Study of wear behaviour of ductile iron subjected to two step austempering

Abstract

An investigation was carried out to examine the influence of two step austempering on microstructural parameters and the wear behaviour of austempered ductile iron. Ductile iron was austenitised at 900 C for 30 min, and then austempered successively at two different temperatures. It was first austempered at 300 C for different durations from 2 min to 30 min and subsequently austempered at 400 C for 2 h, after which it was quenched to room temperature. Resulting microstructures were characterised through optical microscopy and X-ray diffraction. Mechanical properties were studied through hardness measurement and tensile testing. Wear studies were carried out using a pin-on-disc machine. Wear rate was found to decrease with increasing time at the first step temperature of 300 C. At short austempering times at 300 C, the amount of austenite was instrumental in improving the wear resistance through formation of deformation induced martensite. Wear rate was found to depend on yield strength, austenite content and its carbon content. Carl Hanser Verlag GmbH & Co. KG.