Cladding, Extreme High-Speed Application (EHLA), and Top Speed Cladding, forming a base layer which covers at least one of the two braking surfaces of the braking band.

[0018] A further object of the present invention is a disc for disc brakes obtainable by the method described above.

[0019] The disc object of the present invention advantageously allows reducing the release of nickel particles and, at the same time, is capable of ensuring adequate or equivalent thermal and mechanical performance.

[0020] To better understand the invention and appreciate its advantages, some exemplary and non-limiting embodiments thereof will be described below with reference to the accompanying drawings.

[0021] Brief description of the drawings

[0022] Figure 1 shows a top plan view of a disc brake according to an embodiment of the present invention.

[0023] Figure 2 shows a section view of the disc of Figure 1 taken along section line II-II indicated therein, according to an embodiment of the present invention. Figure 3 shows a section view of a half-portion of a braking band according to an embodiment of the present invention.

[0024] Figure 4 shows a section view of a half-portion of a braking band according to a further embodiment of the present invention.

[0025] The elements or parts of elements common to the embodiments described below will be indicated by the same reference numerals.

[0026] Detailed description of the invention

[0027] In the following description, the expression "nickel-free steel" denotes a steel that can comprise nickel up to 0.2% by weight.

[0028] With reference to the aforesaid figures, reference numeral 1 indicates, as a whole, a disc for disc brakes according to the present invention.

[0029] The disc 1 comprises a braking band 2, provided with two opposite braking surfaces 2a and 2b, each of which at least partially defines one of the two main faces of the disc.

[0030] The braking band 2 is made of gray cast iron or steel.

[0031] Preferably, the braking band 2 is made of gray cast iron. Preferably, the entire disc 1 is made of gray cast iron. Therefore, in the following description, reference will be made to a disc made of gray cast iron, without however excluding the possibility that it is made of steel.

[0032] The disc 1 is provided with a base layer 30 which covers at least one of the two braking surfaces 2a, 2b of the braking band 2. In accordance with an embodiment, said base layer 30 is made in direct contact with said braking surfaces 2a, 2b.

[0033] According to an embodiment of the present invention, the base layer 30 comprises steel having a nickel content not exceeding 15%, preferably not exceeding 7.5%, more preferably not exceeding 5%. According to this embodiment, preferably, the steel of the base layer 30 has a nickel content of less than 15%, more preferably less than 7.5%, even more preferably less than 5%.

[0034] According to another embodiment of the present invention, the base layer 30 comprises nickel-free steel. This allows to limit, or even avoid, the dispersion of nickel particles over the life of the brake disc 1. In both of the aforesaid embodiments, the steel of the base layer 30 comprises at least 10% by weight of chromium (Cr).

[0035] In accordance with both of the aforesaid embodiments, the base layer 30 further comprises at least one carbide selected from: titanium carbide (TiC), tungsten carbide (WC), chromium carbide (e.g., Cr3C2), niobium carbide (NbC), molybdenum carbide (Mo2C), silicon carbide (SiC).

[0036] In accordance with an embodiment, said at least one carbide is incorporated in the steel.

[0037] In accordance with an embodiment, the base layer 30 consists of nickel-free steel, or steel having a nickel content not exceeding 15% by weight, or not exceeding 7.5% by weight, or not exceeding 5% by weight, and at least one carbide selected from titanium carbide (TiC), tungsten carbide (WC), chromium carbide, niobium carbide (NbC), molybdenum carbide (Mo2C), silicon carbide (SiC), the steel of the base layer 30 comprising at least 10% by weight of chromium (Cr).

[0038] It is apparent that those skilled in the art know what is meant when referring to percentages of nickel content or any other component of the steel alloy or cast iron. For example, reference is generally made to the mass percent content with respect to the total alloy content. Therefore, in the remainder of the present disclosure, particular calculations of percentages will be specified only should they deviate from the definition given above; where not specified, the indicated percentages should be considered as understood by those skilled in the art.

[0039] Advantageously, the base layer 30 is the result of the metallurgical bond which is created between at least one of said braking surfaces 2a, 2b and a particle composition deposited on said braking surface 2a, 2b by means of at least one laser beam. Said particle composition comprises, or consists of, MxCy- FeCr and nickel-free steel, or having a nickel content not exceeding 15% by weight, or not exceeding 7.5% by weight, or not exceeding 5% by weight, wherein M is selected from Ti, W, Cr, Nb, Mo, Si, x is an integer selected from 1, 2 and 3, and y is an integer selected from 1 and 2.

[0040] With further advantage, the base layer 30 is formed by depositing the aforesaid particle composition using a laser deposition technique selected from LMD (Laser Metal Deposition), HSLMD (High Speed Laser Metal Deposition), High Speed Laser Cladding, Extreme High Speed Application (EHLA) and Top Speed Cladding, on at least one of the two braking surfaces 2a, 2b, of the above-described particle composition.

[0041] The term "Laser Cladding" advantageously denotes the formation of a metallurgical bond between the substrate and the layers deposited, or welded, above said substrate by means of one or more laser beams.

[0042] Preferably, MxCy-FeCr is a sintered and agglomerated particle material. Preferably, MxCy-FeCr is in powder form.

[0043] Preferably, MxCy-FeCr has a weight ratio of carbide to FeCr between 20:80 and 80:20, e.g., between 30:70 and 70:30, or between 40:60 and 60:40.

[0044] In accordance with a preferred embodiment, the steel of the base layer 30 comprises at least titanium carbide (TiC). Preferably, said base layer 30 is the result of the metallurgical bond which is created between at least one of said braking surfaces 2a, 2b and a particle composition deposited on said braking surface 2a, 2b by means of at least one laser beam, wherein said particle composition comprises, or consists of, TiC-FeCr and nickel-free steel, or having a nickel content not exceeding 15% by weight, or not exceeding 7.5% by weight, or not exceeding 5% by weight. The presence of one or more carbides in the base layer 30 allows conferring adequate mechanical strength and resistance to wear.

[0045] In accordance with an embodiment, the steel of the base layer 30 can include one or more metal oxides and / or ceramic materials, for example it can include a mixture of aluminum oxides AI2O3.

[0046] Preferably, the base layer 30 has a thickness between 30 μm and 1500 μm, for example between 50 μm and 300 μm, or between 800 μm and 1200 μm.

[0047] The steel of the base layer 30 comprises at least 10% by weight of chromium (Cr), for example between 10% and 25% by weight of chromium.

[0048] In accordance with an embodiment of the invention, the steel of the base layer 30 comprises at least 15% by weight of chromium, for example between 15% and 25% by weight or between 20% and 25% by weight or between 16% and 18% by weight of chromium.

[0049] Preferably, moreover, the steel of the base layer 30 comprises manganese (Mn) in an amount not exceeding 5% by weight, for example between 0.5% and 5% by weight or between 0.5% and 2% by weight, extremes included, so as to at least partially compensate for the lack of the steel alloy properties generally conferred by the presence of nickel, increasing mechanical strength.

[0050] In accordance with an embodiment, the steel of the base layer 30 comprises at least 55% by weight of iron (Fe), e.g., at least 65% by weight of iron or at least 75% by weight of iron, for example an amount of iron between 65% to 85% by weight or between 75% to 80% by weight.

[0051] In accordance with an embodiment, in order to compensate for the low amount or the complete absence of nickel and to obtain adequate performance for a brake disc, the steel of the base layer 30 consists of 10 to 20% by weight of chromium (Cr), preferably between 16% to 18% by weight of chromium (Cr), at most 1.5% by weight of silicon (Si), at most 2% by weight of manganese (Mn), at most 0.03% by weight of carbon (C), and for the remainder of iron (Fe), i.e., for the remaining percentage by weight of iron.

[0052] In accordance with an embodiment of the invention, in order to compensate for the low amount or the complete absence of nickel and obtain adequate performance for a brake disc, the steel of the base layer 30 has a molybdenum content between 0.5% and 3% by weight, extremes included, and a manganese content between 0.1% and 5% by weight, extremes included. The presence of molybdenum and manganese in the aforesaid percentages allows obtaining adequate corrosion resistance and at the same time adequate mechanical strength.

[0053] In accordance with an embodiment, an intermediate layer 300 of nickel-free steel is interposed between the base layer 30 and at least one of the two braking surfaces 2a, 2b of the braking band 2.

[0054] In accordance with an alternative embodiment, an intermediate layer 300 of steel comprising nickel in an amount not exceeding 15%, or not exceeding 7.5%, or not exceeding 5%, is interposed between the base layer 30 and at least one of the two braking surfaces 2a, 2b of the braking band 2. Preferably, if the base layer 30 is nickel-free, the intermediate layer 300 has a nickel content of at least 5% and not exceeding 15%, or less than 15%.

[0055] The presence of the intermediate layer 300 allows obtaining a disc with adequate mechanical features, but at the same time with a reduced environmental impact, by virtue of the presence of the base layer 30. Preferably, the intermediate layer 300 has a thickness between 30 μm and 1000 μm, for example between 60 μm and 200 μm.

[0056] In accordance with an embodiment, an auxiliary ferritic-nitrecarburized layer or an auxiliary ferroalumination layer is interposed between one of the two braking surfaces 2a, 2b of the braking band 2 and the base layer 30, or between one of the two braking surfaces 2a, 2b of the braking band 2 and the intermediate layer 300, or between the intermediate layer 300 and the base layer 30.

[0057] Advantageously, the brake disc is provided with a portion adapted to fix the disc to a vehicle, consisting of an annular portion 4 which is arranged centrally to the disc 1 and concentric to the braking band 2. The fixing portion 4 supports the connection element 5 to the wheel hub (i.e., the bell). The bell can be made in one piece with the annular fixing portion (as shown in the accompanying drawings) or can be made separately and then fixed by means of appropriate connection elements to the fixing portion.

[0058] The annular fixing portion 4 can be made of the same material as the braking band, i.e., of gray cast iron, or another appropriate material. The bell 5 can also be made of gray cast iron or other appropriate material. In particular, the entire disc (i.e., the braking band, the fixing portion, and the bell) can be made of gray cast iron.

[0059] Preferably, the braking band 2 is made by casting. Similarly, when they are made of gray cast iron, the fixing portion and / or the bell can be made by casting.

[0060] The annular fixing portion can be made in a single body with the braking band (as shown in the accompanying drawings) or can be made as a separate body, mechanically connected to the braking band.

[0061] As already mentioned above, the base layer 30 and, if present, the intermediate layer 300 cover at least one of the two braking surfaces 2a, 2b of the braking band.

[0062] In the following, the term "coating" will refer to the base layer 30 or to the assembly given by the base layer 30 and the intermediate layer 300.

[0063] Preferably, as shown in Figure 2, the disc 1 is provided with a coating which covers both braking surfaces 2a and 2b of the braking band 2.

[0064] In particular, the coating can cover the braking band on a single braking surface, or on both. In accordance with solutions not shown in the accompanying drawings, the coating can also extend to other parts of the disc 1 such as the annular fixing portion 4 and the bell 5, up to cover the entire surface of the disc 1. In particular, the coating can cover - in addition to the braking band - only the fixing portion or only the bell. The choice is dictated by essentially aesthetic reasons, in order to have an even color and / or finishing on the entire disc or between some portions thereof.

[0065] Advantageously, the deposition of the particle material for the formation of the coating can be performed in a differentiated manner on the surface of the disc, at least in terms of the coating thickness.

[0066] At the braking band, the coating can be made with the same thickness on the two opposite braking surfaces. Alternative solutions can be provided wherein the coating is made by differentiating the thicknesses between the two braking surfaces of the braking band.

[0067] The brake disc 1 is preferably, but not necessarily, manufactured by the method according to the invention which will be described below. In accordance with a first embodiment, the method according to the present invention comprises the following operating steps: a) providing a brake disc 1 comprising a braking band 2 provided with two opposite braking surfaces 2a, 2b, the braking band being made of gray cast iron or steel; b) depositing a particle composition comprising, or consisting of, MxCy-FeCr and nickel-free steel, or having a nickel content not exceeding 15% by weight, or not exceeding 7.5% by weight, or not exceeding 5% by weight, wherein M is selected from Ti, W, Cr, Nb, Mo, Si, x is an integer selected from 1, 2, and 3, and y is an integer selected from 1 and 2, on at least one of said braking surfaces 2a, 2b by means of a laser deposition technique selected from: LMD (Laser Metal Deposition), HSLMD (High-Speed Laser Metal Deposition), High-Speed Laser Cladding, Extreme High-Speed Application (EHLA), and Top Speed Cladding, forming a base layer (30) which covers at least one of the two braking surfaces (2a, 2b) of the braking band (2).

[0068] In accordance with different embodiments, the carbide in MxCy-FeCr is selected from titanium carbide (TiC), tungsten carbide (WC), chromium carbide (preferably, Cr3C2), niobium carbide (NbC), molybdenum carbide (Mo2C), silicon carbide (SiC).

[0069] In accordance with a preferred embodiment, the particle composition comprises, or consists of, TiC- FeCr and nickel-free steel, or having a nickel content not exceeding 15% by weight, or not exceeding 7.5% by weight, or not exceeding 5% by weight.

[0070] Advantageously, step b) of the aforesaid method allows a carbide, preferably TiC, to be incorporated in the steel and the steel itself to be enriched with Fe and Cr, forming the base layer 30.

[0071] In accordance with an embodiment, particles of MxCy-FeCr are dispersed in a matrix of steel particles, preferably MxCy-FeCr is an agglomerated and / or sintered material.

[0072] In accordance with an embodiment, said particle composition comprises MxCy-FeCr in an amount between 10 and 40% by weight, preferably between 15 and 35% by weight, with respect to the weight of the particle composition .

[0073] In accordance with an embodiment, MxCy-FeCr has a weight ratio of carbide to FeCr between 20:80 and 80:20, for example between 30:70 and 70:30, or between 40:60 and 60:40. In accordance with an embodiment, step b) is carried out using at least a first laser beam having a power between 6 and 30 kW, preferably between 10 and 30 kW, preferably said laser beam being of the Gaussian or top-hat or top-hat ring type. Advantageously, said first laser beam performs the deposition, or welding, of the particle composition on at least one of the two braking surfaces 2a, 2b.

[0074] In accordance with an embodiment, the deposition rate of said particle composition is between 1 m2 / h and 14 m2 / h, for example between 1 m2 / h and 8 m2 / h.

[0075] In accordance with an embodiment, the flow (powder flow rate) with which the particle composition is deposited is between 20 g / min and 400 g / min.

[0076] In accordance with an embodiment, during step b), upstream of the use of said first laser beam, a further laser beam is employed which performs the pre-treatment of at least one of said braking surfaces 2a, 2b, said further laser beam having a power comprised between 1 and 15 kW, preferably between 1 and 15 kW. Preferably, said further laser beam is of the Gaussian or top-hat or top-hat ring type. Said pre-treatment can include a pre-heating, for example to reduce thermal gradients and deformations (increasing the window available for varying the process parameters and ensuring greater process stability), and / or a cleaning of the surface, and / or a homogenization of the surface.

[0077] In accordance with an embodiment, during step b), downstream of the use of said first laser beam, a further laser beam having a power between 1 and 20 kW is employed, which performs a post-treatment of at least one of said braking surfaces 2a, 2b on which the particle composition was previously deposited. Preferably, said further laser beam is of the Gaussian or top-hat or top-hat ring type. Said post-treatment can include a heating, for example to reduce thermal gradients and deformations or to modify microstructural features or to reduce undulation and roughness.

[0078] In accordance with an embodiment, said first laser beam and further laser beams have a spot size on said at least one braking surface 2a, 2b which is comprised between 1 mm and 10 mm.

[0079] In accordance with an embodiment, the steel of the particle composition can include at least one carbide selected from titanium carbide (TiC)), tungsten carbide (WC), chromium carbide (e.g., Cr3C2), niobium carbide (NbC), molybdenum carbide (Mo2C), silicon carbide (SiC). This means that, according to this embodiment, one or more carbides selected from those indicated above are included within the steel of the particle composition. The inclusion of one or more carbides is obtained by techniques known to the person skilled in the art for the inclusion of carbides in steel, e.g., the carbides are dissolved in the alloy.

[0080] In accordance with an embodiment, the steel of the particle composition can include one or more metal oxides and / or ceramic materials, for example it can include a mixture of aluminum oxides AI2O3.

[0081] The use of a laser deposition technique, selected from those indicated above, together with the use of a particle composition comprising MxCy-FeCr (preferably TiC-FeCr, preferably in agglomerated and sintered form) and steel, advantageously allows reducing the emission of dust during braking, increasing corrosion resistance, reducing the presence of cracks in the base layer 30, reducing the porosity generated during the deposition of the base layer 30, reducing the generation of cracks during braking.

[0082] In accordance with an embodiment, the method according to the present invention further comprises a step al) which is carried out downstream of step a) and upstream of step b). Said step al) includes depositing on at least one of the two opposite braking surfaces 2a, 2b an intermediate layer 300 consisting of nickel-free steel, or steel having a nickel content not exceeding 15% by weight, or not exceeding 7.5% by weight, or not exceeding 5% by weight. It follows that, in accordance with this embodiment, the base layer 30, during step b), is formed above said intermediate layer 300.

[0083] In accordance with an embodiment, step al) of deposition of the intermediate layer 300 includes depositing a composition in particle form consisting of nickel-free steel, or steel having a nickel content not exceeding 15% by weight, or not exceeding 7.5% by weight, or not exceeding 5% by weight, by means of a laser deposition technique selected from: LMD (Laser Metal Deposition) , HSLMD (High Speed Laser Metal Deposition), High Speed Laser Cladding, Extreme High Speed Application (HELA) and Top Speed Cladding.

[0084] In accordance with an embodiment, the step al) is carried out using at least a first laser beam having a power between 6 and 30 kW, preferably between 10 and 30 kW, preferably said laser beam being of the Gaussian or top-hat or top-hat ring type. Advantageously, said first laser beam performs the deposition of the composition in particle form on at least one of said braking surfaces 2a, 2b.

[0085] In accordance with an embodiment, the deposition rate of said composition in particle form is between 1 m2 / h and 14 m2 / h, for example between 1 m2 / h and 8 m2 / h.

[0086] In accordance with an embodiment, the flow (powder flow rate) with which the composition in particle form is deposited is between 20 g / min and 400 g / min.

[0087] In accordance with an embodiment, during step al), upstream of the use of said first laser beam, a further laser beam is employed which performs the pre-treatment of at least one of said braking surfaces 2a, 2b, said further laser beam having a power comprised between 1 and 15 kW, preferably comprised between 1 and 15 kW. Preferably, said further laser beam is of the Gaussian or top-hat or top-hat ring type. Said pre-treatment can include a pre-heating, for example to reduce thermal gradients and deformations (increasing the window available for varying the process parameters and ensuring greater process stability), and / or a cleaning of the surface, and / or a homogenization of the surface.

[0088] In accordance with an embodiment, during step al), downstream of the use of said first laser beam, a further laser beam having a power between 1 and 20 kW is employed, which performs a post-treatment of at least one of said braking surfaces 2a, 2b on which the composition in particle form was previously deposited. Preferably, said further laser beam is of the Gaussian or top-hat or top-hat ring type. Said post-treatment can include a heating, for example to reduce the thermal gradients and make the surface uniform before forming the base layer 30 during the step b) described above.

[0089] In accordance with an embodiment of the method, a step el) is provided for depositing an auxiliary ferritic-nitrocarburization layer between one of the two braking surfaces 2a, 2b of the braking band and the base layer 30, and / or between one of the two braking surfaces 2a, 2b of the braking band and the intermediate layer 300, and / or between the intermediate layer 300 and the base layer 30.

[0090] In accordance with an embodiment of the method, a step e2) is provided for depositing an auxiliary ferroalumination layer between one of the two braking surfaces 2a, 2b of the braking band and the base layer 30, and / or between one of the two braking surfaces 2a, 2b of the braking band and the intermediate layer 300, and / or between the intermediate layer 300 and the base layer 30.

[0091] In accordance with an embodiment, the method includes depositing a ferritic-nitrocarburization auxiliary layer and a ferroalumination auxiliary layer between one of the two braking surfaces 2a, 2b of the braking band and the base layer 30, and / or between one of the two braking surfaces 2a, 2b of the braking band and the intermediate layer 300, and / or between the intermediate layer 300 and the base layer 30.

[0092] It is apparent that those described are only particular embodiments of the present invention. Those skilled in the art will be able to make all the necessary modifications to the disc and method of the present invention for the adaptation thereof to particular conditions, without however departing from the scope of protection as defined in the appended claims.

Claims

CLAIMS1. A disc (1) for disc brakes, comprising a braking band (2) provided with two opposite braking surfaces (2a, 2b), the braking band (2) being made of gray cast iron or steel, said disc comprising: a base layer (30), which covers at least one of the two braking surfaces (2a, 2b) of the braking band (2), wherein the base layer (30) comprises nickel-free steel, or steel having a nickel content not exceeding 15% by weight, or not exceeding 7.5% by weight, or not exceeding 5% by weight, and at least one carbide selected from titanium carbide (TiC), tungsten carbide (WC), chromium carbide, niobium carbide (NbC), molybdenum carbide (Mo2C), silicon carbide (SiC), the steel of the base layer (30) comprising at least 10% by weight of chromium (Cr), and an intermediate layer (300) interposed between the base layer (30) and at least one of the two braking surfaces (2b, 2b) of the braking band (2), wherein the intermediate layer (300) consists of nickel-free steel, or steel with a nickel content not exceeding 15% byweight, or not exceeding 7.5% by weight, or not exceeding 5% by weight.

2. A disc (1) according to claim 1, wherein said base layer (30) is the result of the metallurgical bond which is created between at least one of said braking surfaces (2a, 2b) and a particle composition deposited on said braking surface (2a, 2b) by means of at least one laser beam, wherein said particle composition comprises, or consists of, MxCy-FeCr and nickel-free steel, or having a nickel content not exceeding 15% by weight, or not exceeding 7.5% by weight, or not exceeding 5% by weight, wherein M is selected from Ti, W, Cr, Nb, Mo, Si, x is an integer selected from 1, 2 and 3, and y is an integer selected from 1 and 2.

3. A disc (1) according to claim 1 or 2, wherein the steel of the base layer (30) comprises at least titanium carbide (TiC), preferably said base layer (30) is the result of the metallurgical bond which is created between at least one of said braking surfaces (2a, 2b) and a particle composition deposited on said braking surface (2a, 2b) by means of at least one laser beam, wherein said particle composition comprises, orconsists of, TiC-FeCr and nickel-free steel, or having a nickel content not exceeding 15% by weight, or not exceeding 7.5% by weight, or not exceeding 5% by weight.

4. A disc (1) according to any one of the preceding claims, wherein the steel of the base layer (30) consists of chromium (Cr) in an amount between 10% and 20% by weight, silicon (Si) in an amount not exceeding 1.5% by weight, manganese (Mn) in an amount not exceeding 2% by weight, carbon (C) in an amount not exceeding 0.03% by weight, and iron for the remaining percentage by weight.

5. A disc (1) according to any one of the preceding claims, wherein said base layer (30) has a thickness between 30 μm and 1500 μm, for example between 50 μm and 300 μm or between 800 μm and 1200 μm.

6. A disc (1) according to any one of the preceding claims, wherein said intermediate layer (300) has a thickness between 30 μm and 1000 μm, for example between 60 μm and 200 μm.

7. A method for manufacturing a brake disc (1) comprising the following operating steps: a) providing a brake disc (1) comprising a braking band (2) provided with two opposite braking surfaces (2a, 2b), the braking band being made of gray cast iron or steel; al) after step a), depositing on at least one of the two opposite braking surfaces (2a, 2b) an intermediate layer (300) consisting of nickel-free steel, or steel having a nickel content not exceeding 15% by weight, or not exceeding 7.5% by weight, or not exceeding 5% by weight; b) after step al), depositing a particle composition comprising, or consisting of, MxCy-FeCr and nickel-free steel, or having a nickel content not exceeding 15% by weight, or not exceeding 7.5% by weight, or not exceeding 5% by weight, wherein M is selected from Ti, W, Cr, Nb, Mo, Si, x is an integer selected from 1, 2, and 3, and y is an integer selected from 1 and 2, on the intermediate layer (300) of at least one of said braking surfaces (2a, 2b) by means of a laser deposition technique selected from: LMD (Laser Metal Deposition), HSLMD (High-Speed Laser Metal Deposition), High-Speed Laser Cladding, Extreme High-Speed Application (EHLA), and Top Speed Cladding, forming a base layer (30) which covers at least one of the two braking surfaces (2a, 2b) of the braking band (2).

8. A method according to claim 7, wherein the carbide in MxCy-FeCr is selected from titanium carbide (TiC), tungsten carbide (WC), chromium carbide, niobium carbide (NbC), molybdenum carbide (Mo2C), silicon carbide (SiC).

9. A method according to claim 7 or 8, wherein the particle composition comprises, or consists of, TiC- FeCr and nickel-free steel, or having a nickel content not exceeding 15% by weight, or not exceeding 7.5% by weight, or not exceeding 5% by weight.

10. A method according to any one of claims 7 to9, wherein particles of MxCy-FeCr are dispersed in a matrix of steel particles, preferably MxCy-FeCr is an agglomerated and / or sintered material.

11. A method according to any one of claims 7 to10, wherein said particle composition comprises MxCy- FeCr in an amount between 10 and 40% by weight,preferably between 15 and 35% by weight.

12. A method according to any one of claims 7 to11, wherein MxCy-FeCr has a weight ratio of carbide to FeCr between 20:80 and 80:20, for example between 30:70 and 70:30, or between 40:60 and 60:40.

13. A method according to any one of claims 7 to12, wherein step b) is carried out using at least a first laser beam having a power between 6 and 30 kW, preferably said laser beam being of the Gaussian or top-hat or top-hat ring type.

14. A method according to any one of claims 7 to13, wherein: the deposition rate of said particle composition is between 1 m2 / h and 14 m2 / h, for example between 1 m2 / h and 8 m2 / h, and / or the flow with which the particle composition is deposited is between 20 g / min and 400 g / min.

15. A method according to claim 13 or 14, wherein during step b), upstream of the use of said first laser beam, a further laser beam having a power between 1 and15 kW is employed, preferably said further laser beam being of the Gaussian or top-hat or top-hat ring type, said further laser beam performing a pre-treatment of at least one of said braking surfaces (2a, 2b).

16. A method according to any one of claims 13 to15, wherein during step b), downstream of the use of said first laser beam, a further laser beam having a power between 1 and 20 kW is employed, preferably said further laser beam being of the Gaussian or top-hat or top-hat ring type, said further laser beam performing a post-treatment of at least one of said braking surfaces (2a, 2b) on which the particle composition was previously deposited.

17. A method according to any one of claims 7 to16, wherein step al) of depositing the intermediate layer (300) involves depositing a composition in particle form consisting of nickel-free steel, or steel having a nickel content not exceeding 15% by weight, or not exceeding 7.5% by weight, or not exceeding 5% by weight, by means of a laser deposition technique selected from: LMD (Laser Metal Deposition), HSLMD (High Speed Laser Metal Deposition), High Speed LaserCladding, Extreme High Speed Application (HELA) and TopSpeed Cladding.

18. A method according to claim 17, wherein step al) is carried out using at least a first laser beam having a power between 6 and 30 kW, preferably said laser beam being of the Gaussian or top-hat or top-hat ring type, said first laser beam performing the deposition of the composition in particle form on at least one of said braking surfaces (2a, 2b).

19. A method according to claim 17 or 18, wherein: the deposition rate of said composition in particle form is between 1 m2 / h and 14 m2 / h, for example between 1 m2 / h and 8 m2 / h, and / or the flow with which the composition in particle form is deposited is between 20 g / min and 400 g / min.

20. A method according to claim 18 or 19, wherein during step al), upstream of the use of said first laser beam, a further laser beam having a power between 1 and 15 kW is employed, preferably said further laser beam being of the Gaussian or top-hat or top-hat ring type, said further laser beam performing a pre-treatment of at least one of said braking surfaces (2a, 2b).

21. A method according to any one of claims 18 to 20, wherein during step al), downstream of the use of said first laser beam, a further laser beam having a power between 1 and 20 kW is employed, preferably said laser beam being of the Gaussian or top-hat or top-hat ring type, said further laser beam performing a post- treatment of at least one of said braking surfaces (2a, 2b) on which the composition in particle form was previously deposited.

22. A disc (1) for disc brakes obtainable by the method according to any one of claims 7 to 21.

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