摘要
等离子体电解氧化(Plasma electrolytic oxidation，PEO)又称为微弧氧化(Micro-arc Oxidation，MAO)是一种在阀金属如铝、镁、钛、锆等金属及其合金表面形成陶瓷保护膜的先进表面处理技术，而非阀金属如铁、铜、镍等金属及其合金表面进行PEO 则难以实现。然而现今已有人在钢铁中尝试直接进行PEO处理，并得到一些有益的结果。分别在铝酸盐与硅酸盐体系中制备得到具有一定保护性的PEO膜层，但PEO 过程中的成膜机理与等离子体放电击穿行为未能深入研究。本文主要以Q345碳钢在铝酸钠电解液体系和硅酸钠电解液体系中的PEO过程进行研究，深入了解非阀金属在PEO过程中的膜层形成过程及伴随的等离子体火花放电行为。
Q345碳钢在铝酸盐体系中进行PEO处理时，通过改变不同的电解液成分，能够在8 g /l NaAlO2 + 2 g /l NaH2PO4中成功制得PEO膜层，在8 g /l NaAlO2中，电流密度的增加有助于Q345碳钢表面成膜，而在2 g /l NaH2PO4中，试样表面仅仅发生电化学溶解。Q345碳钢表面生成的一层磷酸铝混合物膜层，膜层成分可能为磷酸铝(AlPO4)、磷铝石(AlPO4·2H2O)和氧化铝-磷酸铝(Al2O3·AlPO4)。该膜层是Q345碳钢表面产生等离子体放电和PEO膜层形成的关键。在8 g /l NaAlO2 + 2 g /l NaH2PO4中通过改变试样表面粗糙度、电解液状态和电源占空比等条件，试样表面粗糙度（抛光与未抛光）、电解液状态（静置与搅拌）一定程度上影响了等离子体放电行为，源于PEO初期形成的磷酸铝混合物膜层稳定性受到影响。占空比为5%时制备得到的PEO膜层较厚。磷酸铝绝缘膜的击穿诱发等离子体放电，阀金属的绝缘膜击穿理
论相对于气膜击穿理论更适用于Q345碳钢。抛光碳钢在5%占空比中制备得到的PEO 膜层腐蚀电流密度为1.474×10-6 A∙cm-2，耐蚀性最好。
Q345碳钢在硅酸盐体系中进行PEO处理时，在32 g /l Na2SiO3·9H2O + 2 g /l NaH2PO2·H2O和32 g /l Na2SiO3·9H2O中均能成功制备得到PEO膜层，Q345碳钢在32 g /l Na2SiO3·9H2O + 2 g /l NaH2PO2·H2O中初始阶段形成的混合物，成分可能为磷酸硅(SiP2O7、Si3(PO4)4和Si5P6O25)，是其接下来诱发等离子体放电的关键。Q345碳钢在32 g /l Na2SiO3·9H2O中制备得到的膜层厚度随电流密度增加呈现出先增加后减少的趋势，但电流密度过大会导致膜层损坏。Q345碳钢在32 g /l Na2SiO3·9H2O中由硅酸根离子放电分解及初始沉积的SiO2是PEO膜层形成的关键。在两种不同溶液中改变电解液状态，电解液的搅动促进了电解液中粒子的传质过程。Q345碳钢在32 g /l Na2SiO3·9H2O不同电流密度中制备得到的PEO膜层在中等电流密度下(0.772A∙cm-2)表现得更耐蚀，但在32 g /l Na2SiO3·9H2O + 2 g /l NaH2PO2·H2O中制备得到的PEO膜层耐腐蚀性能相对更好。
关键词：Q345碳钢；等离子体电解氧化；铝酸盐；硅酸盐；沉积层；放电模型；耐蚀性
Abstract
Plasma electrolytic oxidation (PEO) is also named micro-arc oxidation (MAO). Which is an advanced surface treatment technique for the forming of ceramic coatings on the so called valve metals (Al, M
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g, Ti and Zr, etc.) and their alloys. But the non-valve metals, such as iron, copper and nickel and their alloys. Which are difficult for the application of PEO technology. However, a few rearchers directly attempt to fabricate PEO coatings on carbon steel and make some progress. Some protective properties of PEO coatings were fabricated in aluminate bad electrolyte and silicate bad electrolyte respectively. But the coating formation mechanism and plasma breakdown behavior need to make an in-depth investigation. In this paper, the coating formation mechanism and accompanying PEO spark discharge behaviour of Q345 Carbon steel in aluminate bad electrolyte and silicate bad electrolyte are further investigated.
In order to inverstigate the different electrolyte components on the PEO behavior of Q345 Carbon steel in aluminate electrolytes, the PEO coatings can be successfully prepared in 8 g /l NaAlO2 + 2 g /l NaH2PO4, the high current density is benefit for coating formation in 8 g /l NaAlO2, It only leads to the dissolution of the metal substrate in 2 g /l NaH2PO4.It has been found that the formation of a layer of aluminum phosphates (AlPO4 and AlPO4·2H2O) or alumina aluminum phosphate (Al2O3·AlPO4) at the initial PEO stage plays an important role for the plasma generation and hence PEO coating formation on Q345 carbon steel. The surface roughness(polished or unpolished) and electrolyte state(stagnant electrolyte or agitated electrolyte) of the samples are adjusted in 8 g /l NaA
lO2 + 2 g /l NaH2PO4, Which are associated with the stability of the aluminum phosphates or alumina aluminum phosphate layer on the Q345 carbon steel. The duty cycle has some influences for the coating formation, It is clear that the coating formed at 5% duty cycle shows a thicker thickness. This dielectric layer of aluminum phosphates lead to the plasma breakdown behaviour. The dielectric breakdown of valve metals may be more suitable for Q345 Carbon steel than gas breakdown theory. It was found that the PEO film formed on polished carbon steel at 5% duty cycle has best corrosion resistance and the corrosion current was reduced to 1.474×10-6 A∙cm-2.
In order to inverstigate the coating formation on the PEO behavior of Q345 Carbon steel in silicate electrolytes, the PEO coatings can be successfully prepared in 32 g /l Na2SiO3·9H2O + 2 g /l NaH2PO2·H2O and 32 g /l Na2SiO3·9H2O, the formation of an initial silicon phosphate mixtures (SiP2O7、Si3(PO4)4 and Si5P6O25) is critical to thevicepresident
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establishment of plasma discharge. The thickness of the film prepared by Q345 carbon steel in 32 g /l Na2SiO3·9H2O has a trendency from increasing to decreasing, but the high current density caud the film damaged. The decomposition of silicate ions in discharge process and the initial depwhite christmas
osited layer of SiO2 are esntial for coating growth. The state of the electrolyte was changed in two different solutions, the agitation of electrolyte promotes the mass transfer of particles. It was found that the PEO film formed on Q345 carbon steel at moderate current density(0.772A∙cm-2) has better corrosion resistance than other conditions, but their corrosion resistance was poorer than the PEO coating formed in 32 g /l Na2SiO3·9H2O + 2 g /l NaH2PO2·H2O.
Key words: Q345 Carbon steel; Plasma electrolytic oxidation; Aluminate; Silicate; Sedimentary layer; Breakdown model; Corrosion resistance
目录
学位论文原创性声明和学位论文版权使用授权书............................................I 摘要...............................................................................................III 第1章绪论 (1)
1.1 课题背景和意义 (1)
1.2 等离子体电解氧化技术 (1)
1.2.1 等离子体电解氧化技术发展历程 (1)
1.2.2 等离子体电解氧化技术的原理和特点 (2)
1.2.3 等离子体电解氧化技术的影响因素 (6)
1.2.4 等离子体电解氧化技术的应用与发展趋势 (7)
师德师风演讲稿1.2.5 等离子体电解氧化技术存在的问题 (9)
1.3 阀金属等离子体电解氧化膜形成机理研究概况 (9)
1.4 钢铁等离子体电解氧化研究概况 (13)
1.5 论文研究目的和内容 (15)
成人高考有哪几种形式第2章实验材料与测试 (16)
2.1 实验材料 (16)
2.2 PEO膜的制备 (16)
2.2.1 实验设备 (16)
2.2.2 试样制备 (17)
2.2.3 电解液制备 (17)
2.3 试样测试与表征 (18)
2.3.1 电压电流波形测试 (18)
2.3.2 膜层形貌分析 (18)
2.3.3 膜层相成分分析 (18)
2.3.4 火花实时拍摄分析 (18)
2.3.5 光谱谱图分析 (18)
2.3.6 表面粗糙度测试 (19)
2.3.7 膜层电化学性能测试 (19)
第3章Q345碳钢在铝酸盐中PEO膜层制备与研究 (20)
3.1 Q345碳钢在铝酸钠与磷酸二氢钠中膜层的制备与研究 (20)tf是什么意思
3.1.1 PEO膜层时间电压曲线与波形 (20)
3.1.2 电解液搅拌对PEO膜层放电的影响 (21)
3.1.3 PEO膜层形貌与成分分析 (23)
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3.2 Q345碳钢在铝酸钠溶液中膜层的制备与研究 (28)
3.2.1 PEO膜层的时间电压曲线与火花形貌 (28)
3.2.2 PEO膜层形貌与成分分析 (30)
3.3 Q345碳钢在单独磷酸二氢钠溶液中的形貌与成分分析 (32)
3.4 Q345碳钢在不同电解液中的OES光谱分析 (33)
3.5 Q345碳钢在不同电解液中的气体收集 (34)
3.6 Q345碳钢PEO膜层的电化学测试 (35)
3.7 Q345碳钢PEO过程综合分析 (36)
3.7.1 Q345碳钢PEO膜层的形成过程 (36)
3.7.2 Q345碳钢PEO过程的放电行为 (40)
3.8 本章小结 (41)
第4章Q345碳钢在硅酸盐中PEO膜层制备与研究 (43)
4.1 Q345碳钢在硅酸钠与次亚磷酸钠中膜层的制备与研究 (43)
4.1.1 PEO膜层时间电压变化与电流波形 (43)
4.1.2 PEO膜层形貌与成分分析 (44)
4.2 Q345碳钢在硅酸钠中膜层的制备与研究 (48)
4.2.1 不同电流密度下的膜层电压变化 (48)
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4.2.2 PEO膜层形貌与成分分析 (49)
4.3 两种不同电解液中的PEO膜层XRD分析 (52)
4.4 不同电解液中的PEO膜层电化学测试 (53)
4.5 不同电解液中PEO膜层形成过程分析 (55)枫杨外国语
mineral>广播剧下载4.6 本章小结 (56)
结论 (57)
参考文献 (59)
致谢 (70)
附录A 攻读学位期间发表的学术论文目录 (71)
