Search Results (163)

This study investigated the effect of adding superhard ReB₂ to atmospheric plasma sprayed (APS) coatings based on 60 wt% Al₂O₃ and 40 wt% ZrO₂. The amorphous phases commonly present in such coatings are known to impair their performance. ReB₂ was introduced as a crystallization nucleus due to its high melting point. ReB₂ decomposes in the presence of moisture and oxygen into H₃BO₃, ReO₃, HBO₂, and HReO₄. ReB₂ was encapsulated with Al₂O₃ via metallothermic synthesis to improve moisture stability, yielding a powder with d₉₀ = 15.1 μm. After milling, it was added at 20 wt% to the Al₂O₃-ZrO₂ feedstock. Agglomeration parameters were optimized, and coatings were deposited under varying APS conditions onto 316L steel substrates with a NiAl bond coat. In the coating with the highest ReB₂ content, the identified phases included ReB₂ (2.6 wt%), Re (0.8 wt%), α-Al₂O₃ (30.9 wt%), η-Al₂O₃ (32.4 wt%), and monoclinic and tetragonal ZrO₂. The nanohardness of the coating, measured using a Vickers indenter at 96 mN and calculated via the Oliver–Pharr method, was 9.2 ± 1.0 GPa. High abrasion resistance was obtained for the coating with a higher content of η-Al₂O₃ (48.7 wt%). The coefficient of friction, determined using a ball-on-disc test with a corundum ball, was 0.798 ± 0.03. After 15 months, the formation of (H₃O)(ReO₄) was observed, suggesting initial moisture-induced changes. The results confirm that Al₂O₃-encapsulated ReB₂ can enhance phase stability and crystallinity in APS coatings. 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

This study discusses the frictional wear performance of three 3D-printed materials, acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), and high-impact polystyrene (HIPS), while evaluating different layer thickness levels. The materials were subjected to wear volume and rate tests by ball-on-disc wear tests at various thickness levels (0.1, 0.2, and 0.3 mm) and sliding distances. Lastly, SEM analysis was carried out to study the wear tracks and debris developed during the testing. Quantitatively, ABS maintained a mean wear volume below 0.15 mm³ across all test conditions (e.g., 0.05 ± 0.01 mm³ at 0.1 mm layer thickness and 150 m sliding distance), whereas PLA and HIPS recorded much higher averages of 1.5 mm³ and 3.0 mm³, respectively. With the increase in layer thickness, which caused an upward trend in the obtained results, the wear volume of the investigated materials also increased. ABS exhibited the smallest material loss of all three polymers; for example, at 0.1 mm layer thickness and a 150 m sliding distance, the mean wear volume was only 0.05 mm³, and even under the harshest condition tested (0.3 mm layer thickness, 300 m), the value remained below 0.15 mm³. PLA and HIPS showed higher wear volumes, while HIPS had the lowest resistance among the three materials. The multifunctional wear behavior difference contributed by material type was 59.76%, as shown through ANOVA, and that by layer thickness was 21.32%. Among the parameters investigated, material type had the largest control in wear behavior due to inherent variation in the structural characteristics of the material such as interlayer adhesion, toughness, and brittleness. For instance, the amorphous nature of ABS and its good layer adhesion provided significantly superior wear resistance compared to the brittle PLA and the poorly adhered HIPS. It is highlighted in this research that selecting appropriate material and layer thickness combinations can improve the durability of 3D-printed components. Full article

The paper shows the effect of using a lubricant in the form of an ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF₆), on the tribological properties of a hydrogenated diamond-like coating (DLC) doped with tungsten a-C:H:W. The coatings were deposited on 100Cr6 steel by plasma-enhanced chemical vapor deposition PECVD. Tribological tests were carried out on a TRB³ tribometer in a rotary motion in a ball–disc combination. 100Cr6 steel balls were used as a counter-sample. Friction and wear tests were carried out for discs made of 100Cr6 steel and 100Cr6 steel discs with a DLC coating. They were performed under friction conditions with and without lubrication under 10 N and 15 N loads. The ionic liquid BMIM-PF₆ was used as a lubricant. Coating thickness was observed on a scanning microscope, and the linear analysis of chemical composition on the cross-section was analyzed using the EDS analyzer. The confocal microscope with an interferometric mode was used for analysis of the geometric structure of the surface before and after the tribological tests. The contact angle of the samples for distilled water, diiodomethane and ionic liquid was tested on an optical tensiometer. The test results showed good cooperation of the DLC coating with the lubricant. It lowered the coefficient of friction in comparison to steel about 20%. This indicates the synergistic nature of the interaction: DLC coating–BMIM-PF₆ lubricant–100Cr6 steel. Full article

This article presents the results of tests on the functional properties of oxide layers (Fe₂O₃, Cr_1.3Fe_0.7O₃) produced on AISI 316L austenitic steel, which is susceptible to friction wear, using a new, simple, inexpensive, and environmentally friendly process conducted in air at three different temperatures (400 °C, 450 °C and 500 °C). Vickers microhardness tests showed that the process slightly increased hardness only at lower indenter loads, indicating a low thickness of the layers. The greatest increase in hardness was observed in the sample oxidized at the lowest temperature. Tests performed using an optical profilometer showed a tendency for surface roughness to increase with oxidation temperature. Low surface roughness, enhanced microhardness and a low coefficient of friction resulted in the steel oxidized at 400 °C exhibiting the lowest wear rate in the “ball-on-disc” test. The contact angle measurements for all tested samples indicated hydrophilic properties. Potentiodynamic tests showed a deterioration in the corrosion resistance of the steel after oxidation at 450 °C and 500 °C. Oxidation at 400 °C did not cause a significant decrease in pitting corrosion resistance, while an increase in polarization resistance and a decrease in corrosion current density were observed. An interesting phenomenon, requiring further research, is the greatest increase in hardness and wear resistance observed in the layer formed at 400 °C. Full article

Perfluorinated tetradecanoic acid was added as an additive to a base oil and tested under full film elastohydrodynamic (EHD) contact conditions between a steel ball and a steel disc. By varying key performance parameters, we aimed to assess the feasibility and limitations of perfluorinated carboxylic acids in reducing friction in lubricated contacts. The results demonstrate that the tested perfluorinated additive is effective in reducing friction when blended with a non-polar synthetic poly-alpha-olefin oil. However, no significant friction reduction was observed when the same additive was used in a slightly polar synthetic ester. The carboxylic acid functional group plays a crucial role in the observed friction-reducing effect. Adjusting the additive concentration further plays an important role in reducing friction. A concentration of at least 0.35 wt.% is required to achieve a notable friction reduction of approximately 10%. Increasing the concentration beyond this threshold continues to improve the friction-reducing effect. Conversely, increasing the contact pressure has a detrimental impact on friction reduction. The greatest reduction in friction—over 20% compared to the base oil—was achieved at the lowest contact pressure tested (0.69 GPa). Full article

PVD hard coatings improve the wear and frictional properties in metal cutting and, therefore, extend the lives of cutting tools. Cutting fluids, including the novel use of liquid carbon dioxide (LCO₂), are crucial for reducing tool wear and enhancing machining efficiency. This experimental research is focused on ball-on-disc wear tests of TiAlN hard coatings in environmental, N₂ and CO₂ atmospheres. In the latter case, the experiments were also performed by adding LCO₂ directly into the contact zone. In order to achieve the same temperatures as real cutting conditions, tests were performed at 250 °C, 500 °C and 700 °C, in addition to room temperature. Results show that the TiAlN coating had the highest wear rate in room-temperature tests, regardless of the atmosphere. The wear significantly dropped with the test temperature. It was the lower in the CO₂ atmosphere at all temperatures than in all gas-only atmospheres. When LCO₂ was introduced to the contact, the wear was at its highest at 500 °C, which is the opposite of all other gas-only atmospheres, where it was at its lowest. In all tribological LCO₂ tests, we noticed increased friction coefficient fluctuations. In all gas-only atmospheres, adhered material was observed on the wear tracks, but in LCO₂, wear debris was not detected either on the disk or on the ball. Full article

The present study explores the effects of pre-coating on the wear performance of milled carbon fiber-filled basalt composites via laser texturing. Laser texturing was used to change surface topography, enhancing adhesion and wear resistance. Incorporated 0 wt.% and 5 wt.% milled carbon fibers in an epoxy matrix. A fiber laser system was employed for surface treatment, in which power, scanning speed, and pulse frequency were optimized. For pre-coating, an epoxy-based primer was used, and the adhesion and wear performance of the coating was studied using ball-on-disc wear tests. Experimental results demonstrate that laser texturing significantly increases coating adhesion by enhancing the surface roughness and mechanical interlocking. The laser-induced textures displayed mostly square-shaped dimples, reducing practically by around 22% the deformation of the primer coating when used in combination with 5 wt.% carbon fiber milling. The textured surfaces reduced friction noticeably, leading to a decrease of as much as 23% in the coefficient of friction from untreated surfaces. SEM and 3D profilometry analysis indicate that the lower delamination observed in the laser treatment led to optimal coating retention. The original contribution of this work consists of the unique integration of laser surface engineering with pre-coating treatments toward improved tribological performance. 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 work aims to introduce a new method to predict the wear rate accurately and quickly. Using techniques such as laser scanning confocal microscopy can take a long time to estimate the wear of the experimental alloys in situ. Developing a new method based on calculating the area under the early stages of the friction curve can be a useful and quick tool for estimating wear rate values and comparing wear between different alloys and conditions. The results validated the application of this new method with a regression coefficient of 0.98. This work also demonstrates that wear in the early stages accounts for the highest wear, indicating that the friction coefficient in the steady-state is not always a reliable indicator of the total wear rate. Hardness can be a more influencing parameter on wear rate than steady-state friction coefficient. Using the new method can help reduce time and predict wear more accurately of different alloys. Full article

This study examines the impact of various abrasive balls and sliding loads on WC-12Co coatings. For this purpose, 4 N, 8 N, and 12 N loads were applied to the WC-12Co composite coatings with Al₂O₃ and Si₃N₄ balls. WC-12 Co composite was deposited by the high-velocity oxygen fuel method on the AISI 304 substrate. The wear tests were conducted in accordance with ASTM G99 on a ball-on-disc tribometer at room temperature. In order to study the results of the coating tests, wear volume loss was measured against each counter body. Surface roughness and microstructure changes before and after wear were examined by electron microscopy. The resulting wear tracks were examined with an optical profilometer and the wear amount was calculated. When comparing the Al₂O₃ ball with the Si₃N₄ ball, the Al₂O₃ ball corrodes WC-12Co coatings more and is most susceptible to abrasive grooving, brittle cracking, and spalling. Wear rates rose by 77%, 58%, and 67% when the Si₃N₄ abrasive sample and the samples with Al₂O₃ coating were subjected to 4 N, 8 N, and 12 N loads, respectively. WC-12Co coating layers and powders were subjected to X-ray diffraction analyses, which revealed that coarse WC-12Co powder underwent less decarburization due to HVOF spraying. Full article

This article compares the rheological and tribological properties of three ionic liquids: Tributyl(methyl)phosphonium dimethyl phosphate 97%—MFCD, 1-Butyl-3-methylimidazolium hexafluorophosphate 97%—BMIMPF6, and 1-Butyl-3-methylimidazolium tetrafluoroborate 98%—BMIMBF4. Their density and kinematic viscosity at 20 °C and 40 °C were investigated, and tribological tests were carried out at the same temperatures with ball-on-disc contact. The test materials were made of 100Cr6 steel. A scanning electron microscope was used to image the wear tracks, while an EDS analyzer was employed to determine the chemical composition at the points of wear on the samples. A confocal microscope was used to analyze the geometric structure of the samples before and after the tribological tests. The results of the tests indicated that an increase in temperature reduced the dynamic viscosity of all the ionic liquids tested. At the same time, an increase in the MFCD and BMIMBF4 ionic liquid density and a decrease in the density of the BMIMPF6 ionic liquid were observed. The BMIMPF6 ionic liquid used for this study provided the lowest value of linear wear at both temperatures, ambient and 40 °C. However, for the BMIMBF4 ionic liquid, significant wear was observed for the tested discs and balls, with corrosive pitting on their surfaces. Full article

The influence of ball burnishing on friction and wear at elevated temperatures under fretting conditions has not yet been reported. Fretting experiments were conducted using the Optimol SRV5 tester (Optimol Instruments, Munich, Germany) under dry gross fretting conditions. A ball of WC ceramic was pressed against a disc from the titanium alloy Ti6Al4V. Experiments were carried out at elevated temperatures of 100, 200, and 300 °C. The displacement frequency was 50 Hz, the stroke was 0.1 mm, and the test duration was 15 min. The normal loads used were 40, 60, and 80 N. Ball burnishing led to a substantial reduction in the roughness height and an increase in the microhardness of samples from the titanium alloy. Burnishing, in most cases, caused an improvement in the friction resistance of sliding assemblies. Ball burnishing also led to wear reduction compared to the turned disc sample. The best tribological performance of the sliding pair was achieved for the disc sample burnished with the highest pressure of 40 MPa. An increase in temperature from 100 to 200 °C caused small changes in disc wear volumes and coefficients of friction. A further increase in temperature to 300 °C led to an increase in disc wear rates and friction coefficients. Full article

The plasma immersion nitriding system was utilized to make massive nitrogen supersaturation (MNS) to CoCrMo disc and die substrates at 723 K for 21.6 ks. The top layer thickness in the multi-layered MNSed layer was 20 μm. Its nitrogen solute content reached 5 mass% on average after SEM-EDX analysis. The surface hardness was 1300 HV_1N (HV_0.1), which was much higher than the bare CoCrMo with 450 HV_1N. The original polycrystalline structure was modified to be a multi-layered microstructure, which consisted of the nanograined MNSed top layer, the buffer layer with a thickness of 5 μm, and the column–granular structured layer with their textured crystallographic orientations. The BOD (ball-on-disc) testing was employed to describe the frictional sliding behavior under the applied loads of 5 N and 10 N and the sliding velocity of 0.1 m/s against the AISI316 ball. The friction coefficient was held constant by 0.68 on average. The CNC (Computer Numerical Control) stamping system was employed to upset the fine-grained 1.0 mm thick AISI316 wire up to 70% in reduction in thickness. The friction coefficient at RT was estimated to be 0.05. A round, fine-grained AISI316 wire was shaped into a thin plate with a thickness of 0.3 mm in cold and dry. Full article

This article aims to introduce the tribological investigation of nanoscale zinc oxide particles as friction and wear reduction additives in the automotive industry and to present the results of the measurements. The surface-activated nanoparticles were homogenized into a neat Group-III-type base oil at five different concentrations, and their tribological properties were tested using a simplified ball-on-disc tribosystem. The arising wear scar images were investigated, and the occurred wear volume values were also calculated using a confocal microscope. The evaluation presented excellent friction and wear reduction properties, especially at higher concentrations (0.4 and 0.5 wt%). The authors would like to highlight the tribological decreasing potentials provided by such nanoparticles. Nanoparticle-reinforced lubricants can be one of the future solutions to developing operating machines with an achievable maximum energy efficiency. Full article