Ductile iron specimens of ∼3.5 mass% C and ∼2.8mass% Si were austempered at 420°C for 0.5h∼24h. These upper bainitic austempered ductile iron (ADI) specimens were 90°-eroded by Al2O2 particles of ∼275 μ.m grit size under the average particle velocity of 73 m·s-1 to understand phase transformation at the erosion surface. According to the experimental results, the retained austenite content and the carbon content of bainitic ferrite decreases through phase transformation during erosion. After erosion, the retained austenite and the high carbon content bainitic ferrite form ε-carbide, another carbide and ferrite. The other austempering carbide of the remaining matrix also transforms into ε-carbide in the erosion process.
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