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Reactive Pulsed Laser Deposition of Clustered-Type MoSx (x ~ 2, 3, and 4) Films and Their Solid Lubricant Properties at Low Temperature
摘要： We studied the tribological properties of amorphous molybdenum sulfide (MoSx) thin-film coatings during sliding friction in an oxidizing environment at a low temperature (?100 °C). To obtain films with different sulfur contents (x ~ 2, 3, and 4), we used reactive pulsed laser deposition, where laser ablation of the Mo target was performed in H2S at various pressures. The lowest coefficient of friction (0.08) was observed during tribo-testing of the MoS3 coating. This coating had good ductility and low wear; the wear of a steel counterbody was minimal. The MoS2 coating had the best wear resistance, due to the tribo-film adhering well to the coating in the wear track. Tribo-modification of the MoS2 coating, however, caused a higher coefficient of friction (0.16) and the most intensive wear of the counterbody. The MoS4 coating had inferior tribological properties. This study explored the mechanisms of possible tribo-chemical changes and structural rearrangements in MoSx coatings upon contact with a counterbody when exposed to oxygen and water. The properties of the tribo-film and the efficiency of its transfer onto the coating and/or the counterbody largely depended on local atomic packing of the nanoclusters that formed the structure of the amorphous MoSx films.
关键词： wear,molybdenum sulfides,solid lubricants,nanoclusters,reactive pulsed laser deposition,low temperature,coefficient of friction
更新于2025-09-23 15:19:57
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Corrosion wear and electrochemical corrosion behaviors of laser cladded amorphous FeSiB coating in 3.5% NaCl solution
摘要： An amorphous FeSiB composite coating was fabricated on S355 structural steel using a laser cladding. The corrosion wear and electrochemical corrosion behaviors of FeSiB coating in 3.5% NaCl solution were investigated using a wear tester and electrochemical workstation. The results show that the FeSiB coating with the hardness of 601 HV is primarily composed of amorphous and crystal phases of α–Fe(Si) and Fe2B. The average coefficients of friction (COFs) of FeSiB coating at the wear loads of 3, 5 and 7 N loads are 0.888, 0.751, and 0.564, respectively, which deceases with the increase of wear loads; and the corresponding wear rates are 7.60, 8.02 and 10.04 μm3?N–1?m–1, respectively. The corrosion potentials of FeSiB coating and substrate are –0.718 and –1.042 V, respectively, exhibiting that the corrosion potential of FeSiB coating shifts positively, its corrosion resistance was higher than that of substrate.
关键词： electrochemical corrosion,amorphous FeSiB composite coating,coefficient of friction (COF),wear mechanism,laser cladding (LC)
更新于2025-09-23 15:19:57
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Effects of LED Light Color and Intensity on Feather Pecking and Fear Responses of Layer Breeders in Natural Mating Colony Cages
摘要： The friction properties play an important role in diamond polishing, which significantly affect the interfacial contact and material removal. In this paper, the friction force and coefficient of friction (COF) during diamond polishing process were monitored under different loads and rotating speeds. The results show that the friction force and COF both increase with the load, and decrease with the rotating speed. The bearing capacity of liquid film is enhanced at large rotating speed, which leads to the decrease of friction force. According to the binomial law of friction, the increase of actual contact area caused by high load contributes to the increase of COF. Besides, it is found that the addition of H2O2 reduces the friction coefficient through surface adsorption. In order to further reveal the mechanism of friction variation at the atomic level, the friction behavior at a local area of interface between the diamond substrate and the abrasive particle in diamond polishing process was investigated by molecular dynamics (MD) method. The simulation results indicate that the interfacial bridge bonds formed between the substrate and particle under the action of load lead to the increase of friction force.
关键词： molecular dynamics,coefficient of friction,diamond,friction,polishing
更新于2025-09-19 17:13:59
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Development of mathematical models and optimization of the process parameters of laser surface hardened EN25 steel using elitist non-dominated sorting genetic algorithm
摘要： The ultimate goal of all production entities is to select the process parameters that would be of maximum strength, minimum wear and friction. The friction and wear are serious problems in most of the industries which are influenced by the working set of parameters, oxidation characteristics and mechanism involved in formation of wear. The experimental input parameters such as sliding distance, applied load, and temperature are utilized in finding out the optimized solution for achieving the desired output responses such as coefficient of friction, wear rate, and volume loss. The optimization is performed with the help of a novel method, Elitist Non-dominated Sorting Genetic Algorithm (NSGA-II) based on an evolutionary algorithm. The regression equations obtained using Response Surface Methodology (RSM) are used in determining the optimum process parameters. Further, the results achieved through desirability approach in RSM are compared with that of the optimized solution obtained through NSGA-II. The results conclude that proposed evolutionary technique is much effective and faster than the desirability approach.
关键词： Laser surface hardening,wear rate,coefficient of friction,optimization,NSGA-II
更新于2025-09-12 10:27:22
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Tribological performance of metal-reinforced ceramic composites selectively structured with femtosecond laser-induced periodic surface structures
摘要： The impact of femtosecond (fs) laser-induced periodic surface structures (LIPSS) on tribological properties was investigated for metal-reinforced ceramic composites (Al2O3-ZrO2-Nb). For this purpose, the metallic niobium (Nb) phase was selectively structured with LIPSS in an air environment with different values of the fs-laser peak fluence by near-infrared fs-laser radiation (λ = 1,025 nm, τ = 300 fs, frep = 1 kHz), taking advantage of the different light absorption behavior of ceramic and metal. The tribological performance was evaluated by reciprocating sliding tests in a ball-on-disc configuration using Ringer’s solution as lubricant. The surfaces were characterized before and after laser irradiation by optical microscopy, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy, energy dispersive X-ray spectroscopy and by measuring the contact angle with Ringer’s solution. The LIPSS formation resulted in an increased wetting of the surface with the lubricant. Moreover, the selectively structured composite surfaces revealed a coefficient of friction significantly reduced by a factor of ~ 3 when compared to the non-irradiated surface. Furthermore, the formation of a laser-induced oxidation layer was detected with NbO as the most prominent oxidation state. Selectively structured composites with outstanding mechanical properties and enhanced tribological performance are of particular interest for biomedical applications.
关键词： femtosecond laser-induced periodic surface structures (LIPSS),tribology,wettability,ceramic matrix composites,coefficient of friction,selective surface structuring
更新于2025-09-12 10:27:22
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Novel laser textured surface designs for improved zirconia implants performance
摘要： The development of new surface designs to enhance the integration process between surgically placed implants and biological tissues remains a challenge for the scientific community. In this way and trying to overcome this issue, in this work, laser technology was explored to produce novel textures on the surface of green zirconia compacts produced by cold pressing technique. Two strategies regarding line design (8 and 16 lines design) and different laser parameters (laser power and number of laser passages) were explored to assess their influence on geometry and depth of created textures. The produced textures were evaluated with Scanning Electron Microscopy (SEM) and it was observed that well-defined textured surfaces with regular geometric features (cavities or pillars) were obtained by laser combining different strategies lines design and parameters. The potential of proposed textures was also evaluated regarding surface wettability, friction performance (static and dynamic coefficient of friction evolution) against bone, aging resistance and flexural strength. Results demonstrated that all the produced textures display a super hydrophilic or hydrophilic behavior. Regarding the friction behavior, it was experimentally observed a high initial static coefficient of friction (COF) for all produced textures. Concerning the aging resistance, all the textured surfaces revealed a low monoclinic content, less than 25% after 5?h of hydrothermal aging. The flexural strength results showed that the mechanical resistance of zirconia was not significantly compromised with the laser action. Based on the obtained results, it is possible to prove that the processing route used for manufacturing the new and different surface designs (cold pressing technique followed by laser texturing) showed to be particularly effective for the production of zirconia implants with customized surface designs according to the properties required in a specific application. These new surface designs besides to enhance the surface wettability and also to improve the fixation at the initial moment of the implantation, do not significantly compromise the resistance to aging and the mechanical performance of zirconia. Hence, a positive impact on the long-term performance of the zirconia implants may be expected with the proposed novel laser textured surface designs.
关键词： Flexural strength,Aging resistance,Zirconia,Surface wettability,Coefficient of friction,Laser surface texturing
更新于2025-09-12 10:27:22
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Mechanical and tribological performance of fiber laser cladded h-BN + SS316 composite on SS316 surface
摘要： Laser cladding is a unique process for adding one material to the surface of another base material by utilizing high energy and coherent laser beam. For the present investigation, h-BN (hexagonal boron nitride) + SS316 composite coating was applied on SS316 substrate surface by fiber laser cladding operations. Under the influence of various input process parameters, the surface morphology, microstructure, X-ray diffraction, clad layer thickness, micro-hardness, and tribological behaviour of the composite coating were examined. The result showed good metallurgical bonding between the clad powder and substrate surface. Surface morphology did not show any pores and cracks on the clad surface. From FESEM analysis, the clad surface was found to be smooth and free from any crack propagation during laser processing. X-ray diffraction analysis showed formation of Fe3N, Cr2N, CrB, B2C5N2, γ- (Ni, Fe), h-BN phases which are responsible for enhancing mechanical and tribological properties of the clad layer. During the study, the micro-hardness of the clad layer was found to increase with an increase in % v/v of h-BN by 2-2.5 times compared (525 HV0.3) to parent material (220 HV0.3). Further, dry sliding wear test was carried out with Pin-On-Disc, showed that the coefficient of friction value decreased significantly from 0.560 (parent surface) to 0.251 (clad surface).
关键词： solid lubricant,micro-hardness,fiber laser cladding,coefficient of friction,h-BN,microstructure
更新于2025-09-11 14:15:04