Carbonitriding

The carbonitriding is a special kind of case hardening. It is mostly for low to medium hardening depths (CHD - old designation to DIN 50190-1 Case Hardened Depthalt, : chd ) applied. In addition to carbon, ammonia is simultaneously diffused into the surface layer in small amounts. Ammonia consisting of nitrogen and hydrogen. The nitrogen acts in this process usually as an alloying element in the edge regions of the workpiece. Thus, the Randhärtbarkeit is improved and it is therefore possible to use cheaper steels (eg unalloyed or low-alloy steels, free cutting steels and deep drawing steels ) for a cure. For machining steels and deep-drawing steels, however, there is a danger of the formation of austenite due to the higher manganese content.

The carbonitriding is usually at temperatures between 750 ° C - 930 ° C instead. The Karbonitriertiefen thus generated are usually between 0.06 to 0.60 mm depth; this depends on the selected temperature: at the top of the absorption of nitrogen is less than in the lower. The temperature is therefore chosen according to the desired property. At the top of one carbonidrided if you mainly on the hardness of the surface layer attaches much importance, in the bottom, if you want to achieve a high enrichment of the surface layer with nitrogen with respect to the performance characteristics. It is customary to let carbonitrided parts after quenching. This is done for unalloyed steels usually at 150 ° C to 180 ° C and for alloy steels at 160 ° C to 200 ° C.

The Reibverschleisswiderstand and the emergency running properties of nitrogen-enriched surface layer are better and the tempering resistance is higher than is achieved by case hardening. The higher the nitrogen content of the application layer, the higher the tempering temperature may be selected.

According to DIN 8580 nitriding is one of the manufacturing process by material property change. The process of carbonitriding but not one of the nitriding but to the hardening process. The reason for this is that only small amounts of N ( = nitrogen) diffuse into the structure and thereby is no connecting layer forming heat treatment.

  • Change material properties
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