Solid State Phenomena Vol. 394

Abstract: This work examines the effects of environmental and electrochemical conditions on the Time to Failure (TTF) and the Embrittlement Index (EI) of S2507 stainless steel and observes the alterations in microstructure which occurred before and on solution annealing. Experimental evidence demonstrates that high degradation of the material is caused by differences in the electrochemical potentials and exposures to corrosive conditions. The possible connection between TTF, EI and the material degradation is discussed with an emphasis on the influence of electrochemical stress on the progression of the hydrogen embrittlement. Also, examination of microstructures with the Scanning Electron Microscope (SEM) is used, offering an explanation of alterations in grain architecture and morphological distribution before and after solution annealing, which plays the role of explaining the behavior of the material at stresses. The results have noted that environmental and electrochemical conditions should be optimized to improve the durability of S2507 stainless steel.

Abstract: Alloy-based turbine components operate under extremely high temperatures and corrosive conditions, which often lead to surface degradation and material deterioration. To enhance their durability, these components are typically protected by cermet coatings that act as a barrier against harsh operating environments. This study investigates the influence of carbide alloy powder coating (WC-Co + 70% NiCrBSi) on Ti-31 special alloy and evaluates its effectiveness in resisting hot corrosion. Both uncoated Ti-31 and WC-Co + 70 wt.% NiCrBSi coated Ti-31 specimens were subjected to hot corrosion testing in a molten salt (Na₂SO₄ + 60% V₂O₅) environment. Thermogravimetric analysis showed that the cumulative weight gain per unit area for the coated Ti-31 sample decreased by 94.6% compared to the uncoated sample. Microstructural examinations using SEM/EDS and XRD confirmed that the oxide scale formed on the coated specimen was protective in nature, effectively preventing the penetration of corrosive reaction products into the substrate.

Abstract: There is a need to improve the mechanical properties and corrosion resistance by reducing the harmful lead content. Adding nickel as a solid solution strengthening element will improve the microstructure and reduce the corrosion rate. However, nickel's mechanism and solubility limits in the copper-zinc matrix are poorly understood. This study aimed to examine the effect of nickel addition of 1% to 4% on solid solution strengthening, microstructural modification, and increasing the corrosion resistance of recycled brass alloys. The methods used include preparing alloy samples through melting and permanent casting, and characterization using X-ray Diffraction (XRD) analysis, Scanning Electron Microscopy (SEM), and corrosion testing. The results showed that adding nickel significantly increased the crystallite size and yield strength through a solid solution strengthening mechanism. The corrosion rate decreased linearly with increasing nickel content, indicating the role of nickel as an effective corrosion inhibitor. The main conclusion is that nickel can improve recycled brass's mechanical performance and corrosion resistance, significantly contributing to developing environmentally friendly and durable metal alloys for sustainable manufacturing applications.

Abstract: CH_x-TiNbAlN coatings were deposited on WC turning tools and silicon wafers using a radio frequency unbalanced magnetron sputtering system with acetylene fluxes in the range of 4 to 12 sccm. The hardness of the coatings decreased with an increasing acetylene flux. By contrast, the H/E ratio increased as the acetylene flux increased and reached a value of 0.097 for the CH₁₂-TiNbAlN coating. The CH₁₂-TiNbAlN coating was found to improve the wear resistance of the turning tool by around 15% compared to that of an uncoated tool.

Abstract: NbC_x coatings were deposited on SKH51 substrates by RF magnetron sputtering with different acetylene fluxes. The XRD analysis results showed that the crystalline structure of the coatings changed from NbC phase to amorphous phase as the acetylene flux increased. The coating hardness decreased, whereas the adhesion strength increased, with an increasing carbon content. The average friction coefficient of the coatings decreased as the carbon content increased. The coating deposited with an acetylene flux of 8 sccm showed the highest H/E ratio (0.073) and adhesion strength (HF 1) of all the coatings. Consequently, the coating exhibited the best tribological properties, including the lowest friction coefficient and lowest wear depth and wear rate, under normal loads of 2, 5 and 8 N, respectively.

Abstract: The development of durable hydrophobic coatings remains a significant challenge for industrial applications. This study addresses this by fabricating EP/modified-SiO₂ coatings. The silica nanoparticles (SiO₂) were first surface-functionalized with 3-Aminopropyltriethoxysilane (APTES) and tetraethoxysilane (TEOS) to enhance compatibility. The fabricated coatings were comprehensively characterized to assess their hydrophobic properties through water contact angle (WCA) measurements, surface morphology via roughness analysis, and chemical composition using Fourier-transform infrared (FT-IR) spectroscopy. The findings indicate that the coating with an M-SiO₂ to EP ratio of 2:1 exhibited superior performance, achieving the highest water contact angle of 123±1° and a surface roughness (Ra) of approximately 15.357 μm. FT-IR analysis confirmed the successful chemical modification of the nanoparticles, as evidenced by the disappearance of the characteristic -OH peak at 3348 cm^-1. These results suggest that the 2:1 ratio promotes an optimal surface morphology conducive to the Cassie-Baxter wetting state, thereby enhancing hydrophobicity. In contrast, a higher nanoparticle content was found to induce aggregation, which detrimentally affected the coating's hydrophobic performance.