Interfacial microstructure and mechanical characterization of silicon nitride/nickel-base superalloy joints by partial transient liquid phase bonding

Si3N4 ceramic has been joined successfully to nickel-based superalloy by partial transient liquid phase (PTLP) bonding using Ni/Cu/Ti multi-interlayers. The interfacial microstructure and strength of the joints were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and a three-point bending test. According to the TEM analysis, it was found that a TiN reaction layer was formed at the Si3N4/filler alloy interface. The TiN reaction layer was composed of two zones: one next to the Si3N4 ceramic with a thickness of about 0.4 μm and the other zone with grains of about 0.8 μm. The microstructure of the joint between the Si3N4 and the Cu interlayer can be described as: TiN layer with fine grains/TiN layer with coarse grains/Ti2Ni layer. Ni3Ti and CuTi2 phases were produced at the interface between the Cu interlayer and the DZ483 superalloy. The room-temperature average strength of the joint was 147 MPa, and 96 MPa was achieved when the joints were tested at 1073 K.