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Laser texturing with a dimple pattern was applied to modify a Ti6Al4V alloy at the micro level, aiming to improve its friction and wear resistance in combination with oil lubrication to optimize the performance in demanding industrial environments. The tribological analysis was performed on four different dimple-textured surfaces with varying dimple size and dimple-to-dimple distance and under lubrication with three different oils, i.e., T9, VG46, and VG100, to reflect the oil viscosity's influence on the friction/wear of the laser-textured Ti6Al4V alloy. The results show that the surfaces with the highest texture density showed the most significant COF reduction of around 10% in a low-viscosity oil (T9). However, in high-viscosity oils (VG46 and VG100), the influence of the laser texturing on the COF was less pronounced. A wear analysis revealed that the laser texturing intensified the abrasive wear, especially on surfaces with a higher texture density. For low-texturing-density surfaces, less wear was observed for low- and medium-viscosity oils (T9 and VG46). For medium-to-high-texturing densities, the high-viscosity oil (VG100) provided the best contact conditions and wear results. Overall, reduced wear, even below the non-texturing case, was observed for sample 50-200 in VG100 lubrication, indicating the combined effect of oil reservoirs and increased oil-film thickness within the dimples due to the high viscosity.
RESUMEN
In the present work, the functionalisation of austenitic stainless steel, AISI 316L surfaces via nanosecond Nd:YAG laser texturing in order to modify the surface morphology with crosshatch and dimple patterns is presented. A tribological analysis under lubrication with sunflower and jojoba oil with and without the addition of a solid lubricant, MoS2 nanotubes, was performed. In conjunction with friction/wear response laser-textured surface wettability, oil spreadability and oil retention capacity were also analysed. It was shown that the crosshatch pattern generally exhibited lower friction than the dimple pattern, with the addition of MoS2 nanotubes not having any significant effect on the coefficient of friction under the investigated contact conditions. This was found in addition to the better oil spreadability and oil retention capacity results of the crosshatch-textured surface. Furthermore, texturing reduced the wear of the stainless-steel surfaces but led to an approximately one order of magnitude larger wear rate of the steel counter-body, primarily due to the presence of hard bulges around the textured patterns. Overall, the crosshatch pattern showed better oil retention capacity and lower friction in combination with different vegetable oils, thus making it a promising choice for improving tribological performance in various environmentally friendly applications.
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The scope of the Special Issue entitled "Mechanical, Corrosion Resistance, and Antibacterial Properties of Metallic Materials" includes research regarding the latest developments in materials' mechanical properties and characterization, pure/applied corrosion phenomena, and advanced understanding of bacterial adhesion and the induced antibacterial properties of metallic materials [...].
RESUMEN
A Nd-YAG laser was used for texturing the Ti6Al4V surface with dimples of diameter 50 and 100 µm and centre-to-centre distance 100, 200 and 400 µm, defining the surface texture density. The tribological evaluation was conducted to analyse and compare the behaviour of un-textured and laser-textured samples under water in comparison to oil (PAO6) lubrication without and with the addition of MoS2 nanotubes into the lubricant. MoS2 nanotubes had a positive effect on friction in both media for laser-textured Ti6Al4V. Evaluation of friction and wear in water and PAO6 showed a comparable tribological response in water to oil for specific laser-textured configurations, proving the novel concept of green tribology for laser texturing in combination with MoS2 nanotubes/water lubrication.
RESUMEN
In our study, plasma surface modification was employed to tailor the surface properties of magnesium in terms of surface chemistry, topography, and wettability. For two sets of samples, the plasma treatment involved two steps using two different gases (hydrogen and oxygen), while one set of samples was treated with one step only using oxygen. X-ray photoelectron spectroscopy (XPS) was applied to determine the surface composition, oxidation state of the elements, and the thickness of the surface oxide layer on the Mg samples after different plasma treatments. The surface morphology was characterised using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The wettability was analysed by measuring the static water-contact angles and the corrosion was evaluated using potentiodynamic measurements. The interaction of the live cells with the differently modified Mg surfaces was evaluated in terms of biocompatibility using MG-63 cells (human bone osteosarcoma cells). We have shown that a plasma surface treatment significantly decreased the carbon content and the formation of a 15-20-nm-thick MgO layer was observed. This improves the corrosion resistance, while the biocompatibility was retained, compared to the untreated Mg. A plasma surface treatment is therefore an important step in the development of novel surfaces with improved corrosion resistance for magnesium in biomedical applications.
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The total cost and environmental consequences of corrosion problems have become a major challenge to engineers [...].
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An AISI 316L surface was functionalized by the adsorption of hydrophilic epoxy and epoxy/TiO2/epoxy coatings and hydrophobic epoxy/fluoroalkylsilanefunctionalized FASTiO2/epoxy coatings. We characterized the coatings' wettability, morphology and average surface roughness and discussed the influence of surface wettability and morphology on the coefficient of friction and the wear resistance. Experiments were performed in dry, distilled water and in a simulated physiological solution (Hank's solution). In the case of dry sliding, a lower coefficient of friction is achieved for both TiO2 coatings compared to the pure epoxy coating. In a water environment the same level of friction is shown for all three coatings, whereas in Hank's solution the friction is reduced for the hydrophilic epoxy/TiO2/epoxy coating, increased for the hydrophobic epoxy/FASTiO2/epoxy coating and has no effect on the pure epoxy coating. The results show that the corrosion resistance is significantly improved for the hydrophobic epoxy/FASTiO2/epoxy coating compared to the hydrophilic pure epoxy and epoxy/TiO2/epoxy coatings.
RESUMEN
Epoxy/TiO2/epoxy and epoxy/FAS-TiO2/epoxy coatings were applied to the surface of AISI 316L stainless steel with the aim to improve the biocompatibility and antibacterial properties. Contact-angle measurements were used to evaluate the wetting properties of the epoxy, epoxy/TiO2/epoxy and epoxy/FAS-TiO2/epoxy coatings. The epoxy and epoxy/TiO2/epoxy coatings were hydrophilic compared with the strongly hydrophobic epoxy/FAS-TiO2/epoxy coating. The average surface roughness (Sa) of the epoxy/FAS-TiO2/epoxy coating was higher than that of the epoxy/TiO2/epoxy coating due to the formation of agglomerates. The biocompatibility evaluation revealed that the cell attachment was significantly higher on the epoxy/FAS-TiO2/epoxy and epoxy/TiO2/epoxy coatings compared with the pure epoxy coating. We also observed improved antibacterial properties for the epoxy coatings with the addition of both TiO2 and FAS-TiO2 nanoparticles.
RESUMEN
Controlling the surface wettability represents an important challenge in the field of surface functionalization. Here, the wettability of a stainless-steel surface is modified by 30-ns pulses of a Nd:YAG marking laser (λ = 1064 nm) with peak fluences within the range 3.3â»25.1 J cm-2. The short- (40 days), intermediate- (100 days) and long-term (1 year) superhydrophilic-to-(super)hydrophobic transition of the laser-textured surfaces exposed to the atmospheric air is examined by evaluating its wettability in the context of the following parameters: (i) pulse fluence; (ii) scan line separation; (iii) focal position and (iv) wetting period due to contact angle measurements. The results show that using solely a short-term evaluation can lead to wrong conclusions and that the faster development of the hydrophobicity immediately after laser texturing usually leads to lower final contact angle and vice versa, the slower this transition is, the more superhydrophobic the surface is expected to become (possibly even with self-cleaning ability). Depending on laser fluence, the laser-textured surfaces can develop stable or unstable hydrophobicity. Stable hydrophobicity is achieved, if the threshold fluence of 12 J cm-2 is exceeded. We show that by nanosecond-laser texturing a lotus-leaf-like surface with a contact angle above 150° and roll-off angle below 5° can be achieved.
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A study of oxide layers grown on 2205 duplex stainless steel (DSS) and AISI 316L austenitic stainless steel in simulated physiological solution is presented here in order to establish the possibility of replacement of AISI 316 L with 2205 DSS in biomedical applications. The results of the potentiodynamic measurements show that the extent of the passive range significantly increased for DSS 2205 compared to AISI 316L stainless steel. Cyclic voltammetry was used to investigate electrochemical processes taking place on the steel surfaces. Oxide layers formed by electrochemical oxidation at different oxidation potentials were studied by X-ray photoelectron spectroscopy, and their compositions were analyzed as a function of depth. The main constituents on both the investigated materials were Cr- and Fe-oxides. Atomic force microscopy topography studies revealed the higher corrosion resistance of the DSS 2205 compared to the AISI 316L under the chosen experimental conditions.