1. Core Function and Mechanism
Stabilize the Friction Coefficient
Micro-cutting Effect: Brown corundum particles (Mohs hardness ≥ 9) are embedded in the surface of the dual disc (brake disc) during braking, forming micro-grooves, increasing the surface roughness, avoiding “slipping” caused by the smooth surface in the early stage of braking, and making the friction coefficient more stable (maintained in the range of 0.35-0.45).
Anti-“stick-slip” phenomenon: angular particles destroy the adhesion layer between the brake pad and the brake disc, suppressing low-frequency braking noise (such as “squeaking”).
Improve wear resistance and life
Skeleton support function: As the hard skeleton of the friction layer of the brake pad, it bears more than 60% of the mechanical shear force, reduces the wear rate of soft components such as resin and graphite, and extends the service life by about 20-30%.
High temperature wear resistance: Maintain structural stability at a braking temperature of 300-600℃ (melting point 2050℃), and prevent aggravated wear caused by high temperature softening.
Optimize thermal management performance
Thermal bridge function: The thermal conductivity (~30 W/m·K) is more than 10 times higher than that of the resin matrix, which accelerates the conduction of friction heat to the back plate, reduces the surface temperature by 100–150℃, and avoids thermal decay (prevents brake failure).
Thermal expansion matching: Cooperates with metal fibers and ceramic fibers to suppress the high-temperature volume expansion of brake pads and maintain the stability of brake clearance.
2. Technical details in practical applications
Parameters Typical values/requirements Impact on performance
Addition ratio 5–15 wt% Too low → unstable friction; too high → damage to brake discs
Particle size distribution 80–200 mesh (dominant) Coarse particles (80 mesh) enhance cutting, fine particles (200 mesh) reduce noise
Particle shape Multi-angular (non-spherical) Enhance mechanical engagement and improve braking response speed
High temperature residual strength >90% (800℃ test) Ensure structural integrity under extreme braking
3. Performance comparison with other friction materials
Material type Advantages Limitations Applicable scenarios
Brown corundum High hardness, low cost, good thermal stability May increase brake disc wear Main material for medium and heavy vehicles, commercial vehicles
Zirconium silicate Low wear, good noise reduction High unit price (2–3 times that of brown corundum) High-end cars, occasions with high requirements for quietness
Alumina ceramic fiber Excellent resistance to thermal decay High brittleness, easy to produce hard spots Racing cars, frequent braking at high temperatures
IV. Industry application trends and challenges
Development trends:
Compound formula: compounded with ceramic fibers and potassium titanate whiskers, taking into account both noise reduction and thermal decay resistance (such as Bosch ECO series).
Surface modification: Silane coating covers brown corundum particles to reduce scratches on brake discs (wear rate reduced by 15%).
Existing challenges:
Wear balance: Brake disc wear caused by high hardness needs to be controlled by optimizing the particle size ratio (such as increasing the proportion of 200 mesh fine powder).
Environmental pressure: high energy consumption in the manufacturing process, promoting the application of arc furnace waste heat recovery technology (such as Saint-Gobain’s “zero carbon brown corundum” project).
Summary: The core value of brown corundum
Economical: low cost to achieve a balance between friction performance and life, accounting for 8-12% of the brake pad formula cost;
Reliability: ensure the high temperature stability of braking force, adapt to frequent braking scenarios (such as mountain roads, heavy trucks);
Irreplaceability: the micro-cutting mechanism of angular hard particles, there is no better material to completely replace it.
Note: Modern brake pads need to coordinate 20+ components (resin, steel fiber, graphite, etc.), and brown corundum plays a vital role as a “friction skeleton”.