Study of nitrogen-implanted stainless steels by CEMS and TEM

Abstract

Combining TiN coating deposition by PVD and nitriding by nitrogen implantation in stainless steels shows promise for the future if a good adhesion between the coating and the substrate can be obtained. It is therefore necessary to study the structure and composition of the nitrided surface with a view to optimizing the coating adhesion. Implantation 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 austenitic stainless steels. Some samples were heated in vacuo to 400 degrees C after implantation to simulate the temperature effect during PVD coating. Conversion electron Mossbauer spectroscopy (GEMS) and transmission electron microscopy (TEM) were used to investigate the nitride phases due to nitrogen implantation. These measurements confirm previous results obtained by X-ray diffraction (XRD) and by resonant nuclear reaction analysis (RNRA). GEMS shows an evolution in the phases formed after implantation. At low doses, a solid solution in austenite was formed while a epsilon-(Fe, Cr, Ni)(2+x)N nitride was formed at higher doses. For the 2 x 10(17) N+ cm(-2) implanted and post-heated sample, GEMS and TEM gave evidence for the presence of a nitrogen solid solution and confirmed the diffusion of nitrogen deep into the specimen.