Energy Density Effect on the Interface Zone in Parts Manufactured by Laser Powder Bed Fusion on Machined Bases

Abstract

The hybrid manufacturing procedure of combining an initial machining process and a posterior laser powder bed fusion (LPBF) process opens a new range of possibilities for manufacturing complex parts, promising to reduce both costs and printing time. Hence, the first portion of the part might be manufactured by machining, which is used as the substrate for the LPBF. Different manufacturing processes produce a melting interface zone (MIZ) that can affect the mechanical properties of hybrid parts. This work investigates the properties of the MIZ in hybrid parts. The influence of the energy density of the LPBF process on the interface zone and the mechanical properties of the final hybrid part were assessed. The different tests showed high-quality interphase even with low energy density, with a melting depth of up to 0.3 mm. Tomography analysis showed no pores in the MIZ and the increase in pore number with the scanning speed, reducing the UTS of the hybrid samples from 8 to 42% in relation to machined Corrax®. Additionally, a test piece for injection molding was produced by this new hybrid manufacturing process. The results showed that the costs and manufacturing time were reduced by about 50%, showing a potential application of hybrid manufacturing in such applications. Besides, this work identifies a limitation of the hybrid manufacturing approach using LPBF machines which are not equipped with a system to identify the substrate coordinate system. The present study develops an operational method to identify the coordinate system in order to ease the referencing of the pre-machined substrate within the machine platform.