Type Tribometer Research Articles

Tribological properties of a synthetic mica-organic intercalation compound used as a solid lubricant

Solid lubricants have long been widely used to enhance lubricity and to achieve a longer die life in the field of tribological applications. Molybdenum disulfide (MoS2) is the most desirable solid lubricant because of its low friction coefficient, good anti-seizure ability stemming from easy cleavage and excellent adhesion to the metal surface. Although MoS2 performs well, it has a disadvantage in that its black appearance significantly stains the working environment. Therefore, non-black solid lubricants are strongly desired. Herein, we investigated the properties of a clay-organic intercalation compound as a solid lubricant. It is well known that some types of layered clay minerals have a cation exchange capacity and are capable of being intercalated with an organic cation between the silicate layers. This reaction is based on the ion exchange of exchangeable inorganic ions (Na+, K+, etc.) in the layered clay minerals. In this study, we examined the properties of synthetic mica, whose silicate layers were intercalated with a cationic organic compound (dioctadecyl dimethyl ammonium chloride). We evaluated the lubrication performance of the mica using a newly devised upsetting-ironing type tribometer. X-ray diffraction (XRD) results show that the distance between the silicate layers of the intercalated synthetic mica increased to 36.6Å from 12.6Å for a non-intercalated one. Owing to the increase in the interlayer distance, the lubrication coating containing the synthetic mica-organic intercalation compound showed a much improved lubrication performance than that of the non-intercalated one. These findings indicate that the lubricity of the clay minerals is highly dependent on the friction between the different silicate layers, and that the cationic organic compound incorporated into the interlayers can improve the lubricity. This result means that the clay-organic intercalation compound is a promising solid lubricant as an alternative to MoS2.

METAL-METAL FRICTION PROPERTY AND GEAR DURABILITY PERFORMANCE FROM LUBRICANT ADDITIVE IN CONTINIOUSLY VARIABLE TRANSMISSION FLUIDS

The aim of this study is to clarify how lubricant additives used in fluids for belt type continuously variable transmissions (B-CVTFs) improve a gear pitting life with keeping a higher friction coefficient between the metal contacting surfaces. The metal-metal friction property was experimentally investigated by using a block on ring type tribometer, and the gear pitting life was evaluated by the standard FZG (Forschungsstelle fur Zahnrader und Getriebebau) gear test rig. As a result, a sort of extreme pressure agent was found to give a longer gear fatigue life with a keeping a higher friction coefficient between the metals. The difference in gear pitting life derived from extreme pressure agent would be more significant under a higher load condition on the gears. The tribofilms composed of calcium and phosphorus could minimize abrasion and adhesion in the contact regions of pinion tooth dedendum, leading to prevent from generating micropitting, consequently with a longer gear fatigue life.

Friction and Wear Behaviour of Glass Fibre Reinforced Polymer Composite (GFRP) under Dry and Oil Lubricated Environmental Conditions

This paper presents the friction and wears behaviour of GFRP (glass fibre reinforced polymer) composites fabricated by vacuum bagging process. Composites were experimentally investigated under two different sliding environments, (a) Dry environment and (b) Oil lubricated environment. Wear tests were conducted on a pin on disc type tribometer and steel as counter body with variable parameters. Experimental results depict that coefficient of friction and wear rate is less in oil lubricated sliding when compared with sliding in dry environment. In oil lubricated sliding, the coefficient of friction is reduced due to presence of softer epoxy resin body matrix in between layers of glass fibres. It is proposed that the lubricant gets absorbed on steel surface and the slight initial wear of the polymer also serves in effect as a “lubricant storage reservoir”, as a result the protruding glass fibres pick up lubricant molecules to effectively avoid fibre to steel contact and ensure effective thin film lubrication. In the dry sliding environment condition, images taken by FESEM shows that the rate of wear of composite increases due to increasing load and high friction as a result they undergo bending at the ends.

Tribological Properties of Zirconium Oxide, Spinel and Mullite Nanopowders as Lubricating Oil Additives

In work investigated effects of zirconium oxide (ZrO2), spinel (MgAl2O4) and mullite (Al6Si2O13) nanosized powders on the base oil tribological properties. The nanosized (30-40nm) powders manufactured by plasma chemical synthesis method. Tribological experiments used on ball-on-disc type tribometer, measured coefficient of friction and determined metalic disc wear. Base oil used selectively purified mineral oil (conform SAE-20 viscosity) without any functional additives. Nanosized powders dispersed in base oil at 0.5; 1.0; 2.0; wt.%. At work cocluded, that the adition nanoparticles in base oil, possible reduced friction pair wear and friction coefficient. As the main results include spinel (MgAl2O4) nanoparticles 0.5 and 1.0 wt. % concentration ability reduced friction coeffiecient value.

Design of a pin-on-disc-type CNC tribometer including an automotive dry clutch application

The paper presents the design of a pin-on-disc type tribometer intended for experimental characterization of static and dynamic friction behaviors for various sliding sample pairs. The normal force, slip speed, and temperature, as the main influencing parameters, are precisely controlled during experiments, by applying vertical and rotational servo-axes and an electric heater built in the rotating disc. A compact three-axial piezoelectric force sensor, placed between the vertical-axis screw drive and the friction sample, provides direct measurement of normal and tangential forces used to calculate the sample coefficient of friction. The slip speed is measured directly using an incremental encoder mounted at the rotational table. The disc temperature is measured by a built-in Pt probe, whose wires, together with the heater wires, are connected to the temperature control unit by means of slip rings. The tribometer performances are demonstrated through a study of coefficient of friction, shudder sensitivity, and wear rate characterization for a dry clutch friction material.

Sliding friction study of the oscillating translational motion for steel on PA66 and PA46 type materials

The paper presents the study of the friction, by using tests, in the sliding translational oscillating motion of the steel on PA46 relative to the steel on PA66 type materials by considering as variables the testing parameters as: the load, the velocity and the operating temperature. The paper starts with a study of the literature and, according to that, presents the main conclusions regarding the sliding friction of the steel on PA66 and PA46 type materials and identifies the lacks of the results. The tests are performed on an oscillating motion type tribometer module. First, it is made a running-in program, for each of the materials, at 25 and 90°C, a load of 5 N and a frequency of 1 Hz for one hour; after that, there are performed tests at 90°C and 120°C, at loads of 3 N, 5 N, 7 N and at frequencies at 0.25 Hz, 5 Hz and 1 Hz. The results are presented for the PA46 type material relative to the PA66 material. The conclusions indicate in which conditions and with which advantages are used the PA66 and PA46 polyamides in the case of oscillating translational motions.

Raman spectroscopy characterization of hypo-eutectic CoCrWC alloy tribolayers

Purpose This paper aims to study microstructure and high temperature tribological performance of hypo-eutectic CoCrWC hardfacing alloy (Stellite 12) deposited on steel substrate by plasma-transferred arc (PTA) welding technique. Design/methodology/approach Microstructural characterization of the deposited coating was made using electron probe microanalysis, X-ray diffraction and microhardness tester. Dry sliding wear tests were carried out with a ball-on-disc type tribometer at room and elevated temperature. Worn surfaces of the samples were examined by the EDX equipped SEM and Raman spectroscopy. Findings Results revealed that at room temperature and 300°C plasticity dominated wear mechanism was operative. Under oxidation dominated wear conditions (400, 500, 600 and 700°C), testing temperature plays a crucial role on the characteristics of the oxide tribolayers formed on worn surfaces. Development of Cr2O3 in the tribolayer at 600 and 700°C was beneficial in increasing wear resistance of examined coating. Originality/value While the sliding wear performance of Stellite alloys at room temperature has been investigated in details, published studies on tribological behavior of Stellite alloys with varying temperature are scarce. Therefore, the present work was undertaken to study the wear mechanisms and the type of tribolayers formed during sliding wear of PTA welding deposited hypo-eutectic Stellite 12 coating with increasing temperature up to 700°C.

Reactive-sputter-deposited β-Ta 2 O 5 and TaON nanoceramic coatings on Ti–6Al–4V alloy against wear and corrosion damage

Abstract In this study, two different types of nanoceramic coatings; namely, β-Ta2O5 and TaON, were synthesized by double glow discharge plasma technique on Ti–6Al–4V alloy to improve its wear and corrosion resistance. The new coatings were characterized by atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The two coatings were found to have a thickness of about ~ 25 μm and exhibit similar microstructural characteristics, i.e., composed of equiaxed grains with an average grain size of ~ 15 nm. They are tightly adhered to the Ti–6Al–4V substrate. Nanoindentation was used to determine the hardness and elastic modulus of the two coatings and the adhesion strength between the coatings and substrate was also evaluated by scratch testing. Dry sliding wear tests were performed using a ball-on-disk type tribometer, in which the two coatings were slid against Si3N4 ceramic balls under applied loads ranging from 2.3 N to 5.3 N at room temperature. Compared with the Ti–6Al–4V, the coated samples showed a decrease of two orders of magnitude in the specific wear rate, and the specific wear rates of the two coatings were also insensitive to the applied normal loads. The electrochemical behavior of the two coatings was characterized by potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and Mott–Schottky analysis in a naturally aerated 5 wt.% HCl solution. While both types of coatings were able to greatly improve the corrosion resistance of Ti–6Al–4V alloy, the TaON coating exhibit a higher corrosion resistance than the β-Ta2O5, due primarily to the TaON coating with a lower carrier density.

Tribological Properties of PVD Carbon-Copper Composite Films Reinforced by Titanium

Abstract Carbon-copper composite coatings reinforced with titanium were deposited using high power magnetron sputtering technique. Tribological and metrological tests were performed using Taylor Hobson Talysurf Intra 50 measuring equipment and CSM Instruments ball-on-disk type tribometer. Friction coefficient and wear rate were determined at 2N, 4N, 6N loads. It was revealed that friction coefficient decreased at a higher Ti concentration, which was particularly expressed at bigger applied loads. However, wear volume values tended to increase in the beginning, till Ti concentration reached about 11 %, but then decreased, thus providing better nanocoating wear resistance.

Friction properties of polyvinyl alcohol hydrogel measured by pendulum type tribometer

Friction properties of polyvinyl alcohol hydrogel measured by pendulum type tribometer

Dry Sliding Wear Behavior of Cast A7075 and A7075/SAF 2205 Composite Material

Abstract The wear behavior of cast A7075 and A7075/SAF 2205 composite material fabricated by vacuum-assisted investment flask casting was investigated under dry sliding condition. The wear tests were carried out using a “ball-on-disc” type tribometer. In the wear tests, 100Cr6 and ZrO2 balls were used as counterparts and the load, total distance and rotating speed were selected as 10 N, 100 m and 100 rpm, respectively. The results were evaluated using the friction coefficient–distance diagram, weight loss and wear rate. All worn surfaces were examined by scanning electron microscope and wear characteristics of the materials were discussed as a function of the microstructural features. It was concluded that composite material had lower friction coefficient, less weight loss and slower wear rate than that of cast material.

Mathematical Model of Friction Coefficient Determination for Lubricated Surfaces

<p class="R-AbstractKeywords"><em><span lang="EN-GB">This article reviews mathematical model for the determination of friction coefficient for lubricated surfaces which operate works at sliding friction pairs in boundary lubrication case. In the particular model an absolutely smooth ball and rough surface contact is viewed taking into account properties of the material, surface roughness parameters, lubricating material kinematic viscosity and density. The model refers to widely spread ball-on-disc type tribometer where ball is in the contacts with plane.</span></em></p>

Study of 2D and 3D Methods for Worn Surface Analysis of Tool Materials

This paper is dealing with the comparison of the results given by different worn surface analysing methods. Maraging steel tool materials were used for the experiments. Specimens were produced by direct metal laser sintering from metal powder and by conventional way from rod having equivalent chemical content. The samples were age-hardened and surface treated by nitrocarburising and oxynitriding and they were tested by pin- on-disc type tribometer. The tribological behaviour was compared by using different methods for worn surface analysis. Worn area of the surface was determined by the surface profiles of 2D measurements and the wear volume was calculated by using 3D images of focus variation microscopy measurements.

The effect of electron irradiation on the tribological property of perfluoropolyether grease in vacuum

Abstract A perfluoropolyether (PFPE) grease was exposed to 110 keV electron beam for fluence of 1 × 1015, 5 × 1015 and 1 × 1016 e/cm2 in vacuum. The friction and wear behaviour of the electron irradiated grease-lubricated 2Cr13 steel in vacuum was investigated by using a pin-on-disk type tribometer. The morphologies of the worn surfaces for the irradiated grease-lubricated 2Cr13 steel were observed by a scanning electron microscope (SEM). Gaseous products from the PFPE grease during the electron irradiation were monitored with a quadrupole mass spectrometer (QMS). The compositions and chemical states of grease samples before and after electron irradiation were analysed by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Results show that the irradiated grease-lubricated 2Cr13 steel sliding against the same material in vacuum presents a high friction and a high wear. The QMS, XPS and FTIR analyses reveal that COF2 gas, low molecular weight perfluoroethers and acid fluoride groups are formed due to decomposition when the PFPE grease is exposed to 110 keV electron beam in vacuum. Moreover, the base oil content of the PFPE grease decreases with increasing the electron irradiation fluence, leading to the loss of lubricating ability of the PFPE grease.

Structure and Properties of the Hardmetal Coatings Cr3C2-25NiCr Formed by a Multi-chamber Detonation Sprayer

The hardmetal Cr3C2-25NiCr (180-220 μm thick) coatings have been produced on a steel substrate by a multi-chamber detonation sprayer (MCDS). The characteristic feature of MCDS is that the powder is accelerated by using combustion products that are formed in MCDS chambers and are converged before entering the nozzle, where they interact with the two-phase gas-powder cloud. The microstructures and properties of the hardmetal coatings were examined with the use of optical microscopy, scanning electron microscopy, X-ray phase analysis, and a Vickers hardness tester with a 300 g test load. Wear tests were carried out using a computer controlled pin-on-disc type tribometer. It was established that MCDS has provided the conditions for formation of a dense hardmetal Cr3C2-25NiCr (180-220 μm thick) coatings with a porosity of less than 0.02%, microhardness 540±210 HV0.3 and a specific wear rate of 9.08∙10-5 mm3(m∙N)-1.

Deposition and Characterization of the Titanium-Based Coating by a Multi-Chamber Detonation Sprayer

This work introduces some of the aspects of the deposition of titanium-based coating (80-120 μm thick) on aluminium samples using a multi-chamber detonation sprayer (MCDS). The characteristic feature of MCDS is that the powder is accelerated by using combustion products that are formed in MCDS chambers and are converged before entering the nozzle, where they interact with the two-phase gas-powder cloud. The microstructures and properties of the coating were characterized with the use of scanning electronic microscopes (SEM), optical microscope (OM), X-ray Diffraction (XRD) techniques, and Vickers hardness tester with a 50 g test load. Wear tests were carried out using a computer controlled pin-on-disc type tribometer. It was established that MCDS has provided the conditions for formation of a dense titanium-based coating with a porosity of less than 1.0%, microhardness 810±250 HV0.05 and a specific wear rate of 2.077∙10-4 mm3(m∙N)-1.

Dry sliding wear behaviour of cast roller materials

In this study, wear behaviour of roller materials produced by different casting techniques was investigated. Static and centrifugal casting techniques were used to produce roller materials having pearlitic and martensitic matrices due to the processing method and alloy composition. The roller materials were examined using light and scanning electron microscopes to determine the matrix phase. The samples were tested using 'ball–on–disc' type tribometer to study the wear characteristics of cast morphologies. DIN 100Cr6 steel ball with a 5 mm diameter was used as counterface, load force was selected as 50 N and total sliding distance was 500 m. After wear tests, the surfaces of cast parts were examined by light and scanning electron microscopes to evaluate the wear mechanisms under dry sliding condition. The friction coefficient, weight loss and type of wear mechanisms were determined. It was concluded that the material having finer martensitic matrix produced by centrifugal casting had a higher wear resistance than the one produced by static casting.

수중환경에서 Fe계 벌크 비정질 합금의 트라이볼로지적 거동

The tribological behavior of an Fe-based bulk amorphous alloy while sliding against a AISI 304 disc is investigated using a unidirectional pin-on-disc type tribometer in dry and distilled water environments. The rod-shaped bulk pins are fabricated by suction casting. The crystallinities of the bulk amorphous alloys before and after the friction tests are determined by X-ray diffraction. The friction coefficient and specific wear rate of the amorphous pin in the water environment are found to be twice and thrice as much as in the dry environment at a low applied pressure, respectively. However, at a higher pressure, the friction coefficient and specific wear rate are 0.4 and 1.02 mg/(Nm/s), respectively, in the water environment. A microstructure analysis shows that the worn surface of the alloy is characterized by delamination from the smooth friction surface, and thus delamination is the main wear mechanism during the friction test in dry sliding environment. In contrast, brittle fracture morphologies are apparent on the friction surface formed in distilled water environment. For the sample tested at a lower sliding speed, the XPS data from the oxide layer are similar to those of the pure element with weak suboxide peaks. For higher sliding speeds, all the main sharp peaks representing the core level binding energies are shifted to the oxide region.

Role of Cr additions in enhancing wear and oxidation resistance of (Mo1−xCrx)Si2 nanocrystalline films

In order to explore the effects of Cr alloying on the wear and oxidation resistance of MoSi2 films, four kinds of (Mo1−xCrx)Si2 (x=0, 0.05, 0.10 and 0.15) nanocrystalline films of differing Cr contents were fabricated onto Ti6Al4V substrates by a double cathode glow discharge apparatus. The microstructure features of the as-deposited films were characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The hardness and elastic modulus of the (Mo1−xCrx)Si2 nanocrystalline films were evaluated by nano-indentation. The dry sliding wear properties of the as-deposited films sliding against GCr15 rolling bearing steel were studied using a ball-on-disc type tribometer at room temperature. The results showed that the friction coefficients and specific wear rates of the (Mo1−xCrx)Si2 nanocrystalline films decreased with increasing Cr content in the films. The oxidation behavior of the (Mo1−xCrx)Si2 nanocrystalline films was investigated at 500°C under cyclic oxidation conditions in air for exposure time of 100h. The oxidation kinetics of the films was found to obey a subparabolic behavior, and three Cr-containing MoSi2 films showed a much lower weight gain and the oxidation rate constant as compared to the monolithic MoSi2 film during a 100h exposure. Surface morphologies, phase constituents and electrochemical behavior of the oxide scales formed on the (Mo1−xCrx)Si2 nanocrystalline films were characterized using FESEM, XRD and electrochemical-impedance spectroscopy (EIS). The electrochemical results revealed that the structure of the oxide scales changed from a homogeneous and dense structure to a duplex structure consisting of a porous outer layer and a denser inner layer. The overall resistance of the oxide scales depended strongly on both the oxidation time and Cr content in the films.

Tribological Behaviors of Hybrid PTFE/Nomex Fabric/Phenolic Composite under Dry and Water-Bathed Sliding Conditions

The tribological behaviors of hybrid polytetrafluoroethylene (PTFE)/Nomex fabric/phenolic composite under dry sliding condition and water-bathed sliding conditions were investigated using a pin-on-disk type tribometer. The results showed that this hybrid fabric reinforced composite exhibited a higher wear rate and a lower friction coefficient under water-bathed sliding conditions compared to that measured under dry sliding condition. Scanning electron microscopy (SEM) and X-ray photoelectron microscopy (XPS) analysis demonstrated that under water-bathed sliding conditions the transfer films formed on the counterpart pins surface were of high roughness and less PTFE transferred onto the pin surface, compared to that under dry sliding condition. Moreover, the hybrid fabric composite displayed varied tribological behaviors when distilled water-bathed sliding condition and seawater-bathed sliding condition were applied separately.