Implant Weldability Tests on Ductile Iron and Austempered Ductile Iron

摘要

Austempered Ductile Iron, which is an upgraded version of Ductile Iron, is a relatively recent addition to cast iron family. It is produced by an isothermal heat treatment of Spheriodal Graphite Iron. It possesses high strength-to- weight ratio, wear resistance, ductility coupled with excellent toughness, adequate machinability, design flexibility and cast ability. It is reported that Austempered Ductile Iron out-performs proprietary abrasion resistant steels at similar bulk hardness levels. Austempered Ductile Iron is produced by subjecting a ductile iron casting to an Austenitization soak followed by tempering in a salt bath. This offers an opportunity for dissolving the carbides formed in the as-cast condition. The microstructure produced in Austempered Ductile Iron is unique. Graphite nodules are surrounded by a matrix of bainite and ferrite with a high retention of austenite content. Austempered Ductile Iron finds wide applications in automobile sector like heavy truck components, gears and crankshafts. Other applications of Austempered Ductile Iron are in the fields of Construction, Mining, Agricultural, Defence and Power Plant components. Extensive literature survey carried out on Austempered ductile Iron indicates there is no information on its Weldability characteristics. It is necessary to ascertain weldability of these materials under restraint conditions so that these materials can be used for wide number of applications. In this investigation, Implant welding tests were carried out on ductile iron and Austempered Ductile Iron samples using E7018 and Nickel electrodes. Following were the conclusions made, the yield stress using nickel electrode for ADI produces the best weld.