Name: Artur Pratti de Barros
Type: MSc dissertation
Publication date: 30/03/2016

Namesort descending Role
Marcelo Camargo Severo de Macêdo Advisor *

Examining board:

Namesort descending Role
Eduardo Ariel Ponzio External Examiner *
Marcelo Camargo Severo de Macêdo Advisor *
Temistocles de Sousa Luz Internal Examiner *

Summary: This paper studied the effect of exposition to 475 °C during short periods of time, in the localized resistance corrosion and in mechanical resistance of steels UNS S32304, S31803 and S32750, the formation of alpha prime phase (α') after exposition to 475 °C was followed through electrochemical techniques potentiodynamic reactivation double loop (DLEPR) and electrochemical impedance spectroscopy, beyond the microhardness test.
The samples were heat treated at 475 °C during 4, 8 and 12 hours to provoke the precipitation of alpha prime phase. The tests of DL-EPR and electrochemical impedance spectroscopy were performed in 2 M H2SO4 solution + 0.5 M NaCl + 0.01 M KSCN.
Through the tests of DL-EPR was verified a peak of reactivation only for a sample of steel UND S32304 treated for 8 hours, for the other samples there weren’t a reduction of resistance to corrosion, but, through the analyze of activation current density, it was noticed the there was a reduction of resistance to corrosion of the treated samples. The tests of microhardness also showed changes to the heat treated, increasing the values of microhardness related to de condition as received. And finally, through the test of electrochemical impedance spectroscopy, it was analyzed the resistance to corrosion located in each situation. The UNS S32304 alloy showed the worst resistance to corrosion and the UNS S32750 alloy showed the best resistance to corrosion.

Keywords: Duplex Stainless Steel, UNS S32304, UNS S31803 and UNS S32750, embrittlement at 475
°C, Alpha prime.

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