Excellent Tribological Performance Research Articles

Extremely enhanced friction and wear performance of hydrogen-free DLC film at elevated temperatures via Si doping

Hydrogen-free diamond-like carbon (DLC) films have garnered significant attention as a highly efficient solid lubrication material, but poor high-temperature lubrication and wear resistance limit their further application. Here, silicon-doped DLC (Si-DLC) films with different Si contents were deposited using a superimposed HiPIMS-DCMS deposition system to improve their high-temperature lubrication and wear resistance performance. The influence of Si content on the microstructure, mechanical and high-temperature friction and wear behavior of Si-DLC films was investigated. The results showed that Si-DLC films had a dense structure and nanoscale smooth surface. The Si doping enhanced the adhesion strength and relieved the residual stress of Si-DLC films, but decreased the hardness and Young's modulus. Meanwhile, Raman and XPS spectroscopy revealed significant local structural changes in Si-doped DLC films. Furthermore, the results showed that DLC films doped with low Si content displayed excellent tribological performance at elevated temperatures due to the graphite lubricating layer on the surface of wear marks. Specifically, Si-DLC film with 3.31 at% Si had an ultra-low average friction coefficient of 0.04 at 450 °C and still provided effective lubrication at temperatures up to 500 °C. In contrast, pure DLC film failed to lubricate at 450 °C due to the severe graphitization transition and Si-DLC film with 17.47 at% Si quickly failed to lubricate at 200 °C due to the SiC and SiO2. This work sheds light for the high-temperature application of DLC films doped with low Si content by superimposed HiPIMS-DCMS deposition system.

Synergistic effect of NiCr-Cr3C2 + Y2O3 to enhanced performance of Ti-based composite fabricated by laser cladding

The surface modification technology, which is of great significance in aerospace, energy, and other fields, is based on reinforcement. In this study, a titanium-based composite material system, formed using laser cladding and based on NiCr-Cr3C2 + Y2O3 dual additives, was investigated. TiC reinforcement particles were generated in situ through the reaction between NiCr-Cr3C2 and Ti6Al4V during the cladding process. Additionally, Ni and Cr elements provided solid solution-strengthening effects to the matrix. Meanwhile, Y2O3 particles were introduced ex-situ, effectively eliminating defects in the coating and inhibiting the dendritic growth of TiC particles. This process enhanced the dispersion-strengthening effect of TiC. The titanium-based composite material, incorporating NiCr-Cr3C2 + Y2O3, exhibited excellent tribological performance, displaying a wear rate of approximately 4.22 × 10−4 mm3·N−1·m−1.

The synthesis and tribological behaviour of a phosphorus-free triazine organic molybdenum as friction modifier

A phosphorus-free triazine-based organic molybdenum compound (DCDM) was designed and synthesized by using the click chemistry approach, and its friction-reducing and anti-wear properties were evaluated in PAO10 base oil. The results indicated that DCDM exhibited excellent tribological performance, with a reduction of approximately 35% in friction coefficient and about 46% in wear scar diameter, due to the synergy effect between Mo and S. Surface analysis by EDS and XPS revealed the formation of MoO3, Fe2(SO4)3, FeS, and MoS2 in the friction film. And it was furhter confirmed that the presence of MoS2 in the friction film contributed most significantly to the enhancement of the friction-reducing and anti-wear properties of the developed triazine-based organic molybdenum compound in PAO10 base oil.

A dual-phase Fe-Co-Ni-Cr-Mn high entropy alloy thin film with superior strength and corrosion-resistance

Improving the mechanical properties of high-entropy alloys (HEAs) with a face-centered cubic (fcc) structure is critical for their potential applications. In this work, a Fe-Co-Ni-Cr-Mn thin film was prepared and deposited with a power of 360W. This alloy thin film exhibits a dual-phase microstructure consisting of a fcc matrix and sigma phase (σ phase) precipitates. The 360 W-film shows ultra-high strength-ductility synergy, with a hardness of 10.4GPa, yield strength of 6.2GPa, and a fracture strain of ~25% (micro-pillar compression tests). The excellent mechanical properties can be mainly attributed to the grain size effect, the hardening effect of the σ precipitates, and deformation twinning. Moreover, this alloy thin film exhibits excellent tribological performances and corrosion resistance. Our results demonstrate high potential of the dual-phase HEA thin film for industrial applications as high-performance protective coating materials.

Extremely enhanced friction and wear performance of hydrogen-free DLC film at elevated temperatures via Si doping

Hydrogen-free diamond-like carbon (DLC) films have garnered significant attention as a highly efficient solid lubrication material, but poor high-temperature lubrication and wear resistance limit their further application. Here, silicon-doped DLC (Si-DLC) films with different Si contents were deposited using a superimposed HiPIMS-DCMS deposition system to improve their high-temperature lubrication and wear resistance performance. The influence of Si content on the microstructure, mechanical and high-temperature friction and wear behavior of Si-DLC films was investigated. The results showed that Si-DLC films had a dense structure and nanoscale smooth surface. The Si doping enhanced the adhesion strength and relieved the residual stress of Si-DLC films, but decreased the hardness and Young's modulus. Meanwhile, Raman and XPS spectroscopy revealed significant local structural changes in Si-doped DLC films. Furthermore, the results showed that DLC films doped with low Si content displayed excellent tribological performance at elevated temperatures due to the graphite lubricating layer on the surface of wear marks. Specifically, Si-DLC film with 3.31 at. % Si had an ultra-low average friction coefficient of 0.04 at 450 °C and still provided effective lubrication at temperatures up to 500 °C. In contrast, pure DLC film failed to lubricate at 450 °C due to the severe graphitization transition and Si-DLC film with 17.47 at. % Si quickly failed to lubricate at 200 °C due to the SiC and SiO2. This work sheds light for the high-temperature application of DLC films doped with low Si content by superimposed HiPIMS-DCMS deposition system.

Fabrication of a novel hydrophobic zinc borate/polydopamine/talc nanocomposite with sandwich-like structure for enhanced tribological properties

Two-dimensional layered materials (2DLMs) as lubricant additives have received increasing attention due to their low interlaminar shear stress, outstanding chemical stability and lubrication effects, but the extreme pressure properties, dispersion and dispersion stability in base oils are poor. Herein, a hydrophobic zinc borate/polydopamine/talc (OA-ZB/PDA/TA) nanocomposite with sandwich-like structure is prepared by hydrothermal-assisted intercalation combined with mechanical activation process using natural talc 2DLMs as substrate and oleic acid (OA) as a surface hydrophobic modifier and peeling aid. No obvious sedimentation of OA-ZB/PDA/TA occurs in the rapeseed oil after 15 d, while pure TA is significantly deposited after 12 h, showing superior dispersion and dispersion stability. The OA-ZB/PDA/TA used as a lubricant additive in rapeseed oil exhibits excellent tribological performances under the loads from 147 to 784 N, particularly, wear scar diameter and coefficient of friction reduce by 51.4 and 33.7 % under 392 N, respectively, and the maximum nonseizure load (PB) increases by 27.0 % relative to pure TA. The TA-ZB-TA "sandwich-like" structure gives full play to the synergistic lubrication between ZB NPs and TA, resulting in the sliding and rolling effects under low load, friction film and rolling effect under medium load, and friction film under high load. Our work provides a new avenue for the enhanced extreme pressure properties and dispersion stability of 2DLMs in base oil.

Temperature-induced wear micro-mechanism transition in additively deposited nickel alloys with different solid lubricants

Additive manufacturing of self-lubricating alloys plays a crucial role in the production of complex wear-resistant components and in expanding repair capabilities, especially for intricate wear parts with low tolerances (e.g. with cooling channels). Herein, we report a novel approach providing nickel-based alloy with an excellent tribological performance in dry sliding contacts. Laser-deposited self-lubricating nickel alloys, infused with anti-wear additives of molybdenum disulfide, nickel sulfide, copper sulfide, or bismuth sulfide, were subjected to dry sliding wear tests against an alumina ball counterbody at a temperature range of up to 800 °C. The self-lubricating alloys exhibited a significant decline in friction (43 %) and wear (45 %) at room temperature, 400 °C (friction 40 %, wear rate 55 %), and 600 °C (MoS2-based, friction 58 %, wear rate 75 %). The MoS2-based alloy coating demonstrated excellent performance characteristics up to 800 °C (friction coefficient ⁓0.25, wear rate 11 × 10−6 mm3 N−1 m−1) due to the formation of a ‘glazed’ tribolayer. Wear mapping allowed to identification of a critical condition for self-lubricating alloys where positive transitions in wear mechanisms led to a synergistic lubrication mode involving the formation of tribologically induced new lubricious phases such as silver molybdate or nickel-bismuth intermetallic. This work provides a comparative evaluation of the micromechanisms, surface transitions, and tribochemistry of solid lubricants at a wide temperature range and a variety of applications.

Design of 3D printed metal frame nested porous polyimide composites

Porous polyimide (PPI) can store oil, but the mechanical properties are also weakened by the pores. To solve this problem, a 3D printed metal frame-PPI nested composite (MFP) was proposed. The composite material has a binary pore structure (ordered submillimeter-level metal frame macropores and disordered micron-level PPI micropores). PPI material is filled in the metal frame, and the oil could be filled into the micropores, improving the mechanical and tribological performances. The preparation method was optimized and the mechanical, oil content, tribological properties of MFP were investigated. The experimental results showed that MFP enhance its ability to resist external deformation and has excellent mechanical properties and tribological properties. As the density of PPI filled in the metal frame increases, PPI is tightly bonded to the metal. Under the PPI filling density of 1.1 g cm−3 and sintering temperature of 330 °C, MFP could be well formed, and the friction coefficient is the lowest (0.035). MFP exhibits excellent mechanical and tribological performances.

Boosting the triboelectric performances of biowaste chitosan keratin triboelectric nanogenerator using carbon composite film as charge storage and charge recombination blocking intermediate layer

Environmental conservation efforts are promoting energy-generation technologies that avoid the use of highly polluting fuels and promote the reuse of waste materials. Advances in triboelectric nanogenerators (TENGs) have led to the progress in harvesting energy from ambient mechanical sources and powering small devices and sensors while being compact, flexible, biocompatible, and eco-friendly. Nevertheless, the practical applications of TENG have limitations. Therefore, the development of TENG with excellent triboelectric performance, eco-friendliness, and low cost is crucial. Consequently, an environmentally friendly, inexpensive TENG device with outstanding triboelectric performance was designed using keratin-enhanced chitosan as a tribo-positive material, a carbon film as an intermediate layer, and polytetrafluoroethylene as a triboelectric negative material. The device was purposely designed to simultaneously play a role in waste treatment and efficient green energy harvesting. Therefore, keratin was extracted from recycled fur, and a carbon film was selected to enhance the triboelectric performance because of its excellent electrical conductivity and dielectric constant. The triboelectric properties of a chitosan keratin intermediate layer (CKI)-TENG were systematically investigated. Practical applications of the CKI-TENG in charging electronic devices and waste-noise harvesting were also studied. The developed CKI TENG exhibited outstanding triboelectric performance compared to a TENG device without an intermediate layer. Particularly, the charge transfer, output voltage, and power density was improved by 19%, 46%, and 60%, respectively, compared to the output of the chitosan-keratin (CK) TENG device. It also exhibited outstanding cyclic and charging-discharging stabilities. In addition, the power density of the developed CKI TENG was higher than that of previously reported TENG devices. Thus, it can play a significant role in green and clean energy generation and the utilization of the harvested energy in practical applications, such as biomedical sensors, charging electronic devices, smart textiles, and sensors.

Preparation and Tribological Performance of Multi-Layer van der Waals Heterostructure WS2/h-BN

Van der Waals heterostructures with incommensurate contact interfaces show excellent tribological performance, which provides solutions for the development of new solid lubricants. In this paper, a facile electrostatic layer-by-layer self-assembly (LBL) technique was proposed to prepare multi-layer van der Waals heterostructures tungsten disulfide/hexagonal boron nitride (vdWH WS2/h-BN). The h-BN and WS2 were modified with poly (diallyldimethylammonium chloride) (PDDA) and sodium dodecyl benzene sulfonate (SDBS) to obtain the positively charged PDDA@h-BN and the negatively charged SDBS@WS2, respectively. When the mass ratio of PDDA to h-BN and SDBS to WS2 were both 1:1 and the pH was 3, the zeta potential of PDDA@h-BN and SDBS@WS2 were 60.0 mV and −50.1 mV, respectively. Under the electrostatic interaction, the PDDA@h-BN and SDBS@WS2 attracted each other and stacked alternately along the (002) crystal plane forming the multi-layer (four-layer) vdWH WS2/h-BN. The addition of the multi-layer vdWH WS2/h-BN (1.0 wt%) to the base oil resulted in a significant reduction of 33.8% in the friction coefficient (0.104) and 16.8% in the wear rate (4.43 × 10−5 mm3/(N·m)). The excellent tribological property of the multi-layer vdWH WS2/h-BN arose from the lattice mismatch (26.0%), a 15-fold higher interlayer slip possibility, and the formation of transfer film at the contact interface. This study provided an easily accessible method for the multi-layer vdWH with excellent tribological properties.

Topology optimization of AISI 4140 steel with surface texture filled by multi-solid lubricants for enhancing tribological properties

Wind power gears will be excessively worn due to lubrication failure during operation. Herein, the tribological properties of rubbing pairs are improved by filling solid lubricants into surface texture. In texture design, three types of topological textures (Circle (C), Hexagon (H) and Circle/Hexagon (CH)) were obtained by cell topology optimization, and then three cases with 20%, 30%, and 40% density were designed for each texture. Next, SnAgCu and TiC were deposited in texture of AISI 4140 steel (AS) to obtain 9 kinds of self-lubricating surfaces. Among them, AS with 30% CH density (AS-CH30) exhibits excellent mechanical and tribological properties. Compared with AS-C and AS-H, the maximum equivalent stress of AS-CH was decreased by 10.86% and 5.37%, respectively. Friction coefficient and wear rate of AS-CH30 were 79.68% and 78% lower than those of AS. The excellent tribological performances of AS-CH30 can be attributed to the synergistic effect of topological surface and solid lubricants. Topological surface can not only reduce fluctuation of equivalent stress, but also promote the stored lubricants to be easily transferred at the contact interface to form a 200 nm lubricating film containing solid lubricants (mainly), oxides and wear debris.

Study on the tribological properties of hexagonal boron nitride flakes composite hydrophilic/hydrophobic ionic liquids films by self-assembly

Due to the weak out-of-plane van der Waals interaction between layers, hexagonal boron nitride (h-BN) with a stacking structure has been proven to be a promising lubrication material for its friction performance. However, obtaining h-BN composite films with excellent substrate bonding and low friction properties under high humidity remains challenging. Ionic liquids (ILs) composed of anions and cations that are liquid at or near room temperature have distinguished themselves in the field of lubrication (lubricating additives and lubricating films) due to their advantages of low saturated vapor pressure, good stability and high viscosity. Based on the relationship between lubrication performance and hygroscopicity of hydrophilic/hydrophobic ILs, a simple and flexible method for preparing h-BN composite hydrophilic/hydrophobic ILs films on metal substrates has been developed. h-BN has excellent antioxidant and moisture resistance as well as lubrication performance. Consequently, the influence of the hygroscopicity of ILs on the macroscopic tribological performance of h-BN composite hydrophilic/hydrophobic ILs films was investigated. The results showed that PVA/BNOH composite hydrophobic ILs films displayed a lower friction coefficient and outstanding wear resistance than those of PVA/BNOH composite hydrophilic ILs films in both atmosphere and high humidity. The synergies between the film layers, the intrinsic differences between the hydrophilic and hydrophobic ILs, and tribo-chemical reactions at friction interfaces greatly promoted the realization of excellent tribological performance of composite films. Additionally, the tribological properties of these films at high humidity were mainly related to the interaction between water molecules and the ILs.

Effect of Ag addition on high-temperature self-lubricating behavior of CuNi-based composites

CuNi-based high-temperature self-lubricating composites with BaF2/CaF2 eutectic as a main lubricant were prepared by rapid hot-pressing. The results showed that the addition of BaF2/CaF2 can introduce heterogeneous structures, in which the hard phase of BaF2/CaF2 closely surrounded the soft copper alloy phase. The high strength of the composite was mainly derived from the dislocation strengthening caused by the heterogeneous deformation induced stress, and solid solution strengthening induced by Ag. At 500 ℃, the excellent tribological performance was mainly attributed to the combined lubricating effects of Ag, BaF2/CaF2 and metal oxides. Furthermore, the addition of Ag formed concrete and continuous lubricating film on the worn surface, with more fluorides to continuously and stably protect the composite substrate.

Robust wear performance of graphene-reinforced high entropy alloy composites

The expected excellent tribological performance of high-entropy alloys (HEAs) is rarely achieved due to the absence of self-lubricating ability on the worn surface. In particular, the situation is more challenging in HEAs with face-centered cubic structure because of the inferior yield strength when used in dry sliding conditions. Unlike conventional soft-solid lubricants, which deteriorate the mechanical properties of HEA matrix, in this study we demonstrate in a protocol model alloy that the proper incorporation of few-layer graphene as reinforcement in CoCrFeNiMn can lead to both surface strengthening and lubrication. This is achieved by a partially chemical interface reaction between graphene and HEA via a tunable fabrication process, resulting in a reduction of wear rate and friction coefficient of 86.03% and 23.87%, respectively. As a result of the interfacial in-situ carbide strengthening together with the self-lubrication of graphene, this tailored composite structure also exhibits superior tribological properties over most HEA-based self-lubrication composites. Besides, the subsurface structure evolution and deformation mechanisms that influence the wear resistance are systematically clarified through microscopic exploration and atomistic simulation. The present study presents an effective strategy for the development of innovative HEA composites suitable for safety-critical applications, which overcomes the inherent compromise and achieves exceptional tribological performance, i.e., self-lubricating and anti-wear.

Refractory ceramic WC reinforced Co matrix composite coatings on IN718 superalloy: Microstructure, wear mechanisms and surface energy

WC micro-particles reinforced Co matrix composite coatings were fabricated by laser cladding in this work. Their microstructure, wear mechanisms and surface energy were investigated. The results show that the improved hardness (501.78–586.7 HV0.5) was mainly attributed to the formation of carbides and intermetallic compounds. Compared to the substrate, an order of magnitude improvement (1.44, 1.16 and 0.65 × 10−5 mm3/N·m) in wear resistance was obtained in the composite coatings at RT, the COF decreased by 33.5%. The wear mechanism of the composite coatings at 600 ℃ changes from abrasive and adhesive wear to oxidation wear, COF and wear rate were reduced by 32.4% and 57.3%, respectively. The surface energy (29.40 mN/m) of the Co-5 wt%WC coating is the lowest, which is one of the reasons for its excellent tribological performance.

A study of the tribological properties of Mo-S-Ti composite films prepared by magnetron sputtering

Pure MoS2 films exhibit disadvantages such as low densities, poor mechanical properties, and weak wear resistance under atmospheric environments. For this reason, Ti was chosen as the doping element in this work. Mo-S-Ti composite films with different Ti contents were deposited using the magnetron sputtering system, and the effects of Ti content on the chemical composition, mechanical and tribological properties of these films were analyzed by numerous characterization methods to determine the doping content of Ti elements. The results show that the tribological performance of Mo-S-Ti composite film under atmospheric environments reaches the best when the Ti content is 13.48 at%. In addition, the present work also found that longitudinal load and reciprocating frequency have a significant effect on the tribological properties of this film. It is easier to form high quality transfer film on GCr15 balls under higher longitudinal load and lower reciprocating frequency, thus transforming the friction between film and GCr15 ball into the friction between film and transfer film, resulting in excellent tribological performance.

Investigating tribological properties of electrophoretically deposited graphene nanoplatelets coatings on mild steel

The use of graphene-based materials to enhance the tribological properties of metal surfaces has garnered increasing interest in recent years. In fact, various studies have demonstrated that graphene-related materials, such as graphene nanoplatelets (GNPs), hold promise as solid lubricants. Electrophoretical deposition (EPD) is an interesting coating method to obtain a deposition of particles such as graphene as it is a simple, cheap and effective process with a low environmental impact. This study focusses on investigating the tribological properties of GNPs coatings obtained through anodic EPD on mild steel. Specifically, a combination of GNPs and deionized water as the deposition medium is introduced, allowing a cost-effective process with reduced environmental impact.Deposition time (5, 10 and 20 min) and concentration in the bath (0.5, 1 and 1.5 g/l) were varied in a full factorial plan to highlight their effects on coating performance. The coatings achieved demonstrated good adhesion with scratch break loads above 10 N and excellent tribological performances, with a friction coefficient of above 0.1. The results showed how concentration and process duration have two opposing effects on the adhesion and tribological characteristics of the coatings. The presence of an intermediate optimal condition, with 10 min deposition and a GNP concentration of 1 g/l, leading to an improvement in anti-wear properties of approximately 85 % and a coating break distance of over 80 m. An ANOVA analysis was developed to confirm the statistical significance of the process parameters in adhesion and tribology of the coatings.

Synthesis of core-shell PFPE@SiO2 nanocapsules and their self-lubrication effect in phenol-formaldehyde resin

To improve the mechanical properties and tribological properties of desirable polymer composites, a novel nano-encapsulated perfluoroyeyeane @ silica (PFPE@SiO2) nanocapsules were used to modify the phenol-formaldehyde (PF) resin composites (PFPE@SiO2-PF). These nanocapsules were successfully obtained by interfacial polymerization, exhibited a consistent size ranging from 130 nm to 180 nm, along with a thin shell thickness of 19.4 nm and a high oil-contenting rate of 49.13 wt%. The prepared PFPE@SiO2-PF composites simultaneously demonstrated excellent mechanical properties and tribological performances. Specifically, the compressive strength of the 5 wt%-PF was increased by 33.3% than that of pure PF resin. Moreover, the friction coefficient (COF) of the 25 wt%-PF (50 N) could be reduced by 86.3% (from 0.564 to 0.077) and the wear rate could be reduced by 98.0% (from 69.8 × 10−6 mm3 N−1 m−1 to 1.4 × 10−6 mm3 N−1 m−1). The PFPE oil released from the nanocapsules during the friction process produced a transfer film which brought an extremely low COF and wear rate. These results confirmed the excellent self-lubricating property of the PFPE@SiO2-PF composites and presented a potential application in fabricating self-lubricating polymer composites field.

Oil-soluble polymer brushes-functionalized nanoMOFs for highly efficient friction and wear reduction

Nanomaterials as lubricating oil additives have attracted significant attention because of their designable composition and structure, suitable mechanical property, and tunable surface functionalities. However, the poor compatibility between nanomaterials and base oil limits their further applications. In this work, we demonstrated oil-soluble poly (lauryl methacrylate) (PLMA) brushes-grafted metal-organic frameworks nanoparticles (nanoMOFs) as lubricating oil additives that can achieve efficient friction reduction and anti-wear performance. Macroinitiators were synthesized by free-radical polymerization, which was coordinatively grafted onto the surface of the UiO-67 nanoparticles. Then, PLMA brushes were grown on the macroinitiator-modified UiO-67 by surface-initiated atom transfer radical polymerization, which greatly improved the lipophilic property of the UiO-67 nanoparticles and significantly enhanced the colloidal stability and long-term dispersity in both non-polar solvent and base oil. By adding UiO-67@PLMA nanoparticles into the 500 SN base oil, coefficient of friction and wear volume reductions of 45.3% and 75.5% were achieved due to their excellent mechanical properties and oil dispersibility. Moreover, the load-carrying capacity of 500 SN was greatly increased from 100 to 500 N by the UiO-67@PLMA additives, and their excellent tribological performance was demonstrated even at a high friction frequency of 65 Hz and high temperature of 120 °C. Our work highlights oil-soluble polymer brushes-functionalized nanoMOFs for highly efficient lubricating additives.

Tribological Behavior and Mechanism of Surface-Modified Mullite as Polyurea Grease Additive

Abstract The excellent tribological performance of nanoparticles as additives in lubricating greases has attracted widespread attention. In this study, a silane coupling agent (KH550) was used to chemically modify nanoscale mullite (composed of Al2O3 and SiO2), and the modified nano-KH-mullite was dispersed as an additive in polyurea grease at different ratios (0.01, 0.05, 0.07, 0.1, and 0.3 wt%). The friction and wear performance of the compound polyurea greases were evaluated using a four-ball friction tester. Professional instruments will be utilized to analyze the micro-morphology, 3D profile, elemental content, and valence state of the worn surface, aiming to investigate the lubrication and antiwear mechanism of the nano-KH-mullite additive. The results indicate that nano-mullite effectively improves the antiwear and antifriction performance of the polyurea grease. When the additional content is 0.05 wt%, the friction coefficient (COF) and the wear scar diameter (WSD) are reduced by approximately 19.97% and 11.1%, respectively, and the roughness of the worn surface is also reduced. The excellent tribological performance of the composite grease is attributed not only to the good dispersibility of KH-mullite but also to its ability to promote the formation of a composite lubrication film on the friction pair surface. The component KH-Al2O3 in the KH-mullite can fill and repair scratches and grooves on the worn surface, while the other component KH-SiO2 can bear the load and convert the friction mode to rolling friction.