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 MoS
nanotubes into the lubricant. MoS
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 MoS
nanotubes/water lubrication.
SiO
x
-like coatings were deposited on glass slides from a hexamethylsiloxane precursor by plasma-assisted CVD (PACVD). Surface energies (23.1-45.7 mJ m
−1
) were correlated with the degree of ...surface oxidation and hydrocarbon contents. Tapping mode AFM revealed a range of surface topologies with Ra values 1.55-3.16 nm and RMS roughness 1.96-4.11 nm. Settlement of spores of the green alga Ulva was significantly less, and detachment under shear significantly more on the lowest surface energy coatings. Removal of young plants (sporelings) of Ulva under shear was positively correlated with reducing the surface energy of the coatings. The most hydrophobic coatings also showed good performance against a freshwater bacterium, Pseudomonas fluorescens, significantly reducing initial attachment and biofilm formation, and reducing the adhesion strength of attached bacterial cells under shear. Taken together the results indicate potential for further investigation of these coatings for applications such as heat exchangers and optical instruments.
As a surface-hardening technique, plasma nitriding is a common procedure for improving the properties of conventional Ni-based alloys. The diffusion of nitrogen hardens a layer on the surface of the ...alloy, leading to better wear resistance and a higher coefficient of friction, as well as a higher surface hardness. This study reports the effect of plasma nitriding on additive-manufactured (AM) Inconel 625 (IN625) compared to its conventional manufactured and nitrided counterparts. The samples produced with the laser powder-bed fusion (LPBF) process were subsequently plasma nitrided in the as-built condition, stress-relief annealed at 870 °C and solution treated at 1050 °C. The plasma nitridings were carried out at 430 °C and 500 °C for 15 h. The growth kinetics of the nitride layer of the AM samples depends on the prior heat treatments and is faster in the as-built state due to the specific cellular structure. The lower nitriding temperature leads to the formation of expanded austenite in the nitride layer, while at the higher nitriding temperature, the expanded austenite decomposes and CrN precipitation occurs. The XRD and SEM analyses confirmed the presence of two layers: the surface layer and the diffusion layer beneath. The lower nitriding temperature caused the formation of expanded austenite or a combination of expanded austenite and CrN. The higher nitriding temperature led to the decomposition of the expanded austenite and to the formation/precipitation of CrN. The higher nitriding temperature also decreased the corrosion resistance slightly due to the increased number of precipitated Cr-nitrides. On the other hand, the wear resistance was significantly improved after plasma nitriding and was much less influenced by the nitriding temperature.
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•Nitriding of IN625 alloy causes combination of austenite/expanded austenite and diffusion layer.•Growth kinetics depends on production route, heat treatment, nitriding temperature.•At lower nitriding temperature expanded austenite forms in the nitride layer.•Expanded austenite decomposes at higher nitriding temperature and CrN forms.•Better corrosion performance is obtained at lower nitriding temperature.
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•Laser ablation enables controlled biodegradability of Fe–Mn alloy.•Increased corrosion appears due to laser-induced high-temperature oxides.•XPS reveals mechanism for ...biodegradability via shift in surface Fe/Mn ratio to Mn.•Corrosion rate for laser-textured Fe–Mn is 10-times higher as for Fe.•Laser-triggered corrosion is self-driven leading to biodegradability of bulk.
In this study we report the influence of laser ablation on the controlled biodegradability of a Fe–Mn alloy developed for medical implants. After texturing by a nanosecond Nd:YAG laser, the surface expressed extreme super-hydrophilic wetting properties, since laser ablation led to micro-channels and chemical modification resulting in nanostructured metal oxides. The influence of functionalized surface properties on corrosion behavior was examined on molecular level by using X-ray photoelectron spectroscopy. Results reveal that the oxide layer after the laser texturing of Fe–Mn alloy consists mainly of Fe2O3 and FeO, with the content of Mn in the oxide layer being significantly higher than in the bulk. The results of the electrochemical measurements clearly demonstrate the superior biodegradability of the Fe–Mn alloy samples functionalized by laser ablation. Here, the laser-triggered corrosion is self-driven by further production of corrosion products that leads to biodegradability of the whole sample.
Epoxy/TiO
/epoxy and epoxy/FAS-TiO
/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/TiO
/epoxy and epoxy/FAS-TiO
/epoxy coatings. The epoxy and epoxy/TiO
/epoxy coatings were hydrophilic compared with the strongly hydrophobic epoxy/FAS-TiO
/epoxy coating. The average surface roughness (
) of the epoxy/FAS-TiO
/epoxy coating was higher than that of the epoxy/TiO
/epoxy coating due to the formation of agglomerates. The biocompatibility evaluation revealed that the cell attachment was significantly higher on the epoxy/FAS-TiO
/epoxy and epoxy/TiO
/epoxy coatings compared with the pure epoxy coating. We also observed improved antibacterial properties for the epoxy coatings with the addition of both TiO
and FAS-TiO
nanoparticles.
Multi-material components, also known as functionally graded materials (FGMs), are innovative materials that possess unique properties due to their composition and have many potential applications in ...engineering and science. The effect of the heat treatment (HT) of functionally graded materials 15–5 precipitation-hardened (PH) martensitic steel and SAF 2507 duplex stainless steel (and the opposite order of deposition, i.e. SAF 2507 first followed by 15–5 PH stainless steel) on the interface microstructures was systematically investigated in the presented research. The choice of HT followed the trend of optimum post-processing for the individual alloys. A significant modification in the interface microstructure, characterized in the microstructural transition zone (MTZ) formed above the fusion line. Mechanical properties by miniaturized testing method including hardness measurement characterized both types of interfaces. The sequence of the materials’ application did not have a significant effect on their final mechanical tensile properties in the heat-treated states. Nevertheless, the microstructural change at the MTZ led to drop in the hardness at the interface. The research presents heat-treated FGMs in a horizontal configuration to form a high-quality metallurgical joint between heterogeneous materials manufactured by powder-based directed energy deposition method.
Graphical abstract
PROGRAM AND BOOK OF ABSTRACTS ICM&T 2023 Godec, Matjaž; Donik, Črtomir; Kocijan, Aleksandra ...
Materiali in tehnologije,
10/2023, Letnik:
57, Številka:
5
Journal Article
An AISI 316L surface was functionalized by the adsorption of hydrophilic epoxy and epoxy/TiO
/epoxy coatings and hydrophobic epoxy/fluoroalkylsilanefunctionalized FASTiO
/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 TiO
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/TiO
/epoxy coating, increased for the hydrophobic epoxy/FASTiO
/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/FASTiO
/epoxy coating compared to the hydrophilic pure epoxy and epoxy/TiO
/epoxy coatings.
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