The influence of turning parameters on surface integrity of nickel alloy 625

Abstract

© IMechE 2016.Nickel-based alloys are used in industrial sectors where high mechanical strength and corrosion resistance are required at high temperatures. However, these alloys have low machinability as a consequence of inherent properties. Some of these properties such as high cold work hardening rate and low heat conductivity may cause damages to the machined surface. Among the nickel-based alloys, one that has good properties for oil exploration is alloy 625. As the components made of this alloy are frequently used in very rough environments, this study sought to evaluate the influence of tool geometry, cutting conditions (feed and cutting speed) and tool condition (fresh or worn) on the surface integrity of turned alloy 625 parts in order to discover turning practices for this alloy that result in minimal damage to the workpiece surface. A secondary aim was to evaluate how these input variables affected the life of the coated carbide tools used in the turning experiments with this alloy. The main conclusions are that (a) the surfaces produced with a fresh tool with positive geometry had compressive residual stresses, while those produced with negative tool geometry had tensile residual stresses and (b) when a worn tool was used all the surfaces produced had compressive residual stresses.