M5B3 Boride at the Grain Boundary of a Nickel-based Superalloy

The grain boundary microstructures of a heat-treated Ni-based cast superalloy IN792 were investigated. The results show that M5B3 boride precipitates at the grain boundary. A special orientation relationship between M5B3 phase and the matrix at one side of the grain boundary is found. At the same time, two M5B3 borides with different orientations could co-exist in a single M5B3 particle as an intergrowth besides existing alone, thus forming orientation relationship between the two M5B3 phases and matrix. This phenomenon could be attributed to the special orientation relationship between M5B3 phase and the matrix.