Surface Modification of Titanium Implants

The influence of nitriding temperature (900 and 850°C) and partial pressure of nitrogen (105 and 1 Pa) on morphology and phase structural state of modified surface layers of commercially pure titanium (cp-Ti) was determined. It was shown that nitrided titanium provided much better anti-corrosion protection than nitrided Ti-6Al-4V alloy, and its corrosion resistance increased with decreasing nitriding temperature and partial pressure of nitrogen.

Tribological Behavior of Titanium Alloy Treated by Nitriding and Surface Texturing Composite Technology

This study experimentally investigated the effect of surface textures on the tribological mechanism of nitrided titanium alloy (Ti–6Al–4V). The titanium alloy samples were nitrided at various temperatures ranging from 750 to 950 °C for 10 h in a plasma nitriding furnace. Then, surface textures were fabricated on the polished titanium alloy and plasma nitrided samples by laser process system. The surface roughness, microhardness, and constitution of samples treated by single nitriding and samples treated by composite technology were characterized. The tribological properties of the samples were investigated on a CSM ball-on-disc tribometer. The results show that plasma nitriding effectively enhances the wear resistance of the substrate. The wear rate decreases first and then increases with the increase of nitriding temperature, and the wear rate reaches the minimum at 900 °C. However, the increase in roughness caused by nitriding treatment leads to an increase in the friction coefficient. It is found that surface textures can obviously reduce the friction coefficient of the nitrided titanium alloy. In addition, it can also reduce the wear rate of titanium alloys after nitriding at 900 and 950 °C. It can be concluded that the nitriding and surface texturing combined treatment can obviously reduce the friction coefficient and wear rate at the nitriding temperatures of 900 and 950 °C. This is attributed to the combined effect of high hardness of nitride layers and the function of micro-trap for wear debris of surface textures.

Interpenetrating polymer network adhesive bonding of PEEK to titanium for aerospace application

This investigation highlights the rationale of epoxy-novolac interpenetrating polymer network (IPN) adhesive bonding of low-pressure plasma treated polyether ether ketone (PEEK) to plasma nitrided titanium for aerospace application. Physico-chemical characterization of surface modified PEEK is carried out by surface energy measurement and X-ray photoelectron spectroscopy (XPS) analysis. Lap shear tensile tests are carried out to measure mechanical properties such as lap-shear tensile strength, Young’s modulus, percentage elongation at break (% EB) and toughness of the adhesive bonded PEEK to titanium joint. XPS analysis reveals the presence of the oxygen (O) functional group into the plasma treated PEEK surface. This polar functional group O increases the surface energy on the plasma treated PEEK surface, and consequently, the adhesive bond strength is enhanced. The values of Young’s modulus, % EB and toughness of epoxy-novolac IPN adhesive bonded plasma treated PEEK to plasma nitrided titanium are increased considerably in respect to epoxy-novolac IPN adhesive bonded untreated PEEK to untreated titanium joint. Therefore, the present investigation concludes that the adhesive bond strength not only depends on the surface characteristics of PEEK and titanium, but also on the cohesive properties of the adhesive.