Depth Profiles of Residual Stresses in Inconel 718Machined with Uncoated and Coated Tools

Abstract

Inconel 718 is one of the super-alloy materials, belonging to nickel-chromium alloy family, which has major applications in aerospace sector such as engine parts and turbine components. Durability of these components during engineering performance is affected by residual stresses induced in them in the course of their manufacturing processes. The concept of the present paper is to provide an insight view of induced residual stresses in Inconel 718 work piece, when machined with coated (TiN) and uncoated tools at optimum conditions. For this purpose, turning experiments have been conducted on IN718 material through statistical approach using L9 orthogonal array. Taguchi optimization method is exercised with the emphasis on minimizing the cutting forces resulted during machining. The residual stresses generated in the work piece at the optimum conditions employed for both the tools have been evaluated using XRD method. Conditions such as cutting speed of 60 m/min, feed at 0.068 mm/rev and depth-of-cut of 0.10 mm have been optimized for achieving minimum cutting forces during machining of IN 718 using both coated and uncoated tools. However, tensile stresses on the initial surface layer and compressive stresses in the sub-surface layers are found higher in the work piece material machined with uncoated tool. Surface roughness and temperature developed on the surface of the machined bar are higher in case of uncoated tool than those with coated tool.