First-principles study of the effect of the corrosive environmental components on the grain boundary strength in...

The destruction of nickel (Ni)-based alloys occurs mainly along the grain boundaries (GBs) that have been exposed to a corrosive environment. Understanding the mechanism of such exposure at the atomic level is investigated in this study. Based on density functional theory calculations, the GB energy and the GB strength of the Σ3(111) coherent twin, Σ3(11̄2̄) incoherent twin, and high-angle Σ5(02̄1) GBs in Ni are estimated. The change in the GB strength in Ni is considered upon the change in the concentration of corrosive elements, such as O, Cl, and S. The highest GB strength is found for the GB in the O-rich environment, while the lowest GB strength is found for the GB in the Cl-rich environment. In the case of interstitial O and Cl impurities, the energy that affects the GB's strength or brittleness comes both from the mechanical factor, which is related to the atomic displacements around the impurity, and from the chemical factor, which is related to the bond formation/breaking around the impurity. The results of this study not only deepen the fundamental understanding of the impurity effect on the GB strength in Ni and Ni-based alloys, but also provide valuable information for production and technological application of these alloys.