Formation of titanium oxide films on titanium and Ti6A14V by O2-plasma immersion ion implantation

Titanium and Ti6Al4V have been treated by oxygen-plasma immersion ion implantation (O-2-PIII) to form protective oxide surface layers. The oxide formation has been investigated for dependence on the ion density of the plasma, pulse repetition rate and pulse number, corresponding to process time. The ion density was varied by means of the magnetic field of an external ringmagnet. The sample temperature did not exceed 400 degreesC when implanting under active cooling at a low ion density and a purse repetition rate of 400 Hz. Increasing the ion density and the pulse repetition rate and stopping the sample cooling caused the temperature to rise to 650 degreesC. The composition of the modified surface layer has been evaluated by Rutherford backscattering spectrometry. At low temperature, the amount of incorporated oxygen and its depth distribution is determined by ion-solid interactions. With increasing temperature the oxygen distribution was determined by both implantation and diffusion. A saturation of the oxygen concentration at 66 at.% has been observed at the outer surface layer. Phase characterisation assessed by X-ray diffraction has shown the formation of rutile TiO2 and alpha -TiO in titanium for temperatures exceeding 510 degreesC. In the case of Ti6Al4V, peaks of the other allotropic form of TiO2, anatase, additionally appeared and became dominant for higher doses and temperatures. Surface imaging by atomic force microscopy (AFM) has shown a strong increase in surface roughness from 10 to 69 nm when oxides form. (C) 2000 Elsevier Science S.A. All rights reserved.