The Experimental Investigations into Dry Turning of Austempered Ductile Iron

Abstract

Austempered ductile iron (ADI) formed by austempering of nodular cast iron (NCI). ADI has good mechanical properties due to the matrix of ausferrite.Use of carbide forming elements such as molybdenum and manganese while alloying form carbide. This carbide segregates towards cell boundaries during casting and form carbide in metal matrix. When high normal force is applied to ADI while machining, austenite on surface undergoes strain induced transformation (SIT) and form martensite. This transformation right in front of tool face makes it more difficult to machine. These issue reducing tool life significantly and making hurdle for further applications of ADI.In the present work, experimental investigations have been carried out into dry turning of ADI using response surface methodology(RSM) with central composite design(CCD). The performance of cemented carbide tool while machining ADI (austenitised at 850 °C for 2 hr, austempered at 350 °C for 1 hr) has been presented. The effects of speed, feed and depth of cut on cutting force, surface finish and microhardness have also been investigated with surface plots. The adequacy of these models has been checked by using analysis of variance. The predictability of main cutting force has been found to be greater than 95 %. The R- squared value for surface roughness model has found to be 0.9288. The main cutting force found to be influenced mainly by depth of cut while, the surface roughness by cutting speed.