INFLUENCE OF ISOTHERMAL SOLIDIFICATION ON MICROSTRUCTURAL DEVELOPMENT IN NI-SI-B FILLER METALS

An examination is reported of the microstructure of joints between nickel substrates fabricated using Ni-Si-B filler metal (AWS classification BNi-3). This investigation was undertaken because the presence of residual boride and silicide phases after joining can affect the subsequent mechanical properties of the joint. The microstructures developed in the joints are compared with those formed in similarly heat treated filler metal. Various models of the transient liquid phase process are also considered and predicted times to complete isothermal solidification are compared with experimental values. An initial examination of the influence on filler metal microstructure of a ternary addition (chromium) to the substrate is included.