Nickel-free steel double-layer brake disc and method for manufacturing the same

Abstract

The brake disc (1) for disc brakes consists of a brake band (2) made of grey cast iron or steel and has two opposing braking surfaces (2a, 2b), each of which defines at least a part of the two main faces of the disc (1). The brake disc comprises a completely nickel-free base layer (30) and one or more carbides in nickel-free steel, which base layer (30) covers at least one of the two braking surfaces (2a, 2b) of the brake band. An intermediate layer (300) made of nickel-free steel is interposed between the base layer (30) and at least one of the two braking surfaces (2a, 2b) of the brake band (2).

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a brake disk and a brake disk for a disk brake.

Background Art

[0002] The brake disk of a vehicle disk brake system consists of an annular structure, i.e., a brake band, and a central fixing element known as a bell, by which the disk is attached to a rotating part of the vehicle suspension, such as a hub. The brake band has opposing brake surfaces suitable for cooperating with friction elements (brake pads), and is housed in at least one gripper body arranged on both sides of the brake band and integrated with non-rotating parts of the vehicle suspension. The controlled interaction between the opposing brake pads and the opposing brake surfaces of the brake band determines the braking action by friction and enables the deceleration or stopping of the vehicle.

[0003] Generally, brake disks are made of gray cast iron or steel. In fact, this material makes it possible to obtain good braking performance (especially limited wear) at a relatively low cost. Disks made of carbon or carbon ceramic materials offer much higher performance but are much more costly.

[0004] The limitations of conventional cast iron or steel discs are related to excessive wear. As far as gray cast iron discs are concerned, another very negative aspect is related to excessive surface oxidation and the resulting rust formation. This aspect affects both the performance and appearance of the brake disc, as rust on brake discs is aesthetically unacceptable to users. To address this problem, attempts have been made to manufacture gray cast iron or steel discs with protective coatings. The protective coating reduces disc wear while protecting the gray cast iron base from surface oxidation and preventing the formation of a rust layer. Protective coatings currently available and applied to discs, while providing wear resistance, can cause peeling, leading to delamination from the disc itself.

[0005] This type of protective coating is described, for example, in patent US4715486 relating to low-wear disc brakes. Cast iron discs in particular have a coating made of particulate material deposited on the disc by impact technology with high kinetic energy. According to the first embodiment, the coating comprises 20% to 30% tungsten carbide, 5% nickel, and a mixture of chromium and tungsten carbide with the remainder.

[0006] In the case of coating application using flame spray technology, the reason why conventional protective coatings peel off aluminum or aluminum alloy discs is the presence of free carbon in the protective coating. This phenomenon also affects gray cast iron or steel discs.

[0007] A solution to the aforementioned problem is proposed by the same applicant in international application WO2014 / 097187, relating to gray cast iron or steel discs. It involves forming a protective coating on the brake surface of a brake disc obtained by depositing a particulate material consisting of 70-95 wt% tungsten carbide, 5-15 wt% cobalt, and 1-10 wt% chromium. The deposition of the particulate material is achieved by HVOF (High Velocity Oxygen Fuel) technology, HVAF (High Velocity Air Fuel) technology, or KM (Kinetic Metallization) technology.

[0008] More specifically, according to the solution provided in WO2014 / 097187, a protective coating with high bonding strength can be obtained by combining HVOF, HVAF, or KM film deposition technology with the chemical components used to form the coating, thereby ensuring a high degree of fixation to gray cast iron or steel. While the above solution can significantly reduce the peeling phenomenon of protective coatings recorded in the prior art, it cannot eliminate it completely. In fact, even in discs with protective coatings manufactured according to WO2014 / 097186, peeling and sagging of the protective coating still occur, albeit less frequently than in the prior art.

[0009] The aforementioned peeling and sagging may contribute, in particular, to the frictional release of nickel particles, a metal that significantly contributes to sensitization phenomena in groups.

[0010] However, in the specific field of manufacturing steel for brake discs, the presence of nickel has been considered essential to this day for increasing the strength and toughness of the steel. Furthermore, nickel improves the oxidation and corrosion resistance of the steel, but above all, it improves the wear resistance and heat resistance of the steel. Therefore, to this day, the presence of nickel is considered an essential element in the manufacture of cast iron or steel brake discs.

[0011] Considering both the wear resistance benefits guaranteed by protective coatings and the need to maintain the presence of nickel in the brake disc composition, the need to address the shortcomings mentioned in the prior art is very strong in this field.

[0012] In particular, there is a perceived need for gray cast iron or steel discs that can reduce the emission of nickel particles while simultaneously ensuring appropriate or equivalent thermal and mechanical performance typical of prior art brake discs, including high wear resistance and reliability over time.

[0013] In a further embodiment, there is a perceived need to manufacture steel discs that maintain the appropriate hardness of the coating while simultaneously reducing (or eliminating) the emission of nickel particles, while also reducing the consumption of resources (and therefore costs) required for manufacturing. [Overview of the project]

[0014] The need for a brake disc that can reduce the emission of nickel particles while simultaneously ensuring appropriate or equivalent thermal and mechanical performance is satisfied by the brake disc and method for manufacturing the brake disc according to the attached independent claims. [Brief explanation of the drawing]

[0015] Further features and advantages of the present invention will become more apparent from the following description of its preferred non-limiting embodiments: [Figure 1] Figure 1 is a plan view of a disc brake according to one embodiment of the present invention. [Figure 2] Figure 2 is a cross-sectional view of the disk of Figure 1 along the line II-II shown therein, according to an embodiment of the present invention. [Figure 3] Figure 3 is a cross-sectional view of the disk of Figure 1 along the line II-II shown therein, according to a further embodiment of the present invention. [Figure 4]FIG. 4 is a cross-sectional view of half of the brake band according to an embodiment of the present invention. [Figure 5] FIG. 5 is a cross-sectional view of half of the brake band according to a second embodiment of the present invention. [Figure 6] FIG. 6 is a cross-sectional view of half of the brake band according to a third embodiment of the present invention. [Figure 7] FIG. 7 is a cross-sectional view of half of the brake band according to a fourth embodiment of the present invention. [Figure 8] FIG. 8 is a cross-sectional view of half of the brake band according to a fifth embodiment of the present invention. [[ID=第十三条]] [Figure 9] FIG. 9 is a cross-sectional view of half of the brake band according to a sixth embodiment of the present invention. [Figure 10] FIG. 10 is a cross-sectional view of half of the brake band according to a seventh embodiment of the present invention.

[0016] Elements or parts of elements common to the embodiments described below are denoted by the same reference numerals.

BEST MODE FOR CARRYING OUT THE INVENTION

[0017] Referring to the above figures, reference numeral 1 generally indicates a brake disc according to the present invention.

[0018] In this specification, when numerical percentage intervals are shown, unless otherwise specified, it is understood that the extreme values of these intervals are always included.

[0019] According to a general embodiment of the present invention shown in the accompanying figures, the brake disc 1 consists of a brake band 2 having two opposing brake surfaces 2a and 2b, and each brake surface 2a and 2b at least partially defines one of the two main surfaces of the disc.

[0020] The brake band 2 is made of gray cast iron or steel.

[0021] Preferably, the brake band 2 is made of gray cast iron. In particular, the entire disk is made of gray cast iron. Therefore, in this specification, without excluding the possibility that the disk is made of steel, the gray cast iron disk will be referred to.

[0022] The disk 1 includes a base layer 30 that covers at least one of the two brake surfaces 2a, 2b of the brake band and preferably contacts the brake surfaces 2a, 2b directly.

[0023] According to one aspect of the present invention, such a base layer 30 is composed of steel having a nickel content lower than 15% or at most equal to 15%.

[0024] According to a further aspect of the present invention, such a base layer 30 is composed of steel having a nickel content lower than 7.5% or at most equal to it, more preferably lower than 5% or at most equal to it.

[0025] According to a further aspect of the present invention, such a base layer 30 does not contain nickel at all. Thereby, during the life of the brake disk 1, the dispersion of nickel particles can be restricted, if not avoided.

[0026] Generally, in this discussion, when referring to expressions such as "nickel-free" or "without nickel", it not only means that no nickel is present, but also means that there is less nickel than the small amount of nickel that may be present due to traces or residual impurities resulting from the manufacturing process. In any case, the amount of nickel is lower than 1% for any layer, and in some cases, strictly lower than 5%.

[0027] It is clear to those skilled in the art what is meant when referring to the content of nickel or other components in steel or cast iron alloys. For example, generally, the content is referred to in mass% with respect to the total content of the alloy. Therefore, in this specification, the calculation of a specific percentage will only be specified when deviating from the above definitions.

[0028] According to one embodiment of the present invention, the steel of the base layer 30 is composed of 10% to 15% chromium (Cr), at most 1% silicon (Si), at most 4% manganese (Mn), 0.16% to 0.5% carbon (C), and the remainder being iron (Fe), i.e., the remaining weight of iron. This makes it possible to obtain a martensitic steel that does not contain nickel.

[0029] Preferably, the carbon (C) content of the steel in the base layer is 0.16 to 0.25%.

[0030] Advantageously, the aforementioned composition allows for a reduction in the proportion of carbides in the steel, enabling its use without decreasing the hardness of the coating (more details will be provided later in the text).

[0031] According to a modified version of the preferred embodiment, the chromium (Cr) content in the steel of the base layer 30 is composed of 11% to 14%, including extreme cases.

[0032] For example, according to a modified embodiment of the present invention shown in Figure 5, the base layer 30 is also composed of one or more carbides contained in nickel-free steel. Such inclusions are obtained by techniques known to those skilled in the art regarding the inclusion of carbides in steel, for example, by dissolving the carbides in the alloy.

[0033] Preferably, the one or more carbides contained consist of at least one carbide selected from the group consisting of tungsten carbide (WC), chromium carbide (preferably, but not limited to, Cr3C2), niobium carbide (NbC), and titanium carbide (TiC). It is clear that one or more carbides selected from the aforementioned group, or all of the carbides present in the present invention, may be present.

[0034] The one or more carbides included are at least one carbide selected from the group consisting of tungsten carbide (WC), chromium carbide (e.g., Cr3C2), niobium carbide (NbC), and titanium carbide (TiC).

[0035] For example, according to an advantageous embodiment shown in Figure 6, the brake disc 1 is composed of a protective surface coating 3 that covers the base layer 30 on at least one side of the two brake surfaces 2a, 2b of the brake band. Such a surface protective coating 3 is located on the side of the base layer 30 that does not face the brake surfaces 2a, 2b. Furthermore, the surface protective coating 3 is composed of at least one or more particulate carbides that can be deposited by thermal spraying techniques [e.g., HVOF (high-speed oxygen fuel) techniques, HVAF (high-speed air fuel) techniques, APS (atmospheric pulse spray) techniques], cold spray deposition techniques [e.g., KM (kinetic metallization) techniques], or laser beam deposition techniques [e.g., LMD (laser metal deposition) techniques, HSLC (high-speed laser cladding) techniques, EHLA (extremely high-speed laser application) techniques, TSC (top-speed cladding) techniques].

[0036] Therefore, the surface protective coating 3 is obtained by directly depositing one or more particulate carbides, preferably tungsten carbide (WC), chromium carbide (e.g., Cr3C2), niobium carbide (NbC), or titanium carbide (TiC) onto the disk 1 using HVOF technology, HVAF (High Velocity Air Fuel) technology, or KM (Kinetic Metallization) technology.

[0037] In a further embodiment, the surface protective coating 3 is composed of steel with a nickel content of 15% or less, or at most 7.5% or less, or at most 5% or less, or more preferably no nickel at all, and one or more carbides contained in the steel. In this variant, in other words, a nickel-free steel base layer 30 and a protective surface coating 3 consisting of the aforementioned steel and one or more carbides contained in the steel are bonded onto the cast iron strip in the order shown.

[0038] The presence of carbides deposited on the surface of steel, or carbides contained within the steel, which are substantially or completely nickel-free, imparts mechanical strength and wear resistance, and can compensate for the scarcity or complete deficiency of nickel within the steel.

[0039] In a modified example, the surface protective coating 3 is obtained by depositing a carbide composed of one or more of tungsten carbide (WC), niobium carbide (NbC), chromium carbide (e.g., Cr3C2), and titanium carbide (TiC) onto the base layer 30 using thermal spraying technology [e.g., HVOF (high-speed oxygen fuel) technology, HVAF (high-speed air fuel) technology, APS (atmospheric pulse spray) technology], cold spray deposition technology [e.g., KM (kinetic metallization) technology], or laser beam deposition technology [e.g., LMD (laser metal deposition) technology, HSLC (high-speed laser cladding) technology, EHLA (extremely high-speed laser application) technology, TSC (top-speed cladding) technology]. Therefore, it is clear that one or more carbides selected from the aforementioned group, or all of the carbides present in the present invention, may be present.

[0040] According to an advantageous embodiment, the surface protective coating 3 is composed of chromium carbide (e.g., Cr3C2) and titanium carbide (TiC).

[0041] In a modified example, the surface protective coating 3 is composed of at least one metal oxide or a mixture of metal oxides, or a mixture of a metal and a ceramic material, preferably a mixture of aluminum oxide Al2O3, or a mixture of Al2O3 and an intermetallic matrix Fe-Cr, such as Fe28Cr.

[0042] According to a modified example of an advantageous embodiment, the surface protective coating 3 comprises one or more of the following carbides: tungsten carbide (WC), niobium carbide (NbC), chromium carbide (e.g., Cr3C2), titanium (TiC), a mixture with a mixture of metal oxides, or a mixture with a mixture of metal and ceramic material, preferably a mixture of aluminum oxide Al2O3, or a mixture of Al2O3 and an intermetallic matrix Fe-Cr, e.g., Fe28Cr.

[0043] It is clear that the above-mentioned oxides or mixtures of oxides, or metals or mixtures of metals and ceramic materials, or mixtures of carbides and metal oxides are preferably deposited by the same deposition techniques for particulate carbides described above and in this paper.

[0044] Preferably, the surface protective coating 3 has a thickness between 30 μm and 150 μm, preferably between 50 μm and 90 μm.

[0045] According to one embodiment of the present invention, the steel of the base layer 30 contains 10% to 20% chromium (Cr).

[0046] According to embodiments of the present invention, the steel of the base layer 30 contains at least 15% chromium (Cr), more preferably 16% to 18% chromium.

[0047] According to one embodiment, the steel of the base layer 30 contains at least 5% manganese (Mn) to at least partially compensate for the lack of properties of steel alloys generally imparted by the presence of nickel and to increase mechanical strength, and more preferably the manganese content is 0.5% to 5%, including extreme cases.

[0048] In particular, according to the embodiment, in order to compensate for any nickel deficiency or complete absence and to obtain suitable performance as a brake disc, the steel of the base layer 30 contains 10% to 20% by weight of chromium (Cr), preferably 16% to 18% by weight of chromium (Cr), at most 1% by weight of silicon (Si), at most 2% by weight of manganese (Mn), at most 0.03% by weight of carbon (C), and the remainder being iron (Fe), i.e., the remaining weight percent of iron.

[0049] Preferably, the base layer 30 has a thickness between 20 μm and 300 μm, preferably equal to 90 μm.

[0050] According to a modified version of the present invention, in order to compensate for the low amount or complete absence of nickel and to obtain sufficient performance as a brake disc, the steel of the base layer 30 has a molybdenum content of 0.5% to 10%, more preferably 0.5% to 4.5%, and a manganese content of 0.5% to 5%, including extreme amounts. The presence of molybdenum and manganese in the above proportions provides sufficient corrosion resistance and, at the same time, sufficient mechanical resistance.

[0051] According to the embodiment, an intermediate layer 300 made of nickel steel is interposed between the base layer 30 and at least one of the two brake surfaces 2a and 2b of the brake band 2, preferably having a nickel content higher than 5% when the base layer 30 contains no nickel, more preferably having a nickel content of at least 5%, and even more preferably having a nickel content of at least 5% or more and less than 15%.

[0052] According to one embodiment, the intermediate layer 300 is made of steel having a nickel content of at most 15% or equal to 15%.

[0053] According to one embodiment, the intermediate layer 300 is made of steel having a nickel content of at most 7.5% or equal to 7.5%.

[0054] In a further embodiment, a nickel-free steel intermediate layer 300 is interposed between the base layer 30 and at least one of the two brake surfaces 2a, 2b of the brake band.

[0055] According to one embodiment, the intermediate layer 300 is made of nickel-free steel consisting of 10% to 15% chromium (Cr), at most 1% silicon (Si), at most 4% manganese (Mn), 0.16% to 0.5% carbon (C), and the remainder being iron (Fe). Preferably, the carbon (C) content is 0.16% to 0.25%.

[0056] The presence of the intermediate layer 300 allows for the creation of a disk with appropriate mechanical properties, while the presence of the base layer 30 simultaneously reduces the environmental impact.

[0057] According to one embodiment, the intermediate layer 300 is made of steel consisting of 10% to 15% chromium (Cr), at most 1% silicon (Si), at most 4% manganese (Mn), 0.16% to 0.5% carbon (C), and the remainder being iron (Fe). Preferably, the carbon (C) content of the steel in the intermediate layer 300 is 0.16% to 0.25%.

[0058] According to the embodiment, the surface protective coating 3 is made of steel consisting of 10% to 15% chromium (Cr), at most 1% silicon (Si), at most 4% manganese (Mn), 0.16% to 0.5% carbon (C), and the remainder being iron (Fe), and preferably does not contain nickel.

[0059] Preferably, the carbon (C) content of the steel in the surface protective coating is 0.16% to 0.25%, and may include extreme values.

[0060] According to the embodiment, an auxiliary ferrite-soft nitriding layer or auxiliary ferroaluminate layer is interposed between one of the two brake surfaces 2a, 2b of the brake band and the base layer 30, or between one of the two brake surfaces 2a, 2b of the brake band and the intermediate layer 300, or between the base layer 30 and the surface protective coating 3, or between the intermediate layer 300 and the base layer 30.

[0061] According to the embodiment, an auxiliary ferrite-soft nitriding layer and an auxiliary ferroaluminate layer are interposed between one of the two brake surfaces 2a, 2b of the brake band and the base layer 30, or between one of the two brake surfaces 2a, 2b of the brake band and the intermediate layer 300, or between the base layer 30 and the surface protective coating 3, or between the intermediate layer 300 and the base layer 30.

[0062] To simplify the discussion, the brake disc 1 will be described in relation to the method according to the present invention. The brake disc 1 is preferably manufactured by the method according to the present invention, which will be described below, but it is not necessarily required to be so.

[0063] According to a first aspect of the present invention, a general embodiment of the method according to the present invention has the following operating steps. a) A step of preparing a brake disc comprising a brake band and having two opposing brake surfaces 2a, 2b, wherein each brake surface 2a, 2b defines at least a portion of two main surfaces of the disc, the brake band being made of gray cast iron or steel. b) A steel layer containing up to 15% nickel is deposited, preferably by laser deposition, such as laser metal deposition, hyperfast laser material deposition, thermal spray deposition, or cold spray deposition, to form a base layer 30. c) Optionally, a step of depositing particulate material made of tungsten carbide (WC), niobium carbide (NbC), titanium carbide (TiC), or optionally chromium carbide onto a base layer 30 by thermal spraying technology [e.g., HVOF (high-speed oxygen fuel) technology, HVAF (high-speed air fuel) technology, APS (atmospheric pulse spray) technology], cold spray deposition technology [e.g., KM (kinetic metallization) technology], laser beam deposition technology [e.g., LMD (laser metal deposition) technology, HSLC (high-speed laser cladding) technology, EHLA (extremely high-speed laser application) technology, TSC (top-speed cladding) technology] to cover at least one of the two brake surfaces of the brake band, for example, covering the base layer 30, preferably covering the entire surface of at least one of the two brake surfaces 2a, 2b of the brake band, to form a protective surface coating 3.

[0064] According to a second aspect of the present invention, a more general embodiment of the method according to the present invention comprises the following operational steps: a) A step of preparing a brake disc comprising a brake band and having two opposing brake surfaces 2a, 2b, wherein each brake surface 2a, 2b defines at least a portion of one of the two main surfaces of the disc, and the brake band is made of gray cast iron or steel. b) A nickel-free steel layer is deposited, preferably by laser deposition technology, such as laser metal deposition, hyperfast laser material deposition, thermal spray deposition, or cold spray deposition, to form the base layer 30; c) Optionally, deposit particulate material consisting of tungsten carbide (WC), niobium carbide (NbC), titanium carbide (TiC), or possibly chromium carbide onto the base layer 30 by thermal spraying technology [e.g., HVOF (high-speed oxygen fuel) technology, HVAF (high-speed air fuel) technology, APS (atmospheric pulse spray) technology], cold spray deposition technology [e.g., KM (kinetic metallization) technology], laser beam deposition technology [e.g., LMD (laser metal deposition) technology, HSLC (high-speed laser cladding) technology, EHLA (extremely high-speed laser application) technology, TSC (top-speed cladding) technology] to form a protective surface coating 3 that covers at least one of the two brake surfaces of the brake band, for example, the base layer 30, preferably covering the entire surface of at least one of the two brake surfaces 2a, 2b of the brake band.

[0065] According to a third aspect of the present invention, a more general embodiment of the method according to the present invention comprises the following operational steps: a) A step of preparing a brake disc comprising a brake band and having two opposing brake surfaces 2a, 2b, wherein each brake surface 2a, 2b defines at least a portion of one of the two main surfaces of the disc, and the brake band is made of gray cast iron or steel. a1) After step a1), deposit an intermediate layer 300 made of nickel-free steel onto at least one of the two opposing brake surfaces 2a and 2b. b) After step a1), a nickel-free steel layer is deposited, preferably by laser deposition, such as laser metal deposition, hyperfast laser material deposition, thermal spray deposition, or cold spray deposition, to form a base layer 30. c) Optionally, deposit particulate material consisting of tungsten carbide (WC), niobium carbide (NbC), titanium carbide (TiC), or possibly chromium carbide onto the base layer 30 by thermal spraying technology [e.g., HVOF (high-speed oxygen fuel) technology, HVAF (high-speed air fuel) technology, APS (atmospheric pulse spray) technology], cold spray deposition technology [e.g., KM (kinetic metallization) technology], laser beam deposition technology [e.g., LMD (laser metal deposition) technology, HSLC (high-speed laser cladding) technology, EHLA (extremely high-speed laser application) technology, TSC (top-speed cladding) technology] to form a protective surface coating 3 that covers at least one of the two brake surfaces of the brake band, for example, the base layer 30, preferably covering the entire surface of at least one of the two brake surfaces 2a, 2b of the brake band.

[0066] According to one embodiment, step a1) provides depositing an intermediate layer 300 consisting of nickel-free steel, 10% to 15% chromium (Cr), at most 1% silicon (Si), at most 4% manganese (Mn), 0.16% to 0.5% carbon (C), preferably 0.16% to 0.25% carbon (C), including extreme amounts, and the remainder being iron (Fe).

[0067] According to a further aspect of the present invention, a more general embodiment of the method according to the present invention comprises the following operational steps: a) A step of preparing a brake disc 1, which includes a brake band 2 having two opposing brake surfaces 2a, 2b, each brake band defining at least a portion of the two main surfaces of the disc, and the brake band being made of gray cast iron or steel. b) A step of depositing a base layer 30 made of steel that does not contain any nickel, and consists of 10% to 15% chromium (Cr), at most 1% silicon (Si), at most 4% manganese (Mn), 0.16% to 0.5%, preferably 0.16% to 0.25%, of which iron (Fe) is the remainder.

[0068] According to a further aspect of the present invention, a general embodiment of the method according to the present invention has the following operational steps: a) A step of preparing a brake disc comprising a brake band and having two opposing brake surfaces 2a, 2b, wherein each brake surface defines at least a portion of the two main surfaces of the disc, and the brake band is made of gray cast iron or steel. a1) Following step a1), an intermediate layer 300 made of nickel-containing steel is deposited on at least one of the two opposing brake surfaces 2a, 2b, preferably in accordance with the features described in the previous paragraph of this paper. b) After step a1), a nickel-free steel layer is deposited, preferably by laser deposition technology, such as laser metal deposition or ultrafast laser material deposition, or thermal spray deposition technology, or cold spray deposition technology, to form a base layer 30. c) Optionally, deposit particulate material consisting of tungsten carbide (WC), niobium carbide (NbC), titanium carbide (TiC), or possibly chromium carbide onto the base layer 30 by thermal spraying technology [e.g., HVOF (high-speed oxygen fuel) technology, HVAF (high-speed air fuel) technology, APS (atmospheric pulse spray) technology], cold spray deposition technology [e.g., KM (kinetic metallization) technology], laser beam deposition technology [e.g., LMD (laser metal deposition) technology, HSLC (high-speed laser cladding) technology, EHLA (extremely high-speed laser application) technology, TSC (top-speed cladding) technology] to form a protective surface coating 3 that covers at least one of the two brake surfaces of the brake band, for example, the base layer 30, preferably covering the entire surface of at least one of the two brake surfaces 2a, 2b of the brake band.

[0069] In addition to the modifications of the general embodiments of the method according to the present invention described above, the method preferably provides further steps described below.

[0070] Preferably, in step c), tungsten carbide (WC), niobium carbide (NbC), titanium carbide (TiC), or optionally chromium carbide is dispersed in the metal matrix.

[0071] According to a preferred embodiment, in step c), the particulate material is composed of chromium carbide and titanium carbide.

[0072] Advantageously, the brake disc is positioned with a portion suitable for securing the disc to the vehicle, having an annular portion 4 located at the center of the disc 1 and concentric with the brake band 2. The securing portion 4 supports a connecting element 5 to the wheel hub (i.e., the bell). The bell may be manufactured integrally with the annular securing portion (as shown in the accompanying diagram) or may be manufactured separately and thus secured to the securing portion via a suitable connecting element.

[0073] The annular fixing portion 4 can be made of the same material as the brake band, i.e., gray cast iron, or other suitable material. The bell 5 can also be made of gray cast iron or other suitable material. In particular, the entire disc (i.e., the brake band, fixing portion and bell) can be made of gray cast iron.

[0074] Preferably, the brake band 2 is made by casting. Similarly, if it is made of gray cast iron, the fixing part and / or bell may also be made of casting.

[0075] The annular fixing portion may be manufactured integrally with the brake band (as shown in the attached diagram), or it may be manufactured as a separate component mechanically connected to the brake band.

[0076] With regard to HVOF, HVAF, or KM, or LMD or HSLC technologies, these are three film deposition techniques known to those skilled in the art, so a detailed explanation will be omitted.

[0077] High-Velocity Oxygen Fuel (HVOF) is a powder spray deposition technology that uses a spraying device equipped with a mixed combustion chamber and spray nozzles. Oxygen and fuel are supplied to the chamber. The high-temperature combustion gas, formed at a pressure close to 1 MPa, passes through converging and branching nozzles into the powder material, which reaches hypersonic speeds (higher than MACH1). The powder material to be deposited is injected into the high-temperature gas stream, where it rapidly melts and is accelerated to speeds on the order of 1000 m / s. Upon impact with the deposition surface, the molten material cools rapidly and, due to the high kinetic energy of the impact, forms an extremely dense and compact structure.

[0078] High-speed air-fuel (HVAF) deposition technology is similar to high-velocity oxygen-fuel (HVOF) technology. The difference is that in HVAF technology, air is supplied to the combustion chamber instead of oxygen. Therefore, the temperature is lower than with HVOF. This allows for better control over the thermal degradation of the coating.

[0079] KM (Kinetic Metallization) deposition is a solid deposition process that sprays metal powder through a two-phase ultrasonic deposition nozzle, accelerating and triboelectrically charging metal particles in an inert gas flow. Thermal energy is supplied to the transport flow. This process converts the potential energy of the compressed inert gas flow and the supplied thermal energy into the kinetic energy of the powder. When accelerated to high speed and charged, the particles are directed towards the deposition surface. The high-speed collision of the metal particles with this surface causes significant deformation of the particles (approximately 80% in the direction perpendicular to the collision). This deformation greatly increases the surface area of ​​the particles. Therefore, upon impact, close contact occurs between the particles and the deposition surface, forming metallic bonds and creating a coating with a very dense and compact structure.

[0080] Advantageously, as an alternative to the three deposition techniques mentioned above, which share the fact that they are high-kinetic-energy impact deposition techniques, other techniques can also be used that utilize different deposition methods but can produce coatings with a very dense and compact structure.

[0081] The combination of HVOF, HVAF, KM, LMD, or HSLC deposition techniques and the chemical components used to form the base layer 30 and surface protective coating 3 makes it possible to obtain both high bonding strength on the underlying material to which they are deposited and deposition of powders with a high carbide content.

[0082] As already mentioned above, the base layer 30 and the surface protective coating 3 cover at least one of the two braking surfaces of the brake band.

[0083] In the following, the term "coating" refers to both the set provided by the base layer 30 and the surface protective coating 3, and the base layer 30 alone in a modified example where the surface protective coating 3 is not specified but the base layer 3 is specified to contain carbides.

[0084] Preferably, as shown in Figures 2 and 3, the disc 1 is provided with coatings 3, 30 that cover both the brake surfaces 2a, 2b of the brake band 2.

[0085] In particular, coatings 3 and 30 may cover only the brake band, a single brake surface, or both.

[0086] In embodiments not shown in the accompanying figures, the coatings 3, 30 may also extend to other parts of the disc 1, such as the annular fixing portion 4 and the bell 5, thereby coating the entire surface of the disc 1. In particular, the coatings 3, 30 may cover only the fixing portion or only the bell, in addition to the brake band. The choice is determined primarily for aesthetic reasons in order to achieve uniform coloring and / or finish across the entire disc or a portion thereof.

[0087] Advantageously, the deposition of particulate matter for forming coatings 3 and 30 can be carried out on the surface of the disk in a differentiated manner, at least in terms of the thickness of the coating.

[0088] In the brake band region, coatings 3 and 30 can be of the same thickness on the two opposing brake surfaces. Alternatively, a solution can be provided in which coatings 3 and 30 have different thicknesses between the two brake surfaces of the brake band.

[0089] According to one embodiment of the present method, step b) for depositing the base layer 30 provides depositing a particulate composition of steel having at least 15%, at least 7.5%, or at least 5% nickel content, or steel that does not contain any nickel at all, by laser deposition technology, preferably LMD (Laser Metal Deposition) or EHLA (Extremely Fast Laser Material Deposition), or thermal spray deposition technology, or cold spray deposition technology.

[0090] In an advantageous embodiment, in step b), the particulate composition further comprises carbides mixed in a proportion not exceeding 50% by weight of the total particulate composition.

[0091] In an advantageous embodiment, in step b), the particulate composition also includes, in addition to steel, a metal oxide or a mixture of a metal and a ceramic material, preferably a mixture of aluminum oxide Al2O3, or a mixture of Al2O3 and an intermetallic matrix Fe-Cr, such as Fe28Cr.

[0092] According to the embodiment, in step b), the particle-form composition includes, in addition to steel, a metal oxide or a mixture of metal and ceramic material, preferably a mixture of aluminum oxide Al2O3, or a mixture of Al2O3 and the intermetallic matrix Fe-Cr, for example Fe28Cr, and further one or more carbides selected from the group consisting of tungsten carbide (WC), niobium carbide (NbC), titanium carbide (TiC), and chromium carbide.

[0093] Therefore, it is clear that by modifying the method described above, the base layer 30 is made of the aforementioned mixture of steel and metal oxide, and in another modification, a brake band 2 is made of a mixture of steel, metal oxide and the aforementioned carbide.

[0094] Preferred embodiments and variations of the brake band, as well as the arrangement order of the base layer 30, intermediate layer 300, and surface coating layer 3, can be better understood by referring to the attached diagram.

[0095] Preferably, step a1) for depositing the intermediate layer 300 provides depositing a particulate composition made of steel having a nickel content of 5% to 15% by laser deposition technology, preferably LMD (laser metal deposition) or EHLA (ultrafast laser material deposition), or thermal spray deposition technology, or cold spray deposition technology.

[0096] According to a modified example of an advantageous embodiment of the present method, step e1) is provided in which a ferrite-soft nitriding auxiliary layer is deposited between one of the two brake surfaces 2a, 2b of the brake band and the base layer 30, and / or between one of the two brake surfaces 2a, 2b of the brake band and the intermediate layer 300, and / or between the base layer 30 and the protective surface coating 3, and / or between the intermediate layer 300 and the base layer 30.

[0097] According to an advantageous embodiment, the method includes step e2) depositing an auxiliary ferroalumination layer between one of the two brake surfaces 2a, 2b of the brake band and the base layer 30, and / or between one of the two brake surfaces 2a, 2b of the brake band and the intermediate layer 300, and / or between the base layer 30 and the protective surface coating 3, and / or between the intermediate layer 300 and the base layer 30.

[0098] Preferably, the ferroalumination step e2) includes the following steps: e21) A step of at least partially immersing the brake band 2 in molten aluminum maintained at a predetermined temperature such that the molten aluminum covers at least a predetermined surface area of ​​the brake band 2, wherein the immersion is extended for a predetermined time to allow the diffusion of aluminum atoms into the surface microstructure of the cast iron or steel and the resulting formation of a ferroaluminum intermetallic compound in the surface layer of the brake band 2, thereby generating a layer of the ferroaluminum intermetallic compound in the predetermined surface area of ​​the brake band 2. e22) The step of removing the brake band 2 from the molten aluminum. e23) The step of removing the aluminum remaining on the brake band 2 to expose the layer of the ferroaluminum intermetallic compound on the surface.

[0099] The layer of ferroaluminum intermetallic compound exposed on the surface imparts excellent corrosion resistance and wear resistance to the brake band 2, which is made of cast iron or steel, in the predetermined surface area.

[0100] Preferably, the ferroaluminum intermetallic compound layer consists of FeAl3 as the dominant phase of the ferroaluminum intermetallic compound.

[0101] According to an advantageous embodiment, the predetermined temperature at which the molten aluminum is maintained is not higher than 750°C, preferably between 690°C and 710°C, and more preferably equal to 700°C.

[0102] According to an advantageous embodiment of the present method, the predetermined immersion time is determined according to the thickness to be obtained for the intermetallic compound layer, and when the temperature of the molten aluminum is the same, the thickness increases as the immersion time increases, preferably the predetermined immersion time is between 5 and 60 minutes, and more preferably equal to 30 minutes.

[0103] In a favorable embodiment, prior to the immersion step e21), the method includes step f) decarburizing the predetermined surface area of ​​the brake band 2 to a predetermined depth.

[0104] Experimentally verified that the presence of carbon in the surface layer of a brake band, subject to penetration by aluminum atom diffusion (induced by aluminization), leads to the formation of iron carbide, as well as intermetallic compounds. The presence of iron carbide creates discontinuities in the intermetallic compound layer, which can induce both corrosion and cracking. Advantageously, surface decarburization treatment can avoid (or at least significantly reduce) the formation of iron carbide, leading to the formation of an intermetallic compound layer that is more resistant to corrosion and less susceptible to cracking.

[0105] Preferably, in step f), the decarburization of the at least one predetermined surface region is carried out by an electrolytic process.

[0106] More specifically, the electrolytic process is carried out by immersing a predetermined surface area of ​​the brake band in a bath of molten salt and applying a potential difference between the bath and the brake band.

[0107] When a potential difference is applied, the brake band is connected to the positive electrode (cathode), while the molten salt bath is connected to the negative electrode (anode). Carbon, especially carbon in the form of graphite flakes, is oxidized to carbon dioxide by the release of electrons and atomic oxygen at the anode. Carbon mainly reacts with oxygen and ultimately combines to form carbon dioxide.

[0108] The oxidation of the brake band surface induced by the electrolytic process is not limited to the carbon present, but also extends to the cast iron (iron) metal matrix, causing the formation of a metal oxide surface film. Reversing the polarity reduces the metal oxide surface film, returning the band to its original metallic state.

[0109] Preferably, the aforementioned electrolytic process can therefore provide a reversal of polarity so that the metal oxide film returns to its original metallic state after a predetermined period of time during which the surface of the brake band is connected to the cathode to oxidize carbon.

[0110] Operationally, the decarburization depth is controlled by adjusting the time of the electrolytic process, which may also be divided into different polarity reversal cycles. Increasing the time of the decarburization process (the oxidation stage of the brake band; connection to the cathode) increases the decarburization depth, even if all other conditions are the same.

[0111] Decarburization can be carried out by alternative processes to the electrolytic process described above, such as laser treatment or chemical treatment.

[0112] However, decarburization by electrolytic treatment is preferred. The reasons are as follows: - Compared to laser processing, it is far more efficient and faster, ensuring more complete and uniform carbon removal in a shorter time. - Compared to chemical treatments (e.g., treatment with potassium permanganate), it is more efficient (ensuring more complete and uniform carbon removal in a shorter time) and does not leave oxidized regions of the cast iron metal matrix in the treated area.

[0113] More specifically, it has been observed that in the oxidized regions of the cast iron matrix, the wettability of molten aluminum is very low, which adversely affects the aluminization process and the characteristics of the intermetallic compound layer. For this reason, the electrolytic decarburization process is preferred over the alternative processes described above.

[0114] As already noted, the thickness of the intermetallic compound layer is mainly influenced by the temperature of the molten aluminum and the immersion time in the molten aluminum. However, it has been found that another factor influencing the thickness of the intermetallic compound layer is the silicon content in the molten aluminum. The higher the weight content of silicon in the molten aluminum, the thinner the intermetallic compound layer will be under the same conditions. Preferably, the molten aluminum has a silicon content of less than 1% by weight.

[0115] Preferably, the molten aluminum has an impurity content of 1% by weight or less. In particular, aluminum with a maximum purity of 99.7% by weight and containing the following impurities (by weight): Si ≤ 0.30%; Fe ≤ 0.18%; Sr ≤ 0.0010%; Na ≤ 0.0025%; Li ≤ 0.0005%; Ca ≤ 0.0020%; P ≤ 0.0020%; Sn ≤ 0.020%.

[0116] In some cases, even after decarburizing a brake band and removing graphite flakes from the surface layer where a layer of intermetallic compounds should form, the resulting layer of intermetallic compounds still contains graphite flakes, as if they had not been removed. This phenomenon can be explained by the fact that the dissolution of iron in aluminum is so rapid that the decarburized layer is consumed rapidly, and as a result, the metallic compounds form in the layer below the decarburized layer, i.e., where the graphite flakes were.

[0117] In other words, the excessive solubility of iron in molten aluminum can completely or partially negate the beneficial effect of surface decarburization on the braking surface.

[0118] Advantageously, step b1) can be performed, which involves immersing the aluminum in a bath of molten aluminum containing dissolved iron in order to slow down the dissolution of iron into the aluminum bath. In this way, by suppressing the dissolution of iron into aluminum, the formation of FeAl3 can be kinetically promoted, and intermetallic compounds can be formed in the decarburized layer.

[0119] Preferably, the iron content in the solution in the aluminum bath is 5% by weight or less, more preferably 3% to 5% by weight, and most preferably equal to 4% by weight, ensuring a significant effect in slowing down the iron dissolution process of cast iron in aluminum.

[0120] For example, an aluminum bath having the following composition (weight %) can be used: Al ≤ 97%; Fe 3-5%; containing the following impurities: Si ≤ 0.30%; Fe ≤ 0.18%; Sr ≤ 0.0010%; Na ≤ 0.0025%; Li ≤ 0.0005%; Ca ≤ 0.0020%; P ≤ 0.0020%; Sn ≤ 0.020%.

[0121] Experimental studies have shown that aluminization using a molten aluminum bath containing iron yields a greater amount of porous intermetallic compound layers, especially when the iron content is close to the solubility limit. This can be explained by the increased viscosity of the molten aluminum bath containing iron, which in turn reduces its wettability to cast iron.

[0122] Advantageously, the immersion step b1) described above is carried out in two substeps so that the intermetallic compound layer is compact and uniform, and therefore not very porous, and at the same time, so that this layer does not develop beneath the decarburized layer and incorporate the graphite flakes present therein. - First substep b11) immersion in a first bath of molten aluminum that is substantially free of iron (or contains at least iron as an impurity; for example, with an iron content lower than 0.20 wt%). - A second substep b12) involves immersing the initial layer in a second bath of molten aluminum containing iron in solution until a final layer of a ferroaluminum intermetallic compound having a predetermined thickness is obtained on the predetermined surface region.

[0123] The immersion time of the brake band in the first bath is shorter than the immersion time of the brake band in the second bath.

[0124] Preferably, the immersion of the brake band in the first bath is for as short a time as possible, but is continued for a sufficient time to obtain an initial layer of ferroaluminum intermetallic compound having a thickness not exceeding 10 μm on the predetermined surface area. In particular, the immersion time in the first bath is 3 to 5 minutes when the temperature of the first bath is about 700°C. As the temperature of the bath rises, the immersion time must decrease.

[0125] More specifically, if the temperature of the second bath is the same, the thickness increases as the immersion time increases, and if the immersion time is the same, the thickness increases as the temperature of the second bath increases.

[0126] Advantageously, both the first and second baths of molten aluminum have an impurity content not higher than 1% by weight. In particular, the two molten aluminum baths have a silicon content lower than 1% by weight.

[0127] Preferably, the iron content in the solution in the second aluminum bath is 5% by weight or less (the solubility limit of iron in aluminum at 700°C is 4% by weight; aluminum saturated with iron), more preferably between 3% and 5% by weight, and most preferably equal to 4% by weight. The iron content should not be less than 3% in order to ensure a significant slowing effect on the iron melting process of cast iron in aluminum.

[0128] Advantageously, both the first bath and the second bath are maintained at a temperature lower than 680°C, preferably not higher than 750°C, more preferably between 690°C and 710°C, and even more preferably equal to 700°C.

[0129] Advantageously, the method may include a step of surface pretreatment of the brake band performed prior to the immersion step e21) in at least the predefined surface area. Preferably, the surface pretreatment step consists of lapping, degreasing, sandblasting and / or chemical removal of surface oxides.

[0130] Preferably, the method includes a step of removing the surface oxide layer from the molten aluminum bath prior to the immersion step e21). This step of removing the surface oxide is performed both when immersion in a single bath is intended and when immersion in two consecutive steps in a first bath and a second bath is intended.

[0131] According to a preferred embodiment of the present invention, the step of removing aluminum remaining attached to the brake band after extraction is carried out in two substeps.

[0132] A first removal substep is performed on the brake band immediately after it has been extracted from the molten aluminum, in which any molten aluminum remaining attached to the brake band is removed.

[0133] A second removal substep is performed on the brake band, which has been extracted from the molten aluminum and cooled, in order to remove any solidified residual aluminum remaining after the first removal substep.

[0134] Preferably, the method includes a step of rapidly cooling the brake band, which is performed between the first removal substep and the second removal substep.

[0135] Advantageously, the first removal substep can be carried out by mechanical shaving of the aluminum, which is still in liquid form.

[0136] Advantageously, the second removal substep can be carried out by chemical removal of solidified aluminum that was not mechanically removed.

[0137] Preferably, the chemical removal is carried out by exposing the aluminum to ferric chloride for at least 4 minutes to induce the following reaction: Al + FeCl3 -> AlCl3 + Fe

[0138] The chemical removal with ferric chloride should necessarily be carried out after the solidification of the aluminum. Since ferric chloride boils at 315°C, it must not come into contact with the molten aluminum. Preferably, the chemical removal is carried out after the quenching step.

[0139] The aforementioned steps of a method called ferroalumination can be used to obtain brake bands, and therefore brake discs, with improved wear resistance and corrosion resistance.

[0140] It should be noted that the ferroaluminum intermetallic compound layer can be composed of multiple intermetallic compounds between iron and aluminum, particularly Fe3Al, FeAl, FeAl2, FeAl3, and Fe2Al5. The dominant intermetallic compound phase is the thermodynamically stable FeAl3.

[0141] According to one embodiment, the method provides depositing an auxiliary ferrite-soft nitride layer and an auxiliary ferroaluminate layer between one of the two brake surfaces 2a, 2b of the brake band and the base layer 30, and / or between one of the two brake surfaces 2a, 2b of the brake band and the intermediate layer 300, and / or between the base layer 30 and the protective surface coating 3, and / or between the intermediate layer 300 and the base layer 30.

[0142] As can be understood from the above description, the brake disc according to the present invention makes it possible to overcome the shortcomings of the prior art.

[0143] By combining a steel base layer with reduced or no nickel content with a cast iron band, the brake disc 1 according to the present invention substantially prevents the generation and release of nickel particles during operation.

[0144] Furthermore, according to particularly advantageous modifications, the addition of a protective surface coating 3 containing or coated with carbides improves wear resistance, compensates for the nickel deficiency in the base layer steel, and provides sufficient mechanical strength.

[0145] Particularly advantageous is the ability to produce nickel-free martensitic steel that exhibits less brittleness during high-temperature use and simultaneously possesses a sufficient corrosion-resistant coating by using a base layer 30 consisting of steel that is completely nickel-free and 10% to 15% chromium (Cr), at most 1% silicon (Si), at most 4% manganese (Mn), 0.16% to 0.5% carbon (C), preferably 0.16% to 0.25% carbon (C), and the remainder iron (Fe). These advantages are synergistically combined with the possibility of using a reduced proportion of carbides in the steel, resulting in a reduction of the resources required for production while maintaining appropriate hardness of the coating.

[0146] Advantageously, the base layer 30, preferably nickel-free, also performs a mechanical "cushioning" function (wear prevention) of the protective surface coating 3. In fact, the base layer 30 exhibits elastic behavior that at least partially dampens the stress applied to the disc during use. Thus, the base layer 30 functions as a kind of shock absorber or cushion between the disc and the protective surface coating 3. In this way, direct transmission of stress between the two parts is avoided, and as a result, the risk of cracking in the protective surface coating 3 is also reduced.

Claims

1. A brake disc (1) for a disc brake, comprising a brake band (2) having two opposing brake surfaces (2a, 2b), wherein each of the two brake surfaces (2a, 2b) defines at least a portion of two main surfaces of the brake disc (1), and the brake band (2) is made of gray cast iron or steel, The brake disc comprises a base layer (30) that covers at least one of the two brake surfaces (2a, 2b) of the brake band. The base layer (30) is composed of steel that does not contain any nickel, and one or more carbides contained in the nickel-free steel. A brake disc (1) for a disc brake, wherein an intermediate layer (300) made of nickel-free steel is interposed between the base layer (30) and at least one of the two brake surfaces (2a, 2b) of the brake band (2).

2. The brake disc (1) for a disc brake according to claim 1, wherein the base layer (30) comprises at least one carbide selected from the group consisting of tungsten carbide (WC), chromium carbide, niobium carbide (NbC), and titanium carbide (TiC).

3. At least one side of the two brake surfaces (2a, 2b) of the brake band includes a protective surface coating (3) covering the base layer (30), The protective surface coating (3) is positioned on the side of the base layer (30) that does not face one of the two brake surfaces (2a, 2b). The brake disc (1) for a disc brake according to claim 1 or 2, wherein the protective surface coating (3) is composed of one or more particulate carbides deposited by thermal spraying technology [e.g., HVOF (high-speed oxygen fuel) technology, HVAF (high-speed air fuel) technology, APS (atmospheric pulse spray) technology], cold spray deposition technology [e.g., KM (kinetic metallization) technology], or laser beam deposition technology [e.g., LMD (laser metal deposition) technology, HSLC (high-speed laser cladding) technology, EHLA (extremely high-speed laser application) technology, or TSC (top-speed cladding) technology].

4. The brake disc (1) for a disc brake according to claim 3, wherein the particulate carbide of one or more parts comprises tungsten carbide (WC), chromium carbide, niobium carbide (NbC), or titanium carbide (TiC).

5. The brake disc (1) for a disc brake according to claim 4, wherein the particulate one or more carbides consist of chromium carbide and titanium carbide.

6. The brake disc (1) for a disc brake according to any one of claims 1 to 5, wherein the steel of the base layer (30) contains at least 15% chromium (Cr).

7. The brake disc (1) for a disc brake according to any one of claims 1 to 6, wherein the steel of the base layer (30) contains 10% to 20% chromium (Cr), including the extreme values.

8. The brake disc (1) for a disc brake according to any one of claims 1 to 7, wherein the steel of the base layer (30) has a molybdenum content of 0.5% to 10% including the extreme value, and a manganese content of 0.5% to 7%.

9. The brake disc (1) for a disc brake according to any one of claims 1 to 8, wherein the steel of the base layer (30) is composed of 10% to 20% chromium (Cr), at most 1.5% silicon (Si), at most 2% manganese (Mn), at most 0.03% carbon (C), and the remainder being iron (Fe).

10. The brake disc (1) for a disc brake according to any one of claims 1 to 9, wherein the base layer (30) has a thickness between 20 μm and 300 μm, preferably 90 μm.

11. a) A step of preparing a brake disc (1), comprising a brake band (2) having two opposing brake surfaces (2a, 2b), wherein the brake band defines at least a portion of the two main surfaces of the brake disc, and the brake band is made of gray cast iron or steel. a1) After step a), deposit an intermediate layer (300) made of nickel-free steel on at least one of the two brake surfaces (2a, 2b), and b) A method for manufacturing a brake disc, comprising the operational step of depositing a base layer (30) made of nickel-free steel after step a1).

12. The method for manufacturing a brake disc according to claim 11, wherein step b) for depositing the base layer (30) comprises depositing a particulate composition made of nickel-free steel by laser deposition technology, preferably laser metal deposition or ultrafast laser material deposition, or thermal spray deposition technology, or cold spray deposition technology.

13. The method for manufacturing a brake disc according to claim 12, wherein in step b) of depositing the base layer (30), the particulate composition further comprises carbides mixed in a proportion not exceeding 50% by weight of the total particulate composition.

14. On the base layer (30), a particulate material consisting of tungsten carbide (WC), niobium carbide (NbC), titanium carbide (Tic), or chromium carbide is deposited by thermal spraying technology [e.g., HVOF (high-speed oxygen fuel) technology, HVAF (high-speed air fuel) technology, APS (atmospheric pulse spray) technology], cold spray deposition technology [e.g., KM (kinetic metallization) technology], laser beam deposition technology [e.g., LMD (laser metal deposition) technology, HSLC (high-speed laser cladding) technology, EHLA (extremely high-speed laser application) technology, TSC (top-speed cladding) technology] to form a protective surface coating (3) on the base layer (30), preferably covering the entire surface of at least one of the two brake surfaces (2a, 2b) of the brake band. A method for manufacturing a brake disc according to any one of claims 11, 12, or 13, further comprising step c).

15. Step e1) deposits a ferrite-nitrided carburized auxiliary layer between one of the two brake surfaces (2a, 2b) of the brake band and the base layer (30), and / or between one of the two brake surfaces (2a, 2b) of the brake band and the intermediate layer (300), and / or between the base layer (30) and the protective surface coating (3), and / or between the intermediate layer (300) and the base layer (30). Step e2) includes depositing an auxiliary ferroalumination layer between one of the two brake surfaces (2a, 2b) of the brake band and the base layer (30), and / or between one of the two brake surfaces (2a, 2b) of the brake band and the intermediate layer (300), and / or between the base layer (30) and the protective surface coating (3), and / or between the intermediate layer (300) and the base layer (30), The aforementioned step e2) is, e21) A step of at least partially immersing the brake band (2) in molten aluminum maintained at a predetermined temperature such that the molten aluminum covers at least a predetermined surface area of ​​the brake band (2), the step of extending the immersion for a predetermined time to diffuse aluminum atoms into the surface microstructure of the cast iron or steel, thereby forming a ferroaluminum intermetallic compound in the surface layer of the brake band (2), thereby generating a layer of the ferroaluminum intermetallic compound in the predetermined surface area of ​​the brake band, e22) The step of removing the brake band from the molten aluminum, e23) A method for manufacturing a brake disc according to claim 14, comprising the step of removing aluminum remaining on the brake band after extraction such that a layer of the ferroaluminum intermetallic compound is exposed on the surface of the brake band, wherein the exposed layer of the ferroaluminum intermetallic compound imparts excellent corrosion resistance and wear resistance to the cast iron or steel brake band in the predetermined surface region.

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