Improving the tribological properties of Ti-6Al-4V alloy by nitrogen-ion implantation

The tribological properties of N-2(+)-ion-implanted Ti alloy (Ti-6Al-4V) we re studied by performing lubricated ball-on-disk tests against steel balls. The friction coefficients of N-2(+)-ion-implanted disks ranged from 0.05 t o 0.2, which were lower than that of the unimplanted disk. Nt-ion implantat ion reduced the volumetric wear rate of the disks as well as that of the st eel balls. Moreover, the seizure limit of N-2(+)-ion-implanted disk was inc reased. These improvements were remarkable for doses above 2.5 x 10(17) ion s cm(-2). However, N-2(+)-ion implantation did not monotonously improve the tribological properties with increasing ion dose. The results were not sim ply attributed to an increase in the surface microhardness by N-2(+)-ion im plantation. Surface analysis revealed that the structure consisted of titan ium oxide on titanium, and titanium nitrides were formed by N-2(+)-ion impl antation. The observed transition in the tribological properties of Ti-6Al- 4V alloy was discussed in terms of surface structure produced by N-2(+)-ion implantation. (C) 1999 Elsevier Science S.A. All rights reserved.