An investigation of cutting forces and surface damage in high-speed turning of Inconel 718

Knowing the stringent operating conditions to which superalloys are subjected to in automobile, aerospace and gas turbine industries, their efficient machining and generation of machined surfaces with high integrity assumes a lot of importance. Therefore, this paper presents an experimental investigation into the effect of various process and tool-dependent parameters on cutting forces, an indirect measure of machined surface integrity besides a detailed microstructural analysis of the machined surface damage, in high-speed machining of superalloy Inconel 718. Accordingly, the effect of cutting speed, feed rate, depth of cut and tool cutting edge geometry on cutting forces, surface roughness and surface damage in high-speed turning of Inconel 718 using PCBN tools has been discussed. The input parameters were varied as: V = 125–475 m min−1, f = 0.05–0.15 mm rev−1, d = 0.50–1.0 mm and edge geometry as: 30° chamfer, 20° chamfer and 30° chamfer plus honed. The results show that the radial and feed force components are almost equal and the main cutting force component is two to three times that of feed and radial force components. The honed plus chamfered cutting edge was influential in reducing cutting forces significantly. It was noted that specimens showing larger cutting forces generated poor surface finish as well as extensive surface damage.