Parts are heated 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. Parts are then quenched in oil to harden and then tempered. Case Depths are generally less than .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 a 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, it is necessary to use a steel with higher alloy content.
- Lower temperatures are used for carbonitriding than carburizing as the ammonia addition will break down too quickly at higher temperatures. This will result 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)
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