电站锅炉模拟烟气环境下的非晶涂层耐腐蚀性能研究
发布时间：2019-06-21 18:53
【摘要】：我国电站锅炉在实际运行过程中,受煤种变化等因素的影响,实际的排烟温度常常比设计值高,这会大幅度地降低锅炉的热效率,为提高电站的运行效率应有效地回收烟气余热。煤炭中含有一定量的硫元素,在锅炉的尾部烟道中,烟气中的水蒸气和硫酸蒸汽进入温度较低的受热面时,与金属壁面接触,可能发生冷凝而对金属壁面造成低温腐蚀,从而影响设备的安全运行,缩短其使用寿命,因此,要突破金属材料腐蚀的限制以充分利用烟气余热。非晶合金是一种高强度、高硬度和耐腐蚀的新型材料,在原有的金属材料上镀上非晶合金,可作为低温烟气腐蚀问题的解决方法。本文开展非晶合金在低温烟气环境下的腐蚀研究。通过调研选取合适的工艺参数,采用激光熔覆技术制备单层和双层铁基非晶涂层,随后进行了金相分析、SEM观察、X射线衍射分析、能谱分析和维氏硬度表征,结果表明:制备的非晶涂层结构致密均匀,表面裂纹较少,冶金结合良好,出现了明显的分层现象,非晶颗粒中夹杂着少量的纳米晶颗粒,非晶/纳米晶的复合结构使基体的硬度提升了2~3倍;然后,进行摩尔浓度为0.5mol/l的硫酸和质量浓度为3.5%的氯化钠电化学实验,得出试样的Tafel极化曲线显示:非晶涂层的自腐蚀电位明显高于基体,自腐蚀电位分别提高了0.1V~0.2V,表明涂层能很好地适应电站强酸等腐蚀环境;最后,模拟烟气腐蚀实验结果表明:单层非晶涂层的耐腐蚀速率约为基体的2倍,双层非晶涂层的耐腐蚀速率约为基体的3倍,主要原因是涂层自身的复合结构性能优异,同时,钼、铬等微量元素在表面形成钝化膜,可阻止烟气腐蚀的继续深入。综合分析,在基体上用激光熔覆技术镀上非晶涂层,可以有效地改善基体的耐腐蚀性能。研究成果将为低温烟气腐蚀环境下的金属材料优化提供指导,有助于推动烟气余热利用由理论分析走向工程实践。
[Abstract]:In the actual operation process of power station boilers in our country, affected by the change of coal type and other factors, the actual smoke exhaust temperature is often higher than the design value, which will greatly reduce the thermal efficiency of the boiler. In order to improve the operation efficiency of the power station, the waste heat of flue gas should be effectively recovered. Coal contains a certain amount of sulfur. In the tail flue of the boiler, when the steam and sulfuric acid steam in the flue gas enter the heating surface with low temperature, the condensation may occur and cause low temperature corrosion to the metal wall, thus affecting the safe operation of the equipment and shortening its service life. Therefore, it is necessary to break through the limitation of metal material corrosion to make full use of the waste heat of the flue gas. Amorphous alloy is a new type of material with high strength, high hardness and corrosion resistance. Coating amorphous alloy on the original metal material can be used as a solution to the corrosion problem of low temperature flue gas. In this paper, the corrosion of amorphous alloys in low temperature flue gas environment is studied. Through investigation and selection of suitable process parameters, single-layer and double-layer iron-based amorphous coatings were prepared by laser cladding technology. Metallographic analysis, SEM observation, X-ray diffraction analysis, energy spectrum analysis and Vickers hardness characterization were carried out. the results show that the amorphous coatings have dense and uniform structure, few surface cracks, good metallurgical bonding and obvious delamination, and a small amount of nanocrystal particles are mixed in the amorphous particles. The hardness of the matrix is increased by 2 times as much as that of the matrix by the composite structure of amorphous / nanocrystal. Then, the electrochemical experiments of sulfuric acid with molar concentration of 0.5mol/l and sodium chloride with mass concentration of 3.5% were carried out. The Tafel polarization curves of the samples showed that the self-corrosion potential of the amorphous coating was significantly higher than that of the substrate, and the self-corrosion potential of the amorphous coating was increased by 0.1 V 鈮，
本文编号：2504279
[Abstract]:In the actual operation process of power station boilers in our country, affected by the change of coal type and other factors, the actual smoke exhaust temperature is often higher than the design value, which will greatly reduce the thermal efficiency of the boiler. In order to improve the operation efficiency of the power station, the waste heat of flue gas should be effectively recovered. Coal contains a certain amount of sulfur. In the tail flue of the boiler, when the steam and sulfuric acid steam in the flue gas enter the heating surface with low temperature, the condensation may occur and cause low temperature corrosion to the metal wall, thus affecting the safe operation of the equipment and shortening its service life. Therefore, it is necessary to break through the limitation of metal material corrosion to make full use of the waste heat of the flue gas. Amorphous alloy is a new type of material with high strength, high hardness and corrosion resistance. Coating amorphous alloy on the original metal material can be used as a solution to the corrosion problem of low temperature flue gas. In this paper, the corrosion of amorphous alloys in low temperature flue gas environment is studied. Through investigation and selection of suitable process parameters, single-layer and double-layer iron-based amorphous coatings were prepared by laser cladding technology. Metallographic analysis, SEM observation, X-ray diffraction analysis, energy spectrum analysis and Vickers hardness characterization were carried out. the results show that the amorphous coatings have dense and uniform structure, few surface cracks, good metallurgical bonding and obvious delamination, and a small amount of nanocrystal particles are mixed in the amorphous particles. The hardness of the matrix is increased by 2 times as much as that of the matrix by the composite structure of amorphous / nanocrystal. Then, the electrochemical experiments of sulfuric acid with molar concentration of 0.5mol/l and sodium chloride with mass concentration of 3.5% were carried out. The Tafel polarization curves of the samples showed that the self-corrosion potential of the amorphous coating was significantly higher than that of the substrate, and the self-corrosion potential of the amorphous coating was increased by 0.1 V 鈮，
本文编号：2504279
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