Characterization of borides in Co-Re-Cr-based high-temperature alloys

Co-Re-Cr-based alloys with additions of 200 ppm or 1000 ppm boron were investigated by high-resolution methods such as scanning electron microscopy, transmission electron microscopy and three-dimensional atom probe. The chemical composition of borides with a lamellar structure resembling a eutectic as determined by three-dimensional atom probe is Cr0.68Re0.46Co0.24B, the composition of isolated boride particles at the grain boundaries is Cr0.76Re0.40Co0.35B. A systematic study was carried out to determine the crystal structure of the various types of borides. Despite their varying chemical composition, the borides in the two alloys, even when appearing in different morphologies, exhibit the same orthorhombic C-centred unit cell with lattice parameters a = 0.436 nm, b = 0.755 nm and c = 1.498 nm.