Carburizing, also referred to as Case Hardening, is a heat treatment process that produces a surface which is resistant to wear while maintaining toughness and strength of the core.
This treatment is applied to low carbon steel parts after machining as well as high alloy steel bearings, gears and other components.
Carburizing increases strength and wear resistance by diffusing carbon into the surface of the steel creating a case while retaining a substantially lesser hardness in the core. This treatment is applied to low carbon steels after machining .
Most carburizing is done by heating components in either a pit furnace, or sealed atmosphere furnace and introducing carburizing gases at temperature.
Gas carburizing allows for accurate control of both the process temperature and carburizing atmosphere (carbon potential). Carburizing is a time/temperature process; the carburizing atmosphere is introduced into the furnace for the required time to ensure the correct depth of case.
The carbon potential of the gas can be lowered to permit diffusion, avoiding excess carbon in the surface layer.
Carburizing cannot be done in ferrite phase as it has very low solid solubility for carbon at room temperature. It is done in the Austenite region above 727°C in carbon rich atmosphere.
Types of carburizing:
i. Pack carburizing
ii. Gas carburizing
iii. Liquid carburizing