Embrittlement of austempered ductile iron on contact with water-testing under applied potential

Recent reports indicate that austempered ductile iron (ADI) is embrittled on contact with water. This environmentally induced cracking (EIC) phenomenon is not clearly understood. The objective of this investigation is to study the behavior of ADI on tensile testing in aqueous media under controlled electrochemical conditions, aiming to identify whether the embrittlement can be either inhibited or enhanced by stimulating or avoiding the reduction of protons on the sample's surface. The results suggest that the EIC of ADI is not an electrochemical phenomenon, since neither cathodic nor anodic applied potentials have been able to inhibit embrittlement. Local wetting of the tensile sample surface has been used to localise fracture. Early stages of fracture propagation have been shown to take place by cleavage. Later, the fracture mode changes to quasi-cleavage, a much more ductile mechanism, as it grows far from the fracture initiation site. (C) 2003 Kluwer Academic Publishers.