Name: André Canal
Type: MSc dissertation
Publication date: 31/08/2017
Advisor:

Namesort descending Role
Marcelo Camargo Severo de Macêdo Advisor *

Examining board:

Namesort descending Role
Juan Manuel Pardal External Examiner *
Marcelo Camargo Severo de Macêdo Advisor *
Sérgio Souto Maior Tavares Internal Examiner *
Temistocles de Sousa Luz Co advisor *

Summary: Duplex stainless steels (AIDs) belong to a group of materials of high mechanical and corrosion properties performance. These achievements have been investigated by several works on the application of the cladding weld with these materials due to the greater pitting resistance equivalente number (PREN) than conventional austenitic stainless steels and their lower cost compared with superalloys. During the deposition process the cooling rate can influence the microstructural balance (δ and  ) and the incidence of deleterious phases, which can decrease the performance of the deposited material. In this work the optimization of the parameters of the Double Loop Electrochemical Potentiokinetic Reactivation (DL-EPR) for evaluating quantitatively the effect of the dilution on the localized corrosion resistance of cladding of UNS S39209 deposited by GTAW welding with cold wire on ASTM A36 steel. The microstructural characterization was performed by optical microscopy before and after the corrosion tests. The efects of the scanning rate and concentration of the depassivator HCl in the solution on the relationship between activation and reactivation currents, which quantifies the corrosion resistance, were investigated. The results demonstrated that the solution of 33% H2SO4 + 0.5% HCl and scan rate of 1.5 mV/s can characterize the interactions between precipitation and chromium depletion of the deposited material. A decrease of the localized corrosion resistance was observed for higher austenite contents. The presence of secondary austenite and chromium nitrides was detected in the specimen of lower dilution. In the intermediate dilution specimen only chromium nitrides were observed. However, these specimens shown a lower degree of sensitization than the specimen with the highest dilution.

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