The plasma nitriding behaviour of Fe-18Cr-9Ni alloy was compared with gas nitriding. The alloy was nitrided under the following conditions: specimen temperature: 823 K, nitriding time: mainly 108 ks, total pressure: 0.4-0.7 kPa, mixture ratio of N2 and H2: 0.25, discharge voltage: 350-450 V, current: 0.8-1.1 A. Formation of a surface layer of iron nitrides was not observed. Formation of a homogeneous internal nitriding layer, consisting of small precipitates of CrN and the γ-phase matrix, was, however, noted. The lattice constant at the specimen surface was smaller than that at greater depth. This may have been because the sputtering effect decreased the dissolved nitrogen content at the specimen surface. The sputtering of iron nitrides at the specimen surface by the plasma was experimentally confirmed through γ′-Fe4N formation on Si beside an alloy specimen. The characteristics of the plasma nitriding mentioned above are discussed in relation to the sputtering.
ASJC Scopus subject areas
- Condensed Matter Physics
- Electronic, Optical and Magnetic Materials
- Materials Science(all)