Nitrogen implantation into steels

Abstract

Nitrogen implantation into steels is certainly the most well-known case of the improvement obtained in wear resistance using implantation. To a large extent, tribological results depend on the steel composition but also on the implantation conditions (fluence, temperature and vacuum quality). Both aspects will be discussed. In the evolution of the implanted layer, the combined influence of the newly created phases, the residual stresses and the nitride grain size must be of primary importance even if they are not always fully controlled. These are studied as a result of the thorough characterization of the implanted region which has been performed by numerous researchers and will be reviewed here. The study consists first in plotting the distribution of the implanted element with a good depth resolution (Auger electron spectroscopy, secondary ion mass spectrometry and nuclear reaction analysis), secondly in measuring the grain sizes (transmission electron microscopy) and thirdly in identifying the compounds formed during implantation (conversion electron Mössbauer spectroscopy, grazing-angle X-ray diffraction, electron spectroscopy for chemical analysis, transmission electron microscopy etc.). With respect to the characterization of the implanted region, recent results will be reported and in particular those concerning the preferential orientation of the nitride and carbonitride phases under irradiation.