NdFeB表面磁控溅射沉积Ti/Al多层膜的结构及耐腐蚀性能

采用直流磁控溅射技术在烧结NdFeB磁体表面沉积Ti/Al多层膜,并研究其结构及在NaCl溶液中的耐腐蚀性能。在Ti/Al多层膜中,Ti层为密排六方结构,成功打断了Al层(面心立方结构)的柱状晶结构生长。与纯Al膜相比,Ti/Al多层膜具有更致密的表面,且周期数增加,表面越平整致密。动电位极化曲线结果发现,纯Al膜试样的自腐蚀电流密度为1.9×10-5 A/cm-2左右,5周期Ti/Al多层膜试样的自腐蚀电流密度约为1.1×10-7 A/cm2,比纯Al膜小近两个数量级,且随着多层膜周期数的增加,其腐蚀电流密度进一步减小。这些结果表明在快速且破坏性强的腐蚀情况下,Ti/Al多层膜抗腐蚀能力比纯Al膜好,且随着周期数的增加进一步提高。NaCl溶液中长期腐蚀试验时,Ti/Al多层膜的耐腐蚀性能不如纯Al膜,这可能是由Ti层和Al层间形成原电池且多层膜应力较大导致。     

镁合金表面离子辅助蒸镀铝膜的耐蚀性研究

采用离子辅助热蒸镀技术在AZ91D镁合金表面沉积了厚度为100μm的单层铝膜及厚度为(25+25)和(50+50)μm的双层铝膜,并对试样表面进行喷丸+化学转化后处理,研究了铝膜的结构和耐蚀防护性能。结果表明:不同工艺的镀铝试样表面铝膜形貌相似,晶粒清晰、细小,呈柱状紧密排列,存在少许孔缝;双铝膜层中有明显的界面,界面处致密且结合紧密。经后处理,膜层表面致密性提高,并生成一层耐蚀化学转化膜。采用双层工艺铝膜能大幅度提高基体的耐腐蚀性能,100μm单层膜镀铝试样的盐雾寿命为6 h,(25+25)和(50+50)μm双层膜镀铝试样的盐雾寿命分别为72和460 h。(25+25)和(50+50)μm的镀铝试样自腐蚀电流密度分别为3.86×10-6和4.3×10-7A/cm~2,比基体降低了2~3个数量级。     

等离子体密度调控CrN薄膜结构改性Ti6Al4V双极板

目的 满足质子交换膜燃料电池双极板的使用要求。方法 采用热丝增强等离子体磁控溅射技术,通过改变热丝放电电流调控溅射等离子体密度,在Ti6Al4V（TC4）合金表面制备了氮化铬（CrN）薄膜。结果 随着热丝放电电流从0A增加至32A,真空腔内等离子体密度增强,-50V偏压下基体偏流密度从0.07 mA/cm²增至0.7 mA/cm²。CrN薄膜择优取向从低应变能的（111）转变成表面能更低的（200）择优取向。薄膜表面形貌由较疏松的四棱锥型转变成致密球形;无热丝时,CrN薄膜显示有铬的（110）衍射峰且铬原子数分数为52.16%,为富金属薄膜。热丝放电电流为16 A和32 A时,Cr N薄膜中的铬原子数分数分别降至50.79%和49.82%,且无Cr的衍射峰,即逐渐转变为贫铬。采用热丝辅助磁控溅射,将使氮气离化率增大,活性增强,引起薄膜贫铬。模拟双极板工作环境下,与TC4腐蚀电流密度1.5×10^-8 A/cm²相比,CrN薄膜的腐蚀电流密度由无热丝的3×10^-5 A/cm     

15CrMnMoVA钢磁控溅射镀铝防护层耐腐蚀性能

采用磁控溅射技术,在15CrMnMoVA钢上镀覆一层纯铝防腐蚀薄膜。利用盐雾机、电化学测量仪、扫描电镜和能谱仪对比基体和铝涂层样品的耐腐蚀性能,同时分析偏压、靶电流、沉积时间等因素对涂层耐腐蚀性能的影响。结果表明,铝膜厚度为8.2μm的样品,铝膜层晶粒均匀,大小为1～2μm、膜/基界面平整、结合良好,其中基体与膜层界面处致密的过渡层对提高样品的耐腐蚀性作用显著;在中性盐雾气氛中,516h出现红锈;Al膜沉积时间为1h的样品,其自腐蚀电流比基体低2个数量级,达到icorr=-6.53×10-8 A,能有效提高基体的耐腐蚀性,膜层在中性盐雾腐蚀气氛下失效方式为逐层失效;薄膜沉积过程中,提高负偏压、靶电流和镀膜时间,均能提高膜层的质量。     

离子辅助蒸发沉积镀铝膜的结构及耐腐蚀性

利用离子辅助热蒸发在45钢基材上制备纯铝防护膜,并对其进行喷丸+化学转化后处理。采用中性盐雾机、电化学工作站、扫描电镜、能谱仪对基体及镀铝试样的结构和性能进行研究。结果表明:45钢上铝膜厚度约12μm,膜层晶粒均匀,大小为1~2μm,膜层基体界面紧密,结合良好,膜基之间存在3μm厚的扩散层,扩散层的存在能显著提高基体的耐腐蚀性能。镀铝试样自腐蚀电流比基体低两个数量级,达到1.46×10-6A·cm-2,经盐雾试验1800 h,铝膜部分剥落,没有出现红锈。经过后处理(喷丸+化学转化)镀铝试样,膜层表层致密度提高,并生成一层耐腐蚀转化膜,耐蚀性能得到进一步提高,自腐蚀电流比基体低3个数量级达,达到2.3×10-7A·cm-2,经盐雾试验1800 h后,膜层较完整,没有出现腐蚀严重部位。     

30CrMnSiNi2A钢紧固件磁控溅射铝膜的腐蚀和氢脆性能

为提高30CrMnSiNi2A螺栓紧固件的耐腐蚀性能,采用磁控溅射技术在30CrMnSiNi2A试样和螺栓表面制备铝薄膜。采用SEM观察铝膜层的微观形貌。选取与镀铝薄膜厚度相同的氰化镀锌试样为对比件,采用电化学工作站和中性盐雾试验测试薄膜的耐腐蚀性能;采用氢脆试验测试基体和镀铝后处理试样的氢脆性能。结果表明:螺栓表面铝薄膜的厚度为7.26~10.47μm,厚度不均匀性为±17.2%;镀铝薄膜的螺栓耐盐雾腐蚀性能比氰化镀锌的耐腐蚀性能好;化学转化后处理和喷丸+化学转化复合后处理的镀铝螺栓的耐盐雾腐蚀性能优异,自腐蚀电流与30CrMnSiNi2A基体相比下降了1~2个数量级;磁控溅射镀铝薄膜和后处理工艺对30CrMnSiNi2A钢基体的氢脆性能没有影响。     

5052 铝合金表面钛锆基转化膜的制备及耐蚀性

目的研究铝合金表面非铬酸盐高耐蚀性转化膜的制备工艺。方法以K2Zr F6和K2Ti F6为主盐,KMn O4为氧化剂,Na F为成膜促进剂,在5052铝合金表面制备化学转化膜。采用SEM,EDS,FT-IR,XPS对转化膜的形貌、结构以及成分进行分析,通过硫酸铜点滴实验、全浸蚀实验和极化曲线对转化膜的耐蚀性进行研究。结果获得了土黄色转化膜,主要由Al F3·3H2O,Al Ox/Al,Al2O3,Mn O2和Ti O2组成。转化处理后,铝合金的腐蚀电位正移了约591 m V,腐蚀电流密度由1.10μA/cm2降低为0.48μA/cm2。经过封闭处理后,腐蚀电流密度降低为0.04μA/cm2,耐蚀性明显提高。结论以K2Zr F6和K2Ti F6为主盐在铝合金表面形成的土黄色化学转化膜具有良好的耐蚀性。     

杂质镓对纯铝表面锆钛转化膜的组织及耐腐蚀性能的影响

目的 探究杂质镓对纯铝锆钛转化膜的生长规律和防护性能的影响。方法 采用扫描电化学显微镜(SECM)技术表征了含镓纯铝表面锆钛转化膜在3.5%(质量分数)NaCl溶液中局部腐蚀的演变过程,结合X射线衍射仪(XRD)、X射线光电子能谱(XPS)、扫描电镜(SEM)等技术分析了镓对纯铝锆钛转化膜的组织及成分的影响规律,采用开路电位法(OCP)、电化学阻抗技术(EIS)以及极化曲线(Tafel)等探究了杂质镓对纯铝表面转化膜的生长和耐腐蚀性能的影响规律。结果 锆钛转化膜主要由冰晶石Na₃AlF₆、氧化物(如TiO₂、ZrO₂、Al₂O₃)和有机金属络合物组成;杂质镓的添加会抑制铝表面转化膜的生长,破坏膜层的完整性。随镓含量(质量分数)从0%增大到0.5%,锆钛转化膜阻抗值从4.75×10⁴?·cm²不断减小到2.49×10³?·cm²,自腐蚀电流密度由0.45μA增加到13.4...     

氮分压对钕铁硼表面直流磁控溅射沉积AlN/Al防护涂层结构和性能的影响

采用直流磁控溅射在钕铁硼表面沉积AlN/Al双层防护薄膜来提高磁体的耐腐蚀性能.先在基体表面沉积纯Al薄膜,然后沉积外层AlN薄膜.沉积AlN薄膜时,改变氮气分压,研究氮分压对薄膜结构和耐腐蚀性能的影响.结果显示,AlN纳米颗粒形成于内层Al结晶体表面.氮氩分压比为1:1时,钕铁硼表面形成了更致密的AlN/Al薄膜.膜基界面存在元素的互扩散和冶金结合.氮氩分压为1:1的AlN/Al防护薄膜具有最好的耐腐蚀性能.     

NdFeB表面磁控溅射沉积Al-Mn薄膜的耐蚀性

在钕铁硼(Nd Fe B)磁体表面利用磁控溅射沉积不同锰含量的铝锰合金薄膜。磁控溅射制备的铝锰合金薄膜表面光滑致密。薄膜结构受到锰含量的影响,当薄膜锰含量从6.80at%上升到25.78at%时,薄膜结构由晶态逐渐转变为非晶态,达到35.67at%时,薄膜中析出金属间化合物Al_8Mn_5。铝锰合金薄膜的耐腐蚀性能受薄膜成分变化的影响很大,当薄膜中锰含量达到25.78%时,此时薄膜呈非晶态结构,薄膜的自腐蚀电流密度达到1.198×10~(-7)A/cm~2,比钕铁硼基体降低了2个数量级,耐腐蚀性能最好。     

Corrosion behaviour of sintered NdFeB deposited with an aluminium coating

A protective, pure Al coating was deposited by direct current (DC) magnetron sputtering onto sintered NdFeB magnets. Separated, single phases of sintered NdFeB (the Nd-rich phase, the B-rich phase and the matrix phase) were prepared by arc melting for open circuit potential (OCP) tests. The corrosion process of the sintered NdFeB magnets coated with Al (Al/NdFeB) was studied experimentally. It was found that the corrosion process can be divided into three different stages. The Al coating cannot provide complete sacrificial protection for the sintered NdFeB magnets.     

Cold-Sprayed Al Coating for Corrosion Protection of Sintered NdFeB

A protective Al coating was achieved on the sintered NdFeB magnet by cold spray. The sprayed Al particles generate plastic deformation and hang together. The thickness of the coating is about 170 μm. The corrosion currents of Al coating and NdFeB without immersion tested by potentiodynamic polarization in 3.5 wt.% NaCl solutions are 1.350 × 10^?6 and 4.361 × 10^?6 A/cm², respectively. X-ray photoelectron spectrometry results confirm that the oxide film is Al₂O₃ and the corrosion process can be derived into two different stages. The Al coating can provide long-term protection for NdFeB effectively.     

Preparation and corrosion resistance of titanium–zirconium–cerium based conversion coating on 6061 aluminum alloy

This paper aims to develop a chromium-free chemical conversion coating with good corrosion resistance. A novel chemical conversion coating was prepared on 6061 aluminum alloy by dipping in the treatment solution containing titanium/zirconium based-ions and sodium metaphosphate and cerium nitrate hexahydrate as additives. The morphology and composition of the conversion coatings were observed by scanning electron microscopy and energy dispersive X-ray spectroscopy. The microarea structure of conversion coatings at different formation stages was analyzed by electron probe microanalyzer. The electrochemical polarization curve revealed that the corrosion potential of the conversion coating was −0.577 V and the corrosion current density was 0.1148 μA/cm². The equivalent circuit fitted by AC impedance showed that the film resistance reaches 68,140 Ω. The formation of coating preferentially grows on the Al (Fe) Si intermetallic to form oxides of Ti and Zr; then TiO₂ formed by a higher concentration of Ti⁴⁺ gradually covered ZrO₂. Ce³⁺ could adsorb on the intermetallic compound, the hydrolysis of which causes the local pH of the solution to decrease and promotes the aluminum alloy dissolved.     

粘结剂含量对粘结NdFeB磁体力学性能和磁性能的影响

粘结剂作为粘结NdFeB磁体制备过程中的重要组成部分,其作用是提高磁粉颗粒的流动性和粘结强度,保证产品的力学性能和磁性能的稳定。采用理论与实验相结合的方法,研究了粘结剂含量对粘结NdFeB磁体力学性能和磁性能的影响。在此基础上,制备了高性能粘结NdFeB磁体。利用扫描电子显微镜（SEM）对磁体的结构和形貌进行了表征。在NIM-200C磁滞回线仪和电子万能试验机（AG-X plus）上分别测定了环形粘结NdFeB磁体（RSM）的磁性能和力学性能。结果表明,当粘结剂含量为3%（质量分数）时,粘结NdFeB磁体密度最高（5.59 g/cm³）,抗压强度最高（159 MPa）,磁性能最佳。     

High-temperature magnetic properties of anisotropic MnBi/NdFeB hybrid bonded magnets

Anisotropic Mn Bi/Nd Fe B(Mn Bi contents of0 wt%, 20 wt%, 40 wt%, 60 wt%, 80 wt%, and 100 wt%)hybrid bonded magnets were prepared by molding compression using Mn Bi powders and commercial hydrogenation disproportionation desorption and recombination(HDDR) Nd Fe B powders. Magnetic measurements at room temperature show that with Mn Bi content increasing, the magnetic properties of the Mn Bi/Nd Fe B hybrid bonded magnets all decrease gradually, while the density of the hybrid magnets improves almost linearly. In a temperature range of 293–398 K, the coercivity temperature coefficient of the hybrid magnets improves gradually from-0.59 %áK~(-1)for the pure Nd Fe B bonded magnet to-0.32 %áK~(-1)for the hybrid bonded magnet with 80 wt%Mn Bi, and the pure Mn Bi bonded magnet exhibits a positive coercivity temperature coefficient of 0.61 %áK~(-1).     

Erosion–corrosion behavior of aluminum in a 50°C ethylene glycol aqueous solution simulating cooling water in HVDC transmission

The erosion–corrosion of aluminum in a 50 °C ethylene glycol aqueous solution (EGAS) was studied. Compared with that in deionized water, the corrosion of aluminum in an EGAS was inhibited to a certain extent. The corrosion potential, corrosion current, and charge transfer impedance of aluminum changed from −1.5776 V, 380.4 nA cm⁻², and 1.924 × 10⁻⁴ Ω cm⁻² in deionized water to −1.3127 V, 285.5 nA cm⁻², and 4.041 × 10⁻⁴ Ω cm⁻² in a 45.3 vt% EGAS, respectively. Ethylene glycol did not ionize in deionized water and the ionic conductivity of the EGAS was low, effectively restraining the corrosion of aluminum. However, a test with aluminum in an EGAS after long-term storage (9 days) showed that ethylene glycol gradually oxidized to glycolic acid, oxalic acid, and other substances, which slowly corroded the aluminum surface. Analysis results showed that the corrosion products on the surface of aluminum were Al(OH)₃ and Al₂O₃. The pitting hole formation mechanism of aluminum occurs via an aluminum–alcohol phase formed on the aluminum surface, which can inhibit the dissolution of the oxide film. Therefore, a suitably concentrated EGAS with a high heat capacity and low ionic conductivity similar to that of deionized water can be used as a coolant in airtight valve cooling systems for high-voltage direct-current transmission.     

Improving wear resistance and corrosion resistance of AZ31 magnesium alloy by DLC/AlN/Al coating

A novel protective coating, consisting of three layers (top: diamond-like carbon, middle: aluminum nitride, bottom: aluminum), was deposited on the surface of AZ31 magnesium alloy layer by layer. Nano-indenter, electrochemical system and tribological tester were performed to investigate the hardness, wear resistance and corrosion resistance of the coated AZ31 magnesium alloy, respectively. The DLC/AlN/Al coating improved the magnesium alloy's surface hardness and reduced its friction coefficient, which consequently induced a great improvement of the magnesium alloy's wear resistance. Furthermore, the corrosion resistance of the AZ31 magnesium alloy with the DLC/AlN/Al coating was also enhanced with the corrosion current density decreasing from 2.25 × 10⁻⁵ A/cm² to 1.28 × 10⁻⁶ A/cm² in a 3.5 wt.% NaCl solution.     

A comparative study on the corrosion behavior of NdFeB magnets in different electrolyte solutions

Sintered NdFeB magnets possess excellent magnetic properties. However, the corrosion resistance property of NdFeB is very poor due to its multiphase microstructure consisting of matrix phase Nd₂Fe₁₄B, Nd‐rich phase, and B‐rich phase. The corrosion behavior of NdFeB magnets in sodium hydroxide (NaOH), sodium chloride (NaCl), nitric acid (HNO₃), and oxalic acid (H₂C₂O₄) solutions was investigated by immersion and electrochemical tests. HNO₃is the strongest corrosive electrolyte compared with the other three solutions. The increase in HNO₃concentration can accelerate the corrosion of NdFeB magnets. NaCl belongs to medium corrosion electrolyte. A NaCl concentration of 0.5 M shows the severest corrosive feature in comparison with other concentrations of NaCl solution. NdFeB hardly suffers corrosion in NaOH and H₂C₂O₄solutions owing to the formation of passivation films on the surface of magnets. Based on the corrosion behavior of NdFeB in different electrolytes, the possible corrosion mechanisms are discussed.     

Primary investigation of corrosion resistance of Ni-P/TiO2 composite film on sintered NdFeB permanent magnet

In this paper, an electroless nickel plating and sol-gel combined technique used to prepare the Ni-P/TiO₂ composite film on sintered NdFeB permanent magnet is described and the composite film was characterized by X-ray diffraction (XRD), environmental scanning electron microscopy (ESEM), and energy dispersive X-ray spectrometer (EDX). The corrosion resistance of Ni-P/TiO₂ film was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The self-corrosion current density (i_corr) of Ni-P/TiO₂ composite film is 2.38μA/cm² in 0.5mol/L H₂SO₄ solution about 33% of that of Ni-P coating and 0.22μA/cm² in 0.5mol/L NaCl solution about 14% of that of Ni-P coating, respectively. In 0.5mol/L H₂SO₄ and 0.5mol/L NaCl solutions, the polarization resistance (Rp) of the composite film is 12.5kΩ cm² and 120kΩ cm², about 1.6 and 2 times that of Ni-P coating, respectively. The results indicate that Ni-P/TiO₂ composite film has a better corrosion resistance than Ni-P coating.