Selection of machining condition on surface integrity of additive and conventional Inconel 718

Abstract

Abstract Inconel 718 is a nickel-based superalloy used in steam turbines, jet engines, etc., where it is subjected to high thermomechanical loads. Inconel 718 is the most preferred alloy in the above applications due to its excellent resistance to fatigue and creep. Inconel 718 is mainly strengthened by the precipitates which were formed during the heat treatment process by the combination of elements like Nb, Ti, and Al along with the base element Ni. Selective Laser Melting (SLM) is one of the most used additive manufacturing processes to manufacture components with high dimensional accuracy in a flexible manner with less material usage. The samples fabricated by SLM were subjected to two heat treatments: Hot Isostatic Pressing (HIP) to improve the density followed by the Aeronautic Heat Treatment (AHT) in order to improve the material properties. The heat-treated SLM samples have the same mechanical properties of the conventional Inconel 718 fabricated by the Cast and Wrought (C&W). The Central Composite face-centered Design (CCD) was used for the Design of Experiments (DOE) in which three different cutting speeds (vc) and feed rates (fz) were considered whereas the depth of cut (ap) is kept constant. Machining experiments were conducted under dry, Minimum Quantity Lubrication (MQL) and emulsion (Wet) conditions on both the cast and wrought (C&W) Inconel 718 and additive fabricated SLM Inconel 718. The optimum cutting condition for C&W and SLM Inconel 718 samples was determined based on three criteria: minimum specific cutting energy (Wc), minimum tool wear (Vb) and minimum surface roughness (Ra). From the overall results, it is being inferred that the SLM Inconel 718 produced better results compared to C&W Inconel 718.