The effect of induction surface hardening process on mechanical properties of the austempered ductile iron

In this study, the effect of induction surface hardening heat treatment on the microstructure and fatigue strength of austempered ductile iron has been investigated. For this purpose, GGG70 grade alloyed ductile iron, specimens was austenitized at 900 °C for 90 min and then transformed into salt bath held 375 C° for austempering for a period of 120 min. Then austempered fatigue test specimens were subjected to high frequency induction surface hardening heat treatment. For a comparison reason, as-cast specimens were also subjected to Induction surface hardening treatment. The fatigue strength of the specimens was determined by rotary-bending fatigue test. The experimental results showed that, the fatigue strength of austempered specimens are higher than those as cast specimens. In addition, induction surface hardening process of austempered specimens increased fatigue strength approximately 25 % compared those austempered specimens.