Wear Scar Width Research Articles

Study on the Performance of Different Crystal Forms Nano MoS2 as Lubricant Additives in Reducing Wear and Friction

ABSTRACTIn order to investigate the anti‐friction and anti‐wear performance of different crystal forms nano MoS2 in paraffin oil. Freeze‐drying method combined with hydrothermal was used to prepare different crystal forms nano MoS2 and their microstructures were characterised by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). The anti‐friction and anti‐wear performance of MoS2 nanoparticles as lubricat additives under different working conditions was investigated by the ball‐and‐disk friction and wear testing machine and the mechanism of friction and wear reduction was investigated. The results showed that the thickness of the floral sheet MoS2 flakes was about 10 nm and the particle size of the spherical MoS2 was about 90 nm. When the addition concentration was 3 wt%, the friction coefficient of the floral sheet MoS2 in paraffin oil was lower at 0.094, which was 29.3% lower than that of the pure paraffin oil, the width of the abrasion marks was 24.2% lower than that of the pure paraffin oil and the wear rate was 71.6% lower than that of the pure paraffin oil; The friction coefficient of the spherical MoS2 with 2.5 wt% addition was 0.082, which was 38.3% lower than the friction coefficient of pure paraffin oil, 24.1% lower than that of paraffin oil in terms of wear scar width and 81.9% lower than that of paraffin oil in terms of wear rate.

Prediction of Grease Performance and Optimal Additive Ratio Based on the SSA-GDA-LSSVM Model

In this paper, to address the issue of compounding three additives in PTFE grease, we propose a machine learning model based on SSA-GDA-LSSVM to predict both the tribological performance and the optimal ratio of additives in PTFE grease. Gaussian data augmentation expanded the experimental data, and the Sparrow Algorithm optimized hyperparameters of the Least Squares Support Vector Machine. SHAP analysis clarified model predictions, and a Non-Dominated Sorting Genetic Algorithm identified optimal additive ratios, which were experimentally validated. The results showed that the model predicted friction coefficients and wear scar widths with R² values exceeding 0.97, and the experimental error for optimal ratios was less than 1%.

Influence of fatty acid composition on contact angle and wear rate of Jatropha curcas and sunflower’s mixture by varying compositions mixture

United Nation Sustainable Development Goals make sustainability become common goals which drives into investments of innovative product and technology focusing on sustainability. Cutting oils are generally made from mineral oil and the renewable replacement is sought after and one of them are Jatropha curcas and sunflower oil or blend of them. Viscosity and adsorption will influence the properties of cutting oil. The study concern on the relationship between percentage of JCO in the mixture to anti-wear properties and contact angle measured using goniometer contact angle and pin-on-disk tribometer by varying percentage of Jatropha curcas oil in mixtures for 2.5 %, 5 %, 10 %, 20 %, and 30 %. Also, molecular simulation is conducted through molecular dynamic in search of dipole moment, electrostatic potential, polarizability and bond energy. The approach is employed to connect molecular interaction and non-linearity trending of experiment. The experiment shows contact angle and wear scar width and also wear rate become higher when percentage of Jatropha curcas oil is higher. The lowest contact angle is 26.9 deg. and the highest is 36.9 deg. of 2.5 % and 30 % Jatropha oil. The highest wear rate is 6.77e-7 and the lowest is 2.74e-7 of 2.5 % and 30 % Jatropha oil. The simulation gives supporting basis in the finding of experiment in which the viscosity is more prominent in governing wear rate than adsorption. Increases of Jatropha curcas percentages have inversely proportional to dipole moment, polarizability, electrostatic potential and bonding which explain why the fatty acids become more adhere to the fatty acid than to surface. The finding is restricted only for idealized conditions both of molecular structure and surface.

Improved wear and corrosion protection of Ni–P alloy coating by an electrodeposited Ni–Co–P alloy coating

To improve the comprehensive protection performances of steel C1045 surface, the Ni–Co–P alloy coatings with varying CoSO4·7 H2O concentration (0, 10, 20, 30, 40, 50, 60 and 70 g·L–1) were successfully prepared by an electrodeposition technique on a steel C1045 surface. The effect of the addition of CoSO4·7 H2O in the plating solution on the surface microstructure, elemental composition, crystallite size, microhardness, wear and corrosion resistance of the Ni–Co–P alloy coatings were analyzed by using a scanning electron microscope, an energy dispersive spectroscopy, an X-ray diffraction, a microhardness tester, a friction wear tester and an electrochemical workstation, respectively. The results indicated that the Ni–Co–P alloy coating exhibited a flatter morphology, compact microstructure and more excellent properties compared with Ni–P alloy coating, and the addition and variation of CoSO4·7 H2O in the plating solution had significant effects on the surface microstructure and comprehensive protection performances Ni–Co–P alloy coating. Notably, when the mass concentration of CoSO4·7 H2O in the plating solution was 50 g·L–1, the Ni–Co–P alloy coating had the highest content of Co element (22.67 wt·%), smallest crystallite size (20.41 nm) and highest microhardness (716.2 HV0.1). Furthermore, its wear resistance and corrosion resistance were considerably improved compared to that of the Ni–P alloy coating. The minimum average dynamic friction coefficient, wear scar width and depth of Ni–Co–P alloy coating at 50 g·L–1 were 0.47±0.02, 450.9 µm and 14.1 µm, respectively. The corrosion current density (Icorr) of Ni–Co–P alloy coating was the smallest (0.68 µA·cm–2), the corrosion rate (Rcorr) was slowest (8.25 µm·year–1), and the polarization resistance (Rp) of the Ni–Co–P alloy coating was highest (29.83 kΩ·cm2). The corrosion resistance of Ni–Co–P alloy coating was best.

Utilizing cellulose nanofibers to enhance spent engine oil performance: A sustainable environmental solution

Spent engine oil is a major source of environmental pollution that affects the aquatic ecosystem and human health. Cellulose nanofibers (CNF) are natural nanomaterials that can be used as additives in spent engine oil to enhance its performance, especially at high temperatures and pressures. Utilizing sulfur-based unbleached rice straw pulping technique, the rice straw was grinded in a solution with 10 % sodium sulfite and 2 % sodium carbonate, that heated to 160 °C for 2 h. This produces unbleached sulfur pulp, which is then analyzed for ash, cellulose, and lignin content. A subsequent bleaching step at 80 °C with a sodium chlorite/acetic acid mix completes the process. This technique was adopted to produce CNF. In this study, preparation and characteriztion of CNF-additives to spent engine oil was performed using different techniquessuch as; IR spectra analysis, kinematic viscosity, and wear scar width. It was also evaluated on the oil adsorption, vibration, and noise reduction properties of the resulted additive oil. The results showed that CNF improved viscosity, lubrication, and anti-wear properties of the oil, and decreased its friction, vibration, and noise. The optimal concentration of CNF was 2.0 wt%, which increased the kinematic viscosity by 14.5 % and reduced the wear scar width by 31 % compared to the spent oil sample. Moreovere, CNF reduced the environmental impact of oil disposal and recycling. Overall, CNF are promising nanofillers for improving the performance of spent engine oil and lowering its environmental impact.

A Polytetrafluoroethylene@Polyacrylonitrile core-shell composite with high tribological performance

As a lubricating additive, polytetrafluoroethylene (PTFE) exhibited poor wear resistance, high wear rate and weak adhesion strength, which restricted its application in the area of lubrication and wear protection. In this paper, we prepared a PTFE-based core-shell composite (PTFE@PAN) composed of PTFE core and polyacrylonitrile (PAN) shell through an emulsion polymerization method. The PTFE core with diameter of about 80–100 nm was wrapped by the PAN shell with the thickness of about 50–60 nm. The PTFE@PAN core-shell composite present better dispersion stability in lubricating oil (poly-α-olefin 6, PAO6) than PTFE. Additionally, the PTFE@PAN composite dispersed in PAO6 exhibited significantly reduction in friction coefficient and wear scar width up to 50 % and 25 % compared to PTFE, respectively. Meanwhile, the wear volume of PTFE@PAN composite under a load of 200 N was 4.855 × 104 μm3, was merely one twenty-seventh of that of PTFE (130.6 × 104 μm3). In comparison to conventional oil lubricants, this enhanced tribological properties of PTFE@PAN composite were conducive to a homogeneous transfer film composed of the dual-phase hard polymer (PAN) and soft PTFE polymer (PTFE). Compared with PTFE, the lower surface hardness and better flexibility of PAN shell led to deformation and gap filling with the entanglement and motion of the molecular chains, which could reduce the scratches and decline the abrasive wear of the rubbing surface significantly in the course of the friction process on a rough surface under the high load. That results also suggested that the PTFE@PAN core-shell composite will be a potential lubricating and wear-resistant additive.

Tribological evaluation of electric vehicle driveline lubricants in an electrified environment

Electrification continues to permeate the automotive industry, with future projections showing an exponential growth in the market share for both light and heavy-duty applications. Existing test methods for automotive applications were developed to model internal combustion engine vehicles and drivelines and are not appropriate for electric drivelines that experience stray electric currents. Tribometers can be used to evaluate friction and wear on modeled surfaces simulating in-vehicle operation. In this work, a commercially available tribometer was modified to isolate an electrical input into a tribological contact. After necessary modifications to the tribometer, a test matrix was completed for investigating different temperatures, load conditions, speed conditions, voltage input types, frequencies of AC signal, and shapes of AC signal. These parameters were tested on three lubricants—two typical automatic transmission fluid formulations and gear oil used in differential applications. Friction was measured throughout the tests, and wear scar width was measured at the end of each test. Results indicated that temperature, DC voltage, AC frequency, lubricant, and test profile had statistically significant differences in wear scar width. For electrical parameters, AC frequency produced different results from DC voltage when no voltage was applied. This significance applied to only one lubricant, with the other two lubricants having mixed results.

Experimental investigation to assess the effect of graphene blended lithium grease on friction, wear, and surface morphology of 52100 chrome alloy steel contacts

AbstractThe results of a research on the tribological behaviour of lithium grease with the addition of graphene nanoparticles are presented in current work. Using a four‐ball tribometer, the wear and friction coefficient of lithium grease and blended grease samples with graphene additions were assessed. The significance of graphene in enhancing the tribological properties of grease materials is evident from experimental results. In the experimental investigation, a considerable decrease in wear and friction co‐efficient values was also noted. One weight percent addition of graphene to base grease decreases friction by 23.73% and wear scar width by 19.51%.

Effect of laser shock peening on plasma nitriding microstructure and properties of H13 steel

Laser shock peening (LSP) was conducted on H13 steel prior to plasma nitriding (PN). The optical microscopy (OP), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), microhardness tester and ball-on-disk wear tester were employed to investigate the microstructure and properties of plasma nitrided H13 steel coupled with LSP processing. The results show that a large number of dislocations, as well as dislocation cells and nanocrystals composed of high-density dislocations, are observed in H13 steel after LSP treatment. Compared with the PN sample, the diffraction peak intensities of the Fe3N phase in the LSP + PN sample are slightly enhanced and the diffraction peaks shift to the right as a whole. Compared to the PN sample, the LSP + PN sample exhibits significant improvements in various aspects. Specifically, the white bright layer and diffusion layer of the LSP + PN sample increased by approximately 25 % and 119.4 %, respectively. Additionally, the thickness of the effective hardened layer increased by around 50 %, and the microhardness increased by approximately 31.3 %. The LSP + PN sample has the better wear resistance than that of the PN sample, with the friction coefficient, wear scar width, wear volume, and wear rate reduced by 11.1 %, 8.4 %, 7.9 %, and 7.3 %, respectively. Through parallel experiments, the experimental error is controlled within 2 %.

Phase Structure, Microstructure, Corrosion, and Wear Resistance of Al0.8CrFeCoNiCu0.5 High-Entropy Alloy

This study investigates the structure and corrosion behavior of the Al0.8CrFeCoNiCu0.5 high-entropy alloy prepared using non-consumable vacuum arc melting. XRD analysis identified BCC1 and BCC2 phases corresponding to (Fe-Cr) and Al-Ni, respectively, while the FCC phase aligned with Cu. SEM and EBSD observations confirmed an equiaxed grain structure with fishbone-like morphology at grain boundaries and modulated structures within the grains. The alloy exhibited minimal residual stress and strain. The alloy demonstrated a preferred orientation of grain growth along the <001> direction. Electrochemical testing in a 3.5% NaCl solution revealed a corrosion potential of −0.332 V and a corrosion current density of 2.61 × 10−6 A/cm2. The intergranular corrosion regions exhibited significant depletion of Al and Cu elements, with the corrosion products primarily consisting of Al and Cu. Al and Cu elements are susceptible to corrosion. The wear scar width of Al0.8CrFeCoNiCu0.5 high-entropy alloy is 1.65 mm, which is less than 45# steel, and high-entropy alloy has more excellent wear resistance. Given its unique attributes, this high-entropy alloy could find potential applications in high-end manufacturing industries such as the aerospace engineering, the defense industry, energy production, and chemical processing where high corrosion resistance and wear resilience are crucial.

Correlation of microstructure and bio-tribocorrosion behavior of equal channel angular pressed pure titanium

The effect of equal channel angular pressing (ECAP) strain (i.e., 1st to 4th pass) on the grain size and eventual mechanical and bio-tribocorrosion properties of commercially pure titanium (cp-Ti) has been investigated. Ultra-fine grains (UFG) of 0.8 µm size (from 12 µm) and yield strength enhancement to 785 MPa (from 381 MPa) have been observed for the ECAP 4th pass sample as compared to the annealed condition of cp-Ti. In addition, the maximum hardness increased by 101 HV to 293 HV in the 4th pass samples due to grain refinement caused by the ECAP process. Further, the tribocorrosion behaviour as a function of cp-Ti sample conditions in the simulated body fluid (SBF) has been evaluated. The ultra-fine-grained 4th pass sample shows a lower coefficient of friction (CoF) of ∼0.35 (from ∼0.5) and wear loss due to its enhanced strength than the annealed sample. Moreover, the ECAP 4th pass sample, because of its UFG, exhibits a more negative potential shift (∼0.82 V) as compared to annealed sample (∼0.88 V). However, this shift is marginal due to its low wear scar width and depth, which eventually induced less galvanic coupling effect in it. Abrasion and adhesion are the primary wear mechanisms for all the sample conditions.

Effect of SiC content on microstructural evolution and tribology properties of laser-clad TiC-reinforced Ti-Al-Si composite coatings

This work prepared (Ti-Al-Si)-X (x = 1, 2, 3, 4) coatings on TC4 alloy matrix composites by laser cladding to improve their surface mechanical properties. Meanwhile, the effect of the content of SiC added to the Ti-Al-Si system on the properties and microstructures of the original coatings was explored. The results showed that the reinforced composite coatings contained matrix phases (TiAl, Ti3Al, TiAl3) and reinforcing phases (Ti5Si3 and TiC). As SiC content increased, the matrix phases formed in the coatings showed different results on the Ti-Al-Si ternary phase diagram due to the introduction of C, a stabilizer of ɑ-Ti alloy. Meanwhile, TEM results indicated the existence of Ti5Si3 phase and Ti3Al secondary phase in the Ti-Al-Si-3 layer. Compared with the TC4 matrix, the reinforced composite coatings had higher microhardness with average values of 780.9 HV0.3, 853.9 HV0.3, 985.0 HV0.3 and 943.5 HV0.3 for the four coatings, respectively. The wear resistance of the reinforced composite coatings increased first and then decreased with increasing SiC content, which was the result of the matrix phase transformation. The Ti-Al-Si-3 coating had the highest microhardness (1092HV0.3) and wear resistance (the friction coefficient, the wear scar width and wear weight loss were 0.37, ∼0.83 mm and 1.8 mg, respectively). The above analysis and results demonstrated that the Ti-Al-Si-3 layer had superior mechanical properties compared with those of other reinforced coatings.

Antifriction and anti-wear performances of bionic lubricating fluid containing gelatin nanoparticles for artificial joint materials

The antifriction and antiwear effects of gelatin nanoparticles (GLN-NP) on artificial joint materials in bionic joint lubricant were investigated to provide a theoretical basis for the development of new bionic joint lubricant. GLN-NP was prepared by cross-linking collagen acid (type A) gelatin with glutaraldehyde by acetone method, and the particle size and stability of GLN-NP were characterized. The biomimetic joint lubricants with different concentrations were prepared by mixing 5, 15, and 30 mg/mL GLN-NP with 15 and 30 mg/mL hyaluronic acid (HA), respectively. The friction reduction and antiwear effects of the biomimetic joint lubricants on zirconia ceramics were investigated on a tribometer. The cytotoxicity of each component of bionic joint lubricant on RAW264.7 mouse macrophages was evaluated by MTT assay. The particle size of GLN-NP was about 139 nm, and the particle size distribution index was 0.17, showing a single peak, indicating that the particle size of GLN-NP was uniform. In complete culture medium, pH7.4 PBS, and deionized water at simulated body temperature, the particle size of GLN-NP did not change more than 10 nm with time, indicating that GLN-NP had good dispersion stability and did not aggregate. Compared with 15 mg/mL HA, 30 mg/mL HA, and normal saline, the friction coefficient, wear scar depth, width, and wear volume were significantly reduced by adding different concentrations of GLN-NP ( P<0.05); there was no significant difference between different concentrations of GLN-NP ( P>0.05). Biocompatibility test showed that the cell survival rate of GLN-NP, HA, and HA+GLN-NP solution decreased slightly with the increase of concentration, but the cell survival rate was more than 90%, and there was no significant difference between groups ( P>0.05). The bionic joint fluid containing GLN-NP has good antifriction and antiwear effect. Among them, GLN-NP saline solution without HA has the best antifriction and antiwear effect.

Preparation and characterization of Ni-P-Al2O3-PTFE nanocomposite coatings by unidirectional jet electrodeposition

In order to improve the wear resistance and toughness of the surface of mechanical parts, Ni-P-Al2O3-PTFE nanocomposite coatings were prepared by jet electrodeposition, and a new method of unidirectional deposition was proposed. Meanwhile, the effect of current density on the surface quality and mechanical properties of nanocomposite coatings obtained by unidirectional jet electrodeposition was studied. The phase structure, surface morphology and related performance of the composite coating were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), energy dispersive spectrometer (EDS), white light interferometer, friction and wear tester and nano indentation tester. The experimental results have proved that the unidirectional deposition process can significantly enhance the deposition quality. In the process of increasing the current density from 10 A/dm2 to 20 A/dm2, the comprehensive property of composite coating shows a trend of first improving and then reducing. Under the condition of adjusting the current density to the midpoint value, the nanocomposite coating demonstrates good surface morphology, the surface roughness, average wear scar width and friction coefficient are the lowest, the elastic recovery ratio (he/hmax) and the ratio of microhardness to Young's modulus (H3/E2) reach the peak value of 0.17 and 0.045 respectively, which indicates that the composite coating has excellent wear resistance and toughness.

Preparation and Investigation of Ni–Co–P Alloy Coatings Using Jet Electrodeposition with Varying Pulse Parameters

Ni–Co–P alloy coatings were successfully fabricated by jet electrodeposition with varying pulse frequencies and duty cycles in order to prolong the longevity of steel C1045 substrates. The results showed that the microstructures and properties of samples were significantly affected by pulse frequencies and duty cycles. All the samples with varying pulse frequencies and duty cycles exhibited a face-centered cubic (FCC) structure. Additionally, the average grain size of the samples reached 20.6 nm. The microhardness of the coatings was observed to first increase, and then decrease, with a rise in pulse frequencies and duty cycles. The microhardness reached 656.2 HV0.1, and the wear scar width of the coatings reached 414.4 µm at 4 kHz pulse frequency and 80% duty cycle. Additionally, the corrosion current densities (Icorr) of samples reached a minimum value of 0.74 µA·cm−2, the corrosion rates (Rcorr) reached a minimum value of 8.9 µm·year−1, and the charge transfer resistance (Rct) reached a maximum value of 8.36 × 104 Ω·cm−2, which indicated the optimal seawater corrosion resistance of the deposited coatings.

Tribological Performance for Steel–Steel Contact Interfaces Using Hybrid MWCNTs/Al2O3 Nanoparticles as Oil-Based Additives in Engines

Numerous problems occur during engine operation, such as start-up, lack of lubrication, and overheating, resulting in engine components’ wear, power loss, and fuel consumption. Nanomaterials dispersed in engine oil can play an important role in improving the tribological properties of oil lubricants. This study investigated the influence of multi-walled carbon nanotubes (MWCNTs) and aluminum oxide nanoparticles (Al2O3 NPs) as nano-additives for lubricants. Different engine oil samples were loaded with 0.5–2.0 wt% Al2O3 NPs and 0.5–1.0 wt% MWCNTs and compared with unmodified oil. The tribological performance of the nano lubricants was investigated using the four-ball test method. In addition, the wear scar in the engine was evaluated using 3D micrographs and scanning electron microscopy (SEM). The results of the sliding surfaces with hybrid MWCNTs/Al2O3 NPs showed better friction performance and wear resistance. The coefficient of friction (COF) and wear scar width were improved by 47.9% and 51.5%, respectively, compared with unmodified oil.

Effect of Surface Roughness and Particle Size on Lubrication Mechanisms of SiO2 Nanoparticles

In this study, a series of tribological tests were conducted on a pin-on-disc tester to study the lubrication mechanism of SiO2 nanoparticles under different surface roughness considering various loads and velocities. For a comprehensive understanding of the mechanism of SiO2 nanoparticles, base fluid was also employed as a contrast. Results show that the reductions of friction coefficients and wear scar widths increase with the decrease of surface roughness, due to the increase in rolling effect and self-repairing mechanism of SiO2 nanoparticles. The lubrication mechanism of SiO2 nanoparticles is the rolling effect when the height-diameter ratio (λ) is less than 6, and the self-repairing mechanism at λ of 6 and 10, whereas, there is no obvious difference by adding nanoparticles when λ is 20. When the height-diameter ratio is less than 6, surface wears show an increasing trend as the load increases due to the high hardness of nanoparticles, while it is the opposite at λ of 10 and 20 because of the self-repairing mechanism.

Microstructure and Wear Behavior of Laser Cladded CoCrNiMox Coatings on the Low Carbon Steel

In this study, CoCrNiMox (x = 0, 1, 3 and 5, wt.%) alloy coatings were fabricated on the surface of low carbon steel by laser surface cladding. The scanning electron microscope (SEM), energy dispersive spectrometer (EDS), and X-ray diffraction (XRD) were used to analyze the microstructure and phases of the prepared coatings. The microhardness and wear resistance of these coating were also evaluated. The results showeded that a single-phase face-centered cubic (FCC) structure generated by the CoCrNi ternary compound in all the coatings, the σ phase, and the Mu (μ) phase, enriched with Cr and Mo and originated with additional Mo, exhibited a lamellar structure. The content of FCC single-phase structure in the coating gradually decreases with the increasing of Mo because the addition of Mo can promote the precipitation of the σ phase and the μ phase. Among all the laser cladded coatings, the CoCrNiMo5 alloy coating shows the best properties, owing to the higher proportion of intermetallic compounds in the σ phase and the μ phase, which can provide enhanced performance. This exhibited the narrowest wear scar width and showed the fatigue wear mechanism.

The Influence of Sintering Pressure on the Preparation, Friction Properties, and Magnetic Properties of Ti2AlC-TiC and Ti3AlC2-TiC Composites Under High-Pressure and High-Temperature

Due to their high melting point, low density, and affordable price, TiC ceramics have emerged as one of the most promising ultrahigh temperature structural materials. However, its development and usage are severely constrained by its weak mechanical characteristics. The Ti2AlC-TiC and Ti3AlC2-TiC composites were synthesized by using the laminated metal-ceramic Ti2AlC/Ti3AlC2 as the binder, combined with high-temperature and high-pressure sintering technology (GPa order of magnitude confinement system). The thermal analysis shows that the exothermic heat of Ti/1.2Al/2TiC is less than that of 3Ti/1.2Al/2C, 2Ti/1.2Al/C, and 3Ti/1.5Al/C. The ratio of Ti/1.2Al/2TiC can suppress the thermal explosion phenomenon during the sintering process and improve the safety of the high-pressure sintering process. XRD results showed that the main composition of the sintered products was Ti2AlC-TiC at 2∼3.5 GPa and Ti3AlC2-TiC at 4∼5 GPa. As the sintering pressure increased from 2 GPa to 5 GPa, the bonding phase changed from Ti2AlC to Ti3AlC2. The thickness of the synthetic Ti3AlC2 layer is near 0.1 µm under 5 GPa. The average friction coefficient of Ti2AlC-TiC composites sintered 2 GPa with POM is as low as 0.1767, while the average friction coefficient of Ti3AlC2-TiC composites with POM increased to 0.3468∼0.3797. The wear width of Ti2AlC-TiC is lower than that of Ti3AlC2-TiC composites sintered under 4–4.5 GPa. The wear width of Ti3AlC2-TiC composites decreases following the rise of sintering pressure and is reduced to 0.3504 mm under 5 GPa. Ti2AlC-TiC and Ti3AlC2-TiC composites with PP ball counterparts have friction coefficients of 0.375 to 0.45 and worse wear resistance than that of POM balls. Ti3AlC2-TiC composites synthesized at 5 GPa with a Cu ball had the smallest friction coefficient (0.4558) and the smallest wear scar width (0.6289 mm). The friction coefficients and wear widths of synthetics with Al pairs ranged from 0.48–0.697 and 0.851–1.087 mm, respectively, and varied irregularly with increasing sintering pressure. Ti2AlC-TiC composites synthesized at 2 GPa with agate and glass pairs have coefficients of friction of 0.5 and 0.61, respectively. Abrasion widths of Ti2AlC-TiC composites synthesized at 2 GPa with agate and glass pairs were 1.3 mm and 0.72 mm, respectively. The friction coefficient of synthetics with agate and glass pairs increases with increasing sintering pressure. The magnetization and magnetization intensity of the Ti3AlC2-TiC composites are stronger than those of Ti3AlC2. Ti2AlC-TiC and Ti3AlC2-TiC composites held promise to serve in the field of ceramic grinding processing applications.

Investigation on the electrical conductivity and tribological properties of NbSe2-doped lubricating grease

Developing lubricants with good electrical conductivity and good tribological properties is necessary for the power equipment. Here, niobium selenide (NbSe2) and boron nitride (BN) were employed to act as additives to fabricate the lubricating greases with superior electrical conductivity and tribological properties. The lubricating grease containing different concentrations of additives were synthesized and their conductivities were measured by a volume resistance meter at the room temperature of about 25 °C. The tribological properties of the lubricating greases were also investigated and the worn surfaces were characterized in detail by scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS) and Raman spectroscopy to analyze the lubrication mechanism after friction test. The results showed that NbSe2 could effectively reduce the volume resistivity by ten times as compared with the base grease. Tribological tests showed that when the concentration of NbSe2 was 2 wt%, it could reduce the COF and wear scar width by 23.5% and 12.8% under 150 N and 5 Hz, indicating 2 wt% NbSe2 doped lubricating grease exhibited the outstanding tribological properties. In addition, based on the analysis of the wear surfaces, the superior tribological properties of NbSe2 grease were attributed to the effective lubricating film generated on the friction surface, which played a key role in reducing friction and anti-wear.