Traditional machining of Austempered ductile iron (ADI): A review

Machining is one of the important fabrication process. Austempered Ductile Iron (ADI) has 10% less weight than Steel, good impact strength, up to 40% less cost than hardened steel forgings, better wear resistance than case hardened steels, excellent resistance to crack propagation etc. Although the above properties are advantageous, it has been assumed to be un-machinable by many manufacturers. This is mainly because of its high hardness values. ADI can be used for different automotive components like constant velocity joint, truck hub etc. The addition of alloying elements increases the hardenability of ADI and decreases the tool life while machining. The main problem faced while conventional machining of ADI is strain induced transformation which significantly reduces the life of tool. This paper deals with need for Austempered Ductile Iron, various grades of ADI, literature review related to machining response to different conventional machining process namely Turning, Milling and Drilling. The different input process parameters considered are cutting speed, depth of cut, machining response for different tool materials and tool geometry, with cutting force, surface finish being the output process parameter. Different strategies have been tried by various authors, viz., Machining prior to heat treatment, partial machining before and finishing after heat treatment and post heat treatment machining. Ceramic inserts, PVD coated and uncoated tools, whisker reinforced tools are tried for different machining process for this material.