Effect of inhomogeneous composition on the passive film of AISI 431 coating fabricated by extreme-high-speed laser cladding

The effect of inhomogeneous composition of Cr and Fe on morphology and formation mechanism of passive film was investigated. A bi-layer structure passive film with a Cr2O3 inner layer and a Fe2O3 outer layer obtained on EHLA coating. The passive film is heterogeneous (thickness, compactness) between...

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Bibliographic Details
Published in:Surface & coatings technology 2022-06, Vol.440, p.128496, Article 128496
Main Authors: Ren, Yiqun, Chang, Shuai, Wu, Yuechen, Zhang, Zihao, Shen, Faming, Li, Liqun
Format: Article
Language:English
Subjects:
Bilayers
Chromium
Coating
Composition
Dendritic structure
Diffusion layers
Diffusion rate
Inhomogeneity
Iron
Laser beam cladding
Microstructure
Multilayers
Oxidation
Oxide coatings
Passive film
Stainless steel
Thermodynamics
Thickness
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Summary:The effect of inhomogeneous composition of Cr and Fe on morphology and formation mechanism of passive film was investigated. A bi-layer structure passive film with a Cr2O3 inner layer and a Fe2O3 outer layer obtained on EHLA coating. The passive film is heterogeneous (thickness, compactness) between inter-dendrite and dendrite core due to the element segregation and dislocation. Aspects of the passive film formation mechanism are discussed according to the thermodynamics. It indicates the prior oxidation of chromium resulting in the formation of inner Cr-rich layer, while higher diffusion rate of Fe3+ is the main reason for the formation of outer Fe-rich layer. This provides a new sight on the formation of multilayer oxide films. •A bi-layer structure passive film with a Cr2O3 inner layer and a Fe2O3 outer layer was obtained on the EHLA coating.•The thickness of the passive film is heterogeneous in the regions of inter-dendrite and dendrite core.•The outer layer of passive film on the dendrite core is thicker than that on the inter-dendrite.•The inner amorphous Cr-rich layer is well resistant to Chloride ions attack.
ISSN:0257-8972
1879-3347
DOI:10.1016/j.surfcoat.2022.128496