超临界发电锅炉在650 ℃水蒸气中常发生腐蚀,针对此问题进行了锅炉钢表面化学预氧化防护研究。先将锅炉钢TP347H放入管式炉中,管式炉通流量为20 mm/s的氧气,温度300 ℃下氧化2 h,利用重量法研究了氧化层对锅炉钢的防护效果,利用扫描电子显微镜观察了材料的表面形貌,结合产物成分分析得到以下结论:TP347H锅炉钢在300 ℃ 氧化2 h,可生成约0.2 μm的氧化膜;这种氧化膜使材料在650 ℃水蒸气中腐蚀速度比未预氧化的材料降低了87.5%;表面没有氧化的TP347H锅炉钢在高温水蒸气中腐蚀后,产物为2层,表层主要为Fe的氧化物,底层为Fe、Cr、Ni的氧化物,2层间结合强度较差,外层产物容易脱落,而表面氧化后的试样腐蚀产物为单层,腐蚀产物中为Fe、Cr、Ni的氧化物,涂层与基体结合强度好,腐蚀产物不易脱落。
Supercritical power generation boilers often corrode in 650 °C water vapor. A study on chemical pre-oxidation protection of boiler steel surfaces was conducted to address this problem. Firstly, the TP347H boiler steel was placed in a tubular furnace with a flow rate of 20 mm/s of oxygen and oxidized for 2 h at 300 ℃. The protective effect of the oxide layer on the boiler steel was studied using the gravimetric method. Scanning electron microscope (SEM) was used to observe the surface morphology of the material. Combined with the product composition analysis, the following conclusions were obtained: after 2 h of oxidation at 300 ℃, the thickness of the oxidation layer of TP347H boiler steel could reach 0.2 μm. This oxide layer reduced the corrosion rate of the material in 650 ℃ water vapor by 87.5% compared to the material without pre-oxidation. The corrosion products of the TP347H boiler steel without oxidation after corroded in high temperature water vapor could be divided into two layers: the surface layer was mainly the oxide of Fe, and the bottom layer was the oxide of Fe, Cr, and Ni. The bonding strength between the two layers was poor, and the outer layer products were easy to fall off. After the surface oxidation treatment, the corrosion products of the sample were only a monolayer. The corrosion products were mainly oxides of Fe, Cr and Ni. The bonding strength between the coating and the substrate was good, and the corrosion products were not easy to fall off.
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