Thesis (Ph.D.) - Cairo University - -Faculty of Engineering - Department of Metallurgical Engineering

This study aims at evaluating both pitting corrosion and microstructure of duplex stainless steel (2205) welded by (2209) as a filler before and after exposure to increased service temperatures. In this work selected welded samples were aged at different temperatures (650{u00B0}C, 850{u00B0}C, 950{u00B0}C and 1050{u00B0}C), in order to simulate heat exposure during processing or sevice stages. The results showed that the pitting corrosion rate increased in chloride environments with increasing aging temperature till 850{u00B0}C, afterwards pitting corrosion rate started to decrease and the joints restored their original pitting resistance at 1050{u00B0}C, by the increasing the aging to above 1050{u00BA}C, pitting resistance was found to decrease again. Also, The results showed that the amount of brittle phases increased as the temperature and holding time are increased in the temperature range (475-850{u00B0}C), then they dissolved to form ferrite phase again on increasing the temperatur above 850{u00B0}C. When the temperature reached 1050{u00B0}C all brittle phases completely dissolved and the ferrite to austenite ratio was restored. As the temperature increased to 1150 the ratio Þ/e was decreased due to increase of the ferrite phase. A correlation between different welding processes and aging times were also conducted

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