Embrittlement of austempered ductile iron caused by contact with water and other liquids

Abstract

Recent research has reported that austempered ductile irons (ADI) suffer a marked embrittlement when the material is tested in tension with its surface in contact with water. The objective of this investigation is to verify that embrittlement phenomenon, and to characterise the behaviour of several strength grades of ADI. The embrittlement effect of other wetting agents is also investigated. The results verified prior studies. A noticeable decrease in UTS and elongation takes place when ADI samples of grades 2 to 4 are tested immersed in water. The embrittlement effect is not affected by the concentration of protons in water. Embrittlement of ADI was also found when testing in contact with isopropyl alcohol and SAE 30 lubricant oil. A very strong wetting agent (WD40TM oil) does not cause embrittlement. Pearlitic matrix ductile irons also suffer embrittlement in contact with water, while ferritic matrix ductile irons of the same chemical composition, do not suffer embrittlement. The present study advances in the characterisation of the embrittlement of ADI, and identifies new embrittling liquids, but does not provide a definite explanation for its causes.