Efeito da velocidade de resfriamento após tratamento térmico em alta temperatura na resistência à corrosão localizada do aço UNS S31803

Abstract

Duplex Stainless Steel have both phases ferrite and austenite in his microstructure in almost equal proportions, allowing it to have great strength corrosion and mechanical resistance , being extremely used in petrochemical and chemical industries. When exposed to high temperatures they are subject to microstructural changes making his properties to be modified. In this work localized corrosion resistance of the duplex stainless steel UNS S31803 heat treated by high temperature(1300◦C) for 30 minutes followed by different cooling rates is studied.Somesamples were solution treated at 1000◦C for 1 hour and fast cooled after the high temperaturetreatment.A wide range of microstructures,with differents morphologies and phase proportions, were obtained by this way, also this microstructural changes during cooling process have promoted the precipitation of deleteriusphases such as nitrides and sigma, making the corrosion strength to be altered.The intergranular corrosion resistance wasmeasured with DL-EPR technique,and pitting corrosion was made using potentiodynamic polarization both according to the standard ASTM.Besides these tests were made microhardness analysis,optical microscopy andscanning electron microscopy of the samples.