TLP-brazing of nickel-numerical modelling and experimental verification

Isothermal solidification during TLP-brazing of nickel using Ni-11 wt%P filler metal is modelled and the output of the modelling study is validated directly using actual brazed test samples. There was good correspondence between the experimental and calculated results for isothermal solidification during TLP-brazing of single crystal nickel base metal. The rate of isothermal solidification during brazing was strongly affected by the grain size of the nickel base metal (faster isothermal solidification rates occurred with the fine-grained nickel base metal). The isothermal solidification process is directly influenced by liquid penetration at grain boundary regions. This liquid penetration effect occurs due to the energy balance between the solid-liquid interface and the grain boundary energy. Decreasing the base metal grain size increases the apparent mean phosphorous diffusion coefficient in solid nickel and this qualitatively explains the increased isothermal solidification rate in fine-grained base metals.