Microstructural evolution and phase-dependent corrosion of Si₃N₄/316L joints using AgCuTi/Ag composite fiols

The microstructure evolution of Si₃N₄/316 L joint brazed with AgCuTi/Ag composite filler is investigated, and the typical microstructure of Si₃N₄/316 L joint is Si₃N₄/TiN+Ti₅Si₃/Ag-rich/Cu-rich+Fe₂Ti, NiTi+Ag-rich+Fe-rich/316 L. Further research on the corrosion resistance of the joint is warranted to build the relationship between microstructure and corrosion behavior. It is noteworthy that corrosion behavior is more likely to occur at the interface of seam/316 L by SEM analysis. The residual stress on the 316 L substrate is also concentrated on this region, playing an important catalytic role in corrosion behavior. The joint presents a shear strength of 100 MPa and excellent corrosion resistance when it is brazed at 900°C for 15 min. Moreover, the diffusion kinetic process of Fe element in the interface of filler/316 L is studied based on the Boltzmann-Matano model, and the activation energy is obtained for about 468 kJ/mol. Although the addition of the Ag layer into the seam decreases the non-corrodibility of the 316 L substrate, however, the non-corrodibility of the joint is improved by transforming galvanic corrosion to uniform corrosion with the prolonged immersion time.