Self-lubricating Behavior Research Articles

The response of double press double sintered (DPDS) Al/CNT nanocomposites against wear, impact, and bending

Aluminum/carbon nanotubes (Al/CNTs) nanocomposites are intriguing prospects for mechanical and tribology applications. In this study, the double-pressing double-sintering (DPDS) method was used to create Al-based nanocomposites reinforced with CNTs. Al/CNT nanocomposites’ wear behavior, as well as their impact and bending strengths, were examined in relation to CNT content (1, 2, 4, 8 and 12 weight percent) and diameter (8, 20 and 40 nm). The wear behavior of Al/CNT nanocomposites was improved upon increasing the content from 0 to 8 wt.% and diameter sizes of CNTs compared with neat Al. This behavior is attributed to the self-lubricating behavior, clustering, and agglomeration of CNTs. The impact and bending strengths of the Al-8 wt.% CNTs with a diameter size of 40 nm increased by about 112%(17j) and 117%(265 MPa) compared with the neat Al sample, respectively. Impact resistance and bending strength were enhanced with increasing diameter of CNTs. The impact and bending strengths of these nanocomposites were impacted by CNT aggregation and the poor bonding strength of the Al/CNT interfaces (formation of Al4C3). SEM and TEM were used to analyze the worn and fractured surfaces of Al/CNT nanocomposites.

Tribological analysis and machine learning modeling of nickel-coated graphite reinforced A206 metal matrix composites

This paper demonstrates the successful dispersion of up to 8 wt% nickel-coated graphite (NiGr) particles in A206 aluminum alloys using stir mixing followed by casting. The microstructure, as well as selected mechanical and tribological properties, were thoroughly characterized. The nickel coating improves the dispersion of graphite, overcoming the challenges faced with uncoated graphite in aluminum melts and ensuring uniform distribution of NiGr particles. The A206/NiGr composites show potential as replacements for aluminum-tin alloys, particularly in bearing applications. Wear and friction performance were evaluated using a pin-on-disc tribometer with a 440 stainless steel counterface. Both as-cast and worn surfaces were examined via optical microscopy, scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Additionally, a supervised machine learning algorithm was developed to model the relationship between NiGr content, heat treatment, load, and wear rate. The results indicate that the coefficient of friction (COF) decreases with NiGr additions up to 4 wt%, demonstrating self-lubricating behaviour. However, the wear rate increased with higher NiGr content due to reduced hardness. The machine learning model effectively predicts wear rates based on NiGr percentage, heat treatment, and load, highlighting NiGr content as the most significant factor influencing wear, followed by load and heat treatment.

Effect of ZrO2 nanoparticles on the self-lubrication behavior of the linseed oil-loaded microcapsule/ epoxy composite coatings

Smart polymeric coatings play a crucial role in protecting steel surfaces from corrosion and wear. One of progressive smart behavior is self-healing behavior especially in self-healing epoxy coatings. Creating or improving the second smart behavior is known as a new trend for these smart materials. This study aims to investigate the effects of ZrO2 nanoparticles on the self-lubricating behavior as the second smart behavior of the linseed oil-loaded microcapsule/epoxy composite coatings. To do so, the in-situ polymerization method was used for the synthesis of linseed oil-loaded microcapsule. Results showed that the average size of prepared linseed oil-loaded microcapsules was 563 nm. The composite coatings were prepared by different content of ZrO2 nanoparticles (0, 3, 6, 9, 12, and 15 wt%) and constant content of linseed oil-loaded microcapsules (5 wt%). The tribological performance of samples was studied using pin-on-disk test. The worn surface of the samples was also studied using field emission scanning electron microscope (FESEM) images. Results proved that the frictional coefficient and wear rate of the samples were significantly decreased by increasing the concentrations of the ZrO2 nanoparticles up to 9 wt%. The lowest friction coefficient and wear rate values of 0.085 and 0.142 × 10−6 mm3/Nm were obtained for 5 wt% linseed oil-loaded microcapsules/epoxy with 9 wt% ZrO2 which were about 82 % and 88 % lower than those of pure epoxy coating.

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

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

Frictional shear-induced nanolamellar oxidation and transformation to oxide nanoparticles during pearlitic steel sliding

The in situ formation of a tribolayer composed of oxide nanoparticles on the wear surface is an important method for suppressing wear in metals with lamellar structures. However, the complex interaction between microstructure evolution and oxidation in a tribolayer obscures the formation mechanisms of nanolamellar oxidation and transformation. In this paper, samples of tribolayers at different oxidation stages were prepared by a focused ion beam (FIB) lift-out method. The dynamic evolution process and distribution of oxides in tribolayers during the dry sliding process were analyzed by characterization and molecular dynamics simulation. The nanolamellar oxidation processes and the effects of oxide nanoparticles on self-lubricating behavior were investigated. The results showed that oxygen diffused into the nanolamellae, resulting in continuous oxidation and the formation of an oxide/metal interface. The nanolamellar oxides were broken and refined in the further friction process and eventually transformed into oxide nanoparticles. The oxidation process was influenced by frictional shear, and the growth of oxides proceeded along the direction parallel to the nanolamellae with high-density dislocations. The above results provide a theoretical basis for the next step to improve the wear resistance and corrosion inhibition of metals by designing lamellar structures.

Formation mechanism and high-temperature self-lubricating behavior of (HfMoNbTaTi)C system single-phase high-entropy ceramics

Formation mechanism and high-temperature self-lubricating behavior of (HfMoNbTaTi)C system single-phase high-entropy ceramics

Self-lubricating behavior of a PdCuNiP glassy alloy by in-situ nanocrystallization during dry friction

In the present work, dry-sliding behavior of a PdCuNiP bulk glassy alloy (BGA) was studied and compared with that of a ZrAlNiCu BGA. The PdCuNiP BGA exhibits a 2-fold smaller coefficient of friction (COF) and a 100-fold lower wear rate than those of the ZrAlNiCu BGA, although the PdCuNiP BGA shows the smaller hardness and fracture toughness. The unprecedented low COF and wear rate of the PdCuNiP BGA stem from in-situ formation of an amorphous/ultrafine nanocrystalline structure layer on the wear-scar surface during the dry sliding. The Von-Mises stress simulation mapping in the contact area reveals that the effect of stress and deformation is not the primary cause for the nanocrystallization. The model calculated frictional heat generated during the friction process causes the in-situ nanocrystallization, which increases the hardness and strength of surface layer. The self-lubrication effect results from the effective suppression of the sliding-induced plastic deformation and surface roughening.

Investigating the effect of novel self-lubricant TiSiVN films on topography, diffusion and oxidation phenomenon at the chip-tool interface during dry machining of Ti-6Al-4V alloy

Machining of titanium alloys such as Ti-6Al-4 V can be very intimidating due to their low thermal conductivity leading to elevated cutting temperatures at the chip-tool interface (ICT). In this regard, the self-lubrication effect of coatings like TiSiVN represented by topography, oxidation, and diffusion at the chip-tool interface are crucial. Thus, the present work investigates the latter three mechanisms during dry machining of Ti-6Al-4 V titanium alloy with uncoated and TiSiVN coated Al2O3/SiC whiskers-reinforced ceramic cutting tools. The results reveal that the adhesion height (AH) and O% increases with cutting temperature, showing the dominant influence of cutting temperature on material adhesion and oxidation levels at the ICT. AH increases with increased cutting speed for both coated tools, indicating that the crater depth increment was not so severe for the coated tools. However, a drastic upward surge of crater depth for uncoated and TiSiN coated tools at 125 m/min cutting speed makes the crater edge near the ICT act as a chip breaker and facilitates the chip's bending away from the tool face causing reduction in chip bend angles (BA). Additionally, the TiSiVN coating accounts to a reduction of approximately 23% in AH and 18% in Ti%, and 37% lower oxygen levels at the highest cutting speed when compared to the uncoated tool primarily due to lower cutting temperatures and self-lubricating behavior.

Tribological considerations for failure restoration and maintenance of radial plunger pump against friction and abrasive wear behavior by microwave cladding of Ni-Graphene

Clean and efficient manufacturing techniques are in great demand in modern industrial facilities. New methods are being developed which are cleaner, environment-friendly, economical, and have better mechanical properties, among others. Due to hot corrosion, Tribological components are often subjected to wear and tear. Graphene (Gr) is a promising material with microwave absorption performance due to its self-lubricating properties, low density, and cementite (Fe3C) formation capabilities with iron. This work examined the effect of self-lubricating behavior and surface hardening of plungers of Austenite alloy by Ni-Gr cladding and glazing. Using silicon carbide abrasive media, a pin-on-disc wear tester was utilized for abrasion testing. Scanning Electron Microscopy (SEM), and X-ray diffraction (XRD) analysis supplemented with a microhardness test were performed to measure the improvement in the properties of clad samples. The results showed that temperature variation influences phase change and mechanical properties. The Ni-Gr cladding showed dense eutectic microstructure at 750° C. XRD’s results revealed that the disintegration of the cladding layer is reduced due to heat treatment along with the generation of the Fe3C phase. In addition, the deposited specimen confirmations maximum wear resistance and hardness characteristics with a minimum wear rate at 750 °C, just above the steel's first critical temperature.

Tribological behavior of Ni-based self-lubricating claddings containing sulfide of nickel, copper, or bismuth at temperatures up to 600 °C

Self-lubricating coatings extend the efficient dry-operational life of cutting and forming tools. In the current work, millimeter-thick NiCrBSi coatings with 10 wt% metal sulfide i.e. Ni3S2, CuS, or Bi2S3 were fabricated on a stainless steel substrate by laser cladding (in-situ alloying). Thermodynamic modelling utilizing the calculation of phase diagrams method (CALPHAD) was performed to predict the phase evolution during laser melting. Electron microscopy methods combined with X-ray diffraction and Raman spectroscopy were used to elucidate the developed microstructure. The coatings were further subjected to reciprocating dry sliding wear against a martensitic steel ball counterbody using a ball-on-plate configuration at 0.1 m/s and 50 N (Hertz contact pressure 1.7 GPa). The tests were conducted at room temperature (20), 400, and 600 °C. The results demonstrate a self-lubricating behavior of the sulfide coatings resulting in friction reduction by ⁓60 % at room temperature and ⁓40 % at 400 °C sliding, particularly for Bi2S3-added cladding, due to the prevalent existence of lubricious phases of chromium sulfide (CrxSy) along with others (NiBi, Bi) and leading to ‘self-healing’ phenomena. The results are reported in comparison to the unmodified NiCrBSi alloy.

Wear behavior of graphite self-lubricating Babbitt alloy composite coating on 20 steel prepared by laser cladding

A tin-based Babbitt self-lubricating composite coating was fabricated on 20 steels substrate by laser cladding through the mixed powders of nickel-plated graphite (Ni-Gr) composite powders and Babbitt alloy powders, aiming at improving wear resistance of Babbitt alloy coating. The results showed that the self-lubricating phase (graphite) coated by the nickel still remained elemental in the composite coating after laser cladding. Both Babbitt coating and Ni-Gr/Babbitt composite coating were uniform and density, without pore, cracks or any other defects, and were mainly composed of α-Sn solid solution phase, Cu6Sn5 and SnSb precipitated phases. The grains were obviously refined for the composite coating due to the heterogeneous nucleation. The nano-hardness (H), nano-hardness/elastic modulus (H/E) and (H3/E2) for the Ni-Gr/Babbitt composite coating were 1.15 GPa, 0.0137 and 1.9 × 10−4, which was much higher than that of the Babbitt coating with the value of 0.57 GPa, 0.0068 and 2.3 × 10−5. With respect to the increase in the nano-hardness, Ni-Gr/Babbitt composite coating also exhibited a low friction coefficient and wear rate with the value of 0.301 and 6.31 × 10−6 mm3/N∙m. The addition of Ni-Gr can effectively improve the self-lubricating and wear behavior of Babbitt alloys.

Deposition of Self-Lubricating Coatings via Supersonic Laser Deposition (SLD)

This paper describes the use of Supersonic Laser Deposition (SLD) to manufacture nickel/graphite composite coatings on titanium and aluminium substrates. Laser heating is critical for depositing coatings containing up to 13.3 vol% graphite. For a given feedstock composition, the resulting graphite content and average size of the graphite particles retained in the coating increases with laser power, until substrate melting occurs. The effect of the powder type, feedstock composition, and process conditions on coating structure is characterized. The friction and wear behaviour of selected coating compositions is examined. Nickel coatings containing 13.3 vol% graphite demonstrated self-lubricating behaviour with a stable coefficient of friction below 0.14 in pin-on-disc testing.

Self-lubricating behavior caused by tribo-oxidation of Ti3SiC2/Cu composites in a wide temperature range

Ti3SiC2/Cu composite, a new wide temperature range intelligent lubricating functional material, was fulfilled, for mechanical equipment components, by Spark Plasma Sintering process. The microstructure, composition and mechanical properties of the Ti3SiC2/Cu composites (TSC-Cu) were investigated. Additionally, the friction and wear behaviors of TSC-Cu sliding against Inconel 718 were conducted on a pin-on-disk configuration at a sliding speed of 0.5 m/s under a load of 5 N at 25–800 °C. For comparison, the tribological property of polycrystalline Ti3SiC2/Inconel 718 was measured in an identical condition. The worn surface of TSC-Cu was analyzed by SEM, EDS and XPS, respectively. The results indicated that TSC-Cu consisted of Ti3SiC2, TiC and Cu3Si. It was worth noting that the as-formed Cu3Si uniformly distributed along the grain boundary of Ti3SiC2. As for mechanical property, the addition of Cu increased the hardness, compressive strength of TSC-Cu but lowered its flexural strength. Compared with polycrystalline Ti3SiC2, the average friction coefficient of TSC-Cu was higher at 25–400 °C whereas it was lower at 600 °C and 800 °C. The lower friction coefficient was owing to the cooperative lubricating characteristic of tribo-oxidation films containing TiO2, SiO2 and CuO. Furthermore, the wear rate of TSC-Cu was absolutely lower than that of polycrystalline Ti3SiC2, which resulted from the effective surface strengthening effect of the as-formed hard TiC product. Moreover, the wear mechanism of the composite changed from three-body abrasion wear to adhesion wear and tribo-oxidation wear, with the temperature increasing from RT to 800 °C.

Self-lubricating behavior of VN coating catalyzed by solute Ag atom under dry friction and oil lubrication

The development of hard-yet-tough ceramic coatings with self-lubricating behavior is an urgent technological requirement to reduce mechanical friction losses and energy consumption. However, traditional ceramics possessing the limited self-lubricating ability and poor toughness have limited their practical applications. To tackle the above-mentioned problems, we modified ceramic material vanadium nitride (VN) to prepare the catalytically active V-Ag-N solid solution coating by magnetron sputtering and realized high hardness, high toughness, and excellent self-lubricating performance under dry friction and oil lubrication conditions. Through detailed experimental investigations, we explain the enhanced mechanism of both hardness and toughness because of solute Ag; moreover, the solute Ag can trigger the appearance of lubricating silver vanadate phase in dry friction and result in a low coefficient of friction. Besides, it was confirmed that the solute Ag atom would induce effectively catalytic ability for in situ formation of self-lubricating onion-like-carbon structures (OLCs) scrolls from base oil at the sliding interface. The novel strategy would be to open a window for more efficiently catalyzing the in situ formation of silver vanadate and OLCs scrolls activated by solute Ag atoms and more significantly improving the hardness and toughness, thereby further improving self-lubricating behavior under dry friction and oil lubrication conditions.

Novel Polyurethane Elastomer Modified by Hybrid Shell Nano-/Microcapsules for Unique Self-Lubricating Behavior

Self-lubricating microcapsules containing liquid paraffin as the core material were successfully synthesized with polyurethane (PU)/silica (SiO2) as the hybrid shell material using a sol–gel proces...

Enhanced self-lubricating and antibacterial activity by building hard-yet-tough Ta-Ag-N films on Ti-6Al-4V

The poor self-lubricating behavior and antibacterial activity of Ti-6Al-4V alloy hinder its medical applications in surgical instruments. And thus, Ag-based transition metal nitrides nanocomposite films on Ti-6Al-4V substrate where Ag existed in the form of nanoparticles have been commonly employed to improve the above properties. In this work, two kinds of Ag-based TaN films (~3 at.% Ag) with solute Ag atoms and Ag nanoparticles are respectively fabricated on the surface of Ti-6Al-4V alloy by magnetron sputtering, aiming to insight into their self-lubricating behavior and antibacterial activity. It is revealed that as Ag resides in form of solute atoms rather than nanoparticles in Ta-Ag-N films, the enhanced antibacterial activity, lower coefficient of friction (CoF) coupled with raised hardness (~39 GPa) and enhanced toughness can be achieved. Compared with the Ag nanoparticles, solute Ag atoms are considerably easier to form Ag2O in the atmosphere and to produce self-lubricating silver tantalate (AgTaO3) phase during the sliding, respectively contributed to the enhanced antibacterial activity and the drop in CoF. It suggests that the new strategy of incorporating solute Ag atoms into TaN can improve its self-lubricating ability and antibacterial activity for possibly extending the surgical instruments service life and reducing healthcare costs.

Effect of Fe on the high-temperature tribological behavior of NiAl/WC-Fex self-lubricating composites produced by thermal explosion

sIn order to improve the self-lubricating properties of NiAl-WC composite, a novel solid-lubricating material, NiAl/WC-Fex (x = 5, 10, 15 and 20 in weight percent) composites were synthesized by thermal explosion using Ni-Al-WC-Fe mixed powders. The microstructure, phase constituent, and tribological behavior of NiAl/WC-Fex composites at 800 °C were studied. According to the results, the addition of Fe could reduce the cracks of the composites. Compared with NiAl/WC, the increased Fe content could reduce the friction coefficient and high-temperature wear rate due to its enhanced ductility, oxidation, and low shearing strength. In particular, composite with 10 wt% Fe content had the lowest friction coefficient and wear rate because of the self-lubricating behavior of Fe at elevated temperature. The result also showed that the wear mechanism of NiAl/WC-Fex is related to Fe content at high-temperature.

The self-lubricating behavior and evolution mechanisms of the surface microporous friction interface of M50-(Sn-Ag-Cu) material

The friction interface structure has an important influence on the friction behavior of self-lubricating materials. In this paper, M50 material covered with surface micropores filled with Sn-Ag-Cu (MM-Salloy) was prepared by laser melt deposition. From 25–450 °C, the friction test results show that MM-Salloy exhibits distinguished tribological properties due to the existence of the microporous friction interface. Analysis indicates that Sn-Ag-Cu in surface micropores can dynamically precipitates to the worn surface of MM-Salloy to achieve a lubricating effect, and the increasing of temperature is beneficial to the dynamic precipitation of Sn-Ag-Cu. The whole friction process can be divided into the initial wear stage, fast wear stage and stable wear stage. At stable wear stage, the friction interface is mainly composed of a lubricant-rich surface lubrication layer and a subsurface load-bearing layer, which greatly improves the material's wear resistance. Especially at 350 °C, the surface lubrication layer and subsurface load-bearing layer are most easily formed.

Effect of amount of TiB2 and B4C particles on tribological behavior of Al7075/B4C/TiB2 mono and hybrid surface composites produced by friction stir processing

In this study, by friction stir processing, we fabricated several defect-free Al7075/B4C/TiB2 mono and hybrid surface composites containing various amounts of B4C and TiB2 reinforcements with high quality interfacial bonding with substrate, fine recrystallized matrix grains, and homogenous dispersion of ceramic particles through the matrix. The composite region of hybrid composite samples was more constricted compared with that of mono composite samples. All hybrid composites had more hardness and wear resistance in comparison to Al/B4C mono composite sample. Among different hybrid composites, the most optimal dispersion of ceramic particles, minimum size of B4C and TiB2 ceramic particles, the lowest friction coefficient, and the highest hardness and wear resistance belonged to the hybrid composite containing equal weight percentage of B4C and TiB2 ceramic particles (named 50%B4C-50%TiB2 hybrid composite). The hardness and wear resistance of the Al7075/B4C, Al7075/TiB2 mono composites and the 50%B4C-50%TiB2 hybrid composite were respectively enhanced by (91%, 121%, 107%) and (67%, 82%, 87%) regarding Al7075 base alloy. During wear, an unstable-simple tribolayer was formed on the surfaces of Al7075 base alloy and unreinforced FSPed samples; however, a more stable mechanically mixed tribolayer containing a mixture of oxygen, ceramic particles, and alloying elements of Al7075 base alloy and steel counterface was formed on the surface of the composite samples. The most stable tribolayer with the highest self-lubricating behavior belonged to the 50%B4C-50%TiB2 hybrid composite owing to the high amount of iron and very low amount of B4C in the tribolayer, resisting the subsurface of tribolayer to crack propagation.

Studies on mechanical and dry sliding wear behaviour of graphite/flyash reinforced aluminium (Al6Mg) MMCs

The present research work aims to the development and study the self-lubricating behaviour of hybrid MMC’s. Self-lubrication property of the composites exhibits better tribological properties as compared with other hybrid MMc’s. In the present research work investigates the possibility of using graphite/flyash for synthesizing aluminium (Al6Mg) based self-lubricating composite through stir casting technique. In this study keeping the flyash constant 8 wt% and by varying graphite (2–8 wt%). The distance, load, and velocity are the parameters are used for the study in the mechanical properties of composite were measured by using universal tensile testing equipment, Brinell hardness testing equipment and pin-on-disc test rig. The result reveals that the improvement in mechanical properties and tribological properties of filler filled composite specimen. Wear behaviour changes with respect to load and lowers the friction co-efficient with the effect of solid lubricants. The wear mechanism arestudied by using scanning electron microscope (SEM).