This method is widely used for machine parts subjected to wear and impact, such as gears, crankshafts, camshafts, shafts, bushings, bearings, and precision components.

Principle and Purpose

• • Principle: At temperatures between 880–950°C, the steel transforms into austenite, which allows carbon to diffuse into its crystal structure. Carbon is introduced from a carbon-rich environment (gas, liquid, or solid) and penetrates the surface through diffusion.

  • Purpose:

    • Form a carbon-enriched surface layer that can transform into martensite upon quenching, significantly increasing surface hardness.
    • Maintain a low-carbon, tough core to withstand impact and dynamic loads.

Process Steps

1. Material and Preparation:

   • Use low-carbon steels (e.g., 20Cr, 16MnCr5, 20MnCrTi).
   • Clean the surface thoroughly to ensure uniform diffusion.

2. Carburizing (Diffusion Phase):

   • Heat to 880–950°C for several hours, depending on the desired case depth (commonly 0.3–2.0 mm or more).
   • Carbon diffuses into the surface while the material is in the austenitic phase.

3. Quenching:

   • Rapid cooling in oil, water, or gas converts the high-carbon surface into martensite, achieving hardness of 58–64 HRC.

4. Tempering:

   • Performed at 150–200°C to relieve internal stresses and improve toughness of the hardened layer.

Case Characteristics

Advantages

• Selective hardening with optimal material performance.

• Significantly increases component life in abrasive environments.

• Suitable for complex geometries.

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