Original language | English |
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Title of host publication | Encyclopedia of Materials: Metals and Alloys |
Editors | Francisca G. Caballero |
Publisher | Elsevier |
Publication date | 2022 |
Pages | 173-189 |
ISBN (Electronic) | 978-0-12-819733-2 |
DOIs | |
Publication status | Published - 2022 |
Abstract
Nitriding is among the most versatile thermochemical surface
engineering treatments of steels and is widely applied to improve the
performance of steel components with respect to fatigue, wear and
corrosion. The deliberate introduction of nitrogen to steels dates back
to the early 1900s, where it was discovered that steels applied in the
ammonia synthesis suffered from embrittlement
due to the ingress of nitrogen, which is an undesired corrosion
phenomenon. This gave the inspiration for the deliberate and controlled
introduction of nitrogen as an alloying element. The strengthening
mechanisms on which nitriding relies, are solid solution strengthening
by interstitially dissolved elements, precipitation strengthening by
alloying element nitrides,
and the formation of interstitial surface compounds (iron-based
nitrides). There exists a wide range of commercial processes to
introduce nitrogen into steels, including many variants of gas, plasma
and salt-bath based processes. This article will not elucidate the
various processing routes, but rather focus on the mechanisms by which
nitrogen in steels contributes to the improvement of their performance.
As a thermodynamics reference for the dissolution of nitrogen in steels,
equilibrium reactions with nitrogen-providing gas molecules are given.
This article is subdivided in nitriding treatments for low-alloyed
steels and for stainless steels.