Name: FRANCISCO ANTÓNIO FORTES BORGES
Type: MSc dissertation
Publication date: 10/10/2018
Advisor:
Name |
Role |
|---|---|
| MARCELO CAMARGO SEVERO DE MACÊDO | Advisor * |
Examining board:
| Name |
Role |
|---|---|
| MARCELO CAMARGO SEVERO DE MACÊDO | Advisor * |
Summary: Recent studies show that the welding of duplex stainless-steel sheets with preheating allows a more efficient control of the phase balance, thus providing better characteristics of the welded region. However, welding promotes microstructural changes that include the modification in the balance between ferrite and austenite, which theoretically should be around 50 %, in addition to the precipitation of secondary phases, such as the phase 𝜎 and the chromium nitride. In this context, the objective of this work is to evaluate the microstructural changes and the corrosion resistance of duplex stainless steels subjected to welding process. The autogenous GTAW welding process was performed on SAF2205 stainless duplex plates exposed to room temperature and preheated to 200∘C and 300 ºC.
After the welding, the plates were sectioned, prepared for the metallographic analysis of the morphology of austenite formed and for the quantification of the phases. The microstructural characterization was evaluated by optical microscopy and scanning electron microscopy (MEV). Besides this, double-cycle potentiodynamic electrochemical reactivation (DL-EPR) tests was performed to evaluate the corrosion resistance of the steel. The results showed the presence of grain - bound allotriomorphic austenite, Widmanstätten austenite and intragranular austenite. It was observed that the preheating temperature and the shielding gas influenced the microstructural balance and corrosion resistance. It was also verified, no evidence of pitting corrosion in samples immersed in saline solution.
Keywords: Duplex Stainless Steel UNS S31803, GTAW Welding, temperature of preheating, Corrosion.
