Tribological properties of grey cast iron lubricated using organic compounds containing Mo and ZnDTP additives

The lubricating effectiveness of organic compounds containing Mo and ZnDTP in different ratios in poly‐alpha‐olefin (PAO) was investigated using an Optimol SRV‐IV (Optimol Instruments, Munich, Germany) reciprocating friction and wear tester. The morphologies of the worn surfaces were observed using a scanning electron microscope with energy‐dispersive X‐ray spectroscopy. The chemical states of several typical elements on the worn surfaces of grey cast iron discs were examined by means of X‐ray photoelectron spectroscopy (XPS). The results indicated that the grey cast iron discs exhibited different friction‐reducing and wear‐resistance capabilities when lubricated with PAO containing MoDTP and ZnDTP additives in different ratios. The lowest frication coefficient is only 0.072. XPS analyses indicated that ZnDTP + MoDTP and ZnDTP + MoDTC formed different chemical products. Copyright © 2012 John Wiley & Sons, Ltd.     

Tribological properties of non‐ferrous coating lubricated with rapeseed oil containing lubricant additives

With the increasing requirements of environmental protection, using lead, hexavalent chromium and other heavy metals will be prohibited in different surface coatings. In this paper, the non‐ferrous CrN coatings and the rapeseed oil were chosen as friction pair and biodegradable lubricant. The tribology properties were investigated using SRV‐IV reciprocating friction wear test. The worn surface of CrN coatings was observed and analysed using scanning electron microscopy and X‐ray photoelectron spectroscopy. The results indicate that the rapeseed oil containing 1 wt.% MoZn (MoDTC (molybdenum dithiocarbamate) + ZnDTP (zinc dithiophosphate) (1 : 3)) exhibits better friction‐reducing properties than the rapeseed oil containing 1 wt.% PN (an amine salt of an alkoxylphosphate) additives, whereas the rapeseed oil containing 1 wt.% PN additive exhibits better wear resistance properties than the rapeseed oil containing 1 wt.% MoZn additives. This is partly attributed to the tribophysical and tribochemical reactions between the lubricant and the CrN coating sliding surfaces. Copyright © 2012 John Wiley & Sons, Ltd.     

Tribological properties of Fe7Mo6-based alloy under two ionic liquid lubrications

The tribological properties of Fe₇Mo₆-based alloy, Mo, Fe and ASTM class no. 45 cast iron disk specimens were investigated against ASTM 52100 steel balls under the lubrication of two different kinds of hydrophobic ionic liquid: N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (PP13-TFSI) and N-N-N-trimethyl-N-propylammonium bis(trifluoromethanesulfonyl)imide (TMPA-TFSI). When lubricated with PP13-TFSI or TMPA-TFSI, the Fe₇Mo₆-based alloy disk specimens exhibited lower friction coefficients and lower wear rates than the Mo, Fe and ASTM class no. 45 cast iron disk specimens. The low friction coefficients and low wear rates of the Fe₇Mo₆-based alloy were considered to be caused by the formation of low friction materials such as MoO₃ and FeSO₄ on the worn surface.     

Tribological properties of lubricated nanocrystalline diamond surfaces for various loads and geometries

Abstract

Diamond and diamond-like carbon films are well known for their outstanding properties such as high hardness, low coefficient of friction, good thermal conductivity, excellent biocompatibility and electrical insulation. Diamond films with nanocrystalline grains offer added advantages of higher hardness, improved surface finish (less roughness), very high sp³ content, etc. In view of the above, the present investigation is undertaken to explore the possibility of using nanocrystalline diamond films in advanced tribological applications. In this work, a nanocrystalline diamond film is deposited using a unique chemical vapour deposition (CVD) technique. The microstructural features are characterised using atomic force microscopy (AFM). Tribological behaviour of these films is evaluated by means of a reciprocating model tribometer with various lubricants. The worn surfaces are examined using three-dimensional confocal microscopy. The results show that these films have comparable friction coefficient with and without lubricants. Furthermore, they exhibited negligible wear for the tested range of loads.     

TiAl基合金的制备及其摩擦磨损性能

以钛粉、铝粉和铬粉为原料,采用机械合金化放电等离子烧结技术制备了TiAl基合金,分析了球磨时间和烧结温度对其物相组成、显微组织以及硬度的影响;用SiC砂轮为对偶件对TiAl基合金的摩擦磨损性能进行了研究.结果表明:混合粉经150 h球磨,1 173 K烧结9 min后所制备的合金具有较好的性能,其显微组织均匀细小,平均晶粒尺寸小于10μm,硬度达到68.2 HRC;与304不锈钢相比,烧结TiAl基合金具有更低的摩擦因数和更高的耐磨性,磨损机理为磨粒磨损.     

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.     

Tribological Properties of Films Formed by the Reaction of Carbon Tetrachloride with Iron

The tribological properties of halide films grown on iron by reaction with carbon tetrachloride vapor at a temperature of 617 K and a pressure of 1.7 Torr are compared, in ultrahigh vacuum, with FeCl₂ films evaporated onto the surface. It is found that the reactively formed film has a slightly lower limiting friction coefficient than the evaporated layer (~0.06 compared to ~0.08), which may be due either to the diffusion of some carbon into the substrate or the formation of a more oriented layer when this is formed reactively. The major difference between the reactively grown and evaporated film is that the evaporated layer attains the minimum friction when ~40 ? of FeCl₂ has been evaporated, while the reactively formed layer has a minimum friction coefficient when a film of 6±2 ? has been deposited. In the case of the evaporated FeCl₂ film, the growth of second and subsequent layers proceeds before the first layer is complete. It has been shown that the friction coefficient reaches its minimum value after completion of the first monolayer, a process that is complete after the evaporation of ~40 ? of FeCl₂. In the case of the film formed by reaction with CCl₄, the halide film grows directly on the surface implying that the FeCl₂ monolayer thickness is ~6 ?. This value is in good agreement with the layer thickness in bulk ferrous chloride.     

Friction and wear properties of Fe7Mo6-based alloy in ethyl alcohol

In this study, the friction and wear properties of Fe₇Mo₆-based alloy, Fe and Mo disk specimens sliding against ASTM 52100 steel and Cu and SiC ball (or pin) specimens in ethyl alcohol were evaluated using an Optimol SRV oscillating friction and wear tester. The Fe₇Mo₆-based alloy disk specimens exhibited more stable friction coefficients than the Fe and Mo disk specimens when slid against the ASTM 52100 steel ball specimen. On the other hand, the Fe/SiC tribo-pairs exhibited the lowest average friction coefficients (0.14-0.17).     

Tribological properties of molybdenum disulfide nanosheets by monolayer restacking process as additive in liquid paraffin

Molybdenum disulfide nanosheets were prepared by monolayer restacking process. Results of transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and scanning electron microscopy (SEM) showed that the obtained MoS₂ nanosheets had a thickness about 30-70 nm. The tribological properties of the so-prepared MoS₂ nanosheets were investigated on a MQ-800 four-ball tribometer. The results showed the base oil with MoS₂ nanosheets had better friction reduction, wear resistance and extreme pressure than those with commercial micro-MoS₂. The good tribological properties of MoS₂ nanosheets were mainly ascribed to the surface effect and the dimension effect of nanoparticles. Moreover, the formation of MoO₃ and FeSO₄ complex film on the rubbed surface also played an important role in friction reduction and wear resistance.     

Optimisation of Industrial Tribological Systems with the Pin‐on‐Disc Tribometer Method

The purpose of tribology is to improve the service life and efficiency of machines and their elements. This paper describes certain tests that can be done on a modified pin‐on‐disc apparatus to match in‐service conditions more closely. The three examples considered incorporate a liquid heating function, a reciprocating modification to allow for linear sliding rather than circular sliding, and a modification to allow the simulation of different lubrication regimes.     

Tribological properties of some water-based lubricants containing polyethylene glycol under boundary lubrication conditions

The metal-working industry is increasingly interested in synthetic metalworking fluids and coolants. The excellent lubricating properties of polyalkylene glycols have been recognised in areas such as gear lubricants, hydraulic fluids, and compressor lubricants. The main purpose of the present work was to investigate the friction and wear properties of several polyethylene glycols and their synergy with a common water-soluble EP additive, using four-ball and ball-on-plate tribometers.     

Tribochemistry of aluminium and aluminium alloy systems lubricated with liquids containing alcohol or amine additive types and some other lubricants — a review

The ability of a lubricating oil to reduce wear and prevent damage of interacting solids is a crucial factor controlling lubricant formulation. It is well known that friction produces local high temperatures. Many chemical reactions that are initiated by the friction process itself occur at much lower temperatures than those needed to provide the activation energy. Under boundary lubrication conditions, a clean surface exposed as a result of mechanical activity of the solid surface is extremely reactive, especially in the case of metals. This review mostly relates to the tribochemistry of aluminium, and discusses the tribological characteristics of alcohol‐ and amine‐type liquids used as either additives or lubricants to lubricate aluminium and its alloys under boundary friction conditions. Although tribochemical reactions during sliding are perceived in various ways, here the emphasis is on the negative‐ion‐radical action mechanism (NIRAM) approach. This review addresses the question as to how present knowledge of tribochemistry can be applied to the elucidation of the mechanisms of action by which the boundary lubricant compounds considered reduce aluminium‐on‐aluminium, steel‐on‐aluminium, and aluminium‐on‐steel wear. Also, information and a discussion on the tribological behaviour of other additives and/or lubricants in relation to the friction and wear of aluminium and its alloys are presented. A concise review of the most recent work on the tribochemistry of selected fluorinated alcohols is also included.     

Tribological properties of the film formed by borated dioctyl dithiocarbamate as an additive in liquid paraffin

This paper discusses the preparation of borated dioctyl dithiocarbamate as an oil-soluble antiwear and extreme pressure additive for lubricants. Its tribological performance when added to liquid paraffin was evaluated on a four-ball tester and a ring-on-block machine. The relationships between its performances and the concentrations are also given, and are compared with these of zinc dialkyldithiophospate (ZDDP). The results show that the novel compound possesses an excellent load-carrying capacity and friction reduction property similar to ZDDP, and exhibits better antiwear property than ZDDP above 392 N. In addition, the novel compound has good anticorrosive property and high thermal stability. The rubbed surface was investigated using X-ray photoelectron spectroscopy, and the antiwear mechanism was discussed.     

Tribological properties of HVOF as-sprayed and heat treated Co–Mo–Cr–Si coatings

HVOF-sprayed Co–28%Mo–17%Cr–3%Si alloy tribological performance was tested in the as-sprayed condition and after thermal treatments at 200, 400, 600 °C for 1 h. As-sprayed coating possesses low hardness, undergoes adhesive wear against 100Cr6 steel and displays an high-friction coefficient causing relevant thermal effects. The 600 °C-heat treatment increases microhardness, thus preventing adhesive wear and reducing friction.     

Tribological properties of asperity arrays coated with self-assembled monolayers

The effects of a self-assembled monolayer (SAM) coating on the friction and pull-off forces were determined by using two-dimensional asperity arrays on silicon wafers. The arrays were coated with SAM composed of one of five different alkylchlorsilanes. First, two-dimensional asperity arrays were created by using a focussed ion beam (FIB) system to mill patterns on silicon plates. Each silicon plate had different patterns of equally spaced asperities. Each pattern (5 × 5 μm²) had a different radius of curvature of the asperity peaks, ranging from about 200 to 2500 nm. Then, each silicon plate was immersed in a solution of a different alkylchlorsilane in hexane (either hexyltrichlorosilane, octyltrichlorosilane, dodecyltrichlorosilane, tetradecyltrichlorosilane, or octadecyltrichlorosilane), thus coating the asperity arrays with SAM. The friction and pull-off forces on the SAM-coated arrays were measured by using an atomic force microscope (AFM) that had a square flat probe. The pull-off force for SAM-coated silicon was roughly proportional to the radius of curvature of the asperity peaks. The magnitude of the pull-off force corresponded approximately to the capillary force calculated by using the contact angle of water on the surface of SAM. The friction coefficient correlated with the inverse of the alkyl-chain length of the SAM.     

含石墨镍基复合材料的摩擦学性能研究

用粉末冶金制备石墨wt．％含量为0，3，6,9的镍基白润滑合金，研究不同石墨含量对材料摩擦学性能的影响。     

Tribological properties of 4,5-di(cetyl thio)-1,3-dithiole-2-thione as additive in liquid paraffin

The synthesis of a new type of oil additive, 4,5-di(cetyl thio)-1,3-dithiole-2-thione, is described. The thermal stability of the compound was investigated by thermal gravity analysis (TGA). The tribological properties of the compound as additive in liquid paraffin were also evaluated using a four ball tester. The results show that the novel compound has good tribological properties in liquid paraffin. The lubricating mechanism was studied by electron probe microanalysis (EPMA) and X-ray photoelectron spectroscopy (XPS).     

Tribological properties of high temperature resistant polymer composites with fine particles

The tribological properties of two kinds of high temperature resistant thermoplastic composites, polyetheretherketone (PEEK) and polyetherimide (PEI), reinforced with short carbon fibre (SCF), graphite flakes, and sub-micro particles of TiO₂ and ZnS, were investigated in dry sliding conditions. Friction and wear experiments were conducted on a pin-on-disc apparatus, using composite pins against polished steel counterparts, performed within moderate pv-ranges at room and elevated temperatures (up to 150 °C). It was found that conventional fillers, i.e. SCF and graphite flakes, could effectively enhance both the wear resistance and the load-carrying capacity of the base polymers. With the addition of sub-micro particles, the frictional coefficient and wear rate of the composites were further reduced especially at elevated temperatures. On the basis of microscopic observation of worn surfaces, dominant wear mechanisms are discussed.     

A comparative study on the tribological behaviors of nitrided and sulfur-nitrided 35CrMo steel lubricated in PAO base oil with MoDTC additive

A nitrided layer on 35CrMo steel was prepared by the ion nitriding process, and then a sulfur-nitrided layer was obtained by low temperature ion sulfuration. The results showed that both the nitrided and sulfur-nitrided surfaces improved the wear resistance efficiently under PAO lubrication, and exhibited the best wear resistance and friction-reducing property under PAO with 0.75% MoDTC lubrication. Compared with the plain and nitrided surfaces, the sulfur-nitrided surface exhibited the best synergistic effect with MoDTC displaying the lowest friction coefficient and wear volume. The mechanism of the best effect was due to MoS₂ and FeS formed on the sulfur-nitrided surface.     

Tribological properties of fast-cutting steel tools and tools modified with iodine compounds

We present the results of studies of the processes that evolve in contact zones in the blade-cutting of metals and alloys when the surface layers of tool materials (fast-cutting steels) contain iodine compounds that have formed when the tools have been chemothermally or ion-plasma treated. It is established that iron diodide is the prevailing compound that modifies the physicomechanical behavior of high-speed steels without altering the microstresses in their surface layers. The structural and thermodynamic features of iron diodide have motivated the experimental validation of the mechanism of its effect on the processes of contact interaction The essence of the mechanism is the combination of the solid grease and the radical-chain reactions. Various operations of blade-cutting of a broad range of materials has demonstrated the effectiveness of iodine compounds for the cutting process characteristics and opertional ability of cutting tools. The utmost effect is achieved when machining titanium-based alloys.