Performance analysis of hard inserts in finish turning Inconel 718

Abstract

Nickel based super alloys are widely used in the aerospace industry, in particular, in the hot sections of gas turbine engines, due to their high temperature strength and high corrosion resistance. Inconel 718 is the most extensively used nickel based alloy and a well known difficult-to-cut material. Its petite thermal conductivity and specific heat result in high cutting temperatures, which are responsible for being difficult to machine. Efficient machining of aero engine alloys depends on an informed choice of materials, cutting speed, processing time and the functionality of the machined component for an economic production. In finish turning Inconel 718, the effects of flank wear of the cutting tool are considered most critical, as it directly determines the surface finish and properties of the subsurface layer. Therefore, understanding of the tool wear behavior and the capability of predicting it is the key to successful process control and optimization. To work towards this goal, the effect of different hard cutting inserts on the cutting variables and process parameters are first investigated using Response Surface Methodology (RSM). Furthermore, the developed models are optimized by determining the best combinations of input process parameters in order to produce an excellent surface quality and minimum flank wear. The uses of different hard inserts such as uncoated carbide, coated carbide, ceramics and cermets to cut this kind of material have been investigated. The performance in the finish turning operation is discussed on the focus of failure modes, wear mechanism and effect of cutting parameters on the responses. From the analysis, it is observed that the cutting speed has the strongest effect on the surface roughness and flank wear among the selected parameters newline