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Abstract
An investigation was carried out on transient liquid phase brazing of IN-738 superalloy with Ni–Cr–B filler. Conventional models used to model the Transient Liquid Phase (TLP) bonding process assume that boride precipitation does not occur during the joining process. However, a significant deviation from this assumption was observed in all brazed samples as extensive intragranular and intergranular precipitation of chromium and boron rich particles was observed to occur within the base alloy in regions beside the braze/ base metal interface. Application of two diffusion models to the isothermal solidification stage was successful in reasonably predicting the time required to achieve complete isothermal solidification of the liquid insert, which is vital in preventing the formation of deleterious centreline eutectic. Diffusion analysis showed that the boron rich particles formed as a result of substantial solute diffusion into the base metal before equilibration of the liquid–solid phases.
