Investigation of in-situ alloying grade 23 Titanium with Copper by Selective Laser Melting Process for biomedical applications

Abstract

The medical industry has successfully utilised additive manufacturing (AM) technologies, such as laser and electron beam powder bed fusion (LPBF and E-PBF), to manufacture complex shapes from biocompatible materials in order to produce implants using computer aided design (CAD) geometry based on medical Computer Tomography (CT) scan data. AM transforms the original design of the customised digital model directly to the physical device. Modern medicine utilises the benefits of LPBF to manufacture complex customised implants with biocompatible materials. Ti6Al4V alloy is the most used Titanium alloy that has the appropriate mechanical, corrosion and biocompatible properties. Infection is the most common postoperative complication resulting in device failure after implantation. Copper is a proven antibacterial agent and in small amounts, is not toxic to the human body. Functionalisation of Ti6Al4V implants structure with Cu additions at the bone–implant interface, reduces the risk of bacterial infection. LPBF combines the advantages of powder metallurgy with complete melting of powder mixtures and provides a unique opportunity for the design of new alloys utilising compositions impossible for conventional methods. Manufacturing of titanium alloys and copper materials from a mixture of elemental powders and in-situ mixing and alloying during manufacturing, is an example of such an approach. The formation of in-situ Ti6Al4V-x at.% Cu (1%, 3% and 5% Cu) alloy structures by LPBF for application in medical implants was investigated. Ti6Al4V Extra low interstitials (ELI) powder was mixed with pure copper powder of similar particle size distribution. Process parameters such as laser power, scanning speed, hatch distance and layer thickness directly affect the surface quality and part density. Optimal process parameters were established for in-situ alloying Ti6Al4V-x% Cu to form dense parts with suitable microstructural and surface quality. Firstly, single track formation was studied at different scanning speeds for 170 W and 340 Wlaser powers. The effect of laser power and scanning speed on the track width and shape was described. Secondly, the surface roughness and single layer morphology was considered. Dense non-porous in-situ alloyed 3D samples were produced and analysed. Future research on mechanical properties, antimicrobial activity and cytotoxicity is required to substantiate the functional properties of in-situ Ti6Al4V-x at.% Cu (1%, 3% and 5% Cu) alloys.