Titanium carbide (TiC) reinforced Titanium Matrix Composites (TMCs) have been synthesized via an in-situ reactive spark plasma sintering (SPS) process using commercial Ti-6Al-4V spherical powders pre-coated with 1 wt.% carbon nanoparticles by low-energy ball milling. Graphite flakes are used as carbon source, which aids powder flow during mixing as lubricant. Graphite transforms to nano-crystallite carbon during mixing which is favourable for the rapid formation of TiC second phase in the following SPS process. The composites exhibited a novel honeycomb-like cellular microstructure with the formation of 5-6 vol.% fine TiC submicron grains interconnected in the titanium / matrix. In addition, the reinforcement of the TiC phase with a nano-hardness of 12.4 GPa, improves the wear resistance of the parent alloy matrix (5.1 GPa), with a reduction of 26-28 % in wear rate during dry reciprocating sliding tests against Si3N4 balls. During sliding, the wear debris (predominantly anatase TiO2) builds up on the raised TiC hard phase forming a barrier layer of adhered oxide that can protect the alloy matrix underneath from abrasion and oxidation, leading to a reduced wear rate.

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CoCrMo alloys have been widely used in hip replacements. On the one hand they have exhibited excellent long-term survival rates, but recently high failure rates have been observed, associated with adverse local tissue reactions. It is still a puzzle why CoCrMo alloys sometimes work very well, while at the other times the failure rate is unacceptably high. The current work aims to investigate the influence of protein adsorption on the oxide layer properties and consequently on corrosion behaviour of CoCrMo biomedical grade alloys in different surface and media conditions. Electrochemical Impedance Spectroscopy (EIS), SEM and AFM were employed to characterise the surfaces. TEM was also used to reveal the subsurface chemical composition. The results showed a significant drop in the resistance of the oxide layer on the surfaces after some cathodic potential polarization. It was also shown that higher protein content and temperature reduced the oxide layer/metal surface interface resistivity. EDX quantitative chemical composition spot analysis of the subsurface after cathodic polarization showed a depletion of chromium in the outermost layer. AFM imaging and peak-force quantitative nanomechanical mapping QNM revealed lower adhesion forces for a relatively thick proteinaceous adsorbed layer on the surface after high cathodic polarization in particular at 50°C.