NiTi合金表面改性及其微动磨损性能研究

采用多弧离子镀技术在NiTi形状记忆合金表面制备TiN涂层。利用SRVⅢ摩擦磨损试验机研究NiTi合金表面改性后在37℃Hank’s模拟体液中微动磨损性能,分析法向载荷对TiN合金磨损机制的影响规律。利用SEM扫描电镜及能谱考察磨损表面形貌,结果表明：制备的TiN涂层表面致密均匀,无明显缺陷。说明TiN涂层可有效提高基体的耐磨性能,其磨损机制主要表现为剥落损伤与磨粒磨损并存。TiN涂层显微硬度为784 HV,远高于基体,TiN/NiTi膜基硬度比缓慢下降,涂层与基体结合强度高。     

含h-BN 的钛合金激光熔覆自润滑耐磨涂层的摩擦学行为

为提高Ti6Al4V合金的摩擦学性能,采用激光熔覆技术在钛合金表面制备以TiC、TiB2、CrB等为增强相、γ-Ni基固溶体为增韧相、h-BN为固体润滑相的自润滑耐磨复合涂层;分别在不同载荷下测试复合涂层和Ti6Al4V合金基体的干滑动磨损性能。结果表明,该复合涂层的摩擦因数及磨损率随着载荷的增大呈现先减小后略增大的趋势,并且摩擦因数和磨损率均比Ti6Al4V合金基体显著降低;在中等载荷下,复合涂层中的润滑颗粒被挤出磨损表面形成润滑膜,因而具有较好的自润滑耐磨性能,磨损后表面光滑平整。     

Ti6Al4V钛合金冲蚀机理研究

为研究Ti6Al4V钛合金在气固两相流使用环境中的损伤机理,进行了室内力学性能试验以及不同攻角下的冲蚀试验,并借助扫描电子显微镜对试验后试样表面的显微形貌进行分析。试验结果表明:较低角度30°时,"显微切削"和"挤压锻打"作用对Ti6Al4V钛合金试样表面会造成较为严重的损伤。     

真空阴极电弧沉积（Ti,Al）N薄膜的应用研究

为了提高TiN涂层刀具的耐磨性,采用钛铝合金靶,以真空阴极电弧沉积法制备了（Ti,Al)N涂层,对膜层形貌成分,组织结构及硬度进行了测试及研究,并试验了（Ti,Al)N涂层高速钢钻头及YG6硬质合金刀具的使用寿命,结果表明：（Ti,Al)N涂层硬度高达HV0．1,15,3700,（Ti,Al)N涂层使高速钢钻头及YG6硬质合金刀具的使用寿命显著提高。     

渗氢温度为800℃时氢对Ti6Al4V合金切削加工性影响的试验研究

试验试件的渗氢温度为800℃。通过对不同氢含量Ti6Al4V合金试件进行车削试验,测量切削力和加工后的表面粗糙度以及观察切屑形态,研究氢对Ti6Al4V合金切削加工性的影响。试验结果表明:随氢含量增加,Ti6Al4V合金的切削加工性提高,并且有一个最佳氢含量范围,超过该氢含量范围,随氢含量增加,Ti6Al4V合金切削加工性变差。     

钛合金表面的热氧化/真空扩散处理工艺

采用热氧化后真空扩散处理工艺。在Ti6A14V合金表面制备了与基体结合良好的硬化层，并在空气和真空条件下分别进行了摩擦磨损试验。结果表明，硬化层由表面氧化物薄层和氧扩散区组成，经810℃真空扩散后，在表面硬化层有Ti3Al相形成，使沿层深方向的硬度下降趋势变缓。热氧化/真空扩散处理可有效地降低在空气和真空中的Ti6A14V合金与GCr15钢的干摩擦系数。提高Ti6A14V合金在空气和真空中的耐磨性。     

钛合金微弧氧化层的摩擦学性能研究

利用微弧氧化技术在Ti6Al4V合金表面制备了富含钙、磷的多孔氧化陶瓷层,研究了微弧氧化层表面形貌、组成及摩擦学性能。研究结果表明,随着电压的升高,氧化层表面微孔孔径、粗糙度和Ca、P元素含量增大,显微硬度增大。25%小牛血清润滑条件下的微弧氧化层与ZrO2陶瓷球的摩擦学实验表明,微弧氧化层的摩擦因数高于Ti6Al4V钛合金,但磨损率明显降低,表明微弧氧化Ti6Al4V合金具有良好的耐磨性能。     

表面改性钛合金与增强型聚四氟乙烯在海水中的摩擦学行为

为改善海水环境中钛合金与增强型聚四氟乙烯摩擦副对磨时的摩擦学性能,采用离子渗氮、微弧氧化技术对Ti6Al4V钛合金表面进行改性处理。对比研究了Ti6Al4V合金基材与改性层在模拟海水环境中分别与两种增强型聚四氟乙烯配副材料对磨的摩擦学行为。结果表明:在海水介质环境中,Ti6Al4V钛合金及其表面渗氮、微弧氧化处理试样与两种增强型聚四氟乙烯配副对磨时摩擦系数均较低;Ti6Al4V钛合金基体不耐磨,且造成两种增强型聚四氟乙烯配副的严重磨损。上述两种表面处理均有效改善了钛合金表面的耐磨性能,其中表面离子渗氮处理钛合金耐磨性能更优,同时降低了增强型聚四氟乙烯配副的磨损程度,而微弧氧化处理则使增强型聚四氟乙烯配副的磨损加重。相同试验条件下,玻璃纤维增强聚四氟乙烯比锡青铜增强聚四氟乙烯的耐磨性能优。采用离子渗氮钛合金与玻璃纤维增强聚四氟乙烯组成配副材料应用于海水环境中服役的水压传动摩擦学元件有明显的优势。     

Ti6Al4V钛合金表面双层辉光等离子钨-钼共渗层的制备及其高温摩擦磨损性能

采用双层辉光等离子表面技术在Ti6Al4V钛合金表面进行钨-钼共渗,并对渗层的结构和高温摩擦磨损性能进行了研究。结果表明:在Ti6Al4V合金表面形成了与基体结合良好的钨-钼共渗层;渗层由沉积层、过渡层和扩散层构成,渗层组织为钨、钼及其在钛合金中的固溶体TixW1-x、MoTi;与基体相比,在450℃条件下共渗层的摩擦因数稍有降低,而耐磨性却显著提高,且磨损后渗层表面磨痕显著减小,粘着和擦伤现象均得到明显减轻,其磨损机制主要是粘着磨损和少量的微切削。     

激光气体氮化原位合成制备TiN/Ti_3Al复合涂层及其抗高温冲蚀性能

通过在氮气中加入铝粉,采用激光气体氮化技术在Ti-6Al-4V钛合金表面原位制备了TiN/Ti_3Al复合涂层,研究了涂层的微观形貌、物相组成、硬度分布以及抗含SiC和SiO_2颗粒的高温高速水蒸气冲蚀的能力。结果表明:涂层的表面硬度为(1 400±50)HV,是Ti-6Al-4V钛合金的4倍;用SiC颗粒冲蚀较短时间或用SiO_2颗粒冲蚀后,涂层的冲蚀质量损失随冲蚀角度的增大而增加,Ti-6Al-4V钛合金的则减小;在相同冲蚀角度下,涂层的冲蚀质量损失随冲蚀颗粒硬度的增加而增大,Ti-6Al-4V合金的冲蚀质量损失在较小冲蚀角度时也遵循此规律,但在较大冲蚀角度下,质量损失的变化不大。     

Fretting wear behavior of nitrogen ion implanted titanium alloys in bovine serum lubrication

Nitrogen ion implantation was performed on biomedical titanium alloys by using of the PBII technology to improve the surface mechanical properties for the application of artificial joints. The titanium nitride phase was characterized with X-ray photoelectron spectroscopy (XPS). The nanohardness of the titanium alloys and implanted samples were measured by using of in-situ nano-mechanical testing system (TriboIndenter). Then, the fretting wear of nitrogen ion implanted titanium alloys was done on the universal multifunctional tester (UMT) with ball-on-flat fretting style in bovine serum lubrication. The fretting wear mechanism was investigated with scanning electron microscopy (SEM) and 3D surface profiler. The XPS analysis results indicate that nitrogen diffuses into the titanium alloy and forms a hard TiN layer on the Ti6Al4V alloys. The nanohardness increases from 6.40 to 7.7 GPa at the normal load of 2 mN, which reveals that nitrogen ion implantation is an effective way to enhance the surface hardness of Ti6Al4V. The coefficients of friction for Ti6Al4V alloy in bovine serum are obviously lower than that in dry friction, but the coefficients of friction for nitrogen ion implanted Ti6Al4V alloy in bovine serum are higher than that in dry friction. Fatigue wear controls the fretting failure mechanism of nitrogen ion implanted Ti6Al4V alloy fretting in bovine serum. The testing results in this paper prove that nitrogen ion implantation can effectively increase the fretting wear resistance for Ti6Al4V alloy in dry friction, and has a considerable improvement for Ti6Al4V alloy in bovine serum lubrication.     

Effect of laser power on the microstructure and mechanical properties of TiN/Ti3Al composite coatings on Ti6Al4V

Laser nitriding is one of the effective techniques to improve the surface properties of titanium alloys and has potential application in the life extension of last-stage steam turbine blades. However, cracking of surface coating is a common problem due to heat concentration in laser nitriding process. Conventionally, the cracks can be avoided through heat treatment, which may have an important influence on the mechanical properties of coating. Crack-free TiN/Ti3Al IMC coatings on Ti6Al4V are prepared by plasma spraying and laser nitriding. The microstructures, phase constitutes and compositions of the coating are observed and analyzed with scanning electron microscopy(SEM), X-ray diffraction(XRD) and X-ray energy-dispersive spectroscopy(EDS). Microhardness, elastic modulus, fracture toughness of the coating are measured. The results show that the crackand pore-free IMC coatings can be made through the proposed method; with increasing laser power, the amount and density of TiN phase in the coating first increased and then decreased, leading to the similar trend of microhardness and elastic modulus and the reverse trend of fracture toughness of the coating. Both the average microhardness and elastic modulus of the coating increase three times higher than those of the substrate. The volume fraction of the TiN reinforced phase in composite can be controlled by varying the laser power and the cracking problem in laser nitriding process is successfully solved.     

Triboelectrochemical behaviour of a Si3N4–TiN ceramic composite and a titanium alloy commonly used in biomedical applications

In this paper the corrosion and tribocorrosion behaviour of a traditional metallic biomaterial (Ti6Al4V) and a Si₃N₄/TiN (SN/TiN) ceramic composite are studied and compared during exposures to 1% NaCl and 1% NaCl + 1% lactic acid solutions.Electrochemical impedance spectroscopy (EIS) data collected on Ti6Al4V in both neutral and acidic solution have been interpreted on the basis of a double layer surface oxide film, which is completely removed from the wear track during the sliding tests. Under these conditions, the impedance of the depassivated region dominates the overall electrode impedance.Previous EIS tests performed on SN/TiN evidence that even this material exposed to neutral solution is covered by a double layer film, while a porous monolayer film forms in acid solution. Under pure corrosion conditions, SN/TiN exhibits corrosion rates which are quite comparable to those measured on Ti6Al4V. During tribocorrosion tests the EIS response of the ceramic material does not change much. Its corrosion rates are two orders of magnitude lower than those measured on Ti6Al4V.Profilometer analysis shows that on both materials most of overall tribocorrosion damage is due to mechanical wear.The tests suggest that SN/TiN is a promising biomaterials for applications where sliding conditions occur.     

Tribological properties of selected PVD coatings when slid against ductile materials

In this paper, a physical vapour deposited (PVD) deposited TiB₂ coating is compared in dry sliding with commercial PVD titanium nitride (TiN), titanium aluminium nitride (TiAlN) and titanium carbonitirde (TiCN) as to frictional properties and tendency of counter material pick-up. The aim is to investigate if the superior behaviour of the TiB₂ coating experienced in severe sliding applications against aluminium alloys can be extended to other materials with a similarly poor tribological characteristics.A new tribological test for sliding contact has been used. The test configuration involves two crossed elongated cylindrical test specimens which are forced to slide axially against each other at a constant sliding speed and a gradually increasing normal load, while recording the friction. The evaluation is performed by correlating the friction history with the width, topography and composition of the sliding tracks as detected by optical and scanning electron microscopy.Coated cemented carbide (CC) test cylinders have been slid against cylinders of a Ti alloy (Ti–6Al–4V), an Al alloy (Al 7075) and Inconel 718. It was shown that the TiB₂ surface displayed superior friction and anti-sticking properties, when tested against the aluminium alloy. Against the Ti and Inconel alloys no major difference between the coatings could be found. Instead, it is concluded that the friction coefficient is determined by the plastic properties of the counter material since a complete transfer layer instantly builds up on the coating.It proved possible to estimate the friction force from the width of the sliding tracks, the Vickers hardness of the counter material and simple plastic considerations. This estimation also verifies the unexpectedly low friction of all coatings against the Ti alloy.     

A study on the influence of laser power on microstructural evolution and tribological functionality of metallic coatings deposited on Ti-6Al-4V alloy

Metallic Ti–Co binary coatings were fabricated on titanium alloy (Ti–6Al–4V) substrate by laser surface cladding technique using a continuous wave RofinSinar 4 kW Nd: YAG laser. The influence of laser power on microstructure, hardness and tribological performance of Ti–Co laser clad coatings on titanium alloy (Ti–6Al–4V) was examined. Laser powers of 750 and 900 W were varied with constant scan speed of 1.2 m/min. A beam size of 3 mm and argon shield gas flow rate of 1.2 L/min were set as the operating laser parameters. Phase identification and morphological studies of the coatings were carried out using X-ray diffractometry (XRD) and scanning electron microscopy (SEM), respectively. Based on the results of laser process optimisation, it was observed that both laser powers produced clad coatings with good metallurgical bond with no cracks or pores in the coatings. With respect to the substrate (Ti–6Al–4V), the microstructure, hardness and friction/wear behaviour of Ti–Co coatings on Ti–6Al–4V substrate were enhanced obviously.     

Influence of the carbon content on the corrosion and tribocorrosion performance of Ti-DLC coatings for biomedical alloys

Biomedical alloys are prone to suffer corrosion and wear phenomena coming from the hostile environment of the body and friction processes, respectively. Diamond-like carbon (DLC) coatings are known to be excellent candidates for using as protective coatings on biomedical alloys, not only due to their excellent tribological properties but also due to their chemical composition and stability. In this work, three Ti-DLC PVD coatings with different compositions were deposited on Ti6Al4V alloy and their corrosion and tribocorrosion responses were evaluated in simulated body fluid. Excellent tribocorrosion response has been found especially in case of coatings with high carbon content. Additionally significative reduction of friction and wear has been obtained in comparison to the substrate response.     

Surface quality improvement of EDMed Ti–6Al–4V alloy using plasma etching and TiN coating

This paper seeks to improve the surface quality of electrical discharge machining (EDM) Ti–6Al–4V using plasma etching treatment and TiN coating. The EDM parameter setting is optimized firstly based on grey-Taguchi method. Four EDM parameters, including current (A), voltage (V), pulse duration (μs), and duty factor (%), are selected for multiple performance of lower electrode wear rate (EWR), higher material removal rate (MRR), and better surface roughness (SR). An orthogonal array, signal-to-noise (S/N) ratios, and analysis of variance (ANOVA) are used to analyze the effects of these EDM parameters. Normality tests show that all the distributions fit normality assumption with p?=?0.276, 0.688, and 0.663, respectively. The EDM process is stable over time monitored by Shewhart control charts. It is observed that there is an EDM damaged layer on the surface consisting of debris, microcracks, molten drops, and solidified metals by scanning electron microscopy. The plasma etching and TiN coating are employed to improve surface quality of the EDMed Ti–6Al–4V alloys. The results demonstrate that using the oxygen plasma etching treatment, the damaged phenomena are decreased, and the mean SR value is reduced from Ra?=?2.91 to Ra?=?2.50 μm. In addition, when the plasma-treated alloy is coated with Ti buffer/TiN coating by physical vapor deposition, the surface morphology exhibits less defects and a better surface finish. The mean SR values are further reduced from Ra?=?2.50 μm to Ra?=?1.48 μm (for 740 nm TiN film) and Ra?=?0.61 μm (for 1450 nm TiN film), respectively.     

Increasing the tribological performances of Ti–6Al–4V alloy by forming a thin nanoporous TiO2 layer and hydroxyapatite electrodeposition under lubricated conditions

In this study, comparative investigation of (i) untreated Ti–6Al–4V alloy, (ii) nanoporous thin TiO₂ layer formed by controlled anodic oxidation and (iii) electrodeposited hydroxyapatite coatings into porous oxide layer was carried out for evaluation of sliding-wear performances in a bio-simulated environment. Wear mechanisms, wear volumes and friction coefficients of the three types of surfaces under lubricated conditions in a bio-simulated solution were recorded and analyzed. The results presented herein show that, under the investigated tribocorrosion conditions (under reciprocating sliding), both surface treatments applied have improved the wear resistance and friction coefficients as compared to the untreated Ti–6Al–4V alloy surface.     

An experimental study of process variables in turning operations of Ti–6Al–4V and Cr–Co spherical prostheses

Ti–6Al–4V and Cr–Co alloys are extensively used in manufacturing prostheses due to their biocompatibility, high strength-to-weight ratio and high resistance to corrosion and wear. However, machining operations involving Ti–6Al–4V and Cr–Co alloys face a series of difficulties related to their low machinability which complicate the process of controlling the quality levels required in these parts. The main objective of this paper is to study the influence of cutting parameters, machine tool control accuracy and metrology procedures on surface roughness parameters and form errors in contouring operations of Ti–6Al–4V and Cr–Co workpieces. The machining performance of the two biocompatible materials is compared, focusing the study on part quality at low feed per revolution and the stochastic nature of plastic deformations at this regime. The results showed a better surface roughness control for Ti–6Al–4V, whereas for Cr–Co alloys, the performance presents high variability. In the case of form errors (sphericity), contouring errors and metrology procedures are important factors to be considered for quality assurance. In addition, the study analyses the correlation of the machining performance with different sensor signals acquired from a low cost non-intrusive multi-sensor, showing a high correlation of signals from acoustic emission sensors and accelerometers in the machining of spherical features on Ti–6Al–4V parts. The findings of this research work can be taken into account when designing prostheses components and planning their manufacturing processes.     

碳酸酯对Ti6Al4V/钢摩擦副摩擦磨损性能的影响

采用SRV型微动摩擦磨损实验机分别考察了Ti6Al4V-钢摩擦副在2种碳酸酯润滑下的摩擦磨损性能,并利用扫描电子显微镜和X射线光电子能谱仪分析了Ti6Al4V磨斑表面形貌和典型元素的化学状态。结果表明,2种碳酸酯作为Ti6Al4V/钢摩擦副的润滑剂所表现出的减摩抗磨和承载能力优于其相对应的脂肪醇;载荷和频率明显影响Ti6Al4V/钢摩擦副在碳酸酯润滑下的摩擦磨损行为;碳酸二-2-乙基己酯所表现出的减摩抗磨和承载能力明显优于碳酸二辛酯;2种碳酸酯对Ti6Al4V/钢摩擦副的润滑机制为在Ti6Al4V磨损表面形成吸附膜,从而起到减摩抗磨的作用。