Increase In Graphite Content Research Articles

Enhanced wear resistance of in-situ nanoscale TiC reinforced Ti composites fabricated by additive manufacturing

The poor wear resistance of Ti alloys limits its application in the orthopedic and dental surgery field. TiC as an ideal reinforcement phase can improve wear resistance due to its high hardness, low coefficient of friction, and good bio-compatibility. However, the wettability of the interface between the TiC and Ti matrix is poor, which leads to low mechanical properties and wear resistance. In situ TiC formed through the addition of a C source can enhance interfacial bonding. In this work, the Ti-graphite composites are prepared by Laser powder bed fusion (LPBF). On the one hand, the LPBF can prepare various complex porous shapes according to the personalized customized demand. On the other hand, the LPBF can provide a high cooling rate, suppressing grain growth and refining grains, and also can obtain equally distributed nanoscale TiC particles. The results show that the composites are mainly composed of Ti, TiC, and residual graphite. With the increase of graphite content, the amount of TiC increases and the grain becomes smaller, and the microhardness increases from 317 HV0.2 to 408 HV0.2. Meanwhile, the Ti-1.5 wt%Gr composite has a low friction coefficient, volume of wear, and wear rate, which is attributed to the high hardness of TiC particles and lubrication of graphite. The oxide on the surface of the wear mark is mainly composed of TiO2 and TiO. The main wear mechanisms of the composites are oxidation wear and adhesive wear.

Microstructural, mechanical, and wear properties of Sn-based solder alloy modified with graphite nanoparticles

This study investigated the microstructural, mechanical, and wear properties of the Sn-2.5 wt%Ag-0.4 wt%Cu-1.0 wt%In (SAC-1.0In) solder alloy including nano-graphite (0.6–1.2 wt%). The microstructural characteristics of several samples were investigated using optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive x-ray spectrometry (EDS), electron probe microanalysis (EPMA), x-ray diffraction (XRD), and x-ray photoelectronic spectroscopy (XPS). The results of this study revealed that the presence of nano-graphite particles stimulated the production of distinct intermetallic compound phases (IMC) identified as Ag3Sn, Cu6Sn5, and γ-InSn4. These IMCs are uniformly dispersed throughout the matrix. The results showed that the addition of nano-graphite particles did not significantly alter the morphology of the microstructure but reduced the particle size of these IMCs. This refining of precipitated IMC particles resulted in considerable improvements in the material’s mechanical properties. The wear properties of both unreinforced matrix and graphite composites were investigated utilizing a pin-on-disc tribometer. The addition of 0.6, 0.9, and 1.2 wt% graphite nanoparticles decreased the sliding wear rate. It is worth noting that the current study is deemed unique and novel in terms of total strain percent behavior as graphite content increases.

ANALYZING THE PROPERTIES OF A COMPOSITE OF PCL-GRAPHITE BY THE INJECTION MOLDING

Coral reefs are vulnerable to several natural phenomena such as ocean warming, acidification, coral diseases, and plastic pollution. In order to tackle these problems, scientists are now working on the development of biocomposites utilizing biodegradable polymers such as polycaprolactone (PCL). Graphite can be used in conjunction with PCL to enhance its characteristics. The work is centered around conducting water absorption experiments on a composite material consisting of PCL and graphite. The investigation employs PCL granular and graphite powdered materials. The materials undergo heating, crushing, and weighing processes to ascertain weight ratios. Next, the mixture is shaped into specimens. The product's shape and distribution of chemical constituents are analyzed using water absorption, hydrophobicity, FTIR, and SEM testing. The findings indicate that the water absorption diminishes as the concentration of graphite powder increases. An alloy containing 10% graphite had the highest water absorption rate. The hydrophobicity test assesses the ability of a specimen's surface to repel water by introducing NaCl droplets and observing droplet production. The contact angle value exhibits a direct correlation with the increase in graphite content. The FTIR study indicates that there are no changes in the functional groups, resulting in a limited connection between the PCL matrix and the graphite filler. The temperature during the injection molding process affects the microstructure of the polymer. Lower temperatures lead to reduced crystallization, whereas higher temperatures result in denser molecular groupings. Graphite is a highly suitable choice for use as a filler in a PCL matrix because of its layered structure, large surface area, and excellent capacity to effectively fill voids within the matrix.

Research on damage optimization of copper-carbon gradient composite materials for current-carrying friction

To meet the demand for damage optimization of current-carrying friction materials and based on the uneven distribution characteristics of damage, copper-graphite gradient composite materials were prepared using spark plasma sintering technology. These materials were paired with H62 brass, conducting damage optimization studies on copper-graphite gradient composite materials using a self-made current-carrying friction test machine. The results indicate that the copper-graphite gradient composite materials possess excellent current-carrying performance. With an increase of graphite content, the degree of mechanical damage and arc damage on the worn surface is optimized. The friction coefficient and wear rate of the material significantly decrease. When the content of graphite in the material is 5 wt% − 10 wt%, The material's damage optimization reaches the best and the wear rate is 9.7 × 10−4 mg·m−1. At this point, the predominant form of damage to the material is plastic deformation.

An experimental study on the effect of graphite microparticles on the mechanical and tribological properties of epoxy matrix composites

This article comprehensively discusses the mechanical and tribological properties of epoxy matrix composites filled with 100μm graphite particulates, at loadings ranging from 0 to 1wt%. The investigation also focuses on the effects of the graphite filler on the wear surface of the specimens, utilizing an optical microscope for analysis. The results revealed a significant decrease in the tensile strength of the composite, with a reduction of more than 50% observed at 1wt% graphite loading. However, the flexural strength exhibited an initial sharp increase at 0.1wt% graphite loading, followed by a decline at higher graphite contents. Moreover, both impact and hardness values demonstrated improvement as the graphite content increased. The addition of graphite particles led to a reduction in the friction coefficient, attributed to the solid lubrication capabilities of graphite. Furthermore, the wear rate exhibited a sharp decrease with an increase in graphite content due to the formation of a lubrication layer at the contact surface, effectively reducing the break-off of the specimen.

Mechanical, tribological, and morphological properties of SiC and Gr reinforced Al-0.7Fe-0.6Si-0.375Cr-0.25Zn based stir-casted hybrid metal matrix composites for automotive applications: Fabrication and characterizations

The main goal of this research is to meet the demanding need for developing lightweight materials with improved properties that are appropriate for several engineering applications. The investigators proceeded to considerable efforts to assess the mechanical, micro-structural, and tribological characteristics of Al-0.7Fe-0.6Si-0.375Cr-0.25Zn/10 wt%SiCP/3 wt%GrP-MMC, Al-0.7Fe-0.6Si-0.375Cr-0.25Zn/15 wt%SiCP/5 wt%GrP-MMC, and Al-0.7Fe-0.6Si-0.375Cr-0.25Zn/20 wt%SiCP/8 wt%GrP-MMC based hybrid metal-matrix nano-composites (HMMC's). These hybrid aluminum matrix nano-composites were fabricated using the liquid processing stir casting method for automobile, aviation, defense, and chemical handling sectors owing to their superior strength, and higher thermal conductive properties. The machinability of Al-0.7Fe-0.6Si-0.375Cr-0.25Zn/(SiCp + Grp) - MMC has received limited attention to date. Owing to its exceptional characteristics, this hybrid composite could take the role of cast iron or aluminum composites in a wide-variety multitude of engineering applications. The Mechanical properties of fabricated Hybrid-MMCs have been examined along with tribological properties & other factors, affecting the tensile strength of cast composites in this study. Additionally, the characterization has been performed through X-ray Diffraction (XRD), Energy Dispersive Spectrum (EDS), Scanning Electron Microscope (SEM), and Optical Microscopy. The fabricated samples of hybrid metal matrix nano-composites of Al-0.7Fe-0.6Si-0.375Cr-0.25Zn matrix have been tested for microstructure analysis, micro hardness test, density, tensile strength, and grain size. Microstructure study clears the claim of uniform distribution of SiC & Graphite particles in Al matrix alloy. An average tensile strength has been recorded as 258 MPa and a percent-elongation of 4.6 during the tensile test. Tensile-fractography findings have portrayed the intrinsic fractured-rupture microstructure of tensile-tested samples that seemed to have particle deformation breakage and pull-outs. The density of Al/(SiCp + Grp)-MMCs have been found to be 2.76 g/cm3 whereas the average hardness has been recorded at 120HV. An increase in graphite content in Al/SiC-MMC's provides a significant improvement in friction coefficient as well as a reduction in wear rate. Findings have observed that the wear rate is increased with increasing the sliding speed, however, it is almost constant between 300 and 600 rpm, and beyond this wear rate increases drastically. Likewise, the coefficient of friction also shows a considerable increase with the increase in sliding speed. As the composition of graphite in the material increases, a considerable decrease in the wear has been noted down because of the presence of tribo-layer formed between mating surfaces. A high value of applied load and high rotating speed imposed high deformation of the surface and increase in frictional force, as a result, an increase in wear rate. Wear rate increases with the increment in load during the wear test, while friction coefficient decreases. Hence, the development of HMMCs with better mechanical, microstructural, and tribological properties that can be utilized as cast iron or aluminum composites in a diverse spectra multitude of engineering applications involving the study's scientific insights and technological developments. Manufacturers in the myriads of industries, including aerospace, ground-transportation, thermal management, industrial, recreational, and infrastructure, could profit inventors/producers from the findings of the current study.

High-entropy diboride ceramics with graphite addition

Graphite is a widely used oxygen impurity-removing additive and a property-tuning second phase for diboride and carbide-based ultrahigh temperature ceramics (UHTCs). In recent years, high-entropy diboride (HEB) ceramics have attracted much attention for the development of better UHTCs. However, oxide impurity generally inhibits their densification and harms their properties. Here, (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)B2 ceramics added with different contents of graphite (HEB-xC, x = 0, 1, 2.5, 5, 10, 20 vol%) were prepared by spark plasma sintering. It was found that the added graphite acted as an oxygen-removing agent and the oxide impurity phase t-(Zr, Hf)O2 was converted to the (Hf, Ta)C-based solid solution carbide. With the increase in graphite content, the relative density increased from 89.4% for HEB-0 C to 100% for HEB-10 C. Based on the evaluated properties of the prepared specimens, including Young’s modulus, hardness, toughness, and thermal conductivity, the added graphite with an optimized content is important for a given started powder and processing to achieve good and balanced material properties.

Effect of graphite addition on microstructure and properties of TiC–Ti5Si3–SiC composite coatings reacted from Ti–SiC-graphite powders

A TiC–Ti5Si3–SiC composite coating was prepared using atmospheric plasma spraying by in-situ reaction of raw agglomerated Ti–SiC-graphite powders. The effect of graphite content on the reaction mechanism, microstructure, and properties of plasma sprayed TiC–Ti5Si3–SiC coatings was studied. The results indicated that, with the increase of graphite content, Ti and C preferentially reacted and the reaction feasibility between Ti and SiC reduced. The content of TiC in the reaction products and unreacted SiC increased, while the content of Ti5Si3 decreased. Among them, the TiC–Ti5Si3–SiC coating prepared using Ti–SiC-graphite powders with a molar ratio of 3:1:1 exhibits excellent comprehensive properties, dense microstructure (porosity: 11.76 %), highest hardness (1132 HV0.2), high bonding strength (scratch critical load: ∼44 N), and optimal wear resistance with a wear loss weight of ∼5 × 10 −4 g.

Study on the microstructure and properties of copper/graphite composites with two-step method and copper-modified graphite

In this experiment, copper was coated on the surface of graphite by chemical process. Besides, the microstructure and crystal structure of copper-coated graphite were characterized by SEM and XRD. Copper-plated C/Cu composite was prepared by SPS sintering technique of powder mixture by two-step method. In order to test the dispersion state of graphite in the composites and the phenomenon of interfacial dispersion, the effect of graphite content on the properties of copper-coated C/Cu composites was also an important point. Therefore, the microscopic characterization and performance test were carried out. The results show that magnetic stirring and high-energy ball milling ensure the uniformity of copper-coated graphite in copper matrix, and conducted structural grain refining. The grain size of copper, and the properties of composite materials decreased with the increase of graphite content, such as relative density, conductivity and hardness. However, the further increase of graphite content leads to excessive grain size, the relatively long time of ball milling makes the fine grain become larger after sintering. When the graphite content is 1.0wt.%, the relative density, conductivity and hardness are 99.91%, 92.1%IACS and 67.7 HV, respectively. It is proved that copper-coated graphite and two-step powder mixing play an important role on improving the properties of the composites.

The Thermal Stability, Ablation Properties, Creamization Mechanism of Graphite/Zirconia (ZrO2)/Silicone Rubber Composites Containing Carbon Multicomponent Systems

It is urgent to improve the long-term ablation resistance of silicone rubber composites in order to meet the application requirements in the field of aerospace thermal protection. The graphite/ZrO2/silicone rubber (G/ZrO2/SR) composites prepared in this study were for that purpose. Firstly, the thermal stability and ablation properties of the G/ZrO2/SR composites were studied. The results showed that with the increase of graphite content, the initial decomposition temperature of the composites increased from 456.5 °C to 478.6 °C. The linear and mass ablation rates of the G/ZrO2/SR composite with 3 phr graphite were 0.048 mm/s and 0.0,220 g/s, respectively, which were decreased by 14.3% and 9.1%, compared with the ZrO2/SR composite without graphite. Moreover, the phase composition transformation and ceramization mechanism at high temperature of the G/ZrO2/SR composites containing carbon multicomponent system were studied. The results showed that the SR matrix completed the ceramic transformation during the ablation process and -Si-O-C pyrolysis products were formed and served as the skeleton of the ceramic layers. Finally, SiO2 and ZrO2 reacted with the graphite individually and the in-situ SiC and ZrC ceramic products formed enhanced the ceramic layers.

Tribological Properties of Cu-Based Self-Lubricating Materials Composed with Cu- or Ni-Plated Graphite

Cu-based self-lubricating materials can effectively adapt to complex natural environments and ensure consistency in materials used for switch transitions. These materials were tested through interface reinforcement research, improving their mechanical and tribological properties and providing a theoretical basis for new switch slide baseplate materials. Results showed that the coefficient of friction and wear weight loss of Cu-based self-lubricating materials decreased with an increase in graphite content after Cu and Ni plating on the graphite surface, reaching a minimum value at a graphite content of 6 wt.%. The coefficient of friction and wear weight loss of the Ni-plated material were reduced 11.1% and 85.6%, respectively, whereas the coefficient of friction and wear weight loss of Cu-plated materials were reduced 7.2% and 78.4%, respectively. Compared to Cu plating, Ni plating substantially enhanced the friction and wear performance of Cu-based self-lubricating materials. Cu and Ni plating increased the adhesion of the materials on the pin surface and the adhesive materials’ composition was consistent with the lubricating film, which changed the grinding mechanism between the pin and the disk. Ni plating had a stronger effect on the tribological performance of Cu-based self-lubricating materials than Cu plating.

Microstructure and high temperature wear behavior of in-situ synthesized carbides reinforced Mo-based coating by laser cladding

To broaden the application fields of Mo coating as wear resistant coatings for hot-end components in jet engines, the in-situ synthesized carbides reinforced Mo-based coatings were prepared by laser cladding. The effect of nickel-coated graphite (carbon source) on the microstructure, hardness and elevated-temperature wear behavior of coatings was studied. The wear behavior of coatings was evaluated by using a tribotester with a ball-on-disc configuration from room temperature to 1000 °C against Si3N4 ball in air. The results showed that the carbides played a role of dispersion-strengthening. The coatings were composed of Mo, Cr1.12Ni2.88, Cr9Mo21Ni20, Mo2C, Cr7C3 and Mo6Ni6C. The wear resistance of the laser clad coatings was significantly enhanced by the addition of nickel-coated graphite, and the wear rates firstly decreased and then increased with increasing graphite content. The friction coefficients of laser clad coatings increased with an increase in nickel-coated graphite content. There existed a critical content of nickel-coated graphite that best strengthened the tribological behavior from room temperature to 1000 °C. The coating with 6.0 wt% nickel-coated graphite exhibited favorable tribological properties due to the moderate ductility, carbides, lubricating layer and in-situ synthesized solid lubricants.

Texture, microstructure and mechanical properties of AA7075-graphite composites produced through mechanical alloying and hot-extrusion

This paper reports the effect of graphite and milling time on the texture, microstructure and mechanical properties of AA7075-graphite composites produced through mechanical alloying and hot extrusion. Characterization was conducted by scanning electron microcopy, transmission electron microscopy, X-ray diffraction, laser diffraction, electron backscatter diffraction and precession electron diffraction, and mechanical properties were evaluated by uniaxial tensile tests. Results show that particle and crystallite size of mechanically milled powders affect the grain size of extruded samples. Most of extruded samples exhibit deformation textures components, however, in-grain misorientation values were lower than 2°, which is an indicative of their recrystallization. The presence of deformation texture components in recrystallized samples is explained by the oriented nucleation mechanism. Hardness, yield strength (YS) and ultimate tensile strength increase, while elongation to fracture decreases, with the increase in graphite content and milling time. The size of recrystallized grains decreases with the increase in milling time and graphite content. Furthermore, YS varies with grain size according to the Hall-Petch relationship. Hardening of the investigated AA7075-graphite composites is enhanced by grain refinement, dispersion of Al4C3, Mg2Zn2 and Al2O3; and to a lesser extent by the random texture developed.

Using DEM method to study graphite migration of copper-based graphite composites during friction

The self-lubrication of copper-based graphite composites depends on the formation of a graphite lubricating film on the frictional interface, which results from the graphite migration from the matrix. In fact, the graphite migration process is difficult to observe and record during friction by experimental methods. In our work, a discrete element method (DEM) software “the Particle Flow Code in 2 Dimensions (PFC2D)” was employed to simulate and analyze the graphite migration dynamic process of copper-based graphite composites sliding against 45 steel. The simulation results show that a migrated graphite particle layer was formed on the composite surface during friction, and maintained dynamic equilibrium relied on graphite migration from the matrix. The graphite migration was affected by applied load: the larger the applied load was, the greater the migration depth and number of migration particles were. And the sliding speed has little effect on graphite migration. With increase of graphite content, the migration depth first decreased and then increased, and the number of migration particles increased. With increase of graphite cluster size, the migration depth first decreased and then increased, and the number of migration particles decreased. The simulation results were verified by test analysis on a self-made in-situ observation tribometer, the test results was consistent with simulation results.

A study on visco-elastic, thermal and mechanical characteristics of injection molded ABS/graphite composite

Acrylonitrile Butadiene Styrene (ABS) materials have been widely used in automotive and other manufacturing industries. To meet the specific requirements of industry the ABS materials are enhanced by adding fillers through compounding. Very few works are found for the improvement of viscoelastic and thermal characteristics of ABS material. This work is focused to prepare the thermoplastic composites of ABS with graphite filler and to analyze the dynamic mechanical, thermal and mechanical properties of composites. Thermoplastic composites were prepared with three different weight ratios (3, 6 and 9%) of graphite powder with ABS by employing a twin-screw extruder and the scanning electron microscopy (SEM) images confirmed the proper mixing of filler material with the matrix and the samples were prepared using injection molding machine. The viscoelastic properties of the composites were investigated through dynamic mechanical analysis (DMA) with three different frequencies of (0.5, 1 and 2) Hz and the DMA results indicate that the damping properties were significantly influenced by the presence of graphite particles in ABS. It was observed that the storage modulus (E’) is higher at the frequency of 2 Hz compared to the other two frequencies (0.5 and 1) Hz, but the loss modulus was almost the same at all three frequencies. The thermal stability and mass losses of the prepared samples, thermal gravimetric analysis (TGA) was performed and the TGA graphs showed the improvement in the thermal characteristics of neat ABS due to the addition of graphite filler. The DSC thermograms of neat ABS and ABS/graphite composites indicate that the glass transition temperatures of ABS/graphite composites were increased. The tensile strength increases up to 6 wt% of graphite and drastically drops at 9 wt% of the filler content. But the flexural strength of the ABS/graphite composites were reduced as the weight percentage of graphite content increases.

Influence of graphite content on fracture behavior of MgO–C refractories based on wedge splitting test with digital image correlation method and acoustic emission

Mechanical and thermal stresses are one of the main reasons causing the damage of MgO–C refractories in service. An in-depth understanding of the fracture behavior of MgO–C refractories is essential for the further development of high-performance MgO–C refractories. In this paper, effect of graphite content on fracture behavior of MgO–C refractories under wedge splitting test was investigated with the Digital Image Correlation (DIC) and Acoustic Emission (AE) technology. The results showed that the increase of graphite content in MgO–C refractories led to a reduction in brittleness and an improvement of thermal shock resistance. MgO–C refractories with higher graphite content were likely to generate crack at earlier loading stage and to have larger ultimate crack mouth opening displacement. It indicated a lower crack initiation resistance of MgO–C refractories and a better further damage propagation resistance. In addition, the proportion of crack in the MgO grains decreased and the tortuousness of crack path increased with the increasement of graphite content. It promoted the transformation of AE activity and energy dissipation from “burst type” to “slow release type” and the nonlinearity of MgO–C refractories mechanics behavior during failure process.

Room-temperature deposition of ZnO-graphene nanocomposite hybrid photocatalysts for improved visible-light-driven degradation of methylene blue

ZnO-graphene nanocomposites (NCs) of ZnO and graphite microparticles were directly deposited by a one-step kinetic spray process at room temperature on a nickel foam (NF) porous substrate. The ZnO-graphene NCs/NF with various graphite contents (25, 50, and 75 wt%) were utilized as hybrid photocatalysts for methylene blue (MB) degradation. Analysis of Raman spectra revealed the improvement of various disorder-related phonons, confirming the fragmentation of microparticles into the nano-size range in all the ZnO-graphene NCs/NF hybrid photocatalysts. Also, the degree of layer separation and fragmentation of micro-sized graphite in the ZnO-graphene NCs/NF was shown to be strongly dependent on the graphite content. The surface morphology of the nanostructured ZnO/NF thin films consisted of nanorods and nanosheets. The increase of graphite content in the ZnO-graphene NCs/NF hybrid photocatalysts was accompanied by a two-step morphology transformation into graphene nanoflakes and nanoflowers. The interfacial bonding states of the ZnO-graphene NCs/NF were investigated using X-ray photoelectron spectroscopy, which indicated synergy improvement by the evolution of multiple bonded states between the ZnO and graphene species in all the hybrid photocatalysts. UV–visible optical absorbance spectra revealed a decrease in the optical bandgap of the ZnO-graphene NCs/NF with graphene species incorporation, indicating the improvement of visible light harvesting. The NCs hybrid photocatalyst with 50 wt% graphite content exhibited the lowest bandgap of 2.9 eV compared with the nanostructured ZnO/NF with 3.18 eV. The photocatalytic activity of ZnO-graphene NCs/NF was evaluated using the degradation of MB under visible light irradiation. The NCs hybrid photocatalysts with 50 wt% graphite content exhibited the highest degradation efficiency and the highest reaction kinetics rate constant compared with the other nanostructured photocatalysts.

Experimental investigations on mechanical properties of Al7075/TiB2/Gr hybrid composites

This work focuses on synthesizing Aluminum 7075 based hybrid MMCs using graphite and Titanium di Boride as reinforcements via stir casting technique. The graphite content has been varied between 2 and 8 wt% in step of 2 wt%, whereas Titanium di-boride particle has been fixed with 5 wt%. The developed hybrid composites have been subjected to mechanical characteristics such as hardness, Ultimate Tensile Strength (UTS) and ductility. Hardness and UTS increases with increase in graphite content. Tensile evaluation was carried out as per ASTM-A370 standard test procedure. Maximum of 74% and 68.85% improvement was recorded in hardness and UTS of hybrid composites. However, ductility reduces to the lowest value of 4.8% with graphite and titanium di boride’s inclusion.

Manufacturing and Tribological Behavior of Self-Lubricating Duplex Composites: Graphite-Reinforced Polymer Composites and Polymer-Infiltrated Metal Networks

Self-lubricating duplex composites comprising a top layer of polymer-based composites, i.e. bismaleimide (BMI) filled with a wide range of graphite (Gr) content (0–55 wt.%), and a bottom layer of infiltrated metal networks were manufactured by a hot compression-molded method. Melting points and polymerization temperatures of as-received BMI powder and BMI + Gr blends were investigated to determine infiltration process. The polymerization peaks move to higher temperatures with increase in graphite content. For cured polymer composites, the hardness measured by nanoindentation keeps increasing with graphite content without degradation up to 55 wt.%. Tribological performance of the top and bottom composites was examined individually, with focus placed on the development and stability of lubricating transfer film and tribofilm. For the top polymer composites, 25 wt.% Gr (or equivalently 17 vol.%) is sufficient to form lubricating transfer film and reduces the friction to the lowest ~ 0.15. For the bottom infiltrated metal networks, the BMI + 55% Gr-infiltrated network is adequate to develop fully covered transfer films and achieve low friction throughout the test. Those results shed lights on design and manufacturing of self-lubricating polymer matrix composites on metallic components that undergo severe running conditions.

Microstructure and Properties of Copper–Graphite Composites Fabricated by Spark Plasma Sintering Based on Two-Step Mixing

The microstructure and properties of Copper-Graphite Composites (CGC) prepared by spark plasma sintering (SPS) based on two-step mixing and wet milling were investigated. The results showed that Cu powders were rolled into Cu flakes during milling, and their size significantly decreased from 23.2 to 10.9 μm when the graphite content increased from 1.0 wt.% to 2.5 wt.%. The oxidation of Cu powder was avoided during two-step mixing and wet milling. After spark plasma sintering, the graphite powders of the composites were mainly distributed at Cu grain boundaries in granular and flake shapes. The mean size of Cu grains was 9.4 um for 1.0 wt.% graphite content and reduced slightly with the increasing of graphite content. Compared with other conventional methods, the composite prepared by two-step mixing and SPS achieved higher relative density, electrical conductivity, and micro-hardness, which, respectively, reduced from 98.78%, 89.7% IACS (International annealed copper standard), and 64 HV (Vickers-hardness) to 96.56%, 81.3% IACS, and 55 HV when the graphite content increased from 1.0 wt.% to 2.5 wt.%. As the graphite content increases, the friction coefficient and wear rate of the composite decreases. When the graphite content of CGC is 1.0 wt.%, the main wear mechanism was plastic deformation, delamination, adhesive, and fatigue wear. The adhesive and fatigue wear disappeared gradually with the increasing of graphite content.