The effect of reducing the austempering time on the fatigue properties of austempered ductile iron

The effect of reducing the austempering time on the high-cycle fatigue behavior of austempered ductile iron (ADI) has been investigated by subjecting samples to rotating bending and fatigue crack propagation tests. Starting from the same cast iron, two distinct types of ADI were austempered at the same temperature of 360 °C but for different austempering times, which resulted in two materials whose main difference was the content of carbon in austenite. The first sample was austempered for 1.5 h, while the second was austempered for only 0.6 h. The austenitizing cycle (900 °C, 1.5 h) was the same for both ADIs. Therefore, we investigated the influence of the mechanical stability of austenite in the initiation and propagation of fatigue cracking. Reducing the austempering time increased the fatigue life and did not affect the mechanical properties or the rate of fatigue crack propagation. Reducing the austempering time increased the time to fatigue crack nucleation in ADI in addition to its economic and environmental benefits.