Numerical and experimental study of flowing and spreading of silver-based filler metal droplet on different substrates during laser brazing process

Abstract

In this study, a finite volume model was constructed to study the wetting, spreading, and flowing behaviors of silver-based filler metal droplet in laser brazing. The solidification and melting, multiphase flow, and heat transfer models were employed to simulate laser brazing process of Inconel 718, Inconel 600, 321 Stainless Steel, and 410 Stainless Steel substrates with silver-based filler metal. The volume of fluid (VOF) method was used to trace the free surfaces of the multiphase system. The enthalpy-porosity technique was employed to model the solidification and melting processes. Gravity force, buoyancy force, and Marangoni convection were considered in the model. The effects of variations in laser power, speed, and pulse width on the wetting, spreading, and flowing of the filler metal were evaluated. The conservation equations of energy, momentum, and mass are solved and the temperature distribution, volume fraction, and liquid fraction were calculated using fluent software. Finally, the calculated and experimental geometry profiles were compared. The simulated results show that wetting, spreading, and flowing behaviors of the silver-based filler metal can be predicted by this model in laser brazing process. The silver-based filler metal droplet wets and spreads on Inconel 718, Inconel 600, 321 S.S, and 410 S.S substrates and simultaneously infiltrates into the 0.15-mm joint gap with the lapse of time. The calculated geometry profiles show good agreement with experimental results.