Ferritic nitrocarburizing
This allows for better control of the dimensional stability that would not be present in case hardening processes that occur when the alloy is transitioned into the austenitic phase.
[2] There are four main classes of ferritic nitrocarburizing: gaseous, salt bath, ion or plasma, and fluidized-bed.
ICI called their process "the cassel" due to the plant where it was developed[5][6] or "Sulfinuz" treatment because it had sulfur in the salt bath.
[7] Because of the cleaning issues, Lucas Industries began experimenting with gaseous forms of ferritic nitrocarburizing in the late 1950s.
[8] This innovation spurred the development of a more environmentally friendly salt bath process by the German company Degussa after acquiring ICI patents.
The shared attribute of this class of this process is the introduction of nitrogen and carbon in the ferritic state of the material.
The processes are divided into four main classes: gaseous, salt bath, ion or plasma, or fluidized-bed.
The trade name and patented processes may vary slightly from the general description, but they are all a form of ferritic nitrocarburizing.
The compound layer consists of iron, nitrogen, and oxygen is abrasion resistant and is stable at elevated temperatures.
[20][21][22][23] In this technique intense electric fields are used to generate ionized molecules of the gas around the surface to diffuse the nitrogen and carbon into the workpiece.
The gas used for plasma nitriding is usually pure nitrogen since no spontaneous decomposition is needed (as is the case of gaseous ferritic nitrocarburizing with ammonia).
Due to the relatively low-temperature range (420 °C (788 °F) to 580 °C (1,076 °F)) generally applied during plasma-assisted ferritic nitrocarburizing and gentle cooling in the furnace, the distortion of workpieces can be minimized.
Stainless steel workpieces can be processed at moderate temperatures (like 420 °C (788 °F)) without the formation of chromium nitride precipitates and hence maintaining their corrosion resistance properties.
Typical applications include spindles, cams, gears, dies, hydraulic piston rods, and powdered metal components.
Pistol manufacturer Caracal International, headquartered in the United Arab Emirates, uses ferritic nitrocarburizing for finishing parts such as barrels and slides with the plasma-based post-oxidation process (PlasOx).
