Effect of Annealing on the Surface Hardness of High-Fluence Nitrogen Ion-Implanted Titanium.

Commercially pure titanium grade II was kinetically nitrided by implanting nitrogen ions with a fluence in the range of (1-9)·1017 cm-2 and ion energy of 90 keV. Post-implantation annealing in the temperature stability range of TiN (up to 600 °C) shows hardness degradation for titanium implanted with high fluences above 6·1017 cm-2, leading to nitrogen oversaturation. Temperature-induced redistribution of interstitially located nitrogen in the oversaturated lattice has been found to be the predominant hardness degradation mechanism. The impact of the annealing temperature on a change in surface hardness related to the applied fluence of implanted nitrogen has been demonstrated.

The Use of Electrochemical Methods to Determine the Effect of Nitrides of Alloying Elements on the Electrochemical Properties of Titanium ß-Alloys.

Titanium beta alloys represent the new generation of materials for the manufacturing of joint implants. Their Young's modulus is lower and thus closer to the bone tissue compared to commonly used alloys. The surface tribological properties of these materials should be improved by ion implantation. The influence of this surface treatment on corrosion behaviour is unknown. The surface of Ti-36Nb-6Ta, Ti-36Nb-4Zr, and Ti-39Nb titanium ß-alloys was modified using nitrogen ion implantation. X-ray photoelectron spectroscopy was used for surface analysis, which showed the presence of titanium, niobium, and tantalum nitrides in the treated samples and the elimination of less stable oxides. Electrochemical methods, electrochemical impedance spectra, polarisation resistance, and Mott-Schottky plot were measured in a physiological saline solution. The results of the measurements showed that ion implantation does not have a significant negative effect on the corrosion behaviour of the material. The best results of the alloys investigated were achieved by the Ti-36Nb-6Ta alloy. The combination of niobium and tantalum nitrides had a positive effect on the corrosion resistance of this alloy. After surface treatment, the polarization resistance of this alloy increased, 2.3 × 106 Ω·cm2, demonstrating higher corrosion resistance of the alloy. These results were also supported by the results of electrochemical impedance spectroscopy.

Influence of surface pre-treatment with mechanical polishing, chemical, electrochemical and ion sputter etching on the surface properties, corrosion resistance and MG-63 cell colonization of commercially pure titanium.

The impact of four pre-treatment techniques on the surface morphology and chemistry, residual stress, mechanical properties, corrosion resistance in a physiological saline solution and cell colonization of commercially pure titanium is examined in detail. Mechanical polishing, electrochemical etching, chemical etching in Kroll's reagent, and ion sputter etching with argon ions were applied. Surface morphologies reflect the nature of surface layer removal. Significant roughening of the surface and a characteristic microtopology become apparent as a result of the sensitivity of chemical and ion sputter etching to the grain orientation. The hardness in the near surface region was controlled by the amount of residual stress. Etching of the stressed surface layer led to a reduction in residual stress and surface hardness. A compact passivation layer composed of TiO, TiO2 and Ti2O3 native oxides imparted high corrosion resistance to the surface after mechanical polishing, chemical and electrochemical etching. The ion sputter etched surface showed substantially reduced corrosion resistance, where the corrosion process was controlled by electron transfer. The specific topology affected the adhesion of the cell to the surface rather than the cell area coverage. The cell area coverage increased with the corrosion stability of the surface.