Dr. Andrei Popescu, Researcher, Center for Advanced Laser Technologies - CETAL, National Institute for Lasers, Plasma and Radiation Physics, Romania

Title: Design, manufacturing and testing of Ti₆Al₄V cranial mesh prostheses printed by laser melting deposition

Abstract: Ti₆Al₄V cranial prostheses in form of meshes were 3D printed by Laser Melting Deposition in argon environment, using an Yb:YAG disk laser source and micronic Ti₆Al₄V powder as starting material. The printing was conducted using a robotic arm with computer controlled movements. The printed material was investigated by optical microscopy and was found to be dense, without porosity. Metallographic investigations exposed the biphasic α+β structure, with α grains developing dendritically in a β matrix. Energy dispersive X-ray spectroscopy revealed a composition very similar to the starting powder material. Mapping of selected areas on surface showed a uniform distribution of elements, with no segregations or areas with poor elemental distribution. X-ray diffraction evidenced two crystalline phases entering in composition of the bulk printed structure: a hexagonal phase similar to Ti and a Ti(1-x)Vx with cubic structure.

In order to reach the desired resolution for prostheses, a fine tuning of the laser power and the powder debit was conducted, in order to obtain a solid shape even after a single laser pass and to diminish unwanted blown powder stuck in the vicinity of the prosthesis elements. The robot trajectories selected for tracing the programmed contour proved to have an important influence on the quality of the printed shape and therefore a discussion with relevant examples will be conducted.

In vitro tests consisting in viability and proliferation of steoblast-like cells conducted on both printed and casted Ti₆Al₄V samples showed very similar biological behaviors, certifying that the deposited material is bioinert after deposition.

Keywords: Laser melting deposition; 3D printing of metallic implants; CAD-CAM design; Titanium alloys.