Yttria-stabilized zirconia (YSZ) is one of the most common materials used for a ceramic top coat in the thermal barrier coating (TBC). The high operating temperature used in the gas turbine engines causes the stress between the top coat and the bond coat. The stress relaxation can be assured by modifications of YSZ. Hence, studies on how to modify the chemical and phase composition of these coatings are still conducted. The laser flash analysis was used to determine the thermal diffusivity of composite mixture of 8 mol% yttria-stabilized zirconia with α-Al₂O₃ in the range of temperatures between 20 and 1100 °C. The powders were prepared with 5 and 25 mass% Al₂O₃ addition to 8YSZ. The particle size distribution was done for each powder to analyse the grain size after milling of the α-Al₂O₃ with 8YSZ in the ball mill. The density of each powder was measured in the helium pycnometer. The disc-shaped samples were produced by pressing using an isostatic press and then sintered at various temperatures: 1000, 1200, 1400 and 1600 °C.

Plant extracts are intensively studied as green corrosion inhibitors of aluminum. Because these extracts are complex systems, the influence of their individual constituents on the corrosion of aluminum should be determined. In this work, gallic acid was tested for the first time as a corrosion inhibitor of aluminum in orthophosphoric acid aqueous solution. So far, its potential inhibiting properties in acidic solutions were only suggested based on promising results obtained for various plant extracts. Evaluation of the potential inhibiting properties of gallic acid was performed using electrochemical methods. The corrosion potential, polarization curves, and impedance spectra of aluminum in 0.5 M orthophosphoric acid, at T = 303 K, were determined. The corrosion potential, corrosion current density, and corrosion rate of aluminum in orthophosphoric acid were equal to −1.151 V vs. Ag|AgCl (3M KCl) reference electrode, 36 μA∙cm⁻² and 0.39 mm∙year⁻¹, respectively. These values did not change with the addition of gallic acid. The results obtained show that gallic acid does not inhibit aluminum corrosion. UV-Vis absorption spectra of gallic acid solutions and quantum mechanical calculations show that this organic compound did not adsorb onto the aluminum surface under the studied conditions.

The continuous increase in the consumption of aluminium and its alloys has led to an increase in the amount of aluminium scrap. Due to environmental protection, and to reduce the costs of manufacturing aluminum in recent years, a lot of research is devoted to recycling of aluminum alloys. The paper presents the results of research concerning the possibility of manufacturing standardized alloy 2017A from commercial and post-production scrap by continuous casting. Obtained from recycling process ingots were subjected to analysis of chemical composition and intermetallic phase composition. Based on the results of light microscopy (LM), scanning electron microscopy + electron dispersive spectroscopy (SEM + EDS), and X-ray diffraction (XRD) the following phases in the as-cast state were identified: θ-Al₂Cu, β-Mg₂Si, Al₇Cu₂Fe, Q-Al₄Cu₂Mg₈Si₇, and α-Al₁₅(FeMn)₃(SiCu)₂. During solution heat treatment most of the primary precipitates of intermetallic phases, like θ-Al₂Cu, β-Mg₂Si, and Q-Al₄Cu₂Mg₈Si₇, were dissolved in the solid solution α-Al, and during natural and artificial aging they precipitate as strengthening phases θ-Al₂Cu and Q-Al₄Cu₂Mg₈Si₇ with high dispersion. The highest hardness—150.3 HB—of 2017A alloy was obtained after solution heat treatment from 510 °C and aging at 175 °C. In the static tensile test the mechanical (R_m and R_p0.₂) and plastic (A₅) properties were determined for 2017A alloy in the cast state and after T4 heat treatment. The highest strength properties—tensile strength R_m = 450.5 MPa and yield strength R₀.₂ = 268.7 MPa with good relative elongation A₅ = 14.65%, were obtained after solution heat treatment at 510 °C/6 h/water quenching and natural aging at 25 °C for 70 h. The alloy manufactured from recycled scrap is characterized by relatively high mechanical properties.

Advanced aircraft gearboxes operate under high mechanical loads. Currently, aircraft gears are manufactured from chromium–nickel–molybdenum steel grades such as AISI 9310 or Pyrowear 53. The major causes of gear failure are wear and fatigue cracking. As the crack initiation occurs predominantly on the component surface, the gears are routinely subjected to surface hardening processes such as low-pressure carburizing and case hardening. The gears are manufactured in a multiple operation process, in which teeth grinding is a crucial step. Selection of improper grinding conditions can lead to local heat concentration and creation of grinding burns, which are small areas where microstructure and properties changes are induced by high temperature generated during grinding. Their presence can lead to significant reduction of gear durability. Therefore destructive and non-destructive (NDT) quality-control methods such as chemical etching or magnetic Barkhausen noise (MBN) measurements are applied to detect the grinding burns. In the area of a grinding burn, effects related to the over-tempering or re-hardening of the carburized case may occur. In this paper, the results of the studies on the characterization of microstructure changes caused by local heating performed to simulate grinding burns are presented. The areas with the over-tempering and re-hardening effects typical for grinding burns were formed by laser surface heating of carburized AISI 9310 steel. Analyses of the microstructure, residual stresses, retained austenite content, and non-destructive testing by the MBN method were performed. The correlation between the MBN value and the properties of the modified surface layer was identified. It was also found that the re-hardened areas had similar characteristics of changes in the Barkhausen noise intensity, despite the significant differences in the width of the overheated zone, which depended on the laser-heating process conditions.

Corrosion inhibition of aluminium alloys in the acidic solutions is important in the aluminium finishing industry (stripping solutions for anodic films). Sodium molybdate is a potential replacement for chromate-containing species used in the stripping solutions. It was tested as the corrosion inhibitor of 2024 aluminium alloy in orthophosphoric acid solutions. A corrosion rate of the alloy as a function of an initial concentration of sodium molybdate and temperature was determined by using gravimetric and gasometric methods. The corrosion rate was significantly lower in the solutions containing over 5 mM of sodium molybdate when compared to the uninhibited solution. The inhibition efficiency decreased with the increase of the temperature for the constant concentration of sodium molybdate. Sodium molybdate reduced the corrosion of the alloy by adsorption as well as formation of insoluble corrosion products on the alloy.