Metallographic investigations of nitrogen-implanted titanium alloys

Pure titanium and Ti-6Al-4V samples were implanted with N+ with an ion energy of 180 keV and doses between 1 and 6.10(17) cm(-2). A change in the etching behaviour of the material due to the ion implantation was observed. Spherical sections were prepared for metallographic examination in order to investigate radiation effects. With this technique it is possible to visualize ion-and dose-dependent changes within the implanted zone and the depth of the modified zone can be also measured. Nitrogen implantation into Ti-6Al-4V results in depth-dependent precipitation of TiN, which can be identified by its typical golden colour. Further chemical analyses of the implanted layers were carried out with X-ray photoelectron spectroscopy. The depth profiles confirmed the precipitation of TIN. Nanoindentation measurements revealed an increase in microhardness after ion implantation into Ti-6Al-4V. Correlations between the changes in hardness and the results of metallographic and chemical analyses are discussed. (C) 1998 Elsevier Science S.A.