On the Role of Grain Boundary Serration in Simulated Weld Heat-Affected Zone Liquation of a Wrought Nickel-Based Superalloy |
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Authors: | Hyun Uk Hong In Soo Kim Baig Gyu Choi Young Soo Yoo Chang Yong Jo |
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Affiliation: | (1) High Temperature Materials Research Group, Korea Institute of Materials Science, 797 Changwondaero Sungsan-gu, Changwon, Gyeongnam, 641-831, Republic of Korea |
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Abstract: | The effects of grain boundary serration on boron segregation and liquation cracking behavior in a simulated weld heat-affected
zone (HAZ) of a wrought nickel-based superalloy 263 have been investigated. The serrated grain boundaries formed by the developed
heat treatment were highly resistant to boron segregation; the serrated sample contained 41.6 pct grain boundaries resistant
to boron enrichment as compared with 14.6 pct in the unserrated sample. During weld thermal cycle simulation, liquated grain
boundaries enriched with boron were observed at the peak temperature higher than 1333 K (1060 °C) in both unserrated and serrated
samples; however, serrated grain boundaries exhibited a higher resistance to liquation. The primary cause of liquation in
this alloy was associated with the segregation of the melting point depressing element boron at grain boundaries. The hot
ductility testing result indicated that the serrated grain boundaries showed a lower susceptibility to liquation cracking;
the grain boundary serration led to an approximate 15 K decrease in the brittle temperature range. These results reflect closely
a significant decrease in interfacial energy as well as a grain boundary configuration change by the serration. |
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