Gas Carburising Process

The rate of diffusion is dependent on the alloy and carbon potential of the atmosphere. Care must be taken to ensure that only sufficient carbon is available in the atmosphere at any one time to satisfy the take up rate of the alloy to accept the carbon atoms.

In practice, this is defined in a carbon potential setpoint profile which runs concurrently with the temperature cycle. The setpoint may give a boost phase where the carbon potential would be typically set above 1.0% carbon but, as the cycle progresses and the effective case depth increases, the carbon setpoint will be reduced to complete the diffusion stage.

Depending on the final requirement for effective case depth, the whole cycle may take many hours.

Once the heating and carbon diffusion part of the process are complete it is necessary to rapidly quench the components to a defined alloy recipe. The recipe will specify the quench method, the quenchant temperature and time.