title: Surface topography, corrosion and microhardness of nitrogen-diffusion-hardened titanium alloy.
abstract: Mechanical-electrochemical interactions accelerate corrosion in mixed-metal modular hip prostheses. These interactions can be reduced by improving the modular component machining tolerances or by improving the resistance of the components to scratch or fretting damage. Wrought cobalt-alloy (CoCrMo) is known to have better tribological properties compared to the titanium alloy (Ti64). Thus, improving the tribological properties of this mixed-metal interface should center around improving the tribological properties of the Ti64 alloy. This study used scanning probe microscopy (contact, tapping and phase contrast mode), scanning electron microscopy, corrosion testing, and microhardness testing to determine the effect of a nitrogen-diffusion hardening process on the surface morphology, electrochemistry and surface hardness of the Ti64 alloy. The nitrogen-diffusion-hardened titanium alloy samples (N-Ti64) had a more pronounced grain structure, more nodular surface, and significantly (P<0.01) higher mean roughness values than the control-Ti64 samples. The N-Ti64 samples also exhibited at least equivalent corrosion behavior and a definite increase in surface hardness compared to the control Ti64 samples. The equivalent corrosion behavior and improved surface hardness indicate the potential for N-Ti64 samples to resist similar and mixed-metal scratch and fretting damage. The use of N-Ti64 as opposed to control-Ti64 may therefore reduce the occurrence of mechanical-electrochemical degradation in mixed-metal modular total hip prostheses.
authors.affiliation: Department of Biomedical Engineering, University of Alabama at Birmingham 35294-4440, USA. krishna@uab.edu
authors.forename: R
authors.initials: R
authors.lastname: Venugopalan
authors.forename: M A
authors.initials: MA
authors.lastname: George
authors.forename: J J
authors.initials: JJ
authors.lastname: Weimer
authors.forename: L C
authors.initials: LC
authors.lastname: Lucas
mesh_terms: D000497:Alloys; D001672:Biocompatible Materials; D004563:Electrochemistry; D006244:Hardness; D006622:Hip Prosthesis; D006801:Humans; D008855:Microscopy, Electron, Scanning; D009584:Nitrogen; D013499:Surface Properties; D014025:Titanium
chemical_list: D000497:Alloys; D001672:Biocompatible Materials; D014025:Titanium; D009584:Nitrogen