A multiscale modelling study of Ni-Cr crack tip initial stage oxidation at different stress intensities

Nishith Kumar Das, Ismail Tirtom, Tetsuo Shoji

研究成果: Article査読

18 被引用数 (Scopus)

抄録

In this study, different scale analyses have been performed to understand the very beginning stage of the Ni-Cr(1 1 1) binary alloy surface oxidation mechanism. The finite elements method (FEM) has been applied to find the stress intensity effect on a compact tension (CT) specimen crack tip, and a 2-μm rectangular region has been prepared for the quasi-continuum (QC) model. The displacement load calculated by FEM was applied at the upper and lower boundaries of the QC model. The obtained atomic positions of the deformed crystal structure were considered for quantum chemical molecular dynamics (QCMD) analysis by placing water molecules on the surface. Water molecules dissociate on the top site followed by the quick diffusion of hydrogen atoms on the surface through the hollow sites. Hydrogen is easily transported into the lattice due to its small atomic size. Increases in stress intensity factor (K) act to deform the structure, which augments oxygen penetration and reduces hydrogen diffusion time; as a consequence, changes in K result in an increase of metallic surface oxidation. Oxygen preferentially bonds with chromium to develop a protective passive film on the surface, and the quickly diffused hydrogen is trapped on the metal surface. Hydrogen bonds with the metal by receiving electrons and, therefore, works as an oxidant on the surface and weakens the metal atomic bond at the primary stage. Initially, the oxidized surface forms a strong bond with oxygen, resulting in the breakage of metal-metal bonds. Therefore, this hydrogen action enhances the very early stage surface oxidation.

本文言語English
ページ(範囲)336-342
ページ数7
ジャーナルMaterials Chemistry and Physics
122
2-3
DOI
出版ステータスPublished - 2010 8 1

ASJC Scopus subject areas

  • 材料科学(全般)
  • 凝縮系物理学

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