The Effect of Cutting Speed and Depth of Cut on Surface Roughness During Machining of Austempered Ductile Iron

Abstract

Austempered Ductile Iron (ADI) is a relatively novel material to the industrial market and it is often reported that ADI is a difficult material for machining. This work mainly focuses on machinability studies of ADI. The Ductile Iron (DI) was austempered at 250 °C for different durations and the process window for austempering was established by studying the microstructure. The microstructural characterization of the material was done using optical microscopy, SEM and XRD. The samples austempered as per the process window were then subjected to turning using a TiAlN-coated tungsten carbide insert to study the effect of cutting parameters, namely the cutting speed & the depth of cut. The effect was investigated in terms of the surface roughness obtained. It has been observed that increasing cutting speed results in decreasing of surface roughness and improvement in surface quality. The surface quality deteriorates with decreasing the cutting speed. Based on the observations it is concluded that when ADI is subjected to turning with TiAlN-coated tungsten carbide insert, the combination of a depth of cut of 2 mm and feed rate of 0.1 mm/rev results in the best surface quality when the cutting speeds in the range 150–200 m/min are employed. The observed machinability behaviour was investigated in light of the microstructure of the material obtained under the given austempering conditions and a structure–property co-relation was established between the two. High-speed cutting with deeper depth of cut not only reduce machining expenses by increasing production volume and rate, but also results in good surface quality of machined parts.