1. Selection and pretreatment of silicon carbide
(1) Selection of particle type
Particle size: Select different mesh sizes (usually 200 mesh to 2000 mesh) according to wear resistance requirements:
Coarse particles (50~200μm): used in high impact wear scenarios (such as mining equipment coatings).
Fine particles (1~50μm): used for fine wear-resistant layers (such as precision mechanical seals).
Nanoscale (<1μm): improves the density and surface finish of the composite material.
Morphology:
Angular particles: enhance mechanical interlocking and increase friction coefficient.
Spherical particles: improve fluidity and reduce adhesive internal stress.
(2) Surface modification
To improve compatibility with the adhesive matrix, SiC needs to be surface treated:
Silane coupling agent treatment (such as KH-550, KH-560): Enhance the interfacial bonding strength with organic adhesives such as epoxy resin and polyurethane.
Acid washing/alkali washing: Remove surface oxides and improve activity.
Plasma treatment: Suitable for high-performance nanocomposites.
2. Addition method and formula design
(1) Direct mixing method
Steps: Mix SiC particles and adhesive matrix (such as epoxy resin, polyurethane) evenly by mechanical stirring or ultrasonic dispersion.
Addition ratio:
Low load (5%~15%): Maintain the flexibility of the adhesive, suitable for thin coatings.
High load (30%~60%): Significantly improve wear resistance, but toughening agents (such as rubber particles) are required to prevent brittle cracking.
(2) Gradient distribution design
Multilayer coating: first apply a high SiC content layer (wear resistance) on the substrate surface, then apply a low content layer (toughening).
Centrifugal sedimentation: Use centrifugal force to enrich SiC on the surface before curing (suitable for thick coatings).
(3) Composite reinforcement system
Cooperation with other fillers:
SiC + graphite: Reduce friction coefficient, suitable for self-lubricating coatings.
SiC + carbon fiber: Improve impact resistance and thermal conductivity.
3. Curing process optimization
Temperature control:
Epoxy resin system: Curing at 80~150℃ can reduce SiC sedimentation.
Polyurethane system: Room temperature curing requires extended stirring time to prevent particle agglomeration.
Pressure assistance: Hot pressing (such as 5~10MPa) can increase SiC filling density.
4. Application scenarios and typical cases
(1) Industrial wear-resistant coating
Transportation pipeline lining: Adding 40% SiC epoxy adhesive can increase wear resistance life by 3~5 times.
Mining machinery: Polyurethane/SiC composite coating (50% load) has excellent resistance to sand and gravel wear.
(2) Aerospace sealant
Nano-SiC (10%~20%) modified silicone rubber is resistant to high temperature (600℃) and wear.
(3) Automotive brake adhesive
SiC is blended with aramid fiber and used for brake pad backing to reduce thermal decay.
5. Common problems and solutions
Problem 1: Particle sedimentation
Solution: Add gas-phase SiO₂ or cellulose thickener, or use a thixotropic adhesive matrix.
Problem 2: Weak interface bonding
Solution: Use coupling agent treatment or in-situ polymerization to coat SiC.
Problem 3: Increased viscosity
Solution: Optimize particle size grading (mixed coarse + fine particles), or add diluent.
Summary
The core value of silicon carbide in wear-resistant adhesives lies in its hardness (Mohs 9.2) and thermal stability (＞1600℃). By rationally selecting particle parameters, surface modification and process design, the wear resistance, thermal conductivity and mechanical strength of the adhesive can be significantly improved, making it suitable for extreme working conditions such as heavy loads and high temperatures. In practical applications, it is necessary to balance wear resistance and matrix toughness to avoid cracking caused by overfilling.