Next Article in Journal
Liquid Crystal/Carbon Nanotube/Polyaniline Composites and Their Coating Orientation Patterning Applications
Previous Article in Journal
Extended Lifetime of Dual-Layer Yttria-Stabilized Zirconia APS/Gadolinium Zirconate SPS Thermal Barrier Coatings in Furnace Cycle Tests
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Coatings
Volume 14
Issue 12
10.3390/coatings14121567
coatings-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

MXene Coatings Based on Electrophoretic Deposition for the High-Temperature Friction Reduction of Graphite for Mechanical Seal Pairs

by
Qunfeng Zeng
1,*,
Shichuan Sun
1,
Siyang Gao
2,3,
Jianhang Chen
4 and
Fan Zhang
5
1
Key Laboratory of Education Ministry for Modern Design and Rotor-Bearing System, Xi’an Jiaotong University, Xi’an 710049, China
2
Shi-Changxu Innovation Center for Advanced Materials, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
3
Liaoning Key Laboratory of Aero-Engine Materials Tribology, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
4
AECC Hunan Aviation Power Plant Research Institute, Zhuzhou 412002, China
5
Engineering Research Center of Heavy Machinery of Ministry of Education, Taiyuan University of Science and Technology, Taiyuan 030024, China
*
Author to whom correspondence should be addressed.
Coatings 2024, 14(12), 1567; https://doi.org/10.3390/coatings14121567
Submission received: 19 November 2024 / Revised: 9 December 2024 / Accepted: 11 December 2024 / Published: 13 December 2024
(This article belongs to the Special Issue Engineered Coatings for a Sustainable Future)
Browse Figures
Versions Notes

Abstract

:
This paper presents the tribological properties of MXene (Ti3C2Tx) coatings on the surface of impregnated zinc phosphate graphite. MXene coatings were deposited on the surface of the impregnated zinc phosphate graphite by the electrophoretic deposition method at different voltages of 5 V, 10 V, and 15 V. The tribological properties of the MXene coatings were investigated from room temperature to 400 °C in ambient air. The results show that MXene coatings are helpful to improve the tribological properties of the impregnated zinc phosphate graphite at elevated temperatures. The coatings deposited at 5 V have the best anti-friction behaviors among the coatings at the different deposition voltages, which indicates that the MXene coatings deposited at 5 V are suitable for applications in a wide range of temperatures, especially high-temperature environments. The average CoF of the coatings deposited at 5 V is about 0.18 at 200 °C, 0.25 at 300 °C, and 0.21 at 400 °C, respectively. The CoF of the coatings deposited at 15 V is relatively stable with the increase in temperature. Moreover, the high-temperature low-friction mechanism was discussed. The high-temperature low-friction mechanism is attributed to the good self-lubricating behaviors of the impregnated zinc phosphate graphite and the transfer film of the MXene coatings.

1. Introduction

Seals are used in many machine parts of the aircraft engine to solve the leakage problem between the rotating parts and non-rotating parts [1,2,3,4]. Graphite has a series of advantages such as self-lubrication, high thermal conductivity, chemical stability, etc., and the sealing performance of graphite can still be ensured under the harsh conditions of aircraft engines (high temperature, high pressure, high speed) [5,6,7,8,9,10]. The graphite seal has a wide range of applications in aviation engine oil circuit seals. With the continuous development of technology, the performance of aero engines continues to be improved, which makes the service conditions of the key components significant. Therefore, it is of great significance to study the mechanism of the high-temperature friction and wear of graphite sealing materials and enhance the high-temperature tribological properties. Therefore, it is necessary to carry out research on the preparation technology of graphite sealing materials and explore their anti-friction and wear-resistant mechanisms under extreme working conditions such as high temperature, which would be of great significance for the research and development of high-performance sealing graphite [11,12,13,14].
The sealing materials may have high strength, high thermal conductivity, high corrosion resistance, high chemical stability, and high heat resistance. Good sealing graphite for aviation may meet the requirements of stable friction performance under different working conditions such as high speed and high temperature. Impregnated metal graphite means that under the conditions of high temperature and high pressure, the molten metal is filled into the connected pores of the graphite blank to form a network structure and improve the overall strength, hardness, and density of the graphite. Zhao et al. [15] studied the tribological performance of metal-impregnated graphite, resin-impregnated graphite, and non-metal-impregnated graphite under high temperature and high load. The metal-impregnated graphite has a stable friction regime and exhibits good anti-friction and anti-wear properties under extreme pressure (200–350 MPa) and high temperature (100–350 °C). The impregnated materials can enhance the strength of the graphite matrix and improve the formation of the graphite tribofilm on the counterpart surfaces. The friction-induced structural ordering of graphite and the oxidation of metal in the formed mechanically mixed layer are beneficial for friction and wear reduction. Mahto et al. [16] studied the tribological performance of carbo-graphite (CG) and copper-impregnated carbo-graphite (Cu-CG) at different temperatures (RT to 350 °C) under dry and oil-lubricated (room temperature (RT) and 120 °C) conditions. The results indicate that Cu-CG shows a low wear rate compared to CG due to its higher hardness caused by the impregnation of copper.
Two-dimensional material is a sheet-like material composed of a single layer or a few layers of atoms, with a thickness of nanometers. The atoms in the layers are connected in the form of ionic or covalent bonds and the layers are connected by weak van der Waals forces in 2D materials, thus showing unique physical and chemical properties. The transition metal sulfides (TMDs), black scale (BP) and hexagonal boron nitride (h-BN), and other graphene-like materials have been studied [17,18,19,20,21,22,23,24,25,26]. In 2011, a new two-dimensional material, Ti3C2TX (Tx stands for the end groups, such as -OH, -F, etc.), was discovered and named MXene [27,28,29,30,31,32]. With the research development of Ti3C2TX, the MXene species have increased rapidly and have grown to include two-dimensional transition metal carbon/nitride. Ti3C2TX is one of the earliest members of the MXene family. Marian et al. [33] studied the friction and wear behaviors of Ti3C2TX coatings with relative humidity and contact pressure in steel/steel contact. Ti3C2TX as a solid lubricant can improve the tribological properties. The CoF (coefficient of friction) and the wear volume are reduced significantly due to the formation of the Ti3C2Tx friction film. Yin et al. [34] prepared Ti3C2TX/nano-diamond coatings and PTFE balls used for the friction pair. It was found that under dry conditions, the CoF is reduced to half of the CoF of the Ti3C2Tx coatings. This shows the synergistic effect between the protective effect of PTFE and the self-lubrication effect, including the rolling of nano-diamonds and the sliding and embedding of two-dimensional Ti3C2TX, forming three layers of the friction film and achieving ultra-wear resistance. Lian et al. [35] prepared Ti3C2TX coatings with 200 nm in thickness on a copper disk by the spraying method, and observed that the CoF and the wear were reduced. The Ti3C2 coatings prevent direct contact between the two metal sliding surfaces during the sliding, and a carbon-rich lubricating transfer film was formed between the contact interfaces, which was produced by the tribo-induced graphitization of the Ti3C2 coatings. The existence of the transfer film effectively inhibits the occurrence of abrasive wear and adhesive wear, thus significantly reducing friction and wear. Based on the above research results, MXene coatings are prepared on the graphite surface to improve the self-lubrication properties and the antioxidant properties. Yi et al. [36] achieved a robust macroscale superlubricity state with a CoF of 0.002 by introducing Ti3C2TX MXene nanoflakes in glycerol at Si3N4/sapphire interfaces. The friction reduction of MXene–glycerol is attributed to the in situ formation of the tribofilm containing Ti3C2TX MXene nanoflakes on the friction pairs. Wait et al. [37] presented a number of layer-dependent friction properties of the single-to-four-layer flakes of Ti3C2Tx MXene and demonstrated the superlubricity of single-layer MXene as well as the effect of the layers of Ti3C2Tx in an inert nitrogen atmosphere (with a CoF as low as 0.0039 for a bi-layer). The solution-processed multi-layer Ti3C2Tx-MoS2 blends were spray-coated onto rough 52100-grade steel surfaces as a solid lubricant. Ti3C2Tx-MoS2 nanocomposites led to superlubricious states, indicating a synergistic mechanism because the formation of an in situ robust tribo-layer was responsible for the performance at high contact pressures (>1.1 GPa) and sliding speeds [38,39].
Impregnated zinc phosphate graphite has a high CoF at high temperatures, and its comprehensive tribology needs to be improved. In this paper, two-dimensional layered MXene coatings were prepared on the impregnated zinc phosphate graphite surface by electrophoretic deposition to reduce friction and improve the tribological properties of graphite. The novelty of this research is to deposit the MXene coatings on the surface of the graphite and study the high-temperature anti-friction mechanism of the MXene coatings. The purpose of this paper is to improve the tribological performance of the graphite at different temperatures, especially at elevated temperatures, and to improve its high-temperature oxidation resistance.

2. Experimental Details

2.1. Composition and Performance of the Impregnated Zinc Phosphate Graphite

The impregnated zinc phosphate graphite material used was bought from Morgan New Materials Co., Ltd. (Shanghai, China). The impregnated zinc phosphate graphite material has a Shao hardness of 90 HS, a density of 2.05 g/cm3, a porosity of 0.5%, a compressive strength of 211 MPa, and a bending strength of 77.4 MPa. The physical properties are shown in Table 1.

2.2. Preparation of the MXene Coatings

Electrophoretic deposition (EPD) is an effective technique to construct coatings on the surface of materials. The EPD process includes two main steps: electrophoresis and deposition. During electrophoresis, charged particles or macromolecular aggregates can move towards an oppositely charged electrode in liquid medium under the influence of an externally applied electric field. The key parameters controlling EPD include precursor solution/suspension characteristics, the applied electric field, and the deposition time. EPD should be performed at moderate voltages and concentrations to achieve uniform, dense, and adhesive coatings without compromising the deposition rate. The deposition thickness increases with the deposition time at a constant rate when using a constant current during EPD. The preparation process of the electrophoretic deposition of the MXene coating is shown in Figure 1. Firstly, deionized water is used as the solvent to prepare the Ti3C2Tx dispersion solution with a concentration of 1 mg/mL, and then magnetically stirred for 2 h to obtain the initial dispersion solution. Then, the obtained dispersion solution is ultrasounded in the ultrasonic machine for 45 min, until it is fully dispersed. Furthermore, the multi-layer Ti3C2Tx is peeled off to a certain extent into fewer layers or a single layer, which is good for the subsequent deposition and lubrication performance of the coating. After that, the impregnated phosphate graphite pin is connected to the electrode holder and partially immersed in the dispersion solution. The impregnated phosphate graphite pin is used as the electrode at both poles, and the voltage is applied between the two poles. After the deposition is completed, the graphite pin is taken out and dried naturally to complete the preparation of the coating. The important parameters are the deposition voltage and the deposition time. In order to investigate the effect of deposition voltage on the coating properties, MXene coatings were prepared under three different deposition voltages of 5 V, 10 V, and 15 V, respectively. The distance between the electrodes was 15 mm.

2.3. The Microstructure Characterization and Tribological Properties of the MXene Coatings

The tribometer (MFT5000, Rtec instruments, San Jose, CA, USA) in a ball-on-flat contact in the rotary configuration was used to investigate the tribological properties of the coatings at different temperatures. In order to accurately reflect the operating state of the friction pair, this test rig applied loading to the upper specimen and rotation to the lower specimen, thereby creating rotational friction between the upper and lower specimens in surface contact. The test rig mainly consisted of four main systems: the transmission system, the loading system, the pressurized fluid circulation system, and the testing system. All samples were ultrasonically cleaned with absolute ethanol for 10 min and dried with dry air before the tests. All the friction experiments were carried out in atmosphere air with a sliding speed of 0.05 m/s and a load of 10 N to ensure the same friction environmental conditions. The tribotest temperatures were room temperature, 100 °C, 200 °C, 300 °C, and 400 °C, respectively. The moving ring was 9Cr18 high-carbon and high-chromium stainless steel, which has excellent wear resistance and corrosion resistance, and is one of the most commonly used moving ring materials in graphite sealing. The samples were heated to the specific temperature and kept there for 15 min to make sure the heating balance was complete. Then, load was applied to the samples and the effect of the thermal deformation of the substrate and coatings was eliminated. The testing results were averaged from three repeated tests.
Scanning electron microscopy (SEM, Gemini SEM 500, Carl Zeiss, Jena, Germany) and laser scanning confocal microscopy (LSCM, OLS4000, Olympus, Tokyo, Japan) were used to observe the morphologies of the worn surface and the depths of the wear scars, and then the wear rate of the coatings was calculated after the tribotests.

3. Results and Discussion

3.1. Microstructure of Graphite and Ti3C2Tx

The surface morphology and the element distribution of the impregnated zinc phosphate graphite were characterized by SEM and EDS, as shown in Figure 2. Combined with the EDS results, it was found that the impregnated zinc phosphate is finely and evenly distributed on the graphite surface. The graphite surface is evenly distributed and covered, which corresponds to its relatively lower porosity.
The surface of the impregnated zinc phosphate graphite was characterized by Raman spectrometer, as shown in Figure 3. The ID/IG value of the impregnated zinc phosphate graphite is only 0.43, which indicates that the graphite is in a highly ordered state in its initial state [40,41]. Meanwhile, the high strength of 2D indicates that the accumulation of graphite is weak, which is advantageous for the formation of a transfer film on the contact surface.
MXene is a two-dimensional layered material, which is first prepared by etching Ti3AlC2 on the precursor material to obtain Ti3C2Tx, which is then named MXene. The MXene material was bought from Xinxi Technology Co., Ltd., Foshan, Chian and prepared by the minimal reinforcement layering method. The microstructure of Ti3C2Tx was characterized by SEM, as shown in Figure 4. The layered structure of Ti3C2Tx was found clearly according to the SEM image, which indicates the low shear resistance characteristics of 2D materials and is helpful for the formation of the lubrication film [42]. And it has good dispersion in aqueous solutions, which provides a good basis for the preparation of the coatings by electrophoretic deposition.

3.2. Characterization of MXene Coatings

The surface morphology of the graphite pin was characterized by SEM and EDS to investigate the influence of the deposition voltage on the morphology of the coatings, as shown in Figure 5. When the deposition voltage was 5 V, the MXene coating was relatively flat, and the Ti3C2Tx was aggregated, which did not completely cover the graphite surface. When the deposition voltage was 10 V, the MXene coating was not observed on the surface. However, many zinc phosphate crystals were originally impregnated in the graphite pores and crystallized on the graphite surface. When the deposition voltage was 15 V, MXene basically covered the graphite surface, but the deposited MXene coating on the graphite surface was messy and the coatings were not smooth.
The deposition mechanism of Ti3C2Tx on the impregnated zinc phosphate graphite was analyzed based on the morphology of the graphite surface and on the phenomena that occurred during deposition. When the deposition voltage was 5 V, the Ti3C2Tx in the dispersion solution migrated slowly; the deposition was relatively slow, but the deposition was smooth. The Ti3C2Tx did not completely cover the surface, and there was graphite exposed, which is helpful for the graphite and Ti3C2Tx to form a lubricating film together during the friction process. When the deposition voltage was 10 V, the zinc phosphate impregnated in the graphite pores was crystallized under the action of the voltage, and the migration speed of the Ti3C2Tx sheet was not enough for it to be deposited quickly on the graphite surface to prevent its further precipitation. In addition, during the deposition process, bubbles were observed at the electrode, indicating that the reaction of electrolytic water occurred during the deposition process, and the bubbles burst after upwelling, which also hindered the deposition of Ti3C2Tx. At the deposition voltage of 10 V, the migration rate of the Ti3C2Tx was not enough to deposit on the surface of the graphite under the influence of the electrolytic water reaction and zinc phosphate crystallization. At the deposition voltage of 15 V, many bubbles was observed during the deposition process, indicating that the reaction of the electrolytic water was intense at this time, the migration speed of Ti3C2Tx was faster, and it can be deposited on the surface of the graphite under this influence, but the bubbles generated by the reaction of the electrolytic water broke at the electrode, destroying the structure of the deposited film. The resulting Ti3C2Tx film was messy and not as smooth as the film deposited at 5 V deposition voltage.

3.3. The Tribological Properties of MXene Coatings

The friction and wear experiments of the MXene coatings on the impregnated zinc phosphate graphite pins prepared at the different deposition voltages were carried out from room temperature to 400 °C to explore the friction and wear behaviors of the MXene coatings on the surface of the impregnated zinc phosphate graphite. The friction pair was 9Cr18 steel, the load was 10 N, and the relative velocity was 0.05 m/s.
Figure 6 shows the CoF and wear rate of the MXene coatings at the deposition voltage of 5 V. The CoF of the MXene coatings at the 5 V deposition voltage is about 0.2, which does not largely differ from room temperature to 400 °C and is relatively stable.
At room temperature, the CoF was about 0.12 in the initial stage and increased to about 0.22 after a period of running-in until the end of the friction test, and the average of the CoF was about 0.22. At 100 °C, the CoF was about 0.16 in the initial stage, and firstly increased and then decreased after a period of running-in. The average CoF was about 0.23, although the CoF increased slightly during the period at the end of the friction test. At 200 °C, the CoF was about 0.09 in the initial stage, and firstly increased and then gradually decreased. The average CoF was about 0.18, which was the lowest value. At 300 °C, the CoF was about 0.19 in the initial stage, and increased slightly to about 0.25 of the average CoF at a stable stage. At 400 °C, the CoF was about 0.17 in the initial stage, and increased slightly and reached a stable stage. The average CoF was about 0.21. The CoF of the MXene coatings on the graphite pin deposited at 5 V was relatively stable at room temperature but not at 200 °C. The coatings deposited at 5 V were smooth, which was attributed to the observed tribological performance. The CoF still remained at low friction levels even at elevated temperatures, and the friction process was stable with small fluctuations, indicating that the Ti3C2Tx coatings can effectively reduce the CoF at high temperatures [43]. The wear rate gradually increased with the increase in temperature. The average CoF was relatively high compared with the values found in the existing literature. MXene is unstable at high temperatures and prone to oxidation, and it is easily oxidized at high temperatures, especially in humid air, in water, at high temperatures, and in other conditions. Because MXene has poor electrochemical stability and is easily oxidized, this results in a decrease in the tribological properties. Thus, the CoF increases slightly from 200 °C to 300 °C, and then the CoF decreases at 400 °C.
Figure 7 shows the CoF and wear rate of the MXene coatings at the deposition voltage of 10 V. The CoF of the coatings on the graphite pins at the deposition voltage of 10 V was a little high compared with that at room temperature.
At room temperature, the CoF was 0.24 in the initial stage, and increased firstly and then decreased after a short period of fluctuation. This may be due to the fact that the Ti3C2Tx coatings could not be deposited on the surface of the graphite pin effectively after deposition at a 10 V deposition voltage, which led to the crystallization of the impregnated zinc phosphate in the graphite pores. These crystals increased the CoF during sliding. The average CoF was about 0.27. At 100 °C, the CoF was 0.19 in the initial stage, and increased gradually to about 0.23 at the end of the tribotest. The friction curve was very stable, and the average CoF was 0.23. At 200 °C, the CoF was 0.22 in the initial stage, and then increased gradually to 0.40 until the end of the friction test, which means that the friction behaviors became poor. At 300 °C, the CoF was 0.22 in the initial stage, and gradually decreased to 0.2 at about 150 s, and increased to about 0.3 again, and the average CoF was about 0.3. At 400 °C, the CoF was 0.06 in the initial stage, and then increased gradually to about 0.4. After about 300 s, the CoF decreased and then remained at about 0.33 of the average value. The CoF was high at 300 °C and 400 °C, and the friction process fluctuated slightly. The wear rate was also high, and the crystallization of the zinc phosphate impregnation led to an increase in the porosity of the graphite surface, which reduced the anti-wear behavior and the oxidation resistance [44,45].
Figure 8 shows the CoF and the wear rate at the deposition voltage of 15 V. The Ti3C2Tx coatings deposited at 15 V had stable friction with the increase in temperature.
At room temperature, the CoF was 0.24, and rapidly rose to 0.35 and then decreased to around 0.2, and finally increased to about 0.23. The average CoF was 0.22. At 100 °C, the CoF was 0.16 in the initial stage, and then increased to 0.34 and decreased to 0.18, and finally increased to about 0.27 at the end of the friction test. The average CoF was 0.25. At 200 °C, the CoF decreased from 0.26 to 0.12 and then increased gradually to about 0.33. The average CoF was about 0.28. At 300 °C, the CoF was 0.25 in the initial stage, and increased rapidly to 0.37 and then gradually decreased to about 0.26 at the end of the friction test. The average CoF was 0.27. At 400 °C, the CoF was about 0.12, and then increased rapidly to 0.35 and gradually decreased to 0.28 at the end of the friction test. The average CoF was 0.28. The wear rate was slightly high compared with that at other voltages.
Figure 9 shows the average CoF of the graphite and coatings. It was found that the coatings have excellent anti-friction behaviors, and the coatings deposited at the deposition voltage of 5 V, among the coatings at the other deposition voltages, have the best anti-friction behaviors. The CoF curve of the MXene coatings at the 5 V deposition voltage is relatively stable and smooth.
At room temperature, the CoF of graphite is lowest and the CoF of the coatings deposited at 10 V is highest. After room temperature, the CoF of the coatings deposited at 5 V is lowest among the different temperatures. However, at 100 °C, the CoF is almost the same and the CoF of graphite is highest. The CoF of the coatings deposited at 5 V is lowest. At 200 °C, the CoF of the coatings deposited at 5 V remains lowest and the CoF of the coatings deposited at 10 V is highest. At 300 °C, the CoF of the coatings deposited at 5 V is lowest and the CoF of the coatings deposited at 10 V is highest. The CoF of graphite increases compared with that at 200 °C. At 400 °C, the CoF of graphite increases to the maximum value, which may involve the oxidation of graphite.
For graphite, the CoF is lowest at room temperature and the CoF is highest at 400 °C. For the coatings at 5 V, the CoF is lowest from 100 °C to 400 °C, which indicates that the MXene coatings at 5 V are suitable for applications at a wide range of temperatures, especially high temperatures. For the coatings at 10 V, the CoF fluctuates with the increase in temperature. For the coatings at 15 V, the CoF is relatively stable with the increase in temperature.
Figure 6b, Figure 7b and Figure 8b show the wear rate of the coatings deposited at 5 V, 10 V, and 15 V. It is convenient to compare the CoF and wear rate at each temperature and each coating. Figure 9b shows the comparison results of the wear rate of the coatings. High electrophoresis voltage may destroy the structure of the coatings and generate too much heat, and high temperatures damage the properties of the coatings, causing the high wear rate of the coatings. Therefore, the electrophoretic voltage needs to be properly controlled and adjusted during the production process.

3.4. The Wear Mechanism of MXene Coatings

According to the above experimental results, the Ti3C2Tx coatings deposited at 5 V have the best anti-friction performances and most stable CoF values. Therefore, the worn surface of the 9Cr18 steel for the sliding of the coatings deposited at 5 V was characterized to analyze the anti-friction mechanism. Figure 10 shows the worn surface of the steel, observed by optical microscope, after friction tests at different temperatures.
There was plowing wear on the worn surface at different temperatures. At room temperature, the wear was low, and there was a continuous and uniform transfer film at the wear scar. The highly ordered arrangement of the impregnated zinc phosphate graphite was attributed to the formation of a continuous and uniform transfer film. At the deposition voltage of 5 V, the Ti3C2Tx coatings did not completely cover the graphite surface. Moreover, the graphite and Ti3C2Tx coatings formed a lubricating film together during friction. However, the Ti3C2Tx coatings decreased the self-lubricating performance of the transfer film, creating high friction to a certain extent.
As the temperature increased, oxidation was observed during sliding. At 100 °C, a certain transfer film was also observed in the wear scar on the worn surface, but a less apparent transfer film, which corresponds to the results of the high CoF at various temperatures.
At 200 °C, it was observed that the plowing wear became serious at the wear scars. However, a continuous transfer film was formed, which was helpful for the anti-friction behaviors of the coatings. At 300 °C, the depth of the wear marks became high, and continuous transfer films were formed in the wear scars, and the oxidation phenomenon also occurred. At 400 °C, the transfer film on the worn surface became less apparent, meaning that the oxidation phenomenon was serious at this time.
Figure 11 shows the three-dimensional morphologies of the worn surface characterized by laser confocal microscopy to analyze the worn surface. The depth in the middle was low and the depth on both sides was high in the wear scars, indicating that a transfer film was formed during the friction process. At room temperature, the transfer film was thin, and the wear was less, and the transfer film was not easily damaged, which plays a stable and effective lubrication role. At 100 °C, the transfer film on the surface of the abrasion became thin and was widely distributed. At 200 °C, a thick transfer film was formed on the surface, and the transfer film was formed in the whole wear scar, which corresponds to the low CoF. At 300 °C and 400 °C, a transfer film was also observed, and the transfer film may contain some oxides.
SEM and EDS were used to observe and analyze the microstructure and element distribution of the wear scars, as shown in Figure 12. At room temperature, the transfer film was observed on the worn surface scattered in the friction area. It can be seen that in the transfer film, the Ti3C2Tx was embedded in the graphite and formed a transfer film together with the graphite. At 100 °C, there was no continuous transfer film formed in the wear scar, and the graphite and Ti3C2Tx were distributed in the form of particles in the friction area, which may have led to the relatively high CoF. At 200 °C, the wear scar was shallow, and the transfer film was relatively flat, mainly composed of graphite. At 300 °C, the wear scar on the worn surface was very shallow, and the graphite and Ti3C2Tx were adhered to the surface of the 9Cr18 steel. At 400 °C, a relatively obvious bulge was observed on the worn surface, and the surface of the transfer film was rough, and the graphite and Ti3C2Tx were scattered in the transfer film. The wear mechanism of the MXene coatings was mainly abrasive wear and adhesive wear.
Figure 13 shows the Raman spectra of the transfer film in the wear area of the 9Cr18 disk after various temperature experiments. At different temperatures, the Raman spectra of the transfer film at the wear marks show very distinct D and G peaks, which demonstrates that a lubricating film is formed at the abrasion marks as the graphite wears during friction. Compared with the graphite before the experiment, the ID/IG value of the transfer film at the wear marks is significantly increased, indicating an increase in defects in the graphite transfer film after friction. In the range of RT to 300 °C, the value of ID/IG varies less, showing that in this range, the high temperature is less destructive to the graphite lubrication film. However, when the temperature reaches 400 °C, the value of ID/IG has a significant increase, when the lubrication film is more seriously damaged by temperature. At the same time, with the increase in temperature, the characteristic peaks of the oxides of Fe and Cr gradually appear in the Raman spectra, and the peak intensity gradually increases.
The wear marks of the graphite pins after the experiments were further characterized by SEM and EDS to analyze the lubrication mechanism, as shown in Figure 14. Visible graphite accumulation can be seen at the abrasion marks, and the presence of Ti3C2Tx is also confirmed by the distribution of Ti, which is generally consistent with the phenomenon observed in the abrasions on the disk surface. Combined with the results of the Raman spectra, it is known that the transfer film formed in the wear area is a combination of graphite and Ti3C2Tx deposited on the graphite surface. As the temperature increases, more pronounced wear marks can be observed on the graphite pin surface, corresponding to its gradually increasing wear rate, which is related to the oxidative failure of the graphite and the production of oxides [46].
Combined with the tribological experimental results and characterization results, the high-temperature friction and wear mechanisms of the electrophoretic deposition of MXene coatings on the impregnated zinc phosphate graphite surface are discussed, as shown in Figure 15. Impregnated zinc phosphate graphite has good orderliness and mono-layer properties, which gives it the ability to form the film. When the deposition voltage was 5 V, Ti3C2Tx was deposited on the graphite surface. After the deposition for 30 min, the Ti3C2Tx formed a coating on the graphite surface, but it did not completely cover the graphite surface. This allowed the graphite and the deposited Ti3C2Tx to easily form a transfer film together during friction. In the present paper, the tribological mechanisms involve the oxidation of graphite and the transfer films according to the experimental results. The MXene coatings participated in the formation of wear-resistant transfer films, which also proved that friction-induced transfer occurred during friction.
As a novel two-dimensional material, Ti3C2TX not only has a similar structure to graphene, but also has similar mechanical properties. Ti3C2TX has a similar Young’s modulus (~330 N/m) to graphene. This results in low inter-layer shear resistance, which contributes to the slip of the lubricant film it forms, thus reducing the CoF. At room temperature, Ti3C2Tx may decrease the lubrication performance because the graphite transfer film formed by the impregnated zinc phosphate graphite at room temperature has very good lubrication performance [47,48]. With the increase in temperature, the graphite in the transfer film begins a gradual trend of oxidation under the action of temperature, but the Ti3C2Tx in the transfer films can still play a lubricating role, so the friction process is stable [49,50].

4. Conclusions

Ti3C2Tx coatings were deposited on the surface of the impregnated zinc phosphate graphite by electrophoretic deposition to reduce the high-temperature CoF and improve the tribological properties of the impregnated zinc phosphate graphite. The Ti3C2Tx coatings were deposited at 5 V, 10 V, and 15 V, respectively. The tribological properties of the coatings were investigated. Finally, the Ti3C2Tx coatings deposited at 5 V may improve the tribological properties of graphite. The optimal deposition voltage is 5 V and the coatings deposited at 5 V have potential practical implications for high-temperature applications. The conclusions are listed as follows:
(1)
The Ti3C2Tx coatings deposited at 5 V are relatively smooth, and the Ti3C2Tx coatings partially cover the surface of the graphite, which helps to form a lubricating film with the graphite. The Ti3C2Tx coatings deposited at 10 V may lead to the crystallization of the impregnated zinc phosphate in the pores of the graphite surface and destroy the original structure of the graphite. There is more Ti3C2Tx in the coatings deposited at 15 V. During the deposition process, there is a severe reaction of electrolytic water, resulting in bubbles at the electrode. The bursting bubbles destroy the structure of the coatings.
(2)
The Ti3C2Tx coatings deposited at 5 V can effectively reduce the CoF of the friction pair of the impregnated zinc phosphate graphite and 9Cr18 steel at high temperatures, and the friction curve is relatively stable. The Ti3C2Tx coatings prepared at 10 V exhibit a high-temperature CoF. The Ti3C2Tx coatings deposited at 15 V also have high friction during the friction process.
(3)
The Ti3C2Tx coatings deposited at 5 V were covered in a transfer film from the graphite during the sliding, which plays a lubricating role. At room temperature, the Ti3C2Tx coatings improve the lubrication behaviors due to the good self-lubricating behaviors of the graphite. With the increase in temperature, the graphite particles in the transfer film are oxidized in the ambient air, but the Ti3C2Tx coatings in the transfer film can still play a lubricating role with the graphite in the transfer film and indicate the good tribological properties of graphite.

Author Contributions

Formal analysis, F.Z.; Resources, F.Z.; Writing—original draft, S.S.; Writing—review & editing, Q.Z.; Supervision, Q.Z.; Project administration, J.C.; Funding acquisition, S.G. All authors have read and agreed to the published version of the manuscript.

Funding

The present work is financially supported by the Liaoning Key Laboratory of Aero-engine Materials Tribology (LKLAMTF202401), the Henan Key Laboratory of High-performance Bearings (ZYSKF202302), and the Shanxi Province Science and Technology Cooperation and Exchange Special Project (202204041101021).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data is contained within the article.

Conflicts of Interest

There is no conflict of interests regarding the publication of this article.

References

  1. Dinc, S.; Demiroglu, M.; Turnquist, N.; Mortzheim, J.; Goetze, G.; Maupin, J.; Hopkins, J.; Wolfe, C.; Florin, M. Fundamental Design Issues of Brush Seals for Industrial Applications. J. Turbomach. 2002, 124, 293–300. [Google Scholar]
  2. Sayma, A.I.; Bré ard, C.; Vahdati, M.; Imregun, M. Aeroelasticity Analysis of Air-Riding Seals for Aero-Engine Applications. J. Tribol. 2002, 124, 607–616. [Google Scholar] [CrossRef]
  3. Zhao, Y.; Zhang, G.; Wang, J.; Wang, H.; Zhao, W.; Zeng, Q. Tribological properties of low-temperature time-dependent pretreated graphite for mechanical seal pairs in high-speed turbopump. Friction 2023, 12, 305–318. [Google Scholar]
  4. Zeng, Q.; Deng, Z.; Li, J.; Zhang, W. Advances in magnetic fluid seal and structures. J. Magn. Magn. Mater. 2024, 603, 172232. [Google Scholar]
  5. Torres, H.; Podgornik, B.; Jovičević-Klug, M.; Ripoll, M.R. Compatibility of graphite, hBN and graphene with self-lubricating coatings and tool steel for high temperature aluminium forming. Wear 2022, 490, 204187. [Google Scholar]
  6. Omrani, E.; Dorri Moghadam, A.; Menezes, P.L. New emerging self-lubricating metal matrix composites for tribological applications. In Ecotribology: Materials Forming, Machining and Tribology; Springer: Cham, Switzerland, 2016; pp. 63–103. [Google Scholar]
  7. Wang, R.; Zhang, F.; Yang, K.; Xiao, N.; Tang, J.; Xiong, Y.; Zhang, G.; Duan, M.; Chen, H. Important contributions of carbon materials in tribology: From lubrication abilities to wear mechanisms. J. Alloys Compd. 2024, 979, 173454. [Google Scholar]
  8. Zhao, W.; Zhang, G.; Dong, G. Friction and wear behavior of different seal materials under water-lubricated conditions. Friction 2020, 9, 697–709. [Google Scholar]
  9. Zhang, F.; Yin, P.; Zeng, Q.; Wang, J. Insights on the Formation Mechanism of Ultra-Low Friction of Phenolic Resin Graphite at High Temperature. Coatings 2021, 12, 6. [Google Scholar] [CrossRef]
  10. Zeng, Q.; Zhang, W. A Systematic Review of the Recent Advances in Superlubricity Research. Coatings 2023, 13, 1989. [Google Scholar] [CrossRef]
  11. Roe, M.; Torrance, A. The surface failure and wear of graphite seals. Tribol. Int. 2008, 41, 1002–1008. [Google Scholar]
  12. Shi, D.; Cai, L.; Zhang, C.; Chen, D.; Pan, Z.; Kang, Z.; Liu, Y.; Zhang, J. Fabrication methods, structure design and durability analysis of advanced sealing materials in proton exchange membrane fuel cells. Chem. Eng. J. 2023, 454, 139995. [Google Scholar] [CrossRef]
  13. Zhao, J.; Li, Q.; Li, S.; Li, S.; Chen, G.; Liu, X.; He, Y.; Luo, J. Influence of a carbon-based tribofilm induced by the friction temperature on the tribological properties of impregnated graphite sliding against a cemented carbide. Friction 2020, 9, 686–696. [Google Scholar] [CrossRef]
  14. Gao, R.; Huang, Y.; Zhou, X.; Ma, G.; Jin, G.; Li, T.; Wang, H.; Liu, M. Material system and tribological mechanism of plasma sprayed wear resistant coatings: Overview. Surf. Coat. Technol. 2024, 483, 130758. [Google Scholar] [CrossRef]
  15. Zhao, J.; Liu, Y.; Liu, D.; Gu, Y.; Zheng, R.; Ma, R.; Li, S.; Wang, Y.; Shi, Y. The tribological performance of metal-/resin-impregnated graphite under harsh condition. Lubricants 2021, 10, 2. [Google Scholar] [CrossRef]
  16. Mahto, N.K.; Tyagi, R.; Mishra, S. Sliding Wear of Copper-Impregnated Carbo-Graphite Under Different Conditions. J. Mater. Eng. Perform. 2024, 1–14. [Google Scholar] [CrossRef]
  17. Berman, D.; Erdemir, A.; Sumant, A.V. Approaches for Achieving Superlubricity in Two-Dimensional Materials. ACS Nano 2018, 12, 2122–2137. [Google Scholar] [CrossRef]
  18. Li, H.; Wang, J.; Gao, S.; Chen, Q.; Peng, L.; Liu, K.; Wei, X. Superlubricity between MoS2 monolayers. Adv. Mater. 2017, 29, 1701474. [Google Scholar] [CrossRef]
  19. Ramezani, M.; Ripin, Z.M.; Jiang, C.-P.; Pasang, T. Superlubricity of Materials: Progress, Potential, and Challenges. Materials 2023, 16, 5145. [Google Scholar] [CrossRef]
  20. Yi, S.; Li, J.; Rao, J.; Ma, X.; Zhang, Y. Alkyl-functionalized black phosphorus nanosheets triggers macroscale superlubricity on diamond-like carbon film. Chem. Eng. J. 2022, 449, 137764. [Google Scholar] [CrossRef]
  21. Gao, K.; Bin, W.; Berman, D.; Ren, Y.; Luo, J.; Xie, G. Self-Adaptive Macroscale Superlubricity Based on the Tribocatalytic Properties of Partially Oxidized Black Phosphorus. Nano Lett. 2023, 23, 6823–6830. [Google Scholar] [CrossRef]
  22. Tang, G.; Wu, Z.; Su, F.; Wang, H.; Xu, X.; Li, Q.; Ma, G.; Chu, P.K. Macroscale Superlubricity on Engineering Steel in the Presence of Black Phosphorus. Nano Lett. 2021, 21, 5308–5315. [Google Scholar] [CrossRef] [PubMed]
  23. Zeng, Q.; Ning, Z.; Pang, Z.; Wang, Z.; Zheng, C. Self-assembled multilayer WS2/GO films on amorphous silicon coating for enhancing the lubricating properties. Appl. Surf. Sci. 2023, 624, 157184. [Google Scholar] [CrossRef]
  24. Zeng, Q. High Temperature Low Friction Behavior of h-BN Coatings against ZrO2. Coatings 2022, 12, 1772. [Google Scholar] [CrossRef]
  25. Zeng, Q. Influence of CePO4 on high temperature anti-friction and anti-wear behaviors of nickel-based h-BN composite coatings. Diam. Relat. Mater. 2024, 148, 111421. [Google Scholar] [CrossRef]
  26. Naguib, M.; Kurtoglu, M.; Presser, V.; Lu, J.; Niu, J.; Heon, M.; Hultman, L.; Gogotsi, Y.; Barsoum, M.W. Two-dimensional nanocrystals produced by exfoliation of Ti3AlC2. Adv. Mater. 2011, 23, 4248–4253. [Google Scholar] [CrossRef]
  27. Huang, S.; Mutyala, K.; Sumant, A.; Mochalin, V. Achieving superlubricity with 2D transition metal carbides (MXenes) and MXene/graphene coatings. Mater. Today Adv. 2021, 9, 100133. [Google Scholar] [CrossRef]
  28. Rodriguez, A.; Jaman, M.; Acikgoz, O.; Wang, B.; Yu, J.; Grützmacher, P.G.; Rosenkranz, A.; Baykara, M.Z. The potential of Ti3C2Tx nano-sheets (MXenes) for nanoscale solid lubrication revealed by friction force microscopy. Appl. Surf. Sci. 2021, 535, 147664. [Google Scholar] [CrossRef]
  29. Chhattal, M.; Rosenkranz, A.; Kaihuan, Y.; Grützmacher, P.; Gong, Z.; Zhang, J. Comparative analysis of the solid lubrication performance-Ti3AlC2 versus Ti3C2Tx coatings. Ceram. Int. 2024, 50, 26391–26401. [Google Scholar] [CrossRef]
  30. Rosenkranz, A.; Wang, B.; Zambrano, D.; Henríquez, J.; Aguilar-Hurtado, J.; Marquis, E.; Restuccia, P.; Wyatt, B.; Righi, M.; Anasori, B. Solid-lubrication performance of Ti3C2Tx-Effect of tribo-chemistry and exfoliation. Mater. Today Nano 2024, 25, 100464. [Google Scholar] [CrossRef]
  31. Liu, X.; Le, K.; Wang, J.; Lin, H.; Liu, Y.; Jiang, F.; Yang, Z.; Li, H.; Xu, S.; Liu, W. Synergistic lubrication of multilayer Ti3C2Tx@ MoS2 composite coatings via hydrothermal synthesis. Appl. Surf. Sci. 2024, 668, 160400. [Google Scholar] [CrossRef]
  32. Marian, M.; Song, G.; Wang, B.; Fuenzalida, V.; Krauß, S.; Merle, B.; Tremmel, S.; Wartzack, S.; Yu, J.; Rosenkranz, A. Effective usage of 2D MXene nanosheets as solid lubricant—Influence of contact pressure and relative humidity. Appl. Surf. Sci. 2020, 531, 147311. [Google Scholar]
  33. Yin, X.; Jin, J.; Chen, X.; Rosenkranz, A.; Luo, J. Ultra-Wear-Resistant MXene-Based Composite Coating via in Situ Formed Nanostructured Tribofilm. ACS Appl. Mater. Interfaces 2019, 11, 32569–32576. [Google Scholar] [PubMed]
  34. Lian, W.; Mai, Y.; Liu, C.; Zhang, L.; Li, S.; Jie, X. Two-dimensional Ti3C2 coating as an emerging protective solid-lubricant for tribology. Ceram. Int. 2018, 44, 20154–20162. [Google Scholar]
  35. Yi, S.; Li, J.; Liu, Y.; Ge, X.; Zhang, J.; Luo, J. In-situ formation of tribofilm with Ti3C2Tx MXene nanoflakes triggers macroscale superlubricity. Tribol. Int. 2021, 154, 106695. [Google Scholar]
  36. Wait, J.; Josephson, G.; Wyatt, B.; Anasori, B.; Çolak, A. Environmentally stable nanoscale superlubricity of multi-layered Ti3C2Tx MXene. Carbon 2023, 213, 118284. [Google Scholar] [CrossRef]
  37. Macknojia, A.; Ayyagari, A.; Zambrano, D.; Rosenkranz, A.; Shevchenko, E.V.; Berman, D. Macroscale Superlubricity Induced by MXene/MoS2 Nanocomposites on Rough Steel Surfaces under High Contact Stresses. ACS Nano 2023, 17, 2421–2430. [Google Scholar]
  38. Lu, X.; Gu, X.; Shi, Y. A review on the synthesis of MXenes and their lubrication performance and mechanisms. Tribol. Int. 2023, 179, 108170. [Google Scholar]
  39. Ferrari, A.C. Raman spectroscopy of graphene and graphite: Disorder, electron–phonon coupling, doping and nonadiabatic effects. Solid State Commun. 2007, 143, 47–57. [Google Scholar] [CrossRef]
  40. Zeng, Q.; Ning, Z. High-temperature tribological properties of diamond-like carbon films: A review. Rev. Adv. Mater. Sci. 2021, 60, 276–292. [Google Scholar]
  41. Xiong, D.; Li, X.; Bai, Z.; Lu, S. Recent advances in layered Ti3C2Tx MXene for electrochemical energy storage. Small 2018, 14, 1703419. [Google Scholar] [CrossRef]
  42. Hurtado, J.; Grützmacher, P.; Henríquez, J.; Zambrano, D.; Wang, B.; Rosenkranz, A. Solid lubrication performance of few—And multilayer Ti3C2Tx coatings. Adv. Eng. Mater. 2022, 24, 2200755. [Google Scholar]
  43. Jia, Y.; Wan, H.; Chen, L.; Zhou, H.; Chen, J. Effects of phosphate binder on the lubricity and wear resistance of graphite coating at elevated temperatures. Surf. Coat. Technol. 2017, 315, 490–497. [Google Scholar]
  44. Zhai, W.; Bai, L.; Zhou, R.; Fan, X.; Kang, G.; Liu, Y.; Zhou, K. Recent progress on wear-resistant materials: Designs, properties, and applications. Adv. Sci. 2021, 8, 2003739. [Google Scholar]
  45. Luo, X.; Robin, J.; Yu, S. Effect of temperature on graphite oxidation behavior. Nucl. Eng. Des. 2004, 227, 273–280. [Google Scholar]
  46. Morstein, C.E.; Dienwiebel, M. Graphite lubrication mechanisms under high mechanical load. Wear 2021, 477, 203794. [Google Scholar]
  47. Han, H.; Qian, Z.; Meng, F.; Cui, Z. Tribological performances of graphite–MoS2 coating at various high temperatures. Proc. Inst. Mech. Eng. Part J J. Eng. Tribol. 2019, 233, 1888–1902. [Google Scholar]
  48. Ma, W.; Li, T.; Fang, Z.; Li, W.; Tang, H.; Zhang, L.; Yu, Y.; Qiao, Z. Effect of Ti3C2Tx MXenes on tribological and rheological properties of greases. Tribol. Int. 2024, 191, 109137. [Google Scholar]
  49. Rosenkranz, A.; Grützmacher, P.G.; Espinoza, R.; Fuenzalida, V.M.; Blanco, E.; Escalona, N.; Gracia, F.J.; Villarroel, R.; Guo, L.; Kang, R.; et al. Multi-layer Ti3C2Tx-nanoparticles (MXenes) as solid lubricants–Role of surface terminations and intercalated water. Appl. Surf. Sci. 2019, 494, 13–21. [Google Scholar]
  50. Xue, L.; Xu, Q.; Meng, C.; Lei, S.; Zhang, G.; Tang, M.; Zhai, W.; Yu, H.; Liu, X.; Du, C. Achieving the ultra-low friction and wear rate of PEEK-PTFE composites by Ti3C2Tx MXene reinforcement. Tribol. Int. 2024, 199, 110030. [Google Scholar]
Coatings 14 01567 g001
Figure 1. Preparation process of the MXene coatings by electrophoretic deposition.
Figure 1. Preparation process of the MXene coatings by electrophoretic deposition.
Coatings 14 01567 g001
Coatings 14 01567 g002
Figure 2. Surface morphology and element distribution of graphite.
Figure 2. Surface morphology and element distribution of graphite.
Coatings 14 01567 g002
Coatings 14 01567 g003
Figure 3. Raman spectrum of the impregnated zinc phosphate graphite.
Figure 3. Raman spectrum of the impregnated zinc phosphate graphite.
Coatings 14 01567 g003
Coatings 14 01567 g004
Figure 4. SEM images of Ti3C2Tx. (a) Low magnification; (b) high magnification.
Figure 4. SEM images of Ti3C2Tx. (a) Low magnification; (b) high magnification.
Coatings 14 01567 g004
Coatings 14 01567 g005
Figure 5. SEM and EDS of the deposition coatings at different deposition voltages: (a) 5 V; (b) 10 V; (c) 15 V.
Figure 5. SEM and EDS of the deposition coatings at different deposition voltages: (a) 5 V; (b) 10 V; (c) 15 V.
Coatings 14 01567 g005
Coatings 14 01567 g006
Figure 6. CoF and wear rate of MXene coatings at 5 V deposition voltage: (a) CoF and (b) wear rate.
Figure 6. CoF and wear rate of MXene coatings at 5 V deposition voltage: (a) CoF and (b) wear rate.
Coatings 14 01567 g006
Coatings 14 01567 g007
Figure 7. CoF and wear rate of the MXene coatings at 10 V deposition voltage: (a) CoF and (b) wear rate.
Figure 7. CoF and wear rate of the MXene coatings at 10 V deposition voltage: (a) CoF and (b) wear rate.
Coatings 14 01567 g007
Coatings 14 01567 g008
Figure 8. CoF and wear rate of the MXene coatings at 15 V deposition voltage: (a) CoF and (b) wear rate.
Figure 8. CoF and wear rate of the MXene coatings at 15 V deposition voltage: (a) CoF and (b) wear rate.
Coatings 14 01567 g008
Coatings 14 01567 g009
Figure 9. Average CoF and wear rate of the MXene coatings at different deposition voltages: (a) CoF and (b) wear rate.
Figure 9. Average CoF and wear rate of the MXene coatings at different deposition voltages: (a) CoF and (b) wear rate.
Coatings 14 01567 g009
Coatings 14 01567 g010
Figure 10. Surface wear morphology of steel at various temperatures: (a) RT; (b) 100 °C; (c) 200 °C; (d) 300 °C; and (e) 400 °C.
Figure 10. Surface wear morphology of steel at various temperatures: (a) RT; (b) 100 °C; (c) 200 °C; (d) 300 °C; and (e) 400 °C.
Coatings 14 01567 g010
Coatings 14 01567 g011
Figure 11. 3D morphology of abrasion marks on the surface of 9Cr18 steel at various temperatures: (a) RT; (b) 100 °C; (c) 200 °C; (d) 300 °C; and (e) 400 °C.
Figure 11. 3D morphology of abrasion marks on the surface of 9Cr18 steel at various temperatures: (a) RT; (b) 100 °C; (c) 200 °C; (d) 300 °C; and (e) 400 °C.
Coatings 14 01567 g011
Coatings 14 01567 g012
Figure 12. Wear marks and EDS on the surface of the 9Cr18 disk after various temperature experiments: (a) RT; (b) 100 °C; (c) 200 °C; (d) 300 °C; and (e) 400 °C.
Figure 12. Wear marks and EDS on the surface of the 9Cr18 disk after various temperature experiments: (a) RT; (b) 100 °C; (c) 200 °C; (d) 300 °C; and (e) 400 °C.
Coatings 14 01567 g012
Coatings 14 01567 g013
Figure 13. Raman spectra of the transfer film in the wear area of the 9Cr18 disk after various temperature experiments.
Figure 13. Raman spectra of the transfer film in the wear area of the 9Cr18 disk after various temperature experiments.
Coatings 14 01567 g013
Coatings 14 01567 g014
Figure 14. Wear marks and EDS on the surface of graphite after various temperature experiments: (a) RT; (b) 100 °C; (c) 200 °C; (d) 300 °C; and (e) 400 °C.
Figure 14. Wear marks and EDS on the surface of graphite after various temperature experiments: (a) RT; (b) 100 °C; (c) 200 °C; (d) 300 °C; and (e) 400 °C.
Coatings 14 01567 g014
Coatings 14 01567 g015
Figure 15. Schematic diagram of the lubrication mechanism of (a) uncoated graphite and (b) MXene–Graphite.
Figure 15. Schematic diagram of the lubrication mechanism of (a) uncoated graphite and (b) MXene–Graphite.
Coatings 14 01567 g015
Table 1. Physical properties of the impregnated zinc phosphate graphite.
Table 1. Physical properties of the impregnated zinc phosphate graphite.
MaterialHardness (HS)Density
(g/cm3)		Compressive Strength (MPa)Flexural Strength
(MPa)		Porosity
(%)
Impregnated zinc phosphate graphite902.0521177.40.5
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Zeng, Q.; Sun, S.; Gao, S.; Chen, J.; Zhang, F. MXene Coatings Based on Electrophoretic Deposition for the High-Temperature Friction Reduction of Graphite for Mechanical Seal Pairs. Coatings 2024, 14, 1567. https://doi.org/10.3390/coatings14121567

AMA Style

Zeng Q, Sun S, Gao S, Chen J, Zhang F. MXene Coatings Based on Electrophoretic Deposition for the High-Temperature Friction Reduction of Graphite for Mechanical Seal Pairs. Coatings. 2024; 14(12):1567. https://doi.org/10.3390/coatings14121567

Chicago/Turabian Style

Zeng, Qunfeng, Shichuan Sun, Siyang Gao, Jianhang Chen, and Fan Zhang. 2024. "MXene Coatings Based on Electrophoretic Deposition for the High-Temperature Friction Reduction of Graphite for Mechanical Seal Pairs" Coatings 14, no. 12: 1567. https://doi.org/10.3390/coatings14121567

APA Style

Zeng, Q., Sun, S., Gao, S., Chen, J., & Zhang, F. (2024). MXene Coatings Based on Electrophoretic Deposition for the High-Temperature Friction Reduction of Graphite for Mechanical Seal Pairs. Coatings, 14(12), 1567. https://doi.org/10.3390/coatings14121567

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop