Mechanical Seal Materials

I. Dynamic/Static Ring Materials (Friction Pair Materials)

Silicon Carbide (SiC)

Features: High hardness, wear resistance, corrosion resistance, good thermal conductivity.

Types: Pressureless sintered (more corrosion-resistant), reaction sintered (lower cost, slightly poorer acid resistance).

Applications: Strongly corrosive media (e.g., acids/alkalis), particle-laden fluids, high-temperature/high-pressure conditions.

Silicon Nitride (Si₃N₄)

Features: Excellent thermal shock resistance, high-temperature tolerance (up to 1200°C), but weak resistance to strong acids/alkalis.

Applications: High-temperature and high-speed scenarios (e.g., aviation, automotive cooling pumps).

Aluminum Oxide Ceramic (Al₂O₃)

Features: High hardness, corrosion resistance, but brittle with poor impact resistance.

Applications: Clean water, weak corrosive media, low-cost general conditions.

Hard Alloy (e.g., WCCo)

Features: High wear resistance, but weak against strong acids.

Applications: Particle-laden media (e.g., slurry pumps), petroleum industry.

Stainless Steel (e.g., 304/316)

Applications: Low-corrosion media, economical seals.

Carbon Graphite (Impregnated)

Impregnation Types: Resin-impregnated (acid-resistant), metal-impregnated (good thermal conductivity).

Applications: Clean water, oils; often paired with hard materials.

II. Auxiliary Sealing Materials (Elastic Elements)

Rubber Types

Nitrile Butadiene Rubber (NBR): Good oil resistance, temperature range -30~120°C (e.g., oil pumps).

Fluororubber (FKM): High-temperature resistance (200°C), oil/solvent resistance (chemical pumps).

Ethylene-Propylene-Diene Monomer (EPDM): Steam and weak acid/alkali resistance, poor hydrocarbon resistance (hot water pumps).

Perfluoroelastomer (FFKM): Extreme corrosive media (strong acids, oxidants).

Polytetrafluoroethylene (PTFE)

Features: Strong corrosion resistance, high-temperature tolerance (260°C), but poor elasticity (requires spring support).

Applications: Concentrated sulfuric acid, hydrofluoric acid, and other strong corrosive media.

III. Materials for Other Key Components

Metal Bellows

Materials: Stainless steel (304/316), Hastelloy (C276), titanium alloy.

Applications: High-temperature and highly corrosive media (e.g., petrochemical industry).

Springs

Materials: Stainless steel (302/316), Hastelloy.

Requirements: Fatigue resistance, medium corrosion resistance.

Gaskets/Seals

Materials: Flexible graphite (high-temperature resistant), PTFE (corrosion-resistant).

IV. Material Selection Considerations

Medium Compatibility: Use PTFE or silicon carbide for hydrofluoric acid; avoid copper alloys for ammonia.

Temperature Limits: Rubber materials have upper temperature limits (e.g., NBR ages above 120°C).

Cost Balance: Silicon carbide offers superior performance but higher cost; ceramic or carbon graphite is suitable for general conditions.

Pairing Principles:

Hard-soft pairing (e.g., SiC vs. carbon graphite) reduces wear.

Hard-hard pairing (SiC/SiC) suits high-speed and high-pressure applications.