what is gas nitriding?
Gas nitriding is a low temperature furnace treatment with an atmosphere of Ammonia. The nitriding process is an established and successful means of generating a hard case on a component. The aim of the process is to create a certain level of protection against corrosion and to protect the material from wear. In addition, the strength of the material can be improved in this way.
Nitriding is another form of surface hardening of steels. It is a thermochemical process in a nitrogen-releasing environment. In this atmosphere the material is heated to a temperature between 475 and 550°C. The material is then held at this temperature for a certain time. This time can vary from a few minutes up to 120 hours. Eventually, the material is cooled down.
The desired hardness is created by the transfer of nitrides into the metal mesh. Different degrees of hardness can be achieved depending on the element used.
The characteristics of the process are:
- Low temperature between 475°C to 550°
- Flexibly applied – process duration modified according to the specification of the required final component properties.
- Environmentally friendly compared to serious alternatives (e.g. chrome plating).
- Clean for the component –g. leaving no heavy surface contaminant or residue.
fields of application
The process is usually performed on fully finished components which, in many instances, require no additional operations prior to assembly.
Usually nitriding is only used on alloy steel. These have a carbon content of 0.3 to 0.4%. It is possible to nitride other materials such as stainless steel, titanium and nickel alloys, however the preferred nitriding route for those materials is Plasma Nitriding.
The resulting layer is relatively thin, so that changes in shape cannot be changed afterwards by grinding. However, the changes in shape during nitriding are comparatively very small. Stress relieving should be carried out beforehand. In this way it can be achieved that the material is free from stresses, which in turn reduces the risk of shape changes.
This process is most useful for components such as Crankshafts, Gears and a multitude of other parts in tough environments (especially oil & gas, energy, aerospace, etc).
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