Fretting Wear Behavior and Mechanism of Inconel 690 Alloy Related to the Displacement Amplitude

Fretting wear tests on Inconel 690 alloy were carried out at different displacement amplitudes. The results indicated that with an increase in displacement amplitude, the ratio of tangential force to normal load and wear volume increased. The fretting mode gradually transformed from mostly stick, mixed stick–slip, to full sliding, showing the competition of fretting-induced fatigue cracking and fretting-induced wear. There was a gradient plastic strain created by fretting, which resulted in the formation of a nanocrystalline tribologically transformed structure (TTS) and plastic deformation layers. The plastic strain in the plastic deformation layer gradually increased with an increase in displacement amplitude.     

Investigation on the Fretting Wear Behavior and Mechanisms of Alloy 690TT during the Transformation from Mixed Regime to Partial Slip Regime Induced by Elevated Temperature

Fretting wear of Alloy 690TT can occur in the steam generator of a nuclear power plant, in which the interfacial conditions are changed as the temperature varies. In this study, the gradual transformation from the mixed fretting regime (MFR) to the partial slip regime (PSR) occurred with an increase in test temperature. Correspondingly, there was a competition in wear modes due to the formation of a nanostructured tribologically transformed structure (TTS), presence of delamination cracking, nucleation of fatigue cracks, and oxidation. Delamination within the TTS dominated first. As the area of TTS and the plastic deformation region was reduced, fatigue cracks began to initiate. Oxidation was accelerated by an increase in the test temperature, and that effect resulted in reduced wear volume of Alloy 690TT in the MFR.     

Effect of Cold Rolling on the Fretting Wear Behavior and Mechanism in Inconel 600 Alloy

The fretting test was carried out using an SRV IV fretting test rig in order to investigate the fretting wear behavior and mechanism in Inconel 600 alloy at room temperature. The materials were rolled to different reductions before the test. The effect of cold rolling on the friction coefficient and wear volume was subsequently investigated. The surface and cross-sectional morphologies of the wear scar were studied by scanning electron microscopy (SEM), laser scanning confocal microscopy (LSCM), and electron back-scattering diffraction (EBSD). The results indicated that the cold rolling had a different effect on wear behavior in different slip regimes. In the stick regime, cold rolling strongly decreased the wear volume, although it did not affect the friction coefficient. The 25% rolled specimen had the minimum wear volume. The mechanisms of as-received and 50% rolled specimens were delamination and oxidation wear, whereas for the 25% rolled specimen, cracking was the main wear mechanism. In the gross slip regime, cold rolling had little effect on the friction coefficient or wear volume. The fretting wear process gave rise to a decrease in the Σ3 grain boundary, an increase in local misorientation, and a change in the crystal orientation.     

The Effects of Sodium Chloride Solution on Fretting Wear Behavior of Nickel Based Alloy in Partial Slip Regime

The investigations on fretting wear behaviors of nickel based alloy in NaCl solution and atmosphere indicated that wear mechanism and regional transformation from partial slip regime (PSR) to the mixed regime (MR) are significantly affected by NaCl solution. The crevice corrosion induced by synergy of chloride ion and deformed asperities caused wear mechanism changed from adhesive and oxidation wear (PSR in atmosphere) to abrasive and oxidation wear (PSR in NaCl solution) and to oxidation and delamination wear (MR in NaCl solution), meanwhile accelerated the regional transformation from PSR to MR. However, the annular fatigue crack was almost unaffected by NaCl solution, which propagated along the direction of 40-50^° to surface in the mode of transgranular and intergranular in all conditions.     

Mo离子注入提高TC4合金微动磨损抗力的研究

对TC4合金进行了Mo离子注入表面改性处理,利用摩擦磨损试验机进行了点接触微动磨损试验,借助读数显微镜和表面粗糙度仪测量出有关参数,计算出试样的微动磨损体积。结果表明,Mo离子注入使试样表面硬度提高,微动磨损体积明显降低。在微动磨损初期,Mo离子注入具有较好的减摩效果。Mo离子注入带来的表面强化效应是基体合金的微动磨损抗力得以提高的主要原因。     

高温下位移幅值对TC4合金磨损性能的影响

钛合金的微动磨损会加速裂纹的形成与扩展,导致其构件提前失效。利用摩擦磨损试验机考察TC4合金在300和500℃温度下的微动磨损行为,利用扫描电子显微镜和激光共聚焦显微镜对磨痕轮廓及磨痕表面进行分析,探讨在300和500℃温度下TC4合金在不同位移幅值作用下的微动磨损机制。实验结果表明：高温条件下,试样平均摩擦因数和磨损率随位移幅值的增加呈现先增大后减小的趋势;两种高温环境中,小位移幅值时,微动运行区域为部分滑移区,主要损伤机制为黏着磨损和氧化磨损;位移幅值为100μm时,微动运行区域为混合滑移区,主要磨损机制为氧化磨损、剥层磨损及塑性变形;大位移幅值时,微动运行区域为完全滑移区,主要磨损机制为磨粒磨损和疲劳磨损。对比300和500℃条件下磨损结果,表明温度越高TC4合金耐磨性能越好,这主要是由于摩擦生成的氧化物TiO₂和Fe₂O₃对磨损表面具有保护作用。     

TiAlZr合金微动磨损性能研究

采用高精度液压式微动磨损试验机研究了TiA lZr合金在不同微动运行区域的微动磨损行为,建立了其运行工况微动图。试验结果表明:滑移区、混合区和部分滑移区的摩擦因数随循环次数变化呈现不同的规律,其中部分滑移区摩擦因数较低,磨损体积随着位移幅值的增大而增大;滑移区、混合区磨损体积随着法向载荷的增加而增大,而部分滑移区磨损体积随着法向载荷的增加而减小;滑移区磨屑堆积于中心区域,磨损以磨粒磨损和剥层机制为主;混合区磨损机制主要表现为粘着磨损与磨粒磨损并存;部分滑移区磨损轻微。     

TC4合金微动磨损过渡区摩擦行为

为研究TC4合金微动磨损过渡区摩擦行为特点,采用SRV-IV微动摩擦磨损试验机,对球/平面接触的GCr15钢球/合金TC4摩擦副在100 N法向载荷下进行微动磨损试验,得到TC4合金微动磨损过渡区的范围,分析不同状态下摩擦因数演变及磨痕表面形貌特点,研究磨损机制的变化。结果表明:微动状态下,摩擦因数在磨合阶段波动剧烈,达到稳定磨损阶段后趋于稳定,且稳定状态下的摩擦因数随着位移幅值的增加而增加;往复滑动状态下,不同位移幅值下的摩擦因数曲线近乎重合且波动剧烈;微动磨损过渡区的摩擦因数变化处于2种状态的转变阶段。微动状态下,磨痕表面轮廓线粗糙,损伤轻微,磨损机制以黏着磨损和疲劳剥层为主;往复滑动状态下,轮廓线更光滑且损伤严重,磨损机制以磨粒磨损及塑性变形为主;微动磨损过渡区轮廓线由粗糙变为光滑,磨损深度及宽度突增,磨损机制由黏着磨损转变为磨粒磨损。     

有机钼复合润滑剂在高温微动和滑动条件下的摩擦磨损行为

以矿物基650SN油作为基础油,采用复配技术制备了有机钼复合润滑剂。利用SRV微动磨损试验机和T-11滑动磨损试验机考察了该复合剂的高温摩擦学行为,采用扫描电子显微镜和X射线光电子能谱仪对其润滑下的磨痕表面形貌和表面膜的元素组成进行了分析,探讨了复合剂的减摩润滑机制。结果表明:有机钼复合剂具有良好的高温微动和滑动摩擦学行为,与基础油相比,复合剂能够使钢-钢摩擦副在高温微动和滑动过程中的摩擦因数降低28%和43%,抵抗微动和滑动磨损的能力分别提高53%和54%。这是由于有机钼复合剂通过分解、吸附和摩擦化学反应,在摩擦副金属表面形成了含磷酸盐的沉积膜和含FeS、MoS2的化学反应膜共同组成的复合边界润滑膜,从而表现出优良的减摩润滑效果。     

Effects of Loading and Sliding Speed on the Dry Sliding Wear Behavior of Mg-3Al-0.4Si Magnesium Alloy

The friction and wear properties of Mg-3Al-0.4Si alloy were investigated using a pin-on-disc tester. Morphologies and compositions of worn surfaces were characterized by scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS) for identification of the wear mechanisms. Microstructural evolution and hardness change in subsurfaces were analyzed by confocal scanning laser microscopy and hardness testing. The results revealed that the wear behavior of Mg-3Al-0.4Si alloy was classified into two types of wear regimes; that is, mild and severe. In the mild wear regime, wear rates increased at a low slope with increasing load; the corresponding wear mechanisms were oxidation, abrasion, and delamination. In the severe wear regime, wear rates increased rapidly at a high slope with load; the wear mechanisms were severe plastic deformation and surface melting. Analysis of microstructural evolution on the subsurface identified the reason for the transition from mild to severe wear; that is, the realization of dynamic recrystallization (DRX) in the surface layer material. A contact surface DRX temperature criterion for the mild to severe wear transition was proposed, and the critical DRX temperatures for the mild to severe wear transition were calculated using DRX kinetics.     

Mg97Zn1Y2镁合金的高温磨损行为

对Mg97Zn1Y2合金的室温磨损行为已有研究,但是缺乏高温磨损研究,探究该合金高温磨损行为是非常必要的。采用MG-2000型销-盘磨损试验机对Mg97Zn1Y2合金进行磨损试验,试验温度范围为20~200℃,加载范围为20~320 N,探究不同温度以及载荷对Mg97Zn1Y2合金磨损行为的影响。根据试验数据绘制不同温度下的磨损率曲线;应用SEM观察磨损表面形貌,应用EDS分析磨损表面的化学成分,划分磨损区间。结果表明：随着温度的升高,Mg97Zn1Y2合金的磨损率随载荷的增加而上升得更加显著,磨损行为可以分为轻微磨损和严重磨损两个阶段：轻微磨损阶段的磨损机制为：磨粒磨损、剥层磨损、氧化磨损;严重磨损阶段为严重的塑性变形和表面熔化。绘制了磨损机制转变图,划分该合金的安全工作区间,为该合金在高温下的摩擦学应用提供有益参考。     

ZM5镁合金微动磨损特性研究

采用高精度微动试验台研究了ZM5镁合金的微动磨损行为,法向载荷变化范围为50～200N、位移幅位为5～40μm。通过摩擦力-位移-循环次数变化分析,结合显微观测,结果表明:ZM5镁合金的微动磨损行为与微动区城特性密切相关。它的微动损伤形貌主要是磨损,在初期阶段的磨损机制主要是粘着和氧化,中后期是粘着、氧化和磨粒磨损共同作用的结果。     

Radial Fretting Behavior of Cortical Bone Against Titanium

Radial fretting tests of human cortical bone against two kinds of diameters titanium (TA2) balls were conducted. The damages of cortical bone aggravated with increase in the normal loads and cycles. Cracks propagating on the surface of cortical bone can be classified into four patterns among which the cracks propagated along the cement line were the most popular types. Critical load for crack initiation was also deduced to help analyzing the cause of the implant failure.     

载荷对径向微动磨损的影响

为了研究在实际工况中较为常见的圆柱/平面接触副的径向微动磨损特性,分析载荷对径向微动磨损影响,本文通过ANSYS建立圆柱/平面的径向微动磨损模型,分析施加载荷过程,不同时间点的载荷对径向微动磨损的影响,并通过接触切应力和X方向应力的分析,提出径向微动磨损在粘滑过渡点以及X方向应力为零的点为裂纹萌生点.     

Finite Element Modeling and Experimental Validation of Fretting Wear Scars in a Press-Fitted Shaft with an Open Zone

A finite element (FE)-based method was developed for simulating the fretting wear scar in a press-fitted shaft with an open zone. The method is based on the energy wear approach and is implemented via the commercial FE code ABAQUS. The effects of open zone, mesh size, cycle jumps technique, and increments per fretting cycle were investigated for optimization of this methodology. The results show that when assuming that the surface profile can be changed only in the open zone, the FE wear model gives a good prediction of the scar width. The mesh size has a great influence on the dimensions and shape of the scar profile; when the mesh size is about 3% of the width of the wear scar for a press-fitted shaft, the best compromise between the wear scar shape and the computational time can be achieved. For the cycle jump ΔN, an optimum value of 3,000 is found; above this value, the depth of the fretting wear scar increases rapidly with increasing ΔN. The impact of increments per fretting cycle on the depth of the predicted wear scar is small by comparison with cycle jump ΔN. The results of the optimized model are validated with respect to the experimental data obtained in the interrupted fretting fatigue tests. The FE wear model can provide an accurate prediction of the maximum wear depth and the width of fretting wear scar. The predicted wear depth inside of the contact is slightly larger than that found experimentally.     

等离子喷涂WC-12Co涂层滑移区高温微动磨损特性研究

利用等离子喷涂技术在TiAlZr钛合金基材上制备了WC-12Co涂层.XRD分析表明,等离子喷涂WC-12Co涂层主要以WC和W2C两相存在,并伴随少量的W,CoO和Co相.采用高精度高温液压式微动磨损试验机研究了涂层的微动磨损行为,用扫描电镜(SEM)、能谱仪(EDS)、激光共焦扫描显微镜(LCSM)对等离子喷涂WC-12Co涂层大气氛围中从室温(25 ℃)至400 ℃的滑移区微动磨损特性进行了研究,并与无涂层的TiAlZr钛合金基材进行了比较.结果表明:在室温(25 ℃)至400 ℃范围内,等离子喷涂WC-12Co涂层的摩擦因数随着温度的升高明显上升,而磨损体积基本不变;在此温度范围内,涂层的摩擦因数比基材低,磨损体积也比基材明显要低;等离子喷涂WC-12Co涂层提高了TiAlZr钛合金的抗高温微动磨损性能,其在室温(25 ℃)至400 ℃范围内的磨损机制主要以剥层形式为主,局部会有磨粒磨损.     

钛合金球与骨水泥界面之间的微动磨损机制研究

采用钛合金球与自制骨水泥试样以球/平面接触方式,在自制的微动摩擦磨损试验机上开展干摩擦和25%小牛血清介质中切向微动磨损试验研究,考察钛合金球与骨水泥界面之间的微动运行特性,并采用S-3000N型扫描电镜观察磨痕形貌来分析其微动磨损机制。结果表明:随着微动振幅的增加,微动运行由部分滑移区向混合区转变。随着接触载荷的增加,试样接触面之间更容易发生黏着。与干摩擦相比,在小牛血清溶液中部分滑移区向较大振幅区扩展。部分滑移区摩擦因数值较低且保持稳定,混合区的摩擦因数先增大后保持不变。稳定摩擦因数随着接触载荷的增加而减小,随微动振幅增大而增大。骨水泥试样的磨损量在小牛血清介质中比在空气中大,并且随接触载荷增大而增大。骨水泥在小牛血清介质中微动磨损的损伤机制主要为黏着磨损和疲劳磨损,溶液分子在应力作用下对骨水泥基体有削弱作用。     

扭转复合微动模拟及其试验研究

基于低速往复回转电动机系统和高精度六维力/转矩传感器,通过改变旋转轴的倾斜角α,成功实现了扭转复合微动,该微动属扭动微动和转动微动模式的复合。并对GCr15钢球/50钢平面在倾斜角度为10°和40°及不同扭转角位移幅值下的扭转复合微动进行初步考察,同时结合光学显微镜、扫描电子显微镜、表面轮廓仪等手段分析50钢的扭转复合微动运行行为、磨痕形貌及损伤机理。结果表明,该试验装置能真实模拟扭转复合微动;倾斜角和角位移幅值对扭转复合微动的运行和损伤行为有重要影响;可利用摩擦力—角位移幅值曲线来表征扭转复合微动行为,50钢摩擦力—角位移幅值曲线呈直线型、椭圆型和平行四边形型3种类型;其损伤特征明显不同于单一运行模式控制(扭动微动或转动微动)下的微动行为。此外,不对称的磨斑形貌是扭转复合微动的一个典型特征。     

Tribochemistry of a Ti Alloy Under Fretting in Air: Evidence of Titanium Nitride Formation

The present investigation focuses on the tribological transformation occurring on a Ti alloy (Ti17) under fretting in air. Several fretting wear tests were performed on a large scale punch on plane configuration (two types of planes tested: bare Ti6242 and CuNiIn-coated Ti6242) at several temperatures from ambient up to 450 °C. In all the cases, two zones were identified on the scars: a lateral oxidized rim and a highly deformed region at centre. Metallurgical observations revealed similarities with Tribologically Transformed Structure (TTS), previously observed on various Ti alloys. In the framework of this article, careful analyses were conducted (EDX, DRX, XPS, HRTEM and EFTEM) in order to identify the nature and chemistry of this transformed layer. Results demonstrated the formation of a new phase, nanocrystalline, identified as TiO _x N _y . The high content of nitrogen found in the TTS indicated its ability to penetrate inside the contact and react with titanium. At 50 μm under the surface, a FIB preparation enabled the observation in TEM of N-rich lamellae (TiO _x N _y ) in the Ti (α) matrix. Two models were suggested to explain this tribochemical reaction under fretting.     

AZ91D镁合金微动磨损特性研究

采用液压高精度材料试验机考察了平面一球面接触的AZ91D镁合金摩擦副的微动磨损行为，分析了位移幅值、法向载荷和频率等参数对摩擦因数和磨损体积的影响，考察了不同实验条件下的磨斑形貌，并探讨了其磨损机理。结果表明：AZ91D镁合金的微动区域可分为部分滑移区、混合区和滑移区3个区域，粘着磨损、疲劳磨损和磨粒磨损分别是3个区域的主要磨损机制；磨损体积随着位移幅值和法向载荷的增加而增大，但却随着频率的增大而减小。在微动部分滑移区和混合区，摩擦因数随着位移增大迅速增加；在微动滑移区，摩擦因数随法向载荷的增大而减小，而位移幅值和频率对摩擦因数的影响较小。