Caustic stress corrosion cracking of a graphite cast iron component

Abstract

This paper presents failure analysis of an ex-service cast iron component exposed to aggressive caustic solutions during Bayers process for alumina processing. The cracks and the neighbouring areas in the ex-service samples were examined using conventional metallography, scanning electron microscopy (SEM), the extraction replica technique in the transmission electron microscope (TEM) and Auger electron spectroscopy (AES). The features include intergranular stress corrosion cracking and grain boundary embrittlement ahead of the crack-tips. The paper also argues the possibility of hydrogen-assisted crack propagation.