Friction and wear properties of rice husk ceramics under dry condition

The friction and wear behaviors of rice husk (RH) ceramics, prepared by carbonizing the mixture of rice husk and phenol resin at 900 °C in N₂ gas environment, sliding against high carbon chromium steel (JIS SUJ2), austenitic stainless steel (JIS SUS304), and Al₂O₃ under dry condition were investigated using a ball-on-disk tribometer. The test results show that the friction coefficient of RH ceramics takes very low values 0.05–0.08 and 0.06–0.11 sliding against SUJ2 and SUS304, respectively, and much higher values around 0.14–0.23 against Al₂O₃. It was also shown that SUJ2 provides the lowest specific wear rate values below 10⁻⁹ mm²/N, while, those of SUS304 and Al₂O₃ mostly stayed between 10⁻⁹ to 10⁻⁸ mm²/N range. The worn surfaces of counterparts were observed with optical microscopy and analyzed using cross-sectional transmission electron microscopy with energy dispersive X-ray spectroscopy and electron diffraction. It was suggested that the tribological behaviors of RH ceramics are closely related with the formation of a transferred film, consisted of amorphous silica and carbon particles, on a counterpart surface. The transferred film was formed readily on SUJ2 balls, whereas for SUS304 the presence of the film was subject of the sliding conditions. Moreover, formation of the transferred film could not be detected on Al₂O₃ counterparts.     

Potential-Controlled Boundary Lubrication of Stainless Steels in Non-aqueous Sodium Dodecyl Sulfate Solutions

In aqueous solutions, sodium dodecyl sulfate (SDS) surfactant can form a boundary film on metal surfaces to provide lubrication for sliding surfaces in contact. Previous studies have demonstrated that the boundary lubrication of SDS film can be inhibited or enhanced substantially by changing the surface potential of the rubbing metal surfaces. In this study, the SDS surfactant was added to a non-aqueous base fluid, propylene carbonate (PC), and the boundary lubrication behaviors of the solution for stainless steels were investigated under different potential conditions. Friction measurement, electrochemical impedance spectroscopy, cyclic voltammetry, and electrochemical quartz crystal microbalance techniques were employed to investigate the lubricating performance and adsorption film of the sodium dodecyl sulfate (SDS) film on two kinds of steels (AISI 316L, AISI 440C) in propylene carbonate (PC) solution. Similar to aqueous SDS solutions, the lubricating performance of the SDS/PC solution depends upon the electrode potential within the potential range from ?1.5 to +1.5 V versus Ag/AgCl, which suggests the potential-dependent reversible change in the adsorbed film. When the potential is positive, both friction and wear of the tested stainless steels are relatively lower due to the presence of the adsorbed SDS film. As the potential is shifted to the negative regime, the DS chains in the adsorbed film are replaced by the PC molecules gradually, and friction coefficient increases by 100 % or more, depending on the load condition and the hardness of the stainless steels.     

Frictional Voltammetry with Copper

This paper presents an experimental study correlating frictional behavior with in situ voltammetry for a unidirectional sliding contact between a hemispherical tipped alumina probe and a flat rotating copper counterface (maximum Hertzian contact pressure of 68 MPa and sliding speed of 10 mm/s). The contact was immersed in an aqueous 0.1 M Na₂CO₃ solution (pH ∼11) where the copper counterface acted as the working electrode in a potentiostat controlled three-electrode cell; a coiled Pt wire was used as the counter electrode and a saturated calomel electrode (SCE) as the reference. Clear and reproducible trends were found between friction coefficient and published data suggesting the onset of particular redox reactions, graphically presented in a frictional voltammetry plot. At anodic potentials primarily associated with the formation of copper(I) oxide (Cu₂O) (V vs SCE ∼−0.25), the measured friction coefficient was in the range μ ∼0.4–0.5. At cathodic potentials primarily associated with the formation of CuO, Cu(OH)₂, and CuCO₃ (V vs SCE ∼−0.10), the friction coefficient transitions to the range μ ∼0.7–1.0. At sustained cathodic potentials associated with reduction of the native copper oxide, Cu₂O, (V vs SCE ∼−0.65), the friction coefficient is observed to fluctuate between μ ∼0.2 and 0.5, arguably a result of exposure of bare copper due to non-uniform reduction (fractional coverage) of Cu₂O.     

Experimental Evaluation of Friction and Wear Properties of Solid Lubricant Coatings on SUS440C Steel in Liquid Nitrogen

The friction and wear properties of the prevailing different solid lubricant coatings (Ion-plated Au, Ion-plated Ag and RF-sputtered PTFE on SUS440C stainless steel) used in the bearings of high-speed cryogenic-turbo-pumps of liquid rocket engines were experimentally evaluated in liquid nitrogen immersed conditions. Also the above experiments were carried out with two newly proposed solid lubricant coatings of sputter-ion-plated MoSTi and a new ion-plated Pb on SUS440C stainless steel. The friction coefficient and wear rates of the coatings of ion-plated Au, ion-plated Ag, RF-sputtered PTFE, the new ion-plated Pb and MoS₂Ti-SIP (with coating thickness of 0.7±0.1 μm) on SUS440C steel against SUS440C stainless steel ball in liquid nitrogen were compared. Worn surfaces were examined microscopically with a microscope and a profilometer for understanding the mechanisms of friction and wear and transfer film lubrication in liquid nitrogen. It is found that the newly proposed solid lubricant coatings are showing promising results for their use in liquid nitrogen immersed conditions. The sputter-ion-plated MoSTi coating on SUS 440C steel shows a minimum value of friction coefficient (μ=0.015) and wear rate (w_c=0.56 × 10⁻⁶ mm³/N m ) in liquid nitrogen.     

Ultra-High Tribological Performance of Magnetron Sputtered a-C:H Films in Sand-Dust Environment

The hydrogenated amorphous carbon (a-C:H) films were prepared on AISI 440C steel substrates using a RF magnetron sputtering graphite target in the CH₄ and Ar mixture atmosphere. The friction and wear behavior of a-C:H films were comparatively investigated by pin-on-disc tester under dry sliding and simulated sand-dust wear conditions. In addition, the effects of applied load, amount of sand and sand particle sizes on the tribological performance of a-C:H films were systemically studied. Results show that a-C:H films exhibited ultra-high tribological performance with low friction coefficient and ultra-low wear rate under sand-dust environments. It is very interesting to observe that the friction coefficient of a-C:H film under sand-dust conditions was relatively lower when compared with dry sliding condition, and the wear rate under sand-dust conditions kept at the same order of magnitude (×10⁻¹⁹ m³/N m) with the increase of applied load and particle size as a comparison with the dry sliding condition. Based on the formation of “ridge” layer (composite transfer layer), a transfer layer-hardening composite model was established to explain the anti-wear mechanisms and friction-reducing capacity of a-C:H solid lubrication films under sand-dust conditions.     

端面密封材料S-07不锈钢滑动摩擦学行为的分子动力学模拟

为探究端面密封材料S-07不锈钢在不同参数下的摩擦学行为,构建纳米尺度下S-07不锈钢的摩擦磨损模型,以对偶件的压入深度和滑动速度作为变量,研究S-07不锈钢表面摩擦学性能及形貌变化。结果表明：随着摩擦相对滑动速度的增加(50、100、150 m/s),S-07不锈钢磨损表面粗糙度降低;随着对偶件压入深度(0.3、0.6、0.9 nm)的增大,摩擦因数呈上升趋势;磨损量随压入深度增大而增大,随滑动速度上升呈下降趋势。在微观尺度上,从位错、塑性变形等角度解释了在不同磨损条件下S-07不锈钢性能变化的原因,为该材料适用摩擦工况的选择提供了理论参考。     

Speed and Atmosphere Influences on Nanotribological Properties of NbSe<Subscript>2</Subscript>

Nanotribological properties of NbSe₂ are studied using an atomic friction force microscope. The friction force is measured as a function of normal load and scan speeds ranging from 10 nm s⁻¹ to 40 μm s⁻¹ under two atmospheres (air and argon). At low speed, no effect of atmosphere is noticed and a linear relationship between the friction and normal forces is observed leading to a friction coefficient close to 0.02 for both atmospheres. At high speed, the tip/surface contact obeys the JKR theory and the tribological properties are atmosphere dependent: the shear stress measured in air environment is three times lower than the one measured under argon atmosphere. A special attention is paid to interpret these results through numerical data obtained from a simple athermal model based on Tomlinson approach.     

Structural characterization and tribological evaluation of quince seed mucilage

The mucilage, originating from the seeds of quince fruit was characterized as a potential bio-inspired water-based lubricant. The mucilage consists mainly of fine cellulose nanofibrils and charged hemicelluloses whose structure and properties were characterized here by atomic force microscopy (AFM) and tribological Pin-On-Disc (POD) experiments. The hemicellulose-decorated nanocellulose fibrils were 3.0±0.7 nm in thickness, had a very large aspect ratio and also had a tendency to self-align when dried on mica surface. Macroscale tribological tests showed that the mucilage was able to reduce the coefficient of friction of polyethylene/stainless steel contact to values below 0.03. Thus, we show that quince mucilage is a native nanocellulose material with a notable ability to lower friction.     

Effect of Tribofilm Formation on the Dry Sliding Friction and Wear Properties of Magnetron Sputtered TiAlCrYN Coatings

Nano-structured TiAlCrYN coatings, grown by unbalanced magnetron sputtering on various steel substrates, exhibited friction coefficients 0.6–0.8 and wear coefficients 10⁻¹⁶–10⁻¹⁵ m³ N⁻¹ m⁻¹ in dry sliding wear tests. This article reports comprehensive worn surface analyses using SEM, TEM, EDX, EELS and Raman spectroscopy. A ~80 nm thick tribofilm formed on the TiAlCrYN worn surface was found to have dense amorphous structure and homogeneous oxide composition of Cr_0.39Al_0.19Ti_0.20Y_0.01O_0.21. Viscous flow of the amorphous tribofilm was dominant in causing the high friction coefficient observed. The coatings showed combined wear mechanisms of tribo-oxidation and nano-scale delamination.     

Tribological behaviour of AISI 316L stainless steel for biomedical applications

Abstract

The aim of this research is to study the tribological behaviour of AISI 316L stainless steel for surgical implants (total hip prosthesis). The tribological behaviour is evaluated by wear tests, using tribometers ball on disc and sphere on plane. These tests consisted of measuring the weight loss and the friction coefficient of stainless steel (SS) AISI 316L. The oscillating friction and wear tests have been carried out in ambient air with an oscillating tribotester in accord with standards ISO 7148, ASTM G99-95a and ASTM G133-95 under different conditions of normal applied load (3, 6 and 10 N) and sliding speed (1, 15 and 25 mm s^?1). A ball of 100Cr 6, 10 mm in diameter, is used as counter pairs. These tribological results are compared with those carried out with a tribometer type pin on disc under different conditions of normal load applied P (19·43, 28 and 44 N) and sliding speed (600 and 1020 rev min^?1). The behaviour observed for both samples suggests that the wear and friction mechanism during the tests is the same, and to increase the resistance to wear and friction of biomedical SS AISI 316L alloy used in total hip prosthesis (femoral stems), surface coating and treatment are necessary.     

Tribological behaviors and mechanisms of Ti<Subscript>3</Subscript>AlC<Subscript>2</Subscript>

Tribological behaviors and the relevant mechanism of a highly pure polycrystalline bulk Ti₃AlC₂ sliding dryly against a low carbon steel disk were investigated. The tribological tests were carried out using a block-on-disk type high-speed friction tester, at the sliding speeds of 20–60 m/s under a normal pressure of 0.8 MPa. The results showed that the friction coefficient is as low as 0.1∼0.14 and the wear rate of Ti₃AlC₂ is only (2.3–2.5) × 10⁻⁶ mm³/Nm in the sliding speed range of 20–60 m/s. Such unusual friction and wear properties were confirmed to be dependant dominantly upon the presence of a frictional oxide film consisting of amorphous Ti, Al, and Fe oxides on the friction surfaces. The oxide film is in a fused state during the sliding friction at a fused temperature of 238–324 °C, so it takes a significant self-lubricating effect.     

Tribological behaviors of surfactant-functionalized carbon nanotubes as lubricant additive in water

The multi-walled carbon nanotubes (MWCNTs) are functionalized by self-assembled surfactant layers after sonication in anionic surfactant sodium dodecyl sulfate (SDS) aqueous solution. The tribological properties of the SDS-functionalized MWCNTs as additive in water-based lubricants were evaluated with a four-ball tester. The results show that the SDS-functionalized MWCNTs exhibit good anti-wear and friction reduction properties as well as enhanced load-carrying capacity. The maximum non-seizure load (PB value) can be raised about 3–7 times when SDS-functionalized MWCNTs were added into water. The mechanism of SDS-functionalized MWCNT additive was investigated with scanning electron microscopy (SEM), Auger electron spectroscopy (AES), and Raman spectroscopy. These preliminary results show a promise in applications of surfactant functional carbon nanotubes as an additive in water.     

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.     

Surfactant dithiophosphates lubricating oil additives

Abstract

This paper presents a research on the tribological properties and the action mechanisms of surfactant lubricating oil additives, polyalkoxy glycol ammonium salts and O,O,S-triesters of polyalkoxy glycol dithiophosphoric acid. To understand the physicochemical properties of surfactants, polyalkoxy glycol dithiophosphoric acid behaviour both in solution and at metal surfaces are identified and discussed. The STM adsorption on steel surface, four-ball and ball disc tests of friction of water, synthetic and mineral oil solutions studies of these additives are presented. Friction and wear properties are dependent on tribological parameters, chemical structure of the additives and their surface active behaviour in tribological systems. The relationships are presented on the example of additives with different molecular structures and masses.     

Comparative Investigation on Tribological Properties of Ion-Sulfuration Layers Under Dry Friction

Four kinds of steel, including high-speed steel (M2), die steel (L6), stainless steel (420) and plain carbon steel (1045), were treated by low-temperature ion sulfuration. Sulfide layers, dominated by the FeS phase, were produced on the surfaces of the four steels. The tribological properties of sulfide layers were investigated on a block-on-ring test rig under dry friction conditions. The results showed that the tribological properties of all sulfurized steels were remarkably improved. The tribological properties decreased in the order of high-speed steel—die steel—1045 steel—stainless steel. The hardness, microstructure and corrosion resistance of the substrate determined the differences in the tribological properties of different steels.     

Alkyl Imidazolium Ionic Liquids as Friction Reduction and Anti-Wear Additive in Polyurea Grease for Steel/Steel Contacts

Five room temperature ionic liquids (ILs), 1-butyl-3-methylimidazolium hexafluorophosphate (L-P104), 1-hexyl-3-methylimidazolium hexafluorophosphate (L-P106), 1-octyl-3-methylimidazolium hexafluorophosphate (L-P108), 1-decyl-3-methylimidazolium hexafluorophosphate (L-P110), and 1-hexyl-3-methylimidazolium tetrafluoroborate (LB106) were studied as 1 wt% additives of polyurea grease for steel/steel contacts. Their tribological behaviors as additives of polyurea grease for steel/steel contacts were evaluated on an Optimol SRV-IV oscillating reciprocating friction and wear tester and an MRS-1J (G) four-ball tester at room and high temperatures. The friction test results showed that the ILs, as 1 wt% additives in polyurea grease for steel/steel contacts, had better friction reduction and anti-wear properties at high temperature than at room temperature, and ILs can significantly improve the friction reduction and anti-wear properties of polyurea grease compared with base grease containing 1 wt% of zinc dialkyldithiophosphate (T204). The excellent tribological properties are attributed to the formation of a surface protective film composed of FeF₂, nitrides, and compound containing the P–O bonding on the lubricated metal surface by a tribochemical reaction. The ordered adsorbed films and good miscibility of ILs with the base grease also contributed to the excellent tribological properties. Wear mechanisms and worn steel surfaces were studied by a PHI-5702 multifunctional X-ray photoelectron spectrometer and a JSM-5600LV scanning electron microscope.     

NiAl Matrix High-Temperature Self-Lubricating Composite

A high-temperature self-lubricating composite NiAl–Cr–Mo–CaF₂ was fabricated using the powder metallurgy technique, and the tribological behavior of the composite at a wide range of temperatures (room temperature to 1000 °C) was investigated. The results showed that the composite had a favorable friction coefficient of about 0.2 and an excellent wear resistance of about 1 × 10⁻⁵ mm³N⁻¹m⁻¹ at the high temperatures tested (800 and 1000 °C). The excellent self-lubricating performance was attributed to the formation of the glaze film on the worn surface consisting mainly of CaCrO₄ and CaMoO₄ as high-temperature solid lubricants.     

Effect of Fluoride Content on Friction and Wear Performance of Ni<Subscript>3</Subscript>Al Matrix High-Temperature Self-Lubricating Composites

The self-lubricating composites Ni₃Al–BaF₂–CaF₂–Ag–Cr, which have varying fluoride contents, were fabricated by the powder metallurgy technique. The effect of fluoride content on the mechanical and tribological properties of the composites was investigated. The results showed that an optimal fluoride content and a balance between lubricity and mechanical strength were obtained. The Ni₃Al–6.2BaF₂–3.8CaF₂–12.5Ag–10Cr composite showed the best friction coefficients (0.29–0.38) and wear rates (4.2 × 10⁻⁵–2.19 × 10⁻⁴ mm³ N⁻¹ m⁻¹) at a wide temperature range (room temperature to 800°C). Fluorides exhibited a good reduced friction performance at 400 and 600°C. However, at 800°C, the formation of BaCrO₄ on the worn surface due to the tribo-chemical reaction at high temperatures provided an excellent lubricating property.     

表面粗糙度对Al2O3增强Y-TZP陶瓷材料生物摩擦学特性的影响

采用销-盘式摩擦磨损试验机研究了氧化铝增强氧化锆陶瓷(ADZ)的表面粗糙度对ADZ/316L不锈钢摩擦副的摩擦磨损性能的影响。结果表明:在小牛血清润滑下,随着陶瓷表面粗糙度的降低,ADZ陶瓷和316L不锈钢的摩擦因数和磨损率均呈降低趋势。但是对于表面粗糙度最高的陶瓷,由于Fe转移膜的物理吸附,出现了“负磨损”现象。     

甘油润滑下CrCN涂层的超低摩擦特性

为开发与CrCN涂层具有良好配伍润滑性能的绿色润滑剂,使用磁控溅射技术在304不锈钢表面沉积CrCN涂层,利用场发射扫描电子显微镜、原子力显微镜、纳米压痕仪、维氏硬度计、X射线衍射仪、X射线光电子能谱仪分别对其表面形貌、涂层厚度、力学性能、物相组成以及元素化学价态进行分析,并借助多功能摩擦磨损试验机评价在甘油润滑下CrCN涂层的摩擦学性能,并与PAO6润滑下结果进行比较。利用磁控溅射技术在不锈钢表面构筑的CrCN涂层表面光滑致密,粗糙度仅为1.01 nm,硬度可达14.39 GPa。对比钢-钢和钢-CrCN体系的摩擦学性能发现,钢-CrCN体系在甘油润滑下展现出优异的润滑性能;当负载为0.5 N时,钢-CrCN体系在甘油润滑下的摩擦因数可低至0.01,大大低于PAO6润滑下的摩擦因数。对磨痕的XPS分析表明,在摩擦过程中,甘油发生摩擦化学反应,在CrCN涂层的接触表面生成一层FeOOH层,甘油分子及其降解产物可能进一步吸附在FeOOH层,形成流体润滑层,有效降低了摩擦和磨损。