Gas nitriding is a thermo chemical process of heating ferrous materials at temperatures 500-520°C, so that the metal surface is exposed to the gaseous environment rich in atomic nitrogen. The time required for the nitriding to be done depends on the required thickness of the layer and the material itself (20-120h for thickness 0,2-0,8mm).
As for the classical gas nitriding, so-called nitriding steels (special steels, used for improvement, containing about 0.35% C and alloy elements that create nitrides: Cr, Al, Mo, V) are the most suitable.
Nitrided layer consists of two parts: the "white zone" on the surface (provides the abrasion resistance) and the "diffusion zone" (increases the fatigue strength of steel and provides resistance to pressure).
Nitriding is applied when objects made of ferrous materials are required to achieve at least one of the following properties:
- High wear resistance;
- Increased fatigue strength at varying dynamic loads (primarily bending and torsion);
- High surface hardness and a certain layer thickness, in order to increase resistance to high local pressure and shock;
- High surface hardness and wear resistance at elevated temperatures.
Nitriding does not require any subsequent thermal treatment. Nitrided surfaces are clean and do not require additional machining. Grinding to max 0.05mm may be performed, in order to remove the layer of brittle “white zone” on the surface of the object). Nitriding is applied to parts which are complex in shape, so that possible deformation is avoided.
Nitriding process takes place in shaft furnaces (workspace dimensions are 900 x 2000 mm and maximum batch weight up to 1000kg).