LASER WELDING OF Ti-6Al-4V PARTS PRODUCED BY ELECTRON BEAM MELTING

Metal-based Additive Manufacturing (AM) is a novel production process allowing to create full-dense three-dimensional objects. AM manufacturing is a layer-by-layer production process of the 3D drawn model under computer control. There is a great potential for Metal-based AM to replace conventional technologies that are currently used in aerospace, automotive and biomedical industries, by increasing the part design freedom, and the flexibility and product customization in manufacturing. Other technological challenges that arise are related to the welding of printed parts.

The present research is focused on the welding process of 3D printed Ti-6Al-4V parts made by the Electron Beam Melting (EBM) technique. Butt joints of parts that are 2-mm thick were laser welded without an additional material. The research work focuses on the study of microstructure and mechanical properties of the joint made from the printed parts, the influence of different parameters of the laser on the joint properties, and welding of different types of Ti-6Al-4V alloy – both printed and conventionally produced. The microstructure of base metals and the joint area of the parts were examined by means of optical and Scanning Electron Microscopy (SEM and HRSEM), Electron Backscattered Diffraction (EBSD) and X-Ray Diffraction (XRD).

Due to the fast cooling rate in the fused area, the fully martensitic microstructure was observed in the fusion zone, and a certain amount of martensitic structure was formed in the heat-affected area. Thus, a significant and less significant increase in hardness was observed in the fusion zone and in the heat-affected zone, respectfully, in relation to the bulk. Microstructures, mechanical properties and an analysis of the reasons for their formation will be discussed in the lecture.