Tribological Performance of Laser-Textured Polyoxymethylene under Boundary Lubricated Sliding Condition

Micro texturing was fabricated on polyoxymethylene surfaces using laser texturing, and the tribological characteristics were studied. Micro texturing was proven to be very effective in lowering the coefficient of friction, regardless of the texturing depth used in this study. Laser texturing was practical and efficient owing to its fast process time with reasonable machined shapes. An optimum aspect ratio and area density of texturing would exist under the conditions used in this study. Wear of polyoxymethylene was negligible.     

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.     

热处理对石墨填充高岭土基矿物聚合物复合材料摩擦学性能的影响

对20%石墨填充高岭土基矿物聚合物复合材料在不同温度下进行热处理,利用扫描电镜、X射线衍射和红外光谱等表征手段及显微硬度实验、三点弯曲实验,研究了材料的微观结构、机械性能及摩擦学性能与热处理温度之间的关系。结果表明,随热处理温度的提高,材料的微观结构发生较大变化,材料的显微硬度和弯曲强度均呈现先下降后又缓慢上升的趋势;材料经300℃和600℃的高温处理后仍具有较好的摩擦学性能,处理温度较低时,材料的磨损形式以磨粒磨损和粘着磨损为主;处理温度较高时,磨损形式以磨粒磨损和疲劳磨损为主。     

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.     

Tribological Behavior of an Aluminum Matrix Composite with Al4SiC4 Reinforcement under Dry Sliding Condition

In the present research work, an aluminum-based metal matrix composite with in situ Al₄SiC₄ particles has been developed by the incorporation of TiC particles in commercial aluminum melt through a stir-casting method. Microstructure evaluation in correlation to developed hardness and mechanical properties was performed. Furthermore, the dry sliding wear behavior of commercial aluminum and commercial aluminum–5 vol% Al₄SiC₄ composite was investigated at low sliding speed (1 ms^?1) against a hardened EN 31 disk at different loads. The wear mechanism involved adhesion and microcutting–abrasion at lower loads. On the other hand, at higher loads, abrasive wear involving microcutting along with adherent oxide formation was observed. The overall wear rate increased with load in the alloy as well as in the composite. Moreover, the overall wear rate of the composite was lower than that of the commercial aluminum at all applied loads.` The severe wear region at 39.2 N load in the case of the commercial aluminum–5 vol% Al₄SiC₄ composite was found to be delayed up to a longer sliding distance compared to commercial aluminum. The in situ Al₄SiC₄ particles offered resistance to adhesive wear. Accordingly, the commercial aluminum–5 vol% Al₄SiC₄ composite exhibited superior wear resistance compared to the commercial aluminum.     

Tribological Behavior of Composites Based on ZA-27 Alloy Reinforced with Graphite Particles

The objective of this investigation is to assess the influence of graphite reinforcement on tribological behavior of ZA-27 alloy. The composite with 2 wt% of graphite particles was produced by the compocasting procedure. Tribological properties of unreinforced alloy and composite were studied, using block-on-disk tribometer, under dry and lubricated sliding conditions at different specific loads and sliding speeds. The worn surfaces of the samples were examined by the scanning electron microscopy (SEM). The obtained results revealed that ZA-27/graphite composite specimens exhibited significantly lower wear rate and coefficient of friction than the matrix alloy specimens in all the combinations of applied loads (F _n ) and sliding speeds (v) in dry and lubricated tests. The positive tribological effects of graphite reinforcement of ZA-27 in dry sliding tests were provided by the tribo-induced graphite film on the contact surface of composite. In test conditions, characterized by the small graphite content and modest sliding speeds and applied loads, nonuniform tribo-induced graphite films were formed leading to the increase of the friction coefficient and wear rate, with increase of the sliding speed and applied load. In conditions of lubricated sliding, the very fine graphite particles formed in the contact interface mix with the lubricating oil forming the emulsion with improved tribological characteristics. Smeared graphite decreased the negative influence of F _n on tribological response of composites, what is manifested by the mild regime of the boundary lubrication, as well as by realization of the mixed lubrication at lower values of the v/F _n ratio, with respect to the matrix alloy.     

The Effects of Magnetic Treatment on the Tribological Behavior of AISI 1045 Steel under Lubricated Conditions

The mechanical and tribological properties of pulse-magnetized and untreated AISI 1045 steel were studied comparatively. The microhardness and microstructures of treated and untreated steel samples were analyzed to evaluate magnetic treatment effects on the mechanical properties. Dislocation densities were calculated from X-ray diffraction data according to the Williamson-Hall method. Tribological tests were conducted using a ball-on-disk reciprocating friction and wear tester. Scanning electron and energy-dispersive microscopies were used to analyze the morphologies and elements of worn surfaces. Dislocation densities of AISI 1045 steel were found to increase by 16.5% after magnetic treatment. Treated steel performed better under polyalphaolefin (PAO) base oil lubrication with each of five additives, especially when oleic acid was 0.2 and 1.5% (by mass), and the wear scar width and friction coefficient of treated samples were 46.9 and 16.4% lower than those of the untreated samples, respectively. Morphological analyses indicated that micromagnetic fields generated during friction tests not only promoted oxidation of the worn surface and debris but also produced thinner tribofilms that included chemical and adsorbed films.     

The Effect of Applied Load on Tribological Behaviors of Potassium Titanate Whiskers Reinforced PEEK Composites Under Water Lubricated Condition

The tribological behavior of potassium titanate whiskers (PTW) reinforced polyetheretherketone (PEEK) composite has been investigated using the pin-on-disk configuration at different applied loads under water lubricated condition. It was found that the incorporation of the PTW into PEEK would achieve high wear resistance and low friction coefficient at low load. When the applied load increased up to 4 MPa, only the composite filled with 5 wt% PTW showed a significant improvement in the frictional reduction and wear resistance; on the contrary, a rapid increasing of the friction coefficient was observed for the composites of high PTW content. In the meantime, the severe wear loss occurred along with the sharply increasing temperature. This sudden deterioration of the wear resistance should be attributed to the change of the wear mechanism. The main wear mechanism of mild fatigue for the neat PEEK and mild abrasive wear for the 5 wt% PTW filled composite did not alter with the rising of the load. In this case, no transfer film could be detected on the counterpart surface. However, for the high PTW filled composites, the wear mechanism changed from the mild abrasive wear at low applied load to the severe fatigue wear at high load. Large amounts of wear debris were generated by the fatigue-delamination of the composite surface. And then, the debris served as third-body abrasives during the subsequent sliding process and the wear mechanism changed to severe abrasive wear. And unexpectedly, a thick and lumpy transfer film was formed on the counterface.     

Boundary Lubricated Tribology of an Aluminium-Silicon Alloy Sliding Against Steel

We have slid steel pins on aluminium-silicon alloy discs in the boundary lubrication regime in the presence of one drop of oil. We have explored the effect of base oil and additivated engine oil on friction and wear and analyzed the data in terms of the formation of a mechanically mixed layer at the interface and the corrosive action of additive addition.     

Tribological Properties of Phosphor Bronze and Nanocrystalline Nickel Coatings Under PAO + MoDTC and Ionic Liquid Lubricated Condition

The friction and wear properties of phosphor bronze and nanocrystalline nickel coatings were evaluated using a reciprocating ball-on-plates UMT-2MT sliding tester lubricated with ionic liquid and poly-alpha-olefin containing molybdenum dialkyl dithiocarbamate, respectively. The morphologies of the worn surfaces for the phosphor bronze and nanocrystalline nickel coatings were observed using a scanning electron microscope. The chemical states of several typical elements on the worn surfaces were examined by means of X-ray photoelectron spectroscopy. Results show that the phosphor bronze and nanocrystalline nickel coatings exhibited quite different tribological behaviors under different lubricants. Phosphor bronze plate shows higher friction coefficient (0.14) and wear rate (3.2 × 10⁻⁵ mm³/Nm) than nanocrystalline nickel coatings (average friction coefficient is 0.097, wear rate is 1.75 × 10⁻⁶ mm³/Nm) under poly-alpha-olefin containing molybdenum dialkyl dithiocarbamate lubricated conditions. The excellent tribological performance of nanocrystalline nickel coatings under above lubricant can be attributed to the formation of MoS₂ and MoO₃ on the sliding surface. a quite a number of C, O and F products on worn surface of phosphor bronze than NC nickel coatings can improve anti-wear properties while using ionic liquid as lubricant.     

A New Tribological Approach for Lubricated Sliding Contact of Pitted Metallic Curvature Cup

Interest in the development and application of plant-based lubricants for medical use is increasing. This study investigates palm oil lubricants as environmentally friendly and renewable resources to optimize the motion in an ergonomic simulated metal hip prosthesis with modification to the acetabular cup surface. Although metal hip replacements are extensively used, minimizing metal-on-metal friction and wear using safe lubricants requires further investigation. The main physical properties of palm kernel oil and palm fatty acid distillate are considered. The viscosity, wear scar, and coefficient of friction are compared to hyaluronic acid. A modified pin-on-disc tribometer simulates friction and wear on a 28-mm-diameter acetabular cup and microscopy image analysis is used to examine the wear scar. The physical properties of palm oil derivatives reduce friction and wear. In brief, the most significant results of this study include the effect of lubricant and number of pits on wear and friction coefficient. The contribution of this research work is to maintain stability and increase the lifetime of ergonomic metal hip implants.     

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。     

Friction Dependence on Surface Roughness for Castor Oil Lubricated NiTi Alloy Sliding on Steel

Abstract

NiTi alloys are highly resistant to corrosion with hardness and elasticity properties suitable for bearing applications. However, lubrication of this material is still being explored since many commercial lubricants are designed to function through chemical and physical interactions with steel surfaces. Previous studies suggested castor oil as a natural lubricant for NiTi and reported friction coefficients less than 0.01, i.e. superlubricity, when sliding steel against 60NiTi (60wt.%?Ni, 40?wt.%?Ti). Here we explore the robustness of those findings by characterizing the change in friction coefficient as a function of contact pressure and surface roughness. It is found that friction is extremely sensitive to surface roughness, such that ultra-low friction could only be achieved with surfaces having roughness less than tens of nanometers, conditions which may not be achievable in some practical bearing applications.     

Influence of Polymer Filler on Tribological Properties of Thermoplastic Polyurethane Under Oscillating Sliding Conditions Against Cast Iron

The tribological behaviour of unfilled thermoplastic polyurethane (TPU) and a polymer sphere filled (TPUG) thermoplastic polyurethane have been studied under oscillating sliding condition against cast iron as a counterpart. In the case of unfilled TPU, the wear mechanisms are dominated by particle detachment and roll formation. In principle, TPUG also showed a similar wear mechanism as that of unfilled TPU; in addition, particle pull-out and delamination are also observed. Wear volume of TPUG was significantly higher than that for the unfilled TPU and this is attributed to the different material removal processes taking place in the material during sliding. The polymer spheres as a filler material deteriorated the wear resistance of TPU because of improper adhesion and bonding of filler in the TPU matrix and therefore it contributed to more wear. In case of TPU the friction behaviour was strongly dependant on the temperature and surface roughness of the counter body. The results showed that below the glass transition temperature higher friction values are observed with higher counter body surface roughness. However, above the glass transition temperature, higher friction values are observed with a smoother surface roughness of the counter body. In case of TPUG, the friction behaviour was not significantly dependent on surface roughness of the counter body.     

PEEK450 FC30与SiC陶瓷在海水润滑下的摩擦磨损特性研究

碳纤维增强聚醚醚酮PEEK450 FC30与工程陶瓷SiC软硬组合作为海水柱塞泵关键摩擦副备选材料,利用MCF 10摩擦磨损试验机对其在海水润滑下的摩擦磨损特性进行试验研究,探讨接触压力、滑动转速对材料磨损率和摩擦系数的影响规律。试验结果表明：在一定范围内的滑动速度、接触压力下,该摩擦副呈现出较小的磨损率和摩擦系数。当滑动速度在0.5~1.5 m/s之间,接触压力为1.33 MPa时,磨损率最小。通过扫描电子显微镜观察摩擦副磨损表层发现,在海水润滑下,SiC磨损并不明显,而PEEK450 FC30的磨损主要是以塑性涂抹为特征的粘着和SiC表面粗糙峰引起的机械犁耕。研究结果对水液压元件的选材具有十分重要的指导作用。     

铜镍锡合金干滑动磨损行为研究

大型装备上的铜镍锡合金工件常常工作在润滑不足或者无润滑的工况条件下,因此有必要研究铜镍锡材料在干摩擦下的性能。采用CEF-I型销-盘式磨损试验机对铜镍锡合金在不同载荷与转速条件下进行干滑动摩擦磨损试验,采用扫面电子显微镜、能谱仪和轮廓检测仪对磨损表面进行检测,研究铜镍锡合金的干滑动磨损行为,并探讨其磨损机制。结果表明：在转速一定时,平均摩擦因数随载荷增大总体呈波动下降趋势,铜镍锡合金试件磨损量先缓慢增加,在较高载荷下快速增加;在载荷一定时,平均摩擦因数随转速增大先增大后减小,铜镍锡合金试件磨损量总体呈先减小后增大趋势;随着载荷的增大,铜镍锡合金的磨损机制由轻微黏着和剥层磨损到明显的黏着和剥层磨损,再到严重的黏着和疲劳磨损,随着转速的增大,铜镍锡合金的磨损机制由磨粒磨损转变为黏着磨损再到剥层磨损。在较低载荷下,随着转速的增大,铜镍锡合金摩擦磨损性能保持很好的稳定性,因此铜镍锡合金适用在高转速较低载荷的干摩擦工况下。     

不同热处理条件下45#钢与40Cr钢摩擦学性能比较

针对机械行业中45^#钢和40Cr钢使用混乱的状况,着眼于2种钢材的基础性能,从45^#钢和40Cr钢的耐磨性能入手,对二者在不同热处理条件下的摩擦学性能进行了研究和比较。结果表明：在调质处理状态下,45^#钢和40Cr钢与GCr15钢对磨时的摩擦因数基本相同,但45^#钢的磨损量要低于40Cr钢,在强度符合条件,工件形状不太复杂的情况下,建议采用45^#钢;在淬火加低温回火处理状态下,45^#钢的摩擦因数与磨损量均高于40Cr钢的摩擦因数。在强调工件的强度和耐磨性时,建议采用40Cr钢;在高频淬火加低温回火处理和在离子氮化处理状态下,45^#钢的摩擦因数与磨损量均接近于40Cr钢的摩擦因数与磨损量,在保证强度的情况下,可以考虑采用45^#钢以降低生产成本。     

Influence of the Wetting Properties of Liquids on the Tribological Behavior of Selected Sliding Materials in Mechanical Seals

Theoretical investigations are carried out for a plain journal bearing considering the influence of thermal effects on non-Newtonian lubrication. With reasonable assumptions, the steady state and dynamic characteristics are presented using a thermohydrodynamic analysis of a bearing lubricated by a nonlinear, i.e., cubic, fluid model.

Experiments are conducted on a rig to study the steady state and dynamic performance of a full journal bearing with different types of non-Newtonian lubricants. Experiments include the measurements of eccentricity ratio, critical speed, and stability limit.

The theoretical investigation reveals that the interaction of the non-Newtonian effect and the thermohydrodynamic effect is strong for friction, and the interaction effect is negligible in the case of eccentricity ratio, attitude angle, and lubricant flow rate. Further, for relatively high values of non-Newtonian parameter, α_n , the effect due to the non-Newtonian parameter is not negligible.     

导热能力对TC4合金高速干摩擦及其热行为的影响

采用具有较好导热性能的紫铜与TC4合金机械镶嵌，组成的销试样与纯TCA合金销试样的摩擦磨损特性及热行为特性进行对比研究。研究结果表明：随着摩擦功的增加，使用紫铜强化导热的TCA-紫铜组合销试样与纯TCA合金销试样的摩擦表面温度整体均为上升趋势，但是TC4-紫铜组合销试样的摩擦表面温度与纯TC4合金销试样相比有大幅度的降低，纯TC4合金销试样的表面温度在升高到一定程度以后由于相变吸收热量，其表面温度出现降低的趋势。使用紫铜强化导热后，摩擦副的摩擦因数有所提高，材料的耐磨性也有一定程度的提高。     

Tribological Behavior of Ceramics at High Sliding Speeds in Steam

Three sets of tests were conducted using a pin-on-disk tribometer to determine the tribological behavior of ceramics at high sliding speeds in steam. In the first set, the speed was increased from 4000rpm to 10,000rpm in 1000 rpm increments. Constant rotational speeds of 4000rpm, 6000rpm, 8000 rpm and 10,000 rpm were used in the second test series. In the third series of tests, the rotational speed was slowly increased to 10,000rpm and allowed to coast down to zero. While the coefficient of friction for silicon nitride/YTZP pair varied between 0.2 and 0.4 without a clear pattern as the speed was increased in the first two test series, it decreased from about 0.6 to 0.2 when the speed was raised to 10,000 rpm in the third test series. This behavior is attributed to the general phenomena of powder lubrication as the wear debris provides an interfacial layer leading to reduced friction at high speeds. The coefficient of friction for silicon nitride/silicon carbide pair was substantially reduced to about 0.02 as the speed was raised. The low coefficient of friction, however, increased to a high level as the speed was further increased. The drop in friction is explained based on analysis of elasto-hydrodynamic lubrication assuming that a water film containing solid particles exists at the interface. Several possible mechanisms are suggested for the transition to a higher friction as the speed is raised: thermal effects at high flash temperatures, low residence times (for water adsorption on surface), collapse of the lubricant film and starvation effects.