INVESTIGATION OF NITRIDE PHASES IN STAINLESS-STEELS BY NUCLEAR-REACTION ANALYSIS AND X-RAY-DIFFRACTION

Abstract

Hard, wear-resistant TiN coatings on metals are mainly used when good coating adhesion to the substrate material can be obtained. However, if the same treatment is carried out on different types of steel, marked differences in coating adhesion are observed. Thus, to optimize the coating adhesion, it is necessary to know what phases and contamination are present on the substrate prior the coating, and how these are affected by the deposition process. Implantation of nitrogen at doses ranging between 1 and 5 x 10(17) N+cm-2 is used to form the nitride in austenitic steels 304 and 310. Preliminary results are presented on the phases obtained with different plasma nitriding processes, measured using nuclear reaction analysis and X-ray diffraction techniques. No difference is observed between the two types of steel, except when the substrate is heated at 400-degrees-C after the implantation. At low doses, only austenite, expanded austenite and gamma'-Fe4N are observed. With high doses, the diffraction patterns show the appearance of epsilon-(Fe, Cr)2N1-x or Cr2N phases. Interdiffusion of nitrogen is demonstrated when a Ti-TiN layer is deposited on an implanted sample.