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Inconel 718 alloy is difficult to machine using conventional methods due to its physical properties. Thereby, additive manufacturing (AM) of IN718 components with near-net shapes has been extensively studied. Even though AM processes provide shape and size accuracy, there is still the need for the machining of the AM-processed components to achieve the final shape of a component. Laser powder bed fusion (LPBF) has been successfully utilized to fabricate near-net shape IN718 components; moreover, the microstructure of LPBF-IN718 was unique owing to the AM processing, resulting in differences in grain size, grain boundary characteristics, and grain orientations. Furthermore, these microstructural characteristics are expected to alter the machining performance of IN718. Therefore, this study investigated the wire electro-discharge machining (WEDM) performance of LPBF-718 samples compared to wrought IN718 while focusing on the unique microstructure characteristics of LPBF-IN718 samples (lamella, single-crystal, ploy-crystal). Three different cutting strategies (rough, semi-finish, and finish) were implemented to understand the performance of the multi-pass cutting phenomenon and its effect on the surface of IN718. For all samples, rough (single pass) cutting displayed high roughness, while finish (three passes) cutting exhibited good surface quality. Compositional analyses on the machined surface showed debris formation including Zn and Cu-containing recast material, indicating wire erosion. The surface of single-crystal LPBF-IN718 after the WEDM process was smooth owing to its large grain size and less amount of grain boundary, resulting in slow cutting speed but a good surface finish. Thus, this study, for the first time, investigated the effect of unique microstructural characteristics of LPBF-fabricated IN718 on WEDM performance and machined surface quality. [ABSTRACT FROM AUTHOR]

Refractory high-entropy alloys (RHEAs) have high strength and hardness but limited plasticity at room temperature, making them challenging to process and shape using conventional techniques. In the current study, HfNbTaTiZr RHEAs were machined using wire electric discharge machining (WEDM), which enables precision shaping of hard and brittle materials without subjecting them to high stresses. The roughness of the surfaces and sections cut using WEDM was compared. Average surface roughness (Ra) increased by approximately 0.75 μm due to the limited heat transfer capability of the dielectric fluid in removing debris and cooling the interior of the sample. SEM and EDS analyses taken from the machined surfaces revealed microcracks, voids, globules, craters, and debris formed on the surface because of the sudden cooling of the dielectric liquid after melting and evaporation under intense heat. Cross-section analysis showed that the microcracks on the surface were approximately 30 μm deep in the heat-affected zone and did not go further into the workpiece. Hf, Nb, Ta, Ti, and Zr as well as Cu and Zn were found on all machined surfaces indicating the consumption of the wire electrodes. [ABSTRACT FROM AUTHOR]

In this study, the holes of glass fiber reinforced polymer (GFRP) and multi-walled carbon nanotubes (MWCNTs) doped GFRP composite materials were drilled using abrasive water jet (AWJ), CO2 laser cutting, orbital drilling, and punching methods; the effects of these methods on hole quality were determined. The hole entry and exit dimensions were obtained equal and in the desired size by orbital drilling; thus, kerf formation was prevented due to the lateral and face milling of the end mill. The surface hardness change was not observed in the hole circles obtained with the orbital drilling and punching methods. However, epoxy hardening was observed in the hole circles obtained by laser cutting due to the heat effect of laser beam. In AWJ method, matrix-fiber integrity was disrupted, and delamination was observed due to the effect of water pressure and kinetic energy; consequently an increase in material thickness was observed and surface hardness decreased. It was determined that MWCNTs additive increased the surface hardness of composites and maintained its hardness and durability in post-cutting measurements. Splintering and burring were not seen in any method, but fiber carbonization was observed in the inner parts of the hole due to thermal effects in laser cutting. [ABSTRACT FROM AUTHOR]