Shear strength/microstructure relationship for dissimilar IN738/IN718 TLP joints

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MBF20 interlayer, as a commercial foil, was used for TLP bonding of IN738/MBF20/IN718 system at different temperatures and times. Microhardness and shear strength tests were conducted for all the samples. Hardness profile across the joints made at 1050 and 1100 °C revealed the microstructure regions as isothermal solidification zone (ISZ), athermal solidification zone (ASZ), and diffusion affected zone (DAZ). With increasing bonding time at each temperature, hardness peak at the joint centerline was removed but the hardness peak at DAZ remained. Increase of joint’s shear strength, increase of ISZ hardness, and decrease of DAZ hardness with increasing bonding temperature and/or time were discussed according to the effect of Larson-Miller parameter. Partial liquation of the base metals at 1150 °C/60 min condition caused reverse trend for variation of hardness and joint’s strength with bonding temperature. Fracture path of the joints with incomplete isothermal solidification was seen through the centerline eutectics. This path for the joints with complete isothermal solidification was observed through the bonding zone and the DAZ phases.

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  • 06 January 2021

    The original version of this article unfortunately contained a mistake.


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The author would like to acknowledge Kermanshah Branch of Azad University for financial supports of this research.

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Correspondence to R. Bakhtiari.

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• Mechanical properties of TLP joints for IN-738/MBF-20/IN-718 system.

• Increase of joint’s shear strength and hardness with increasing bonding temperature.

• Discussion of this trend according to the effect of Larsson-Miller parameter.

• Reverse trend for variation of joint’s strength and hardness at 1150 °C.

• Shear fracture path of the joints through the bonding zone and the DAZ phases.

Recommended for publication by Commission XVII - Brazing, Soldering and Diffusion Bonding

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Bakhtiari, R., Yarmou Shamsabadi, A. & Alipour Moradi, K. Shear strength/microstructure relationship for dissimilar IN738/IN718 TLP joints. Weld World 64, 219–231 (2020).

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  • TLP bonding
  • IN718 superalloy
  • IN738 superalloy
  • MBF20 interlayer
  • Mechanical properties