微织构对硬质合金表面摩擦性能的影响

微织构是一种有效地改进表面摩擦性能和提高表面承载能力的措施.为了研究微织构在刀具减磨技术方面的应用,本文在WC-Co硬质合金材料表面制作出微坑阵列,与Ti6Al4V构成摩擦副,在微量润滑(MQL)条件下进行摩擦磨损试验.研究发现:红MQL条件下,微织构对WC-Co/Ti6Al4V摩擦副具有一定的减磨效果,低速高载和高速...     

脂肪醇对Ti6Al4V/钢摩擦副摩擦磨损性能的影响

采用SRV型摩擦磨损试验机分别考察了Ti6Al4V/钢摩擦副在多种脂肪醇润滑下的摩擦磨损性能。结果表明,与液体石蜡相比,碳链长度小于碳8的脂肪醇作为Ti6Al4V/钢摩擦副的润滑剂表现出良好的润滑性能,其润滑机制是在Ti6Al4V磨损表面形成吸附膜。载荷和频率明显影响Ti6Al4V/钢摩擦副在脂肪醇润滑下的摩擦磨损行为和摩擦磨损机制:当载荷较小时,Ti6Al4V磨损表面主要发生轻微的擦伤;随着载荷增加,Ti6Al4V磨损表面擦伤严重并在更高载荷下发生较为严重犁沟和塑性变形。     

高速切削钛合金Ti6Al4V切屑的形成及其数值模拟

应用Hopkinson压杆实验装置,确定了航空用钛合金Ti6Al4V高应变和高温条件下的应力-应变关系,结合Ti6Al4V合金准静态试验数据,建立了适合高速切削仿真的Johnson-Cook本构模型;通过有限元数值模拟,仿真了高速切削Ti6Al4V合金的锯齿状切屑形成过程,分析了整个锯齿状切屑形成过程的切削力、切削温度、等效塑性应变的变化,深入探讨了锯齿状切屑的形成机理;将模拟计算得到的切削力和切削温度与试验结果进行了比较,两者具有较好的一致性。
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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。     

Ti6Al4V/WC-Co干摩擦性能研究

利用Optimal SRV高温摩擦磨损试验机,研究干摩擦条件下钛合金(Ti6Al4V)对硬质合金(WC-Co)的摩擦学性能.研究了载荷、温度与滑动速度对摩擦过程的影响,通过磨损区微观形貌表征分析了磨损机理.结果表明:Ti6Al4V与WC-Co的摩擦系数波动剧烈,产生了严重的黏滑摩擦,且随着载荷、温度与滑动速度的增加,黏...     

磷嗪对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考察Ti6Al4V-钢摩擦副在磷嗪(X-1P)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Ti6Al4V磨斑表面形貌和典型元素的化学状态。结果表明,X-1P作为Ti6Al4V-钢摩擦副的润滑剂,具有很好的润滑性能;摩擦因数随载荷的增加变化不显著,磨损率随载荷的增加逐渐增大;频率和振幅明显影响摩擦学性能,磨损率随频率的增加逐渐减小,随振幅的增加逐渐增大;在Ti6Al4V-钢摩擦副中,X-1P由于含有极性元素F、P,Ti6Al4V的磨损表面主要发生腐蚀磨损,其磨损机制为X-1P在磨损表面发生摩擦化学反应,形成一层含O、C、F、N、P的保护膜以及金属氟化物,从而起到抗磨减摩作用。     

磷酸酯对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3种磷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,磷酸三甲苯酯作为Ti6Al4V/钢摩擦副的润滑剂,其摩擦学性能明显好于磷酸二(2-乙基己基)酯和磷酸三丁酯.载荷和频率对磷酸三甲苯酯摩擦因数和磨损率的影响不同,摩擦因数随载荷和频率的增加变化不显著,磨损率随载荷的增加逐渐增加,随频率的增加先急剧下降,然后缓慢降低并趋于稳定;其磨损机制为在磨损表面形成牢固的边界膜,保护底材不受磨损.     

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。     

Ni+注入参数对Ti6Al4V表面改性层生物摩擦学性能的影响

为改善Ti6Al4V表面的生物摩擦学性能,把不同能量与剂量的Ni~+注入到Ti6Al4V表面以形成表面改性层。用Nano IndenterⅡ型纳米显微力学探针测定表面改性层的纳米硬度,在MRTR多功能摩擦磨损试验机上以Zr O2球/改性层为摩擦副,以透明质酸钠溶液润滑剂在室温下进行生物摩擦学实验,使用S-3000N扫描电子显微镜观察生物摩擦学试验后试样的磨痕形貌并分析磨损机制。结果表明:Ni~+注入Ti6Al4V表面的形成相为Ti2Ni;随着注入能量和剂量增加,改性层中Ti2Ni的质量分数增加,改性层的纳米硬度增加,摩擦因数下降,且磨损出现不同程度的减轻;注入能量增加比剂量增加更有利于提高改性层的生物摩擦学性能。     

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。     

Tribological Behavior of Ti3Al2.5V Alloy Sliding against EN-31 Steel under Dry Condition

This article aims to study the friction and wear behavior of Ti3Al2.5V alloy sliding against EN-31 steel under dry condition using a multi-tribotester. The effect of variation in load and sliding velocity on wear rate, average coefficient of friction, and contact temperature has been studied and analysis of wear debris has been carried out. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were employed to study the morphology of the wear tracks and deduce microchemical information at the elemental level of worn samples, respectively. Results reveal that the wear rate of Ti-3Al-2.5V increases with increasing sliding velocity and increasing normal load with few exceptions. The average coefficient of friction decreases as the normal load increases with exceptions at some loads. SEM micrographs of worn samples obtained at different loads and sliding velocities show the formation of wear tracks on the surface due to ploughing and flaking of the matrix. The main mechanism responsible for wear of Ti3Al2.5V alloy sample is rupture of the matrix and abrasion. Wear debris analysis shows irregular-shaped wear particles with very sharp edges that appeared to be plastically deformed at high sliding velocity, whereas the wear debris is very loose and fine at lowest sliding velocity.     

Improvement of the Oxidation and Wear Resistance of Pure Ti by Laser-Cladding Ti<Subscript>3</Subscript>Al Coating at Elevated Temperature

Ti₃Al coating was in situ synthesized successfully on pure Ti substrate by laser-cladding technology using aluminum powder as the precursor. The composition and microstructure of the prepared coating were analyzed by transmission electron microscopy, scanning electron microscopy (SEM), and X-ray diffraction technique. Thermal gravimetric analysis was used to evaluate the high-temperature oxidation resistance of the Ti₃Al coating. The friction and wear behavior was tested through sliding against Si₃N₄ ball at elevated temperature of 20, 100, 300, and 500°C. The morphologies of the worn surfaces and wear debris were also analyzed by SEM and three-dimensional non-contact surface mapping. The results show that the Ti₃Al coating with high microhardness, high-temperature oxidation resistance, and high temperature wear resistance. The pure Ti substrate is dominated by severe adhesion wear, abrasive wear, fracture, and severe plastic deformation at lower temperature, and severe adhesion wear, abrasive wear, plastic deformation, oxidation, and nitriding wear at higher temperature, whereas the Ti₃Al coating experiences only moderate abrasive and adhesive wear when sliding against the Si₃N₄ ceramic ball counterpart. In addition, the wear debris of the laser-cladding Ti₃Al coating sliding and Si₃N₄ friction pairs are much smaller than that of pure Ti substrate and Si₃N₄ friction pairs at elevated temperature.     

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.     

Multi-pass scratch test behavior of modified layer formed during plasma nitriding

316L stainless steel and Ti6Al4V alloy were plasma nitrided at different treatment parameters, and the wear behaviors of the modified layers formed on the surface during nitriding were investigated by multi-pass scratch test. Phase structure and cross-sections of modified layers were also examined with XRD and SEM. While a single modified layer formed on surface of the 316L stainless steel, both modified and diffusion layers were observed on the surface of the Ti6Al4V alloy after nitriding. As a result, it was observed that phase structure and thickness for modified layers of 316L stainless steel and Ti6Al4V alloy, respectively, were the significant parameters for friction coefficient and wear rate. In addition, diffusion layer formed during the nitriding process caused on increase of wear resistance of Ti6Al4V alloy by supporting the modified layer on the surface.     

Tribological behaviors of Ti–6Al–4V modified by chemical methods

In order to improve the tribological properties of titanium-based implants, sodium hydroxide (NaOH), hydrogen peroxide (H₂O₂) solutions, sol–gel hydroxyapatite (HA) film, thermal treatment and combined methods of NaOH solution/HA film, H₂O₂ solution/HA film are used to modify the surfaces of Ti–6Al–4V (coded TC4). The chemical states of some typical elements in the modified surfaces were detected by means of X-ray photoelectron spectroscopy (XPS). The tribological properties of modified surfaces sliding against an AISI52100 steel ball were evaluated on a reciprocating friction and wear tester. As the results, complex surfaces with varied components are obtained. All the methods are effective in improving the wear resistance of Ti–6Al–4V in different degrees. Among all, the surface modified by the combined method of NaOH solution/HA film gives the best tribological performances. The friction coefficient is also greatly reduced by the modification of NaOH solution. The order of the wear resistance under 3 N is as following: Ti–NaOH–HA>Ti–NaOH>Ti–HA>Ti–H₂O₂–HA>Ti–H₂O₂ >Ti–500; under 1 N is Ti–HA, Ti–NaOH–HA>Ti–NaOH. For Ti–H₂O₂, a very low friction coefficient and long wear life over 2000 passes is obtained under 1 N. SEM observation of the morphologies of worn surfaces indicates that the wear of TC4 is characteristic of abrasive wear. Differently, abrasion, plastic deformation and micro–crack dominate the wear of Ti–HA; slight abrasive wear dominate the wear mechanism of Ti–NaOH and microfracture and abrasive wear for Ti–NaOH–HA and Ti–H₂O₂–HA, while the sample modified by thermal treatment is characterized by sever fracture. The superior friction reduction and wear resistance of HA films are greatly attributed to the slight plastic deformation of the film. NaOH solution is superior in improving the wear resistance and decreasing the friction coefficient under relative higher load (3 N) and H₂O₂ is helpful to reduce friction and wear under relatively lower load (1 N). Combined method of Ti–NaOH–HA is suggested to improve the wear resistance of Ti–6Al–4V for medial applications under fretting situations.     

Investigate on effect of cryogenic cooling on oxidation wear of WC-Co carbide tool milling titanium alloy

Abstract

For titanium alloy at high cutting speed, the severe tool wear will ineluctably take place diminishing the available tool life because of the high instantaneous temperature rise. Especially the WC-Co material in carbide tool will be reacted with the oxygen element in the air and generate oxide, and the tool oxidation wear is inevitable. In milling Ti–6Al–4V alloy operations, this article presents the first comprehensive investigation on the oxidation wear effect of cryogenic cooling on carbide tool compared with the conventional cooling. Based on the Gibbs free energy of the chemical reaction, the machining characteristics of the oxidation reactions were analyzed in detail. A series of machining testes were executed adopting controllable cryogenic cooling milling system. The surface and cross-section morphology and phase composition characteristics of tool were measured by SEM and XRD measuring equipments, as well as the oxidation wear mechanism of tool in cryogenic cooling. The results show that the thermal oxidation degree of the elements of WC-Co is higher in the conventional cooling processing. After cryogenic cooling intervention, oxidation reactions in tool are reduced significantly. Even the most probable reaction is disappeared, and the oxidation degree is decreased. When the temperature drops to 180 K, it has the best cooling effect. In cryogenic, the effective binding of WC crystal particle to the adhesive phase Co is a major factor for inhabiting oxidation wear of tool. The investigations indicate that the cryogenic cooling method can effectively inhibit the oxidation effect of carbide tool in milling titanium alloy process, and it improves the resist oxidation ability of tool.     

Correlation between the characteristics of the thermo-mechanical mixed layer and wear behaviour of Ti–6Al–4V alloy

The sliding friction and wear behaviours of Ti–6Al–4V alloy were investigated under dry sliding wear conditions. The wear tests were carried out on a pin-disc tribometer at sliding speeds from 30 m/s to 70 m/s and at contact pressure ranging from 0.33 MPa to 1.33 MPa. Pins of the Ti–6Al–4V alloy are used in both solution treated and aged conditions. The objective of the study is to understand the influence of thermo-mechanical mixed layers (TMML), which form on the surface of the worn material during the course of the wear test, on the friction and wear behaviour. Detailed characterization of the TMML was carried out using SEM, EDS and micro-hardness testing in order to understand the influence of test velocity and contact pressure on the composition, hardness and thickness of the TMML formed. The influence of the TMML on the friction and wear behaviour was also studied. On the basis of the above characterization, it was demonstrated that the observed friction and wear behaviour of Ti–6Al–4V alloy can be best understood in terms of the formation and fracture rate of the TMML rather than the bulk properties of the material.     

Biotribological properties of Ti/TiB2 multilayers in simulated body solution

Ti/TiB₂ multilayers with various modulation ratios were prepared by magnetron sputtering on biomedical titanium alloy Ti6Al4V. The tribological properties of the multilayers sliding against ultra-high molecular weight polyethylene under lubrication with Hank׳s solution were also investigated. The results demonstrated that the tribological properties strongly depended on the modulation ratios of multilayers. The coefficient of friction of multilayers with a modulation ratio of 1:5 was 0.1, a reduction by 28.6%; the wear volume loss of UHMWPE decreased by almost one order of magnitude compared to that of Ti6Al4V alloy, exhibiting excellent anti-friction and anti-wear properties. The oxidation wear of Ti6Al4V alloy could be restrained effectively and converted to abrasion wear and/or adhesive wear by the laminate structures in the multilayers, suggesting that this material may serve as a potential candidate for the surface modification of artificial joints.