接触载荷对7075铝合金扭转复合微动摩擦学行为的影响

在新型扭转复合微动试验机上,以7075铝合金平面/GCr15钢球配副为研究对象,研究不同接触载荷对7075铝合金扭转复合微动磨损行为的影响。在动力学特性分析的基础上结合磨痕形貌微观观察,研究7075铝合金扭转复合微动的磨损机理。结果表明:接触载荷明显地改变微动运行区域,随着接触载荷的增加,微动推迟进入混合区和滑移区,且混合区逐渐扩大;在相同的微动运行区域内,Ft/Fn系数随循环次数增加的变化趋势受接触载荷的影响不大,但Ft/Fn系数随着法向接触载荷的增加依次降低;在其它参量不变的情况下,接触载荷越大,微动更趋向于受扭动微动分量控制,表面损伤伴随着明显的剥落。扭转复合微动的磨损机制主要为磨粒磨损、氧化磨损和剥层。     

扭动微动磨损的研究进展和现状

扭动微动磨损是微动磨损的一种,文中介绍了国内外扭动微动磨损的研究进展及成果,综述了典型金属材料、高分子材料和天然软骨的扭动微动磨损的研究结果,包括扭动微动的摩擦运行行为、材料响应行为、界面的摩擦化学行为、损伤物理模型和演变规律等,对于不同种类材料在部分滑移区、混合区、滑移区的损伤规律进行了系统的总结,发现了扭动微动运行区域特性具有与其它模式的微动磨损不同的特点等一系列现象,并探讨了其今后的可能的发展方向和研究重点。     

钛及其合金的扭动微动摩擦磨损特性

采用新型扭动微动试验机在法向载荷为50、80和110 N及角位移幅值为0.3°~10°的条件下进行TA2和TC4合金与ZrO2对磨球的扭动微动试验。在摩擦动力学行为研究的基础上,结合磨痕形貌微观分析,考察TA2和TC4合金的扭动微动磨损特性。结果表明:可用摩擦扭矩—角位移曲线和摩擦扭矩时变曲线表征合金的扭动微动行为,获得了TA2和TC4合金的扭动微动运行工况微动图,TA2合金的混合区较TC4合金的宽。摩擦扭矩随法向载荷和角位移幅值的增加而增加,在相同试验条件下,TA2合金的摩擦扭矩始终大于TC4合金的。在部分滑移区,损伤轻微;在混合区和滑移区,损伤加剧,扭动微动摩擦磨损机制主要为磨粒磨损、氧化磨损和剥落。     

7075铝合金在VG46油润滑工况下的扭转复合微动磨损特性

采用球/平面接触方式,考察7075铝合金在VG46油润滑工况下不同倾斜角度和角位移幅值对扭转复合微动磨损特性的影响。利用光学显微镜(OM)、扫描电子显微镜(SEM)分析7075铝合金的磨痕表面及剖面形貌、磨损机制,用双模式表面轮廓仪分析磨损体积。结果表明:润滑油对扭转复合微动运行和损伤机制存在显著影响,润滑油明显改变微动运行区域,随着倾斜角度的增加,微动的混合区逐渐缩小甚至完全消失。微动运行区域对润滑油的润滑性能也有重要影响,在部分滑移区,微滑仅发生在接触边缘,润滑油对微动的影响甚微;在混合区,润滑油渗入表面微裂纹加速了疲劳裂纹的扩展;在滑移区,接触界面间形成了润滑油膜,显著地减缓了微动损伤。     

Ti6Al7Nb合金氮离子注入层在小牛血清溶液中的扭动微动摩擦磨损性能

利用高能离子注入及增强沉积系统对Ti6Al7Nb合金做了不同剂量的氮离子注入处理,采用球/平面接触模式,对Ti6Al7Nb合金及其离子注入层/ Zr2O球（直径为25.2 mm）接触副在小牛血清介质条件下进行了扭动微动磨损实验研究。结合动力学分析,借助X射线衍射仪（XRD）、三维形貌仪（3D-profiler）和扫描电镜（SEM）分析了测试材料成分及其扭动微动磨损磨痕形貌和微观组织结构, 探讨了Ti6Al7Nb合金及其离子注入层的扭动微动运行行为和损伤机制。结果表明：N+离子注入在钛合金表面形成了氮化钛层,使钛合金表面的微观硬度明显提高,随着注入剂量的增加,钛合金的硬度逐渐升高,磨痕逐渐变小,磨粒逐渐变细,其抗扭动微动磨损性能也提高     

氮离子注入浓度对钛及其合金扭动微动磨损性能的影响（英文）

通过等离子体浸没离子注入,在纯钛及Ti6Al7Ni和Ti6Al4V合金表面进行不同剂量的氮离子注入处理。采用ZrO_2球与未处理和处理的钛及其合金平面摩擦副,以小牛血清溶液作为模拟生理介质,进行扭动微动磨损试验。研究氮离子注入处理后钛及其合金表面的特征以及注入剂量对材料扭动微动性能的影响。结果表明:氮离子注入浓度和角位移幅值显著影响钛及其合金的扭动微动运行和损伤行为。随着氮离子浓度增加,扭动微动运行边界向小角位移幅值滑移,中心轻微磨损区减少。钛及其合金的磨损机理为氧化磨损、磨粒磨损和剥层,磨粒磨损是离子注入层的主要磨损机理。     

接触载荷对TC4钛合金微动磨损行为的影响

目的在不同的载荷和位移幅值下,结合微动图研究微动接触状态、滑移状态、损伤体积三者对微动摩擦磨损的影响以及不同微动接触状态和滑移状态下材料的损伤机理,为机械构件的微动磨损防护设计提供一定的理论支持。方法在相对湿度为50%、干摩擦条件下,运用SRV-V摩擦实验机,采用球/平面接触形式研究了TC4钛合金/GCr15钢球摩擦副的微动摩擦磨损行为。实验后,用原子力显微镜、纳米压痕仪、三维光学轮廓仪、场发射扫描电子显微镜及其自带的EDS,测试TC4试样的表面形貌及粗糙度、弹性模量与硬度、磨损体积与截面形貌和显微结构及磨斑、磨屑形貌成分等。结果在较低法向载荷下,完全滑移(GSR)占主导地位。磨粒磨损、粘着磨损、氧化磨损以及疲劳脱层是主要的损伤机理。另一方面,在较高法向载荷下,混合滑移(MSR)、部分滑移(PSR)占主导地位。损伤机制是由于高的应力集中,导致疲劳裂纹。此外,不同的微动运行条件下和材料损伤区域也不相同。完全滑移条件下,损伤主要集中在磨斑中心,而部分滑移条件下,损伤主要集中在磨斑边缘。结论切向摩擦力、微动振幅是影响微动磨损的重要因素。小位移幅值下,磨屑可以减缓接触面钛合金基体材料的微动磨损;而大位移幅值下,磨屑会加剧接触面基体材料的微动磨损。     

LZ50钢低温离子渗硫转动微动摩擦学性能研究

在LZ50钢表面进行低温离子渗硫处理,研究了渗硫层及LZ50钢基体在干态不同角位移幅值下的转动微动磨损行为.在对渗硫层及LZ50钢基体转动微动摩擦动力学特性分析的基础上,对其转动微动损伤行为进行了分析.结果表明:渗硫层结构主要由FeS和FeS2相组成;渗硫层及LZ50钢基体的转动微动运行区域强烈依赖于转动角位移幅值,呈现部分滑移和完全滑移两个微动区域,混合区未观察到,且渗硫层未改变LZ50钢基体的微动运行区域;在整个部分滑移区和滑移区的跑合阶段,由于渗硫层的固体润滑作用,使摩擦因数均低于LZ50钢基材;渗硫层可以显著降低基材的磨损,在部分滑移区损伤轻微,在滑移区的损伤机制主要表现为剥层、磨粒磨损和氧化磨损.     

微动条件下CF8M阀门用钢的疲劳特性研究

通过弯曲微动疲劳实验,分析了CF8M钢在不同弯曲载荷下的疲劳特性。结果表明,不同于常规疲劳,试验钢的S-N曲线出现"C"曲线特性;微动区由混合区、滑移区和部分滑移区三个区域组成,且处于混合区的阀门磨损最严重,使用期限最短;试验钢的弯曲微动疲劳存在磨粒磨损、剥层和氧化磨损三种磨损机制,部分滑移区产生的损伤最小。     

XPS原位分析纯铁微动磨损摩擦氧化行为∗

摩擦化学是微动磨损过程中不可避免产生的一种复杂的摩擦学行为,对材料的磨损性能及磨损机理具有重要的影响。 基于原位 XPS 高精度切向微动磨损试验平台,系统性研究工业纯铁在真空（p=4 mPa）和大气环境下不同微动运行区域接触界面摩擦化学状态及其微动磨损行为。试验结果表明,工业纯铁在大气环境下未观察到微动混合区,然而真空环境下因接触界面发生了严重粘着效应,使得微动运行难以进入滑移区而具有较宽的混合区。随着位移幅值的增加,工业纯铁在真空环境下的微动磨斑具有更多的 Fe 基体暴露,并伴有以 FeO 为主的氧化物,整体表现出较高的磨损量;相对比,在大气环境下其磨斑表面产物为以 FeO 和 Fe₂O₃为主的氧化物,特别在滑移区几乎没有 Fe 单质暴露,且磨斑表面主要以 Fe₂O₃氧化物为主, 表现出较真空环境下更轻微的磨损。磨损结果表明,FeO 和 Fe₂O₃ 具有较好的润滑保护作用,特别是 Fe₂O₃ 氧化物能显著提高材料表面抗微动磨损性能。利用原位 XPS 技术可以实现表征材料接触表面真实的摩擦化学状态,且更加准确地揭示摩擦氧化反应对微动磨损行为的影响作用机理,对丰富和发展微动磨损基础理论具有科学意义。     

Torsional fretting corrosion behaviours of Ti6Al4V alloys in Hank’s simulated body fluid

ABSTRACT

Torsional fretting corrosion in a physiological medium is one of the main reasons that artificial joints fail. In this study, we carried out experiments on torsional fretting corrosion in Titanium alloys (Ti6Al4V) against Zirconium dioxide (ZrO₂) ceramic balls under 37°C in a Hank’s simulated body fluid. During the tests, we recorded electrochemical corrosion parameters using an electrochemical analysis system in real-time. We analysed the torsional fretting dynamics behaviours, damage mechanisms, and electrochemical corrosion behaviours in detail using the micro-examinations of a scanning electron microscope (SEM), an energy-dispersive X-ray (EDX), a profilometer, and an X-ray photoelectron spectrometer (XPS). The results showed that the dynamics behaviours strongly depended upon the torsional angular displacement amplitude and the number of cycles. The friction torque increased with increases in the torsional angular displacement amplitude and normal load. We established a running condition fretting map (RCFM), which included three fretting running regimes: a partial slip regime (PSR), a mixed fretting regime (MFR), and a slip regime (SR). We determined that the influences of torsional fretting on electrochemical corrosion behaviours were strongly correlated to the angular displacement amplitude. Under large angular displacement amplitudes, the corrosion of the Ti6Al4V alloys in Hank’s simulated body fluids were accelerated by torsional fretting, especially during the initial stage of the test. However, when the angular displacement amplitude was smaller than 1°, the corrosion potentials and corrosion currents were almost invariable during the entire duration of the test. The damage to the Ti6Al4V alloy was the result of wear and corrosion. The wear mechanisms were attributable to delamination and abrasive wear in the three fretting regimes. We observed almost no damage on the contact centre and only slight scratches and wear on the contact edge in the PSR. In MFR testing, the damage zone extended to the contact centre and the sticking zone (which exhibited no damage) contracted to the contact centre with increases in the number of cycles. Ultimately, in MFR and SR testing, the damage mechanisms were primarily the result of abrasive wear, oxidation wear, tribochemical reactions, adhesion wear, and electrochemical corrosion.     

Friction and wear of 7075 aluminum alloy induced by torsional fretting

The torsional fretting wear tests of 7075 aluminum alloy flat against 52100 steel ball in dry condition were carried out on a new high-precision torsional fretting-wear tester.The kinetics behaviors and damage mechanism of 7075 aluminum alloy under different angular displacement amplitudes were investigated in detail.The results show that the torsional fretting running behaviors of 7075 aluminum alloy can be defined by three fretting regimes(i.e.partial slip regime(PSR),mixed fretting regime(MFR) and slip r...     

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.     

Fretting wear behavior of Ti/TiN multilayer film on uranium surface under various displacement amplitudes

Ti/TiN multilayer film was deposited on uranium surface by arc ion plating technique to improve fretting wear behavior. The morphology, structure and element distribution of the film were measured by scanning electric microscopy (SEM), X-ray diffractometry (XRD) and Auger electron spectroscopy (AES). Fretting wear tests of uranium and Ti/TiN multilayer film were carried out using pin-on-disc configuration. The fretting tests of uranium and Ti/TiN multilayer film were carried out under normal load of 20 N and various displacement amplitudes ranging from 5 to 100 μm. With the increase of the displacement amplitude, the fretting changed from partial slip regime (PSR) to slip regime (SR). The coefficient of friction (COF) increased with the increase of displacement amplitude. The results indicated that the displacement amplitude had a strong effect on fretting wear behavior of the film. The damage of the film was very slight when the displacement amplitude was below 20 μm. The observations indicated that the delamination was the main wear mechanism of Ti/TiN multilayer film in PSR. The main wear mechanism of Ti/TiN multilayer film in SR was delamination and abrasive wear.     

Effect of nitrogen ion implantation dose on torsional fretting wear behavior of titanium and its alloy

Various doses of nitrogen ions were implanted into the surface of pure titanium, Ti6Al7Nb and Ti6Al4V, by plasma immersion ion implantation. Torsional fretting wear tests involving flat specimens of no-treated and treated titanium, as well as its alloys, against a ZrO₂ ball contact were performed on a torsional fretting wear test rig using a simulated physiological medium of serum solution. The treated surfaces were characterized, and the effect of implantation dose on torsional fretting behavior was discussed in detail. The results showed that the torsional fretting running and damage behavior of titanium and its alloys were strongly dependent on the dose of the implanted nitrogen ions and the angular displacement amplitude. The torsional fretting running boundary moved to smaller angular displacement amplitude, and the central light damage zone decreased, as the ion dose increased. The wear mechanisms of titanium and its alloys were oxidative wear, abrasive wear and delamination, with abrasive wear as the most common mechanism of the ion implantation layers.     

微动图在抗微动失效中的应用

本文详细介绍了微动运行机制和破坏特性的二类微动图;运行工况微动图由部分滑移区、混合区和滑移区组成;材料响应微动图可分为轻微损伤医、裂纹区和表面磨损区。进一步研究证明微动破坏与微动区域有密切关系。其次,从微动图的角度出发,结合实际经验和文献研究,作者试图在改变微动区域、增加表面强度、利用润滑、合理选择材料及匹配等四方面对减缓微动破坏提出指导性意见。     

LZ50钢离子渗氮层的转动微动磨损行为

利用离子渗氮技术在LZ50钢表面进行渗氮处理.对渗氮层及其基体材料(LZ50钢)在干态不同角位移幅值下进行转动微动磨损试验,并采用扫描电子显微镜(SEM)、电子能谱仪(EDX)和轮廓仪对磨痕形貌进行了分析.结果表明:渗氮层虽没有改变LZ50钢的转动微动运行区域特性,但显著降低了基体的摩擦系数,并提高了基体的耐磨性.在部分滑移区,渗氮层损伤轻微,仅呈现零星点状压痕;滑移区,渗氮层的损伤主要表现为剥层和磨粒磨损.