Spark Plasma Sintering of Titanium and Cobalt Alloys For Biomedical Applications

This work was carried out in the frame of an industrial research project in cooperation with the Eurocoating SpA and K4Sint Srl, aiming at developing the commercial pure titanium, the Ti-6Al-4V and the Co-28Cr-6Mo alloys by Spark Plasma Sintering (SPS) for biomedical application. The definition of the process parameters for the production of a highly porous (cp-Ti), full density materials (Ti-6Al-4V and Co-28Cr-6Mo), and their combination in a surface functionalized full density substrate was the central focus. The SPS parameters were optimized to obtain the Co-28Cr-6Mo alloy in full density state for matching the international standards. Tensile and fatigue were the main properties under investigation. In the case of Ti-6Al-4V alloy the best SPS parameters was defined in a previous work by means of densification curve and tensile properties. Therefore, the fatigue resistance was the main property under investigation. The optimization of the sintering parameters was evaluated by the interdependence between the density, microstructure and hardness. Co-sintering of the cp-Ti with the Co alloy and the cp-Ti with the Ti alloy was carried in order to obtain a porous coated full density substrate in one single step. The SPS parameters were optimized in order to achieve a coating like structure containing macropores with specific range of size and highly interconnected. To that, the space holder technique was chosen since it allows a very good control of the pores characteristics. The interactions at the interfaces were characterized and the best SPS strategy was defined. Subsequently, fatigue tests were carried out in order to assess the influence of the porous coating on the fatigue resistance of the full density substrates. As a general conclusion it may be assessed that the process parameters for the production of the investigated biomaterials have been defined and the microstructural characteristics, as well as mechanical, corrosion properties and wear resistance satisfy the requirements on the international standards. These results have been used to produce implants which are under test.