Carbonitriding is a process in which nitrogen and carbon are diffused into a steel part at elevated temperatures and then quenched to form a hard outer surface layer. This treatment gives steel components beneficial properties, such as increased wear resistance, durability, and ductility, which in turn leads to longer lifespans even in contaminated environments.
Common Alloys treated through carbonitriding
- Low Carbon Carbon Steels, e.g., 1018, 1020, 12L14
- Low Carbon Structural Steels, e.g., A36, A572
- Low Carbon Alloy Steels, e.g., 8620, 4130
We heat steel parts in a protective endothermic atmosphere to above the critical point of steel. Controlled amounts of methane and ammonia are introduced and allowed to diffuse into the part for a determined amount of time. The parts are subsequently quenched in oil to harden and then tempered. The resulting case depths are generally less than 0.030 inches.
- Carbonitriding is frequently used on low-carbon steels that need to have a hard outer surface. Due to the low carbon content of the steel, traditional quench and temper processing will not produce that required hard surface. The diffusion of carbon into the steel allows for maximum surface hardness in excess of 60 HRC. The nitrogen diffusion is critical for low-alloy steels as it increases the hardenability of the surface layer.
- Carbonitriding is used over carburizing in applications where a low-alloy steel is preferred, generally for economical reasons. If increased core strength is required however, then steels with higher alloy contents are necessary. For more information, check out carburizing.
- In carbonitriding, we utilize lower temperatures than used in carburizing, as the ammonia addition breaks down too quickly at higher temperatures. This results in less distortion, but requires longer cycle times to reach the same case depths.
- Carbonitriding should not be confused with nitrocarburizing, which is a lower temperature process based on nitriding. See Plasma Nitriding for more information.
- AMS 2762
What To Consider When Specifying
- Case Depth
- Spec (if required)
- Masking (if required)