Vacuum Sintering Process for SiC (Silicon Carbide)

I. Process Principle

SiC vacuum pressureless sintering is conducted under vacuum conditions without the application of external pressure. Densification is achieved through high temperatures (1950–2200°C) combined with sintering aids, utilizing either solid-phase diffusion (B/C system) or liquid-phase sintering (Al₂O₃-Y₂O₃ system). This process allows for the attainment of a relative density of ≥98%.

II. Process Parameters

1) Solid-Phase Sintering (B₄C + C; High Thermal Conductivity / High Purity)

• SiC: 98.5–99% (Sub-micron β-SiC, 0.4–0.8 μm)
• B₄C: 0.5% (Sintering aid; grain refinement)
• C: 1.0% (Reduction of SiO₂; oxidation prevention)

III. Process Flow

1. Raw Material Pre-treatment

• Ball Milling: SiC powder + sintering aids + ethanol; 24–48 hours
• Drying: Rotary evaporation + Oven drying
• Sieving: 200–325 mesh; removal of agglomerates

2. Forming

• Dry Pressing: 50–100 MPa
• Cold Isostatic Pressing (Optional): 200–300 MPa; improves uniformity

3. Debinding (Binder Removal)

• Vacuum Level: ≤10⁻¹ Pa
• Heating Profile: Room Temperature → 600°C (2°C/min), hold for 1–2 hours
• 600°C → 1200°C (5°C/min), hold for 1 hour

4. Vacuum Sintering

• Vacuum Level: ≤10⁻² Pa
• Temperature: Typically heated to 2050°C and held for 1–2 hours
• Furnace Cooling: (≤5°C/min; prevents cracking)

5. Post-processing

• Grinding / Polishing: Surface roughness Ra 0.1–0.5 μm
• Cleaning: Ultrasonic cleaning + Alcohol; drying

Ⅳ. Process Advantages

• Oxidation-Free: A vacuum environment prevents oxidation, ensuring purity and hardness.
• Thorough Dewaxing: Achieved through vacuum extraction combined with high-temperature vaporization, resulting in residual wax levels of less than 0.01%.
• High Density: Attains 98–99.5% of theoretical density, offering exceptional strength and wear resistance.
• Eco-Friendly: Wax vapor is condensed and recovered, resulting in zero exhaust emissions.

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SIMUWU specializes in the manufacture of vacuum furnaces, possessing over ten years of relevant experience and enjoying a good reputation in the vacuum furnace manufacturing field. Our product line includes vacuum gas quenching furnaces, vacuum oil quenching furnaces, vacuum brazing furnaces, and vacuum sintering furnaces, which are widely sold to developed and developing countries.

If you would like to learn more about vacuum furnace equipment, please send your requirements to kevin.liu@vacfurnace.com, and we will provide you with a satisfactory solution.