纳米润滑添加剂的摩擦学特性研究

纳米金属铜粒子粒度难以控制,其在润滑油中的分散性和稳定性也存在不少问题,为此,采用机械化学法在QM1SP04高能行星球磨机上制备出了铜颗粒粒径在15～60 nm之间的纳米铜浆,并与润滑基础油N68混合搅拌、沉淀后,获得了油溶性良好的纳米润滑油添加剂NT-1.用XP销-盘摩擦磨损试验机和四球摩擦试验机考察了NT-1添加剂的摩擦学性能,结果表明:添加NT-1纳米添加剂的N68润滑油比未添加时总磨损量减小了135%,出现了负磨损现象;将NT-1添加到长城15W/40SE汽油机油中,其PB值增加了26.0%,摩擦系数降低了11.1%,表现出良好的减摩性能和自修复功能.同时,将NT-1添加剂与3种有机钼盐配对试验,发现加入2%的硫化硫磷酸钼使基础油的承载能力提高了98.3%,其原因可能是有机钼与纳米铜之间存在协同作用.     

铝管退火表面形成残焦的原因剖析

通过铝管拉拔试验及加热失重试验，剖析了不同的润滑剂在不同温度下形成残焦的原因，并由热重分析得到了证实。进而优选出一种新型润滑剂为Ｘ润滑油。     

防泵轴头甩油新结构的研制开发

通过对泵原结构轴头甩油原因分析，指出了漏油原因。研制出防止轴头甩油的离心密封和螺旋密封组合的新结构。利用离心密封作为初步节流阻漏密封，利用螺旋密封作二次密封。这种改进方法只需改造轴承箱压盖和轴承锁紧螺母，对原结构改动很小，即能满足密封要求，又能适应原结构可利用空间小的限制。实际使用效果良好，有普遍推广价值。     

几种润滑剂对温压工艺的影响

温压工艺的技术关键之一是润滑剂 ,其主要作用是减小压制过程中粉末颗粒与模壁之间及粉末颗粒之间的摩擦 ,增大有效压力 ,从而使压坯密度相对于传统压制工艺明显提高。不同润滑剂的润滑效果不同 ,最佳压制温度也有差异。本文选用 3种不同的润滑剂 ,在不同温度、压力条件下采用温压技术制备铁基粉末冶金材料 ,研究了压坯密度的变化规律和它的力学性能 ,探讨了润滑剂对温压工艺的影响     

粉末冶金静电模壁润滑中润滑剂粉末的荷电影响因素

粉末冶金静电模壁润滑是一种新颖的润滑方式。本文通过试验研究了在粉末冶金静电模壁润滑技术中润滑剂粉末荷电情况的各种影响因素，包括润滑剂种类、电压和输粉管长度，并对其进行了初步理论分析。结果表明：硬脂酸锌荷电性能最好，不存在荷电阀门值(能使润滑剂粉末荷电的最低电压)，而EBS蜡、W-special蜡及硬脂酸锌和EBS蜡的各种混合粉均存在一荷电阀门值；另外，输粉管长度越短，EBS蜡的荷电阀门值越高，荷电性能越差。     

Super-low friction of MoS2 coatings in various environments

The ultra-low friction coefficient (typically in the 10⁻² range) of MoS₂-based coatings is generally associated with the friction-induced orientation of ‘easy-shear’ planes of the lamellar structure parallel to the sliding direction, particularly in the absence of environmental reactive gases and with moderate normal loads. We used and AES/XPS ultra-high vacuum tribometer coupled to a preparation chamber, thus allowing the deposition of oxygen-free MoS₂ PVD coatings and the performance of friction tests in various controlled atmospheres. Friction of oxygen-free stoichiometric MoS₂ coatings deposited on AISI 52100 steel was studied in ultra-high vacuum (UHV: 5 × 10⁻⁸ Pa), high vacuum (HV: 10⁻³ Pa), dry nitrogen (10⁵ Pa) and ambient air (10⁵ Pa). ‘Super-low’ friction coefficients below 0.004 were recorded in UHV and dry nitrogen, corresponding to a calculated interfacial shear strength in the range of 1 MPa, about ten times lower than for standard coatings. Low friction coefficients of about 0.013–0.015 were recorded in HV, with interfacial shear strength in the range of 5 MPa. Friction in ambient air leads to higher friction coefficients in the range of 0.2. Surface analysis performed inside the wear scars by Auger electron spectroscopy shows no trace of contaminant, except after friction in ambient air where oxygen and carbon contaminants are observed. In the light of already published results, the ‘super-low’ friction behaviour (10⁻³ range) can be attributed to superlubricity, obtained for a particular combination of cystallographic orientation and the absence of contaminants, leading to a considerable decrease in the interfacial shear strength.     

Lubricant Spin-Off from Magnetic Recording Disks

As the rotation rate of magnetic recording disks increases over the next few years, lubricant spin-off from the disk surface may be significant. Lubricant thickness was measured as a function of spin time at 10000 rpm on typical carbon overcoated magnetic recording disks initially lubricated with 10–135 Å of perfluoropolyether Zdol. The viscosity of the lubricant film increased as the film thickness decreased with spin time. Lubricant spin-off in response to air shear stress on the free surface was approximately described by viscous flow. The rate of lubricant removal by evaporation was compared to the spin-off removal rate in films between 10 and 50 Å thick. Dispersion interaction and chemisorption are expected to retain a molecularly thin film of lubricant on the disk surface.     

Effects of lubricant additives on the performance of hydrodynamically lubricated journal bearings

A non-Newtonian rheological model to investigate theoretically the effects of lubricant additives on the steady state performance of hydrodynamically lubricated finite journal bearings is introduced. In this model, the non-Newtonian behavior resulting from blending the lubricant with polymer additives is simulated by Stokes couple stress fluid model. The formed boundary layer at the bearing surface is described through the use of a hypothetical porous medium layer that adheres to the bearing surface. The Brinkman-extended Darcy equations are utilized to model the flow in the porous region. A stress jump boundary condition is applied at the porous media/fluid film interface. A modified form of the Reynolds equation is derived and solved numerically using a finite difference scheme. The effects of bearing geometry, and non-Newtonian behavior of the lubricant on the steady-state performance characteristics such as pressure distribution, load carrying capacity, side leakage flow, and coefficient of friction are presented and discussed. The results showed that lubricant additives significantly increase the load carrying capacity and reduce both the coefficient of friction and the side leakage as compared to the Newtonian lubricants.     

头/盘界面对润滑剂转移行为及分布的影响

为进一步提高磁头飞行的稳定性,增加硬盘存储容量,采用分子动力学方法研究磁头磁盘接触条件下盘片上类金刚石薄膜(DLC)层粗糙度、DLC表层官能团比例及单个润滑剂分子中羟基数对润滑剂转移行为及润滑剂在盘片表面分布的影响.研究结果表明:降低DLC层粗糙度,增加DLC表层官能团比例都将降低磁头磁盘间的润滑剂转移量;当磁盘表面存在物理吸附态的润滑剂分子时,增加单个润滑剂分子中的羟基数也可降低润滑剂转移量;但降低DLC层粗糙度或同时增加DLC表层官能团的比例和单个润滑剂中羟基数会增加润滑剂在盘片表面堆积的高度,进而降低磁头飞行稳定性.综合考虑润滑剂转移量和润滑剂在磁盘表面堆积厚度对磁头飞行稳定性的影响,DLC层粗糙度应降低至约0.07 nm,DLC表层官能团比例增至约80%,单个润滑剂分子中的羟基数量应少于8个.     

Performance analysis of a fully textured hybrid circular thrust pad bearing system operating with non-Newtonian lubricant

The present paper deals with the theoretical investigation of the influence of dimple geometry on fully textured hybrid thrust pad bearing and operating with non-Newtonian lubricant. The modified Reynolds equation which governs the flow of non-Newtonian lubricant in the clearance space has been solved using Finite Element Method. The simulated results indicate that the values of load carrying capacity, frictional power loss, maximum pressure and fluid film stiffness coefficient are significantly affected by the behavior of lubricant. The results presented in the study are expected to aid in determining the optimum value of dimple diameter and depth for the optimum bearing performance.