Tribological characteristics of bisphenol S bis(diphenyl phosphate) as a high‐performance antiwear additive in lubricating greases at elevated temperature

Bisphenol S bis(diphenyl phosphate) (BSDP) was synthesised and characterised, and its tribological behaviours as additives in polyurea grease and lithium complex grease were evaluated for steel/steel contact at 200 °C. The results indicated that BSDP could dramatically reduce the friction and wear of sliding pairs in the base grease of polyurea, and the tribological performances of BSDP in polyurea grease were significantly superior to the normally used molybdenum disulfide‐based additive package. Furthermore, BSDP in polyurea grease has better tribological behaviour than that in lithium complex grease at a constant load of 100 N. X‐ray photoelectron spectroscopy analysis indicated that boundary lubrication films composed of Fe(OH)O, Fe₂O₃, Fe₃O₄ and FePO₄ compounds containing the P–O bonds and nitride compounds were formed on the worn surface, which resulted in excellent friction reduction and antiwear performance. Copyright © 2016 John Wiley & Sons, Ltd.     

Effect of thermal activation on the tribological behaviours of serpentine ultrafine powders as an additive in liquid paraffin

The influence of thermal activation temperature on the tribological properties of surface-coated serpentine ultrafine powders as liquid paraffin additives was studied. It is found that the serpentine powders suspended in liquid paraffin present excellent tribological properties. Thermal activations in a temperature range from 300 to 600 °C increase the film forming ability and tribofilm completeness of the serpentine, keep the layer structure and accordingly further improve the tribological properties. However, the layer structure is destroyed and hard phases appear after thermal activated at or higher than 850 °C, as results in the aggravation of friction and wear.     

CuNiCoBe材料抗滑动磨损性能研究

船闸易损件具有高耐磨性是船闸正常工作的一个关键因素。通过对CuN iCoBe材料在水润滑和锂基脂+3%MoS2润滑条件下的试验,论证了HB200和HB270两种热处理的CuN iCoBe材料作为船闸耐磨材料的可能。在销盘实验机上测试了两种热处理材料的耐磨性。试验表明,材料在水润滑条件下耐磨性很差,但仍好于其它同等实验条件下很多材料的耐磨性,HB200和HB270材料的平均磨损率分别为7.3×10-6g/m和3.9×10-6g/m;在锂基脂+3%MoS2润滑条件下耐磨性很好,HB200和HB270材料的平均磨损率分别为1.46×10-7g/m和2.05×10-7g/m。通过SEM分析磨损表面发现在水润滑条件下的磨损机理是塑性变形,而在锂基脂+3%MoS2润滑条件下,材料的磨损机理是轻微犁沟作用。     

Comparative study of the tribological properties of ionic liquids as additives of the attapulgite and bentone greases

Three kinds of ionic liquids (1‐butyl‐3‐methylimidazolium hexafluorophosphate (L‐P104), 1‐hexyl‐3‐methyl imidazolium hexafluorophosphate (L‐P106) and 1‐octyl‐3‐methylimidazolium tetrafluoroborate (LB108)) were added to the attapulgite base grease and the bentone base grease to investigate and compare the tribological behaviours of the ionic liquids with the two base greases at room temperature and 150°C. Tribological tests were performed using a ball‐on‐plate reciprocating tribometer. The attapulgite base grease showed better wear resistance properties than that of bentone base grease by adding ionic liquids as additives. At same time, the attapulgite base grease showed excellent friction‐reducing and wear resistance properties at high temperature (150°C). Also, we discussed the tribological mechanism of the attapulgite base grease at both room temperature and 150°C from the aspect of the structure of the grease thicker. Copyright © 2012 John Wiley & Sons, Ltd.     

Tribological properties of nano‐calcium borate as lithium grease additive

Nano‐calcium borate (NCB) with an average particle size of about 70 nm was synthesised via ethanol supercritical fluid drying technique, and the morphology and microstructures of as‐prepared particles were characterised by means of scanning electron microscope (SEM, JEOL LTD., Tokyo, Japan) and X‐ray powder diffraction. The friction and wear behaviour of the NCB as additive in lithium grease were evaluated with an Optimol‐SRV IV (Optimol Instruments Prüftechnik GmbH, Munich, Germany) oscillating friction and wear tester (SRV tester). The morphology and surface composition of the worn surfaces of lower discs after SRV test were analysed by SEM and X‐ray photoelectron spectroscopy (XPS, Physical Electronics, Inc., USA). The result demonstrated that the anti‐wear and load‐carrying capacities of the lithium grease were significantly improved, and the friction coefficient of the lithium grease decreased with the addition of NCB additive. The analytical results of XPS indicate that the good tribological performance of NCB is attributable to the formation of a boundary lubrication film composed of deposited NCB and the tribochemical reaction products such as B₂O₃, CaO and iron oxides on the rubbing surface. Copyright © 2013 John Wiley & Sons, Ltd.     

The Preparation and Tribological Investigation of Ni–P Amorphous Alloy Nanoparticles

Amorphous Ni–P alloy nanoparticles were synthesized by chemical reduction of nickel acetate in water reacted with sodium hypophosphite under stirring. The nanoparticles were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Results of XRD and TEM showed that nanoparticles have an average diameter 100 nm. And XPS analysis indicated that part of the surface of Ni–P amorphous alloy nanoparticles was oxidized. The tribological properties of the prepared Ni–P nanoparticles as an additive in lithium grease were evaluated with a four-ball friction and wear tester. The worn surfaces of the lubricated GCr15 steel were analyzed by means of XPS and scanning electron microscopy (SEM). The lubricating mechanisms were discussed on the basis of XPS and SEM analyses of the worn steel surfaces. The results show that these nanoparticles as a grease additive can effectively enhance the friction-reduction and antiwear ability of lithium grease. Tribochemical reactions were involved for steel–steel frictional pair lubricated with the lithium grease containing amorphous Ni–P alloy nanoparticles, with the formation of a boundary lubricating and protecting film composed of additives of lithium grease and tribochemical reaction products (iron phosphate, iron oxides, nickel oxide, nickel, etc.) of the lubricants. This contributes to improve the tribological properties of the lithium grease.     

Comparative tribological properties of magnesium hexasilicate and serpentine powder as lubricating oil additives under High temperature

Friction and wear experiments were carried out with nanoscale serpentine (magnesium silicate mineral) and magnesium hexasilicate powder as lubricating oil additives at 400 °C. The tribological test results showed that the self-repairing protective layers could be well formed on the contact surfaces, whether nanoscale serpentine or magnesium hexasilicate powder was added into lubricating oil. The SEM and EDAX analysis demonstrate that the morphology and elements of both self-repairing layers are in accordance with each other. The research results indicate that the essence of self-repairing of serpentine power is isomorphic replacement and tribochemical reaction between magnesium silicate and metal matrix.     

Conductive and Tribological Properties of Lithium-Based Ionic Liquids as Grease Base Oil

This article reports several conductive greases prepared by ionic liquids (ILs) that are synthesized by mixing lithium tetrafluoroborate (LiBF₄) or lithium bis(trifluoromethane-sulfonyl) imide (LiNTf₂) in diglyme (G2) and tetraglyme (G4) with appropriate weight ratios at room temperature (RT). The ILs have good solution in poly(ethylene glycol-ran-propylene glycol) monobutyl ether (PAG) and thus can be used as a base oil for preparing grease for steel–steel contacts. The electrical conductive properties of the grease prepared with the mixed oil of PAG plus ILs were evaluated using the DDSJ-308A conductivity tester, GEST-121 volume surface resistance tester, and HLY-200A circuit resistance tester. Combining the free volume with viscosity, the conductivity is inversely proportional to viscosity. The tribological properties were investigated using an MFT-R4000 reciprocating friction and wear tester. The results demonstrated that the prepared greases possess better conductive and tribological properties than the commercial grease with Cu powder as an additive.     

Effect of temperature on friction and wear of prehardened tool steel during sliding against 22MnB5 steel

Abstract

Mechanical components in tribological systems exposed to elevated temperatures are gaining increased attention since more and more systems are designed to operate under extreme conditions. In hot metal forming, the effect of temperature on friction and wear is especially important since it is directly related to process economy (tool wear) and quality of the produced parts (friction between tool and workpiece). This study is therefore focused on fundamental understanding pertaining to the tribological characteristics of prehardened hot work tool steel during sliding against 22MnB5 boron steel. The tribological tests were carried out using a high temperature reciprocating sliding friction and wear tester under a normal load of 31 N (corresponding to a contact pressure of 10 MPa), a sliding speed of 0·2 m s^?1 and temperatures ranging from 40°C to 800°C. It was found that friction coefficient and specific wear rate decreased at elevated temperature because of formation of compacted wear debris layers on the surfaces.     

Tribological Performance and Surface Analysis of a Borate Calcium as Additive in Lithium and Polyurea Greases

In this work, a borate calcium additive was added to lithium and polyurea greases to investigate the tribological performance. Friction and wear tests were conducted on a four-ball machine under higher load and a reciprocating tribometer under lower load. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) analyses were performed on the worn surface after the tests. It was found that the tribological performance affected the boundary layers formed by the additive and the soap fibers. The boundary films in lithium grease mainly consist of ferrum hydroxide, and more oxide can be found in polyurea-based films. SEM analyses of soap fibers show that the soap fibers in polyurea-based grease were more separated than those in lithium-based grease. Compared to the base grease, the soap shows smaller and shorter fibers.     

The Effect of FeS Solid Lubricant on the Tribological Properties of Bearing Steel under Grease Lubrication

In order to improve the tribological properties of 52100 steel under grease lubrication, FeS solid lubricant was used in two ways. Low-temperature ion-sulfurization technology was utilized to prepare solid lubricant iron sulfide (FeS) films on the surface of 52100 steel, and FeS particles were mixed into the lithium grease as additive. The friction and wear properties were examined systematically on a “ball-on-disc” testing machine. The results showed that the tribological properties of bearing steel under grease lubrication can be improved either by using ion-sulfurization technique or by adding FeS microparticles into the grease. The tribological performance of sulfurized surface lubricated by grease is better than that of a plain surface lubricated by grease containing FeS microparticles at lower load and speed. The plain surface lubricated by the grease containing FeS micropaticles possesses better antiwear property under harsher conditions. The mechanism of the experimental results is discussed in detail.     

High temperature friction and wear mechanism map for tool steel and boron steel tribopair

Abstract

Tribological systems working under severe conditions like high pressures, sliding velocities and temperatures are subjected to different phenomena such as wear, oxidation and changes in mechanical properties. In many cases, there are several mechanisms occurring simultaneously. The predominating type(s) of wear mechanism(s) presented will depend on the materials in contact, operating parameters and surrounding environment. In this work, high temperature tribological studies of boron steel sliding against tool steel were conducted using a pin-on-disc machine under unlubricated conditions at five different temperatures ranging from 25 to 400°C, three different loads: 25, 50 and 75 N (contact pressures of 2, 4 and 6 MPa respectively) and a sliding speed of 0·2 ms^?1. Scanning electron microscopy/energy dispersive spectroscopy and X-ray techniques were used for analysing the resulting damage and tribolayers of the worn surfaces. Additionally, hardness measurements were carried out in a special hot hardness rig in the same temperature range as that used in pin-on-disc tests. The results have shown that for a given load, the wear rate of boron steel decreased as the temperature increased, reaching its lowest value at 400°C at 50 N. In the case of the tool steel, it could be observed that at 200°C and above, the wear rate decreased as the load increased. This behaviour is consistent with the formation of a protective oxidised layer initiated at 100°C. At higher temperatures, such layers become more pronounced. The obtained data were finally used to construct a friction and wear mechanism map for this material pair that takes temperature and pressure into account.     

Oil‐soluble lithium salts as novel lubricant additives towards improving conductivity and tribological performance of bentone grease

The tribological and conductive properties of three kinds of lithium salts (LiBF₄, LiPF₆ and LiNTf₂) as lubricating additives in bentone grease were investigated in detail. As compared with the bentone‐based grease, the lithium salts as its additives not only provide excellent tribological properties but also greatly improve the load‐carrying capacity and electrical conductivity. These benefits are strongly dependent on the formation of a versatile boundary lubricating film and ion diffusion of lithium salts through an external electric field effect. Copyright © 2014 John Wiley & Sons, Ltd.     

Tribological Behavior of Amorphous and Crystalline Overbased Calcium Sulfonate as Additives in Lithium Complex Grease

The aim of this study was to examine the tribological behavior of amorphous overbased calcium sulfonate (AOBCS) and crystalline overbased calcium sulfonate (COBCS, transformed from the AOBCS) as additives in lithium complex grease. The transformation product of the calcium carbonate polymorph from AOBCS was calcite, as determined by Fourier transform infrared spectroscopy. Tribological properties were evaluated by an oscillating reciprocating friction and wear tester and a four-ball tester. The results showed that the addition of COBCS can dramatically improve both the antiwear performance and the friction-reducing and load-carrying properties of the base grease. However, improvement of the tribological properties of the base grease by AOBCS was highly dependent on the concentrations added and the loads applied. The tribological properties of the base grease were improved more by the addition of COBCS than by the addition of AOBCS. X-ray photoelectron energy spectrometry and thermogravimetric analysis revealed that both AOBCS and COBCS underwent complicated tribochemical reactions in the base grease and that chemically reactive films consisting of CaCO₃, CaO, iron oxide and organic compounds were formed on the worn surfaces. Taken together with the results of the tribo-tests, we suggest that transformation of the calcium carbonate polymorphs was the main factor in improving the tribological properties of lithium complex grease. The transformation of calcium carbonate polymorphs can broaden the application of AOBCS as an extreme pressure/antiwear additive in greases under boundary lubrication conditions.     

Effect of thermal activation on the tribological behaviours of serpentine ultrafine powders as an additive in liquid paraffin

The influence of thermal activation temperature on the tribological properties of surface-coated serpentine ultrafine powders as liquid paraffin additives was studied. It is found that the serpentine powders suspended in liquid paraffin present excellent tribological properties. Thermal activations in a temperature range from 300 to 600 °C increase the film forming ability and tribofilm completeness of the serpentine, keep the layer structure and accordingly further improve the tribological properties. However, the layer structure is destroyed and hard phases appear after thermal activated at or higher than 850 °C, as results in the aggravation of friction and wear.     

Tribological Behavior of Protic Ionic Liquids with Dodecylamine Salts of Dialkyldithiocarbamate as Additives in Lithium Complex Grease

Three kinds of protic ionic liquids with ammonium salts, dodecylamine salt of S-(1-carboxyl)-propyl-N, N-diethyldithiocarbamate (coded as DDED), dodecylamine salt of S-(1-carboxyl)-propyl-N, N-dibutyldithiocarbamate (coded as DDBD), dodecylamine salt of S-(1-carboxyl)-propyl-N, N-dioctyldithiocarbamate (coded as DDOD) were synthesized, characterized, and their tribological behaviors as additives in lithium complex grease were studied for steel/steel contact. The tribological properties were evaluated on an Optimol SRV-I oscillating reciprocating friction and wear tester and a MRS-10A lever-type fourball tester in details. The results of tests demonstrated that the novel additives were able to remarkably improve the extreme pressure, friction-reducing, and anti-wear properties of the base lithium complex grease when added at a low adding concentration (<3?%). Based on the performance comparison of three novel additives with different chain lengths in DTCs groups and a commercial additive with similar DTCs groups but no PILs groups, methylene bis dibutyldithiocarbamate (T323), a number of primary conclusions were drawn. The carboxylic acid ammonium salts, the typical function groups of the PILs existing in the molecule structures of three additives, could not only greatly enhance the physical and/or chemical adsorption on the metal surface to reduce friction of the base grease, and also have better synergism with DTCs groups in improving anti-wear performance of base grease. Based on the characterization and analysis of the worn surface by a PHI-5702 multifunctional X-ray photoelectron spectrometer (XPS) and a JSM-5600LV scanning electron microscope (SEM), a protective film consisting of FeS, organic compound was formed on the surface. The ordered adsorbed film and chemical reactive film on the sliding steels contributed to the main factor in improving the tribological properties of base lithium complex grease.     

Tribological behaviors of surface-coated serpentine ultrafine powders as lubricant additive

The effect of surface-coated ultrafine powders (UFPs) of serpentine suspended in lubricants on the tribological behaviors of a mated 1045 steel contact was investigated. Through the addition of serpentine UFPs to oil, the wear resistance ability was improved and the friction coefficient was decreased. The addition of 1.5 wt% serpentine to oil is found most efficient in reducing friction and wear. The nano-hardness and the ratio of hardness to modulus of friction surface are observably increased. Such effects can be attributed to the formation of a tribofilm of multi-apertured oxide layer, on which the micrometric alumina particles embedded and serpentine nano-particles adsorbed.     

Effects of Aging Treatments on the High-Temperature Wear Behavior of 60Nitinol Alloy

This study was undertaken to investigate the effect of heat treatments on the high-temperature wear behavior of 60Nitinol. The samples were hot-worked, aged at two temperatures of 400 and 700°C for 1 h and then water quenched. The microstructure of the alloys was investigated by scanning electron microscopy and X-ray diffraction. Sliding wear tests were performed at two temperatures of 25 and 200°C using three types of 60Nitinol disks: hot-worked, aged at 400°C, and aged at 700°C. All wear tests were performed at a speed of 0.3 m/s under a normal load of 60 N for a total sliding distance of 1,000 m using WC-Co pins sliding against 60Nitinol disks. The worn surfaces and microstructure of the subsurfaces were studied by scanning electron microscopy. Compression and hardness tests were also performed to characterize the mechanical properties of the alloys. The highest fracture strain and lowest hardness were obtained for the sample aged at 700°C that contained Ni₃Ti₂ precipitants. This sample also showed the maximum wear resistance at a wear testing temperature of 200°C. This was attributed to the formation of a more compact and stable tribological layer on the worn surface of the softer sample.     

Effect of Heat Treatment Temperature on Microstructure and Mechanical and Tribological Properties of Cold Sprayed Ti-6Al-4V Coatings

In this study, Ti-6Al-4V (Ti-64) coatings were prepared on commercial Ti-64 substrates via a high-pressure cold spray process. The coatings were heat treated at different temperatures of 400–1000°C to investigate the effect of heat treatment temperature on their microstructure and mechanical and tribological properties. The increased heat treatment temperature from 400 to 600°C promoted diffusion between sprayed Ti-64 particles. Recrystallization of the sprayed particles was found at the heat treatment temperature of 800°C and grain growth was found in the microstructure of the coating heat treated at 1000°C. The highest and lowest hardnesses of the heat-treated coatings were found at heat treatment temperatures of 400 and 800°C, respectively. Therefore, the lowest and highest specific wear rates of the coatings were consistently found at 400 and 800°C due to their highest and lowest abrasive wear resistances associated with their highest and lowest surface hardnesses, respectively. The coating heat treated at 400°C showed the highest surface hardness of 470.1 Hv and lowest specific wear rate of 69.6 × 10^?14 m³/Nm. It could be concluded that the microstructure and mechanical and tribological properties of the Ti-64 coatings were significantly influenced by heat treatment temperature.     

油胺修饰镍纳米粒子在锂基脂中的摩擦学性能*

为提高镍纳米粒子作为润滑脂添加剂的减摩和抗磨能力,采用油胺对其进行修饰以减少团聚,通过SEM、FT-IR和XRD对OA-Ni的微观形态和结构进行了表征,利用四球摩擦试验机和TE77往复摩擦试验机考察表面修饰的镍纳米粒子(OA-Ni)对锂基润滑脂摩擦学性能的影响,并探讨其在润滑脂中的减摩抗磨机制。结果表明:制备的油胺修饰镍纳米粒子呈不规则的圆片状,粒径约为100 nm,在润滑脂中有良好的分散性;经油胺表面改性的镍纳米粒子能有效改善锂基脂的摩擦学性能,抗磨和减摩性能分别提升了36.6%和15%。磨损表面分析结果表明,在摩擦过程中油胺修饰的镍纳米粒子在摩擦表面形成了主要成分为Fe2O3、 Fe3O4、NiO、Ni2O3等金属氧化物的摩擦化学膜,提高了锂基脂的摩擦学性能。