| Summary: | 碩士 === 國立成功大學 === 機械工程學系碩博士班 === 96 === This study investigated the microstructure and corrosion resistance of Inconel 600 Alloy weldments by GTAW process. The heat treatments of As-received Alloy 600 were stress relieved (SR) at 843℃ for 1 hour. Then Alloy 600 were treated with solution annealed (SA) at 1100℃ for 30 min and thermal treatment (TT) at 700℃ for 24 hours. Their corrosion resistance was evaluated by Huey test.
Compared to the microstructure in the heat affected zone of these weldments, there was weld decay zone in SA weldment. According to the temperature measurement, it took over 10 seconds to pass through the sensitization range (500~750℃), and the cooling-rate of this zone were between 25~32℃/sec. Cr-carbides precipitate along the grain boundary, and hence to decrease the corrosion resistance in this zone. There was, however, different microstructure in TT weldment. Because of TT heat treatment, Cr-depletion zone has recovery. This effect can prevent weld decay zone forming during welding. SR weldment has poorer corrosion resistance of base metal than the other two. Serious Intergranular corrosion happened (IGC) after 24 hours Huey test.
We may predict weld decay zone in SA weldment by welding thermal cycle. The weldment could be repaired to prevent rupture.
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