Caustic stress corrosion cracking of a spheroidal graphite cast iron: Laboratory investigation

This paper presents the results of an experimental investigation into the stress corrosion cracking (SCC) of an engineering cast iron (namely a spheroidal graphite (SG) cast iron), in a highly caustic solution (namely synthetic Bayer liquor (SBL)) at high temperature. In order to ascertain experimental conditions under which plain iron - carbon materials may fracture predominantly by SCC in a caustic environment, slow strain rate testing (SSRT) was performed on carbon steel specimens, employing various combinations of strain rates and temperatures, in SBL and an inert environment of liquid paraffin. Under the conditions identified to be most conducive for caustic SCC of mild steel, specimens of the SG cast iron were subjected to SSRT in SBL and liquid paraffin, and the fracture behaviour was investigated by detailed fractography and microstructural characterisation.