A ductile iron of ~3.5 wt.% C and ~2.8 wt.% Si was austempered at 420 C for 0.5, 1, 2 and 3 h. These upper bainitic austempered ductile iron (ADI) specimens were then eroded by Al2O3 particles of ~275 μ grit size under the average particle velocity of 73 m s -1. According to the experimental results, 0.5 h austempered specimen, which contains largest amount of retained austenite and no austempered carbide, is more erosion resistant than the other ADI spicemens and the same cast iron of other common matrix structures. To increase the austempering time will induce brittle cracks at normal impact and shift the impact angle of maximum erosion rate to a higher one. The results also indicate the formation of ε-carbide upon particle impingement. Retained austenite is not the only phase to be transformed during the erosion process.
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