Innovative Nano-transient liquid phase bonding of Inconel 718

Ni nanoparticles (NPs) and nanowires (NWs) are compared as brazing filler metals for joining Inconel 718. Nanowires significantly enhance the strength of brazed joints compared to nanoparticle joints (270 MPa). Joints formed with a pure nanowire pellet and a nanowire-nanoparticle mixed pellet yielded average lap shear bonding strengths of 319.2 MPa and 370 MPa, respectively. The experiment displayed that the contact angle in brazing with nanoparticles is higher than that with nanowires. A modified Hart’s equation is also proposed for predicting the effective interdiffusion coefficients of nanomaterials that accounts for surface diffusion in addition to lattice and grain boundary diffusion. The diffusion coefficients calculated by the modified Hart’s equation are consistent with the values determined by Sauer-Friese analysis for nanoparticles, but for nanowires the diffusion coefficients determined by Sauer-Friese are mainly controlled by the grain boundary diffusion, significantly higher than those predicted by the modified Hart’s equation due to size-dependent transient liquid phase diffusion. This explains the enhanced brazing strength with nanowire fillers.