Enhanced wear resistance of NiTi alloy by surface modification with Nb ion implantation

Niobium ion implantation is found to significantly decrease the friction coefficient and improve wear resistance of NiTi shape memory alloy. Scanning electron microscope(SEM) observations indicate that surface grooves formed on NiTi during the mechanical polishing are removed after Nb ion implantation. Dry friction tests show that Nb implanted NiTi samples exhibit a lower friction coefficient, narrower wear tracks, fewer wear debris generated, 46 %–62 % reduction in wear width, and29 %–49 % reduction in wear depth compared with the untreated NiTi. Wear resistance is related to the incident parameters, and the Nb implanted NiTi with the incident dose of 2.5 9 1017ionsácm-2, and incident current of2 mA behaves the best wear performance. The lubricating of Nb2O5, good oxidation resistance of Nb in NiTi, and increased micro-hardness of NiTi are responsible for the enhanced wear resistance.     

In vitro corrosion behavior of TiN layer produced on orthopedic nickel-titanium shape memory alloy by nitrogen plasma immersion ion implantation using different frequencies

In the present work, the NiTi surface was modified by nitrogen plasma immersion ion implantation (PIII) in an effort to improve the corrosion resistance and mitigate nickel release from the materials. The implanted nitrogen depths and thicknesses of the surface TiN barrier layers were varied by changing the pulsing frequencies during PIII. In order to determine the optimal parameters including the pulsing frequencies, electrochemical tests including open circuit potential (OCP) measurements and potentiodynamic polarization tests were conducted on the untreated and N-implanted NiTi in simulated body fluids (SBF). Our results reveal that the nitride layer produced using a frequency of 50 Hz has the best stability under the OCP conditions and the TiN layer produced using 200 Hz has the highest potentiodynamic stability after immersion in SBF for a long time. The observation can be correlated to the temperature during PIII and the thickness of TiN layer. The TiN layer on the NiTi surface favors deposition of Ca-P composites thereby compensating for the instability of the TiN layer produced at a higher frequency.     

Surface characteristics, corrosion behavior, and antibacterial property of Ag-implanted NiTi alloy

NiTi shape memory alloy was modified by Ag ion implantation with different incident doses to improve its antibacterial property. The atomic force microscopy, auger electron spectroscopy, and X-ray photoelectron spectroscopy show that the surface of NiTi alloy is covered by TiO₂ nano-film with embedded pure Ag with a peak concentration of 5.0 at% at the incident dose of 1.5 × 10¹⁷ ions·cm^?2, and Ni concentration is reduced in the superficial surface layer. The surface roughness reaches the maximum value nearly twice higher than the control sample at the incident dose of 1.5 × 10¹⁷ ions·cm^?2. The potentiodynamic anodic polarization curves show that the Ag-implanted NiTi samples possess higher self-corrosion potential (E _corr) and lower self-corrosion current density (i _corr) but lower breakdown potential (E _br). Therefore, the corrosion resistance of the Ag–NiTi is comparable to, if not better than, the untreated NiTi. The antibacterial tests reveal that there is a distinct reduction of the germ numbers on the Ag–NiTi, which is due to the direct contact between Ag and germ, and enhanced by the leaching Ag ions.     

Nitrogen ion implantation and in vitro corrosion behavior of as-cast Ti-6Al-7Nb alloy

In the present investigation, surface modification of Ti-6Al-7Nb alloy with nitrogen ions is considered as a method to improve its performance with respect to corrosion. Nitrogen ion was implanted on Ti-6Al-7Nb alloy at an energy of 70 and 100 keV using a 150 keV accelerator at different doses between 1×10¹⁶ and 3×10¹⁷ ions/cm². Gracing incidence X-ray diffraction was employed on the implanted specimens to understand the phases formed with increasing doses. The implanted samples were subjected to electrochemical study in Ringer's solution in order to determine the optimum dose that can give good corrosion resistance in a simulated body fluid condition. The OCP of the implanted specimens were found to shift in the noble direction in comparison with unimplanted specimen. The passive current density and area of the repassivation loop were found to decrease as the dose values increased. The electrochemical impedance spectroscopic results indicate that the polarization resistance was higher for the dose of 2.5×10¹⁷ ions/cm² implanted at both energy of 70 and 100 keV. Nitrogen ion implantation enhanced the passivability and reduces the corrosion kinetics of the alloy surface with increasing tendency for repassivation. Nature of the surface and reason for the variation and improvement in corrosion resistance are discussed in detail.     

Surface characteristics and corrosion behavior of Ti-Al-Zr alloy implanted with Al and Nb

Ti-Al-Zr alloys were implanted with Al and Nb to doses ranging from 1 × 10¹⁷ to 1 × 10¹⁸ ions cm⁻². The valence states of element on the sample surfaces were analyzed by X-ray photoelectron spectroscopy (XPS). Glancing angle X-ray diffraction (GAXRD) was employed on the as-implanted specimens to understand phase formation. X-ray diffraction (XRD) measurement revealed α-Ti on Al-implanted samples and (α + β)-Ti on Nb-implanted samples. The tendency was observed in increasing corrosion resistance from α- toward (α + β)-phase. In deaerated 5 M HCl, the ion-implanted Ti-Al-Zr surface containing Nb-stabilized β-phase was spontaneously passive, while Al-implanted surface displaying an active/passive behavior. In the aerated solution with pH = 10, all the implanted surfaces are passive. Enhanced reoxidation was confirmed on implanted surfaces by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) analysis. The corrosion in the solution with pH = 10 was governed by a predominantly TiO₂ surface film. The cathodic kinetics was seen to affect the corrosion behavior in 5 M HCl.     

Electrochemical behaviour of oxidized NiTi shape memory alloys for biomedical applications

A new oxidation treatment (OT) for NiTi Shape Memory Alloys used in biomedical applications has been developed in a previous work to reduce Ni surface concentration and, consequently, decrease Ni ions release into the exterior medium. This OT treatment is expected to minimize adverse and toxic reactions associated to Ni ions. However, in order to assess the biocompatibility of a metallic material, its corrosion resistance has to be evaluated.In this work, the electrochemical behaviour of NiTi surfaces oxidized by the new OT treatment was compared to untreated NiTi surfaces (NT). For this purpose, tests of open-circuit potential and cyclic voltammetry were performed at 37 °C in a Hanks Balance Salt Solution.A significant increase of the corrosion (E_corr) and breakdown (E_b) potentials was observed for OT surfaces, in comparison with NT surfaces. Moreover, the qualitative potentiodynamic behaviour of OT NiTi and Ti surfaces are similar. This observation suggests that the OT treatment leads to the formation of an oxide on NiTi surface that has similar structure and electrochemical property to native Ti oxide. This new oxidation treatment is efficient to protect NiTi alloys from electrochemical degradation and, therefore, it may be an excellent candidate for biomedical applications.     

Surface treatment of NiTi shape memory alloy and its influence on corrosion behavior

Influence of various surface treatments of a NiTi alloy on its surface chemistry and corrosion resistance was studied. NiTi (50.9 at.% Ni) alloy was subjected to mechanical polishing (MP), chemical etching (CHE) in an acidic bath, combination of mechanical polishing and oxidation at 530 °C/10 min in air (MPO) and combination of chemical etching and oxidation at 530 °C/10 min in air (CHEO). Scanning electron microscopy, X-ray photoelectron spectroscopy and Raman spectrometry were used for the surface examination. Corrosion behavior was determined by measuring potentiodynamic curves and nickel release into a model physiological solution with pH = 2. It was shown that oxidation at 530 °C has a slightly retarding effect on the nickel release in the case of MP material. However, in the case of CHE material, oxidation negatively influences corrosion, i.e. it strongly accelerates the nickel release, despite that it produces a relatively thick Ni-depleted oxide layer. Chemical etching was evidenced to produce the best corrosion performance in terms of nickel release. By comparing the MP and MPO sample, it was evidenced that oxidation significantly enhances susceptibility to the pitting corrosion. The findings obtained in our work were discussed in relation to variations in the surface chemistry and structure after different treatments.     

Surface characterization of passive film formed on nitrogen ion implanted Ti-6Al-4V and Ti-6Al-7Nb alloys using SIMS

The aim of this paper is to study the effect of N⁺ ion implantation on corrosion and phase formation on the implanted surfaces of Ti-6Al-4V and Ti-6Al-7Nb alloys. Nitrogen ion was implanted on Ti-6Al-4V and Ti-6Al-7Nb alloys at an energy of 70 and 100 keV, respectively using a 150 keV accelerator at different doses ranging from 5 × 10¹⁵ to 2.5 × 10¹⁷ ions/cm². Electrochemical studies have been carried out in Ringer’s solution in order to determine the optimum dose that can give good corrosion resistance in a simulated body fluid condition. The implanted surfaces of such modified doses were electrochemically passivated at 1.0 V for an hour. Secondary ion mass spectroscopy was used to study and characterize titanium oxide and titanium nitride layers produced on implanted surface and to correlate them with the corrosion resistance. The nature of the passive film of the implanted-passivated specimen was compared with the unimplanted-passivated as well as as-implanted specimens.     

Surface Modification of PVD-TiN Films Using MEVVAIon Implantation

IN severe working and operating conditions tin filmsfabricated by conventional methods may also fail.Therefore,the investigations were towards furthersurface treatments,aiming at modifying the wearresistance of TiN films.Among the post surfacetreatment methods,MEVVA ion implantation hasshown to be particularly promising for surfacemodification|2l Some studies have shown that the wearand friction of implanted TiN films were improved afterMEVVA ion implantation,irrespective of the type ofi…     

Cr离子注入镍钛合金的表面组织结构

针对镍钛合金(NiTi)进行3种不同浓度Cr离子注入,采用扫描电子显微镜、三维白光形貌干涉仪、小角度掠射X射线衍射仪、X射线光电子能谱仪分析了离子注入前后镍钛合金表面形貌、粗糙度、组织结构及化合态。结果表明,随着注入Cr离子浓度的增大,镍钛合金表面更加平整,粗糙度变小。所有注入试样表面形成了近60nm厚的注入膜层,主要成分为三氧化二铬和铬碳化合物,并且随Cr离子注入剂量的增加,三氧化二铬和铬碳化合物的含量增加。     

3Cr2W8V钢的钽、碳离子束材料改性

采用由金属蒸汽真空弧离子源引出的强束流钽、碳离子对 3Cr2W8V钢进行离子注入表面改性研究。钽注入剂量为 3× 10 1 7cm- 2 ,引出电压为 42kV ,平均束流密度为 40 μA·cm- 2 。摩擦磨损试验结果表明 ,钽、碳离子双注入 3Cr2W8V钢能使其耐磨性提高 2 5倍 ,并可大幅度降低其摩擦系数。利用卢瑟福背散射谱 (RBS)测量了离子注入表面的成分 ,借助X射线衍射 (XRD)仪考察了表层的相结构。     

Electrochemical studies of stainless steel implanted with nitrogen and oxygen by plasma immersion ion implantation

Plasma Immersion Ion Implantation (PIII) of stainless steel with nitrogen at temperatures lower than 400 °C has been reported to increase the hardness of the material by several times. However, expectations that the corrosion resistance will remain unaffected after implantation were not found to be so. In the present study the influence of post-oxygen implantation on the corrosion resistance of nitrogen implanted stainless steel is presented. Stainless steel samples were subjected to oxygen, nitrogen and post-oxygen ion implantation at different temperatures. GIXRD and microRaman studies of the implanted samples showed that oxygen implantation leads to the formation of an oxide layer consisting of corundum and spinel structures. The corrosion properties of the implanted samples were studied by potentiodynamic polarization and electrochemical impedance techniques in 3.5% NaCl solution. After nitrogen implantation the corrosion current increased and the corrosion potential shifted to the less noble side to − 0.486 V as compared to − 0.284 V for the substrate. Oxygen implantation at 400 °C shifted the corrosion potential to the nobler side to − 0.2 V with decrease of corrosion current. For post-oxygen ion implantation at temperatures lower than 400 °C, the corrosion current was higher than the substrate and the corrosion potential was also on the less noble side. However, post-oxygen ion implantation at 400 °C after nitrogen ion implantation resulted in improved corrosion resistance as the corrosion potential shifted to nobler side and the corrosion current was lower than that of substrate.     

Corrosion behavior of AISI302 steel treated by elevated temperature nitrogen plasma immersion ion implantation

The corrosion behavior of AISI302 steel implanted with nitrogen at elevated temperature was investigated by electrochemical impedance spectroscopy. Equivalent circuits for explaining the impedance characteristics are proposed. The thick passive layer containing Cr₂O₃ and the expanded austenite layer in the sub-surface worked together, resulting in the high corrosion resistance.     

铝离子注入不锈钢表面提高Al-Si钎料浸润分析

为了实现铝合金和不锈钢的钎焊连接,对不锈钢进行铝离子注入前处理.注入电压为40 kV,注入剂量分别为3×1017,6×1017,9×1017离子数/cm^2.分析了注铝不锈钢表面化学状态,评价了BAl88Si钎料在注铝不锈钢及未注铝不锈钢表面的润湿铺展能力.结果表明,注铝不锈钢表面为Al和Fe元素共存;温度为600,6...     

Sol–gel derived Ta-containing TiO_2 films on surface roughened NiTi alloy

The surface of NiTi alloy was roughened by NaOH–HCl treatment, and the Ta-containing TiO2 films were coated on the pretreated NiTi alloy by the sol–gel method. Thermal analyses indicate that the evaporation temperature of the organics decreases with the addition of tantalum ethoxide in the TiO2 sol, but the crystallization temperature of anatase increases. The NaOH–HCl pretreatment improves the film integrity, but cracks still form in the films at high Ta contents(C20 %, molar ratio) owing to the increasing film thickness. X-ray diffraction(XRD) confirms that the addition of Ta suppresses the crystallization of anatase. X-ray photoelectron spectroscopy(XPS) reveals that Ta exists as Ta2 O5 in the film. With the increase of Ta content, the hydrophilic conversion of the films under UV illumination is impeded, but their corrosion resistance in 0.9 % NaCl solution increases, tested by the potentiodynamic polarization. The coating samples have acceptable hemolysis ratios for biomaterials(5). The introduction of Ta improves the anti-aggregating function of the TiO2 film in the platelet adhesion test.     

镁合金表面离子注Ti耐蚀性能的研究

镁合金以其优越的性能在工业上的应用越来越广泛,但是其耐蚀性、耐磨性较差,硬度较低的缺点限制了它的大量使用.利用改进的金属蒸发弧放电离子源(MEVVA)在AZ31镁合金表面注入Ti离子,形成Ti离子注入改性层,以期提高镁合金表面的耐蚀性能.注入能量为45keV,注入剂量为3×1017 cm-2.注入后镁合金表面形成厚度约为450nm的注入层,用SEM、XRD分析了Ti离子注入层的表面形貌和相结构.用CS300P型电化学工作站测试了注入前后镁合金的耐蚀性,结果表明镁合金表面耐蚀性能显著提高.     

基于载能离子束技术制备超薄无胶挠性覆铜板

目的 开发超薄的无胶二层挠性覆铜板(2L-FCCL)。方法 融合MEVVA离子注入、磁过滤阴极真空弧和化学电镀技术在柔性聚酰亚胺表面构筑梯度金属化结构,并为超薄无胶二层挠性覆铜板的制备提供解决方案。结果 通过XPS、ATR-FTIR光谱及反应分子动力学(ReaxFF-MD)模拟证明了Ni⁺注入过程中聚酰亚胺亚表层互键连网络的形成,这种离子螯合反应带来的机械互锁效应能够极大提高界面附着强度。此外,磁过滤阴极真空弧技术制备的γ (Ni-Cr)合金过渡层具有良好的柔韧性和延展性,有助于Cu膜的后续生长,并增强协同变形能力。通过45°剥离试验测得NiCr合金层与聚酰亚胺基底之间的附着强度为(1.75±0.16)N/mm,而精细化挠性覆铜线路经历1 000次弯折试验后在其高变形区域未观察到裂纹萌生或线路剥落现象。结论 通过MEVVA离子注入与磁过滤阴极真空弧技术的耦合可以显著提升挠性覆铜板的机械稳定性,有望应用于高端挠性覆铜板的工业化制备。     

Modification of biomedical NiTi shape memory alloy by TiC/Ti films using PIIID

TiC/Ti coatings were deposited on the surface of Ti-50.6 at.% Ni alloy by plasma immersion ion implantation and deposition (PIIID) technique. The microstructure, mechanical properties and hemocompatibility of the samples were investigated by means of XRD, AFM, nanoindentation, and scratch and platelet adhesion tests. The result of XRD analysis shows that the crystalline TiC coating has a preferential orientation of (111) in the normal direction. The surface presents a very smooth and dense microstructure with 1.517 nm root mean square roughness (RMS). The average hardness and modulus values of the TiC coating are much higher than those of the NiTi substrate. In the initial stage of scratching, some obvious transversal cracks and worm-like cracks spreading into the film from both side of the scratch track were observed. At higher normal loads for the scratching test, the film delaminated from the substrate at the margins of the substrate. Platelet adhesion tests demonstrate that the hemocompatibility of the coated sample is improved.     

Microstructure and corrosion resistance of tantalum after nitrogen ion implantation

This paper investigates the effect of nitrogen ion implantation on surface structure as well as resistance against tantalum corrosion. Bulk Ta surface was implanted with 30?keV nitrogen ions at a temperature of 100°C with doses between 1?×?10¹⁷ and 1?×?10¹⁸?ions/cm². The implanted samples were characterised by atomic force microscopy, X-ray diffraction analyses and the corrosion test to identify structural, compositional and electrochemical changes at various doses. The experimental results indicate the formation of hexagonal tantalum nitride (TaN_0.43), in addition to the fact that by increasing the ion dose, nitrogen atoms occupy more interstitial spaces in the target crystal, a case which can significantly improve corrosion resistance. The maximum extent in the improvement of the micro hardness was 75% and the reduction in the corrosion current was 83%. According to scanning electronic microscopy and corrosion results, in the dose of 1?×?10¹⁸?ions/cm² the highest corrosion resistance was received against the H₂SO₄ corroding media.