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Nitriding steels are substantially similar to the hardening and tempering steels having a particular chemical composition, their are alloyed with particular elements like: aluminum, molybdenum, vanadium and chrome.The peculiar affinity with nitrogen allows easily the production of nitride with very high hardness.
These peculiar steel qualities are used in the nitriding thermochemical treatments to be performed on items previously hardened and tempered to harden the surfaces increasing the wear resistance, both abrasive and adhesive, and a significant increase of fatigue limit.
For the above mentioned reasons and considering the limited deformations after the treatment, those steels are preferred to the casehardening steels.
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SYNTHESIS OF CHARACTERISTICS OF HARDENED & TEMPERED AND NITRIDED STEELS
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 Excellent cleanness of surfaces after nitriding treatment.
Possibility of use items after the treatment without other treatments.
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Increased harness of the surfaces (750 ÷ 1200 Hv).
Constant hardness with heat up to 500 °C.
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Reduced dimension variation (swelling from 0.001 mm to 0.03 mm).
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Resistance improvement to corrosion in low aggressive environments.
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| Nitriding steels acknowledged by UNI norms are the following: |
- 31CrMo12
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There are also, although in limited number, other steels used in the nitriding treatment like (according DIN 17211 norm):
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- 31CrMo12 |
(W nr. 1.8515) |
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- 31CrMoV12
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- 31CrMoV9 |
(W nr. 1.8519) |
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- 34CrMoV7
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- 15CrMoV5.9 |
(W nr. 1.8521) |
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- 41CrAIMo7
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- 34CrAlMo5 |
(W nr. 1.8507) |
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- 34CrAlNi7 |
(W nr. 1.8550) |
In the following pages, the typical aspects of these steels (like chemical analysis, mechanical characteristics etc..) are illustrated:
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