Brake disc for disc brake and method for producing such disc brake

Abstract

The invention relates to a brake disc for a disc brake, in particular for a motorcycle or a motor vehicle, comprising a brake band (2) provided with two opposite brake surfaces (2a, 2b), each of which at least partially defines one of two main face parts of the disc (1), the brake band (2) is made of gray cast iron or steel, preferably stainless steel, said disc comprising a surface coating (3) covering at least one of the two brake surfaces of the brake band. Said surface coating (3) is based on a mixture of one or more aluminum oxides and one or more titanium oxides, said surface coating (3) having a color darker than the color of the steel or gray cast iron of the brake band (2).

Description

Technical Field

[0001] The invention relates to a brake disc for a disc brake and to a method for producing such a brake disc. Background Art

[0002] A brake disc for a disc brake system for a vehicle or motorcycle comprises an annular structure or brake band. Typically, the brake disc is provided with a central fixing element, called a bell, by means of which the disc is fixed to a rotating part of the suspension of the vehicle or motorcycle, such as a wheel hub. It is possible to provide a brake disc solution in which the brake band is fixed directly to the rotating part of the rotation, such as a wheel hub or a wheel rim, without the interposition of a bell. The brake band is provided with opposing braking surfaces suitable for cooperating with friction elements (brake pads), which are housed in at least one caliper body, which is arranged to straddle such a brake band and is integral with a non-rotating part of the vehicle suspension. The controlled interaction between the opposing brake pads and the opposing braking surfaces of the brake band produces a braking action by friction, thereby allowing the vehicle to be slowed down or stopped.

[0003] In many cases, in particular in motorcycles and in motor vehicles provided with rims having large windows or large diameters, the brake disc is clearly visible from the outside of the vehicle and is thus of increasing aesthetic value to the user.

[0004] Typically, the most common brake discs are made of grey cast iron or steel, and in particular of stainless steel. In fact, these materials allow good braking performance (especially in terms of limiting wear) to be obtained at relatively low cost. Discs made solely of carbon or of carbon-ceramic materials offer higher performance, but at a much higher cost.

[0005] Recently, the market has seen a growing demand for aesthetically pleasing brake discs of grey cast iron or steel to meet the needs of an increasingly wide range of users.

[0006] An increasingly common requirement among users, especially of motorcycles, is to install brake discs made of grey cast iron or steel, especially stainless steel, wherein the brake band has a black or blackish color or a color darker than the color of the starting substrate.

[0007] Disc manufacturers have attempted to meet this demand by coating the brake band with a black or black-colored coating.

[0008] However, no coating has been found so far which allows obtaining a black or blackish color or a color darker than the color of the starting base material of the brake band while being resistant to high temperatures, wear, abrasion and corrosion.

[0009] In other words, to date, no coating has been found that can be applied to a brake band of a brake disc made of grey cast iron or stainless steel that will impart a black or blackish colour or a darker colour than the starting substrate and that will withstand normal operating conditions on the disc over time.

[0010] The most suitable brake discs with a black or blackish color or a color darker than the color of the starting substrate to ensure color and performance stability are discs made of carbon only or of carbon ceramic material. However, such discs have a much higher cost compared to gray cast iron discs or steel discs.

[0011] In the field of brake discs, in particular for motorcycles, there is a strongly felt need to produce brake discs having a brake band made of grey cast iron or steel, in particular stainless steel, which is provided with a coating having a black or blackish colour or a darker colour than the colour of the starting substrate and which can withstand the normal operating conditions to which the disc is subjected over time. Summary of the invention

[0012] The object of the present invention is to provide a brake disc for a disc brake, in particular for a disc brake for a motor vehicle or motorcycle, which brake disc is made of grey cast iron or steel and has a brake band which has a black or blackish colour or a darker colour than the colour of the starting base material and which can withstand the normal operating conditions to which the brake disc is subjected over time.

[0013] These disadvantages are solved by a brake disk made of grey cast iron or steel according to claim 1 and a method for producing such a brake disk according to claim 17 .

[0014] Further embodiments of the disc brake and the manufacturing method according to the invention are described in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Further features and advantages of the invention will be better understood from the following description of preferred embodiments of the invention given by way of non-limiting examples, in which:

[0016] - Figure 1a shows a top plan view of a disc brake according to an embodiment of the present invention;

[0017] - Figure 1b shows a cross-sectional view of the brake disc in FIG. 1 taken along the cross-sectional plane AA shown in FIG. 1 ;

[0018] - Figure 2a Some parts are not shown to scale for the sake of illustration. Figure 1b ;

[0019] - Figure 2b The present invention is shown in a manner where some parts are not shown to scale for the purpose of illustration. Figure 2a In terms of alternative embodiments of the embodiments shown in Figure 1b ;

[0020] - Figure 3a A picture showing a brake disc having a black or black-tinted brake band manufactured according to the invention;

[0021] - Figure 3b Shows Figure 3a Magnified details of the image;

[0022] - Fig. 4a shows a picture of a brake disc similar to the one shown in the picture in Fig. 2 , but having a conventional brake band having the colour of stainless steel; and - Fig. 4b shows an enlarged detail of the picture in Fig. 4a .

[0023] Elements or parts of elements that are common to the embodiments described below will be denoted by the same reference numerals. DETAILED DESCRIPTION

[0024] With reference to the above-mentioned figures, reference numeral 1 denotes as a whole a brake disc according to the present invention.

[0025] According to the general structural solution of the invention shown in the attached drawings, a disc brake 1 comprises a brake 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 1.

[0026] In particular, the brake disc 1 may be of the ventilated type.

[0027] Advantageously, the brake disc 1 may be provided with portions adapted to secure the disc to a vehicle.

[0028] Typically, if the brake disc is for a motorcycle, the fixed portion is a hub connection element known as a bell. Alternatively, as shown in the figures, the fixed portion may comprise a plurality of appendages 4 extending radially in the brake band by being directly connected to the hub, or the fixed portion may comprise a plurality of appendages extending radially outside the brake band by being connected to the outermost part of the rim (peripheral brake disc).

[0029] Typically, if the brake disc is for a motor vehicle, the fixed part is a hub connection element known as a bell. Alternatively, the fixed part may comprise a plurality of appendages extending radially outside the brake band by being connected to the outermost part of the rim (peripheral brake disc).

[0030] The bell in a brake disc for a motorcycle or motor vehicle (if provided) may be made in one piece with the brake band, or may be made separately and then fixed to the brake band by means of suitable connecting elements or by means of other processes (i.e. co-casting).

[0031] The fixed part of a brake disc for a motorcycle or motor vehicle, whether it comprises a bell or a plurality of appendages, may be made of the same material as the brake band, such as steel or grey cast iron, or it may be made of another suitable material, such as aluminium. In particular, the entire disc, i.e. the brake band and the fixed part, may be made of stainless steel.

[0032] The brake band is made by casting. Similarly, the fixing part and / or the bell may be made by casting.

[0033] Preferably, if the brake disc is used for a motorcycle, the brake band and its fastening part are produced by punching.

[0034] Preferably, if the brake disc is for a motor vehicle, both the brake band and the bell can be obtained by casting; or the brake band can be obtained by blanking and the bell can be obtained by casting; or the brake band can be obtained by casting and the bell can be obtained by deep drawing.

[0035] The fixing part can be made in a single body with the brake band (as shown in the figures), or it can be made in a separate body and connected to the brake band in a mechanical manner.

[0036] The brake band 2 is made of grey cast iron or steel. Preferably, the brake band 2 is made of stainless steel.

[0037] According to the preferred embodiment shown in the drawings, the brake disc 1 is a brake disc for a motorcycle. However, the brake disc 1 can also be a brake disc for a motor vehicle.

[0038] The disc 1 comprises a surface coating 3 which covers at least one of the two braking surfaces of the braking band.

[0039] According to the invention, the above-mentioned surface coating 3 is based on a mixture of one or more aluminum oxides and one or more titanium oxides. This surface coating 3 has a darker color than the steel of the brake band 2 .

[0040] Preferably, the surface coating part 3 comprises:

[0041] - 55 to 95% by weight of one or more aluminum oxides;

[0042] - 5 to 45% by weight of one or more titanium oxides; and

[0043] - 0 to 40% by weight of one or more oxides selected from the group consisting of manganese oxides, iron oxides and nickel oxides. Preferably, the one or more oxides - where provided - are selected from the group consisting of MnO, MnO 2 , Mn 2 O 3 ,FeO,Fe 3 O 4 and Ni 2 O 3 .

[0044] The surface coating part 3 may include a mixture of one or more aluminum oxides and one or more titanium oxides.

[0045] In this case, the surface coating part 3 preferably includes 70 to 95% by weight of aluminum oxide (Al 2 O 3 ) and the remainder of titanium dioxide (TiO 2 Even more preferably, the surface coating part 3 preferably includes 85 to 90% by weight of aluminum oxide (Al 2 O 3 ) and the remainder of titanium dioxide (TiO 2 ).

[0046] Alternatively, the surface coating 3 may comprise, in addition to the one or more aluminum oxides and the one or more titanium oxides, other metal oxides suitable for highlighting the black or blackish color or the darker color of the starting substrate already characterized for the surface coating 3 comprising only a mixture of one or more aluminum oxides and one or more titanium oxides.

[0047] In this case, the surface coating part 3 preferably includes:

[0048] - 55 to 85% by weight of one or more aluminum oxides;

[0049] - 10 to 40% by weight of one or more titanium oxides;

[0050] - 5 to 35% by weight of one or more oxides selected from the group consisting of: manganese oxides, iron oxides and nickel oxides. Preferably, the one or more oxides are selected from the group consisting of: MnO, MnO 2 , Mn 2 O 3 ,FeO,Fe 3 O 4 and Ni 2 O 3 .

[0051] According to a preferred embodiment, the surface coating part 3 comprises:

[0052] - 70 to 85% by weight of aluminum oxide (Al 2 O 3 );

[0053] - 10 to 25% by weight of titanium dioxide (TiO 2 );

[0054] - 5 to 20% by weight of one or more oxides selected from the group consisting of: MnO, MnO 2 , Mn 2 O 3 ,FeO,Fe 3 O 4 and Ni 2 O 3 .

[0055] In particular, the thickness of the surface coating 3 may be between 10 μm and 500 μm. Preferably, the thickness of the surface coating 3 is between 30 μm and 350 μm, and even more preferably between 50 μm and 250 μm. The selection of such a range of values ​​allows a balance to be achieved between the consumption of the protective coating layer and the limitation of the thermal expansion of the coating itself. In other words, if the thickness of the protective coating is less than 10 μm, the protective coating will be completely removed in a very short time in the event of wear. On the other hand, a thickness exceeding 500 μm may lead to poor adhesion over time due to the thermal expansion that occurs during the service life of the disc brake.

[0056] Preferably, the surface coating portion 3 is a layer obtained by depositing a material in particulate form (e.g., powder), wherein the deposition forms the coating portion by means of one of the following deposition techniques: APS (atmospheric plasma spraying); HVOF (high velocity oxygen fuel spraying, High Velocity Oxygen Fuel); HVAF (high velocity air fuel spraying, High Velocity Air Fuel); KM (kinetic metallization); laser cladding (or laser metal deposition, LMD); or cold spraying.

[0057] If through Figure 3a and Figure 3b 4a and 4b, it becomes apparent that the surface coating 3 has a darker color than the color of the stainless steel. In particular, the surface coating 3 has a black color or a blackish color or a darker color than the color of the starting substrate. Considering the different colors of the coated brake band (black or blackish or darker than the starting substrate) and the uncoated fixing parts (plurality of appendages) of the brake band, this can also be achieved by only Figure 3a to Figure 3b Seen through observation.

[0058] This allows the brake band to be coloured differently from the traditional colours of stainless steel or grey cast iron, thus meeting market demands.

[0059] In addition, it can be verified through experiments that the surface coating portion 3 has a voltage between 1100 HV 300 With 1300HV 300 The microhardness between.

[0060] Such hardness values ​​are higher than the typical approximately 400 HV for hardened stainless steels commonly used to make brake discs. 300 Hardness value.

[0061] By virtue of such hardness values ​​of the surface coating 3 , the brake disc 1 according to the invention has a longer service life than conventional brake discs made of hardened stainless steel without coating or conventional brake discs made of grey cast iron without coating.

[0062] Furthermore, it has been found through experiments that, compared with conventional brake discs made of hardened stainless steel or grey cast iron, the brake disc 1 according to the invention with a coated brake band has:

[0063] - Greater resistance to wear and abrasion;

[0064] - Greater resistance to high temperatures;

[0065] -Greater corrosion resistance.

[0066] like Figure 2b Schematically shown in FIG, the surface coating 3 can be in direct contact with the braking surface of the brake band. In this case, the surface coating 3 is the only coating on the brake disc 1.

[0067] Alternatively, if Figure 2a As schematically shown in FIG. 1 , the brake disc 1 may include a base coating portion 30 which is arranged below the surface coating portion 3 and is in direct contact with the braking surface of the brake band.

[0068] In this case, the brake disc 1 is provided with:

[0069] a base coating 30 which covers at least one of the two braking surfaces of the braking band and is made in direct contact with this surface; and

[0070] A surface coating portion 3 which covers at least one of the two braking surfaces of the brake band and is manufactured so as to cover the above-mentioned base coating portion 30 .

[0071] The base coating part 30 includes nickel and / or nickel carbide, aluminum and / or aluminum oxide, or a mixture of nickel and / or nickel carbide and aluminum and / or aluminum oxide.

[0072] Preferably, the base coating part 30 comprises 75% to 95% by weight of nickel and / or nickel carbide and the balance of aluminum and / or aluminum oxide. Even more preferably, the base coating part 30 comprises 90% to 95% by weight of nickel and / or nickel carbide and the balance of aluminum and / or aluminum oxide.

[0073] Alternatively, the above-mentioned base coating part 30 may include 100% by weight of nickel and / or nickel carbide or include 100% by weight of aluminum and / or aluminum oxide.

[0074] In particular, the base coating 30 has a thickness between 10 μm and 500 μm, preferably between 30 μm and 350 μm, and even more preferably between 50 μm and 150 μm.

[0075] Preferably, the base coating 30 is a layer obtained by depositing a material in particulate form (e.g., powder) by means of one of the following deposition techniques: APS (atmospheric plasma spraying); HVOF (high velocity oxygen fuel spraying); HVAF (high velocity air fuel spraying); KM (kinetic metallization); laser cladding (or laser metal deposition, LMD); or cold spraying.

[0076] Advantageously, the base coating 30 performs a mechanical "anchoring" function for the surface coating 3, while the surface coating 3 has a coloring and anti-wear function. In fact, the base coating 30 formed of nickel / nickel oxide and / or aluminum / aluminum oxide has an intermediate thermal expansion coefficient between the base material (steel or gray cast iron) and the surface coating 3, which is formed of one or more aluminum oxides, one or more titanium oxides, and possibly manganese oxides, iron oxides and nickel oxides. This gives the base coating 30 the ability to reduce the difference in thermal expansion between the base material and the surface coating 3, thereby reducing the risk of causing cracks and fissures in the protective surface coating 3.

[0077] With respect to the anti-wear and coloring functions, the protective surface coating 3 is not affected by the presence of the protective base coating 30 .

[0078] As described above, the surface coating portion 3 and the base coating portion 30 (if provided) cover at least one of the two braking surfaces of the braking band.

[0079] Preferably, if Figure 2a and Figure 2b As shown in FIG. 2 , the brake band 2 is coated at both braking surfaces 2 a and 2 b of the brake band 2 .

[0080] In particular, the surface coating 3 and the base coating 30 (if provided) may cover the braking band only on a single braking surface or may cover the braking band on both braking surfaces.

[0081] According to an embodiment not shown in the drawings, the surface coating 3 and the base coating 30 (if provided) can also extend to other parts of the disc 1, such as the annular fixing part 4 and the bell (if provided), so as to cover the entire surface of the disc 1. In particular, the surface coating 3 and the base coating 30 (if provided) can cover only the fixing part or only the bell in addition to the braking band. This is mainly chosen for aesthetic reasons, in order to have a uniform color and / or finishing over the entire disc or between some parts of the disc.

[0082] Coating the entire brake disc 1 is convenient, for one reason, to avoid corrosion / oxidation phenomena, in particular associated with the contact portion between the bell and the hub, which could make assembly difficult or cause malfunctions (alteration of the flatness of the mating surfaces).

[0083] Advantageously, at least a portion of the at least one braking surface 2a or 2b covered by the surface coating 3 or base coating 30 (if provided) may comprise an activated surface having a rough profile. Such a rough profile is filled by the coating.

[0084] In particular, such a rough profile may be defined by one or more grooves or channels, each of which is bounded by at least one pair of protrusions.

[0085] Such an activated surface can be obtained by subjecting the braking surface (before depositing the coating) to a treatment suitable for increasing the surface roughness of the braking surface by chip removal machining or laser engraving or plastic deformation.

[0086] Operationally, the function of the activated surface is to increase the adhesion capabilities of the surface coating 3 deposited on the braking surface.

[0087] In order to simplify the present disclosure, the brake disc 1 will now be described together with the method according to the invention. The brake disc 1 is preferably, but not necessarily, manufactured by the method according to the invention as described below.

[0088] According to the general implementation of the method according to the present invention, the method comprises the following steps:

[0089] a) preparing a brake disc comprising a brake band 2 provided with two opposite braking surfaces 2a, 2b, each of which at least partially defines one of the two main face portions of the disc, the brake band being made of grey cast iron or steel, preferably of stainless steel;

[0090] b) depositing a layer of a granular material based on a mixture of one or more aluminium oxides and one or more titanium oxides on the brake disc, thereby forming a surface coating 3 covering at least one of the two braking surfaces of the brake band.

[0091] The surface coating portion 3 has a darker color than the steel of the brake band 2 .

[0092] Preferably, the particulate material deposited in the deposition step b) to form the surface coating 3 comprises:

[0093] - 55 to 95% by weight of one or more aluminum oxides;

[0094] - 5 to 45% by weight of one or more titanium oxides; and

[0095] - 0 to 40% by weight of one or more oxides selected from the group consisting of manganese oxides, iron oxides and nickel oxides.

[0096] Preferably, the one or more oxides (if provided) are selected from: MnO, MnO 2 , Mn 2 O 3 ,FeO,Fe 3 O 4 and Ni 2 O 3 .

[0097] The particulate material deposited during the deposition step b) to form the surface coating 3 may comprise a mixture of one or more aluminum oxides and one or more titanium oxides.

[0098] In this case, the particulate material deposited in step b) preferably comprises 70 to 95% by weight of aluminum oxide Al 2 O 3 Even more preferably, the particulate material deposited in step b) preferably comprises 85 to 90% by weight of alumina Al2O3 and the balance of titanium dioxide TiO2. 2 .

[0099] Alternatively, the particulate material deposited in deposition step b) to form the surface coating 3 may comprise, in addition to the one or more aluminum oxides and the one or more titanium oxides, further metal oxides suitable for highlighting the black or blackish color or the darker color of the starting substrate, which has been characterized for the surface coating 3 comprising only a mixture of one or more aluminum oxides and one or more titanium oxides.

[0100] In this case, the particulate material deposited in step b) preferably comprises:

[0101] - 55 to 85% by weight of one or more aluminum oxides;

[0102] - 10 to 40% by weight of one or more titanium oxides;

[0103] - 5 to 35% by weight of one or more oxides selected from the group consisting of: manganese oxides, iron oxides and nickel oxides. Preferably, the one or more oxides are selected from the group consisting of: MnO, MnO 2 , Mn 2 O 3 ,FeO,Fe 3 O 4 and Ni 2 O 3 .

[0104] According to a preferred embodiment, the particulate material deposited in step b) comprises:

[0105] - 70 to 85% by weight of aluminum oxide (Al 2 O 3 );

[0106] - 10 to 25% by weight of titanium dioxide (TiO 2 );

[0107] - 5 to 20% by weight of one or more oxides selected from the group consisting of: MnO, MnO 2 , Mn 2 O 3 ,FeO,Fe 3 O 4 and Ni 2 O 3 .

[0108] Advantageously, the surface coating 3 obtained at the end of the deposition step b) has a black or blackish colour or a darker colour than that of the starting substrate.

[0109] Advantageously, the surface coating 3 obtained at the end of the deposition step b) has a resistance between 1100 HV 300 With 1300HV 300 The microhardness between.

[0110] Preferably, the deposition step b) is performed so that the surface coating 3 has a thickness comprised between 10 μm and 500 μm, preferably between 30 μm and 350 μm and even more preferably between 50 μm and 250 μm.

[0111] As mentioned above, the selection of such a range of values ​​allows a balance to be achieved between the consumption of the protective coating layer and the limitation of the thermal expansion of the coating itself. In other words, if the thickness of the protective coating is less than 10 μm, the protective coating will be completely removed in a very short time in the event of wear. On the other hand, a thickness exceeding 500 μm may lead to poor adhesion over time due to the thermal expansion that occurs during the service life of the disc brake.

[0112] Preferably, the surface coating 3 is obtained by performing step b) by means of the following deposition techniques: APS (atmospheric plasma spray); HVOF (high velocity oxygen fuel spray); HVAF (high velocity air fuel spray); KM (kinetic metallization); laser cladding (or laser metal deposition, LMD); or cold spraying.

[0113] Advantageously, the material in the form of particles deposited to form the surface coating 3 in step e) has a particle size between 5 μm and 40 μm. The value of selecting this range allows the coating to have high performance in terms of density, hardness and limited porosity. Such a range is selected by balancing the following two opposite requirements: porosity reduction and adhesion improvement. Smaller particle sizes (and therefore lower quality) of particles form a layer with fewer pores and more compact, but lower quality means that the kinetic energy is lower during the step of depositing the coating, and therefore adhesion may be lower.

[0114] The surface coating 3 may be obtained by depositing a granular material in direct contact with the braking surface of the brake band.

[0115] Alternatively, the surface coating 3 may be obtained by depositing the granular material not in contact with the braking surface of the brake band but over the base coating 30 previously deposited on the braking surface of the brake band 2 .

[0116] To this end, the method preferably comprises the following step c): depositing a layer of material in granular form on the disc, thereby forming a base coating 30, the material comprising nickel and / or nickel carbide, aluminum and / or aluminum oxide, or a mixture of nickel and / or nickel carbide and aluminum and / or aluminum oxide, the base coating 30 covering at least one of the two braking surfaces of the brake band in direct contact with the at least one braking surface.

[0117] Operationally, such a step c) is then carried out before the above-mentioned step b) whereby the surface coating 3 is deposited over the base coating 30 .

[0118] Preferably, the granular material deposited in the deposition step c) to form the above-mentioned base coating portion 30 includes 75% to 95% by weight of nickel and / or nickel carbide and the balance of aluminum and / or aluminum oxide. Preferably, the granular material deposited in step c) includes 90% to 95% by weight of nickel and / or nickel carbide and the balance of aluminum and / or aluminum oxide.

[0119] Preferably, the deposition step c) is carried out so that the base coating 30 has a thickness between 10 μm and 500 μm, preferably between 30 μm and 350 μm, and even more preferably between 50 μm and 150 μm. Within this thickness range, the base coating 30 allows the above-mentioned weakening effect on thermal strain, thereby helping to maintain the integrity of the surface coating 3.

[0120] Preferably, the base coating 30 is obtained by performing step c) by means of the following deposition techniques: APS (atmospheric plasma spray); HVOF (high velocity oxygen fuel spray); HVAF (high velocity air fuel spray); KM (kinetic metallization); laser cladding (or laser metal deposition, LMD); or cold spraying.

[0121] Advantageously, the material in the form of particles deposited in step d) to form the base coating 30 has a particle size between 5 μm and 40 μm. The selection of such a range of values ​​allows the coating to have high performance in terms of density and ability to adhere to the deposition surface. Such a range is selected by balancing the following two opposing needs: porosity reduction and adhesion provision. Particles of smaller particle size (and therefore lower mass) form less porous and more compact layers, but lower mass means lower kinetic energy during the deposition process, and therefore lower adhesion may be achieved.

[0122] Preferably, both deposition step b) and, if applicable, deposition step c) are performed at an average deposition temperature on the component not exceeding 250°C.

[0123] Preferably, the method comprises a step d) of preparing the surface for the base coating 30 (if provided) and the surface coating 3 to form. Therefore, this step d) must be performed before performing step b) or step c) (if included).

[0124] In particular, the surface preparation step d) may comprise a sub-step d1) of cleaning the surface with a solvent suitable for removing oil or dirt.

[0125] Preferably, the preparation step d) may include a sub-step d2) of subjecting at least a portion of the at least one braking surface 2a or 2b to a treatment suitable for increasing the surface roughness of at least a portion of the at least one braking surface 2a or 2b by chip removal machining or laser engraving or plastic deformation, thereby forming an activated portion of the braking surface.

[0126] Operationally, the function of this sub-step d2) is to increase the adhesion capabilities of the base coating 30 (if provided) or the surface coating 3 deposited on the braking surface.

[0127] In particular, the function of this sub-step d2) is to form a rough profile on the braking surface, which rough profile may be defined by one or more grooves or channels, each of which is delimited by at least one pair of protrusions.

[0128] Advantageously, the method may comprise a step e) of surface finishing the above-mentioned surface coating, for example by machining (grinding, turning, brushing, etc.).

[0129] In particular, such surface conditioning of the coated disc helps to restore the coated disc to geometrical and dimensional operating tolerances that may have been lost during deposition steps b) and c), as well as to ensure a suitable surface roughness to optimize frictional contact with the friction element.

[0130] As can be understood from the above description, the brake disc according to the invention allows to overcome the disadvantages of the prior art.

[0131] By means of the surface coating 3, the brake disc 1 according to the invention has a darker color than the color of steel or gray cast iron. In particular, the surface coating 3 has a black color or a blackish color or a darker color than the color of the starting substrate. This allows the color of the brake band to be differentiated from the traditional colors of stainless steel or gray cast iron, thereby meeting market demands.

[0132] Compared to conventional brake discs made of hardened stainless steel without a coating, the brake disc 1 according to the invention has a longer service life by virtue of the surface coating 3 covering at least one of the two braking surfaces of the belt.

[0133] Compared to conventional brake discs made of hardened stainless steel or grey cast iron, the brake disc 1 according to the invention with a coated brake band has:

[0134] - a black or blackish color or a darker color of the starting substrate at least in the coated surface at the brake band;

[0135] - Greater resistance to wear and abrasion, resulting in reduced dust emissions;

[0136] - Greater resistance to high temperatures;

[0137] - Greater corrosion resistance, thus ensuring more stable working conditions over time.

[0138] By virtue of the lower thermal conductivity of the material used for the coating compared to steel or grey cast iron, the surface coating 3 also serves as a heat barrier for the underlying brake band.

[0139] By means of the present invention, brake discs made of steel or gray cast iron and having a black color or a blackish color or a color darker than the color of the starting substrate can be manufactured at significantly lower costs when compared to brake discs currently available on the market that are made only of carbon or made of carbon ceramic materials and have a black color or a blackish color or a color darker than the color of the starting substrate.

[0140] In order to meet possible specific requirements, a person skilled in the art may make numerous changes and modifications to the method and the brake disc described above, all of which are included within the scope of the present invention as defined by the appended claims.

Claims

1. A brake disc for a disc brake, in particular for a disc brake for a motorcycle or a motor vehicle, the disc comprising a brake band (2), the brake band (2) being provided with two opposite braking surfaces (2a, 2b), each of the braking surfaces (2a, 2b) at least partially defining one of the two main face portions of the disc (1), the brake band (2) being made of grey cast iron or steel, preferably of stainless steel, the disc comprising a surface coating (3), the surface coating (3) covering at least one of the two braking surfaces of the brake band, It is characterized in that The surface coating (3) is based on a mixture of one or more aluminum oxides and one or more titanium oxides, the surface coating (3) having a darker color relative to the steel or grey cast iron of the brake band (2).

2. The disk according to claim 1, wherein The surface coating part (3) comprises: - 55 to 95% by weight of one or more aluminum oxides; - 5 to 45% by weight of one or more titanium oxides; and - 0 to 40% by weight of one or more oxides selected from the group consisting of manganese oxides, iron oxides and nickel oxides, preferably 0 to 40% by weight of one or more oxides selected from the group consisting of MnO, MnO2, Mn2O3, FeO, Fe3O4 and Ni2O3.

3. The disc according to claim 1 or 2, wherein: The surface coating (3) comprises only a mixture of one or more aluminum oxides and one or more titanium oxides.

4. The disk according to claim 3, wherein The surface coating portion (3) comprises 70% to 95% by weight of aluminum oxide (Al2O3) and the balance of titanium dioxide (TiO2). Preferably, the surface coating portion (3) comprises 85% to 90% by weight of aluminum oxide (Al2O3) and the balance of titanium dioxide (TiO2).

5. The disk according to claim 1 or 2, wherein: The surface coating part (3) comprises: - 55 to 85% by weight of one or more aluminum oxides; - 10 to 40% by weight of one or more titanium oxides; and - 5 to 35% by weight of one or more oxides selected from the group consisting of manganese oxides, iron oxides and nickel oxides, preferably 5 to 35% by weight of one or more oxides selected from the group consisting of MnO2, Fe3O4 and Ni2O3.

6. The disk according to claim 5, wherein The surface coating part (3) comprises: - 70 to 85% by weight of aluminum oxide (Al2O3); - 10 to 25% by weight of titanium dioxide (TiO2); - 5 to 20% by weight of one or more oxides selected from the group consisting of: MnO, MnO2, Mn2O3, FeO, Fe3O4 and Ni2O3.

7. A tray according to any one of the preceding claims, wherein The surface coating (3) has a black or blackish color or in any case a darker color than the starting substrate.

8. A tray according to any one of the preceding claims, wherein The surface coating portion (3) has a voltage between 1100 HV 300 With 1300HV 300 The microhardness between.

9. A tray according to any one of the preceding claims, wherein The surface coating (3) has a thickness between 10 μm and 500 μm, and preferably, the surface coating (3) has a thickness between 30 μm and 350 μm, and even more preferably, the surface coating (3) has a thickness between 50 μm and 250 μm.

10. A tray according to any one of the preceding claims, wherein The surface coating (3) is a layer obtained by the following deposition techniques: APS (atmospheric plasma spraying); HVOF (high velocity oxygen fuel spraying); HVAF (high velocity air fuel spraying); KM (kinetic metallization); Laser cladding; or cold spraying.

11. A tray according to any one of the preceding claims, wherein The surface coating portion (3) is in contact with the braking surface of the brake band.

12. A disc according to any one of claims 1 to 10, comprising a base coating (30), which is arranged below the surface coating (3) and is in direct contact with the braking surface of the brake band, and the base coating (30) comprises nickel and / or nickel carbide, and / or aluminum and / or aluminum oxide.

13. The disk according to claim 12, wherein The base coating portion (30) comprises 75% to 95% by weight of nickel and / or nickel carbide and the balance of aluminum and / or aluminum oxide. Preferably, the base coating portion (30) comprises 90% to 95% by weight of nickel and / or nickel carbide and the balance of aluminum and / or aluminum oxide.

14. The tray according to claim 12, wherein The base coating (30) includes 100% by weight of nickel and / or nickel carbide, or the base coating (30) includes 100% by weight of aluminum and / or aluminum oxide.

15. A disc according to claim 12, 13 or 14, wherein The base coating (30) has a thickness between 10 μm and 500 μm, and preferably, the base coating (30) has a thickness between 30 μm and 350 μm, and even more preferably, the base coating (30) has a thickness between 50 μm and 150 μm.

16. A tray according to any one of claims 12 to 15, wherein The base coating (30) is a layer obtained by the following deposition techniques: APS (atmospheric plasma spray); HVOF (high velocity oxygen fuel spray); HVAF (high velocity air fuel spray); KM (kinetic metallization); laser cladding; or cold spraying.

17. A tray according to any one of the preceding claims, wherein The brake disc is a brake disc for a motorcycle.

18. A method for manufacturing a brake disc for a disc brake, in particular for a disc brake for a motorcycle, the method comprising the following steps: a) preparing a brake disc, said disc comprising a brake band (2), said brake band (2) being provided with two opposite brake surfaces (2a, 2b), each of said brake surfaces (2a, 2b) at least partially defining one of two main face portions of said disc, said brake band being made of grey cast iron or steel, preferably of stainless steel; b) depositing a layer of granular material on the brake disc, thereby forming a surface coating (3) covering at least one of the two braking surfaces of the brake band, the granular material being based on a mixture of one or more aluminum oxides and one or more titanium oxides, the surface coating (3) having a darker color relative to the steel of the brake band (2).

19. The method according to claim 18, wherein: The granular material forming the surface coating portion (3) comprises: - 55 to 95% by weight of one or more aluminum oxides; - 5 to 45% by weight of one or more titanium oxides; and - 0 to 40% by weight of one or more oxides selected from the group consisting of manganese oxides, iron oxides and nickel oxides, preferably 0 to 40% by weight of one or more oxides selected from the group consisting of MnO, MnO2, Mn2O3, FeO, Fe3O4 and Ni2O3.

20. The method according to claim 18 or 19, wherein: The particulate material forming the surface coating (3) comprises only a mixture of one or more aluminum oxides and one or more titanium oxides.

21. The method according to claim 20, wherein: The granular material deposited in the deposition step b) to form the surface coating portion (3) comprises 70 to 95% by weight of aluminum oxide (Al2O3) and the balance titanium dioxide (TiO2). Preferably, the granular material deposited in the deposition step b) to form the surface coating portion (3) comprises 85 to 90% by weight of aluminum oxide (Al2O3) and the balance titanium dioxide (TiO2).

22. The method according to claim 18 or 19, wherein: The particulate material deposited in the deposition step b) to form the surface coating (3) comprises: - 55 to 85% by weight of one or more aluminum oxides; - 10 to 40% by weight of one or more titanium oxides; and - 5 to 35% by weight of one or more oxides selected from the group consisting of manganese oxides, iron oxides and nickel oxides, preferably 5 to 35% by weight of one or more oxides selected from the group consisting of MnO, MnO2, Mn2O3, FeO, Fe3O4 and Ni2O3.

23. The method according to claim 22, wherein: The particulate material deposited in the deposition step b) to form the surface coating (3) comprises: - 70 to 85% by weight of aluminum oxide (Al2O3); - 10 to 25% by weight of titanium dioxide (TiO2); - 5 to 20% by weight of one or more oxides selected from the group consisting of: MnO, MnO2, Mn2O3, FeO, Fe3O4 and Ni2O3.

24. The method according to any one of claims 18 to 23, wherein: The surface coating (3) has a black or blackish color or in any case a darker color than the starting substrate.

25. The method according to any one of claims 18 to 24, wherein: The surface coating portion (3) has a voltage between 1100 HV 300 With 1300HV 300 The microhardness between.

26. The method according to any one of claims 18 to 24, wherein: The surface coating (3) has a thickness between 10 μm and 500 μm, and preferably, the surface coating (3) has a thickness between 30 μm and 350 μm, and even more preferably, the surface coating (3) has a thickness between 50 μm and 250 μm.

27. The method according to any one of claims 18 to 26, wherein: The surface coating (3) is obtained by the following deposition techniques: APS (atmospheric plasma spray); HVOF (high velocity oxygen fuel spray); HVAF (high velocity air fuel spray); KM (kinetic metallization); laser cladding; or cold spraying.

28. The method according to any one of claims 18 to 27, wherein: The surface coating (3) is obtained by depositing the granular material in direct contact with the braking surface of the brake band.

29. A method according to any one of claims 18 to 27, comprising the step c) of depositing a layer of granular material on the disc to form a base coating (30), the granular material comprising nickel and / or nickel carbide and / or aluminium and / or aluminium oxide, the base coating (30) covering at least one of the two braking surfaces of the brake band in direct contact with the at least one braking surface, wherein The step c) is performed before the step b), and the surface coating portion (3) is formed above the base coating portion (30).

30. The method of claim 29, wherein: The granular material deposited in the deposition step c) to form the base coating portion (30) comprises 75% to 95% by weight of nickel and / or nickel carbide and the remainder of aluminum and / or aluminum oxide. Preferably, the granular material deposited in the deposition step c) to form the base coating portion (30) comprises 90% to 95% by weight of nickel and / or nickel carbide and the remainder of aluminum and / or aluminum oxide.

31. The method of claim 29, wherein: The granular material deposited in deposition step c) to form the base coating (30) comprises 100% by weight of nickel and / or nickel carbide, or the granular material deposited in deposition step c) to form the base coating (30) comprises 100% by weight of aluminum and / or aluminum oxide.

32. The method of claim 29, 30 or 31, wherein: The base coating (30) has a thickness between 10 μm and 500 μm, and preferably, the base coating (30) has a thickness between 30 μm and 350 μm, and even more preferably, the base coating (30) has a thickness between 50 μm and 150 μm.

33. The method according to any one of claims 29 to 32, wherein: The base coating (30) is obtained by the following deposition techniques: APS (atmospheric plasma spray); HVOF (high velocity oxygen fuel spray); HVAF (high velocity air fuel spray); KM (kinetic metallization); laser cladding; or cold spraying.

34. A method according to any one of claims 18 to 33, comprising a step d) of preparing the surface of the disc (1) before carrying out step b) or, if step c) is envisaged, before carrying out step c).

35. The method according to any one of claims 18 to 34, comprising the step e) of surface finishing the surface coating (3).

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