Adhesion of sol-gel derived hydroxyapatite nanocoatings on anodised pure titanium and titanium (Ti6Al4V) alloy substrates

The mechanical properties and adhesion behaviour of sol-gel derived hydroxyapatite (HA) nanocoatings on commercially pure (cp) titanium (Ti) and Ti6Al4V alloy have been determined and related to anodising treatment. The surface roughness, wetting and coating characteristics were examined using profilometry, contact angle, scanning electron microscopy (SEM) and X-ray diffraction (XRD). Nano-indentation was used to determine the Young's modulus and hardness of the coatings, while microtensile tests were used to introduce controlled strains in the coatings through the cp Ti and TiAl6V4 alloy substrates, from which the strength, fracture toughness and adhesion behaviour could be ascertained based on multiple cracking and delamination events. The toughness of the HA coatings is found to be slightly lower to that of equivalent bulk pure HA ceramics. The substrate and the anodized layer thickness have the most influence on the interfacial adhesion of HA, with nanocoatings on Ti6Al4V exhibiting superior interfacial bonding in comparison to cp Ti.     

Ti-6Al-4V基体上等离子喷涂羟基磷灰石涂层的热-力耦合和残余应力

基于热弹塑性理论建立了等离子喷涂羟基磷灰石涂层的热-力耦合模型。一方面,通过引入变形对温度的影响项对经典的Fourier瞬态热传导方程进行了修正,另一方面,在考虑了温度软化效应、应变硬化效应、和应变率强化效应后,采用适用于高温、高应变率条件下的Johnson-Cook模型作为本构方程。基于上述耦合模型,采用有限元方法对涂层内的残余应力场进行了模拟,同时还模拟了基体预热温度以及涂层厚度对残余应力的影响。为了验证数值模拟的可靠性,还采用“材料去除”的实验技术测试了涂层在界面处的残余应力。结果表明：在界面边缘有明显的应力集中;适当提高基体的预热温度有利于减小残余应力;涂层的残余应力随厚度的增加而增大。     

Preparation and characterization of hydroxyapatite/titania composite coating on NiTi alloy by electrochemical deposition

NiTi alloy is used as biomaterial due to its unique properties, but the high content of Ni (about 50 at.%) in biomedical NiTi is of concern. Hydroxyapatite/titania composite coating was directly electrodeposited on the surface of NiTi alloy. The coated samples were characterized using X-ray diffraction, scanning electron microscopy, infrared spectroscopy, bonding strength test, polarization and electrochemical impedance spectroscopy (EIS). Results showed that addition of TiO₂ to the electrolyte changed the morphology of hydroxyapatite from thin flake-flower-like crystals to needle-flower-like crystals, and the coating was much denser. Besides, hydroxyapatite crystal grains in the coating were preferentially arranged in the [001] direction, which was perpendicular to the surface of NiTi alloy. The addition of TiO₂ improved the bonding strength between the coating and the substrate. Corrosion resistance of NiTi in the simulated body fluid at 37 °C was significantly improved by more than 50 times by electrodeposition of the hydroxyapatite/titania composite coating.     

Preparation and cell-materials interactions of plasma sprayed strontium-containing hydroxyapatite coating

The use of strontium-containing hydroxyapatite (Sr-HA) as a biomaterial has been reported recently. In vitro and in vivo studies have shown that Sr-HA promotes osteoblast response and stimulates new bone formation. In order to extend its usage to major load-bearing applications, such as artificial hip replacement, it has been proposed that the material could be used in the form of a coating on implant surfaces. This paper reports a preliminary study of biocompatibility of plasma sprayed Sr-HA coatings on a metallic substrate. Coatings of Sr-HA containing 10 mol% Sr²⁺ was produced on titanium alloy substrates. The coating exhibited good bonding with the substrate. The bioactivity of Sr-HA coating was evaluated in vitro by immersion in simulated body fluid (SBF). After immersion in SBF, Sr-HA coating exhibited great ability to induce apatite precipitation on its surface. The possible effects of cell-materials interactions of Sr-HA coating were examined by culturing osteoprecursor cells (OPC1) on coating surfaces. The effect of Sr-HA was also compared to a hydroxyapatite (HA) coating, which is widely used in orthopedics and dentistry. The results indicated that Sr-HA coating had good biocompatibility with human osteoblasts. OPC1 cells survived and proliferated well on the surface of coating. Sr-HA coating promoted OPC1 cells attachment, and more local contacts were produced on the surface. The presence of Sr stimulated OPC1 cell differentiation and ALP expression. No deleterious effect on ECM formation and mineralization was found with Sr-HA coating. The results indicated that Sr-HA coating had good mechanical properties and bioactivity in vitro.     

医用镁合金等离子喷涂羟基磷灰石涂层研究

为了提高医用镁合金的表面耐蚀性和生物相容性,采用等离子喷涂技术在镁合金表面制备羟基磷灰石(HA)涂层.研究结果表明,镁合金表面所制备的HA涂层与基体结合牢固,界面无裂纹、气孔等缺陷.相组成为生物相容性较好的HA和少量的Ca3(PO4)2(TCP),显微组织具有层状特征,涂层表面存在一些有利于骨长人的孔隙.涂层的弹性模量约为19.825 GPa,接近骨的弹性模量,涂层表面硬度为300～350 HV.腐蚀试验和钙磷沉积试验结果表明HA涂层具有较好的耐蚀性和骨诱导性.     

Fretting wear of micro-arc oxidation coating prepared on Ti6Al4V alloy

Micro-arc oxidation(MAO)coating was prepared on Ti6Al4V alloy surface and its characterizations were detected by Vickers hardness tester,profilometer,scanning electric microscope(SEM),energy dispersive X-ray spectrometer(EDX)and X-ray diffractometer(XRD).Fretting wear behaviors of the coating and its substrate were comparatively tested without lubrication under varied displacement amplitudes(D)in a range of 3-40μm,constant normal load(Fn)of 300 N and frequency of 5 Hz.The results showed that the MAO coating,presenting rough and porous surface and high hardness,mainly consisted of rutile and anatase TiO2 phases.Compared with the substrate,the MAO coating could shift the mixed fretting regime(MFR)and slip regime(SR)to a direction of smaller displacement amplitude.In the partial slip regime(PSR),lower friction coefficients and slight damage appeared due to the coordination of elastic deformation of contact zones.In the MFR,the friction coefficient of the coating was lower than that of the substrate as a result of the prevention of plastic deformation by the hard ceramic surface.With the increase of the displacement amplitude,the degradation of the MAO coating and the substrate increased extremely.The fretting wear mechanisms of the coating were abrasive wear and delamination with some material transfer of specimen.In addition,the coating presented a better property for alleviating fretting wear.     

Ti6Al4V合金表面激光熔覆钛基复合涂层的显微组织研究

在Ti6Al4V合金表面预置Ti和Cr3C2混合粉末,采用横流CO2激光进行熔覆试验,制备出了原位自生的TiC颗粒增强的钛基复合涂层.利用SEM、XRD等手段对激光熔覆层的组织、成分、物相进行了分析,测试了激光熔覆层的显微硬度.结果表明,熔覆层不同位置,组织形态不同,TiC在熔覆层表层以树枝晶形态存在,而在熔覆层底部为近球状颗粒.熔覆层与基材之间形成良好的冶金结合.熔覆层显微硬度在600～800 HV0.5之间,约为基材硬度的2～3倍.     

水热处理参数对Ti6Al4V合金微弧氧化膜HA生成的影响

采用微弧氧化的方法在Ti6Al4V合金表面生成一层富含Ca和P元素的氧化膜,对其进行水热处理,并生成具有生物活性的羟基磷灰石(HA)涂层.研究了处理介质为氨水(pH=10)时,水热处理温度、水热处理时间、冷却条件及填充度对水热处理后钛合金微弧氧化膜表面生成羟基磷灰石的影响.结果表明:随着处理温度和保温时间的延长,HA数量增多,颗粒增大;随釜冷却处理比空冷处理得到的HA更加粗大,并且分布更加均匀致密;填充度增加,HA分布趋于均匀但是形状趋向不规则.     

模拟体液中纯钛及Ti6A14V合金的腐蚀行为

采用电化学测试技术研究了人体医用金属材料工业纯钛和Ti6A14V合金在人工模拟体液中的腐蚀行为,结果表明,阳极极化后两种合金均未发现点蚀,工业纯钛的维钝电流密度小于于Ti6A14V合金,前者的阳极极化性能优于后者,Ti6A14V合金缝隙试样在阳极电位超过＋2000mV(vsSCE)后,电流开始急剧增大,发生了缝隙腐蚀;通过电子探针分析发现,在缝隙内Al和V两种元素发生活性溶解。工业纯钛在电位达到＋4000mV/(vsSCE）时仍没有发生缝隙腐蚀。     

Ti6Al4V合金表面离子注入N+C,Ti+N和Ti+C性能研究

采用等离子体基离子注入的方法在Ti6Al4V合金表面分别注入N+C、Ti+N和Ti+C元素,注入剂量均为2×1017 ions/cm2,N+C和Ti+N元素的注入负脉冲偏压为-50 kV,Ti+C元素的注入电压分别为-20 kV、-35 kV和-50 kV。通过X射线光电子能谱仪（XPS）和X射线衍射仪（XRD）对注入层进行了微观结构分析,结果表明：Ti+C注入层中存在TiC和Ti-O,Ti+N注入层中存在TiN和Ti-O键。采用纳米压痕仪和球盘磨损试验机对注入层的硬度和摩擦学性能进行了研究。结果表明：在相同注入电压下,Ti+C注入层的硬度最高,其次是Ti+N注入层,N+C注入层的硬度最低;Ti+C 注入层的硬度随着注入电压的增大而增大,最大硬度为11.2GPa。50kV注入层Ti+C具有最低的比磨损率,其值为6.7×10-5mm3/N.m,比磨损率较未处理Ti6Al4V基体下降了1 个数量级以上,表现出优异的耐磨损性能。     

Effect of Fe content on microstructures and properties of Ti6Al4V alloy with combinatorial approach

A combinatorial approach was applied to investigating the influence of Fe content on the microstructures and properties of Ti6Al4V alloy. A diffusion couple was manufactured with Ti6Al4V and Ti6Al4V20Fe alloys and annealed at 1000 °C for 600 h to obtain a wide range of compositions. By combining electron probe micro-analysis (EPMA), scanning electron microscopy (SEM) and nanoindentation, the relationships between composition and microstructure as well as hardness were determined. It is found that after aging the Ti6Al4V5Fe sample contains reasonable (about 55%) volume fraction of fine α phase and shows the peak hardness among the Ti6Al4VxFe alloys. Therefore, it is a promising candidate for the development of titanium alloys. HAADF-STEM and XRD reveal that after quenching from the single β phase field, the metastable α″ lamellae form in the Ti6Al4V5Fe alloy, and on subsequent isothermal aging, the α″ lamellae become coarse and act as precursors/preferential nucleation sites for the stable α phase.     

Ti6Al4V合金激光熔覆Ni基自润滑涂层的组织和性能

利用光纤激光器在Ti6Al4V合金基体表面制备了Ni25为基体和Ni包MoS2为润滑剂的Ni基自润滑涂层,通过FESEM、XRD、硬度测试仪和摩擦磨损试验机研究了熔覆层的显微组织、物相组成和摩擦性能.结果表明,熔覆层表面主要以花瓣状组织以及少量的树枝晶组成,界面处的组织主要是以树枝晶为主,还有少量的等轴晶粒.熔覆层...     

Electrochemical behavior of the Ti6Al4V alloy implanted by nitrogen PIII

Plasma surface treatments have been used very often to enhance the surface properties of metallic materials. In this work, Ti6Al4V titanium alloy was treated by nitrogen plasma immersion ion implantation (NPIII) in order to obtain improvements in its surface properties, such as corrosion resistance evaluated here. The microstructure and corrosion behavior of the implanted and unimplanted samples were evaluated, using, XRD, GDOES and potentiodynamic polarization and impedance electrochemical spectroscopy tests in 0.6 M NaCl solution. It was verified that the NPIII created resistant layers to corrosive attacks. In corrosion tests by polarization, the implanted samples showed corrosion current density reduction of about 10 times compared to the Ti6Al4V alloy without treatment. Besides that, it was also observed a reduction of the passive current density of one order of the magnitude. In all the studied cases, the polarization curves were shifted to more positive values of potentials, indicating a lower tendency of these PIII treated surfaces to corrosion. The implantation process produced a thin TiN surface layer followed by Ti₂N and then a layer with nitrogen in solid solution, all detected by GDOES combined with X-ray diffraction. These layers promoted an excellent polarization resistance of the Ti6Al4V surfaces on impedance spectroscopy tests also. This better performance in these tests can be correlated with the formation of continuous nitride layer, which could retard chloride ions ingress into the substrate.     

Ti6Al4V合金吸氢行为研究

研究了Ti6Al4V合金在不同置氢温度、保温时间和氢压下的吸氢行为,利用光学显微镜研究了氢在钛合金中的分布规律。研究结果表明,Ti6Al4V合金的氢含量是由置氢温度、保温时间和氢压来控制的。随着置氢温度的升高,氢含量先增加后降低。随着氢压的增加,氢含量直线增加。钛合金的吸氢过程实质上是氢的扩散过程,随着保温时间的增加,合金中的氢分布逐渐趋于一致。     

The effect of a DLC coating adhesion layer on the corrosion behavior of titanium and the Ti6Al4V alloy for dental implants

The properties of DLC layers provide for their broad use in medical applications. Their tribological properties are frequently utilized in big joint implants, and their barrier effect offers another benefit. The present work studied corrosion behavior of DLC coatings formed on titanium and Ti6Al4V alloy with a titanium or chromium inter-layer, in environments to which dental implants may be exposed. Electrochemical impedance spectroscopy, XPS surface analysis, ICP/MS chemical analysis method and a set of standard biological tests were employed in the study.     

Electrochemical deposition of bioactive coatings on Ti and Ti-6Al-4V surfaces

Passivating coatings of brushite (CaHPO₄·2H₂O) were obtained on Ti and Ti-6Al-4V ELI alloy substrates by cathodic polarization. After soaking in Ringer's solution for 48 h brushite was transformed to hydroxyapatite (Ca₁₀(PO₄)₆(OH)₂) as confirmed by XRD, FT-IR and Raman spectroscopy. Electrochemical cyclic polarization curves of the coated biomaterials obtained in Ringer's solution at pH values of 7.1 and 8.91 as well as in Hank's Balanced Salt Solution (HBSS) at pH value of 7.4 show a nobler behavior than of the uncoated biomaterials. The coated biomaterials had lower corrosion rates than the uncoated biomaterials suggesting a protective character of the hydroxyapatite coating. Electrochemical impedance spectra (EIS) revealed capacitive behavior, owing to the protective, very resistant layer, the thickness of which increased with soaking time. The coated biomaterials presented higher electropositive open circuit potentials compared to the uncoated biomaterials as result of the protective effect of the coating. The morphology of the coatings changed with soaking time as the coatings became denser, smoother and better adhering. Hence such coatings may provide favorable structure for cell adhesion and proliferation.     

Morphology and phase composition of MAO ceramic coating containing Cu on Ti6Al4V alloy

A ceramic coating containing Cu element was prepared on Ti6Al4V alloy using micro-arc oxidation(MAO)technology.After copper ions were added to the electrolyte solution of aluminate salt,the anode voltage in MAO process reduces,and the micropore size on the surface of the ceramic coating is more uniform.The crystalline phases of the ceramic coatings prepared in the electrolyte solutions with and without copper ions are mainly Ti element,rutile TiO_2,and anatase TiO_2.The addition of copper ions to the electrolyte solution makes rutile TiO_2 content decrease but promotes the formation of Al_2TiO_5 phase.Energy spectrum test results confirm that by adding copper ions to the electrolyte solution,the ceramic coating formed in the process of MAO contains copper element.     

Ti6Al4V辉光等离子渗铝摩擦磨损性能研究

利用双层辉光等离子渗金属技术在Ti6Al4V上渗铝以提高材料的摩擦磨损性能,对渗铝层的相结构和显微硬度进行了测试.采用球盘滑动磨损试验机对渗层进行摩擦磨损性能测试.结果表明:渗铝后渗层由Al3Ti和Al组成,材料的硬度值较基体Ti6Al4V有了很大的提高;材料摩擦因数和磨损体积减小,耐磨性得到提高.通过磨痕形貌分析可知,渗层磨损机制为粘着磨损.可见采用辉光等离子渗铝技术改善了材料的摩擦磨损性能.     

Ti6Al4V钛合金表面真空渗氧处理

目的在Ti6Al4V钛合金表层制备硬度高、耐磨性好的硬化层。方法结合真空技术,以高纯的O2为介质,在Ti6Al4V钛合金表面制备致密的渗氧硬化层,采用X衍射仪分析渗氧层的相组成,用金相显微镜观察渗氧层和磨痕组织,用显微硬度计测试渗氧层的显微硬度,用MM-U10A端面磨损试验机研究渗氧层的耐磨性。结果渗氧层物相主要由TiO_2、TiO、Ti_3Al及Al_2O_3组成,温度较低时,形成的渗氧层较薄,温度增加,渗氧层厚度迅速增加,硬度及耐磨性也随之增加。温度为760℃时,表面硬度为基体硬度的2.5倍以上,大于750HV,有效硬化层厚度达60μm以上,其磨损失重仅为未渗氧原样的1/4,表面磨痕细密,没有撕裂情况发生,渗氧层保持完整。温度继续增加,氧化物开始聚集长大,渗氧层组织开始变得疏松,硬度及耐磨性开始下降。结论 Ti6Al4V钛合金表面真空渗氧处理可显著提高其表面硬度,耐磨性改善明显。