Abstract
In this study, a nickel-based superalloy Inconel 718 material was developed through direct metal laser sintering process. To enhance the mechanical properties, printed material is heat treated at two different conditions in the combination of solution and aging. The transformation of microstructure from original anisotropic phase are studied using optical microscope. The change in mechanical properties were evaluated. The hardness of the heat- treated samples obtained are 35HRC and 39HRC for the heat treatment plan at 1100˚C + 845˚C and 980˚C + 720˚C (solution + ageing) respectively. Further, micro holes were machined on these two material samples using spark erosion micro machining or micro electric discharge machining (µEDM) process. Applied voltage, capacitance, and material hardness were three major variable parameters. Experiments are performed with hollow tungsten carbide rod of 300µm in diameter as a drill tool rotating at a speed 1500rpm for a constant machining time of 30min. Optical and scanning electron micrographs have been used to analyse the hole quality and therefore the performance of µEDM. Perfect concentric drill hole was produced with 35HRC sample than the other. Weld spatters and metal drops found around the surface of 39HRC sample. The range of drill hole varies to a maximum of ϕ385µm in low hardness and ϕ400µm in high hardness samples. The depth of drill hole is maximum with high hard sample at l00V and 100nF process condition. Light spectroscope – based roughness characterization revealed the minimum surface roughness measured was 6.946µm in low hard and 9.829µm in high hard material.