Nitriding
Nitriding diffuses nitrogen into the steel surface at relatively low temperature (around 500–570 °C), forming a very hard, wear- and fatigue-resistant layer with minimal distortion. Gas, plasma and salt-bath nitriding are used for dies, gears, crankshafts and precision parts.
What it is
Because nitriding happens below the steel's tempering temperature and needs no quench, parts keep their shape and dimensions, often finish-machined beforehand. The hard layer is thin (typically 0.1–0.6 mm diffusion zone) but very hard.
Nitrocarburising (for example salt-bath or gas processes) adds carbon and gives a shallow, wear- and corrosion-resistant compound layer, popular on shafts and hydraulic parts.
Typical applications
- Plastic moulds and extrusion dies
- Crankshafts and gears
- Hydraulic rods and pistons
- Screw and barrel parts
- Precision machine components
Suitable materials
- Nitriding steels (EN41B)
- Alloy steels (EN19, EN24, 42CrMo4)
- Tool steels (H13, D2)
- Stainless steels (special processes)
Points to consider
- Pre-harden and temper alloy steels above the nitriding temperature for a strong core.
- Finish machine before nitriding; only light polishing afterwards.
- Plain carbon steels give low hardness; use alloy steels with Cr, Mo, Al.
- Mask areas that must stay soft.
Frequently asked questions
Why choose nitriding over case hardening?
Nitriding causes very little distortion because it runs at low temperature with no quench, so finish-machined parts keep their size.
How hard is a nitrided surface?
Typically around 600–1,100 HV depending on the steel's alloying elements.
What is the difference between nitriding and nitrocarburising?
Nitriding diffuses nitrogen for a deeper hard layer; nitrocarburising adds carbon too, forming a thinner wear- and corrosion-resistant compound layer faster.