Evaluation of machinability of austempered ductile irons in terms of cutting forces and surface quality

This study presents the results of machining tests carried out to determine the effect of microstructure and mechanical properties of austempered ductile irons (ADIs) on cutting forces and surface roughness. Specimens were prepared under different austempering times with the addition of Cu and Ni at various contents. Six different specimen groups were austenised at 900 °C for 90 min and then austempered in molten salt at 370 °C for 60, 90, 180 and 200 min. The results were evaluated after machining tests which were carried out in accordance with ISO 3685. Austempering heat treatment resulted in considerable improvement on the surface quality when compared to as-cast specimens while the changes in cutting forces remained at about 20% level for different specimens. In terms of both criterion, the best result was obtained from 60 min austempered and 0.7% Ni and 0.7% Cu added specimens.