“Structural superlubricity” is an important fundamental phenomenon in modern tribology that is expected to greatly diminish friction in mechanical engineering, but now is limited to achieve only at ...nanoscale and microscale in experiment. A novel principle for broadening the structural superlubricating state based on numberless micro‐contact into macroscale superlubricity is demonstrated. The topography of micro‐asperities on engineering steel substrates is elaborately constructed to divide the macroscale surface contact into microscale point contacts. Then at each contact point, special measures such as pre‐running‐in period and coating heterogeneous covalent/ionic or ionic/ionic nanocomposite of 2D materials are devised to manipulate the interfacial ordered layer‐by‐layer state, weak chemical interaction, and incommensurate configuration, thereby satisfying the prerequisites responsible for structural superlubricity. Finally, the robust superlubricating states on engineering steel–steel macroscale contact pairs are achieved with significantly reduced friction coefficient in 10−3 magnitude, extra‐long antiwear life (more than 1.0 × 106 laps), and good universality to wide range of materials and loads, which can be of significance for the industrialization of “structural superlubricity.”
A novel principle is proposed to assemble numberless “microscale superlubricity” into “macroscale superlubricity,” where the elaborately constructed micro‐asperities of rough engineering substrate play the role of splitting macro‐surface into micro‐points. Then, at each contact point, special measures, such as pre‐running‐in and heterogeneous 2D materials are devised to manipulate the interfacial ordered state, chemical interaction, and incommensurate configuration, thereby achieving robust macroscale superlubricity.
•The doping effects of Ag on DLC film were investigated thoroughly.•The Ag concentration in the film was controlled by changing Ar/CH4 ratios.•The vacuum tribological properties of Ag/DLC film were ...investigated firstly.•The mechanisms related to it were also discussed.
Silver (Ag)/diamond-like carbon (DLC) nanocomposite films with different Ag concentrations ranging from 0 to 11.02at.% were prepared by medium frequency unbalanced magnetron sputtering, in which the mixed Ar/CH4 of different volume ratios were used as the source gases. The doping effects of Ag concentration on microstructure, mechanical and vacuum tribological properties of the DLC films were investigated. It is found that the Ag concentration increased with the increasing Ar/CH4 ratios, accompanied with the increasing number and size of Ag crystalline. With moderate incorporation of Ag at 3.55at.%, the film (deposited at the Ar/CH4=65/45) maintained a low internal stress without considerable decrease of hardness and thus improved the adhesion strength. Moreover, the film showed low friction coefficient and the longest sliding lifetime in vacuum. The significant improvement in tribological properties of Ag/DLC nanocomposite films with moderate Ag concentration can be attributed to the low shear strength of Ag clusters on the surface, as well as the diffusion of Ag from the bulk to the surface and wear track.
▶ In recent years, a large number of reports on the friction and wear behavior of NiCrBSi coatings, which generally on room temperature seldom at high temperature, in particular, composite NiCrBSi ...coatings, at elevated temperature. ▶ In our article, NiCrBSi coating and its composite coatings doped with WC-Ni powders were fabricated by laser cladding. ▶ The high temperature friction and wear behavior of the two types of laser cladding coatings was comparatively investigated.
NiCrBSi coating and NiCrBSi/WC-Ni composite coating were produced on stainless steel by laser cladding. The friction and wear behavior of the laser cladding coatings sliding against Si
3N
4 ball at an elevated temperature of 500
°C was evaluated. The morphologies of the worn surfaces and wear debris were analyzed by means of scanning electron microscopy and three-dimensional non-contact surface mapping. Moreover, the elemental composition of the wear debris was determined by means of energy dispersive spectrometry. It has been found that the microhardness and wear resistance of the laser cladding coatings are excellent than that of stainless steel substrate. In particular, laser cladding NiCrBSi/WC-Ni composite coating shows better high temperature wear resistance than NiCrBSi coating, which is due to the formation of hard WC phase in the composite coating. Stainless steel substrate sliding against Si
3N
4 counterpart ball at an elevated temperature is dominated by adhesion wear, abrasive wear and severe plastic deformation and cutting; while both laser cladding coatings, involving only mild abrasive and fatigue wear when sliding against the ceramic counterpart, are able to prevent them from severe adhesion and abrasive wear.
•FC-TC4 and AC-TC4 alloys with more content of α phase were obtained by heat treatment.•Nano twins of TiV and TiAl3 were formed separately in FC-TC4 and AC-TC4 alloys.•Refined recrystallized grain ...and more high-angle grain boundaries of AC-TC4 alloy enhanced its mechanical properties.•The passivating ability of AC-TC4 alloy was best among three samples because of its microstructure.•The cavitation erosion resistance of Ti6Al4V alloys in artificial seawater was closely related to their mechanical properties and passivating ability.
The investigate about the effect of the microstructure of Ti6Al4V alloy on its cavitation erosion and corrosion properties in marine can provide the key basis for the application. On the basis of as-received Ti6Al4V(TC4) alloy, FC-TC4 and AC-TC4 alloys were prepared by heat treatment with the cooling method of a furnace and atmospheric environment, respectively. Then the microstructure evolutions of three samples were scrutinized and the effect of microstructure on their cavitation erosion and corrosion resistance was explored. The results showed that more recrystallized grains formed as well as its content of α grains and high-angle grain boundaries increased in AC-TC4 alloy. To FC-TC4 alloy, there was obvious grain growth apart from recrystallization. Moreover, many nanotwins of TiV and TiAl3 were formed separately in FC-TC4 and AC-TC4 alloys due to the dislocation migration during heat treatment. The microstructure evolution led the hardness and elastic modulus of AC-TC4 alloy were the best, followed by FC-TC4 alloy, that of TC4 were the worst. Similarly, passivating ability of AC-TC4 alloy was the best among three samples because of its microstructure. Although cracks extended along the grain boundaries under the action of continual cavitation erosion, the passivation film formed by TiO2 and Al2O3 would enhance their resistance to further corrosion and cavitation erosion in artificial seawater.
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High entropy ceramics (HECs) films (TiCrZrVAl)N were deposited on Inconel 718 alloys by multi-arc ion plating (MAIP) equipment at different nitrogen flow ratios RnN2/(N2+ Ar). The effects of Rn (0%, ...20%, 50%, 80%, 90%) on the evolution of microstructure, mechanical properties, and tribological properties of films were systematically studied. The films deposited at low Rn exhibited an amorphous structure and smooth cross-section, whereas the films at Rn of 50% and higher showed a face-centered-cubic (FCC) NaCl-type structure with loose columnar cross-section. With the increase of Rn, the content of the N element increased, the Cr element decreased, and other elements (Ti, Zr, V, Al) nearly remained stable. The films' hardness and elastic modulus increased gradually and reached the maximum value of 31.08 ± 1.81 GPa and 387.66 ± 12.49 GPa, respectively, when Rn was 80%. The films deposited at Rn of 20% invalided easily in tribology tests, whereas the films prepared under Rn exceeded 20% presented outstanding wear resistance and obtained the minimum wear rate of 7.4×10-16 m3/(N·m) when Rn is 80%.
Natural serpentine powders as functional fillers were incorporated to promote the anti-wear performance of phosphate-bonded solid coatings. Optimal mass percent of natural serpentine in phosphate ...coatings was first explored. Thereafter, to further stimulate strengthening effect of natural serpentine on tribological performance of phosphate composite coatings, harsher friction condition on the phosphate composite coatings was conducted. The experimental result indicated that the optimal incorporation of natural serpentine in phosphate coatings was 10 wt.%, through which anti-wear performance of phosphate coatings was significantly elevated. Additionally, accompanied by the increase of applied load and sliding speed, natural serpentine was gradually activated, and interfacial interactions between naturals serpentine and counterface were intensified. As a result, a continuous protective tribo-film was in situ formed on the counterface, through which serious furrows generated on the counterface were effectively self-repaired during the friction process. What’s more, further abrasion on both phosphate composite coatings and counterface was also greatly restrained.
Graphical Abstract
Natural serpentine as the enhanced phase was incorporated into phosphate bonded solid coatings. The experimental results indicated that when applied load and sliding speed were increased, transfer and adhesion of phosphate composite coatings on the counterface were apparently intensified, and simultaneously, serious furrows generated on the wear spot were obviously reduced. What’s more, a continuous tribo-film was in-situ formed on the counterface, through which the direct abrasion between phosphate composite coatings and counterpart steel ball was restrained, and therefore, the anti-wear performance of phosphate composite coatings was significantly promoted.
Different WC–Ni contents of NiCrBSi/WC–Ni composite coatings were produced on stainless steel by laser cladding. The effect of WC–Ni doping on the microstructure and tribological properties of the ...conventional NiCrBSi coating were systematically investigated. It has been found that the microhardness and wear resistance of the Ni-based alloy coatings are greatly increased after adding the WC–Ni particles, due to the formation of hard WC phase and a partial dissolution of WC particles on the Ni matrix after laser cladding. The laser cladding NiCrBSi/WC–Ni composite coatings, involving only mild abrasive and adhesive wear when sliding against the AISI-52100 counterpart (under ball-on-disk and ring-on-block wear test conditions). Thus, it is concluded that the incorporation of WC phase is an effective and attainable way to improve the tribological properties of conventional Ni-based alloys coatings.
► Different WC-Ni contents of NiCrBSi/WC-Ni composite coatings were produced by laser cladding. ► The effect of WC-Ni added on the microstructure, composition and microhardness was analyzed. ► The tribological properties of the Ni-based alloy coatings were investigated.
The reinforcing effect of graphene oxide (GO) and its derivatives for polymer matrices highly depends on their dispersion therein. Thus, a facile method was developed to enhance the dispersibility of ...GO via compounding with γ-methacryloxypropyltrimethoxysilane (GO–KH570). The interfacial interactions between GO and KH570, as well as the surface morphology, chemical composition and polarity, were investigated by molecular dynamics simulation combined with experimental methods. Findings indicate that KH570 can successfully graft onto the surface of GO nanosheets via the covalent bonding, and the polarity of the as-obtained GO–KH570 can be tuned by adjusting the dosage of KH570. Besides, the GO–KH570 was further used as the filler to improve performances of polyimide (PI) matrix. After using this GO–KH570 composite, the PI-based coating was endowed with excellent wear resistance and corrosion resistance properties. Particularly, PI/GO–KH570-2 coating with a GO–KH570-2 dosage of 0.5 wt% exhibits much higher hardness, showing promising potential as the candidate high-performance coating in aerospace and marine industries.
► Superhydrophobic SiO2 paper was fabricated by a simple spray-coating method. ► The superhydrophobic SiO2 paper showed a high water contact angle of 162±1° and a low water sliding angle of 3±1°. ► ...The superhydrophobic SiO2 paper was found to be highly transparent.
A simple technique for fabrication of superhydrophobic SiO2 paper was developed by spraying hydrophobic SiO2 nanoparticles suspension on paper substrate. The hydrophobic SiO2 nanoparticles were prepared by imparting octadecyltrichloro group on SiO2 nanoparticles. The as-prepared superhydrophobic SiO2 paper exhibted high water contact angle and low water sliding angle. Futhermore, the obtained superhydrophobic SiO2 paper was found to be highly transparent and the visibility of the character on the paper was not changed after spray-coating the hydrophobic SiO2 nanoparticles.
A type of CoMoCrSi coatings were fabricated by using HVOF technique, and the microstructures, mechanical properties and tribological behaviors at room temperature (RT) of the coatings annealed at ...800 °C for different time were investigated in detail. Annealed CoMoCrSi coatings exhibited better crystallization and more compact microstructures compared to as-sprayed coatings. The porosity of the annealed coatings reduced to 0.32–0.2%, and adhesive strength increased to 63.8–68.5 MPa, both of that were all reached at an equivalent level with the variation of the annealed time. The surface microhardness could be enhanced from 902.8 HV
0.3
for the as-sprayed coating to 1237.6 HV
0.3
for the coating annealed for 10 h, which could be attribute to more compact microstructures and hard nano-sized Cr
2
O
3
layer, that resisted indentation effectively. With the increasing of sliding distance at room temperature, the friction coefficients of the annealed coatings reached at 0.39–0.4, and the wear rates decreased to 0.88–1.59 × 10
–6
mm
3
N
−1
m
−1
, demonstrating enhanced tribological performance of the CoMoCrSi coating after heat treatment. Numerous metallic oxides, i.e., Cr
2
O
3
played a critical role in sustaining and anti-wear, and oxides, i.e., Co
3
O
4
, MoO
3
, and CoMoO
4
transferred to the Al
2
O
3
pair surface and formed a continuous transfer film during the friction test at RT, which directly reduced friction and leading to a low friction coefficient and wear rate.
