Plasma immersion ion implantation of AISI 304 stainless steel in toroidal and cylindrical geometries

PIII technology has been applied in vacuum chambers with toroidal and cylindrical geometries in order to study the nitriding of AISI 304 austenitic stainless steel plates. A high voltage generator provided a 5 kV polarization in 5 Vs long pulses at 1 kHz in a nitrogen plasma created by a DC source. An elemental analysis of the samples was performed by means of SEM while XRD was used to determine the characteristic patterns of their nitrides. Results indicate a significant increment in the implanted nitrogen content of the substrata. The detected nitrides were identified as Fe3NiN and FeNiN, which are associated with the enhanced austenitic phase of the stainless steel. Thus, the Vickers microhardness of the samples doubles in the cylindrical chamber and reaches a 2.8 times increase in the toroidal one. It is also observed that this microhardness tends to grow with the gas pressure, and therefore with the sample temperature, as well as with the thickness of the nitrided stratum. (C) 2004 Elsevier Ltd. All rights reserved.