An Experimental Study on Machinability of Austempered Ductile Irons During Dry Turning by Ceramic Cutting Tools

Experimental investigation on the dry-turnned machinability of austempered ductile iron (ADI) samples using CC650 ceramic cutting tools were carried out in this paper, in which ADI samples are isothermally quenched at 300°C, 350°C, 400°C (hereafter referred as ADI300, ADI350, ADI400, respectively), chip morphologies were also characterized using scanning electron microscope (SEM).Results showed that they own different machinabilities based on the analysis of cutting forces and chip characteristics, strongly implying that ADI350 sample exhibits a relatively improved machinability while its mechanical properties are excellent. However, the cutting force of ADI400 is largest due to its lowest strength, hardness and toughness. The chips of ductile iron (DI) are continuous, while the chips of ADI present segmented and less coiled. The shear localization in the primary and secondary shear zone of ADI chips are correlated with the cutting forces and the wear rate of cutting tools. High carbon austenite transform into marten site due to transformation induced plasticity (TRIP) mechanism during the machining operation lead to an increase in cutting forces and a decrease of machinability.