Microstructural and microhardness evaluations in ion nitrided titanium

Abstract

Pure titanium and Ti-6242S alloy were ion nitrided in the temperature range 800–1080°C in a pure nitrogen plasma at 5 Torr. using microhardness depth profiles and with the aid of calculated nitrogen concentration profiles, an empirical relationship between the nitrogen concentration and microhardness in the α-Ti was obtained. Nitriding of pure titanium resulted in a layered structure consisting of TiN (δ), Ti 2N(ϵ) and α-Ti. Similarly, ion nitriding of Ti-6242S alloy resulted in surface hardening by the formation of a thin TiN layer and a nitrogen solid solution hardened case. Transmission electron micrographs indicated precipitation of Ti 2N in the nitrided case of both pure and alloyed titanium. The distribution and morphology of these precipitates, however, were functions of nitrogen concentration as well as the distribution of alloying element.