Method for manufacturing a brake disc and brake disc for disc brakes

1. A method for manufacturing a brake disc comprising the following operating steps:

a) preparing a brake disc, comprising a braking band and provided with two mutually opposite braking surfaces, each of which defines at least partially one of the two main faces of the disc, the braking band being made of aluminium or aluminium alloy, or being made of grey cast iron or steel;

b) depositing on the disc a layer consisting of chromium carbide (Cr3C2) and nickel-chromium (NiCr) in particulate form with HVOF (High Velocity Oxygen Fuel) technique, HVAF (High Velocity Air Fuel) technique or KM (Kinetic Metallisation) technique forming a base protective coating that consists of chromium carbide (Cr3C2) and nickle-chromium (NiCr) that covers at least one of the two braking surfaces of the braking band in direct contact with them; and

c) depositing over said base protective coating a material in particulate form consisting of tungsten carbide (WC) and cobalt (Co) with HVOF (High Velocity Oxygen Fuel) technique, HVAF (High Velocity Air Fuel) technique or KM (Kinetic Metallisation) technique forming a surface protective coating that consist of tungsten carbide (WC) and cobalt (Co) that covers at least one of the two braking surfaces of the braking band.

2. The method according to claim 1 , wherein the material in particulate form deposited in deposition step b) to create the base protective coating is constituted by 65% to 95% of chromium carbide (Cr3C2) and the remaining by nickel-chromium (NiCr).

3. The method according to claim 1 , wherein the material in particulate form deposited in deposition step c) to create the surface protective coating is constituted by 80% to 90% by weight of tungsten carbide (WC) and the remaining by cobalt (Co).

4. The method according to claim 1 , wherein both the material in particulate form deposited in deposition step b) to create the base protective coating and the material in particulate form deposited in deposition step c) to create the surface protective coating are deposited with HVOF (High Velocity Oxygen Fuel) technique.

5. The method according to claim 1 , wherein the base protective coating has a thickness between 20 μm and 60 μm.

6. The method according to claim 1 , wherein the surface protective coating has a thickness between 30 μm and 70 μm.

7. The method according to claim 1 , wherein the material in particulate form that is deposited in step b) to form the base protective coating has a particle size between 5 and 40 μm.

8. The method according to claim 1 , wherein the material in particulate form that is deposited in step c) to form the surface protective coating has a particle size between 5 and 40 μm.

9. The method according to claim 1 , wherein the deposition step b) comprises two or more distinct deposition passages of chromium carbide (Cr3C2) and nickel-chromium (NiCr) on the same surface to form the base protective coating.

10. The method according to claim 9 , wherein the deposition step b) comprises a first deposition passage of chromium carbide (Cr3C2) and nickel-chromium (NiCr) in particulate form to create a first base protective layer directly on the disc and a second deposition passage of chromium carbide (Cr3C2) and nickel-chromium (NiCr) in particulate form to create a second layer over the first layer, the chromium carbide (Cr3C2) and nickel-chromium (NiCr) deposited with the first deposition passage having a particle size greater than that deposited with the second deposition pass.

11. The method according to claim 10 , wherein the chromium carbide (Cr3C2) and nickel-chromium (NiCr) deposited with the first deposition passage have a particle size between 30 and 40 μm, while the chromium carbide (Cr3C2) and nickel-chromium (NiCr) deposited with the second deposition passage have a particle size of between 5 and 20 μm.

12. The method according to claim 1 , wherein the braking band is made of grey cast iron.

13. A brake disc for a disc brake, comprising a braking band, provided with two mutually opposite braking surfaces, each of which defines at least partially one of the two main faces of the disc, the braking band being made of aluminium or aluminium alloy, or being made of grey cast iron or steel;

said disc being provided with:

a base protective coating that covers at least one of the two braking surfaces of the braking band, said base protective coating consisting of chromium carbide (Cr3C2) and nickel-chromium (NiCr) and being obtained by depositing, directly on the disc, chromium carbide (Cr3C2) and nickel-chromium (NiCr) in particulate form with HVOF (High Velocity Oxygen Fuel) technique, HVAF (High Velocity Air Fuel) technique or KM (Kinetic Metallisation) technique; and

a surface protective coating that covers at least one of the two braking surfaces of the braking band, said surface protective coating consisting of tungsten carbide (WC) and cobalt (Co) and being obtained by depositing, on the base protective coating, tungsten carbide (WC) and cobalt (Co) in particulate form with HVOF (High Velocity Oxygen Fuel) technique, HVAF (High Velocity Air Fuel) technique or KM (Kinetic Metallisation) technique.

14. The disc according to claim 13 , wherein the base protective coating is constituted by 65% to 95% of chromium carbide (Cr3C2) and the remaining by nickel-chromium (NiCr).

15. The disc according to claim 13 , wherein the surface protective coating is constituted by 80% to 90% by weight of tungsten carbide (WC) and the remaining by cobalt (Co).

16. The disc according to claim 13 , wherein the base protective coating ( 30 ) has a thickness between 20 μm and 60 μm.

17. The disc according to claim 13 , wherein surface protective coating has a thickness between 30 μm 70 μm.

18. The disc according to claim 13 , wherein the braking band is made of grey cast iron.