Optimization and modeling of sinter-brazing of porous copper-based composites joined to a wrought steel substrate

Sinter-brazing of a powder-metallurgy porous copper-based composite to a wrought steel substrate was investigated. Two commercial Cu-based filler metals (Hi-Temp 548 disk and CDA 521) and different heating profiles were evaluated to identify a process window that maximizes joint performance while limiting wicking of the molten filler into the open porosity. Peak temperature (1010–1020 ◦C) and holding time (5–10 min) were varied under N2. Shear testing and metallography show that increasing peak temperature or holding time reduces joint shear strength due to excessive infiltration of the filler and associated microstructural coarsening. The maximum joint shear strength (8.76 ± 0.5 MPa) was obtained using Hi-Temp 548 at 1015 ◦C with a 5 min hold. A three-dimensional CFD model based on the volume-of-fluid method and the continuum surface-force formulation was developed to predict filler infiltration into the porous compact. The predicted infiltration depth (415 μm) agreed with experiments (389 μm) within 7%. Parametric simulations indicate that infiltration increases with decreasing filler density and viscosity and with increasing holding time, with holding time being the dominant factor.