Environment effect on the mechanical behaviour of a thermally treated superduplex UNS S32760.

The susceptibility to stress corrosion cracking (SCC) of a thermally treated (4, 10, 30 min at 950°C) superduplex UNS S32760, in a simulated petrochemical process environment, containing hydrogen sulphide and chloride (20%wt. NaCl + 0.1M Na2S2O3, 80°C), was evaluated using the slow strain rate tensile (SSRT) technique. At the end of the test, the samples gauge length section and the fracture surface were observed by optical microscope (OM) and scanning electron microscope (SEM). SCC susceptibility was also estimated by means of the ratio (R) between the percentage of elongation at fracture obtained by the SSRT test in two aggressive solutions and the percentage of elongation at fracture obtained in air. The results showed that the UNS S32760 treated for 10 min at 950°C was the most susceptible to SCC in the 20% NaCl solution containing 0.1M Na2S2O3