Search Results (86)

Graphene oxide (GO), a derivative of graphene, has attracted significant attention in tribological applications due to its unique structural, mechanical, and chemical properties. This review highlights the influence of GO and its composites on friction and wear performance across various engineering systems. The paper explores GO’s key properties, such as its high surface area, layered morphology, and abundant functional groups. These features contribute to reduced shear resistance, tribofilm formation, and improved load-bearing capacity. A detailed analysis of GO-based composites, including polymer, metal, and ceramic matrices, reveals those small additions of GO (typically 0.1–2 wt%) result in substantial reductions in coefficient of friction and wear rate, with improvements ranging between 30–70%, depending on the application. The tribological mechanisms, including self-lubrication, dispersion, thermal stability, and interface interactions, are discussed to provide insights into performance enhancement. Furthermore, the effects of electrochemical environment, functional group modifications, and external loading conditions on GO’s tribological behavior are examined. Despite these advantages, challenges such as scalability, agglomeration, and material compatibility persist. Overall, the paper demonstrates that GO is a promising additive for advanced tribological systems, while also identifying key limitations and future research directions. Full article

In this study, a Ag/ZrO₂ hybrid coating prepared by the sol–gel method on a β-type Ti45Nb alloy was applied by the spin coating technique, and the microstructural, mechanical, electrochemical, and tribological properties of the surface were evaluated in a multi-dimensional manner. The hybrid solution was prepared using zirconium propoxide and silver nitrate and stabilized through a low-temperature two-stage annealing protocol. The crystal structure of the coating was determined by XRD, and the presence of dense tetragonal ZrO₂ phase and crystalline Ag phases was confirmed. SEM-EDS analyses revealed a compact coating structure of approximately 1.8 µm thickness with homogeneously distributed Ag nanoparticles on the surface. As a result of the electrochemical corrosion tests, it was determined that the open circuit potential shifted to more noble values, the corrosion current density decreased, and the corrosion rate decreased by more than 70% on the surfaces where the Ag/ZrO₂ coating was applied. In the tribological tests, a decrease in the coefficient of friction, narrowing of wear marks, and significant reduction in surface damage were observed in dry and physiological (HBSS) environments. The findings revealed that the Ag/ZrO₂ hybrid coating significantly improved the surface performance of the Ti45Nb alloy both mechanically and electrochemically and offers high potential for biomedical implant applications. Full article

This study investigates the development of silver (Ag)-doped zirconia (ZrO₂) coatings deposited on 316LVM stainless steel via the unbalanced magnetron sputtering technique. The oxygen content in the Ar/O₂ gas mixture was systematically varied (12.5%, 25%, 37.5%, and 50%) to assess its influence on the resulting coating properties. In response to the growing demand for biomedical implants with improved durability and biocompatibility, the objective was to develop coatings that enhance both wear and corrosion resistance in physiological environments. The effects of silver incorporation and oxygen concentration on the structural, tribological, and electrochemical behavior of the coatings were systematically analyzed. X-ray diffraction (XRD) was employed to identify crystalline phases, while atomic force microscopy (AFM) was used to characterize surface topography prior to wear testing. Wear resistance was evaluated using a ball-on-plane tribometer under simulated prosthetic motion, applying a 5 N load with a bone pin as the counter body. Corrosion resistance was assessed through electrochemical impedance spectroscopy (EIS) in a physiological solution. Additionally, tribocorrosive performance was investigated by coupling tribological and electrochemical tests in Ringer’s lactate solution, simulating dynamic in vivo contact conditions. The results demonstrate that Ag doping, combined with increased oxygen content in the sputtering atmosphere, significantly improves both wear and corrosion resistance. Notably, the ZrO₂-Ag coating deposited with 50% O₂ exhibited the lowest wear volume (0.086 mm³) and a minimum coefficient of friction (0.0043) under a 5 N load. This same coating also displayed superior electrochemical performance, with the highest charge transfer resistance (38.83 kΩ·cm²) and the lowest corrosion current density (3.32 × 10⁻⁸ A/cm²). These findings confirm the high structural integrity and outstanding tribocorrosive behavior of the coating, highlighting its potential for application in biomedical implant technology. Full article

Background and Objectives: Magnesium (Mg)-based materials, such as the WE43 alloy, show potential in biomedical applications owing to their advantageous mechanical properties and biodegradability; however, their quick corrosion rate and hydrogen release restrict their general clinical utilization. This study aimed to develop a novel Mg-Zn-Ca alloy system based on WE43 alloy, evaluating the influence of Zn and Ca additions on microstructure, mechanical properties, cytocompatibility, and electrochemical behavior for potential use in biodegradable orthopedic applications. Materials and Methods: The WE43-Zn-Ca alloy system was developed by alloying standard WE43 (Mg–Y–Zr–RE) with 1.5% Zn and Ca concentrations of 0.2% (WE43_0.2Ca alloy) and 0.3% (WE43_0.3Ca alloy). Microstructural analysis was performed utilizing scanning electron microscopy (SEM) in conjunction with energy-dispersive X-ray spectroscopy (EDS), while the chemical composition was validated through optical emission spectroscopy and X-ray diffraction (XRD). Mechanical properties were assessed through tribological tests. Electrochemical corrosion behavior was evaluated using potentiodynamic polarization in a 3.5% NaCl solution. Cytocompatibility was assessed in vitro on MG63 cells using cell viability assays (MTT). Results: Alloys WE43_0.2Ca and WE43_0.3Ca exhibited refined, homogeneous microstructures with grain sizes between 70 and 100 µm, without significant structural defects. Mechanical testing indicated reduced stiffness and an elastic modulus similar to human bone (19.2–20.3 GPa), lowering the risk of stress shielding. Cytocompatibility tests confirmed non-cytotoxic behavior for alloys WE43_0.2Ca and WE43_0.3Ca, with increased cell viability and unaffected cellular morphology. Conclusions: The study validates the potential of Mg-Zn-Ca alloys (especially WE43_0.3Ca) as biodegradable biomaterials for orthopedic implants due to their favorable combination of mechanical properties, corrosion resistance, and cytocompatibility. The optimization of these alloys contributed to obtaining an improved microstructure with a reduced degradation rate and a non-cytotoxic in vitro outcome, which supports efficient bone tissue regeneration and its integration into the body for complex biomedical applications. Full article

The friction surfacing (FS) process has emerged over the past few years as a method for joining both similar and dissimilar materials, for volume damage repair of defective components, and for corrosion protection. The possibility to produce a metallic coating by FS, without melting the material, classifies this technique as distinct from other standard methods. This unconventional deposition method is based on the severe plastic deformation that appears on a rotating metallic rod (consumable material) pressed against the substrate under an axial load. The present study aims to investigate the tribological properties and corrosion resistance provided by the aluminum-based FS coatings deposited onto a structural S235 steel substrate and further modified by plasma electrolytic oxidation (PEO). During the PEO treatment, the formation of a ceramic film is enabled, while the hardness, chemical stability, corrosion, and wear resistance of the modified surfaces are considerably increased. The morpho-structural characteristics and chemical composition of the PEO-modified FS coatings are further investigated using scanning electron microscopy combined with energy dispersive spectroscopy analysis and X-ray diffraction. Dry sliding wear testing of the PEO-modified aluminum-based coatings was carried out using a ball-on-disc configuration, while the corrosion resistance was electrochemically evaluated in a 3.5 wt.% NaCl solution. The corrosion rates of the aluminum-based coatings decreased significantly when the PEO treatment was applied, while the wear rate was substantially reduced compared to the untreated aluminum-based coating and steel substrate, respectively. Full article

In response to the performance requirements of ship conductive rings in the coupled environment of high salt spray, high humidity, and mechanical wear in the ocean, a Cu-TiC composite coating was prepared on the surface of 7075 aluminum alloy by using the high-speed laser cladding (HLC) technology. The influence laws of the scanning speed (86.4–149.7 mm/s) on the microstructure, tribological properties, and corrosion resistance of the coating were explored. The results show that the scanning speed significantly changes the phase composition and grain morphology of the coating by regulating the thermodynamic behavior of the molten pool. At a low scanning speed (86.4 mm/s), the CuAl₂ phase is dominant, and the grains are mainly columnar crystals. As the scanning speed increases to 149.7 mm/s, the accelerated cooling rate promotes an increase in the proportion of Cu₂Al₃ phase, refines the grains to a coexisting structure of equiaxed crystals and cellular crystals, and improves the uniformity of TiC particle distribution. Tribological property analysis shows that the high scanning speed (149.7 mm/s) coating has a 17.9% lower wear rate than the substrate due to grain refinement and TiC interface strengthening. The wear mechanism is mainly abrasive wear and adhesive wear, accompanied by slight oxidative wear. Electrochemical tests show that the corrosion current density of the high-speed cladding coating is as low as 7.36 × 10⁻⁷ A·cm⁻², and the polarization resistance reaches 23,813 Ω·cm². The improvement in corrosion resistance is attributed to the formation of a dense passivation film and the blocking of the Cl diffusion path. The coating with a scanning speed of 149.7 mm/s exhibits optimal wear-resistant and corrosion-resistant synergistic performance and is suitable for the surface strengthening of conductive rings in extreme marine environments. This research provides theoretical support for the process performance regulation and engineering application of copper-based composite coatings. Full article

Electrodeposited composite coatings are widely studied for their potential to improve surface properties such as wear resistance and friction reduction. This study investigates the effect of electrodeposition parameters on the structure, morphology, and tribological performance of three coatings: pure nickel (Ni), Ni–graphite (Ni-G), and Ni–MoS₂ (Ni-MoS₂). Three deposition conditions were selected based on a review of key electrochemical parameters commonly used in the literature. The coatings were analyzed in terms of morphological characteristics, friction and wear resistance. The findings reveal that higher current densities led to increased friction and wear in Ni coatings, while lower pH values promoted finer crystallite sizes and improved tribological behavior. Ni-G coatings exhibited larger cluster formations with reduced friction and wear, especially at low pH, whereas Ni-MoS₂ coatings developed a stable cauliflower-like morphology at pH 2, but showed reduced adhesion and structural integrity at higher pH levels. Scratch resistance tests performed under optimal deposition conditions showed that Ni-G coatings provided the highest resistance to mechanical damage, while Ni-MoS₂ coatings were more susceptible to microcracking and adhesion failure. These results underscore the importance of optimizing deposition parameters to tailor the microstructure and functional properties of composite coatings for enhanced tribological and mechanical performance. Full article

The collector ring/carbon brush assembly of a hydrogenerator set is a critical component for transmitting excitation current into the self-exciting winding. Its operating environment necessitates excellent corrosion resistance and current-carrying frictional properties. The surface condition and material composition of the collector ring are key factors influencing the performance of the brush/ring interface. Coatings have proven effective in enhancing both tribological and corrosion-resistant characteristics. In this study, copper/graphene composite coatings were fabricated via electroplating, and the effects of graphene deposition rate on current-carrying friction characteristics were systematically investigated to optimize electroplating parameters. The results showed that the composite coating reduced contact resistance by 32.58% and friction coefficient by 37.59%. Electrochemical and immersion tests were conducted to evaluate the corrosion behavior under varying pressure and current density conditions. The results revealed that the optimal corrosion resistance was achieved under 1 N pressure and 12 A/cm² current density. The copper/graphene composite coating demonstrated superior corrosion resistance compared to uncoated samples. In summary, the electroplated copper/graphene composite coatings exhibit excellent current-carrying frictional performance and corrosion resistance, offering a promising solution for enhancing the durability and efficiency of hydrogenerator collector rings. Full article

The electrochemical co-deposition of various hard particles with metals or metal alloys has been recently studied, especially for developing wear-resistant coatings. In the current work, pure cobalt and cobalt–diamond composite coatings were electrochemically deposited onto a low-alloy steel substrate and further investigated in terms of microstructure, corrosion behavior, and tribological characteristics. The electrodeposition process was carried out using direct current, from an additive-free electrolyte containing 300 g L⁻¹ CoSO₄, 50 g L⁻¹ CoCl_2, and 30 g L⁻¹ H₃BO₃ with and without diamond particles. Scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS) was used for the microstructural characterization correlated with the chemical composition identification of the resulting coatings. The pure Co coatings showed a dense microstructure with a nodular morphology. In contrast, for the Co-diamond composite coatings, more elongated grains were observed containing a uniform distribution of the reinforcing diamond particles. The corrosion resistance was evaluated by potentiostatic polarization measurements in 3.5 wt.% NaCl solution, while the sliding wear resistance was assessed using the ball-on-disk testing method. The experimental results demonstrated that incorporating diamond particles into the cobalt deposition electrolyte positively impacted the tribological performance of the resulting composite coatings without significantly affecting the corrosion properties. Both cobalt and the composite coatings demonstrated substantially superior wear characteristics and corrosion resistance compared to the steel substrate. Full article

This research study aims to evaluate the wear and corrosive behaviour of aluminum 6061 alloy hybrid metal matrix composites after reinforcing them with graphene (0.5, 1 wt.%) and boron carbide (6 wt.%) at varying weight percentages. The hybrid composites were processed through ball milling and powder compaction, followed by a microwave sintering process, and T6 temper heat treatment was carried out to improve the properties. The properties were evaluated and analyzed using FE-SEM, Pin-on-Disc tribometer, surface roughness, salt spray test, and electrochemical tests. The results were evaluated prior to and subsequent to the T6 heat-treatment conditions. The T6 tempered sample S1 (Al6061-0.5% Gr-6% B₄C) exhibits a wear rate of 0.00107 mm³/Nm at 10 N and 0.00127 mm³/Nm at 20 N for 0.5 m/s sliding velocity. When the sliding velocity is 1 m/s, the wear rate is 0.00137 mm³/Nm at 10 N and 0.00187 mm³/Nm at 20 N load conditions. From the Tafel polarization results, the as-fabricated (F) condition demonstrates an Ecorr of −0.789 and an Icorr of 3.592 µA/cm² and a corrosion rate of 0.039 mm/year. Transitioning to the T6 condition further decreases Icorr to 2.514 µA/cm², Ecorr value of −0.814, and the corrosion rate to 0.027 mm/year. The results show that an increase in the addition of graphene wt.% from 0.5 to 1 to the Al 6061 alloy matrix deteriorated the wear and corrosive properties of the hybrid matrix composites. Full article

This study focused on analyzing the changes in the microstructure and composition evolution of plasma electrolytic oxidation (PEO) and electroless copper–PEO composite (Cu/PEO) coatings both prior to and following irradiation. Additionally, the corrosion resistance and tribological properties of these coatings were assessed. Post-irradiation, the PEO coating exhibited a 5% reduction in porosity, and electrochemical impedance spectroscopy (EIS) tests indicated a notable enhancement in short-term corrosion resistance, with a low-frequency impedance of 10⁶ Ω·cm² sustained over 72 h. The Cu/PEO coating, deposited with Bi element, demonstrated enhanced wear resistance after irradiation. Specifically, the coefficient of friction (COF) dropped from 0.7 to 0.5, and the wear rate reduced by 39%. Full article

Nowadays, Thin Dense Chromium (TDC) coatings are being industrially used in rolling bearings applications due to their claimed advantages such as high hardness, low wear, and good corrosion resistance. However, despite their broad commercial use, very little has been published in the open scientific literature regarding their microstructure, nanomechanical, and tribological properties. In this paper, TDC coatings with a thickness of about 5 µm were deposited by a customized electrochemical process on ASTM 52100 bearing steel substrates. Surface microstructure and chemical composition analysis of the TDC coatings was carried out by scanning electron microscopy and atomic force microscopy. The results revealed a coating with a dense, nodular, and polycrystalline microstructure. Unlike standard electrodeposited “Hard Chromium” coatings, TDC coatings show no presence of micro/nano-cracks, likely contributing to their superior corrosion resistance. The nanomechanical behavior, studied by nanoindentation as a function of penetration depths, exhibits a pronounced size effect near the coating surface that can be linked to the nodular microstructure. A hard surface with hardness H_IT 14.9 ± 0.5 GPa and reduced elastic modulus E_r = 216.8 ± 3.9 GPa was observed. Tribological characterization under the presence of lubricants was performed by two single-contact tribometers using coated and uncoated steel balls against flat steel substrates. An in-house fretting wear rig was used to measure the lubricated friction coefficient in pure sliding conditions, whilst the friction performance in rolling/sliding lubricated conditions was evaluated using a WAM test rig. In pure sliding, TDC/TDC contacts show ~13% lower friction than for steel. Under rolling/sliding conditions with 5% sliding, the traction coefficient of TDC/TDC coating contact was at least 20% lower than that for steel/steel contact. The tribological results obtained in various contact conditions demonstrate the benefits of applying TDC coatings to reduce bearing friction. Full article

This study investigates the effects of aluminum and nitrogen content on the microstructure, mechanical properties, and tribological performance of high-entropy coatings based on (TiCrAl_xNbY)N_y systems. Using a hybrid magnetron sputtering technique, both metallic and nitride coatings were synthesized and evaluated. Increasing the aluminum concentration led to a transition from a crystalline to a nanocrystalline and nearly amorphous (NC/A) structure, with the TiAl_0.5CrNbY sample (11.8% Al) exhibiting the best balance of hardness (6.8 GPa), elastic modulus (87.1 GPa), and coefficient of friction (0.64). The addition of nitrogen further enhanced these properties, transitioning the coatings to a denser fine-grained FCC structure. The HN2 sample (45.8% nitrogen) displayed the highest hardness (21.8 GPa) but increased brittleness, while the HN1 sample (32.9% nitrogen) provided an optimal balance of hardness (14.3 GPa), elastic modulus (127.5 GPa), coefficient of friction (0.60), and wear resistance (21.2 × 10⁻⁶ mm³/Nm). Electrochemical impedance spectroscopy revealed improved corrosion resistance for the HN1 sample due to its dense microstructure. Overall, the (TiAl_0.5CrNbY)N_0.5 coating achieved the best performance for friction applications, such as break and clutch systems, requiring high coefficients of friction, high wear resistance, and durability. Full article

Seamless gas cylinders for diving exhibit excellent low-temperature impact performance, lightweight characteristics, and good corrosion resistance, making them widely applicable in underwater activities. However, during use, the peeling of paint or corrosion on the surface of these cylinders poses a significant threat to their safety. In this study, environmentally friendly arc ion plating technology was used to deposit TiBN, CrAlN, and nano-multilayer coatings of CrAlN/TiBN. The surface morphology, tribological properties, and corrosion resistance of these coatings were investigated. The results indicated that both CrAlN and CrAlN/TiBN coatings possess fewer droplets, pinholes, and pits, and the cross-section of the CrAlN/TiBN coating exhibits a denser structure. The preferred orientation for TiBN was identified as TiB₂ (101), while that for CrAlN was Cr(Al)N (200), with the preferred orientation for CrAlN/TiBN being TiB₂ (101). The friction measurements revealed that the lowest coefficient was observed in the CrAlN/TiBN coating (0.489), followed by CrAlN (0.491) and then TiBN (0.642). Electrochemical tests conducted in artificial seawater demonstrated that the self-corrosion potential was highest for the CrAlN/TiBN coating, followed by CrAlN and lastly TiBN. The developed TiBN-based nano-multilayer coatings hold substantial application value in protecting seamless gas cylinders used in diving. Full article

GH4169 alloy, a nickel-based superalloy known for its excellent high temperature resistance, corrosion resistance, mechanical properties, and high-temperature tribological properties, is widely used in industrial applications, such as in gas turbines for space shuttles and rocket engines. This study addresses the issue of electrolyte product residue in the electrochemical machining process of a GH4169 alloy by utilizing a C₆H₅Na₃O₇-containing NaNO₃ new mixed electrolyte. Comparative investigations of the electrochemical behavior and electrolyte product removal mechanisms at different concentrations of C₆H₅Na₃O₇ additive in NaNO₃ solutions were conducted. The effects of additives, applied voltage, and the rotating speed of the cathode tool on the processing performance of micro-pit arrays on a GH4169 alloy were analyzed. The results indicate that the mixed solution containing C₆H₅Na₃O₇ significantly improves the localization and geometric morphology of the micro-pits compared to a single NaNO₃ solution. The optimal electrochemical machining parameters were identified as 0.5 wt% C₆H₅Na₃O₇ + 10 wt% NaNO₃ mixed electrolyte, 12 V applied voltage, and 0.1 r/min rotating speed of the cathode tool. Under these conditions, high-quality micro-pit arrays with an average diameter of 405.85 μm, an average depth of 87.5 μm, and an etch factor (EF) of 1.67 were successfully fabricated, exhibiting excellent morphology, localization, and consistency. Full article