Biocompatibility and surface characterisation of PIRAC-treated titanium material

Abstract

Titanium and its alloys are commonly used as biomaterials due to their advantageous properties, such as their high-strength-to-weight ratio, resistance to corrosion, low elastic modulus and most importantly due to their excellent biocompatibility. However, titanium based alloys have the tendency to gall when in sliding contact with other metals under load. This characterises titanium and its alloys as materials with poor abrasive and adhesive wear resistance, limiting many implant applications. Surface engineering techniques intended to generate titanium nitride (TiN) have been previously recommended to combat such problems. TiN has a high hardness and has been approved by the Federal Food and Drug Administration for use in titanium and the components of titanium alloy implants. Powder Immersion Reaction Assisted Coating (PIRAC) nitrogen-diffusion treatment is a relatively simple thennochemical diffusion based procedure which has been proposed as a technique capable of creating a TiN/Ti2N compound layer on titanium alloys. PIRAC is cost-effective when compared to other established nitriding techniques such as a gas and plasma nitriding which typically require the use of vacuum furnaces. Also since PIRAC is a nitrogen diffusion process, it can lead to superior adhesion (compared to PVD) of the ceramic compound to the underlining nitrogen-rich substrate.