STRUCTURE, MECHANICAL, AND TRIBOLOGICAL PROPERTIES OF TITANIUM IMPLANTED ALUMINA

A study of the effects of titanium ion implantation on the structural, mechanical, and tribological properties of single crystal and polycrystalline alpha-alumina has been carried out. Rutherford Backscattering Spectrometry (RBS) in channeling geometry shows that a great proportion of implanted titanium ions are substitutional at low fluence. This fraction falls to near zero as an amorphous layer is formed. The chemical states for implanted titanium are determined by X-ray Photoelectron Spectroscopy (XPS). Titanium is present in the Ti3+ state near the surface and as metallic Ti0 and as Ti3+ at depths corresponding to higher local concentration of titanium. The same behavior is observed for polycrystalline and single crystal alpha-alumina. Nanoindentation experiments show that low fluence implantation of titanium results in an increase of mechanical properties whereas high fluence implanted samples exhibit reduced hardness and Young's modulus compared to unimplanted samples. The friction coefficient is not changed by titanium ion implantation. Likewise, the wear characteristics were not changed by low fluence implantation, but amorphization at high fluence leads to a greater disk wear rate.