Effect of austempering temperature on microstructure and properties of austempered ductile iron

The influence of austempering temperature on microstructure and properties of Austempered Ductile Iron were studied in this paper. The purpose was to improve comprehensive performance of Austempered Ductile Iron for adapting to slurry pump transflux parts. The nodularisation grade of graphite was 2-3 magnitude and the size of graphite was 6-7 magnitude. After austempered at different temperatures for 120 min, the microstructure mainly consisted of acicular ferrite, retained austenite and spheroidal graphite. With increasing austempering temperature, tensile strength improved firstly and then decreased, impact toughness increased, the wear resistance became worse, and the corrosion resistance increased. When the heat treatment process was 900°C × 90 min + 250°C × 120 min, the comprehensive performance was better (tensile strength: 1710 MPa, elongation: 2%, impact toughness: 40 J/cm2, Brinell hardness: 467 HBW, wear weightlessness rate: 0.17 mg/m) than the requirements in ASTM A897-06.