Carbonitrieren
Carbonitriding is a special type of hardening. It is usually used with low to medium curing depths (CHD - Case Hardened Depthalt, old designation according to DIN 50190-1: Eht). Apart from carbon, ammonia is simultaneously diffused into the boundary layer in smaller amounts. Ammonia consists of nitrogen and hydrogen. In this process, the nitrogen generally acts as an alloying element in the edge regions of the workpiece. This improves the edge curability, and it is therefore possible to use cheaper steels (eg unalloyed or low alloy steels, free-cutting steels and deep-drawn steels) for curing. However, the risk of the formation of residual austenite for automatic steels and deep drawing steels is due to the higher manganese content.
Carbonitriding usually takes place at temperatures between 750 ° C - 930 ° C. The resulting carbonitriding depths are usually between 0.06 and 0.60 mm depth; this depends on the selected temperature: in the upper range, the nitrogen intake is lower than in the lower one. The temperature is therefore selected according to the desired property. In the upper region, the upper layer is carbonitrided, if the hardness of the edge layer is to be carbonitized, if a high enrichment of the boundary layer with nitrogen is to be achieved with respect to the properties of use. It is customary to allow carbonitrided parts after quenching. In the case of unalloyed steels, this is usually carried out at 150 ° C. to 180 ° C. and for alloyed steels at 160 ° C. to 200 ° C.
The frictional wear resistance and the emergency running characteristics of the nitrogen-enriched edge layer are better and the starting resistance is higher than is achieved with case hardening. The higher the nitrogen content of the application layer, the higher the tempering temperature can be chosen.
According to DIN 8580, nitriding is one of the manufacturing processes by material properties. The process of carbonitriding is, however, not one of the nitriding methods but of the hardening processes. The reason for this is that only small amounts of N (= nitrogen) are diffused into the microstructure and it is therefore not a heat-bonding layer-forming heat treatment. Edit source text Weblinks Edit sourcetext
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