Transient liquid phase bonding of Inconel 718 and Inconel 625 with BNi-2: Modeling and experimental investigations

In this study, a combination of direct experimentation and computational modeling approach was used to predict the time required to complete isothermal solidification during the transient liquid phase bonding of Inconel 718 and 625 superalloys, two most commonly used superalloys in aero-engine hot section components, with nickel based filler alloy, BNi-2. However, unlike conventional modeling, the diffusion of solute atoms was modeled by the Random Walk Modeling technique which can take into account the physical and chemical uncertainties associated with the transient liquid phase bonding experiments. The model equations for migrating solid/liquid interface and solute distribution approaches have been modified and presented in this article. Cumulative probability distribution and probability density function of predicted isothermal solidification times were calculated for different process conditions. The predicted isothermal solidification time range with different confidence levels has been verified with experimental data. Good agreement was observed. The times required for complete isothermal solidification were found to be significantly less than those of other nickel superalloys with different nickel based brazing fillers. Further, significant reduction of holding time was observed with increasing bonding temperature and with decreasing joint gap and no significant grain growth has been observed in the temperature range being investigated (1325–1394 K).