X-ray diffraction measurements of plasma-nitrided Ti6Al-4V

A systematic study was undertaken with samples of commercial Ti-6Al-4V nitrided in a conventional d.c. plasma equipment. As treatment parameters, we have used: nitriding time (from 15 to 360 min); nitriding atmosphere (H-2-20% N-2 and H-2-60% N-2); total pressure (from 10 mPa to 1 kPa) and cathode temperature (from 673 to 943 K). X-ray diffraction measurements show that the effect of nitriding on the near-surface composition of (alpha + beta)-Ti-6Al-4V is a very complex function of the process parameters. Among these, it appears that the sample temperature plays the more dramatic role. For temperatures below 773 K, epsilon-Ti2N and delta-delta-TiN are clearly present only for a long period of treatment in a N/H=3/2 atmosphere. For the N/H=1/4 atmosphere, these nitrides are not present in the XRD pattern of samples treated at 773 K, even for a long treatment time such as 240 min. However: samples treated at 943 K show well-resolved epsilon-Ti2N and delta-TiN reflections, even for short treatment limes such as 15 min. (C) 1999 Elsevier Science S.A. All rights reserved.