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The role of Cr atom in the early steam oxidation of Fe‐based alloys: An atomistic simulation
Author(s) -
Qi Jing,
Xu Hong,
Liang Zhiyuan,
Lu Ping,
Zhou Changsong
Publication year - 2021
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/maco.202011774
Subject(s) - oxide , dissociation (chemistry) , atom (system on chip) , metal , atom probe , ion , alloy , crystallography , chemistry , density functional theory , materials science , inorganic chemistry , metallurgy , computational chemistry , organic chemistry , computer science , embedded system
This study employed the density functional theory to capture the atomic‐level dissociation processes of steam and investigate the ions migration on Fe(001) and FeCr(001) surfaces, revealing the role of Cr atom in the early oxidation. Various coadsorption structures with different steam‐derived species have been systematically examined to find the most energetically favored surface site. The results showed that the steam dissociation on the alloy surface underwent two steps. First, H 2 O molecule on the top site was dissociated into OH group and H atom, which further combined with metal atoms on the bridge site and hollow site. Second, the OH group was decomposed into O and H atoms, which moved to two adjacent hollow sites and generated an oxide. On further oxidation, the Fe atom migrated outward and formed an outer Fe oxide, whereas the Cr oxide could only grow inward as O atom passed through oxide. It was found that the presence of Cr atom on the surface was thermodynamically beneficial, which could promote steam oxidation. The Cr atom could effectively block ion diffusion across the oxide scale and protect the underlying substrate from further oxidation. These results were in good agreement with experimental observation.