Search Results (4)

This study proposes a novel synergistic design strategy to enhance the oxidation resistance of FeNiCuAl-based high-entropy alloys by integrating multi-element alloying (Cr-Co-Mn), trace Y modification, and laser-cladding-induced nanocrystallization. While the Base Alloy exhibited a mass gain of approximately 15 mg/cm² after oxidation at 900 °C for 120 h, the addition of Cr_2.5Co_2.5Mn_2.5 promoted the formation of a multilayered oxide scale (outer MnCr₂O₄/inner Al₂O₃), reducing the parabolic oxidation rate constant to 1.7 × 10⁻⁵ mg²·cm⁻⁴·s⁻¹. The originality of this work lies in the coupling of compositional and microstructural engineering; further addition of 0.5 at.% Y decreased this constant to 1.7 × 10⁻⁶ mg²·cm⁻⁴·s⁻¹—a three-order-of-magnitude reduction relative to the Base Alloy, while increasing the apparent oxidation activation energy to ~350 kJ/mol. After 100 thermal cycles at 1000 °C, the designed alloy showed a mass change of only 0.05 ± 0.02 mg/cm², with its critical load and interfacial fracture energy reaching 78 N and 14.8 J/m², respectively. Furthermore, the alloy retained a hardness of 310 HV, an elastic modulus of 135 GPa, and a tensile strength of 240 MPa at elevated temperature. These results demonstrate that the synergistic integration of chemical and structural optimization provides a new paradigm for designing low-cost, high-performance FeNiCuAl-based protective coatings. Full article

Thermal barrier coatings (TBCs) prepared using the atmospheric plasma spraying method fail mainly due to coating delamination caused by thermal mismatch in the absence of high temperature assessment. In this study, the thickness optimization of multiple ceramic layers in a TBCs and the influence of the interface structure on the residual stress of the coating were investigated using a finite element simulation method. The results showed that varying the thickness of each layer of a TBCs with multiple ceramic layers affects the distribution and magnitude of the residual stress of the coating. Therefore, a reasonable range of thickness for each layer can be determined. The thickness of the bonding layer should be 110 μm, the thickness of YSZ layer should be about 270 μm, the thickness of tantalate layer should be about 70 μm, and the thickness of Al₂O₃-YAG layer should be about 100 μm. Simultaneously, the results show that a rough interface can be more effective in reducing the relief of stress concentrations compared to a smooth interface, but the stress values increase. Full article

The article describes the effect of heat treatment on the structural-phase state and properties of a multilayer Cr-Al-Co-Y coating obtained by magnetron sputtering. Heat treatment was carried out at 400, 800 and 1000 °C. The study of the microstructure was carried out by electron microscopy with energy dispersive analysis and powder X-ray diffraction. The surface of the samples was studied by atomic force microscopy. The thickness of the Co-Cr-Al-Y coatings was 1.5–1.7 ± 0.2 µm. The obtained coatings are characterized by a hardness of 4.7–6.4 GPa. A distinctive feature of the layers is the absence of a crystalline structure in some areas of the coating. The main process occurring during the thermal treatment is the formation of a spinel-type phase. For a single-layer sample after heat treatment at 400 °C, it was not possible to fix extraneous reflections except for the reflections of the silicon substrate 111 and 220. For the rest of the samples, the appearance of reflections of a number of phases was noticed, such as: SiO₂, CoO, AlSi_0.5O_2.5 and CrAl_0.42Si_1.58. An increase in the treatment temperature up to 800 °C did not lead to significant changes. In the case of the multilayer sample, the reflections of various impurity phases disappeared and the Co₃O₄ phase was formed. For samples treated at 1000 °C, the formation of a spinel-type phase (Co₃O₄-CoCr₂O₄) was observed in all cases. Data on the structural-phase state and properties of the multilayer Co-Cr-Al-Y coating can be used to predict the nature of such coatings after heat treatment. Full article

Cold spray is a solid-state additive manufacturing process that has been increasingly used for restoration of damaged parts. Due to the nature of powder solid-state bonding, cold spray coatings usually possess pores in the microstructures. Heat treatment has been widely used as a post-processing method to reduce the porosity of cold sprayed coatings. However, it usually requires the whole component to be treated in the furnace and typically takes a few hours to finish the treatment. This study aims to develop a localized and rapid post-processing method for cold sprayed coatings. Multi-layer cold sprayed coatings of CoNiCrAlY on an Inconel 718 substrate were produced. Then the coatings were heat treated at 800 °C, 900 °C, 1000 °C and 1100 °C by rapid induction heating. The porosity level of the coatings reduced significantly after induction heating for a short period of merely 10 min. This is attributed to the preferential Joule heating at pore regions, which results in pore closures within the coatings. The potential application of induction heating as a rapid post-processing method for cold spray coatings has been demonstrated in this work. Full article