Properties of nitrided layers formed during plasma nitriding of commercially pure Ti and Ti-6Al-4V alloy

► Diffusion cycles combined with active nitriding on Ti-6Al-4V improved efficiency. ► Nitriding for 156 h at 730 °C led to predominance of TiN. ► Nitriding for 76 h at 730 °C led to coexistence of TiN and Ti2N. ► Al- and V-rich regions were detected just beneath the TiN/Ti2N layer.