Mechanical and corrosion properties of Al/Ti film on magnesium alloy AZ31B

Preparation of titanium film on magnesium substrate faces a challenge due to non-Fickian inter-diffusion between titanium and magnesium. Aluminum can build a bridge between titanium and magnesium. Al/Ti duplex coatings were deposited on magnesium alloy AZ31B using magnetron sputtering (MS). The low temperature diffusion bonding behavior of the Mg/Al/Ti coating was investigated through SEM and its affiliated EDS. The phase structure and critical load of the coatings were examined by means of XRD and scratch tests, respectively. The results demonstrated that the bonding strength was significantly improved after a post heat treatment (HT) at a temperature of 210°C. The diffusion mechanism of the interfaces of Mg/Al and Al/Ti in the coating was discussed based on the analysis of formation energy of vacancies and diffusion rates. The Al/Ti dual layer enhanced the corrosion resistance of the alloy. And the HT process further increased the corrosion resistance of the coated alloy. This result implies that a post HT at a lower temperature after MS is an effective approach to enhance the bonding strength and corrosion resistance of the Al/Ti film on Mg alloys.     

不同表面处理工艺压铸镁合金涂层耐蚀性研究

为了研究不同表面处理工艺下压铸镁合金涂层的抗腐蚀性能,通过浸泡腐蚀和电化学腐蚀的方法,比较了微弧氧化和无铬化学氧化等表面处理试样的耐蚀性.结果表明,无铬化学氧化和微弧氧化处理能显著提高镁合金表面耐蚀性,而以微弧氧化处理更优;且两种处理方法覆盖层对孔洞、裂纹不敏感.根据交流阻抗图谱,拟合得到了微弧氧化、无铬化学氧化和未处理三种试样电化学腐蚀时体系的等效电路,拟合结果与实测结果吻合.XRD分析表明这两种处理方法得到的覆盖层中主体相均为Mg3Al2Si3O12等含硅的尖晶石型氧化物和Mg0.36Al2.44O4、MgAl2O4等不含硅的镁、铝复合氧化物,有利于提高镁合金耐蚀性.     

AZ31镁合金表面磁控溅射Zr(Al,Ti)-SiN_x复合薄膜及其耐蚀性能

镁合金表面沉积薄膜可以提高其耐蚀性,但现有的几种沉积方法得到的膜疏松、与基体结合力差,影响了其耐腐蚀性能.为此,采用磁控溅射法在AZ31镁合金表面制备了Al,Zr,Ti膜及其与SiN_x的复合薄膜.用扫描电镜、X射线衍射、XPS研究了金属膜及其与SiNi_x复合薄膜的晶体结构、表面形貌和化学成分.结果表明:所制备的SiN_x薄膜为非晶态的富N膜;Zr膜的耐腐蚀性最好,Al膜的保护性最差;Zr-SiN_x复合薄膜比AZ31镁合金的腐蚀电流密度降低了3个数量级,Ti-SiN_x复合薄膜在阳极极化区出现了钝化.SiN_x复合薄膜的耐腐蚀性优于AZ31镁合金和单一金属膜.     

温度对AZ31B镁合金植酸转化膜性能的影响

为了探讨转化温度对镁合金防腐蚀性能的影响,应用析氢试验、Tafel分析法及SEM,EDS,FTIR研究了不同植酸液温度所形成的转化膜的防腐蚀性能及表面微观形貌、元素组成及官能团构成。结果表明转化温度对镁合金植酸转化膜的防腐蚀性能有较大的影响：在较低范围内,转化膜的防腐蚀性能随着温度的升高而增加,转化温度为40℃时,转化...     

Biodegradable poly(lactide-co-glycolide) coatings on magnesium alloys for orthopedic applications

Polymeric film coatings were applied by dip coating on two magnesium alloy systems, AZ31 and Mg4Y, in an attempt to slow the degradation of these alloys under in vitro conditions. Poly(lactic-co-glycolic acid) polymer in solution was explored at various concentrations, yielding coatings of varying thicknesses on the alloy substrates. Electrochemical corrosion studies indicate that the coatings initially provide some corrosion protection. Degradation studies showed reduced degradation over 3 days, but beyond this time point however, do not maintain a reduction in corrosion rate. Scanning electron microscopy indicates inhomogeneous coating durability, with gas pocket formation in the polymer coating, resulting in eventual detachment from the alloy surface. In vitro studies of cell viability utilizing mouse osteoblast cells showed improved biocompatibility of polymer coated substrates over the bare AZ31 and Mg4Y substrates. Results demonstrate that while challenges remain for long term degradation control, the developed polymeric coatings nevertheless provide short term corrosion protection and improved biocompatibility of magnesium alloys for possible use in orthopedic applications.     

AZ91镁合金表面MgFe_2O_4薄膜的溶胶-凝胶法制备及其耐蚀性能

MgFe2O4耐酸耐碱,但目前还未见将其制成镁合金防腐蚀涂层的报道。采用溶胶-凝胶法在AZ91镁合金表面制备了MgFe2O4薄膜,利用正交试验研究了镀膜层数、溶胶中Mg2+与Fe3+的摩尔比、烧结温度、烧结时间对AZ91镁合金膜试样自腐蚀电流密度的影响,得出最优方案,并研究了优化条件制备的膜试样的组织结构及耐蚀性。结果表明:各因素对AZ91镁合金膜试样自腐蚀电流密度的影响程度由大到小依次是镀膜层数、烧结温度、nMg2+/nFe3+、烧结时间;最优条件是镀膜1层,nMg2+/nFe3+=0.35,烧结温度400℃,烧结时间5 h;与AZ91镁合金基体相比,优化条件制备的MgFe2O4薄膜的自腐蚀电流密度降低了1个数量级,自腐蚀电位正移了690 mV,耐腐蚀性能得到很大提高。     

Bioactive Ca–P coating with self-sealing structure on pure magnesium

Bioactive coatings containing Ca and P with self-sealing structures were fabricated on the surface of pure magnesium using micro-arc oxidation technique (MAO) in a specific calcium hydroxide based electrolyte system. Coatings were prepared at three applied voltages, i.e. 360, 410 and 450 V, and the morphology, chemical composition, corrosion resistance and the degradation properties in Hank’s solution of the MAO-coated samples with three different applied voltages were investigated. It was found that all the three coatings showed similar surface morphologies that the majority of micro-pores were filled with compound particles. Both the porous structures and the compound particles were found to contain consistent chemical compositions which were mainly composed of O, Mg, F, Ca and P. Electrochemical tests showed a significant increase in corrosion resistance for the three coatings, meanwhile the coating obtained at 450 V exhibited the superior corrosion resistance owing to the largest coating thickness. The long term immersion tests in Hank’s solution also revealed an effective reduction in corrosion rate for the MAO coated samples, and the pH values of the coated samples always maintained a lower level. Besides, all the three coatings were subjected to a mild and uniform degradation, while the coating obtained at 360 V showed a relatively obvious degradation characteristic and appreciable Ca and P contents on the surfaces of the three coatings were observed after immersion in Hank’s solution. The results of the present study confirmed that the MAO coatings containing bioactive Ca and P elements with self-sealing structures could significantly enhance the corrosion resistance of magnesium substrate in Hanks’ solution with great potential for medical application.     

Formation of high heat resistant coatings by using gas tunnel type plasma spraying

Zirconia sprayed coatings are widely used as thermal barrier coatings (TBC) for high temperature protection of metallic structures. However, their use in diesel engine combustion chamber components has the long run durability problems, such as the spallation at the interface between the coating and substrate due to the interface oxidation. Although zirconia coatings have been used in many applications, the interface spallation problem is still waiting to be solved under the critical conditions such as high temperature and high corrosion environment. The gas tunnel type plasma spraying developed by the author can make high quality ceramic coatings such as Al2O3 and ZrO2 coating compared to other plasma spraying method. A high hardness ceramic coating such as Al2O3 coating by the gas tunnel type plasma spraying, were investigated in the previous study. The Vickers hardness of the zirconia (ZrO2) coating increased with decreasing spraying distance, and a higher Vickers hardness of about Hv = 1200 could be obtained at a shorter spraying distance of L = 30 mm. ZrO2 coating formed has a high hardness layer at the surface side, which shows the graded functionality of hardness. In this study, ZrO2 composite coatings (TBCs) with Al2O3 were deposited on SS304 substrates by gas tunnel type plasma spraying. The performance such as the mechanical properties, thermal behavior and high temperature oxidation resistance of the functionally graded TBCs was investigated and discussed. The resultant coating samples with different spraying powders and thickness are compared in their corrosion resistance with coating thickness as variables. Corrosion potential was measured and analyzed corresponding to the microstructure of the coatings. Keywords: High Heat Resistant Coatings, Gas Tunnel Type Plasma Spraying, Hardness,     

ZrO2涂层成分对其抗热腐蚀能力的影响

本文研究等离子喷涂不同成分ZrO_2涂层的抗热腐蚀能力。结果表明,熔盐热腐蚀过程表现为涂层表面的熔盐渗入内部和熔盐热分解产生的腐蚀气体向涂层内部扩散两个方面。在ZrO_2中添加适量的SiO_2,可显著提高涂层的抗热腐蚀能力。Y_2O_3稳定ZrO_2的效果比CaO好,因为在相同热腐蚀条件下,CaO与熔盐反应,使ZrO_2从四方相转变为单斜相。     

纯Mg表面TiO_2薄膜的耐蚀性研究

以四氯化钛为前驱体,去离子水为溶剂,盐酸为抑制剂,采用溶胶-凝胶法制得TiO2溶胶。采用浸渍-提拉技术在纯镁基体上制得TiO2薄膜,以提高纯镁基体的耐蚀性。通过正交实验,以电化学阻抗值作为评价标准,研究了热处理温度、涂层次数、溶胶浓度对试样耐腐蚀性的影响。结果表明,溶胶浓度为0.5%、涂层次数为3、热处理温度为100℃时得到的TiO2薄膜具有最好的耐蚀性。     

AZ31B镁合金铈基-植酸复合转化膜研究

为了进一步提高镁合金转化膜防腐性能的影响,将铈基转化复合于在AZ31B镁合金植酸转化膜表面,制备了一种铈基一植酸复合转化膜,应用析氢实验、Tafel分析方法及SEM、EDS对AZ31B镁合金不同转化膜的防腐性能及表面微观结构及成份进行了研究。结果表明复合转化膜表面主要由C、O、P、Ce、Mg及Al元素所组成,复合转化膜相比于植酸转化膜及铈基转化膜具有更好的致密性,从而复合转化膜相比于植酸转化膜及铈基转化膜具有更好的防腐性能。     

新型Mg-Zn-Y-Nd-Zr镁合金表面复合涂层的耐腐蚀性能

为了控制镁材及镁合金在人体中的生物降解速率,采用微弧氧化法、电化学沉积法及微弧氧化+电化学沉积法在新型Mg-Zn-Y-Nd-Zr镁合金表面制备了3种涂层。利用JSM-5610V扫描电子显微镜、TESCANTS5130 SB能谱分析仪、Bruker D8 ADVANCE X射线衍射仪、VS-2005涂层附着力自动划痕仪、RST200F电化学工作站对3种涂层的形貌、成分、结构、厚度、结合力以及电化学性能进行了检测。结果表明:3种涂层均能提高新型Mg-Zn-Y-Nd-Zr镁合金的电化学性能,改善其耐蚀性;微弧氧化+电化学沉积层较单一微弧氧化层及电化学沉积层在致密性、结晶度、厚度、结合力、耐腐蚀性能方面都具有更强的指标。     

微波辅助法制备镁合金的植酸镁/羟基磷灰石复合涂层及其耐蚀性能

采用微波辅助法在AZ31镁合金表面制备了植酸镁/羟基磷灰石(PA/HA)复合涂层。利用FESEM、EDS、XRD和电化学性能测试等方法表征涂层的表面形貌、物相组成以及耐蚀性能,探究了植酸溶液的pH值对PA/HA复合涂层形貌及耐蚀性能的影响,并通过浸泡实验研究了镁合金及PA/HA复合涂层在模拟体液(SBF)中的降解矿化行为。结果表明:在植酸预处理中,植酸溶液的pH=5.0时制备得到的PA/HA复合涂层表面均匀、无裂纹,与镁合金基底的界面结合良好;并且在此pH值下PA/HA复合涂层包覆镁合金样品的交流阻抗最大,自腐蚀电流密度最小,说明其耐蚀性最好。在SBF中,PA/HA复合涂层能够快速诱导磷灰石的生成,并显著提高镁合金基底的耐蚀性能。     

AZ31镁合金的SiO2（Mg）涂层的组织及性能研究

采用机械合金化的方法在AZ31镁合金表面涂覆SiO₂（Mg）涂层。通过XRD、显微硬度计、扫描电镜等测试手段对表面涂层的微观形貌结构、涂层的显微硬度进行分析,利用电化学工作站对涂覆前后的AZ31镁合金的耐蚀性能进行检测。结果表明:SiO₂涂层被成功地涂覆到AZ31镁合金表面;同时,随着球磨时间的增加,涂层的显微硬度呈增加趋势,且随着球料比的增加,显微硬度亦增加,最高达到370.6HV,较基体提高了15.2%;涂层的厚度也呈现先增加后趋于稳定的趋势,但球磨时间过长,涂层内部出现裂纹;当球料比为15:1、球磨时间为15 h时,所制备涂层厚度为148μm,涂层致密且与基体结合较好;所对应的自腐蚀电流密度较基体降低了一个数量级,对应的腐蚀电压提高了6.5%,耐腐蚀性能得到明显改善。      

Ti6Al4V钛合金表面Ta2O5/Ta2O5-Ti/Ti多涂层的制备与性能研究

采用磁控溅射技术在Ti6Al4V钛合金表面制备了Ta_2O_5/Ta_2O_5-Ti/Ti多层涂层;利用扫描电子显微镜(SEM)、X射线衍射仪(XRD)和X射线光电子能谱仪 (XPS),分析了涂层的微观结构、物性组成和化学价态;通过划痕仪、纳米压痕仪、摩擦磨损试验机和电化学工作站,检测了涂层的结合强度、力学性能、摩擦系数和耐腐蚀性。研究结果表明,Ta_2O_5/Ta_2O_5-Ti/Ti多层涂层表面由峰型颗粒组成,粒径大小均匀,涂层结构致密。与Ti6Al4V相比,Ta_2O_5/Ta_2O_5-Ti/Ti多层涂层试样具有较小的摩擦系数,较高的腐蚀电位和较小的腐蚀电流密度,表现出良好的耐磨和耐腐蚀性能,能对Ti6Al4V合金植入材料起到较好的保护作用。     

Verschleiß- und Korrosionsschutz durch Chrom und Chromnitrid (PVD-Abscheidung auf Al und Mg)

Wear and corrosion protection using Cr and CrN (PVD coating on Al and Mg) Investigations of the wear behaviour of uncoated Magnesium and Aluminium alloys (AZ 91hp, AlSi 7Mg) are showing very high wear rates of these materials. To improve the wear behaviour both materials were coated with 9 μm CrN using PVD (Physical Vapour Deposition) technology. The tribological behaviour of the coated light metals was tested afterwards by using a plate on cylinder tribometer. Looking at the results, wear is reduced enormously. The great number of defects in the coating of the magnesium alloy is showing almost no influence to the wear behaviour. The corrosion behaviour of chromium and chromium nitride coatings was tested on the magnesium alloy. Because of the defects in the coating, caused by defects like pores in the magnesium, only a short term protection of the alloy can be achieved. The corrosion behaviour of multilayer coatings is better than the behaviour of single layer coatings.     

双向脉冲快速电沉积非晶态Ni-P/Al_2O_3复合镀层

采用双向脉冲电沉积法制备出高P非晶态Ni-P/Al_2O_3复合镀层,利用扫描电镜(SEM)和能谱分析(EDS)方法考察镀层的微观形貌和化学组成,采用X射线衍射技术(XRD)表征镀层的相结构,并通过分析金属镀层和复合镀层的电化学测试结果,评价不同种类镀层的耐腐蚀能力。结果表明:与直流电沉积法相比,双向脉冲电沉积法可将镀层中的P含量提高至12.06%(质量分数),有利于非晶态Ni-P合金镀层的形成。采用双向脉冲法制备的Ni-P/Al_2O_3复合镀层比直流电沉积法制备的Ni-P/Al_2O_3复合镀层更平整、结晶更致密。脉冲电沉积法制备的非晶态Ni-P合金镀层具有更好的耐蚀性,而且复合微粒Al_2O_3的加入,对进一步提高非晶态Ni-P合金镀层的耐蚀性有积极作用。     

AZ91D镁合金表面植酸转化时间对膜组织结构及耐蚀性的影响

为了进一步探讨工艺条件对镁合金表面植酸转化膜的影响,采用扫描电镜、能谱分析、点蚀试验和电化学测量等研究AZ91D镁合金表面不同成膜时间对植酸转化膜表面形貌、成分及其耐蚀性的影响规律.结果表明:植酸转化膜主要由Mg,Al,O,P,C元素组成,其中Mg的质量分数随成膜时间的延长而减小,而P的质量分数随成膜时间的延长逐渐增大...     

镁合金微弧氧化-溶胶凝胶复合膜层的耐蚀性

用微弧氧化和溶胶凝胶法在AZ91D镁合金表面制备复合膜层,用扫描电镜(SEM)、能谱分析(EDS)、X射线衍射(XRD)和电化学测试等分析手段表征其成分、相结构和截面形貌,研究了复合膜层的耐蚀性.结果表明,溶胶凝胶膜有效地封闭了镁合金表面微弧氧化膜的微孔,形成结合力好且较为致密的复合膜层.复合膜层的组成主要有MgO、M...     

Effects of hydroxyapatite/Zr and bioglass/Zr coatings on morphology and corrosion behaviour of Rex-734 alloy

To improve corrosion resistance of metallic implant surfaces, Rex-734 alloy was coated with two different bio-ceramics; single-Hydroxyapatite (HA), double-HA/Zirconia(Zr) and double-Bioglass (BG)/Zr by using sol–gel method. Porous surface morphologies at low crack density were obtained after coating and sintering processes. Corrosion characteristics of coatings were determined by Open circuit potential and Potentiodynamic polarization measurements during corrosion tests. Hardness and adhesion strength of coating layers were measured and their surface morphologies before and after corrosion were characterized by scanning electron microscope (SEM), XRD and EDX. Through the SEM analysis, it was observed that corrosion caused degradation and sphere-like formations appeared with dimples on the coated surfaces. The coated substrates that exhibit high crack density, the corrosion was more effective by disturbing and transmitting through the coating layer, produced CrO₃ and Cr₃O₈ oxide formation. It was found that the addition of Zr provided an increase in adhesion strength and corrosion resistance of the coatings. However, BG/Zr coatings had lower adhesion strength than the HA/Zr coatings, but showed higher corrosion resistance.