Brake disc and manufacturing method thereof

1. A brake disc that stops rotation of an axle when a brake pad is pressed on a surface of the brake disc, comprising:

a disc main body that is attached to a rotary body integrally rotating with the axle;

a plurality of build-up layers laminated on a surface of the disc main body; and

the disc main body being made of steel,

wherein the build-up layers are laminated on the surface of the disc main body by means of laser metal deposition welding,

the build-up layer is constituted of a laminate formed of two or more layers of a predetermined matrix laminated on the surface of the disc main body,

the laminate includes an inner layer which is laminated on the disc main body and does not include high-melting-point metal particles having a higher melting point than the disc main body and an outer layer which is formed on the inner layer and includes the high-melting-point metal particles,

the outer layer of the build-up layer includes ceramic particles, and

a molten amount into the build-up layer from the disc main body is <5%.

2. The brake disc according to claim 1 ,

wherein the high-melting-point metal particles include molybdenum, tungsten, niobium, or tantalum, or a combination thereof.

3. The brake disc according to claim 2 ,

wherein an amount of the ceramic particles in the outer layer is higher than 0% and lower than or equal to 50% in terms of % by mass.

4. The brake disc according to claim 1 ,

wherein an amount of the ceramic particles in the outer layer is higher than 0% and lower than or equal to 50% in terms of % by mass.

5. A manufacturing method of a brake disc that stops rotation of an axle when a brake pad is pressed on a surface of the brake disc, comprising:

a build-up layer-forming step of forming a build-up layer on a surface of a disc main body that is attached to a rotary body integrally rotating with the axle by means of laser metal deposition welding, the disc main body being made of steel,

wherein the build-up layer-forming step includes

a first step of forming an inner layer of the build-up layer on the surface of the brake main body by radiating laser beams on the surface of the disc main body and supplying a first metal powder to a position irradiated with the laser beams so as to melt the first metal powder; and

a second step of forming an outer layer of the build-up layer on a surface of the inner layer by radiating laser beams on the surface of the inner layer and supplying a second metal powder to a position irradiated with the laser beams so as to melt the second metal powder,

wherein the first metal powder is particles of a matrix which does not include high-melting-point metal particles having a higher melting point than the disc main body, and

the second metal powder is a powder mixture of the particles of the matrix and the high-melting-point metal particles.

6. The manufacturing method of a brake disc according to claim 5 ,

wherein the high-melting-point metal particles include molybdenum, tungsten, niobium, or tantalum, or a combination thereof.

7. The manufacturing method of a brake disc according to claim 6 ,

wherein the second metal powder is a powder mixture of the particles of the matrix, the high-melting-point metal particles, and ceramic particles; and

an amount of the ceramic particles in the second metal powder is higher than 0% and lower than or equal to 50% in terms of % by mass.

8. The manufacturing method of a brake disc according to claim 5 ,

wherein the second metal powder is a powder mixture of the particles of the matrix, the high-melting-point metal particles, and ceramic particles; and

an amount of the ceramic particles in the second metal powder is higher than 0% and lower than or equal to 50% in terms of % by mass.