Partitioning of Solutes at Crystal Defects in Borides After Creep and Annealing in a Polycrystalline Superalloy

Lilensten, L. and Kostka, A. and Lartigue-Korinek, S. and Gault, B. and Tin, S. and Antonov, S. and Kontis, P.

Volume: Pages:
DOI: 10.1007/s11837-021-04736-5
Published: 2021

We have investigated the partitioning of solutes at crystal defects in intergranular Cr-rich M2B borides after creep at 850°C/185MPa and annealing at 850°C for approximately 3000 h in a polycrystalline nickel-based superalloy. Borides were found to coarsen in both cases, with the borides after creep being the thickest (800–1100 nm), compared to borides annealed in the absence of an external applied load (400–600 nm). Transmission electron microscopy revealed that the coarsened borides have either a tetragonal I4/mcm structure, or an orthorhombic Fddd, with those two structures coexisting in a single particle. The presence of a very high density of planar faults was systematically observed within the coarsened borides. The faults were correlated with chemical fluctuations of B and Cr, revealed by atom probe tomography. In addition, partitioning of Ni and Co was observed at dislocations within the borides after creep, providing insights into the deformation of borides. © 2021, The Minerals, Metals & Materials Society.

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