The solidification and corrosion behaviour of austempered chilled ductile iron

This paper presents the results obtained and the deductions made from a series of corrosion experiments involving austempered chilled ductile iron containing 0.1% Mo and Ni contents varying from 1.0 to 2.5%. By using copper chills of different thickness, the effect on the corrosion resistance of varying the chill rate was examined. The corrosion tests employed were the weight-loss method according to ASTM G67–80 standards. The microstructure of the corrosion products were also examined. The corrosion resistance was found to increase significantly with increase in Ni content and rate of chilling. Nevertheless, even with a high Ni content, pitting was detected in the initial stages of most of the tests. Generally, the corrosive attack was found to be most severe during the initial stages of each test but it invariably decreased to a very low value in the later stages due to the formation of an adherent protective layer on the metal surface.