What is the Difference Between Carburizing and Carbonitriding?

Carburizing and carbonitriding are both thermochemical surface hardening treatments used to improve the wear resistance, strength, and fatigue properties of steel components. However, there are some differences between the two processes:

1. Atmosphere: Carburizing involves a carbonaceous environment, while carbonitriding involves a carbonaceous environment with ammonia gas.
2. Hardening: Carburizing is the process of hardening a steel surface using carbon, while carbonitriding is the process of hardening a steel surface using both carbon and nitrogen.
3. Material Suitability: Carburizing is suitable for low carbon mild or low alloy steels, while carbonitriding is suitable for plain, low carbon steels that would not achieve a uniform case hardness in standard gas carburizing.
4. Case Depth and Hardness: Carburizing produces a hard, wear-resistant surface with case depths ranging from 0.010" to 0.200" and surface hardness up to 62 - 64 HRC. Carbonitriding produces a thin, high hardness case that gives the part improved wear resistance, strength, and increased resistance to softening at elevated temperatures.
5. Ammonia Addition: Carbonitriding involves the addition of ammonia to the carburizing atmosphere, which results in supplementary nitrogen diffusion into the component and a higher surface hardness. Carbonitriding is sometimes confused with nitrocarburizing, but they are not the same process.

In summary, carburizing and carbonitriding are both used to harden steel surfaces, but they differ in the atmosphere, hardening elements, material suitability, case depth, and hardness. Carbonitriding is a modified form of carburizing that adds ammonia to the process, resulting in a higher surface hardness and improved wear resistance.

Comparative Table: Carburizing vs Carbonitriding

Carburizing and carbonitriding are two techniques used in differential metal structure hardening. Both processes involve diffusing carbon into the surface of steel to increase its hardness and wear resistance. However, there are some differences between the two methods:

Both carburizing and carbonitriding are used in various industries, such as automobile manufacturing, to improve the hardness and wear resistance of steel components subjected to high fatigue stresses or wear, such as parts for transmissions, car engines, roller and ball bearings, and rock drill parts.