耐蚀耐磨铁基非晶合金涂层制备及腐蚀与冲蚀性能研究

IMR OpenIR

	耐蚀耐磨铁基非晶合金涂层制备及腐蚀与冲蚀性能研究
	王勇
学位类型	博士
导师	郑玉贵 ; 王建强
	2012
学位授予单位	中国科学院金属研究所
学位授予地点	北京
学位专业	腐蚀科学与防护
关键词	铁基非晶合金涂层腐蚀冲蚀液/固双相流超音速火焰喷涂 Fe-based Amorphous Metallic Coatings Corrosion Behavior Erosion-corrosion Resistance Liquid/particle Two-phase Flow High-velocity Oxy-fuel
摘要	"本文系统地研究了FeCrMoMnWBCSi非晶合金的腐蚀行为以及合金成分对其耐蚀性和硬度的影响机制，分析并表征了HVOF喷涂FeCrMoMnWBCSi非晶合金涂层的微观形貌、成分及非晶结构特征，揭示了涂层的腐蚀及冲蚀机理，阐述了封孔处理和HVOF喷涂参数对其耐蚀性及硬度的影响规律。旨在理解铁基非晶涂层腐蚀及冲蚀机理的基础上，指导耐蚀耐磨铁基非晶合金涂层设计，为该涂层在腐蚀/磨损领域的推广应用提供科学依据。主要研究结果总结如下：铁基非晶合金在0.5 M NaCl中耐蚀性优于同浓度HCl溶液，而在0.25 M Na2SO4中耐蚀性则低于同浓度H2SO4溶液。在含氯介质中钝化膜的稳定性主要取决于膜层的结构特性(致密度、缺陷等)，在HCl溶液中低的耐蚀性除了H+阳极催化外，所形成的膜层疏松且缺陷多，促进了Cl-浸透作用。在硫酸盐溶液中，由于SO42-吸附作用，膜层成分对于腐蚀过程起着重要作用，H+催化溶解后表面富集低价态Cr3+和Mo4+氧化物使得合金在H2SO4溶液中耐蚀性更优。 Mo、Mn和W元素对铁基非晶合金腐蚀行为和硬度有重要影响。耐蚀性与Mo、W含量存在一临界值(9.4 at.%和3.2 at.%)，随Mn含量增加呈增加趋势，主要与膜层中Mo4+，Mn4+和W6+氧化物含量相关。硬度则随Mo、W含量增加而增加，由于高硬M23C6和M6C类碳化物的形成，但过高的Mo含量(高于9.4 at.%)对硬度提高不大。优化合金配比可实现集耐蚀耐磨于一体的合金成分设计。 HVOF制备的铁基非晶合金涂层除具非晶结构特征外，含Fe2C、Cr7C3、Cr2B、M23C6和少量氧化物组成的纳米晶体相。在海水介质中，涂层表现出较宽且稳定的钝化区间，具有优异的抗点蚀能力。非晶结构及钝化膜中存在的Cr、Mo、W等增加了其点蚀抗力，而孔隙的存在则降低了其均匀腐蚀抗力。冲蚀过程中涂层机械损伤优先发生于孔隙等缺陷部位，高的硬度和非晶结构使其呈现出优异的抗冲蚀性。降低孔隙率是提高其抗腐蚀和冲蚀的关键。封孔处理可以提高涂层的均匀腐蚀抗力，AlPO4封孔涂层具有优异的均匀腐蚀抗力和良好的点蚀抗力，可实现不低于50 μm的封孔深度，极大提高涂层的硬度。钝化膜的稳定性影响了涂层的长期腐蚀行为，AlPO4封孔涂层在长期浸泡腐蚀后具有较低的缺陷浓度，膜层保护性最强，可以应用于耐蚀/耐磨领域。氧/燃气比和送粉速率极大地影响HVOF喷涂涂层的结构和性能。高的氧/燃气比和低的送粉速率所制备的涂层表面未熔颗粒均匀、孔隙率低，硬度较高。当孔隙率低于1.21%，非晶含量占主导，钝化电流随非晶含量降低而增加；反之孔隙率是影响涂层耐蚀性的主要因素。HVOF喷涂技术可以制备耐蚀耐磨于一体的涂层。"
其他摘要	"In this thesis, FeCrMoMnWBCSi metallic glasses were selected to clarify the corrosion behavior and mechanism, and to elucidate the role of alloying elements in influencing the corrosion resistance and hardness. The fabrication and microstructural characteristics of HVOF-sprayed AMCs were revealed. The corrosion and E-C behavior of AMCs were investigated by using electrochemical methods and rotating disk. The porosities of the AMCs were sealed with four sealants, and associated with the influence of spraying parameters were also examined. The present study would advance the understanding of corrosion and E-C mechanism, and guide the design of high corrosion and wear resistant AMCs as well as provide a scientific basis for promotion of the potential applications of Fe-based AMCs in corrosive and abrasive environments. The main results are summarized as follows: Fe-based metallic glasses (MGs) exhibited much lower passive current densities in H2SO4 and NaCl solutions, whereas much higher values in Na2SO4 and HCl solutions. In chloride solutions, corrosion resistance was dominantly influenced by the passive film structure (compactness, defect density) due to the chloride ions penetration mechanism. Fe-based MGs exhibited a much lower stability in HCl solution for the H+ ions catalyzing the anodic reaction. High donor density and low compactness of the film led to the lower corrosion resistance of Fe-based MGs in HCl solution than that in NaCl solution. In sulphate solutions, corrosion process of anions (HSO4-/SO42-) followed the adsorption mechanism. The composition of passive film played a key role in corrosion resistance. In H2SO4 solution, the enrichment of Cr3+ and Mo4+ oxides on the surface favored the formation of a more stable and protective layer which can be assumed to be responsible for the observed high stability of passive film. The alloying elements of Mo, Mn and W showed great influence on corrosion behavior and hardness of Fe-based MGs. The passive current densities decreased with Mo and W content to a critical value (9.4 at.% and 3.2 at.%), and increased with Mn content. The protective Mo4+, Mn4+ and W6+ oxides film on the surface attributed to the enhanced stability and protection ability of passive film. The hardness of alloy was not sensitive to the Mn content, but increased with the Mo and W additions for the formation of M23C6 and M6C type carbides. The higher Mo contents (more than 9.4 at.%) showed little influence on the hardness improvement. Corrosion and wear resistance can be balanced based on the influence of alloying elements. The composite structure of HVOF thermal spraying FeCrMoMWBCSi AMCs was formed with some nanocrystallite phases (Fe2C, Cr7C3 , M23C6, Cr2B and some oxides) embedded in the amorphous matrix. The AMCs exhibited a wide passive region and the presence of Cr, Mo and W oxides in the film by XPS endowed the AMCs with high pitting resistance. The relatively low uniform corrosion resistance of AMCs was due to the occurrence of the incompact structure and pores. The E-C process was controlled by the mechanical damage resulting from erosion. AMCs were preferentially attacked from some coating defects. The high hardness and amorphous structure may be the main reason for the higher E-C resistance of AMCs. The optimization of HVOF spraying parameters and/or pores sealing treatment after spraying would be investigated to further improve the uniform corrosion and E-C resistance. The uniform corrosion resistance of the coatings can be enhanced greatly by Na3SiO4, cerium salt and AlPO4 sealeing treatment. The AlPO4 sealant can penetrate the coatings by no less than 50 μm and enhance their hardness, which exhibited a more uniform corrosion resistance, fairly good pitting corrosion resistance, and can be applied in long-term corrosive and/or abrasive environments. The AlPO4- sealed coating performed better as a protective passive film during the long-term immersion test for a lower defect concentration and a more protective passive film, which may be applied in corrosive and/or abrasive environments. The microstructures and properties of the coatings were sensitive to the spray parameters of oxygen/fuel (O/F) ratio and powder feed rate considerably. The coatings obtained at high O/F ratio and low powder feed rate showed high hardness for the uniformly melted particles and low porosity. There was a critical passive current density for balancing the porosity and the amorphous phase fraction. Corrosion resistance was dominant by the amorphous phase fraction when the porosity was less than 1.21%, while by porosity when it was higher than that. Therefore, the corrosion resistance and hardness can be enhanced significantly by tailoring the spraying parameter during the HVOF spraying process."
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64500
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	王勇. 耐蚀耐磨铁基非晶合金涂层制备及腐蚀与冲蚀性能研究[D]. 北京. 中国科学院金属研究所,2012.