Effect of bonding time on the microstructure and isothermal solidification completion during transient liquid phase bonding of dissimilar nickel-based superalloys IN738LC and Nimonic 75

Joining of dissimilar nickel base superalloys IN738LC to Nimonic 75 by use of transient liquid phase bonding with Ni-15Cr-3.5B interlayer (MBF-80) was carried out at temperatures of 1080 degrees C, 1120 degrees C, 1150 degrees C and 1180 degrees C for different bonding times. Joint microstructure was surveyed by optical and scanning electron microscopy. Microstructural examinations showed those in short bonding times, the joint microstructure consists of continuous eutectic intermetallic phases and longer times lead to eutectic free microstructure. It was shown that bond shear strength increases with holding time increment. Fick's equations were used for prediction the time required for completion of isothermal solidification. It was seen that there was a good correspondence between the results of modeling and experimental data. (C) 2015 Elsevier B.V. All rights reserved.