稀土对镁合金微弧氧化层的作用综述

镁合金具有密度小、比强度高、可回收、优异的铸造性能和切削加工性能等特点,在航空航天、交通工具、3C产品等领域具有十分广泛的应用前景。然而,镁合金的耐蚀耐磨性能差,限制了其更广泛应用。采用微弧氧化技术处理镁合金表面,来提高镁合金的耐蚀耐磨性能是近几年新兴的表面技术。在微弧氧化过程中,镁合金表面不断地陶瓷化,最终获得与镁合金基体结合紧密的致密耐蚀耐磨陶瓷层。本文介绍了镁合金微弧氧化反应原理,综述了稀土对镁合金微弧氧化层作用形式,包括前处理、作为添加剂添加在电解液中以及稀土合金化方式。探讨了稀土对镁合金微弧氧化层的影响作用,稀土通过影响微弧氧化过程、改变微弧氧化层的形貌和提高耐蚀相比例来改善微弧氧化层的耐磨耐蚀性能。指出今后可能的研究方向,通过选择电导率合适、降低Mg O熔点和粘度的稀土盐添加剂,从而提高微弧氧化膜层的致密性和耐蚀相比例,有利于镁合金微弧氧化层性能的改善。     

船用钛合金微弧氧化-电泳技术研究

随着钛及钛合金在以钢为主体建造材料的舰船装备中的广泛应用,采取有效技术措施防止钛-钢异种金属接触副发生电偶腐蚀变得尤为重要,而有资料表明,采用微弧氧化-电泳技术可以有效解决该问题。为此,对比了经微弧氧化、微弧氧化+水煮封孔、微弧氧化+电泳封孔三种工艺处理后的TA2、TA23、Ti80合金表面膜层的综合性能。研究表明,通过电泳技术可以实现对钛合金微弧氧化膜层表面疏松微孔的封闭,从而大幅度提高船用钛合金微弧氧化膜层的电绝缘性能等,并且从膜层横断面微观形貌可以看出,三种钛合金表面的微弧氧化膜层与电泳涂层之间有着良好的结合性。膜层结合强度测试结果显示,微弧氧化+电泳技术可满足对于结合强度要求较低的涂层的涂装。     

石墨含量对TC4钛合金微弧氧化膜的影响

在硅酸钠+磷酸钠体系溶液中添加不同含量的石墨粉,以其为氧化液对TC4钛合金进行表面微弧氧化。通过扫描电子显微镜、能谱仪、X射线衍射仪及摩擦磨损试验机,研究了石墨含量对TC4钛合金微弧氧化膜表面形貌、元素分布、相组成及摩擦系数的影响。结果表明,石墨含量的增加对TC4钛合金表面微弧氧化膜的形貌无太大影响,氧化膜层呈多孔结构,膜层表面有块状石墨颗粒分布;膜层中的Ti、P、O元素含量相对稳定,Si、C元素含量略有波动;膜层主要由TiO_2和Ti组成,石墨对膜层中TiO_2的形成有一定的阻碍作用;微弧氧化膜中的石墨颗粒能够起到一定的减摩作用,随着石墨含量的增加氧化膜的平均摩擦系数从0.85降至0.54。     

钛合金表面微弧氧化制备二氧化钛陶瓷膜的研究

采用微弧氧化法在钛合金表面制备二氧化钛膜层(即生物医学用陶瓷膜),利用SEM、XRD和EDX对膜层的物相结构、形貌和元素组成进行了分析。研究了电解液pH值和微弧氧化电压对微弧氧化过程的影响。结果表明:随着电解液pH值和微弧氧化电压的升高,膜层表面孔洞数量增加,孔径增大,膜层更加均匀;膜层主要由锐钛矿型和金红石型二氧化钛组成,且金红石相含量随微弧氧化电压的升高而增加;微弧氧化电流密度随氧化时间的延长先增大后减小,随电解液pH值的增大而增大。当电解液pH值为11、微弧氧化电压为500V时,可制得多孔状陶瓷膜,且其孔洞分布均匀。     

TC4钛合金微弧氧化膜层高温氧化性能研究

利用微弧氧化(MAO)技术在TC4钛合金表面原位制备陶瓷膜层,并通过硅酸钠水溶液对膜层进行了封孔处理。采用X射线衍射仪(XRD)分析了膜层相组成,通过扫描电子显微镜(SEM)观察了膜层表面形貌。通过粘结拉伸测试,比较了膜层在封孔前后与基体的结合强度。利用高温氧化实验,考察了TC4基体及膜层试样封孔前后的抗高温氧化性能。结果表明:微弧氧化膜层与基体间的结合强度较高,经封孔处理及高温氧化100 h后,膜基结合强度降低至4.29 MPa。与TC4基体相比,微弧氧化膜层的高温氧化增重量小,抗高温氧化性能得到了显著的提高。封孔处理提高了微弧氧化膜层的致密性,使其能更好地阻止氧透过膜层向基体内侵入,进一步提高了膜层的抗高温氧化性能。     

微弧氧化对TC4钛合金微动磨损行为的影响

采用微弧氧化技术,在TC4钛合金表面制备高硬度氧化陶瓷层(MAO),对比研究了TC4钛合金基体与微弧氧化陶瓷层在2种不同位移幅值下的微动磨损行为。结果表明:位移幅值由80μm增大到150μm时,TC4钛合金基体微动损伤机制由粘着磨损和磨粒磨损转变为疲劳磨损和氧化磨损,而微弧氧化陶瓷层的损伤机制始终以氧化磨损为主;位移幅值为80μm时,TC4钛合金基体与微弧氧化陶瓷层磨损量均较小,而摩擦系数大且波动大;位移幅值为150μm时,两者磨损量出现不同程度的增大,而摩擦系数略有下降且趋于平稳;与TC4钛合金基体相比,微弧氧化陶瓷层的平均摩擦系数小,磨损轮廓浅,且磨损量仅为钛合金基体的70%。微弧氧化陶瓷涂层能够保护钛合金基体表面,有效改善TC4钛合金耐磨性。     

表面活性剂对钛合金复合微弧氧化膜结构与耐磨性能的影响

为了在钛合金表面制备耐磨性能良好的复合微弧氧化膜层,研究了4种不同类型的表面活性剂对复合六方氮化硼(hBN)固体润滑微粒微弧氧化膜层微观结构及其耐磨性能的影响。结果表明,表面活性剂对复合微弧氧化(MAO)膜层的微观结构和耐磨性能有明显的影响,阳离子型表面活性剂十六烷基三甲基溴化铵降低了复合MAO膜层中h BN微粒含量,削弱了膜基结合,因而不利于膜层耐磨性能的改善;非离子型表面活性剂无水乙醇由于挥发性强导致膜层的致密性下降,降低了膜层的耐磨性能;阴离子型表面活性剂十二烷基苯磺酸钠对复合MAO膜层的结构和耐磨性能影响较小;阴离子型表面活性剂羧甲基纤维素钠则有效改善了hBN微粒在电解液中的分散性,进而改善其在MAO膜层中的复合及分布状况,从而明显改进了复合MAO膜层的耐磨性能。     

镁合金体育器械的表面改性与性能研究

采用磁控溅射和微弧氧化方法对AZ31B合金进行了表面改性处理,对比分析了AZ31B合金基体、磁控溅射Zr膜和微弧氧化ZrO_2膜的显微形貌、耐蚀性能和耐磨性能。结果表明:磁控溅射Zr膜与AZ31B合金基体实现了良好的冶金结合,界面处未见异常气孔或微裂纹存在,膜层厚度约为4μm;微弧氧化膜层表面存在随机分布的尺寸约在2～10μm的火山喷射状微孔。ZrO_2-AZ31B试样的表面硬度达到332.91 HV,相较于AZ31B合金基体提高422%,相较于Zr-AZ31B试样提高328%。Zr膜和ZrO_2膜从开始浸入直至最后的开路电位相较于AZ31B基体都更加稳定,且在相同时间下ZrO_2膜的开路电位最正;Zr膜和ZrO_2膜的腐蚀电位都相较于AZ31B合金基体发生了正向移动,腐蚀电流密度明显减小,经过磁控溅射和微弧氧化改性都可以提升AZ31B合金的耐蚀性能,且ZrO_2-AZ31B试样具有最佳的耐蚀性能;相较于AZ31B合金基体和Zr膜试样,ZrO_2膜试样的磨痕深度最浅、磨痕宽度和磨痕体积最小;无论在干摩擦还是在模拟人体汗液的湿摩擦条件下,比磨损率由高到低顺序为:AZ31合金基体Zr膜ZrO_2膜,微弧氧化ZrO_2膜具有相对更好的耐磨性能。     

硅酸钠在镁合金表面生成微弧氧化膜时的作用

分别在不添加和添加硅酸钠的电解液中采用微弧氧化(MAO)技术在AZ91D镁合金表面上制备膜层,研究微弧氧化过程中,电解液中的硅酸钠在镁合金表面形成微弧氧化膜层时的作用,分析电解液中硅酸钠的有无对微弧氧化膜层的影响。膜层的微观结构及物相组成分别通过扫描电镜(SEM)和X射线衍射仪(XRD)进行分析,膜层的耐蚀性通过电化学工作站来表征。结果表明:镁合金微弧氧化过程中,电解液中硅酸钠的加入,将会促使在基材表面生成具有平面连续性的完整的微弧氧化膜层,同时改善膜层的致密性,并获得优质新物相Mg_2SiO_4。随着电解液中硅酸钠的加入,溶液的电导率增大,基材表面的起弧电压降低,击穿变得容易发生。SiO_3~(2-)离子与电解液中的其他阴离子协同作用,使得阳极表面微观电位强弱区的对比态势加剧,从而促使放电火花的燃、熄两种状态在基材表面此起彼伏、交替进行,并由此加速了放电火花在基材表面的辗转游移,继而避免了局部热量累积有可能造成的宏观小凹坑的出现,以及微观裂纹的产生。电解液中加入硅酸钠后,所得膜层的腐蚀电流密度减小了1个数量级,线性极化电阻增大了约16倍,膜层的耐蚀性明显得到提高。     

钛合金微弧氧化技术研究进展

目前国内已建成世界上规模最大的钛工业体系,专注深化钛及钛合金的应用和使役行为探究,大力开发表面处理新技术提高使用寿命,其中,微弧氧化是最具代表性的表面改性技术,以其绿色环保的特点贯彻可持续发展战略。总结了国内外钛合金微弧氧化技术的研究成果,阐述了微弧氧化原理,综述了电解液、电参数和添加剂对钛合金微弧氧化的影响,以及钛合金微弧氧化陶瓷膜的耐腐蚀性、耐磨性及结合强度的研究进展,认为钛合金微弧氧化技术下一步研究重点需要加快研发节能电源装置,实现工件批量化生产,继续强化微弧氧化机理研究和工艺系统化设计,构建一个完整的技术库。     

镁锂合金表面含碳陶瓷层的摩擦性能

通过在Na₂SiO₃-KOH基础电解液中加入石墨烯添加剂,在镁锂合金表面制备出一层自润滑的含碳陶瓷层. 利用扫描电镜、原子力显微镜以及X射线衍射仪分析了陶瓷层的表面形貌、粗糙度以及物相组成,利用摩擦磨损试验仪对陶瓷层在室温下的摩擦学性能进行研究. 其结果表明,加入石墨烯后制备出的含碳陶瓷层表面放电微孔分布均匀,且其微孔尺寸和表面粗糙度均明显降低. 相比于镁锂合金,陶瓷层的表面硬度也得到明显的提高. 此外,含碳陶瓷层主要由SiO₂、Mg₂SiO₄以及MgO物相组成,而石墨烯则以机械形式弥散分布于陶瓷层中并起到减摩作用. 当石墨烯体积分数为1%时,陶瓷层表面显微硬度为1317.6 HV_{0.1 kg},其摩擦系数仅为0.09,其耐磨性明显提高. 同时,陶瓷层磨痕的深度和宽度均明显小于镁锂合金,而且较为光滑,表明陶瓷层表面没有发生严重的黏着磨损.      

Structure and Corrosion Resistance of Microarc Oxidation Coatings on AZ91D Magnesium Alloy

Magnesium alloys are widely used as shells of 3C (computer, mobile phone and consumer electronics) equipments for its impressive mechanical and physical properties, such as low density, good resistance to electromagnetic radiation, suitable for high pressure diecasting and easily recycling, etc. But poor corrosion resistance confines its extensively application. In this paper, protective coatings was successfully prepared on AZ91D magnesium alloys by micro-arc oxidation (MAO) and painting process. Microstructures and phases of MAO coatings were invesgated with scanning electron microscope (SEM) and X-Ray diffractometer. Mechanical properties of MAO coating, such as adhesive force and corrosion resistance, were also tested. Results showed that MAO coatings were a good base for painting process. MAO coatings with paint have good adhesive properties to base metal and excellent corrosion resistance. Micro-arc oxidation with painting process is a good kind of surface treatment to improve the corrosion resistance of mobile phone shell made of AZ91D magnesium alloys.     

Investigation of rare earth sealing of porous micro-arc oxidation coating formed on AZ91D magnesium alloy

Magnesium and its alloys have been used in many industries, but they are reactive and require protection against aggressive envi-ronments. In this study, oxide coatings were applied on AZ91D magnesium alloy using micro-arc oxidation (MAO) process. Then, in order to seal the pores of the MAO coatings, the samples were immersed in cerium bath for different times. The surface morphologies and composi-tions of the coatings were analyzed by scanning electron microscopy (SEM) and X-ray energy dispersive spectroscopy (EDS), respectively. The corrosion behavior of the coatings was investigated with electrochemical impedance spectroscopy (EIS) and potentiodynamic polariza-tion tests in 3.5 wt.% NaCl solution. The amount of the porosity of the coating was measured by electrochemical method. It was found that the sealing treatments by immersion in cerium bath successfully sealed the pores of the MAO coatings. The results of the corrosion tests showed that the MAO coating which was sealed in Ce bath for 10 min enhanced the corrosion resistance of the substrate significantly. Fur-thermore, this coating had the lowest amount of the porosity among the coatings.)     

热喷涂制备非晶合金涂层性能的研究进展

首先介绍了非晶合金的理论基础,然后从耐磨性和耐蚀性两个方面入手,详细地阐述了国内外对于热喷涂非晶合金涂层性能研究进展情况,并系统地总结了非金合金涂层在耐磨性和耐蚀性上的本质联系和根本矛盾,最后指出热喷涂非晶合金涂层性能研究上的局限性,提出三点问题:对于非晶合金基础理论的研究还处在起步阶段、热喷涂制备非晶合金涂层的合金体系种类少、制备非晶合金涂层的热喷涂技术有待开发,并针对以上三点问题提出热喷涂制备非晶合金涂层性能研究的未来发展方向。      

Wear of Plasma Sprayed Conventional and Nanostructured Al<Subscript>2</Subscript>O<Subscript>3</Subscript> and Cr<Subscript>2</Subscript>O<Subscript>3</Subscript>, Based Coatings

An ever increasing demand for high-performance ceramic coatings has made it inevitable for developing techniques with precise control over the process parameters to enable the fabrication of coatings with the desired microstructure and improved structural properties. The literature on plasma sprayed nanostructured ceramic coatings such as of Al₂O₃, Cr₂O₃, and their composites obtained using reconstituted nano sized ceramic powders has been reviewed in this study. Ceramic coatings due to their enhanced properties are on the verge of replacing conventional ceramic coatings used for various applications like automotive systems, boiler components, power generation equipment, chemical process equipment, aircraft engines, pulp and paper processing equipment, land-based and marine engine components, turbine blades etc. In such cases, the advantage is greater longevity and reliability for realizing the improved performance of ceramic coatings. It has been observed that the plasma sprayed nanostructured ceramic coatings show improvement in resistance to wear, erosion, corrosion, and mechanical properties as compared to their conventional counterparts. This article reviews various aspects concerning the plasma sprayed ceramic coatings such as (i) the present understanding of formation of plasma-spray coatings and factors affecting them, (ii) wear performance of nanostructured Al₂O₃, Cr₂O₃ and their composite ceramic coatings in comparison to their conventional counterparts, and (iii) mechanisms of wear observed for these coatings under various conditions of testing.     

电弧喷涂含陶瓷颗粒铝基复合涂层的微结构和性能

采用5052半硬铝带分别包覆Al_2O_3、SiC、B_4C、TiC陶瓷颗粒制备的粉芯丝材进行电弧喷涂试验,制备了含陶瓷颗粒的铝基复合涂层。利用光学显微镜、XRD分析了涂层的微观组织和相结构,测试了复合涂层的显微硬度、耐磨性及耐腐蚀性。研究结果表明,制备的铝基复合涂层中含有一定数量的未熔陶瓷颗粒,涂层较为致密,无明显缺陷。含陶瓷铝基涂层的物相主要由Al和所添加的陶瓷相构成,其中在含B_4C陶瓷涂层中还存在Al_3BC、Al_4C_3和AlB_2等新相。陶瓷颗粒的加入有利于提高铝基复合涂层的显微硬度,其中B_4C的加入使涂层中基体相显微硬度提高了1.5倍,这是由于B_4C陶瓷和Al反应生成Al_3BC、Al_4C_3和AlB_2硬质相。复合涂层的耐磨性均优于纯铝涂层,摩擦磨损的形式主要为粘着磨损。动电位极化腐蚀试验表明,含SiC和TiC陶瓷涂层具有较低的腐蚀电流,耐蚀性较好,含SiC陶瓷的复合涂层出现了明显的钝化现象。     

再造纳米小颗粒 给力传统大工业

随着纳米科学技术的快速发展,纳米材料被成功地应用到热喷涂领域。研究表明,热喷涂纳米陶瓷涂层比传统陶瓷涂层具有更高的结合强度、韧性、热震性能、耐磨抗蚀性能和可加工性。这种热喷涂纳米陶瓷涂层是利用纳米粉末为原料经过特殊的再造粒过程得到可喷涂喂料,然后方可制备出纳米结构陶瓷涂层。与传统微米结构陶瓷涂层相比,该纳米陶瓷涂层的韧性、结合强度、抗热震性能高1～2倍,耐磨性能高4～8倍,抗疲劳性能提高10倍。发展这样的国际领先的先进表面工程新材料技术,对推动我省的科技和产业发展无疑有重大的战略和经济意义。可以促进我省传统产业的结构调整和产品的升级换代,可以提高我省产品的市场竞争力和我省企业的活力和经济效益。     

硼化钼基涂层的制备及耐磨抗蚀性能研究

针对连续热镀锌生产线中沉没辊、 轴套等零部件的腐蚀磨损问题, 采用造粒烧结制备了 MoB-Al2O3(MA) 复合陶瓷粉末 , 采用等离子喷涂工艺制备了 MA 复合陶瓷涂层, 测试了涂层的显微组织、 显微硬度及耐熔融锌液 腐蚀磨损性能。 结果表明, 涂层显微组织均匀, 显微硬度约 1300HV100。 采用细粒度粉末、 粘结底层和封孔工艺 制备的 MA 涂层具有更好的抗腐蚀磨损能力, 经腐蚀磨损试验后涂层保持完整, 没有发生明显的腐蚀磨损。     

Friction Stir Surfacing Route: Effective Strategy for the Enhancement of Wear Resistance of Titanium Alloy

Titanium alloys are widely used in aerospace applications due to their properties like high strength to weight ratio, good corrosion and creep resistance. Poor wear resistance of these alloys limits their use in tribological applications. Friction surfacing technique is now recognized as an effective solution to surface engineer the light weight high strength alloys to make them suitable for general engineering applications involving wear and corrosion. The present work pertains to a study on wear resistance of surface coating of boron carbide on Ti–6Al–4V alloy using friction surfacing technique. Coating was formed by placing the boron carbide powder into the holes of predetermined depth on the surface and was characterized by metallography, electron probe micro analysis and dry sliding wear testing. The present study revealed that titanium alloy could be friction surfaced with boron carbide powder. The coating exhibited excellent wear resistance, which is attributed to the formation of strong metallurgical bond with the substrate. In the present work an attempt has also been made to compare the wear behaviour of surface composite layer on titanium alloy with that of conventionally used engineering materials such as mild steel and austenitic stainless steel. Wear data clearly revealed that wear resistance of friction stir surfaced composite layer is better than that of mild steel and stainless steel. This study demonstrated that friction stir surfacing is an effective strategy for the enhancement of wear resistance of titanium alloys.