Micro-structural evolution of oxide scales formed on a Nb-Stabilizing heat-resistant steel at the initial stage in high-temperature water vapor

2020 ◽  
Vol 242 ◽  
pp. 122443 ◽  
Author(s):  
Zhiyuan Liang ◽  
Yungang Wang ◽  
Yong Gui ◽  
Qinxin Zhao
Keyword(s):  
Water Vapor ◽  
High Temperature ◽  
Structural Evolution ◽  
Resistant Steel ◽  
Oxide Scales ◽  
Heat Resistant Steel ◽  
Heat Resistant ◽  
High Temperature Water ◽  
Initial Stage ◽  
Temperature Water

In situ regeneration of commercial NH3-SCR catalysts with high-temperature water vapor

2018 ◽  
Vol 116 ◽  
pp. 57-61 ◽  
Author(s):  
Yao Shi ◽  
Pei Zhang ◽  
Tuotuo Fang ◽  
Erhao Gao ◽  
Fujuan Xi ◽  
...  
Keyword(s):  
Water Vapor ◽  
High Temperature ◽  
Nh3 Scr ◽  
High Temperature Water ◽  
In Situ Regeneration ◽  
Scr Catalysts ◽  
Temperature Water

Effect of Pre-Oxidation on the Steam Oxidation of Heat-Resistant Steel T92

2018 ◽  
Vol 37 (8) ◽  
pp. 733-739
Author(s):  
Xu Hong ◽  
Liang Zhiyuan ◽  
Ding Jianliang ◽  
Zhao Qinxin ◽  
Guan Shipian
Keyword(s):  
Mass Gain ◽  
Oxide Thickness ◽  
Steam Oxidation ◽  
Resistant Steel ◽  
Ion Diffusion ◽  
Heat Resistant Steel ◽  
Heat Resistant ◽  
Initial Stage ◽  
Long Time ◽  
Lower Oxidation

AbstractEffect of pre-oxidation on the steam oxidation of T92 heat-resistant steel at 650 °C was investigated. The results show that the mass gain and the oxide thickness of T92 sample with pre-oxidation treatment were lower than that of T92 sample after exposure in steam at 650 °C. The compact and discrete Cr-rich oxide which formed on the pre-oxidized specimen hindered ion diffusion, leading to the lower oxidation rate. The effect of pre-oxidation worked at the initial stage due to the protective Cr-rich layer formed in air gas. After a long time exposure in steam, the pre-oxidation influence decreased slowly and eventually disappeared. What’s more, the adhesion property of oxide scale was improved by pre-oxidation.

Study on the High Temperature Creep Behavior of 30Cr25Ni20 Heat-Resistant Steel

2019 ◽  
Vol 814 ◽  
pp. 157-162
Author(s):  
You Yang ◽  
Xiao Dong Wang ◽  
Wei Feng Tang
Keyword(s):  
High Temperature ◽  
Internal Structure ◽  
Creep Strain ◽  
High Temperature Creep ◽  
Resistant Steel ◽  
Heat Resistant Steel ◽  
Creep Fracture ◽  
Heat Resistant ◽  
Temperature Creep ◽  
Before And After

The high temperature creep test of heat-resisting steel 30Cr25Ni20 for automobile exhaust manifolds was carried out, and the creep strain-time curves at 650°C and 700°C in the different loads were obtained. The effects of different creep temperature and stress on creep life of materials were studied. The microstructure of the fracture after creep was observed by scanning electron microscopy. Microstructures before and after creep at different temperatures were compared by optical microscopy. The results show that the creep fracture life of heat-resistant steel decreases with the increase of stress at the same temperature. The creep fracture life decreases with the increase of temperature at the same stress, too. The fracture of heat-resistant steel shows good high temperature plasticity and a ductile fracture after creep. The fracture dimples become deeper with the increase of stress. At 650°Cand 700°C, the stress exponent is 8.6 and 6, respectively. When the sample was subjected to high temperature creep at 700°C, the precipitates increase obviously and the reticular structure became very large. At this point, the internal structure of the material is destroyed, and the matrix structure becomes unevenly distributed. The failure of the internal structure leads to the dramatic increase of the creep strain, and the failure of the internal structure will be more serious with the deformation of the sample.

High-Temperature Oxidation Behaviors of 30Cr25Ni20Si Heat-Resistant Steel in Air

2020 ◽  
Vol 861 ◽  
pp. 83-88
Author(s):  
You Yang ◽  
Xiao Dong Wang
Keyword(s):  
High Temperature ◽  
Oxide Film ◽  
High Temperature Oxidation ◽  
Film Growth ◽  
Surface Oxidation ◽  
Mass Gain ◽  
Resistant Steel ◽  
Temperature Oxidation ◽  
Heat Resistant Steel ◽  
Heat Resistant

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.

scholarly journals Properties of High Temperature Oxidation of Heat-resistant Steel with Aluminium and Copper

2019 ◽  
Vol 25 (4) ◽  
pp. 394-400
Author(s):  
Hong LI ◽  
Chengzhi ZHAO ◽  
Tao YAN ◽  
Chao DING ◽  
Hexin ZHANG ◽  
...  
Keyword(s):  
High Temperature ◽  
High Temperature Oxidation ◽  
Oxide Films ◽  
Main Element ◽  
Resistant Steel ◽  
Temperature Oxidation ◽  
Heat Resistant Steel ◽  
X Ray ◽  
Heat Resistant ◽  
Test Steel

The research is focused on a novel aluminum and copper-containing heat-resistant steel. The steel was designed by the material performance simulation software JmatPro, performed high-temperature oxidation tests at 650 °C and 700 °C atmospheric conditions, and analyzed the high-temperature oxidation processes and its mechanisms.The phase transtions and surface morphology of the oxide films were studied using X-ray diffraction (XRD), electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS). The results showed that the equilibrium phase of the test steel is composed of γ phase and δ phase at 1050 °C and tranforms to tempered martensite and δ-Fe mixed structure after heat treatment. The preferential oxidation of Fe and Cr and the internal oxidation of Al occurred during the high temperature oxidation of the test steel. The oxide films were formed with various shape and weak bonding properties after high-temperature oxidation at 650℃. To the contrary, the oxide films more regular and evenly distributed, and has a certain protective effect after high-temperature oxidation at 700 ℃. The oxide films were divided into two layers, Fe2O3 is main element in the outer layer, the inner layer is mainly consisting the oxide of Cr. However, the addition of Cu element can promote the diffusion of Al and Si elements, which is beneficial to the formation of Al2O3 and SiO2 protective oxide films and excellent in high temperature oxidation resistance.

Sign in / Sign up

Export Citation Format

Share Document