Abstract
This paper discusses the mechanism of environmental assisted cracking (EAC) of an austenite/ferrite duplex stainless steel in a 35 mass % MgCl2 solution at 363 K by measuring both the acoustic emission (AE) and corrosion potential fluctuation (CPF). We utilized a new fracture toughness testing device and measured the growth characteristics of macroscopic crack. The duplex stainless steel was found to suffer delayed fracture through the ferritic grains in this solution rather the active path corrosion (APC) type SCC in austenitic grains. We detected no clear CPF but strong AEs during the test. AE sources were located at the zone 1-3 mm from of crack tip or at the zone with high hydrostatic pressure at which micro crack of delayed fracture took place. Source wave analysis of AE revealed the fast brittle micro fractures. Fractographic study supported the brittle fracture of ferritic phase by hydrogen and subsequent ductile fracture of the austenitic phase.
