Case Carburizing

Introduction to Case Carburizing

Case carburizing is a widely used surface hardening process that enhances the wear resistance and fatigue strength of steel components. It involves enriching the surface of low-carbon steel with carbon, creating a hard outer layer while maintaining a tough and ductile core. This combination of properties makes case carburized parts ideal for applications requiring high durability and strength.

The Case Carburizing Process

The case carburizing process consists of several key steps:

1. Preparation and Heating

The steel components are cleaned and placed in a controlled atmosphere furnace, where they are heated to temperatures ranging from 850°C to 950°C. This temperature range allows the steel's atomic structure to become receptive to carbon diffusion

2. Carbon Diffusion

A carbon-rich environment is introduced using gases like methane (CH4) or propane (C3H8), or solid carburizing compounds such as charcoal. The carbon atoms diffuse into the surface of the steel, increasing its hardness.

3. Soaking Time Control

The duration of the carburizing stage determines the depth of the hardened layer (also known as the case depth), which can range from 0.1 mm to 3 mm, depending on application requirements.

4. Quenching

After carburization, the components are rapidly cooled (quenched) in oil, water, or gas. This process locks the carbon into the steel structure, forming a hard martensitic surface while preserving the tough inner core

5. Tempering

To relieve internal stresses and improve toughness, the parts undergo a tempering process, which slightly reduces hardness but enhances overall durability.

Benefits of Case Carburizing

• Increased Surface Hardness

The carburized layer significantly improves wear resistance, making the component more durable in high-friction environments.

• Enhanced Fatigue Strength

The tough core combined with a hard surface improves the component's ability to withstand cyclic loading.

• Superior Wear and Impact Resistance

The process allows manufacturers to tailor the hardness depth based on application needs.

• Cost-Effective Process

Carburizing enhances the performance of low-cost steels, reducing the need for expensive alloyed materials.