Effect of Different Austempering Temperatures on Wear Properties of Ductile Iron

Austempered ductile iron (ADI) because of its very interesting properties obtained after austempering process such as high strength, good toughness and low weight and low price has been considered in automotive and military industries. Since mechanical properties of ADI can be improved by precise control of heat treatment parameters. In this study the effect of different austempering temperatures on the wear properties of ADI irons has been studied. In this experiment, the samples of ADI iron were austenitized at 927 °C for 2 hours and then it was under austempering process for 2 hours at a range of 240°C to 400 °C and the effect of different temperatures on tribiological behavior and wear resistance of cast iron have been discussed. In this study, an optical microscope, XRD and SEM, has studied the transformation kinetics and its relationship to the microstructure and to evaluate wear surfaces an SEM electron microscope has been used. Sliding friction tests was done in a dry state by pin device on the disc; then friction coefficient and the wear value was measured and the relationship between the amount of residual austenite and the amount of weight loss due to abrasion has been studied in order to determine the best range of temperature for the best wear resistance. The results revealed that alloy besides having a combination of desirable mechanical properties as well as good wear behavior. In fact, austerity microstructure (ferrite blades in austenite field) along with the amount of residual austenite is considered as the main factor of increasing the strength and high wear resistance of this alloy. The results also indicated that the hardness and wear resistance decreases by increasing austempering temperature.