Carbonitriding is a metallurgical surface modification technique used to increase the surface hardness of a metal and thus reduce wear.
During processing, carbon and nitrogen atoms interstitively diffuse into the metal, creating barriers against slip, increasing the hardness and modulus close to the surface. Carbonitriding is often applied to inexpensive, easy-to-process low-carbon steel to give the surface properties of more expensive and hard-to-machine steel grades.
The surface hardness of carbonitridden parts varies between 55 and 62 HRC. Certain pre-industrial hardening processes include not only carbon-rich materials such as charcoal, but also nitrogen-rich materials such as urea; this means that traditional surface hardening techniques are a type of carbonitriding treatment .
Advantages
Carbonitriding has advantages over carburizing. First, it has a higher resistance to softening during menstruation and higher fatigue and impact resistance. This method is especially applied to steels with low surface hardenability. For example, this method is applied to the valve bed; The parts are first carburized around 900-955°C, after the desired depth is achieved, the carbonitriding process is started and then cooled in oil. The surface hardness of the resulting part is higher than the hardness that will be achieved in carburizing; In addition, the carbonitriding layer formed on the surface increases the compressive stresses on the surface, increasing the contact fatigue strength.
Applications
Typical applications: gear threads, eccentric, axle, bearing, hydraulic piston rods, fasteners, tools and dies.