Reciprocating Friction Tester Research Articles

Study on Friction and Wear Performance of Sliding Metal Seal Materials Under Reciprocating Motion.

During petroleum drilling, the reciprocating motion in the seal device leads to piston and sleeve wear, which may cause leakage of the sealing medium. Selecting appropriate materials for the piston and sleeve, along with surface modifications, can effectively prolong the seal service life of the seal. The friction and wear properties of piston and sleeve pairs of different materials in a metal sealing device were simulated by the laboratory "pin-on-block" reciprocating friction test. Pins made of 45# steel, 35CrMo, and 20Cr13 were used to simulate piston bulges, while 35CrMo samples were used to simulate sleeves. Additionally, the influence of DLC (diamond-like carbon) coating and QPQ (Quench-Polish-Quench) nitriding on the wear resistance of the materials was studied. Based on this, the friction and wear properties, along with the wear mechanism of different material pairs, were analyzed. The results show that the friction coefficient curves of the three piston base materials and the 35CrMo sleeve are similar, and the friction coefficient of 45# steel is lower than that of 35CrMo and 20Cr13 at the initial stage. The DLC surface coating exhibited the best anti-wear performance, with the lowest friction coefficient, minimal wear, and the most stable friction coefficient. Surface QPQ nitriding treatment can also improve the wear resistance of the base material. However, due to the oxide formed during nitriding being prone to flaking, the friction coefficient fluctuates significantly at the initial stage of testing, and its anti-wear performance was inferior to that of the DLC coating. This study on material pairing and surface modification provides theoretical support for material selection and surface modification design of pistons and sleeves in oil drilling sealing devices.

Synthesis and Performance Evaluation of Metallocene Polyalphaolefins (mPAO) Base Oil with Anti-Friction and Anti-Wear Properties

Anti-wear and anti-oxidation abilities are two key properties of lubricants that play a crucial role in ensuring long-term stable equipment operation. In this study, we aimed to develop a base oil with good anti-oxidation and anti-wear properties for use under extreme pressure. The as-prepared metallocene polyalphaolefin (mPAO) was chemically modified using the trifluoromethanesulfonic acid (TfOH) catalysis through an alkylating reaction with triphenyl phosphorothioate (TPPT). During the experiments, when the reaction temperature exceeded 70 °C or the concentration of TfOH exceeded 2.67%, the β-scission reaction in the alkylation process became significantly more pronounced. The physical and chemical properties of TPPT-modified mPAO (T-mPAO) were evaluated by nuclear magnetic resonance spectroscopy, Fourier trans-form infrared spectroscopy, gel–permeation chromatography, and ASTM standards. T-mPAO showed significantly improved antioxidant capacity, with the initial oxidation temperature increasing by 32 °C compared to the base oil, and it exhibited the slowest increase in acid number in the 96-h oven oxidation test. The tribological tests showed that T-mPAO had the lowest friction coefficient, wear track, and wear rate (72.7% lower than that of mPAO) as well as the highest PB (238 kg) and PD (250 kg) among all tested samples. Compared to mPAO, the average friction coefficient of TPPT-modified mPAO in the four-ball friction test was reduced by 30.5%, and by 16.4% in the TE77 reciprocating friction test. Based on the experimental results, T-mPAO had strong anti-oxidation ability and excellent lubricating performance.The successful synthesis of multifunctional mPAO has enabled lubricant base oil additization, making it possible to use it in more demanding work scenarios, greatly broadening its application scope and making lubricant formulation blending more flexible.

Correlation between preparation techniques and frictional properties of cellulose nanocrystals as additives in water-based lubricants

To explore the tribological characteristics of cellulose nanocrystals derived through various preparation techniques when utilized as additives in water-based lubricants, two types of cellulose nanocrystals (S-CNC and C-CNC) were chosen. These were produced via sulfuric acid hydrolysis and oxidation methods. The morphology and structural features were assessed through techniques such as Fourier-transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRD), laser confocal Raman spectroscopy, elemental analysis, scanning electron microscopy (SEM), and laser particle size analysis. According to thermogravimetric analysis (TGA), the thermal stability of S-CNC is slightly superior to that of C-CNC. S-CNC exhibits liquid crystallinity when the concentration exceeds 0.5 %, whereas C-CNC does not display liquid crystallinity at any concentration tested. Further investigation was conducted on the frictional properties of the two types of CNCs using a UMT reciprocating friction tester. The results indicate that both types of CNC exhibit significant friction reduction properties at various additive concentrations, provided the addition does not exceed w=1 %. When below their respective liquid crystalline phase concentrations, the friction reduction performance of S-CNC is slightly inferior to that of C-CNC; however, when above the liquid crystalline phase concentration, the friction reduction performance of S-CNC surpasses that of C-CNC. The addition of w=0.5 % S-CNC leads to a relative reduction of 63.4 % in the friction coefficient compared to the base system. Analysis of the steel plate surface contact angle and post-wear surface suggests that the lubrication mechanism of CNC involves the adsorption of polar functional groups such as hydroxyl or carboxyl groups from the CNC structure onto the friction pair surface, forming a lubricating protective film to varying degrees. Additionally, the liquid crystalline structure of S-CNC facilitates the formation of an ordered lubricating film, further enhancing the frictional properties. These findings provide valuable insights into the application of nanocellulose crystals as lubricant additives.

Microstructural analysis and tribological characteristics of thermally sprayed Co-Ni-O ternary oxide coatings

Due to their high thermal and chemical stability, ternary oxide coatings have been extensively investigated as potential solutions for high-temperature solid lubrication. In this study, the tribological behavior of the thermally sprayed Co0.75Ni0.25O and Co0.5Ni0.5O oxide coatings was investigated. The dry sliding reciprocating friction tests were performed against an Al2O3 counterface at room and elevated temperatures using a ball-on-flat tribometer. The results indicated that the friction and wear of Co0.75Ni0.25O oxide coatings did not change significantly at atmospheric and elevated temperature conditions, whereas the friction and wear of the Co0.5Ni0.5O increased at elevated temperatures. The correlations between the worn surface morphologies, the subsurface microstructure induced by wear, and the wear behavior of the coatings were discussed based on the characterizations, (i.e., microhardness, scanning electron microscopy (SEM), and electron channeling contrast imaging (ECCI)).

Probing the effect of displacement on electrical contact tribological behavior at the risk frequency of nuclear safety DCS equipment

Purpose This paper aims to study the tribological characteristics of the electrical contact system under different displacement amplitudes. Design/methodology/approach First, the risk frequency of real nuclear safety distributed control system (DCS) equipment is evaluated. Subsequently, a reciprocating friction test device which is characterized by a ball-on-flat configuration is established, and a series of current-carrying tribological tests are carried out at this risk frequency. Findings At risk frequency and larger displacement amplitude, the friction coefficient visibly rises. The reliability of the electrical contact system declines as amplitude increases. The wear morphology analysis shows that the wear rate increases significantly and the degree of interface wear intensifies at a larger amplitude. The wear area occupied by the third body layer increases sharply, and the appearance of plateaus on the surface leads to the increase of friction coefficient and contact resistance. EDS analysis suggests that oxygen elements progressively arise in the third layer as a result of increased air exposure brought on by larger displacement amplitude. Originality/value Results are significant for recognizing the tribological properties of electrical connectors in nuclear power control systems. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-03-2024-0098/

The Preparation of Crumpled Graphene Oxide Balls and Research in Tribological Properties.

In this study, crumpled graphene oxide balls (CGBs) were prepared via capillary compression using a rapidly evaporating aerosol droplet method. The CGBs were observed using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), and Raman spectroscopy. The size distributions of crumpled particles were obtained using a laser nanometer particle size analyzer (DLS). The dispersibility of the water and the ionic liquid (IL) was tested by ultrasonic dispersion. The tribological properties of water or ionic liquids containing crumpled graphene oxide ball additives (W/IL-CGB) were tested by a reciprocating friction tester and compared with water/ionic liquids with graphene oxide. The morphology of the wear scar was observed by a three-dimensional optical microscope and its lubrication mechanism was analyzed. The results show that the CGBs were successfully prepared by rapid evaporation of aerosol droplets, and the obtained CGBs were crumpled paper spheres. The CGBs had good water dispersion and ionic liquid dispersion, and IL-CGB has excellent anti-friction and anti-wear effects on steel-steel friction pairs. During the friction process, the CGB was adsorbed at the interface of the steel-steel friction pair to form a protective layer, which avoids the direct contact of the friction pair, thereby reducing friction and wear.

Insight into the tribological properties of cylinder liner-piston ring under the nano BNNs/Cu composite additive lubrication

To improve the tribological properties of the cylinder liner-piston ring, a two-dimensional hexagonal boron nitride/copper composite lubricant additive was prepared and characterized in detail. The tribological properties and lubrication mechanism of nano hexagonal boron nitride composites with different concentrations were studied through the reciprocating friction test on the Rtec friction and wear tester. The results show that copper is successfully reduced and attached to the surface of h-BN nanosheets through the self-polymerization of dopamine, and the spherical structure promotes the interlayer slip of the nanosheets during the reciprocating friction process. The appropriate concentration of nano composite additives has excellent anti-friction and anti-wear properties. At 1 Hz and 100 N, the friction coefficient and wear quality of the nano composite additive with a concentration of 2 wt% were reduced by 29.07% and 76%, respectively. The surface Sq value and Sz value of the cylinder liner sample decreased by 68.06% and 74.47%. At the same time, under the condition of high speed and heavy load, the average wear depth of the cylinder liner sample is reduced by 61.3%. The nano composite material additive forms an excellent friction protective film on the wear surface of the cylinder liner, which can better enter the wear surface of the cylinder liner and produce a filling and repairing effect. The research results provide a method for the use of nano hexagonal boron nitride composite additives to inhibit the wear of cylinder liner-piston ring of Marine diesel engines.

Enhancement of mechanical and tribological properties of hot-pressed B4C ceramics by CeB6 addition

B4C–CeB6 composites were prepared via hot pressing using CeB6 powder as an additive and with varying CeB6 contents ranging from 0 to 5 vol%. The effects of CeB6 content on the microstructure, mechanical properties, and tribological properties of the composites were investigated. The introduced CeB6 did not participate in any chemical reactions during sintering and existed only as a second phase in the B4C matrix. When the volume fraction of the added CeB6 was less than or equal to 1 %, the second phase was uniformly distributed in the matrix, which refines the B4C grains. The high thermal conductivity of CeB6 facilitates efficient heat transfer, contributing to the formation of densely sintered bodies. Additionally, the residual stress at the grain boundary resulting from the difference in the thermal expansion coefficients of the two particles promotes crack deflection and branching, thereby enhancing the toughness of the composite. When the CeB6 content is 1 vol%, the composite exhibits optimal comprehensive mechanical properties, with the density, Vickers hardness, flexural strength, and fracture toughness reaching 99.49 %, 31.57 GPa, 643.2 MPa, and 4.27 MPa m1/2, respectively. In the dry reciprocating friction test, the wear rate after a 30-min sliding test used an Al2O3 ball under a load of 15 N was only 0.98 × 10−6 mm3 N−1 m−1. These comprehensive properties make B4C–CeB6 composites very attractive candidates for various applications.

Superlubricating UHMWPE composites with functionalized carbon nanotubes reinforcement applicable to artificial joints

Polyelectrolyte-grafted ultra-high-molecular-weight polyethylene (UHMWPE) has been proven efficient in friction and wear reduction. However, owing to the damaged molecular structure and material stability, the modified material experiences compromised mechanical and tribological properties under immersed, aqueous working environment. To achieve enhanced material strength and water resistance, carbon nanotubes (CNTs) were modified and used as reinforcing agent. Nanoindentation tests and macroscopic reciprocating friction tests have shown significant improvements in mechanical and tribological properties: friction coefficient and wear rate down to 0.0086 and 5.6 × 10−8 mm3(Nm)-1 under saline-lubricated conditions, which maintained relatively stable during 120-day saline pre-soaking. This combination of strong hydration lubrication and superior material strength offers a promising design of superlubricating artificial cartilage with high wear resistance and long lifetime.

Investigation on the tribological properties of different coatings of cutting tool with reciprocating friction test

Investigation on the tribological properties of different coatings of cutting tool with reciprocating friction test

Use of Functionalized Graphene-Based Materials on Grease

The growing awareness of reduced friction losses and new demands for electrical powertrains demand improved lubricants. Due to their unique properties, such as high thermal and electrical conductivity, graphene and its derivatives have been investigated for tribological applications, especially as lubricant additives. In this work, we investigated three commercially available graphene variants, one comprising a few layers and the other two comprising nanoplates, after functionalization as additives to lithium soap grease. The grease temperature dropping point increased by approximately 6 °C. Additionally, during the reciprocating friction test, friction increased with the test duration for the baseline grease, whereas it decreased for the ones containing graphene-based additives. On the test end, friction was reduced by 8% compared to the baseline grease. On a four-ball tribometer, the wear scar was reduced from 10 to 18% compared to the baseline grease. In general, no significant difference was seen between the three graphene-based variants. The promising results found with graphene nanoplates, a less expensive material than a few graphene layers, creates opportunities for a cost-competitive additive to commercial greases.

Aluminum Chromium Nitride Coating on a Laser Shock Micro-Molded Surface of E690 High-Strength Steel and Its Antifriction Mechanism

Aiming its analysis at the poor hardness and wear-resistance of E690 high-strength steel, and the high hardness and good wear-resistance of AlCrN-coated, combined with the laser impact micro-modeling which can store oil lubrication, this paper carries out research on the synergistic wear reduction mechanism of laser impact micro-modeling AlCrN coated on the surface of E690 high-strength steel. Multi-arc ion plating technology is used to prepare the AlCrN coating on the laser-impact micro-modeling specimen; the micro-modeling AlCrN-coated specimen is subjected to a reciprocating friction test, and the hardness and residual stress of the coated surface are measured by equipment such as a residual stress meter and a microhardness tester. The microstructure and physical elements of the surface wear before and after the preparation of the coating are analyzed by scanning electron microscope (SEM), confocal three-dimensional morphometer and XRD diffractometer, respectively. The results show that the prepared AlCrN-coated materials were well-bonded to the substrate. Compared with the micro-molding-only specimens, the average friction coefficient and wear amount of the micro-molded AlCrN-coated specimens with different micro-molding densities and depths decreased compared with the micro-molded specimens; among them, the average friction coefficient of the specimens with a micro-molding density of 19.6% and a depth of 7.82 µm was 0.0936, which was the lowest. Additionally, the AlCrN coating enhances the stability of the friction process of the specimen and reduces the amount of wear of the specimen. Under the premise of ensuring the anti-wear and stability properties of the material, the best integrated friction performance was achieved at a micro-molding density of 19.6% and a depth of 24.72 µm. A synergistic wear reduction and lubrication model of micro-molding and AlCrN-coating was established.

Microstructure and tribological properties of TiSiCN composite coatings with different carbon contents deposited by plasma‐enhanced magnetron sputtering

TiSiCN composite coatings with different C contents were prepared on Cr buffer layer by plasma‐enhanced magnetron sputtering. The structure, composition, surface, and cross‐sectional morphology of the coatings were characterized by X‐ray photoelectron spectroscopy, X‐ray diffraction, Raman spectroscopy, scanning electron microscope, and atomic force microscope. The hardness, elastic modulus, and tribological performance of the coatings were evaluated by nanoindentation and reciprocating friction tests. The results showed that the TiSiCN composite coatings are amorphous structure composed of TiCN compound and microcrystalline graphite, and amorphous phases. The increase of C content changed the content and distribution of TiCN ceramics nanocrystal, amorphous Si3N4 and amorphous carbon (sp3‐ and sp2‐hybridized C), thus affecting the hardness and friction behavior of the coatings. The hardness of the composite coatings was related to the content of TiCN phase and sp3‐C in the coatings. The TiSiCN composite coating with C content of 68.2% had lower coefficient of friction and the lowest wear rate.

Study on Friction Characteristics of AA7075 Aluminum Alloy under Pulse Current-Assisted Hot Stamping

Friction during contact between metals can be very complex in pulse current-assisted forming. Based on stamping process characteristics, a reciprocating friction tester was designed to study the friction characteristics between AA7075 aluminum alloy and P20 steel under different current densities. Origin software was used to process the experimental data, and a current friction coefficient model was established for the pulse current densities. The results show that the friction coefficient of the aluminum alloy sheet decreased with the increase in the pulse current density (2–10 A/mm2). After that, the friction mechanism was determined by observing microscopic morphology and SEM: some oxide cracked on the friction surface when the current was large. Finally, finite element simulations with Abaqus software and a cylindrical case validated the constant and current friction coefficient models. The thickness distribution patterns of the fixed friction coefficient and the current coefficient model were compared with an actual cylindrical drawing part. The results indicate that the new current friction model had a better fit than the fixed one. The simulation results are consistent with the actual verification results. The maximum thinning was at the corner of the stamping die, which improved the simulation accuracy by 7.31%. This indicates the effectiveness of the pulse current friction model.

Effect of High-Energy Shot Peening on Properties of High-Velocity Oxygen-Fuel Spraying

A Cr3C2-Al2O3-NiCr composite coating was prepared on an INCONEL600 alloy surface through high-velocity oxygen-fuel spraying followed by further processing through high-energy shot peening to create the composite coating. The microhardness and friction properties of the composite coating are analyzed by a microhardness tester and reciprocating friction tester. The microscopic structure and wear trace of the composite coating were analyzed by scanning electron microscope (SEM). The element distribution of the coating was analyzed by energy-dispersive spectroscopy (EDS). The porosity of the coating was detected by industrial CT. The phase and residual stress of the coating were tested by X-ray diffraction (XRD). The electrochemical corrosion and friction wear performance of the samples under different surface states were discussed. The results showed that the compactness of the coating was improved and the porosity was significantly reduced after high-energy shot peening. The high-energy shot peening did not alter the phase composition of the coating but introduced residual compressive stress. The microhardness of theCr3C2-Al2O3-NiCr high-velocity oxygen-fuel coating can reach 2.9 times that of the INCONEL600 substrate, and the hardness of the coating after high-energy shot peening can reach 3.9 times of that of the substrate. After high-energy shot peening, the corrosion resistance of the coating in HCl solution is improved. Compared with the INCONEL600 substrate, the friction coefficient and calculated wear rate of the Cr3C2-Al2O3-NiCr high-velocity oxygen-fuel coating decrease by 62.5% and 79.6%, respectively. After high-energy shot peening, the friction coefficient and calculated wear rate of the coating decrease by 75% and 98.7%, respectively.

Tribological Properties of Nano-ZrO2 and PEEK Reinforced PTFE Composites Based on Molecular Dynamics

Polytetrafluoroethylene (PTFE) is a polymeric material with excellent self-lubricating properties. In this study, in order to improve the wear resistance of PTFE, the PTFE matrix was filled with soft-phase polyetheretherketone (PEEK) particles and hard-phase nano-ZrO2 particles in varying volume ratios. A linear reciprocating friction tester was used to test the tribological properties of the PTFE composites. Optical microscopy (OM) and scanning electron microscopy (SEM) were utilized to observe the formation and evolution of the transfer film on the surface of the counterpart metal during the friction process. Molecular dynamics simulation software (Materials Studio MS) was used to simulate and analyze the frictional behavior between the molecular structures of PTFE composites and the counterpart iron atoms on a microscopic scale. The results showed that the uniformity and firmness of the transfer film had an important influence on the wear resistance of the material. PEEK and ZrO2 nanoparticles were able to improve the firmness and formation rate of the transfer film, respectively, resulting in significant improvement in the wear resistance of PTFE (volume wear rate reduced from 7.7 × 10−4 mm3/Nm for pure PTFE to 1.76 × 10−6 mm3/Nm for nano-ZrO2/PEEK/PTFE). Molecular dynamics simulations revealed that the poor wear resistance of PTFE was due to significant interlayer slippage within its molecular chains. PEEK molecular chains could effectively adsorb PTFE molecular chains and formed a strong bond. ZrO2 nanoparticles also contributed to the overall stability of the PTFE matrix. Both soft and hard fillers significantly inhibited interlayer slippage between PTFE molecular chains, enhancing the shear deformation resistance of the material and thus improving the wear resistance of PTFE composites.

Enhanced lubrication by core-shell TiO2 nanoparticles modified with PEG-400

PurposeThe purpose of this paper is to enhance the characteristics of TiO2 nanoparticles (NPs). Because these NPs stick together easily and are difficult to distribute evenly, they cannot be used extensively in lubricating oils. Altering TiO2 was recommended as an alternate way for making NPs simpler to disperse.Design/methodology/approachThrough dielectric barrier discharge plasma (DBDP)-assisted ball mill diagnostics and modeling of molecular dynamics, TiO2@PEG-400 NPs were produced using the DBDP-assisted ball mill. The NPs’ microstructure was examined using FESEM, TEM, XRD, FT-IR and TG-DSC. Using the CFT-1 reciprocating friction tester, the tribological properties of TiO2@PEG-400 NPs as base oil additives were studied. EDS and XPS were used to examine the surface wear of the friction pair.FindingsTribological properties of the modified NPs are vastly superior to those of the original NPs, and the lipophilicity value of TiO2 NPs was improved by 200%. It was determined through tribological testing that TiO2@PEG-400’s exceptional performance might be attributable to a chemical reaction film made up of TiO2, Fe2O3, iron oxide and other organic chemicals.Originality/valueThis work describes an approach for preventing the aggregation of TiO2 NPs by coating their surface with PEG-400. In addition, the prepared NPs can enhance the tribological performance of lubricating oil. This low-cost, high-performance lubricant additive has tremendous promise for usage in marine engines to minimize operating costs while preserving navigational safety.

Effect of Erucamide as Polyurea Grease Additive on Tribological Properties of GCr15 Steel

To investigate the effect of erucamide on the tribological properties of GCr15 steel in this study, polyurea grease is prepared with different concentrations of erucamide as additive. The tribological behavior of erucamide on the surface of GCr15 steel is studied using a reciprocating friction test. The results show that 1.5 wt% erucamide has the best tribological property and friction-induced vibration and noise suppression capability. This is attributed to the formation of a lubricating film on the transition region of the friction surface, which maintains the friction in a relatively stable state, and the maximum thickness of lubricating film is 3.91 μm.

Preparation and tribological behavior of high‐temperature oil‐containing porous polyimides

AbstractThis paper aimed to attempt the fabrication of high‐temperature oil‐containing porous polyimides (OCPPIs) using as‐polymerized powder with a no processing melting point, as well as investigate its tribological behavior. The OCPPIs were fabricated using a cold‐press sintering technique containing multiple gradient processing steps. Coalescence tightly among polymer powders was successfully achieved under a high‐elastic state by extending holding time vastly based on the time–temperature equivalence principle. The results indicate that OCPPIs possessed a high performance of oil retention after centrifuging in rotation 6000 r/min within 120 min whether low or high porosity. The tribological behaviors were evaluated by reciprocating friction tests under point‐contact conditions. Surprisingly, the tribological properties showed counterintuitive performance, wherein the best performance on the anti‐friction and wear resistance is encountered for the PPIs with the lowest porosity due to the excellent mechanical performance. The corresponding tribological mechanism with respect to multi‐phase wear and liquid–solid lubrication was also discussed comprehensively. This work fills the gap with respect to the fabrication of high‐temperature oil reservoirs and contributes to further understanding the forming mechanisms of porous materials under a high‐elastic state.

Mechanical and Tribological Behaviors of U75VG Rail Flash−Butt Welded Joint

Flash−butt welded rail is widely used in railway transportation; however, the welded joint is vulnerable after a long time of service, and its damage mechanism is controversial. Here, tensile and reciprocating friction tests were carried out to analyze the mechanical and tribological behaviors between the welded joint and the base metal of a U75VG rail. The results show that flash−butt welding promotes the pearlite to transform into ferrite, leading to a relatively low hardness value but high plasticity. In addition, the yielding and strength of the all−weld−metal specimen are 385 MPa and 1090 MPa, respectively, which are about 24.51% and 7.63% lower than that of the base metal specimen. It is worth noting that the elongation of the all−weld−metal specimen is 57.1% higher than that of the base metal specimen, and more dimples and tearing ridges can be detected on the fracture morphology of the all−weld−metal specimen, while the fracture morphology of the base metal specimen is filled with shallow dimples and cleavage planes. Moreover, the weld metal has a relatively higher COF (coefficient of friction), and its fluctuation amplitude is 1.25 times higher than that of the base metal, which is due to the rougher worn surface. Furthermore, the introduction of flash−butt welding changes the wear mechanism of the U75VG rail from adhesive wear and oxidation to fatigue wear and slight oxidation, and ultimately leads to more serious damage.