Tribological Mechanisms Research Articles

Studies on Tribological Characteristics and Wear Mechanisms of (TiN + TiC) Hybrid Nanocomposite Claddings Deposited on TC4-Grade Titanium Alloy Substrate by the Tungsten Inert Gas Cladding Process

Abstract This investigation explored the viability of tribological properties enhancement with the deposition of TiC + TiN nanoparticulate-reinforced hybrid composite claddings in TC4-grade titanium alloy to meet the ever-increasing functional performance requirements employed under aggressive tribological environments. The composite claddings are processed by using the tungsten inert gas cladding process. The tribological performance of the hybrid composite cladding deposition was evaluated against the claddings with simplex reinforcement compositions such as TC4/TiC and TC4/TiN composite claddings and the substrate alloy. Initially, the formation and microstructural characteristics of the composite cladding depositions are studied based on the scanning electron microscope, X-ray diffraction, and energy dispersive spectroscopic analyses to confirm their successful formation. The average microhardness achieved with the deposition of composite claddings such as TiC/TC4, TiN/TC4, and (TiC + TiN)/TC4 is 936.25 HV0.2, 858.88 HV0.2, and 1116. 72 HV0.2, respectively, while the TC4 substrate alloy is about 332.38 HV0.2. The (TiC + TiN)/TC4 hybrid composite cladding composition has shown significantly increased surface hardness which is about 30% and 18%, respectively, compared with the TiC/TC4 and TiN/TC4 composite cladding compositions while about 235% enhancement compared with the TC4 substrate alloy. Compared with the TC4 substrate alloy, the wear resistance enhancement achieved with the deposition of TiC/TC4 and TiN/TC4 composite claddings is up to 22.62% and 38.92%, respectively, while with the (TiC + TiN)/TC4 hybrid composite claddings is up to 49.87%. Similarly, the average CoF of the TC4 substrate alloy, TiC/TC4, TiN/TC4, and (TiC + TiN)/TC4 composite claddings observed are 0.76, 0.49, 0.58, and 0.44, respectively, which indicates that 36%, 23%, and 43% are the enhancements achieved with the respective composite claddings. The SEM analysis of worn surfaces of the composite claddings reveals typical wear mechanisms such as adhesive, abrasive, oxidation, and delamination that are represented by various regions identified on the generated wear maps. The adhesive and delamination wear regions are relatively wider for the TiN/TC4 composite cladding than the TiC/TC4 composite cladding. The wear mechanism of the composite cladding with multiphase TiC and TiN reinforcement particulate has shown an increased prevalence of abrasive wear as a consequence the abrasive wear region is wider while decreasing the window for adhesive and delamination wear.

Tribological performance and mechanism of the titanium fiber-SiC whisker hybrid reinforced aluminum matrix composites prepared by pressure infiltration

In this contribution, a Ti-6Al-4V fiber (Tif) and SiCw (SiCw) hybrid reinforced 5056 Al composites (Tif + SiCw/5056 Al) were fabricated, and the effects of SiC whisker contents on the microstructure, mechanical properties, and wear resistance were investigated. The mechanical properties and the hardness of the composites increased first and then decreased with the increase of SiCw contents. The optimal ratio of SiCw to titanium fibers is 3 wt%. The flexural strength of the optimal composites reached 533 MPa, and the fracture toughness reached 29.1 MPa • m1/2. Under a load of 40 N, compared with the Tif/5056 Al composites sample, the wear rate of the optimal composites sample decreased by 80.7%. The uniformly dispersed SiC whiskers promote the formation of a mechanical mixing layer (MML) on the friction surface; the wear mechanism mainly involves abrasive wear and adhesive wear.

Plasma Spraying NiCoCrAlY-Cr2O3-AgMo Coatings: Fabrication and Tribological Mechanisms

The increasing demand for high-performance aircraft engines has led to a greater emphasis being placed on advanced sealing coating technologies. Developing long-life, self-lubricating, and wear-resistant coatings is of significant research value. This study focuses on the fabrication of a novel self-lubricating and wear-resistant NiCoCrAlY-Cr2O3-AgMo composite coating. This coating was deposited onto a GH4169 substrate utilizing plasma spraying. Scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) and X-ray diffraction (XRD) methods were employed to characterize the elemental composition and microstructure of the fabricated NiCoCrAlY-Cr2O3-AgMo composite coating. Microhardness measurements across the coating cross-section indicated a gradual increase in hardness from the GH4169 substrate to the NiCoCrAlY-Cr2O3-AgMo coating. The average hardness of the GH4169 substrate was 413.92 HV0.2, while the CoNiCrAlY bonding layer region exhibited an average hardness of 467.60 HV0.2. The NiCoCrAlY-Cr2O3-AgMo coating itself demonstrated an average microhardness of 643.22 HV0.2. Room temperature friction tests indicated that the average coefficient of friction (COF) of the GH4169 substrate was 0.665. In contrast, the NiCoCrAlY-Cr2O3-AgMo coating exhibited a significantly lower average COF of 0.16, representing a 75.94% reduction compared to the uncoated GH4169 substrate. High-temperature friction tests were conducted at 400 °C, 500 °C, and 600 °C, indicating average COF values of 0.438, 0.410, and 0.268, respectively, for the NiCoCrAlY-Cr2O3-AgMo coating. Specifically, at 600 °C, the formation of a lubricious NiMoO4 tribofilm on the coating surface was observed. This tribofilm effectively reduced the wear rate of the GH605 pin to 2.78 × 10−6 mm3/N·m, highlighting the potential of the NiCoCrAlY-Cr2O3-AgMo coating to reduce wear in high-temperature sliding contact applications.

Tribological mechanisms of the synergistic effect between phosphate based ionic liquids and metal-organic frameworks

Sulfur-free green lubricant additives have received more attention in industrial production. In this study, tri-octyldodecyl phosphonium diisooctyl phosphate （P/P）with UiO-66 composite environmentally friendly lubricating additives were synthesized. The tribological properties of P/P with UiO-66 composite additive in polyalphaolefin-6 (PAO-6) heavy were systematically conducted. The outcomes showed that 1 % P/P@3000 UiO-66 additive had excellent friction reduction and antiwear properties. This was mainly due to the adsorption of oil-soluble P/P on the surface and within the pores of UiO-66, which effectively reduced the tendency of agglomeration of UiO-66 formed a good synergistic effect. Consequently, a favorable and stable balling effect was achieved, thereby preserving the integrity of the lubricant film, resulting in significantly reducing wear from shear and abrasive.

Establishing high temperature tribological performance and wear mechanism map of engineered in-situ TiB2 reinforced Mg-RE metal matrix composites

The high temperature sliding wear behavior of microstructurally engineering in-situ sub-micron sized TiB2 reinforced ZE41 composite was studied and compared with it’s base counterpart at varying loading conditions. The wear mechanism maps were constructed by correlating the microstructures of worn surfaces with different test parameters. The severe and catastrophic wear mechanisms like delamination and melt wear were wider in base and composite, while in the case of engineered composite, these zones are significantly narrow down. Due to the presence of thermally stable in-situ TiB2 particles and bimodal precipitates in engineered composite, the material showed sufficient resistance against wear induced deformation. Furthermore, the study established scientific knowhow on high-temperature wear induced deformation behavior by analyzing microstructural evolution in wear subsurface zone.

Study of the Impact of Surface Topography on Wear Resistance

The surface texture parameter is a real reflection of the surface topography, which is closely related to the tribological properties of the surface, and the study of the correlation between the surface texture parameter and wear resistance is of great significance in revealing the tribological influence mechanism of the surface and realising the functional manufacturing of the surface. This paper takes the ball-end milling surface as the research object, establishes the three-dimensional simulation model of the surface topography, and analyses the surface topography and the surface texture parameter change rule. Based on the improved correlation analysis model, the correlation characteristics between the surface texture parameters, and between the surface texture parameters and the relative wear rate of per unit sliding distance KV, were investigated, and the prediction model of KV was established based on the surface texture parameters Sku, Sa, Sxp, Sp, and Ssk, and the correctness of the model was verified by experiments. The study in this paper provides a new idea to further reveal the relationship between surface topographical features and wear resistance and to guide the functional manufacturing of surfaces.

Study on fluid dynamic lubrication numerical analysis and surface topography design of slipper pair of valve distribution piston pump

In order to improve the fluid dynamic lubrication performance of slipper pair of valve distribution (digital distribution) axial piston pump, this paper proposes a theory analytical model of fluid dynamic lubrication for slipper pairs with different surface structures of valve distribution pump and its tribological optimization mechanism of surface microstructure topography. In the model, based on the finite volume method, the least square method combined with the trust region dogleg was proposed to solve the nonlinear system of equations of slipper dynamic balance. The fluid lubrication mechanism of slipper pairs with different surface structures was analyzed, the probability of overturning and eccentric wear of slipper pairs with complex surface structure and the viscous friction torque were quantitatively analyzed, and experimental research was conducted. The results show that the surface microstructure topography has great influence on the fluid lubrication performance of slipper pairs. Compared with before optimization, the friction torque of slipper with single-support belt, double-support belt, and four-support belt is decreased by 8.58%, 13.65%, and 17.07% at most, respectively, but the probability of overturning and eccentric wear of slipper with double-support belt and four-support belt is increased and the oil film becomes thicker. Reducing the friction loss and enhancing the anti-overturning ability of the slipper pair are often difficult to be compatible. The research results lay a theoretical and technical foundation for the optimization of lubrication performance of slipper pair of valve distribution pump.

Surface mechanical rolling treatment-introduced gradient nanostructured Inconel 625 alloy with enhanced high-temperature wear resistance

Heterogeneous gradient nanostructures induced through surface treatment of nickel-based superalloys hold significant promise for enhancing wear resistance. In this study, a 700 µm ultra-thick gradient nanostructured (GNS) strengthening layer was fabricated on the surface of an Inconel 625 alloy plate via surface mechanical rolling treatment (SMRT). Subsequently, the tribological behaviors and wear resistance mechanisms of coarse-grained (CG) and GNS samples at temperatures ranging from 25 ℃ to 800 ℃ were comparatively investigated. The results indicated that the gradient nanostructures significantly enhanced the high-temperature wear resistance of the samples, which wear characterized by low coefficient of friction (COF), wear rate and thin friction layer. This enhancement was attributable to the stability and excellent hot hardness of the gradient nanostructures during friction.

Tribological behavior and mechanism of Ti3SiC2/Cu composites in a wide temperature range under lubrication condition

Preparation of Ti3SiC2/Cu composites using Spark Plasma Sintering (SPS) process. The friction and wear behavior of Ti3SiC2/Cu-45# steel tribo-pair under lubrication conditions was investigated in a wide temperatures range. The results demonstrated that the influence of temperature on the tribological properties of the Ti3SiC2/Cu-45# steel tribo-pair under lubrication condition was characterized by a continuous transition from a lubricant to an oxide film. At 200 ℃, mobility of the lubricant increased and the friction interface was in the boundary lubrication state. As the temperature increased, the base oil in the lubricant rapidly evaporated, causing to solidification of the lubricant, and the friction interface formed the friction oxide film. The mechanisms of friction and wear were primarily abrasive wear and tribo-oxidation wear.

Current-carrying tribological behavior and wear mechanism of CuW composites with different W content

CuW composites are widely used in the field of electrical contacts, such as high-voltage switch and microelectronic devices, and the service life of the key components is directly affected by its wear resistance and corrosion resistance. In this paper, the effects of loading current on the tribological behavior of CuW composites with different W content were studied, focusing on the variation of friction coefficient during friction, wear rate and the wear topography of the surface after friction, and the wear mechanism was discussed. The results indicate that the friction coefficient of CuW composites was larger under energized conditions than under dry friction conditions, and that the friction coefficient first increases and then decreases with the increasing current. The main reason for the decrease in friction coefficient is that the heat generated by increasing current creates a layer of molten lubricant on the contact surface. In addition, the wear rate of the CuW composites decreased as the W content increased. When loaded with a current of 15 A, the CuW80 composites exhibited the lowest wear rate of 8 × 10−3 mg/m, which was attributed to the improved wear resistance due to the ability of the high W content to resist plastic deformation. The wear forms of CuW composites under current loading include adhesion, abrasive wear and arc erosion, and fatigue wear was also associated with long-term high current conditions.

Tribological properties and wear mechanism of Ag@Ti3C2Tx phosphate coatings from room temperature to 800 °C

MXene, a novel two-dimensional layered material, finds extensive applications in solid lubrication. However, its practical use is limited by lubrication failures at high temperatures. To increase the service temperature of Ti3C2Tx solid lubricants, phosphate lubricating coatings were prepared using Ag@Ti3C2Tx as solid lubricants, which exhibits superior tribological properties. Compared with Ti3C2Tx phosphate coating, the friction coefficient and wear rate of Ag@Ti3C2Tx phosphate coating significantly decrease between 400 °C and 800 °C. Especially at 800 ℃, the friction coefficient of Ag@Ti3C2Tx phosphate coating reaches 0.09, and the wear rate shows extremely low. This study lays the foundation for the application of Ti3C2Tx in the field of solid lubricants across a wide temperature range.

The friction behavior and wear mechanism of RV reducer gear steel (20CrMo) subjected to three different heat treatment processes from −20 °C to 100 °C

The gear friction pairs in RV reducer always withstand a broad range of temperature, sliding velocity and heavy load. In the research, three types of heat treatment methods (carburizing + quenching, nitrocarburizing and high concentration nitrocarburizing) are applied on the 20CrMo (cycloidal gear material) disc to study the tribological behavior and wear mechanism. The friction coefficient, wear depth and wear rate of the three types of friction pairs under various temperature (−20 °C, 25 °C, 50 °C, 100 °C) are measured and the microstructure characteristics are analyzed by SEM and EDS. The results reveal that high temperature can dramatically decrease the wear scar dimensions and wear rate due to the more active lubricant. Although the lubricant lost its activity at −20 °C, the friction coefficient and maximum wear depth for GCr15/20CrMo (carburizing + quenching) and GCr15/20CrMo (high concentration nitrocarburizing) are relatively less than 0.1 and 4 μm. The wear rate of GCr15/20CrMo (carburizing + quenching) and GCr15/20CrMo (high concentration nitrocarburizing) are 14.49 μm3/N·m and 17.20 μm3/N·m, which are only 28.7% and 34.1% of GCr15/20CrMo (nitrocarburizing). With the temperature increases to 25 °C, tribofilm is more likely to form on the 20CrMo specimen after nitrocarburizing, leading to better wear resistance. At high temperature (50 °C and 100 °C), GCr15/20CrMo (high concentration nitrocarburizing) system presents excellent tribological behavior by the combination of good lubricant activity, formation of tribofilm and refined nitrides. The wear rate even reaches 0.45 μm3/N·m and 0.43 μm3/N·m at the sliding velocity of 300 mm/s and 562 mm/s under 100 °C. Overall, specimen with high concentration nitrocarburizing process exhibits exceptional wear performance under full operating conditions of RV reducer.

The excellent anti-wear and friction-reducing performance of magnesium silicate hydroxide/graphite nanocomposite (MSH-C) as a lubricant additive

Abstract In this paper, MSH-C and MSH-GO composites were prepared by doping MSH with micron-sized few-layer graphene oxide (∼10 um) and nanoscale graphite (∼300 nm), respectively, during the hydrothermal synthesis process. Octadecyltrimethoxysilane (ODTMS) was used as a surfactant to disperse these two types of additives into the fully formulated oil. Tribological tests demonstrated that MSH-C exhibits much more superior tribological properties when compared to MSH-GO. The findings reveal that the oil sample containing 0.5 wt% MSH-C can effectively reduce wear volume (by approximately 26.4%) as compared to fully formulated oil and that the friction coefficient is decreased to ∼0.02. SEM, Raman, FIB-TEM, and TOF-SIMS characterizations and molecular dynamics simulation were used to investigate the tribological mechanism. A tribo-film composed of two layers of different compositions was formed on the worn surface of MSH-C, indicating the synergistic effect of MSH and graphite.

Nano-Diamond Decorated Reduced Graphene Oxide: Improvement to Tribological Property of Polyimide and Its Molecular Dynamic Simulation

In this paper, the nano-diamond decorated reduced graphene oxide (Diamond-RGO) and its polyimide (PI) composite, by using in situ polymerization method, are synthesized, respectively. The tribological study of Diamond-RGO/PI composite exhibits super anti-wear properties under dry sliding and high load condition: the lowest wear rate of 4.9 × 10−8mm3N−1m−1, which is extraordinarily lower than that of pure PI and RGO/PI composite, is obtained under load 100 N. The tribological mechanism investigation shows that Diamond-RGO composite has a strong synergistic effect in the tribological process which contributes to form a uniform transfer film on the counterpart ring and thus significantly decrease the composite’s wear rate. Through molecular simulation, the shear behavior of the composite material indicates that the presence of the Diamond-RGO composite will obviously weaken the influence of the iron wall on the PI bulk phase molecular chain in the shear process. This confirms that the synergistic effect between nano-Diamond and RGO will improve its PI composite’s tribological performance on atomic level.

Current-carrying tribological properties and wear mechanisms of Mo-containing Cu alloy coatings produced by laser cladding

Copper alloy-molybdenum coatings were prepared on the surface of Cu-Cr-Zr alloys by laser cladding. The phase and microstructure were observed, and the hardness, conductivity, friction and wear properties under current-carrying conditions were tested. The results indicate that the prepared coatings exhibit good metallurgical bonding with the substrate. The Brinell hardness of the coatings ranges from 60 to 105 HB, and the electrical conductivity ranges from 17 % to 27 % IACS. The primary wear mechanism is abrasive wear and adhesive wear without current, resulting in the detachment of the Mo phase and transfer of the Cu phase during the sliding process. And it shifts to severe adhesive wear under current-carrying conditions, leading to the formation of aluminum deposit on the coatings.

Wear-resistant phenolic composites reinforced with attapulgite and short carbon fibers for applications subjected to both dry and oil-lubricated sliding

Attapulgite (AT) nanofibers were integrated into phenol-formaldehyde resin (PF) and PF composites reinforced with short carbon fibers (CF). Inclusion of AT significantly enhances the wear resistance of PF under both dry and oil-lubrication conditions. The hybrid nanocomposites, reinforced with both AT and CF, exhibit a high mechanical strength. Interestingly, AT and CF lower synergistically the friction coefficient of PF subjected to harsh dry sliding conditions. The hybrid nanocomposites exhibit excellent tribological performance under both dry and oil-lubrication conditions. Tribofilms’ nanostructures were comprehensively analyzed for disclosing dominant tribological mechanisms. Outcome of this work provides new ideas for developing tribo-materials of a high adaptability to various dry/oil-lubrication conditions.

Tribological mechanism based on tribo-chemistry and molecular dynamics of polyurea/polyimide shape memory copolymers at high temperature

Exploring the tribological mechanism of the shape memory polymers plays an important role in designing intelligent lubricating materials. Here, a series of shape memory polyurea (PUA)/polyimide (PI) were prepared and their tribological performance were investigated. The result showed that the friction and wear of PUA/PI were higher at shape memory transition temperature (Ttrans) than at 200 ℃ and room temperature (RT). However, introducing PUA units into PI enhanced its shape memory stability and tribological performance. SEM and XPS analysis revealed that introducing PUA promoted the formation of polymer-based tribofilm. Molecular dynamics simulations further illustrated that the high relative atomic concentration of PUA/6PI at the sliding interface improves the bonding between the tribofilm and the counterpart, thereby improving overall tribological performance.

Synthesis and characterization of porous silica and composite films for enhanced CO₂ adsorption: A circular economy approach

This study explores the synthesis and application of carbon-negative technology that leverage circular economy and environmentally friendly methodologies. Porous silica using plant-derived silica sources and self-assembled lignin templates were prepared, achieving an impresive surface area of up to 104.76 m2/g. Additionally, we prepared porous composite films via a freeze-drying process incorporating polyvinyl alcohol (PVA). These films demonstrated enhanced tensile properties, with a tensile strength reaching 285.72 kPa. Notably, the film surfaces engaged in a third-body tribology mechanism, which endowed them with excellent abrasion resistance and a low friction coefficient. The specific surface area of the films was measured at 20.15 m2/g, making them ideal substrates for CO₂ adsorption functionalization. The functionalized films showcased outstanding CO₂ adsorption capabilities, with a maximum uptake of 29.38 mg/g. Furthermore, they retained over 90% of their adsorption capacity after five adsorption/desorption cycles. Under high CO₂ conditions, these composite films combine the desirable attributes of both solid and liquid adsorbents—high surface area, low volatility, and adsorption stability—contributing significantly to greenhouse gas mitigation and the pursuit of carbon neutrality.

Microstructures, high-temperature tribological and electrochemical mechanisms of FeCoNiCrAl high-entropy alloy coating prepared by laser cladding on a copper alloy: Combined TEM and DFT calculation

Two layers of FeCoNiCrAl coatings were prepared on copper (Cu) alloys substrates in this paper in order to improve the wear and corrosion performance of Cu alloys and to reduce the dilution of Cu in the laser cladding (LC) process. The microstructures, phase composition, microhardness, and crystal structure of the resulting coatings were analyzed, and their high-temperature tribological and electrochemical properties were tested. The results show that the surface of the HEA coatings still consists of a single-phase body-centered cubic (BCC) with low Cu content, and no generation of a second phase was observed. Compared with the substrate, the FeCoNiCrAl HEA coatings have better wear resistance, with oxidative wear and slight adhesive wear as the wear mechanism at 250 ℃. In addition, the FeCoNiCrAl HEA coating showed better electrochemical corrosion performance in 3.5 wt% NaCl solution. The corrosion mechanism is that the dense oxide layers inhibit the erosion of Cl- and high reaction barriers slow down electrochemical reactions.

Tribological performance and mechanism of graphite, hBN and MoS2 as nano-additives in palm kernel oil-based lubricants: A comparative study

Layered nanoparticles have received considerable interest in tribological applications owing to their outstanding tribological performances, including in vegetable oil-based lubricants. Despite the advantages of vegetable oil-based lubricants over petroleum-based lubricants, the limited manufacturing scale of vegetable oil-based lubricants restricts their more comprehensive implementation in various industries. In order to gain further insights into the exquisite nano-additive properties of layered nanoparticles, this research was conducted to explore the tribological performance of palm kernel oil-based lubricants combined with three different layered nanoparticles, namely graphite, hexagonal boron nitride (hBN), and molybdenum disulfide (MoS2), using a four-ball tribotester. The four-ball tribotester analysis indicated that the wear scars lubricated with graphite, hBN, and MoS2 nanolubricants exhibited a lower coefficient of friction (COF) and wear scar diameter (WSD) than the base lubricant. The findings also showed that the MoS2 nanolubricant had the best friction reduction and anti-wear performance, with a 24.9% drop in COF and a 12.3% drop in WSD. It was followed by the hBN and graphite nanolubricants. To fully understand the lubricating mechanisms involved, the worn surfaces of the tested balls were characterised using various microscopic and spectroscopic methods. Accordingly, the structural changes that occurred during sliding were shown to affect the formation of protective tribofilm. In summary, the findings in this study suggest that the formulated layered nanolubricants possessed exceptional tribological performance, which was contributed by the inherent properties of the individual nanoparticles and the formation of effective tribofilms.