First-Principles Study of the Electronic Properties of γ⁄γ′ Interface in Ni Based Superalloys

Abstract

Electronic properties of the H-, B-and C-doped = 0 interface in Ni based Superalloys are studied by means of the self-consistent fullpotential linearized augmented-plane-wave method under generalized gradient approximation. It is shown that all the three impurities, H, B and C prefer to occupy the Ni-rich octahedral interstitial sites at the = 0 interface. The calculated charge transfer suggests that the effect of H, B and C on the = 0 interface is localized. For the B and C cases, due to the hybridization between the p states of the impurity and the d states of the nearest-neighbor nickel atoms, the effect of both B and C is to strengthen the = 0 interface. In contrast, for the H case, the H-s/Ni-d hybridization results in a strong weakening of interplanar bonding and a slight enhancement of intraplanar Ni-Ni bonding on the interface planes, so that the effect of H is to decrease the cohesive strength of = 0 interface.

Predicting the morphologies of γʹ precipitates in cobalt-based superalloys

“…To calculate the γ/γ interfacial energy, we build a supercell containing 16 atomic layers with a total of 64 atoms [78]: eight layers of fcc cobalt and eight layers of Co 3 (Al,W) quasi-random structures [52]. This supercell structure is acceptable because we choose to work with the pure Co-Al-W system, avoiding the added complexity presented by impurity segregation.…”