Nitriding

Typical applications include gears, crankshafts, camshafts, cam followers, valve parts, extruder screws, die-casting tools, forging dies, extrusion dies, firearm components, injectors and plastic mold tools.

This process has existed for nearly a century, though only in the last few decades has there been a concentrated effort to investigate the thermodynamics and kinetics involved.

The thickness and phase constitution of the resulting nitriding layers can be selected and the process optimized for the particular properties required.

[citation needed] Unfortunately, since the salts used are extremely toxic, modern environmental and safety regulation have caused this process to fall out of favor.

In this technique intense electric fields are used to generate ionized molecules of the gas around the surface to be nitrided.

Such highly active gas with ionized molecules is called plasma, naming the technique.

This process was invented by Bernhardt Berghaus of Germany who later settled in Zurich to escape Nazi persecution.

Plasma nitriding is often coupled with a physical vapor deposition (PVD) process and labeled duplex treatment, with enhanced benefits.

Since nitrogen ions are made available by ionization, differently from gas or salt bath, plasma nitriding efficiency does not depend on the temperature.

Minimal amounts of material should be removed post nitriding to preserve the surface hardness.

In 2015, nitriding was used to generate a unique duplex microstructure in an iron-manganese alloy (martensite-austenite, austenite-ferrite), known to be associated with strongly enhanced mechanical properties.