复合工艺制备的表面微凹坑织构的摩擦性能研究

在构建的激光电化学复合微加工系统上,采用皮秒脉冲激光辐照与电解刻蚀复合加工方法在7075铝合金表面制备出不同尺寸的阵列凹坑微织构。采用共聚焦显微镜观测复合加工织构试样表面形貌,采用MFT-5000型RTEC摩擦磨损试验机研究润滑条件下凹坑织构的摩擦学性能,并探讨直径、深度、面积密度对减摩性能的影响。结果表明:复合加工工艺制备的表面微织构具有良好的表面形貌;润滑条件下材料表面的凹坑型织构能显著改善其摩擦学性能,相比光滑表面最高可降低摩擦因数30%;在实验参数范围内,凹坑的直径与面积密度对材料表面摩擦性能影响较大,凹坑深度对摩擦性能影响较小。     

纳米固体润滑颗粒对微织构表面摩擦学性能的影响研究

基于RTEC-MFT-5000型多功能磨损试验机,研究了纳米固体润滑颗粒作为润滑油添加剂对微凹坑织构表面摩擦学性能的影响。在研究中,应用NanoFocus共聚焦显微镜观测试样表面微织构形貌,获取磨痕处二维截面轮廓图。借助扫描电子显微镜和能谱仪,对磨损区域微凹坑形貌及磨痕部位微凹坑内外的元素成分进行分析。研究结果表明,添加纳米固体润滑颗粒的润滑油,在不同工况条件下均具有较优的减摩特性,固体润滑颗粒作为添加剂有助于在磨损区域形成一层固体润滑膜,减小摩擦副之间的摩擦因数,提高耐磨性能。含有纳米二硫化钼固体颗粒添加剂的润滑油,其减摩抗磨效果优于含有纳米石墨固体颗粒添加剂的润滑油。表面微织构技术与纳米固体润滑颗粒添加剂相结合,可以表现出更为优异的协同润滑效果。     

人工髋关节球形凹坑微织构表面摩擦学性能研究*

为改善人工髋关节表面的摩擦学性能,在人工髋关节表面设计球形凹坑微织构;建立人工髋关节微织构表面的流体动压润滑模型,利用CFD软件ANSYS Fluent对微织构表面流体动压进行数值分析,得到摩擦副表面相对滑动时产生的油膜平均承载力以及摩擦因数,并分析表面微织构参数对摩擦学性能的影响。结果表明:在给定的织构参数范围内,平均承载力随深径比的增加呈现出先降低后升高再降低的趋势,随面积密度的增加呈先升高再降低的趋势;摩擦因数随深径比和面积密度增加的变化趋势与平均承载力相反;织构的最优参数分别为深径比0.06,面积密度25%。因此,在人工髋关节表面设置合适参数的球形凹坑微织构可以提高油膜平均承载力和降低摩擦因数,从而起到减小关节的摩擦磨损提高人工关节使用寿命的作用。     

润滑介质对织构化表面摩擦学性能影响的实验研究

采用纳秒激光烧蚀技术在铍青铜盘试样表面加工3种不同参数圆形微凹坑织构,选用石油装备中常用的低黏度L-CKD150润滑油和高黏度复合锂基润滑脂为润滑介质,开展不同润滑环境下销-盘摩擦学实验,对比分析L-CKD150润滑油和复合锂基润滑脂对织构表面摩擦磨损性能的影响差异。实验结果表明:2种不同润滑环境下,合理参数织构均可有效提高表面润滑性能、减少摩擦磨损;润滑介质对织构表面摩擦磨损性能的影响差异与接触压力有关,接触压力较低时,L-CKD150润滑油润滑性能优于复合锂基润滑脂,接触压力较高时则复合锂基润滑脂润滑性能更优;相同工况下,相比于L-CKD150润滑油润滑,复合锂基润滑脂润滑时最优织构直径更大。     

激光微织构表面黏结型固体润滑膜性能研究

采用声光调Q二极管泵浦Nd∶YAG激光器在45#钢表面进行织构化处理,并填充不同的黏结MoS2基复合固体润滑剂;在销盘线接触的摩擦磨损试验机上研究含不同配比复合固体润滑剂的织构表面的滚动摩擦性能。研究结果表明:织构表面填充黏接型复合固体润滑剂改善了其摩擦性能,其中填充含质量分数50%MoS2复合固体润滑剂的织构表面的摩擦因数最低;在线接触滚动过程中,黏结MoS2基复合固体润滑剂织构表面的摩擦因数均随着载荷和转速的增大而减小,这是因为高速重载促进了转移膜在对偶面的形成,该转移膜显示出良好的减摩性能。     

组合型微织构化铝合金表面的摩擦学性能研究

为改善铝合金的摩擦学性能,运用有限元方法对单一方形凹坑、条形凹槽、方形凹坑和条形凹槽组合3种不同形貌织构摩擦副间润滑油膜承载能力进行仿真分析,并探究不同织构尺寸对油膜承载能力的影响。仿真结果表明：方形凹坑和条形凹槽组合织构润滑油膜承载能力最佳。采用脉冲Nd:YAG激光器在铝合金试件表面加工出具有规则形貌的方形凹坑和条形凹槽组合的织构阵列,借助CFT-I型高速往复摩擦磨损试验机进行摩擦试验,研究织构几何尺寸对摩擦副接触面间摩擦学性能的影响规律,并利用超景深显微系统对试件磨损表面的形貌进行观测。试验结果表明：组合织构化表面的平均摩擦因数与无织构表面相比明显减小,且波动幅度较小;当织构尺寸为80μm时,织构表面的摩擦因数最小,且试验得到的基体表面磨痕深度随织构尺寸的变化规律,与仿真计算得到的润滑油膜升力系数的变化规律相吻合,为微织构参数设计提供了一定的理论依据。     

粗糙度对微凹坑织构化表面摩擦学性能的影响

为了研究表面初始粗糙度和微凹坑织构共存时的表面摩擦性能,采用激光微织构加工技术在不同粗糙度的试样表面上加工出不同几何形貌的微凹坑织构,在MMW-1A摩擦试验机上进行正交摩擦学性能试验。结果表明:在混合润滑区域,表面粗糙度对摩擦性能的影响最为明显,未织构表面越粗糙,摩擦因数越小;存在合适的微凹坑几何参数与表面初始粗糙度值组合,使得织构化粗糙表面的摩擦性能达到最优;表面初始粗糙度对织构化粗糙表面摩擦性能的影响最为重要,其次为微凹坑的面积占有率,最后为凹坑深度,并且织构几何参数与粗糙度之间的交互作用对摩擦性能的影响也是不能忽视的。     

GCr15钢微织构表面固体润滑性能研究

为研究不同表面处理方式对PTFE/GCr15钢配副表面摩擦学性能的影响,采用Nd:YAG纳秒激光器对GCr15轴承钢下试样表面进行激光织构加工,并以纳米MoS_2固体润滑剂作为润滑介质,以黏结有PTFE自润滑衬垫的圆柱销作为上试样进行对摩试验。研究发现:PTFE自润滑衬垫与微织构GCr15摩擦副在干摩擦条件下摩擦因数较低,仅为0.137,而在纳米MoS_2固体润滑剂润滑条件下,其摩擦因数进一步下降为0.123,且波动较小。通过EDS分析表明,表面微织构、聚四氟乙烯衬垫与纳米MoS_2润滑介质三者具有协同润滑减摩效应,可摩擦副表面生成一层由PTFE与纳米MoS_2材料组成的致密、平滑复合润滑膜,有效改善对摩副之间的润滑特性。研究表明,通过表面激光织构技术与固体自润滑技术(添加纳米MoS_2)的有效集成融合,可进一步改善PTFE/GCr15钢配副的润滑性能。     

激光微造型表面固体润滑性能研究

采用声光调Q二极管泵浦固体光源(DPSS)Nd:YAG激光器,在45#钢试样表面进行表面微造型加工。以聚酰亚胺(PI)和二硫化钼(MoS2)复合固体润滑材料作为固体润滑剂,通过两步加温固化黏结工艺成功制备微造型固体润滑试样。在MMW-1A型摩擦磨损试验机上进行光滑无润滑试样、光滑表面固体润滑试样和微造型固体润滑试样的摩擦性能对比试验,以及微造型固体润滑试样在不同转速和压力下的摩擦性能试验。结果表明,在经过激光加工的微凹坑中填充复合固体润滑材料的试样,在摩擦过程中微凹坑中填充的固体润滑材料能有效转移到在摩擦表面,补充消耗掉的润滑材料,因而表现出更好的摩擦学性能。     

表面微织构影响点接触润滑摩擦性能的实验研究

针对球-盘高副点接触开展微织构表面摩擦学性能实验研究。采用激光工艺在试样表面上加工出具有一定形状、深度和面积比的矩形微织构,采用三维表面形貌仪测量微织构的形貌特征,在摩擦磨损实验机上进行摩擦学实验,研究往复运动模式下微织构深度、间距等参数对球-盘点接触润滑摩擦性能的影响。结果表明:较浅的微织构具有相对较小的摩擦因数;较高频率下微织构表现出较好的润滑和减摩效果;沿运动方向的微织构间距增大,摩擦因数逐渐降低,超过Hertz接触直径之后,摩擦因数变化不明显;垂直于运动方向微织构边长增大,摩擦因数呈现先减小后增大的变化趋势。     

Tribological Properties of Lubricating Films on the Al-Si Alloy Surface via Laser Surface Texturing

Dimpled textures were prepared by using a pulse solid laser on the surface of Al-Si alloy. The combination of laser surface texturing (LST) and MoS₂ solid lubricant as well as their tribological properties were investigated in this article. The obtained friction and wear data were critically analyzed to investigate how the parameters of texture influence the tribological performance of Al-Si alloy. Furthermore, morphological investigations of the transfer layers on the worn surfaces were performed and the wear mechanisms are discussed. The results show that the combination of LST and solid lubricant improves the tribological characteristics of Al-Si alloy. The friction coefficient of Al-Si alloy: steel friction pairs can be reduced to 0.15 under dry friction. The lubrication mechanism is attributed to a synergetic effect of providing solid lubricant and traps wear debris in the dimples. It was found that the optimum density of structure was 37% for excellent tribological properties.     

Friction and Wear Properties of MoS<Subscript>2</Subscript>-Overcoated Laser Surface-Textured Silver-Containing Nickel-Based Alloy at Elevated Temperatures

The solid lubricant that is coated on a flat surface is easily removed during friction. Surface texture dimples, which act as reservoirs of solid lubricant, can prolong the wear life of solid lubricant films. We textured silver-containing nickel-based alloys by a pulse laser and filled the micro-dimples with molybdenum disulfide powders. The tribological properties of the alloys were tested by rubbing against alloyed steel on a ring-on-disk tribometer at temperatures ranging from room temperature to 600°C . After laser surface texturing, the friction coefficients of the silver-containing nickel-based alloy smeared with molybdenum disulfide powders were reduced at temperatures ranging from room temperature to 400°C. With increasing dimple density, the wear life of the MoS₂ film increased while the wear rate of the nickel-based alloy decreased. The wear life of the textured surface with a dimple density of 11.2% exceeded 10,000 m at room temperature. We conclude that molybdenum disulfide and its oxides stored in the micro-dimples play a role in lubrication at room temperature and high temperatures, respectively.     

六方氮化硼负载纳米铜润滑添加剂的制备及其摩擦学性能研究

采用水热吸附及热解还原制备六方氮化硼负载纳米铜复合润滑添加剂(Cu/h-BN),利用透射电镜(TEM)、X射线衍射仪(XRD)、热重分析仪(TGA)以及红外光谱仪(FT-IR)对样品进行表征.将纳米润滑添加剂分散到聚α-烯烃(PAO10)中,采用球盘摩擦试验考察其摩擦学性能.采用扫描电子显微镜(SEM)对典型的磨痕进行...     

Investigation of the tribological properties of the different textured DLC coatings under reciprocating lubricated conditions

In this study, we propose the use of laser surface texturing methods to improve the wear resistance of diamond-like-carbon (DLC) coatings. First, the application of dimples perpendicular to an engineering surface is introduced by using laser in a controlled manner. The solid DLC lubricant is subsequently deposited on the textured surface using the magnetron sputtering technique. In the experiments, the dimple densities were varied from 0 to 30%, and the dimple diameters were varied from 40 to 300 μm. The effect of the geometric parameters on the wear performance was studied using a reciprocating sliding-wear tester under oil lubrication conditions. The results showed that the DLC coatings with the appropriate dimple density (10%) and diameter (∼100 μm) demonstrated an obvious improvement in terms of the friction coefficient and wear rate compared with that of the un-textured DLC coatings. The experimental treatment produced respective reductions of 20% in friction and nearly 52% reduction of wear rate. This improvement could be explained by the action of reservoirs that enhance lubricant retention and trap the wear particles during sliding motions. In addition, the relationship between the dimple diameter, the contact width ratio and the wear performance is discussed.     

The study of tribological properties of laser‐textured surface of 2024 aluminium alloy under boundary lubrication

The tribological property of aluminium alloy is critical for its reliable operation in practical applications. In this paper, the tribological performance of laser‐textured 2024 aluminium alloy is studied in unidirectional sliding tests under boundary lubrication. The dimples were produced on the aluminium alloy surface by using a pulse Nd : YAG laser. The topographical microstructures of these laser‐induced textures were characterised by optical and scanning electron microscopy. In comparison with untextured surfaces, a significant improvement in friction behaviour was observed for the textured surfaces. The influences of dimples density on the tribological properties were investigated. Two types of oil with different viscosities were evaluated as lubricants. It was found that the beneficial effects of laser surface texturing are more pronounced at higher speed and load with higher viscosity oil. The optimum dimples density of 8.5% was found to have a lower friction coefficient. On basis of the experimental results, the mechanism of friction reduction and anti‐wear is proposed. Copyright © 2012 John Wiley & Sons, Ltd.     

Surface Engineering Design of Alumina/Molybdenum Fibrous Monolithic Ceramic to Achieve Excellent Lubrication in a High Vacuum Environment

Al₂O₃/Mo fibrous monolithic ceramics are potential candidates for space applications because of their excellent mechanical properties and low density. This study aims at achieving low friction and long life of this material in a high vacuum environment. Three-dimensional composite-lubricating layers were fabricated by considering texture pattern as storage dimples and MoS₂ synthesized via hydrothermal method as lubricant. The tribological properties were studied sliding against Si₃N₄ ceramic and GCr15 bearing steel balls under high vacuum condition. Results showed that the lubricating properties of the Al₂O₃/Mo fibrous monolithic ceramics were improved greatly by the micro-texture and MoS₂ solid lubricant; the friction coefficients were as low as approximately 0.08 and 0.04, respectively, when Si₃N₄ ceramic and GCr15 bearing steel balls acted as the pairing materials. It was also demonstrated that the low friction coefficient can be realized with various normal loads and sliding speeds, indicating the composite-lubricating layers have good adaptation of working conditions. This excellent performance of the material is mainly because of MoS₂ stored in dimples can be easily dragged onto the friction surface to form lubricating and transferring films during the friction process. This work is an extension of studies that were previously published in Tribology Letters journal.     

纳米粗糙间隙中季戊四醇四酯的薄膜润滑行为

采用分子动力学模拟方法建立光滑和粗糙2种固体壁面结构，研究季戊四醇四酯润滑剂在不同压力、薄膜厚度下，在恒定剪切速度和温度下的薄膜润滑行为。分析壁面间润滑薄膜的密度分布，以及剪切过程中润滑剂的速度分布。输出固体壁面在x向和z向的力学响应，并计算摩擦因数。结果表明：表面纳米结构降低了润滑薄膜的厚度，减弱了润滑薄膜分层现象；当润滑薄膜厚度较大时，V形纳米沟槽有助于减小薄膜润滑系统的摩擦因数；润滑薄膜厚度较小时，V形纳米沟槽表面润滑状态容易从流体润滑转变到边界润滑状态，摩擦因数增大。     

Tribological Behavior of Tin-Based Babbitt Alloy Lubricated by Seawater

In this article, the tribological behaviors of tin-based Babbitt alloy ZChSnSb 8–8 sliding against AISI 302 stainless steel lubricated by seawater were investigated. The results indicated that the friction coefficient decreases with increasing load and sliding speed, and the wear rate increases slightly with load but decreases with sliding speed. The low friction coefficient and wear rate are attributed to the unique “concrete structure” and seawater. As a lubrication medium, seawater has lubricating, cooling, and corrosive effects on the sliding couple.