纯铝及6061铝合金微弧氧化陶瓷层的微观结构和粗糙度

采用X射线衍射仪、扫描电镜、数字图像处理软件和表面粗糙度仪研究了纯铝和6061铝合金两种基体上微弧氧化(MAO)陶瓷层的构相、微观形貌、元素组成、厚度和粗糙度随微弧氧化时间的变化。结果表明,微弧氧化初期所得陶瓷层的主要相为γ-Al_2O_3,微弧氧化后期所得陶瓷层均存在W相、AlPO_4相和SiO_2相。随微弧氧化时间延长,MAO陶瓷层的厚度增大,纯铝表面MAO陶瓷层的生长速率大于6061铝合金表面MAO陶瓷层的生长速率;MAO陶瓷层的粗糙度受其结构和厚度的影响。     

钛合金微弧氧化钙磷生物膜层形成机制研究

为了利用微弧氧化工艺生成钛合金生物钙磷陶瓷涂层,使用微弧氧化电源,在恒电流条件下制备试样。通过电子扫描电镜和电子能谱仪观测不同氧化阶段涂层形貌和元素组成,膜层厚度变化特点,并分析各阶段微弧放电特性,研究了钛合金微弧氧化生成羟基磷灰石(钙磷)医用陶瓷涂层机制。结果表明,各阶段膜层放电特性不同,膜层先向外生长,后向内生长,且所生成膜层元素成分有区别,致使在微弧放电阶段才有钙磷生物成分生成。结论:若想获得高质量钙磷生物膜层,需使微弧氧化达到微弧放电阶段,但应避免进入弧光放电阶段,所得结论可对研究微弧氧化成膜过程起到一定的指导作用。     

不同电解液中镁合金微弧氧化膜生长过程及腐蚀防护性能EI北大核心CSCD

对AZ31镁合金在3种电解液(NaAlO_(2),Na_(2)SiO_(3),Na_(3)PO_(4))中进行微弧氧化处理,采用扫描电子显微镜和X射线能谱仪分析了不同电解液体系下微弧氧化膜的表面和截面形貌及其元素分布情况,采用X射线衍射分析了微弧氧化膜生长过程中物相组成的变化情况,利用电动位极化、电化学阻抗和析氢测试比较了不同电解液体系中制备的相同厚度(~15mm)氧化膜的腐蚀防护性能,并根据不同电解液体系中微弧氧化膜生长过程特点,探讨了氧化膜腐蚀防护性能差异的原因。结果表明:在铝酸盐中生长主要以阴离子化合物沉积为主,氧化膜倾向于向外生长,而在硅酸盐和磷酸盐中,这2种膜层的生长很大一部分来自于基体的氧化,导致其向内生长都占据了主要地位,不同的生长方式导致膜层对基体的腐蚀防护性能不同(AZ31-S>AZ31-P>>AZ31-Al)。     

不同电解液中镁合金微弧氧化膜生长过程及腐蚀防护性能

对AZ31镁合金在3种电解液(NaAlO_2,Na_2SiO_3,Na_3PO_4)中进行微弧氧化处理,采用扫描电子显微镜和X射线能谱仪分析了不同电解液体系下微弧氧化膜的表面和截面形貌及其元素分布情况,采用X射线衍射分析了微弧氧化膜生长过程中物相组成的变化情况,利用电动位极化、电化学阻抗和析氢测试比较了不同电解液体系中制备的相同厚度(～15mm)氧化膜的腐蚀防护性能,并根据不同电解液体系中微弧氧化膜生长过程特点,探讨了氧化膜腐蚀防护性能差异的原因。结果表明:在铝酸盐中生长主要以阴离子化合物沉积为主,氧化膜倾向于向外生长,而在硅酸盐和磷酸盐中,这2种膜层的生长很大一部分来自于基体的氧化,导致其向内生长都占据了主要地位,不同的生长方式导致膜层对基体的腐蚀防护性能不同(AZ31-SAZ31-PAZ31-Al)。     

Mg–Gd–Y系合金微弧氧化陶瓷层生长机理及耐蚀性

利用扫描电镜、X射线衍射等研究了Mg–11%Gd–1%Y–0.5%Zn(质量分数)合金微弧氧化陶瓷层的生长规律,分析了微弧氧化膜层相结构及不同生长阶段的耐蚀性。结果表明:在微弧氧化初期,膜层生长遵循直线规律,为典型的电化学极化控制的阳极沉积阶段;随处理时间的延长及膜层增厚,膜层生长符合抛物线规律,属微弧氧化阶段,较氧化初期比,生长速率慢;在弧光放电阶段,抛物线斜率增大,疏松层增厚,生长速率有所提高。微弧氧化疏松层主要以MgSiO3为主,致密层以MgO为主;微弧氧化各阶段,膜层耐蚀性随氧化时间增长而提高,到弧光放电阶段,耐蚀性有所降低。氧化时间为7～12min时,制备的膜层具有较好的耐蚀性。     

Q235钢热浸镀铝微弧氧化层的生长规律

微弧氧化是在普通阳极氧化技术基础上建立起来的一项高新技术，在Q235钢表面热浸镀铝后再进行微弧氧化获得一陶瓷层。研究了强化时间和电流密度对所得陶瓷层向内、向外生长厚度的影响，同时研究了陶瓷层向内与向外生长之间的关系。结果表明，微弧氧化陶瓷层向内与向外的生长比例受强化时间和电流密度综合控制。     

铸造铝合金微弧氧化膜的生长动力学及耐蚀性能

研究了ZL101铸造铝-硅合金微弧氧化陶瓷膜的生长动力学,探讨了膜生长厚度与电流密度(i)和生长速率(v)的关系.分析了膜的形貌和相组成,并用电化学法测量不同膜样品厚度的极化曲线.结果表明:膜生长分为3个阶段,氧化初期,i较高,但膜层生长较慢.在膜快速生长阶段,膜生长速率达到极大值.膜生长进入平稳期后,i基本保持恒定,样品的外部尺寸不再增加,膜逐渐转向基体内部生长.合金化元素硅的影响主要表现为氧化初期对膜生长的阻碍作用.铸造铝合金经过微弧氧化处理后,腐蚀电流大幅下降,极化电阻增加了几个数量级.较薄的微弧氧化膜同样大幅度提高了铝-硅合金的耐蚀性.     

溶质离子对AZ31B镁合金微弧诱发过程和陶瓷层结构的影响

采用微弧氧化方法在AZ31B镁合金表面制备了陶瓷层。研究了AZ31B镁合金微弧氧化溶液体系中KOH和Na2SiO3浓度对微弧等离子体诱发过程和陶瓷层微观结构的影响,通过涡流测厚仪、扫描电子显微镜和X射线衍射仪分析了陶瓷层的物相组成、微观形貌和厚度随KOH和Na2SiO3浓度的变化规律。研究表明:恒流模式下,KOH溶液在AZ31B镁合金表面诱发微弧时存在1个临界浓度,约为27mmol/L,且随着KOH浓度的增大,对基体和氧化膜的溶解作用加剧,影响微弧等离子体诱发的稳定性。Na2SiO3含量显著影响镁合金表面微弧诱发过程和陶瓷层的微观结构,随着Na2SiO3浓度的增大,陶瓷层生长速率增快,膜层表面由光滑转变为微孔结构,且孔径逐渐增大;Na2SiO3浓度在1.6~6.4mmol/L时陶瓷层中主要以MgO为主,Na2SiO3浓度大于16mmol/L时,Mg2SiO4和非晶相明显增多。     

镁合金微弧氧化工艺及陶瓷层耐蚀性能研究

通过单因素试验讨论了镁合金微弧氧化电解液各组分对成膜的作用,得到电解液最佳配方:10g/L(NaPO3)6,5g/LNH4F,6g/LKOH,6mL/LC3H8O3。用扫描电镜(SEM)、X射线衍射(XRD)和能谱(EDS)分析了陶瓷膜层的表面形貌、截面形貌、相组成及元素组成;采用点滴试验、交流阻抗和盐雾试验考察了陶瓷层的耐腐蚀性能。结果表明:膜层表面分布着大量均匀的放电微孔,孔径在1~3μm之间,膜层截面内层与基体过渡部分呈犬牙交错状态,结合良好;膜层由大量非晶态相及少量MgO组成,耐蚀性能优良。P与F元素的存在,证明了电解液组分较好地参与了微弧氧化反应。     

铝锂合金微弧氧化陶瓷膜层特性的研究

采用先恒流、后恒压的微弧氧化方法,在铝锂合金(添加微量稀土元素Ce)表面制备陶瓷化膜层.研究了氧化时间和脉冲频率对膜层生长过程和表面形貌的影响.结果表明:膜层厚度随着反应时间的延长而增加,在更高频率的高能脉冲作用下(＞600 Hz)生长速率更快;膜层表面多孔、起伏不平,延长反应时间或提高脉冲频率会导致烧蚀留下的坑洞变大,表面粗糙度亦随之增大;膜层与基体结合良好,由内部致密层和外部疏松层组成,总厚度可达50 μm;EDS分析表明,膜层由Al、O、Si构成,Si元素的摄入认为是NaOH-Na2SiO3电解液体系中的SiO32-参与反应进入膜层.     

Investigation of tribological properties of micro-arc oxidation ceramic coating on Mg alloy under dry sliding condition

To enhance wear resistance of Mg alloy, micro-arc oxidation (MAO) ceramic coatings on Mg substrate were prepared in silicate electrolyte under various currents. It was found that the surface roughness and thickness of MAO coating were increased with the increase of current. The dry tribological tests showed that the friction coefficient and wear resistance of thicker coatings (obtained under currents of 3?A and 4?A) were much higher than that of Mg alloy and the thin coating (obtained under current of 2?A), meanwhile the lifetime of the coating obtained under 4?A was longer than the other coatings under higher load. The wear type of thin MAO coating was slight abrasive wear under low load, whereas translated to severe adhesive wear under high load. While the main wear mechanism of thick MAO coating was slight abrasive wear or scratch under the given test condition, which was attributed to the thick intermediate layer improved load support for the soft substrate. The tribological study indicated that the MAO coating obtained under 4?A current had better wear resistance and life time due to its compact microstructure and thickness.     

Preparation and corrosion resistance of a self-sealing hydroxyapatite- MgO coating on magnesium alloy by microarc oxidation

An ideal self-sealing hydroxyapatite (HA)-MgO coating was designed on an AZ31 Mg alloy by one-step microarc oxidation (MAO) with the addition of HA nanoparticles into a base electrolyte. The formation mechanism of the self-sealing HA-MAO coating was discussed. The effect of the nano-HA addition on the corrosion resistance of the MAO coating was evaluated by corrosion tests in Hank's solution. The results show that HA nanoparticles inertly incorporated into the MAO coating during the process of coating growth. HA and MgO were the main constituents of the HA-MAO coating. The HA nanoparticles were absent in the inner barrier layer but concentrated in the outer porous layer. In addition, HA nanoparticles accumulated much more inside coating defects than in the other zones, which resulted in the nearly ideal sealing of micropores on the coating surface. By forming a denser and more stable outer layer, the incorporation of HA nanoparticles greatly enhanced the anti-corrosion properties of the MAO coating.     

涂覆工艺对金属基陶瓷涂层高温抗氧化性能影响的研究

将陶瓷粘结料与Cr2O3或重烧MgO制成料浆,采用刷涂、浸渍和喷涂三种涂敷方法和高温熔烧工艺制备金属基Cr2O3或MgO质高温抗氧化陶瓷涂层。研究了三种涂敷方法、涂层厚度对涂层试样高温抗氧能力的影响规律。结果表明:当料浆组成、涂层厚度和熔烧制度相同条件下,采用喷涂工艺所制备的涂层试样具有最佳的抗氧化能力,且Cr2O3和MgO质陶瓷涂层在1200℃、30h的抗氧化能力分别是金属基体的约62倍和16倍。采用SEM对涂层的显微结构进行了表征,揭示涂覆工艺与涂层结构和抗氧化能力之间的关系。     

铝-锰合金镀层的微弧氧化研究

在钢铁基体上采用熔盐电镀的方法获得铝-锰合金镀层,对镀层进行微弧氧化后制得铝-锰陶瓷膜。研究了不同质量浓度的硅酸钠电解液对铝-锰陶瓷膜厚度和硬度的影响;测定了相应质量浓度下的塔菲尔极化曲线,以此评价铝-锰陶瓷膜的耐蚀性;通过扫描电镜观察铝-锰陶瓷膜的微观形貌。     

Investigation on corrosion and wear resistance of MgO-Al2O3 composite coating prepared by plasma electrolytic oxidation

Ceramic coatings were prepared on 6061 Al alloy in a mixed electrolyte with/without MgO powders at different treatment durations. The results of energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD) showed that MgO powder was incorporated into the coatings, and Mg species gradually aggregated into coating inside as prolonging the oxidation time. Scanning electron microscopy (SEM) showed that MgO additive had a certain effect on the microstructures and coating thickness. The corrosion behavior tests evaluated by potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) in 3.5 wt% NaCl solution suggested that at the same treatment time, the addition of MgO powders can improve the corrosion resistance of the coating, and the Mg-rich layer can affect the corrosion resistance of the coating. The tests of mechanical properties showed that the addition of MgO powders improved the stability and hardness of the coating.     

镁钙砂表面沉积MgO涂层的动力学分析

采用MgO碳热还原和扩散氧化法在镁钙砂表面沉积MgO涂层,研究了MgO涂层的沉积动力学、微观形貌、生长机制以及涂层厚度对镁钙砂抗水化性能的影响。结果表明：随着反应温度的升高,沉积过程存在两个控制机理,在1400～1500℃之间,为化学动力学控制,反应为一级反应,活化能为97.82 kJ·mol^-1;在1500～1600℃之间,沉积过程为扩散控制,扩散活化能为19.18 kJ·mol^-1;MgO涂层以方镁石和方钙石为基底均呈二维台阶状生长,但二者生长机制并不完全相同;抗水化实验结果显示最佳处理温度为1600℃、沉积时间为6 h,镁钙砂水化质量增加率为0.02%,约是处理前的1/150。     

Growth and Corrosion Characteristics of Plasma Electrolytic Oxidation Ceramic Films Formed on AZ31 Magnesium Alloy

The growth characteristics of oxide ceramic films formed on AZ31 magnesium alloy with plasma electrolytic oxidation (PEO) technique in alkaline silicate solution were investigated. The composition, structure and morphology of the coatings were detected by energy dispersive X-ray spectroscope and scanning electron microscope. The amount of dissolved magnesium in the electrolytes during PEO process was measured by atomic absorption spectrometry. The results indicated that the growth process of PEO films had three stages when applied with constant voltage mode. In the first stage, the growth rate of PEO films was low, and concentrations of elements O, Mg and Si varied slightly. After sparking occurred (the second stage), the PEO films showed higher growth rate due to the high transfer rate of ions and electrons, and the existence of plasma reactions. When the growth rate tended to maintain stable with time, the third stage happened. PEO films exhibited different uniform and pitting-corrosion characteristics in different reaction stages. The films formed at 300 V for 30 min performed best corrosion resistance and the phase of ceramic films was mainly composed of MgSiO3 and forsterite Mg2SiO4.     

Effect of ultra accurate control of electrolyte temperature on the performance of micro arc oxidation ceramic coatings

The technique of micro arc oxidation (MAO) uses arc discharge and high-voltage breakdown to produce a ceramic layer on valve metal surfaces. However, the common method of MAO requires immersing the workpiece in an electrolyte solution, which can result in elevated temperatures due to the arc discharge, thus negatively affecting the coating's quality and performance. This article investigates the influence of electrolyte temperature on the performance of MAO ceramic coatings, with the assistance of a robotic arm enabling valve metal reaction without immersion in the electrolyte, and precise control of electrolyte temperature through a MAO temperature monitoring system. Various techniques, such as scanning electron microscopy (SEM), hardness testing, electrochemical corrosion experiments, and friction-wear experiments, were utilized to characterize the performance of the prepared coating. The results indicate a nonlinear correlation between the temperature of the electrolyte and the thickness and hardness of the ceramic coating. The corrosion and wear resistance of the MAO ceramic coatings initially improve with increasing electrolyte temperature but eventually deteriorate. At an electrolyte temperature of 40 °C, the MAO ceramic coating exhibits the optimal corrosion and wear resistance. The variation in electrolyte temperature affects the reactivity of the electrolyte ions, leading to changes in the morphology and properties of the resulting MAO ceramic coating. These findings offer valuable insights into the interaction mechanism between electrolyte temperature and the properties of the resulting MAO ceramic coating. This is of great significance in optimizing the MAO process for specific applications and improving the overall performance of ceramic coatings.     

Q235钢铁/AI-Ni镀层/微弧氧化陶瓷膜的性能研究

在Na2 SiO3溶液中,采用微弧氧化技术将钢铁基体上的A1-Ni合金镀层氧化为陶瓷膜.利用SEM观察Al-Ni陶瓷膜的表面形貌;利用Tafel极化曲线评价了A1-Ni陶瓷膜的耐蚀性;讨论了Na2 SiO3的质量浓度对陶瓷膜性能的影响.结果表明:Na2 SiO3的质量浓度对该陶瓷膜的厚度、硬度、耐蚀性均有一定的影响.     

Microstructural characteristic,outward-inward growth behavior and formation mechanism of MAO ceramic coating on the surface of ADC12 Al alloy with micro-groove

The ceramic coatings on the surface of aluminum alloy substrates with micro-grooves have been successfully fabricated in the silicate solution via micro-arc oxidation (MAO) approach. Microstructure characterization showed that the larger main discharge channels were located in the center of micro-groove, the smaller secondary discharge channels were located on both sides of main discharge channel; and a few irregular micro-pores existed in the vicinity of all discharge channels, which were mainly cause by the rapid cooling and solidification of discharge channels hindering the removal of gases produced via reaction. Moreover, the growing direction of coating in the initial stage was mainly outward-growth and resulted in the formation of inverted triangle coating structure, which was due to the sharp-angled effect. But in the final growing stage, the inward-growth behavior played a key role owing to the spark transfer. According to above results and discussion, the formation of smooth, uniform and homogeneous ceramic coating on the surface of whole trapezoidal micro-groove substrate contained four stages: anodic oxidation growth, sharp corner rapid growth, coating homogenization and groove self-filling.