Effects of Filler Metals on Heat-Affected Zone Cracking in IN-939 Superalloy Gas-Tungsten-Arc Welds

AbstractA 50.8-mm-deep gas tungsten arc weld was made with matching filler metal in cast Haynes 282 alloy. The narrow-gap joint was filled with 104 weld beads. Visual and dye-penetrant inspection of cross-weld specimens indicated that the cast base metal contained numerous casting defects. No visible indications of physical defects were found in the weld deposit. The weld heat-affected zone was characterized by microcracking and localized recrystallization. The cause of the cracking could not be determined. Hardness testing showed that a softened region in the as-welded heat-affected zone was nearly eliminated by post-weld heat treatment. Tensile testing up to 816 °C showed that cross-weld specimen strengths ranged from 57 to 79% of the cast base metal tensile strength. The stress-rupture strengths of cross-weld specimens are within 20% of base metal reference data. Failures of both tensile and stress-rupture specimens occurred in the base metal.

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Postweld solution annealing effects on the ductility of ni-co-cr-base alloy gas tungsten arc welds

Journal of Materials Engineering and Performance ◽

10.1007/bf02646914 ◽

1996 ◽

Vol 5 (6) ◽

pp. 784-790

Author(s):

C.- S Lim ◽

K.- K Baek

Keyword(s):

Base Alloy ◽

Solution Annealing ◽

Gas Tungsten Arc ◽

Annealing Effects ◽

Gas Tungsten ◽

Gas Tungsten Arc Welds

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Evaluation of Liquation Cracking Behavior and Susceptibility in Heat-Affected Zone of CM247LC Superalloy Welds for Turbine Blade Application

Korean Journal of Metals and Materials ◽

10.3365/kjmm.2020.58.12.875 ◽

2020 ◽

Vol 58 (12) ◽

pp. 875-886

Author(s):

Ye-Seon Jeong ◽

Kyeong-Min Kim ◽

Uijong Lee ◽

Hyungsoo Lee ◽

Seong-Moon Seo ◽

...

Keyword(s):

Turbine Blade ◽

Heat Affected Zone ◽

Solidus Temperature ◽

Hot Cracking ◽

Liquation Cracking ◽

Cracking Behavior ◽

Gas Tungsten Arc ◽

Constitutional Liquation ◽

Gas Tungsten ◽

Eutectic Colony

In this study, the weldability of the as-cast CM247LC superalloy for turbine blade applications was metallurgically evaluated in terms of its hot cracking behavior and susceptibility. For this purpose, a real blade was manufactured using a directional solidification casting process, and gas tungsten arc welding was performed at the tip and cavity of the upper blade. Hot cracking was confirmed in the heat-affected zone (HAZ) of gas tungsten arc welds, and the cracks were characterized as liquation cracks, since a cobble or dropletshaped crack surface consistent with a liquid film was clearly confirmed. Microstructural analysis of the cracking surface and thermodynamic calculations helped elucidate the metallurgical mechanisms of the liquation cracking. In other words, the cracking was attributed to liquation of the γ-γ’ eutectic colony and the constitutional liquation of the MC-type carbides: these phases existed in the as-cast microstructure. In particular, it was calculated that liquation of the γ-γ’ eutectic colony during welding occurs at least at 1488 K and that constitutional liquation of MC-type carbides begins at 1411 K, while the equilibrium solidus temperature of the CM247LC alloy is 1530 K. Finally, the liquation cracking susceptibility was quantitatively evaluated through a spot-Varestraint test, and it was confirmed for the first time that the higher susceptibility of as-cast samples can be suppressed by employing a pre-weld heat treatment such as solution treatment.

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