Turning of High-performance Materials with Rotating Indexable Inserts

Abstract

High-performance materials with excellent heat resistance are necessary to meet future demands on improving the efficiency of energy converting technologies in the field of power plant construction and aviation industry. Nickel base super alloys can meet these demands to a large extent. However, their excellent corrosion resistance and heat resistance as well as hardness and wear resistance have an adverse effect on the machinability with geometrically defined cutting edges. High local thermal and mechanical stress leads to short tool life and long non-productive time for the tool change. Along with a 90% decrease of cutting speed in comparison to conventional steel machining, cutting of nickel base super alloys demands for more efficient machining processes. One attempt to reduce thermal loads of the tool is machining with rotary tools, where a round indexable insert is mounted on a rotating axis. While machining the workpiece, the rotation of the cutting insert constantly exchanges the active cutting edge section. This allows for a better cooling of the temporarily inactive sections. Also tool wear is distributed equally along the circumference instead of using discrete positions only.In this paper two different types of rotary tools, a self-propelled rotary tool (SPRT) and an actively driven rotary tool (ADRT), are presented. In a series of experiments the influence of the modification of process parameters, penetration angle and tool rotation to the characterization of the surface area of the workpiece, stability of the cutting process and economic efficiency was investigated. Finally a process model was developed as a user-oriented guideline for turning the nickel base super alloy Inconel 718 with rotating indexable inserts.