Carbonitriding is a thermo-chemical process. Within the framework of this process, the surface layer of components is enriched with carbon and nitrogen, in order to improve the mechanical properties of the component surface layer. For this process, there are various furnace technologies, such as chamber furnaces and continuous furnaces.
As a rule, carbonitriding comprises three working steps. In the first step, the workpieces are exposed to a carbon and nitrogen rich environment at a temperature of 750 to 900 °C. In the second step, the quenching takes place after the workpiece was exposed to the target temperature for a certain time. The third step, the tempering treatment serves essentially to relieve the highest stresses in the material structure and to reduce sensitivity to grinding cracks.
fields of application
Carbonitriding results in a very hard case of the component. Specifically, this is useful in the case hardening of gears and similar components which are subject to a great deal of wear in hostile environments. This heat treatment process is especially useful if there is a requirement for a hard, wear resistant surface, overlying a much softer and tougher core. A good example for its application is a gear wheel. The surface of the teeth needs to be extremely hard so that they can withstand constant metal-to-metal contact, without undue wear. The underlying material needs to be tough so that the teeth can tolerate occasional impact loads, without the risk of fracture.
Carbonitriding is used to give a hard case onto the cheapest steels which are often not capable of being case hardened because of their chemical composition. The carbonitriding process is applied to low carbon and mild steels and results in less distortion than traditional carburizing techniques.