Activated solution nitriding of stainless steels

The solution nitriding of the stainless steels can be optimized by a two st age process. The first stage involves an surface activation and an enrichme nt of nitrogen in the case due to internal nitriding. After this step at te mperatures between 1070 degrees C and 1150 degrees C follows the dissolutio n of the chromium nitrides and a solution nitriding. Investigations of ferr itic, martensitic and austenitic steels showed that this technology is supe rior compared to the one stage technology. The treatment time for an given layer thickness in the high temperature stage is cut in halve. The case con centration of nitrogen can be controlled by a material specific choice of t he treatment temperature and the partial pressure of nitrogen. For the inve stigated steels the desired microstructure of the case could be achieved by partial pressures of nitrogen between 0,35 an I bar The solution nitriding of ferritic-martensitic steels eneables the producti on of martensitic cases with a hardnesses up to 700 HV 0,3. An austenitic c ase with higher hardness and stability of the austenit can be produced by e nrichment the surface of austenitic and ferritic-austenitic stainless steel s with nitrogen.