STUDY OF NITROGEN-IMPLANTED STAINLESS-STEELS BY CEMS AND TEM

Combining TiN coating deposition by PVD and nitriding by nitrogen impl antation in stainless steels shows promise for the future if a good ad hesion between the coating and the substrate can be obtained. It is th erefore necessary to study the structure and composition of the nitrid ed surface with a view to optimizing the coating adhesion. Implantatio n of nitrogen at doses of 1-5 x 10(17) N+ cm(-2) and with an energy of 50 keV was realized in the nitriding of AISI 304 and AISI 310 austeni tic stainless steels. Some samples were heated in vacuo to 400 degrees C after implantation to simulate the temperature effect during PVD co ating. Conversion electron Mossbauer spectroscopy (GEMS) and transmiss ion electron microscopy (TEM) were used to investigate the nitride pha ses due to nitrogen implantation. These measurements confirm previous results obtained by X-ray diffraction (XRD) and by resonant nuclear re action analysis (RNRA). GEMS shows an evolution in the phases formed a fter implantation. At low doses, a solid solution in austenite was for med while a epsilon-(Fe, Cr, Ni)(2+x)N nitride was formed at higher do ses. For the 2 x 10(17) N+ cm(-2) implanted and post-heated sample, GE MS and TEM gave evidence for the presence of a nitrogen solid solution and confirmed the diffusion of nitrogen deep into the specimen.