A Stochastic Model of Oxidation Mechanism on High Temperature Corrosion of Stainless Steel

2006 ◽  
Author(s):  
Huajun Chen ◽  
Yitung Chen ◽  
Hsuan-Tsung Hsieh
Keyword(s):  
High Temperature ◽  
Oxide Layer ◽  
Present Model ◽  
Oxidation Mechanism ◽  
High Temperature Corrosion ◽  
Iron Species ◽  
Corrosive Liquid ◽  
Model Mapping ◽  
Wagner Theory

To interpret the role of diffusion and reaction process, a cellular automaton model, which combines the surface growth and internal oxidation, was developed to explain the oxidation mechanism of stainless steels in high temperature corrosive liquid metal environment. In this model, three main processes, which include the corrosion of the substrate, the diffusion of iron species across the oxide layer and precipitation of iron on the oxide layer, are simulated. The diffusion process is simulated by random walk model. Mapping between present model and Wagner theory has been created. The gross features concerning the evolution of the involved process were founded.

Analysis on Failure of Oxide Layer of T91 High Temperature Superheater Tube

2014 ◽  
Vol 1070-1072 ◽  
pp. 505-511
Author(s):  
Shan Shan Zhang ◽  
Guang Chen ◽  
Chang Ming Li ◽  
Da Hu
Keyword(s):  
High Temperature ◽  
Dissolved Oxygen ◽  
Oxide Layer ◽  
Outer Layer ◽  
Oxidation Mechanism ◽  
Middle Layer ◽  
Compact Structure ◽  
Protective Properties ◽  
Superheater Tube ◽  
Temperature Operating

The reason why the failure protective properties of the oxide layer of T91 high temperature superheater tube were analyzed in this study. The microstructure of the oxide layer of T91 high temperature superheater tube was observed by scanning electron microscope (SEM) and the morphological features of it was also analyzed. The concentrations of alloy elements in the section of internal tube were quantitatively analyzed using Energy Dispersive System (EDS). The results showed that the oxide layer of T91 tube can be divided into three layers: inner layer, middle layer and outer layer. The inner layer was formed by chromium rich oxide with compact structure. The middle layer was made up by porous oxide with loose structure. The outer layer was identified as Fe2O3. When the content of dissolved oxygen in steam was excessive, the apparent peeling marks will be appeared in the oxide layer of T91 high temperature superheater tube and the distribution of alloy elements in the oxide layer will present obvious proliferation, migration and enrichment phenomenon. Two different mechanisms (steam oxidation mechanism and oxygen oxidation mechanism) will exercise different influences on the structure and protective properties of the oxide layer: when steam contained dissolved oxygen, the oxide layer will be peroxidated by steam and the structure of oxide layer will be broken; When the tube was over-temperature operating, the oxide layer will be oxidated by oxygen.

scholarly journals High-Temperature Oxidation Performance of 4Cr4Mo2NiMnSiV Hot Die Steel

2021 ◽  
Author(s):  
Renheng HAN ◽  
Ning LI ◽  
Ziming BAO ◽  
Xinjian HU ◽  
Hexin ZHANG ◽  
...  
Keyword(s):  
High Temperature ◽  
Oxide Layer ◽  
High Temperature Oxidation ◽  
Metallic Matrix ◽  
Oxidation Mechanism ◽  
Surface Oxidation ◽  
Ambient Atmosphere ◽  
Temperature Oxidation ◽  
Die Steel ◽  
Hot Working Die Steel

A new type of hot working die steel was designed by using JMatPro, and high-temperature oxidation tests were carried out in the ambient atmosphere at 600 ℃ and 700 ℃. The heat treatment process and oxidation mechanism of the designed 4Cr4Mo2NiMnSiV steel were studied in detail. XRD, SEM and EDS were used to analyze the crystallographic phases, surface and cross-section morphologies of the oxide films. The results show that the main phases in the 4Cr4Mo2NiMnSiV steel were γ and α + δ. During the high-temperature oxidation, oxidation of the Fe outer layer and Cr inner layer occurred. After oxidation at 600℃, the surface oxidation layer comprised a monolayer with an uneven morphology. The surface oxide film had two layers after oxidation at 700℃. The outer oxide layer mainly contained Fe2O3 and Fe3O4, while the inner oxide layer mainly contained Cr2O3. The microstructure was relatively regular and had a significant effect on the protection of the metallic matrix. When oxidized, the 4Cr4Mo2NiMnSiV alloy steel easily formed protective layers, such as Cr2O3 and SiO2, so that the test steel had excellent oxidation resistance at high temperatures.

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