Influence of Hybrid-Additive Interfaces Manufactured by Laser Powder Bed Fusion on the Surface Topography after Machining of Ti-6al-4v

Abstract

In hybrid-additive manufacturing, additive structures are produced on wrought base bodies. Hybrid-additive manufacturing using Powder Bed Fusion - Laser Beam offers unrestricted freedom of design with reduced build time and thus more economical production. Between the wrought and additive component area, an interface is created which has different microstructural properties. In this paper, the influence of the hybridadditive interface on the machining process and its resulting surface topography is investigated. For this purpose, hybrid-additive specimens (Ti-6Al-4V on Ti-6Al-4V) are manufactured in as-built condition and after heat treatment (4 h at 800 °C). The specimens are machined by circumferential climb milling. For detailed investigation, the tests are carried out with a single-tooth tool at varying cutting speeds and depth of cut. Micrographs show a hardly existent heat affected zone in the interface. The additive microstructure shows higher hardness than the wrought microstructure, the delta is reduced with heat treatment. The delta in hardness leads to different cutting forces which in turn result in differing tool deflection. Hence, waviness Wt between the microstructure are observed depending on control variables. High cutting speeds and high depth of cut result in the lowest waviness of 4.2 μm. Further, heat treatment reduces the scatter of roughness values in additive microstructure.

Keywords: Selective laser melting, hybrid additive manufacturing, cutting force, surface topography, Ti-6Al-4V