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CSME 2018/04
Volume 39 No.2
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131-143
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Microstructure and Intergranular Corrosion Resistance Evaluation of Alloy 82 Weldments
Hwa-Teng Leea and Te-Chen Liu a
aDepartment of Mechanical Engineering, National Cheng Kung University, No.1, University Road, Tainan 701, Taiwan, R. O. China
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Abstract:
An investigation is performed into the grain boundary character distribution (GBCD), degree of sensitization (DOS), and intergranular corrosion (IGC) resistance of Alloy 82 overlay welds prepared using a manual gas tungsten arc welding (GTAW) process. Four different weldments are considered, namely as-welded (AW), sensitized (AW+SEN), solution-annealed (SS), and solution-annealed and then sensitized (SS+SEN). The results show that approximately 67.9% and 212.4 cm/cm2 of the grain boundaries in the weldments were prepared by GTAW process found AW specimens are high-angle boundaries (>15°). These boundaries prompt the precipitation of fine Cr-carbides during sensitization treatment, and therefore cause the formation of Cr-depletion zones close to the grain boundary. Consequently, the AW+SEN weldment has a high DOS. By contrast, AW+SEN welds are processed using a laser surface melting (LSM) technique with a continuous CO2 laser beam and scanning speeds in the range of 0.8~1.2 m/min. It is shown that the LSM treatment could improve IGC and pitting corrosion resistance of the overlay weld mainly by reducing the amounts of fine precipitates along the subgrain boundaries of sensitized weld.
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Keywords: Alloy 82 weld, laser surface melting (LSM), intergranular corrosion (IGC), pitting corrosion
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*Corresponding author; e-mail: htlee@mail.ncku.edu.tw
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©
2018
CSME , ISSN 0257-9731
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