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Ti-Nb β alloys are a promising alternative as an implant material due to their good properties and low Young's modulus, compared to other Ti-alloys currently employed as biomaterials. In this study, three materials of the Ti-Nb and Ti-Nb-Fe systems were produced by powder metallurgy techniques starting from TiH 2 (TH) powder. Several sintering cycles were employed to evaluate the H 2 elimination and the effect of sintering temperature on densification and fraction of β-Ti phase. Also, the influence of alloying element size using two kinds of Fe powder was evaluated. The highest loss of H 2 was achieved by decreasing heating rate at the temperature range of hydride decomposition. SEM images and XRD results show mainly a β-Ti phase for TH-40Nb and TH-5Fe-25Nb samples. The TH-12Nb sample shows (α + β) microstructure. Fe addition with smaller particle size seems to improve the diffusion of Nb into Ti which promotes a higher β-phase fraction and sample homogeneity.

The use of titanium hydride as a raw material has been an attractive alternative for the production of titanium components produced by powder metallurgy, due to increased densification of Ti compacts, greater control of contamination and cost reduction of the raw materials. However, a significant amount of hydrogen that often remains on the samples could generate degradation of the mechanical properties. Therefore, understanding decomposition mechanisms is essential to promote the components’ long life. Several studies on titanium hydride (TiH2) decomposition have been developed; nevertheless, few studies focus on the effect of the alloying elements on the dehydrogenation process. In this work, the effects of the addition of different amounts of Fe (5 and 7 wt. %) and Nb (12, 25, and 40 wt. %) as alloying elements were evaluated in detail. Results suggest that α→β transformation of Ti occurs below 800 °C; β phase can be observed at lower temperature than the expected according to the phase diagram. It was found that β phase transformation could take place during the intermediate stage of dehydrogenation. A mechanism was proposed for the effect of allying elements on the dehydrogenation process.

This work investigates the corrosion and tribocorrosion behavior of α + β Ti-12Nb alloy processed by casting and sintering, in 9 g/l NaCl solution at body temperature, and compares the results with the commercial Ti-6Al-4 V alloy. Different electrochemical techniques were used to access the corrosion behavior. Tribocorrosion behavior was studied at open circuit potential under continuous and intermittent sliding, and at anodic potentiostatic condition under continuous sliding. Results revealed that Ti-12Nb alloys presented similar tribocorrosion behavior although the sintered one exhibited a better corrosion behavior. Nevertheless, Ti-6Al-4 V presented better overall degradation resistance than both Ti-12Nb alloys.

The requirement of good mechanical properties, lower Young's modulus, superior corrosion resistance, and excellent biocompatibility makes b-type titanium alloys attractive materials for orthopedic implants. In this study, Ti-25Nb-5Fe and Ti-40Nb b-type titanium alloys were designed and produced by powder metallurgy route using titanium hydride, niobium, and iron powders. The effect of sintering conditions on microstructure, corrosion, and tribocorrosion behavior was explored. Electrochemical behavior was investigated in saline solution (9 g/L NaCl) at body temperature by using potentiodynamic polarization and electrochemical impedance spectroscopy. Tribocorrosion behavior was evaluated by reciprocating against an alumina ball at open circuit potential, as well, under anodic and cathodic potentiostatic conditions in saline solution (9 g/L NaCl) at body temperature. The physical, electrochemical, and tribo-electrochemical behaviors of both alloys were improved with increasing sintering time at 1250°C from 2 to 4 hours and decreasing Fe particle size for Ti-25Nb-5Fe alloy. Degradation under tribocorrosion conditions was mainly governed by mechanical wear on Ti-25Nb-5Fe alloy; however, Ti-40Nb alloy exhibited an antagonistic effect between corrosion and wear during testing under anodic applied potential due to the formation of a denser tribolayer.

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