Insights into the effect of γ′- or γ′′-precipitated phase types on resistance against harmful atoms of heterogeneous interface in nickel-based superalloys

Abstract

To improve the service performances of nickel-based superalloys by controlling the type and proportion of precipitate phases, the resistances against harmful atoms (weakening effect caused by harmful atoms and capacity for hindering intrusion of harmful atoms) of the representative γ-matrix/γ′- or γ′′-precipitated phase heterogeneous interfaces (γ-Ni/γ′-Ni3Al, γ-Ni/γ′-Ni3Ti, and γ-Ni/γ′′-Ni3Nb interfaces) was investigated. The results show that, the harmful atoms (H, O, and S atoms) can be stable adsorbed on heterogeneous interfaces and weaken the interfacial bonding strength, resulting in the fracture position change from γ′- or γ′′ slab to interface during tensile deformation. Because of the minimum changes on interfacial bonding characteristics after the intrusion of harmful atoms, γ-Ni/γ′′-Ni3Nb heterogeneous interface (HIγ″−Ni3Nb) demonstrates the strongest resistance against weakening effect, presented as the smallest deterioration of interfacial ideal work of adhesion and tensile strength. Meanwhile, the energy barrier of harmful atoms diffusing along HIγ″−Ni3Nb is much larger than those along HIγ″−Ni3Al and HIγ″−Ni3Ti, leading to a smallest diffusion coefficient for harmful atoms diffusing along HIγ″−Ni3Nb. The result indicates HIγ″−Ni3Nb also shows the strongest capacity for hindering the intrusion of harmful atoms. This phenomenon is attributed to the strongest interaction between harmful atoms on saddle point and the neighboring atoms on HIγ″−Ni3Nb during the diffusion process. To summary, the Ni-based superalloys with γ′′-Ni3Nb as the main precipitated phase demonstrate the most promising properties in resistance against harmful atoms. This work not only contributes to the further improvement of Ni-based superalloys, but also provides the creative ideas for the research of other superalloys.