Microstructure and Strength of γ-TiAl Alloy/Inconel 718 Brazed Joints

Elsa W. Sequeiros; Anibal Guedes; Ana Maria Pires Pinto; Manuel F. Vieira; Filomena Viana

doi:10.4028/www.scientific.net/MSF.730-732.835

Paper Titles

Influence of Additional Alloying Elements on Corrosion Resistance of Hot Dip Galvanised Steels
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Metallographic Characterization of Friction Stir Channels
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Microalloying of the Zinc for Obtaining Masteralloys or Correction of the Chemical Composition for the Zn Baths in the Galvanizing Process
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Microstructural Evolution during the Directional Transient Solidification of a Hypomonotectic Al-0.9wt%Pb Alloy
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Microstructure and Strength of γ-TiAl Alloy/Inconel 718 Brazed Joints
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Assessment of Cooling Conditions of a Continuous Casting Machine for Steel Billets Based on Surface Temperature Measurements
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Process Stability Evaluation of Manual Metal Arc Welding Using Digital Signals
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SMA (NiTi): The Coupling between Time, Temperature and Cycling Frequency
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Solid State Transformations and Equilibrium Crystal Structures of an Au-Cu Alloy with Shape Memory Effect
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Microstructure and Strength of γ-TiAl Alloy/Inconel 718 Brazed Joints

Abstract:

Intermetallics and superalloys brazing development is a current topic owing the extending use of these alloys in industrial applications. In this work a γ-TiAl alloy was joined to Inconel 718 by active metal brazing, using Incusil-ABA as filler. Joining was performed at 730 °C, 830 °C and 930 °C, with a 10 min dwelling time. The interfaces were characterized by Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS) and Electron Backscatter Diffraction (EBSD). For all processing conditions, the reaction between the base materials and the braze alloy produced multilayered interfaces. For all processing temperatures tested (Ag), (Cu), AlNi₂Ti and AlCu₂Ti were identified at the interface. Raising the brazing temperature increased the thickness of the interface and coarsened its microstructure. The increase of the extension of the interface was essentially due to the growth of the reaction layers formed near each base material, which were found to be mainly composed of intermetallic compounds. The mechanical behavior of the joints, at room temperature, was assessed by microhardness and shear tests. For all processing conditions the hardness decreases from periphery towards the Ag-rich centre of the joints. Brazing at 730 °C for 10 min produced the joints with the highest average shear strength (228±83 MPa). SEM and EDS analysis of the fracture surfaces revealed that fracture of joints always occurred across the interface, preferentially through the hard layer, essentially composed of AlNi₂Ti, resulting from the reaction between Inconel 718 and the braze alloy.