34 00... Reference sample catalog for assessing visual quality of carbon ceramic brake discs in new condition

Structure of a carbon ceramic brake disc:

Ceramic friction layer
Carbon carrier body
Coolant duct

In order to guarantee the long service life of the ceramic brake disc, the carrier body is coated with a separate friction layer. The friction layer is glued on by means of a special joining paste. In siliconization, firm bonding is the result.

The carrier body and the friction layer are based on different mixtures/formulas. Consequently, there are also differences in the visual appearance of the two components.

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Relaxation structure:

Due to the different material composition of friction layer and carrier body, the friction surfaces are covered with a noncritical relaxation structure (even in new condition). Individual relaxation cracks sometimes line the perforation bores.

The relaxation structure emerges in production outgoing from the brake disc surface and does not present a safety hazard. Neither is there any risk of large-scale chipping of the friction layers from the carrier body because thanks to the relaxation structure, the friction layers are almost free of residual stress.

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The relaxation structure is sometimes clearly visible in new condition and can be significantly different on side of the brake disc chamber and the opposite side.

Thus, the brake disc is OK

Rough surfaces in the coolant duct:

The surfaces (1) in the coolant duct have a different structure. The coolant ducts are not machined and have a rough structure because of this.

Thus, the brake disc is OK

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Traces of machining:

The surface of the ceramic brake disc reflects the way is which it was ground. The cross or spiral pattern (see arrows in illustration) generated depending on the type of the grinding process has no influence of the performance of the component.

Thus, the brake disc is OK

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Pores in the carrier body:

Due to the carbon fibers used at a defined length of 10 mm without short-fiber share, visible pores are created in the carrier body during the production process. These pores have no negative influence on the function of the carbon ceramic brake disc.

E.g

Pores at the screw connection of the brake disc chamber
Pores on the rim surface of the brake disc

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Possible surface defects on the brake disc:

Defects at perforation bores

Brake disc OK
Brake disc not OK -> clustered chippings

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Brake disc not OK

-> Clustered chippings (3 or more bores on each side)

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Nature	Perforation bore with edge chippings
Remarks	Edges expanded by edge chippings
Compliance criterion	No chipped edges at perforation bore Chippings are still permissible if they: Do not extend > 3 mm from the edge of the bore End within the friction layer Do not cluster (3 or more adjacent bores)
Maximum number	20 affected bores on each side
Assessment	OK if criteria are complied with
Measures	If not OK, do not install component

Defects in the friction layer:

Friction layer chipping:

Illustration (A): Brake disc OK

Illustration (B): Brake disc not OK

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Nature	Chipping from the friction layer
Remarks	none
Compliance criterion	No chippings Chippings are still permissible if they: End in the friction layer Are not > 2 x 2 mm
Maximum number	1 chipping per side
Assessment	OK if criteria are complied with
Measures	If not OK, do not install component

Separation of friction layer:

Brake disc with separation of friction layer (1) -> brake disc not OK

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Nature	Separation of friction layer
Remarks	Gap between friction layer and carrier body
Compliance criterion	No separation of friction layer permissible
Maximum number	-
Assessment	OK if criteria are complied with
Measures	If not OK, lock component

Friction layer not completely machined:

Brake disc (see illustration), not OK

Nature	Friction layer and edge not completely machined
Remarks	None
Compliance criterion	Complete, uniform machining of the surface
Maximum number	- -
Assessment	OK if criteria are complied with
Measures	If not OK, do not install component

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Chipped edges at the outer diameter of the friction ring:

Brake disc, see illustration, OK

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Brake disc, see illustration, not OK

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Nature	Chipped edges at the outer diameter of the friction ring
Remarks	Irregular outer contour because of material and processing characteristics of the friction layer or Damage due to improper handling of the brake disc
Compliance criterion	No edge damage Damage is still permissible if: Maximum length of damage: 10 mm (x) Maximum width of damage: 3 mm (y) Maximum depth of damage: 3 mm (z)
Maximum number	1 per side
Assessment	OK if criteria are complied with
Measures	If not OK, do not install component

Chipped edge in the area of the ridge:

Brake disc, see illustration, not OK

Nature	Chipped edge in the area of the ridge
Remarks	None
Compliance criterion	No chipped edges Damage is still permissible if: Outside the nut contact surface with an area ≥ 25 mm²
Maximum number	5 connection areas with chipping
Assessment	OK if criteria are complied with
Measures	If not OK, do not install component

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Radial cracks at the inner diameter of the brake disc ring

Brake disc, see illustration, OK

Nature	Radial cracks at the inner diameter of the brake disc ring
Remarks	As a consequence of residual stress in the brake disc ring, radial cracks can emerge
Compliance criterion	Damage is still permissible if: The maximum length of the cracks is up to 10 mm
Maximum number	5 cracks are permissible
Assessment	OK if criteria are complied with
Measures	If not OK, do not install component

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Cracks at the ridge transition:

Brake disc or, respectively, cracks (1) in the ridge area

Brake disc, see illustration, OK

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Brake disc:

Crack (dimension A) in the ridge area > 20 mm depth -> brake disc not OK

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Nature	Cracks in the ridge transition
Remarks	As a consequence of residual stress in the brake disc ring, radial cracks can emerge
Compliance criterion	Damage is still permissible if: Continuous cracks at the ridge ≤ dimension [A] 20 mm depth
Maximum number	Maximum of 10 cracks per component No more than 5 adjacent cracks
Assessment	OK if criteria are complied with
Measures	If not OK, do not install component

Residual phosphate in the coolant duct and perforation bores/contamination at the ZSB

Illustration (A) and (B) -> brake disc not OK

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Brake discs, see illustration, not OK!

Perforation bore
Contamination at the ZSB

Nature	Residual phosphate in the coolant duct or perforation bore
Remarks	Coolant duct: no residual phosphate in the coolant duct or perforation bore: Clear diameter min. 3 mm Restriction circular or sickle-shaped Restriction 2 mm below the surface No contamination at the ZSB
Compliance criterion	Coolant duct: no perforation bore: 20 per side
Maximum number	Maximum of 10 cracks per component No more than 5 adjacent cracks
Assessment	OK if criteria are complied with
Measures	If not OK, do not install component

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