Case Hardening
Case hardening creates a hard, wear-resistant surface layer on steel while keeping a tough, ductile core, usually by carburising low-carbon steel, then quenching and tempering. It is ideal for gears, shafts, pins and cams that face wear and shock.
What it is
In carburising, parts are heated in a carbon-rich atmosphere so carbon diffuses into the surface, then quenched to harden that high-carbon case. Carbonitriding adds nitrogen for shallower cases on smaller parts.
Typical case depths are 0.3–2 mm with surface hardness around 58–62 HRC, while the core stays tougher.
Typical applications
- Gears and pinions
- Camshafts and cam followers
- Pins, bushes and rollers
- Transmission shafts
- Chain and sprocket parts
Suitable materials
- EN36, 20MnCr5, 16MnCr5, 8620
- EN1A / mild steel (light duty)
- EN353, EN354
Points to consider
- Use case-hardening steel grades for good core properties.
- Specify effective case depth and surface/core hardness.
- Areas to stay soft (for later machining) can be masked with copper plating or paint.
- Grind after hardening for precision features; leave allowance.
Frequently asked questions
What is case hardening?
Hardening only the surface layer of steel, typically by carburising, leaving a tough core.
How deep is case hardening?
Typically 0.3–2 mm, specified as effective case depth to a defined hardness.
Can some areas be left soft?
Yes. Areas can be masked, for example with copper plating, so they stay machinable after hardening.