Micro milling machinability of direct energy deposition (DED) processed TI-6AL-4V

Direct metal deposition (DMD) and laser engineered net shaping (LENS) technology have been widely investigated and utilized in Ti-6Al-4V components in aerospace and biomedical industries for their increased in mechanical property and for the ability to produce and clad complex metallic geometries difficult to manufacture through conventional metal forming techniques. Nevertheless, one of the residual challenges in Laser Engineered Net Shaping (LENS), is the characterization of the machinability. Porosity and mechanical behavior arises due to unique material thermal histories during processing. This paper investigates the machinability, specifically cutting forces and quality surface, of LENS-processed Ti-6Al-4V and how these depend on additive deposition parameters and direction of build processing. Mechanical properties were found to be most desirable when the tensile orientation is orthogonal to the build direction and parallel to the scan direction as well as closer to the center of a fully dense component. This study investigates microstructure through micrograph, hardness test and porosity thanks to tomography. The aim is to probe how the LENS deposition parameters are related to mechanical property and consequently how those interact with the machining process. The future prospective is to achieve specific functional surface characteristics, through both thermal and melt pool controls, by predicting mechanical properties from process parameters, also taking into account the machinability properties.