Metallurgical Engineering

Metallurgical Engineering

Effect of homogenization treatment on microstructural evolution of dissimilar TLP joints for FSX-414/MBF-80/IN-738 system

Document Type : Research Paper

Authors
Abbas Jahanbakhsh
Bijan Abbasi Khazaei
Reza Bakhtiari
Abstract
In this research, TLP bonding was used for dissimilar joints of IN-738/FSX-414 system using MBF-80 interlayer with the thickness of 50µm. TLP bonding was carried out at optimum condition (1150oC/5min) in a vaccuum furnace. Then, in order to refine the microstructure and increase the mechanical properties of the joints, homogenization treatment was carried out at 1175, 1200 and 1225oC for 1, 3 and 6 h. Optical microscope and scanning electron microscope (SEM) were used for microstructural studies and phase analysis was done using SEM/WDS analysis. Microstructural studies showed that homogenization at 1175oC/6h had no effect on removing the diffusion affected zone (DAZ) phases, but considerable reduction of these phases has occurred at 1200oC/1h. Homogenization at 1225oC for 1h caused formation of grain boundaries and secondary eutectic phases at the joint as well as coarsening of precipitates at the joint and base metal. Profile of alloying elements concentration across the joint showed that precipitation and coarsening of  at the base metal and diffusion of alloying elements were the controlling factors of homogenization. Considerable reduction in the slope of alloying elements concentration profile at 1200oC was due to the rapid diffusion through the grain boundaries of the joint. Therefore, the optimum microstructural features were seen at 1225oC/1h homogenization condition. 
Keywords
Transient liquid phase (TLP) bonding
Homogenization
Dissimilar joint
FSX-414 superalloy
IN-738 superalloy
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  • Receive Date 23 September 2014