Papers by Keyword: Nanohardness

Abstract: Since their early investigations, TiN coatings have sparked considerable interest because of their remarkable mechanical properties, especially their prominent hardness (30–60 GPa) and oxidation resistance. They are mainly used to harden and protect cutting or sliding tools and occasionally for decoration. Small quantities of different ligands, including Ni, Cu, or Co, are added to improve the smooth performance of cutting tools. These alloying elements lead to the formation of nanocomposites, potentially altering their mechanical characteristics and imparting notable flexibility. In this context, this study focuses on the production of pure TiN and Cu-doped TiN thin films. Magnetron sputtering was used as a deposition technique, simultaneously sputtering Ti and Cu-targets, both with high purity (99.99%), and in a gas mixture of Ar and N₂. X-ray diffraction, SEM, profilometry, nanohardness, and scratch test analyses were employed to characterize the TiN and TiN/Cu films. The results reveal that 3–4% of Cu content led to a slight decrease in hardness, while surface adhesion increased with the addition of copper. Furthermore, the elasticity of the doped films improved the strength and wear resistance of coatings with Cu compared to TiN films without added Cu.

Abstract: The composition, structure, and tribological characteristics at 20 °C and 500 °C of coatings obtained by the vacuum arc deposition method using a MAX phase Ti₂AlC based cathode were investigated. These characteristics were compared to those of titanium nitride coating. It was shown that at a potential of -50 V, a composite coating of TiC and Ti₃AlC phases forms. Meanwhile, at a potential of -100 V, a composite consisting of TiC and α-Ti is formed. At 20 °C, the friction coefficient and specific wear rate of these coatings in contact with a ball made of ShKh15 steel under a load of 2 N are comparable to those of TiN coating. At 500 °C, the wear resistance of the composite (TiC+α-Ti) coating is twice as high as that of TiN coatings. There was no clear correlation between microhardness and the tribological characteristics of the coatings.

Abstract: The low weight and high strength ratio of titanium alloy make TiO₂ nanotubes ideal for biomedical applications. Increasing the oxidation process has recently been studied as a means of encouraging the formation of nanotubes. This study synthesizes the TiO₂ nanotubes with different input voltages. There was an increase in nanotube growth rate as a result of de-ionized water in the electrolyte, as well as an increase in the input potential, which favours oxidation. An analysis of the surface morphology suggests that rib structures were generated in the area where corrosion results were greatly elevated. X-ray diffraction and nanoindentation were used to study phase transformations and nanohardness respectively.

Abstract: The mechanical and electrochemical properties of a low carbon steel alloy were improved with titanium (Ti) nitrides thin films. A nitriding process ensures the adhesion of the deposited thin films and provides the nitrogen source involved in the formation of the desired nitrides. A hybrid reactor was used to permit this duplex surface treatment and to avoid the oxidation of our samples. The X-ray diffraction revealed the formation of nitrided phases (TiN and Ti₂N). The scanning electron microscopy showed an improvement in the adhesion of the deposited thin films with increasing negative bias voltages. The nanohardness of the duplex treated samples was found to be improved. The results obtained after the corrosion tests indicate a reduction of electrochemical activity and therefore an improvement of corrosion resistance.

Abstract: TiCN thin coatings with various different carbon contents were deposited using cathode arc evaporation of pure titanium in a mixture of N₂ and C₂H₂ gasses at a constant pressure of 1.5 Pa. The analyses show a transition from a stoichiometric to a non-stoichiometric coating structure with an increasing C₂H₂ content. Moreover, the increase in the acetylene in the gas mixture leads to a decrease in the crystal phase from pure polycrystalline to pure amorphous. Nanohardness changes from 30.4 to 4.4 GPa and the cohesive failure of the coatings is in the range of 61 - 72 N. The tribology is estimated by the Ball-on-Disc method and an Si₃N₄ ball as the counterpart. The measured coefficient of friction is in the range of 0.2 - 0.56.

Abstract: The elastic modulus and nanohardness of denture bases may be different based on the type of material. The purpose of this study was to compare the elastic modulus and nanohardness of polyamide and polymethyl methacrylate (PMMA) denture base materials. Three polyamide denture base materials (Valplast, Lucitone FRS, and Thermoplastic Comfort System (TCS)) and one Polymethyl methacrylate (PMMA,Triplex Hot) denture base material (n=10) were evaluated to compare their elastic modulus and nanohardness values using an ultramicroindentation system (UMIS 2000; CSIRO, Lindfield, Australia). The data were statistically analyzed using one-way ANOVA, followed by Tukey HSD and Tamhane’s post hoc tests (α=.05). The elastic modulus and nanohardness of PMMA were significantly higher compared to the polyamide groups (P<.05). All the materials showed significant differences in each of their elastic modulus and nanohardness (P<.05). The values of nanohardness and elastic modulus of each group were as follows: Triplex Hot > Lucitone FRS > Valplast > TCS. The elastic modulus and nanohardness values varied among the polyamide denture base materials. PMMA showed higher elastic modulus and nanohardness than the polyamide. A strong positive correlation existed between elastic modulus and nanohardness of the denture bases tested (R² = 0.979, P<.05).

Abstract: Porosity, values of nanohardness and Young’s modulus of the specimens obtained with the method of selective laser melting were measured with optical methods, scanning electron microscopy and Nano Hardness Tester NHT-S-AX-000X device for measuring physicomechanical properties. Ti-45wt%Nb powder obtained with mechanical alloying was used for selective laser melting. The results have shown that increased heat input due to the laser power growth up to 80 W and scanning speed decrease down to 40 mm/s decreases the porosity of the specimen. The nanohardness average value is not sensitive to the changes of scanning modes in the investigated range. The Young’s modulus decreases with energy input increase.

Abstract: A microsecond pulsed laser beam was used to local magnetic domain modification of electrical grain oriented silicon steel. It was carried out using three different laser pulse regimes: a single pulse laser regime, a multipulse laser regime and a multipulse laser regime with modulation of laser pulses. The laser processing variables were pulse energy and and number of pulses. The samples were tested for nanohardness and coercivity before and after laser treatment. Light optical microscopy, scanning electron microscopy and magnetic force microscopy were used to observe the cross-sectional profile, surface of the samples, and magnetic domain visualization, respectively. The local laser treatment of grain oriented silicon steel surface has been studied in terms of its influence on the magnetic domains and coercivity. It was found that laser-modified samples showed coercivity improvement in comparison to the non-treated samples. The most significant improvement in coercivity was obtained in the modulated multipulse regime and negligible improvement in the single pulse laser regime. Three main effects responsible for the observed improvement were identified, namely: magnetic domain refinement, influence of number of laser pulses and shape of laser HAZ profile. The present work highlights on differences in the magnetic domain structure, microstructure of the laser modified material and basic electromagnetic and mechanical properties. In present study, the pulse laser surface processing was presented as a useful energy efficient alternative to other techniques e.g. mechanical scribing, electrical discharge scribing, plasma jet scribing, etc. The refined magnetic domains in electrosteels are responsible for the observed low coercivity, which indicates perspective application of the investigated laser modified steels in the power transformer cores with lower core losses.

Abstract: Structural and mechanical behavior of thin hydroxyapatite (HA) films deposited via radio-frequency magnetron sputtering on AZ91D magnesium alloy was investigated. Nanoindentationwas employed to evaluate nanohardness and Young’s modulus of the uncoated and HA-coated AZ91 magnesium alloy. The HA-coated AZ91D magnesium alloy exhibited a higher hardness of 7.1 GPa and a higher modulus of 86 GPa compared withthe uncoated substrate revealing a strong load-bearing capacity.

Abstract: The effects of residual stresses in thin W-C based coatings were investigated with the aim to find their influence on nanohardness and indentation modulus. Ten samples of W-C based coatings were deposited on microslide glass substrates using DC magnetron sputtering at the identical deposition parameters. Their thickness was in the range from 500 to 600 nm. The residual stresses in the coatings varied from 1.5 GPa up to 4.4 GPa. Increase of residual stress caused linear increase of H_IT from 16 to 19.5 GPa. This increase was only the result of the compressive stresses. E_IT of the studied coatings was not sensitive to residual stresses and corresponded to 185 GPa ± 15 GPa.