Corrosion Behavior Study of Fe-22Cr-25Ni Austenitic Heat-Resistant Steel under Supercritical CO2 Condition
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摘要: 研究了Fe-22Cr-25Ni奥氏体耐热钢在600℃/700℃、15 MPa超临界CO2环境中的高温腐蚀行为。采用拉曼光谱仪、辉光放电光谱仪、扫描电镜和能谱分析仪对腐蚀产物的成分、含量和元素分布进行表征。实验结果表明:Fe-22Cr-25Ni奥氏体耐热钢在600℃/700℃下的腐蚀动力学符合类抛物线规律,腐蚀增重的变化量随温度的升高而增大;通过观察表征结果和热力学计算得出腐蚀产物成分主要为Cr2O3,从气体侧到基体侧依次为最外侧的是Mn的氧化物、内部的Cr2O3和Mn-Cr氧化物、氧化层/基体界面处的SiO2层,以及基体内的碳化物和内氧化物;C主要沉积于腐蚀产物表面,贫Cr区的宽度和深度随时间的增大而增大。同时根据O元素和C元素的质量比及热力学计算结果,提出C极有可能以离子状态发生内扩散。
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关键词:
- 超临界CO2 /
- 腐蚀行为 /
- 奥氏体耐热钢 /
- Fe-22Cr-25Ni
Abstract: The high temperature corrosion behavior of austenitic heat-resistant steel Fe-22Cr-25Ni under 600℃/700℃ and 15 MPa supercritical CO2 condition was investigated. The composition, content and element distribution of corrosion products were characterized by Raman spectroscopy, Glow Discharge Spectroscopy, SEM and EDS. The results show that the corrosion kinetics of Fe-22Cr-25Ni at 600℃/700℃ follow the parabola-like law, and the change of corrosion mass gain increases with increasing temperature. By observing the characterization results and thermodynamic calculations, it is concluded that the corrosion product composition is mainly Cr2O3, specifically, from the gas side to the substrate side are the outermost Mn oxide, the internal Cr2O3 and Mn-Cr oxide, the SiO2 layer at the oxide layer / substrate interface, and the carbide and internal oxide in the substrate; C is mainly deposited on the surface of corrosion products, the width and depth of the Cr-depleted zone increase with increasing time. At the same time, according to the mass ratio of O and C and the results of thermodynamic calculation, it is suggested that C is very likely to be diffused in ionic state.-
Key words:
- Supercritical CO2 /
- Corrosion behavior /
- Austenitic heat-resistant steel /
- Fe-22Cr-25Ni
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表 1 Fe-22Cr-25Ni奥氏体耐热钢的化学成分 %
Table 1. Chemical Compositions of Fe-22Cr-25Ni Heat-resistant Steel %
元素 Fe Cr Ni C Si Mn 质量分数 Bal 21.65 25.07 0.07 0.17 0.49 元素 W Cu Co Nb S P 质量分数 3.85 3.0 1.5 0.5 0.001 0.014 Bal—列出的成分之外的剩余量 表 2 700℃超临界CO2环境下1000 h后断面点扫描结果 %
Table 2. Spot Scanning Results of Cross-section at 700 ℃ in Supercritical CO2 Environment after 1000 h of Reaction(%)
位置 O Si Cr Mn Fe Ni 1 31.23 0.09 42.98 1.63 0.19 0.00 2 22.55 16.67 4.01 1.33 17.76 12.65 3 0.17 0.09 4.96 0.17 42.58 27.75 表 3 不同温度下金属氧化反应所需氧分压
Table 3. Oxygen Partial Pressure Required for Metal Oxidation Reaction at Different Temperatures
化学方程式 $P_{\rm{O_2}} $(600 ℃)/MPa $P_{\rm{O_2}} $ (700 ℃)/MPa Mn+O2=MnO2 1.97×10−22 3.05×10−19 4/3Cr+O2=2/3Cr2O3 9.36×10−37 3.77×10−32 Si+O2=SiO2 9.48×10−45 3.51×10−40 -
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