Carbonitriding is a case hardening treatment in which steel parts are heated in a gas rich in carbon and ammonia, so carbon and nitrogen enter the surface. The parts are then quenched and tempered. It gives a hard, wear-resistant skin, usually 0.1–0.75 mm (0.0039–0.0295 inch) deep, at a lower temperature than carburising, with less distortion. It is used for small parts such as pins, bushes, fasteners and gears.
Quick facts
- Temperature
- About 800–880 °C
- Case depth
- About 0.1–0.75 mm (0.0039–0.0295 inch)
- Surface hardness
- About 58–64 HRC after quenching
- Steels
- Low-carbon and low-alloy steels (EN1A, 15C8, EN353, 16MnCr5)
- Distortion
- Less than carburising
- Usually priced
- Per kg, with a minimum batch charge
Carbonitriding, carburising or nitriding?
| Carbonitriding | Carburising | Nitriding | |
|---|---|---|---|
| Temperature | About 800–880 °C | About 900–950 °C | About 500–570 °C |
| Case depth | Shallow, to about 0.75 mm (0.0295 inch) | Deeper, 0.5–2 mm (0.0197–0.0787 inch) | Shallow |
| Quench needed | Yes | Yes | No |
| Distortion | Low | More | Very low |
| Suits | Small parts | Gears, shafts under heavy load | Finished precision parts |
What to send
- Drawing with case depth, surface and core hardness
- Steel grade
- Areas to keep soft, if any
- Quantity and weight per part
- Hardness test report needed
Need carbonitriding done?
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Questions
- Is carbonitriding the same as nitrocarburising?
- No. Carbonitriding is done hot and followed by quenching; nitrocarburising is a lower-temperature process close to nitriding.
- Which parts suit carbonitriding?
- Small low-carbon steel parts that need a hard skin: pins, bushes, washers, small gears and fasteners.
- Does it change part size?
- Slightly. Leave grinding allowance on precision fits, or ask the workshop what growth to expect.
The figures on this page are typical values for guidance, written by Diemeco from standard engineering practice. They are not a specification: confirm grades and properties with the relevant standard or the supplier's mill test certificate, and tolerances with your workshop. Last checked 29 October 2026.