Effect of HAp and β-TCP incorporation on the tribological response of Ti6Al4V biocomposites for implant parts.

Titanium and its alloys have been widely used in many engineering areas due to their properties. Despite having a high implant-tissue osseointegration time, Ti6Al4V has been extensively used in prosthesis and articular implants. To promote a faster bone ingrowth and consequently reduce the implant fixation time, the addition of a bioactive phase to form a biocomposite seems to be an excellent solution. Because of their bioactivity and similarity in composition with the human bone, HAp and β-TCP are two of the most widely used calcium phosphates in biomedical applications. To guarantee a strong adhesion of the previous bioactive materials in the implants surface, samples of Ti6Al4V, Ti6Al4V+HAp (10 vol %) and Ti6Al4V+β-TCP (10 vol %) TCP were processed by the hot pressing technique. Tribological tests against Al2 O3, lubricated in PBS at 37°C were carried out on a ball-on-flat reciprocating sliding geometry. Loads in the range of 3 N to 30 N were applied and their effect on the friction behavior and wear resistance of the tested materials was evaluated. Values of the coefficient of friction as well as the wear rate tend to increase with the addition of a bioactive phase to the Ti alloy. Micrographs of the worn surfaces showed that abrasion and plastic deformation are the prevailing wear mechanisms in the studied tribosystems. For biocomposites, particularly in the case of Ti6Al4V+HAp, pull-out of bioactive particle clusters has a determinant role on the tribological response, increasing both the friction coefficient and the specific wear rate.