Effects of Grain Boundary Microconstituents on Heat-Affected Zone Cracks in a Mar-M004 Weldment

Repair-welding of a cast Mar-M004 superalloy by gas tungsten arc welding was performed. Liquation cracks of the heat-affected zone (HAZ) in a Mar-M004 weldment were closely related to the presence of low-melting constituents along the solidified boundaries in the weld. The metal carbides (MC), M3B2...

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Bibliographic Details
Published in:Metals (Basel ) 2018-04, Vol.8 (4), p.201
Main Authors: Chen, Tai-Cheng, Cheng, Yi-Hsin, Tsay, Leu-Wen, Shiue, Ren-Kae
Format: Article
Language:English
Subjects:
Arc heating
boride
Borides
Cracks
Gas tungsten arc welding
Grain boundaries
Hafnium
Heat affected zone
intermetallic compound
Intermetallic compounds
liquation crack
Mar-M004 superalloy
MC carbide
Metal carbides
Metals
Precipitates
Repair
Solidus
Superalloys
Zirconium compounds
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Summary:Repair-welding of a cast Mar-M004 superalloy by gas tungsten arc welding was performed. Liquation cracks of the heat-affected zone (HAZ) in a Mar-M004 weldment were closely related to the presence of low-melting constituents along the solidified boundaries in the weld. The metal carbides (MC), M3B2 and M5B3 borides, Ni7(Hf,Zr)2 intermetallic compounds, and γ-γ′colonies were found at the interdendritic boundaries. Fine boride precipitates mixed with intermetallic compounds in lamellar form were more likely to liquate during repair-welding. The melting of borides and intermetallic compounds in 1180 °C/4 h treated samples confirmed the poor weldability of the Mar-M004 superalloy due to enhanced liquation cracking. In addition to boride formation, fractographs of liquation cracks revealed strong segregation of B element in carbides and intermetallics, which might further lower the solidus temperature of the repair weld.
ISSN:2075-4701
2075-4701
DOI:10.3390/met8040201