Cracking of martensitic alloy EP-823 under controlled potential

The susceptibility of martensitic Alloy EP-823 to stress corrosion cracking was evaluated with and without an applied cathodic potential using the slow-strain-rate (SSR) testing technique. The magnitude of the applied potential was based on the corrosion potential determined by cyclic polarization. The cracking susceptibility in an acidic environment at different temperatures was expressed in terms of the true failure stress (σ_f), time to failure (TTF), and ductility parameters, including percent elongation (%El) and percent reduction in area (%RA). The data indicate that the magnitudes of σ_f, TTF, %El, and %RA were reduced due to cathodic charging. The scanning electron microscopic evaluations of the primary fracture surface of the specimens used in SSR testing revealed a combination of ductile and brittle failures. Further, the secondary cracks at the gauge section of these specimens were characterized by branching.