Investigation of grain-boundary structure-segregation relationship in an N18 nickel-based superalloy

Dany Lemarchand (1) , E. Cadel (1) , Sylvain Chambreland (1) , D. Blavette (1)

1 GPM - Groupe de physique des matériaux

Atom probe tomography and transmission electron microscopy were associated in order to characterize both structurally and chemically different general grain boundaries in a boron-doped N18 nickel-based superalloy. Boron, molybdenum and chromium segregation to the grain boundaries was demonstrated. The distribution of segregated atoms is shown to be non-uniform, both perpendicular to and in the plane of the grain boundaries. The Gibbsian interfacial excess was measured as a function of the misorientation angle and of the degree of twist-tilt character of the grain boundaries, leading to better knowledge of the structure-segregation rate relationship. For boron interfacial excess higher than a critical value, a thin chemically disordered film forms on each side of the grain boundaries. This film could explain the boron-induced mechanical reinforcement of the grain boundaries.

Domaines: Physique [physics]

Dany Lemarchand, E. Cadel, Sylvain Chambreland, D. Blavette. Investigation of grain-boundary structure-segregation relationship in an N18 nickel-based superalloy. Philosophical Magazine A: Physics of Condensed Matter, Structure, Defects and Mechanical Properties, 2002, 82 (9), pp.1651--1669. ⟨10.1080/01418610208235682⟩. ⟨hal-01928916⟩