Growth of α-alumina oxide film in high temperature oxidation of Fe-20Cr-5Al alloy thin strip

1998 ◽  
Vol 39 (8) ◽  
pp. 1151-1155 ◽  
Author(s):  
Kee Sun Lee ◽  
Kyu Hwan Oh ◽  
Won Wook Park ◽  
Hyung Yong Ra

The oxidation of metals at high temperatures has been investigated with some thoroughness by Pilling and Bedworth. They found that the metals could be divided into two great classes according to the nature of the oxide produced. If the volume of the oxide is greater than that of the metal from which it was produced an oxide film of compact structure and protective properties will be produced. If the volume of the oxide is less than that of its parent metal a porous oxide is produced which has no protective action whatever. The oxidation of the metals of the first class is controlled by the diffusion of oxygen through the protective film of oxide and the application of the diffusion laws to this process lead us to expect that the oxidation law will be W 2 = K t W 2 = amount of oxygen absorbed t = time K is a constant.


2020 ◽  
Vol 861 ◽  
pp. 83-88
Author(s):  
You Yang ◽  
Xiao Dong Wang

High temperature oxidation dynamic behaviors and mechanisms for 30Cr25Ni20Si heat-resistant steel were investigated at 800, 900 and 1000°C. The oxide layers were characterized by scanning electron microscopy (SEM-EDS), X-ray diffractometer (XRD). The results showed that the oxidation rate of test alloys is increased with increasing the oxidation time. The oxidation dynamic curves at 800 and 900°C follow from liner to parabolic oxidation law. The transition point is 10 h. At 1000°C, the steel exhibits a catastrophic oxidation, and the oxidation mass gain value at 50 h is 0.77 mg/cm2. This suggests that the steel at 900°C has formed a dense protective surface oxidation film, effectively preventing the diffusion of the oxygen atoms and other corrosive gas into the alloy. Therefore, at the first stage of oxidation, chemical adsorption and reaction determine the oxide film composition and formation process. At the oxide film growth stage, oxidation is controlled by migration of ions or electrons across the oxide film. When the spinel scale forms, it acts as a compact barrier for O element and improving the oxidation resistance.


2013 ◽  
Vol 747-748 ◽  
pp. 754-759 ◽  
Author(s):  
Fei Fan ◽  
Hao Sun ◽  
Di Zhao ◽  
Jiang Bo Sha

2 at.% and 4 at.% Mo were added to Co-9Al-9W-2Ta-0.02B alloy to replace W (hereafter referred to as the alloys of 2Mo and 4Mo, respectively; Mo-free alloy was referred to as the 0Mo alloy). The effects of Mo additions on the high temperature oxidation behavior of the alloys at 800 °C in air have been studied. The results indicated that, after oxidation in air at 800 °C for 100 h, the oxide film of the 0Mo alloy remained intact, but the cracking and spallation of the oxide film took place in the alloys of 2Mo and 4Mo. Oxidation kinetic curves revealed weight gain per unit area of the 0Mo alloy was 36.86 mg·cm-2, which was lower than that of the alloys of 2Mo (65.16 mg·cm-2) and 4Mo (48.54mg·cm-2). These suggested that the 0Mo alloy displayed superior oxidation resistance compared to the alloys of 2Mo and 4Mo caused by the formation of volatile MoO3 oxide, and sharp compressive stress formed in the outer layer during the oxidation. The oxide layer was composed of three layers of the Co3O4 + CoO outer layer, middle complex oxide layer containing Co, Al and W (Mo), inner Al2O3 layer and γ/Co3W zone adhere to the γ/γ' substrate.


2021 ◽  
Author(s):  
Ziming BAO ◽  
Renheng HAN ◽  
Yanqing ZHU ◽  
Hong LI ◽  
Ning LI ◽  
...  

The research focuses on the high temperature oxidation resistance of martensitic heat-resistant steel. A new type of martensitic heat-resistant steel was developed with the addition of Al and Cu, and the oxidation behavior of the new martensitic heat-resistant steel at 650 °C and 700 °C was analyzed. The high temperature oxidation kinetics curves of new martensitic heat-resistant steel at 650 °C and 700 °C were determined and plotted by cyclic oxidation experiment and discontinuous weighing method. XRD technique was applied to qualitatively analyze the surface oxide of the material after oxidation. The surface and cross-section morphology of the material were observed by field emission scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), and the oxidation mechanism at high temperature was analyzed. The results show that the oxide film can be divided into two layers after oxidation at 650 ºC for 200 h. The outer oxide film is mainly composed of Fe and Cu oxides, and the inner oxide film is mainly composed of Al2O3, SiO2 and Cr2O3. After oxidation at 700 ºC for 200 h, the outer layer is mainly composed of Fe, Cu, Mn oxides, and the inner layer is mainly composed of Cr, Al and Si oxides. The addition of a small amount of Cu promotes the diffusion of Al and Si elements, facilitates the formation of Al2O3 and SiO2, and improves the high-temperature oxidation resistance of martensitic heat-resistant steel.


2020 ◽  
Vol 38 (2) ◽  
pp. 165-181
Author(s):  
Andrey B. Rozhnov ◽  
Hannanh Alsheikh ◽  
Sergey A. Nikulin ◽  
Vladislav A. Belov ◽  
Elina V. Li ◽  
...  

AbstractHigh-temperature oxidation of E110 (Zr-1%Nb) zirconium alloy in steam at Т = 1100°C to various degrees has been carried out. Based on the studies of morphology and microstructure of the oxide film and metal, as well as on review of previously published results, the mechanism of alloy oxidation has been proposed, which includes oxide thickening close to the oxide/metal interface, growth of the thickened areas and their conversion into nodules, growth of the nodules and crowning of the metal surface (white spots), clustering of nodules under the formed oxide, formation of a double (white on the surface) oxide film and delamination of the oxide upper layer.


Coatings ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1090
Author(s):  
Zhi-Chao Li ◽  
Jie Xu ◽  
Dong-He Zhang ◽  
Zhen-Hai Xu ◽  
Shi-Rui Yang ◽  
...  

This paper presents the results of a study on the high-temperature oxidation characteristics after mechanical and laser removal of TA15 titanium alloy oxide film. The morphology, components, and roughness of the surface were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and laser confocal microscope (OM). The oxide film can be effectively removed with mechanical grinding and laser cleaning, and the oxide film after mechanical grinding is thicker and looser than that of after laser cleaning. The oxide film is principally composed of TiO2, Ti2O3 and TiO. Besides, there is a small amount of aluminum oxide on the surface. The surface after mechanical grinding was rougher than that of after laser cleaning. Thus, this work indicates that laser can not only clean the oxide film completely, but also strengthen the surface, which is a promising way to favor the widespread application of laser cleaning technology.


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