Nitriding is a surface-hardening heat treatment that diffuses nitrogen into the outer layer of a steel or alloy part while it is held at a moderate temperature, well below the metal's melting or even hardening-transformation point, forming hard nitride compounds within that surface layer without requiring the rapid quenching that carbon-based case hardening methods need. The German metallurgist Adolph Fry developed the modern gas nitriding process in the early 1920s while working for the Krupp steelworks, discovering that certain alloy steels containing aluminum, chromium or molybdenum formed an especially hard nitrided layer. Because nitriding causes little distortion compared to quench-hardening methods, it became particularly valued for precision components such as gears, crankshafts and gun barrels that must hold a hardened surface while keeping tight dimensional tolerances, and it remains a standard heat-treatment option in modern metallurgical engineering.
Facts
Partially Attested
YearYear is Adolph Fry's European process patent at Krupp. The same source dates Machlet's earlier process patent to 1908, and Wikipedia says systematic investigation began in the 1920s, so the origin year is not settled. SignificanceCase-hardens metal surfaces, mostly low-alloy steels, for parts such as gears, crankshafts, camshafts, cam followers and valve parts. 1 FAQs
How far below a steel's tempering temperature is nitriding done?
Roughly 50 to 70 degrees Fahrenheit below the steel's prior tempering temperature.
One process guide says the nitriding temperature for a steel should be chosen below the temperature at which the steel was previously tempered, by roughly 50 to 70 degrees Fahrenheit.
What is the white layer on a nitrided part?
It is the compound layer at the surface of the nitrided case.
The white layer is the compound layer at the very surface of a nitrided case. It gets its name because the surface etches out white when a cross section of the case is examined.
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Source Wikipedia: Nitriding
Sources
1. Wikipedia: Nitriding
Lead section, paragraph 2
Typical applications include gears, crankshafts, camshafts, cam followers, valve parts
In Field: Metallurgical Engineering, Categories
Metal heat treatments
In Group: Steel Hardening and Surface Treatment, Introduction
Nitriding is a heat treating process that diffuses nitrogen into the surface of a metal to create a case-hardened surface.
View the Source2. The Monty: Nitriding, Process Methods and Metallurgy
Paragraph 3Quote, Paragraph 3
was granted a European process patent in 1923
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