Abstract

A combination of direct experimentation and computational modeling approach was used to predict the isothermal solidification times during the Transient Liquid Phase (TLP) Bonding of nickel superalloys, Inconel 718 and 625, and stainless steels, 410 and 321, with nickel based filler alloy, BNi-2. 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 TLP Bonding experiments. The model equations for migrating solid/liquid interface and solute distribution have been modified and presented in this thesis. Cumulative probability distributions and probability density functions of isothermal solidification times were calculated for different process conditions and compared with experimental data. Good agreement was observed when nickel superalloys and SS 321 were used as base alloys. However, it was found that both models, based on the assumption of 0.3 at% solubility of boron, underestimated the isothermal solidification time requirement for SS 410/BNi-2 at higher bonding temperatures due to the decreased boron solubility. Excellent agreement was observed when 0.2 at% boron solubility was used. Isothermal solidification times predicted by silicon diffusion model based on the EDS analyses were also in good agreement with the experimental data for this combination