This study aims at investigating the effect of cutting speed, feed rate and depth of cut on surface roughness, microstructure of machined part and tool wear in dry rough turning of Ni superalloy Inconel-718 using PVD coated (TiAlN + TiN) carbide tool inserts. Taguchi’s method for optimization of machining parameters (vc = 40-60 m/min, f = 0.05-0.1 mm/rev and d = 0.25-0.5 mm) was used. A Finite Element (FE) model of the tool geometry was developed in order to understand the trends of deformation and shear stress induced due to mechanical loads during orthogonal machining. Regression equations versus the cutting parameters were obtained for surface finish and tool wear. Changes in microstructure were found to be negligible. The investigation suggested that for PVD coated (TiAlN + TiN) carbide tool inserts, cutting speed of 60 m/min, feed rate of 0.05 mm/rev and depth of cut of 0.5 mm were optimum for producing the best cutting results.

Nickel-based alloys are composed of over half of the materials used in the aerospace industry. These alloys are under constant improvement for better strength and surface integrity. Surface integrity is defined as the inherent condition of a machined surface and its major components can be grouped into surface texture (of which surface roughness is the most important), metallurgy, and the residual stress generated on the surface and subsurface of the machined workpiece (Jawahir et al., 2011; and Ulutan and Ozel, 2011). Inconel is a family of austenitic nickel-chromium-based superalloys. Inconel-718 (UNS N07718) is a precipitation hardening Ni superalloy, which contains significant levels of molybdenum, iron, columbium and niobium, along with traces of aluminum and titanium. Due to the high amount of chromium and other alloying elements, it is a highly corrosion and oxidation resistant material well suited for service in hot and corrosive environments. When heated, Inconel- 718 forms a stable and adherent oxide layer that protects the surface from further attack. It is very heat treatable and a wide variety of mechanical properties, including hardness and strength, can be obtained (Arunachalam and Mannan, 2000).

Mechanical Engineering Journal, Inconel-718, High speed turning, Orthogonal machining, Optimization of machining parameters, Finite Element Method (FEM) simulation.