The authors studied the influence of Mo and C on the properties of the CoCrNiFeMnNb alloy system. Quasi-high-entropy alloys (QHEAs) were smelted by partially using ferroalloys in the charge, unlike classical high-entropy alloys (HEAs). The Mo content was 2 and 4% mass. The C content was 0.45% mass in the experimental alloys. The C content was determined based on the initial content in the charge. The experimental alloy microstructure was represented by a solid FCC-type solution; Laves phases of various compositions; Me1Me2-type intermetallics; carbides Nb0.8, Cr0.2C, and Mo0.5NbC; and μ-phase NbCo2. All experimental alloys had higher hardness, strength, and wear resistance than the alloy without Mo and C. Increasing the Mo content in the alloy to 4% mass increased the hardness and, in particular, the wear resistance of the alloy. Strengthening the alloy with elements Mo and C is associated with forming a finer grain. Grain growth was limited by implementation phases, as well as dispersion strengthening due to solid implementation phases of various origins being formed.
The article investigates Co-(C-Pd) multilayer coatings produced by magnetron sputtering, focusing on their structure and magneto-optical behavior. Film thickness was controlled by the number of layers, and X-ray diffraction was used to analyze structural features. Magneto-optical properties were measured by the transmission line method. Impedance spectroscopy (50 Hz–100 MHz) showed decreasing phase angle at high frequencies, indicating dielectric losses. Charge accumulation was influenced by crystallite boundaries, bulk resistance, and surface effects. Very high ε′ and ε″ values were observed, with low-frequency growth explained by Maxwell–Wagner polarization. Frequency dependence of dielectric loss and conductivity confirmed electromagnetic absorption. Thicker multilayers demonstrated enhanced magneto-optical characteristics, underscoring the potential of Co-C-Pd coatings for spintronic and data-storage technologies.
The tribological behavior of self-lubricating spherical bearings in aerospace applications is crucial for ensuring reliability under dynamic loads. This study employs Computational Fluid Dynamics (CFD) to analyze the interactions between contacting surfaces, focusing on pressure distribution, shear stress, heat flux, and elastic deformation. By simulating various operational conditions, including different rotational speeds and the use of solid lubricants like talc and graphite, the research evaluates their effectiveness in reducing friction and managing thermal effects. Findings reveal that rotational speed significantly influences tribological performance, with graphite outperforming talc in minimizing friction, heat generation, and wear at high speeds. While talc reduces friction, it induces higher shear stresses and elastic deformation, making graphite a more suitable lubricant for demanding aerospace applications. This, study contributing to enhanced performance and durability of self-lubricating bearings in critical aerospace.
The hydrodynamic plain bearing relies on the generation of a lubricant film through the rotational movement of the journal. As the journal rotates, it creates a layer of lubricant between the bearing and journal surfaces. This lubricant film separates the two surfaces, preventing direct contact and minimizing friction and wear. The high speeds can lead to severe conditions such as cavitation due to rapid oil evaporation, which introduces a new phase into the flow. In this study, it is anticipated that a two-phase flow will occur through the shaft-bushing conjunction because of the rupture of the lubricating film near the contact outlet. Pressure disturbances above these rupture zones may induce vapor-cavity formation at a small scale. A numerical analysis was conducted by solving Navier–Stokes continuity equations and vapor-transport equations. The k-epsilon model was used to analyze friction at the fluid-bearing interface for the turbulent regime. The results indicate that higher flow velocity values and pressure were observed in the case of two-phase flow compared to one-phase flow.
Photocatalytic coatings with self-cleaning properties are becoming increasingly more popular due to the increased awareness of the importance of cleaning and the associated high cost of cleaning supplies and services. This research investigated self-cleaning photocatalytic polydimethylsiloxane (PDMS)/titanium dioxide (TiO2) nanocomposite coatings and focused on selecting the optimal TiO2 phase and concentration. To date, the comparison of the different TiO2 phases as a nanocomposite coating has not been sufficiently considered. PDMS/TiO2 nanocomposite coatings with three nanomaterial (NM) samples (an anatase, rutile, and mixed phase) and three concentrations of TiO2 (0.6, 1 and 3 w/v%) were prepared, applied to glass slides by dip coating, and tested with respect to hydrophobicity, surface stability, antifogging, and photocatalytic properties. It was found that a stable hydrophobic coating with the optimal photocatalyitc performance was produced with 3 w/v% anatase TiO2.
