FORM 2
THE PATENTS ACT, 1970
(39 OF 1970)
AND
THE PATENTS RULES, 2003
COMPLETE SPECIFICATION
(See Section 10; rule 13)
TITLE OF THE INVENTION “AUGMENTED BRAKE ROTOR HAVING A BRAKE SLEEVE”
APPLICANT(S)
TATA MOTORS LIMITED
Bombay House, 24 Homi Mody Street,
Hutatma Chowk, Mumbai 400 001, Maharashtra, India; an Indian company.
PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed.

FIELD OF THE INVENTION
[001] The present invention relates to a brake rotor, and more specifically related to a brake rotor having a brake sleeve formed on its surface.
BACKGROUND OF THE INVENTION
[002] A brake rotor may be connected to a wheel of a vehicle for enabling braking of the vehicle. The brake rotor may be disc shaped, and may be also referred to as a brake disc. The brake rotor may be made of an iron alloy, such as grey cast iron. Conventional brake rotors tend to have less corrosion resistance and wear resistance. Consequently, rust is formed on the brake rotors and the brake rotors undergo wear over the course of their usage.
[003] The wear and the rust formation, even though minor surface defects, may impact the braking performance of the brake rotors. Accordingly, the brake rotors are to be replaced. In other words, brake rotors may have to be scrapped for minor surface defects thereon. Further, the lack of wear resistance of the brake rotors may cause particles of the brake rotor to fall-off, which may cause particulate matter emissions and air pollution.
SUMMARY OF THE INVENTION
[004] An augmented brake rotor according to the present subject matter includes a brake rotor and a brake sleeve formed on a surface of the brake rotor. The brake sleeve may include at least one of: particles having iron, tungsten carbide particles, silicon carbide particles, and chromium carbide particles. A method for manufacturing the augmented brake rotor includes depositing sleeve-forming particles on the surface of the brake rotor to form a layer on the surface, compacting the layer on the surface of the brake rotor, oxidizing the layer, and heating the brake

rotor and the layer. The heating enables adhesion between the layer and the brake rotor and formation of the brake sleeve on the surface.
BRIEF DESCRIPTION OF FIGURES
[005] The features, aspects, and advantages of the subject matter will be better understood with regard to the following description, and accompanying figures. The use of the same reference number in different figures indicates similar or identical features and components.
[006] Fig. 1 schematically illustrates an augmented brake rotor (ABR), according to an implementation of the present subject matter.
[007] Fig. 2 illustrates an exploded view of an ABR, according to an implementation of the present subject matter.
[008] Fig. 3 illustrates a method for manufacturing an ABR, according to an implementation of the present subject matter.
[009] Fig. 4 illustrates a method for manufacturing an ABR, according to an implementation of the present subject matter.
[0010] Fig. 5(a) illustrates a brake rotor, according to an implementation of the present subject matter.
[0011] Fig. 5(b) illustrates a brake rotor having layers of sleeve-forming particles deposited thereon, according to an implementation of the present subject matter.
[0012] Fig. 5(c) illustrates an ABR, according to an implementation of the present subject matter.

DETAILED DESCRIPTION OF INVENTION
[0013] The present subject matter relates to an augmented brake rotor. The augmented brake rotor of the present subject matter is wear-resistant and corrosion-resistant, and has a long useful life.
[0014] In accordance with an implementation of the present subject matter, a method for forming the augmented brake rotor includes depositing sleeve-forming particles on a surface of a brake rotor to form a layer on the surface. The sleeve-forming particles include at least one of: particles having iron, tungsten carbide particles, silicon carbide particles, and chromium carbide particles. The method also includes compacting the layer on the surface of the brake rotor by pressing the layer against the surface. In an example, the compacting may be performed until the thickness of the layer reduces to a thickness in a range of about 250-450 µm. The layer is then oxidized and then heated. The heating may be performed at a high temperature, such as at a temperature in a range of about 850° C to about 1100° C. The heating enables adhesion between the layer and the brake rotor, and formation of a brake sleeve on the surface.
[0015] The brake rotor having a coating of the brake sleeve may be referred to as an augmented brake rotor. When the augmented brake rotor is used on a vehicle, brake pads of the vehicle may engage with the brake sleeve of the augmented brake rotor.
[0016] The brake sleeve forms a wear-resistant and corrosion-resistant coating on the surface of the brake rotor, thereby preventing wear and corrosion of the brake rotor. Thus, falling-off of particles of the brake rotor are prevented, thereby reducing particulate emissions and air pollution. Further, even if the brake sleeve wears (e.g., after a prolonged usage of the augmented brake rotor), the brake sleeve may be removed from the surface of the brake rotor, and a new brake sleeve may

be formed on the surface. Therefore, the brake rotor need not be replaced, and its life can be significantly increased.
[0017] The method utilized for forming the brake sleeve on the brake rotor can be used to provide a sleeve of high thickness, such as more than 250 µm, on the brake rotor. Further, the brake sleeve formed has a strong metallurgical bonding to the brake rotor. Such a high thickness and a strong metallurgical bonding may not be achieved using thermal spray coating and additive manufacturing. Further, the method of the present subject matter avoids subjecting the brake rotor to very high temperatures. Therefore, damage to microstructure of the brake rotor due to the high temperature is prevented. The retention of the microstructure enables retaining the desirable properties of the brake rotor, such as good thermal conductivity and damping performance. Further, since heating at high temperature is prevented, energy consumption of the method is minimal.
[0018] The implementations herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting implementations that are illustrated in the accompanying drawings and detailed in the following description. It should be understood, however, that the following descriptions, while indicating preferred implementations and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the implementations herein without departing from the spirit thereof, and the implementations herein include all such modifications. The examples used herein are intended merely to facilitate an understanding of ways in which the implementations herein can be practiced and to further enable those skilled in the art to practice the implementations herein. Accordingly, the examples should not be construed as limiting the scope of the implementations herein.
[0019] Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the implementations herein. Also, the

various implementations described herein are not necessarily mutually exclusive, as some implementations can be combined with one or more other implementations to form new implementations.
[0020] Referring now to the drawings, and more particularly to Figs. 1 through 5(c), where similar reference characters denote corresponding features consistently throughout the figures, there are shown preferred implementations. Further, for the sake of simplicity, and without limitation, the same numbers are used throughout the drawings to reference like features and components. The implementations herein will be better understood from the following description with reference to the drawings.
[0021] Fig. 1 schematically illustrates an augmented brake rotor (ABR) 100, according to an implementation of the present subject matter. The ABR 100 may be connected to a wheel of a vehicle (not shown in Fig. 1) for enabling braking of the vehicle. The vehicle may be, for example, a passenger vehicle (PV), such as a car, or a commercial vehicle (CV), such as a bus or a truck. The ABR 100 includes a brake rotor 102 that forms a core of the ABR 100. The brake rotor 102 may be disc-shaped, and may also be referred to as the brake disc. The brake rotor may be made, for example, of an iron alloy. In an example, the brake rotor 102 may be made of grey cast iron.
[0022] The ABR 100 may also include a brake sleeve, also referred to as a sleeve, formed on a surface of the brake rotor 102. For example, the ABR 100 may include a first brake sleeve 104 and a second brake sleeve 106 formed on opposite surfaces of the brake rotor 102.
[0023] Fig. 2 illustrates an exploded view of the ABR 100, according to an implementation of the present subject matter. As illustrated, the first brake sleeve 104 and the second brake sleeve 106 are formed on opposite surfaces of the brake rotor 102. The surfaces may be, for example, a surface 202 and a surface opposite

the surface 202 (not shown in Fig. 2). A surface of the brake rotor 102 on which a brake sleeve is formed may be a surface with which brake pads of the vehicle would engage in the absence of the brake sleeve. Accordingly, when the ABR 100, having the brake sleeves, is installed in a vehicle, the brake pads of the vehicle may engage with the first brake sleeve 104 and the second brake sleeve 106 on application of brakes. In other words, the first brake sleeve 104 and the second brake sleeve 106 form a protective coating on both sides of the brake rotor 102. The protective coating prevents the brake pads from contacting the brake rotor 102, thereby preventing wear of the brake rotor 102. The protective coating also prevents exposure of the brake rotor 102 to the atmosphere, thereby preventing rusting of the brake rotor 102.
[0024] The brake sleeves may be made of particles that are wear resistant and corrosion resistant. For example, the brake sleeves may include tungsten carbide (WC) particles, silicon carbide (SiC) particles, and chromium carbide (e.g., Cr3C2) particles. The wear-resistant and corrosion-resistant nature of the particles prevents wear and corrosion of the brake sleeves even after usage of the ABR 100 for prolonged periods. The sleeve may also include particles including iron. The particles including iron may be pure/near-pure iron particles. In another example, the particles may be particles of one or more iron alloys, such as iron alloys having carbon, boron, and/or silicon.
[0025] The thickness of the first brake sleeve 104 and the second brake sleeve 106 may be high, such as at least 250 µm. Despite the high thickness, the brake sleeves may be strongly bound to the surfaces of the brake rotor 102. Some example methods of forming a thick brake sleeve with strong metallurgical bonding to the surface of the brake rotor 102 will be explained below.
[0026] Figs. 3 and 4 illustrate method 300 and 400, respectively, for manufacturing an ABR, according to implementations of the present subject matter. The ABR may be, for example, the ABR 100. The orders in which the methods 300 and 400 are

described are not intended to be construed as limitations, and any number of the described method blocks can be combined in any order to implement the methods 300 and 400, or alternative methods. Additionally, individual blocks may be deleted from the methods 300 and 400 without departing from the scope of the subject matter described herein.
[0027] Referring to the method 300, at block 302, sleeve-forming particles may be deposited on a surface of a brake rotor to form a layer on the surface. The brake rotor may be, for example, the brake rotor 102. The sleeve-forming particles include particles having iron, tungsten carbide particles, silicon carbide particles, chromium carbide particles, or any combination thereof.
[0028] At block 304, the layer may be compacted on the surface of the brake rotor by pressing the layer against the surface. At block 306, the layer is oxidized. Further, at block 308, the brake rotor and the layer are heated. The heating enables adhesion between the layer and the brake rotor and forms a brake sleeve on the surface of the brake rotor. The brake sleeve may be, for example, the first brake sleeve 104 or the second brake sleeve 106. The brake rotor and the brake sleeve may be collectively referred to as the ABR.
[0029] In an example, the surface of the brake rotor may have a sleeve previously formed thereon and may have to be replaced. In such a case, prior to depositing the sleeve-forming particles at block 302, the previously-formed sleeve may be removed.
[0030] Fig. 4 illustrates a method 400 for manufacturing an ABR, according to an implementation of the present subject matter.
[0031] At block 402, a brake rotor is manufactured. The brake rotor may be, for example, the brake rotor 102. In an example, the brake rotor may be manufactured

using a casting process, such as sand casting. Further, the brake rotor may be made of grey cast iron.
[0032] At block 404, a surface of the brake rotor is prepared for formation of a brake sleeve thereon. The surface may be, for example, the surface 202 and the surface of the brake rotor 102 opposite the surface 202. In an example, the surface preparation may include making the surface smooth. Further, in an example, the surface preparation may include machining the surface and reducing the thickness of the brake rotor. The thickness of the brake rotor may be reduced because an additional layer (i.e., the brake sleeve) is to be formed on the surface. In an example, a value by which the thickness of the brake rotor is reduced may equal the thickness of the brake sleeve that is to be formed on the surface. For instance, if a brake sleeve of 400 µm is to be formed on the surface, the thickness of the brake rotor may be reduced by 400 µm. In an alternative example, the machining to reduce the thickness of the brake rotor may not be performed. Instead, the brake rotor may be so manufactured that a sum of the thickness of the brake rotor and the thickness of the brake sleeve that would be formed on the brake rotor equals the required thickness of the ABR to be manufactured. For example, if an ABR having a thickness 22800 µm is to be formed and if two brake sleeves each of 400 µm are to be formed on opposite surfaces of a brake rotor, the brake rotor may be manufactured with a thickness of 22000 µm.
[0033] At block 406, sleeve-forming particles are deposited on the surface of the brake rotor, to form a layer on the surface. In an example, the sleeve-forming particles are deposited on opposite surfaces of the brake rotor, such as the surface 202 and the surface of the brake rotor 102 opposite the surface 202. The sleeve-forming particles include particles having iron, tungsten carbide particles, silicon carbide particles, and chromium carbide particles. In an example, the thickness of the sleeve-forming particles deposited on the surface may be in a range of about 1000 microns to about 2000 microns.

[0034] Prior to depositing, the sleeve-forming particles may be mixed thoroughly, so that a homogenous mixture of the sleeve-forming particles is deposited on the surface of the brake rotor. Accordingly, the sleeve formed on the brake rotor has a uniform distribution of various particles.
[0035] In an example, the sleeve-forming particles includes about 15-20 volume percentage of tungsten carbide particles, about 10-18 volume percentage of chromium carbide particles, and about 2-4 volume percentage of silicon carbide particles. The remaining volume percentage of the sleeve-forming particles includes particles having iron, such as pure/near-pure iron particles or particles of iron alloys.
[0036] In an example, the silicon carbide particles are coated with nano-iron powder. The nano-iron power may have iron particles in a size range of nanometres (nm), such as 100-200 nm. The coating enables uniform mixing and better bonding of the silicon carbide particles with iron alloys.
[0037] The size of the sleeve-forming particles may be in microns. For example, the tungsten carbide particles may have size in a range of about 15-35 microns, the chromium carbide particles may have size in a range of about 10-30 microns, the silicon carbide particles may have size in a range of about 20-50 microns, and the particles having iron may have size in a range of about 35-70 microns.
[0038] Upon deposition of the sleeve-forming particles, at block 408, the layer of sleeve-forming particles is compacted on the surface of the brake rotor. The compacting is performed by pressing the layer against the surface. The compacting may be performed at a pressure range of, for example, about 400-650 MPa. The compacting may be performed until the thickness of the layer reduces to a desired thickness value. The thickness value may be selected such that a sufficiently thick protective coating is provided on the surface of the brake rotor, while ensuring that the cost and the weight of the ABR formed do not increase significantly. In an

example, the thickness value may be in a range of about 300 µm to about 400 µm, such as 300 µm or 320 µm.
[0039] In an implementation, the compacting may be performed in multiple stages, where a speed of compacting reduces from one stage to another. For instance, the compacting may be performed at a first speed for a first period. Subsequently, compacting may be performed at a second speed less than the first speed for a second period. Further, another stage of compacting may be performed at a third speed less than the second speed for a third period. The speed of compacting may be reduced with time to ensure good compaction and to prevent cracking of the layer of sleeve-forming particles. In an example, the first speed may be 10 mm/minute, the second speed may be 7 mm/minute, and the third speed may be 5 mm/minute. Further, the first period, the second period, and the third period may be equal to each other, and may be, for example 1 minute.
[0040] Upon compacting, at block 410, the compacted layer is subjected to oxidation treatment. The oxidation treatment converts iron in the compacted layer into iron oxides. In an example, the oxidation may be carried out at a temperature in a range of about 400° C to about 450° C.
[0041] Subsequently, at block 412, the brake rotor and the compacted layer are heated. In an example, the heating may be performed at a temperature in a range of about 850° C to about 1100° C. The heating causes cohesion among particles in the layer and adhesion between the layer and the brake rotor. Thus, the heating causes formation of the brake sleeve on the surface of the brake rotor, thereby completing manufacturing of the ABR. In an example, the particles having iron, which are part of the sleeve-forming particles deposited at block 406, may have a low melting point. The low melting point enables melting of such particles during the heating, which in turn enables better adhesion between the brake sleeve and the brake rotor.

[0042] At block 414, finishing operations may be carried out on the ABR. The finishing operations may include, for example, a machining operation.
[0043] Fig. 5(a) illustrates a brake rotor 502, according to an implementation of the present subject matter. The brake rotor 502 may correspond to the brake rotor 102. The brake rotor 502 may include a first surface 504 and a second surface (not shown in Fig. 5) opposite the first surface 504 on which sleeves are to be formed.
[0044] Fig. 5(b) illustrates the brake rotor 502 having layers of sleeve-forming particles deposited thereon, according to an implementation of the present subject matter. A first layer 506 of sleeve-forming particles is deposited on the first surface 504 (not shown in Fig. 5(b)) and a second layer 508 is deposited on the second surface.
[0045] Fig. 5(c) illustrates an ABR 510, according to an implementation of the present subject matter. The ABR 510 includes a first sleeve 512 and a second sleeve 514. The first sleeve 512 is formed from the first layer 506 when the first layer 506 is subjected to compacting, oxidizing, and heating, as explained above. Similarly, the second sleeve 514 is formed from the second layer 508 when the second layer 508 is subjected to compacting, oxidizing, and heating.
[0046] Over the course of usage of the ABR 510, the first sleeve 512 and/or the second sleeve 514 may wear out. In such a case, the worn sleeve may be removed from the surface of the brake rotor 502 and may be replaced with a new sleeve. The new sleeve may be formed by repeating the steps 406-412.
[0047] The formation of the sleeve on the brake rotor 502 ensures that the brake rotor 502 does not wear over the course of usage of the ABR 510. Further, replacement of the sleeve, while retaining the brake rotor 502, ensures that the brake rotor 502 may be used for long periods of time. Therefore, life of the brake rotor

502 can be significantly improved, and brake replacement cost for the owner of a vehicle can be reduced.
[0048] The present subject matter provides a wear-resistant and corrosion-resistant coating on the surface of the brake rotor, thereby preventing wear and corrosion of the brake rotor. Thus, falling-off of particles of the brake rotor are prevented, thereby reducing particulate emissions and air pollution. Further, even if the brake sleeve wears (e.g., after a prolonged usage of the augmented brake rotor), the brake sleeve may be removed from the surface of the brake rotor, and a new brake sleeve may be formed on the surface. Therefore, the life of the brake rotor can be significantly increased.
[0049] The method utilized for forming the brake sleeve on the brake rotor can be used to provide a sleeve of high thickness on the brake rotor. Further, the brake sleeve formed has a strong metallurgical bonding to the brake rotor. Such a high thickness and a strong metallurgical bonding may not be achieved using other methods of sleeve formation, such as thermal spray coating and additive manufacturing. Further, the method avoids subjecting the brake rotor to very high temperatures, thereby preventing damage to microstructure of the brake rotor and also reducing the energy consumption for the sleeve formation.
[0050] The foregoing description of the specific implementations will so fully reveal the general nature of the implementations herein that others can, by applying current knowledge, readily modify and/or adapt for various applications without departing from the generic concept, and, therefore, such modifications and adaptations should and are intended to be comprehended within the meaning and range of equivalents of the disclosed implementations. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the implementations herein have been described in terms of preferred implementations, those skilled in the art will

recognize that the implementations herein can be practiced with modification within the spirit and scope of the implementations as described herein.

We Claim:
1. A method for manufacturing an augmented brake rotor, the method
comprising:
depositing sleeve-forming particles on a surface of a brake rotor to form a layer on the surface, the sleeve-forming particles comprising at least one of: particles having iron, tungsten carbide particles, silicon carbide particles, and chromium carbide particles;
compacting the layer on the surface of the brake rotor by pressing the layer against the surface;
oxidizing the layer; and
heating the brake rotor and the layer, thereby enabling adhesion between the layer and the brake rotor, and formation of the brake sleeve on the surface.
2. The method as claimed in claim 1, wherein the sleeve-forming particles comprises about 15-20 volume percentage of tungsten carbide particles, about 10-18 volume percentage of chromium carbide particles, and about 2-4 volume percentage of silicon carbide particles.
3. The method as claimed in claim 1, wherein the silicon carbide particles are coated with nano-iron powder.
4. The method as claimed in claim 1, wherein the tungsten carbide particles have size in a range of about 15-35 microns, the chromium carbide particles have size in a range of about 10-30 microns, and the silicon carbide particles have size in a range of about 20-50 microns.
5. The method as claimed in claim 1, wherein the compacting is performed until thickness of the layer is in a range of about 300 µm to about 400 µm.

6. The method as claimed in claim 1, wherein the compacting comprises:
compacting at a first speed for a first period; and
compacting at a second speed for a second period after the first period, wherein the second speed is less than the first speed.
7. The method as claimed in claim 1, wherein the heating is carried out at a temperature in a range of about 850° C to about 1100° C.
8. The method as claimed in claim 1, wherein, prior to depositing the sleeve-forming particles on the surface of the brake rotor, the method comprises:
removing a previously-formed sleeve on the surface.
9. An augmented brake rotor, comprising:
a brake rotor; and
a brake sleeve formed on a surface of the brake rotor, the brake sleeve having at least one of: particles having iron, tungsten carbide particles, silicon carbide particles, and chromium carbide particles.
10. The augmented brake rotor as claimed in claim 9, wherein the brake sleeve has a thickness of at least 250 µm.
11. An augmented brake rotor, comprising:
a brake rotor; and
a brake sleeve formed on a surface of the brake rotor, wherein the brake sleeve is formed on the surface using the method as claimed in claim 1.