ABSTRACT Ti-6Al-4V was plasma nitrided using several N2/H2 ratios and substrate temperatures. In order to investigate the combined influence of these parameters on phase composition and thickness of the coatings, the phases in the as received, annealed, and nitrided Ti-6Al-4V samples were identified with Rietveld refinement. In the as-received and annealed samples the structure parameters of α-Ti and β-Ti were slightly changed, due to the substitution of titanium atoms by Al or V in the α-and β-Ti unit cells. A combination of multiple angle grazing incidence X-ray diffraction, nuclear reaction analysis and cross sectional micrographs showed compound layers consisting of an outer layer of stoichiometric ẟ-TiN over a phase mixture of ẟ-TiN and ɛ-Ti2N, formed on top of a nitrogen diffusion region in the alloy. Higher nitriding temperatures induced thicker compound layers, and higher nitrogen content of the plasma induced thicker fine-grained ẟ-TiN top layers.

Titanium nitride films were formed on the surface of Ti-6Al-4V discs by plasma nitriding (glow discharge) in different N2:H2 atmospheres at several substrate temperatures. In this study the influence of the process parameters on dynamic micro-hardness were investigated. Grain sizes of the nitride films, determined with X-Ray Diffraction, were related to the nitriding parameters. TiNx stoichiometry was determined with Nuclear Reaction Analysis and showed a correlation to substrate temperature during the nitriding process. Micro-hardness measurements were taken on the nitrided surfaces. Grain sizes increased for a particular gas composition of 60%N2+40%H2 where hardness was lowest.