Process development and mechanical properties of Ti-6Al-4V samples generated by laser material deposition with coaxial wire feed

Abstract

The use of wire in laser material deposition (LMD) eliminates major disadvantages of powder-based LMD processes, namely, contamination of the process cell with metal powder, significant material losses during the process, health and safety issues, as well as the impact of insufficient powder quality. A processing head with coaxial wire feed is used with a closed annularly shaped laser beam surrounding the wire, which is one of the distinguishing features. The laser beam and wire are arranged coaxially to each other, with the wire being fed through the inside of an annularly shaped laser beam without any shadowing. In contrast to lateral wire feeding, two substantial technological advantages can be identified: the process is independent of the feed direction and can manufacture complex 3D geometries. In this paper, a novel approach to deposit Ti-6Al-4V with wire-based LMD to increase the deposition rate to 500 g/h and develop process strategies to build up 3D volumes is described. In addition, stability criteria for the LMD process are determined and used for process development. The paper also presents characterization of the deposited layers and the procedure for generating tensile test samples from Ti-6Al-4V. Finally, the results of the built-up, heat-treated, mechanically processed, and tested samples are discussed, and the results are compared with those from the literature on powder-based LMD. Finally, an outlook toward future research and possible applications is given.