Journal of Thermal Spray Technology最新文献

Ti-6Al-4 V is commonly used in gas turbine engines and is sometimes subject to wear during operation. To address this, cost-effective and environmentally friendly solutions are being explored, with a focus on solid-state additive manufacturing techniques such as cold spray (CS). CS can create a dense structure; however, the existing porosity adversely affects the mechanical properties. To reduce the need for post-heat-treatment, this paper considers inner-diameter high- velocity air-fuel (ID_HVAF) as an alternative repair method which is a relatively low-temperature HVAF process that can deposit coatings with microstructures close to those observed in CS coatings. ID_HVAF process can deposit particles at high velocities and relatively low temperatures so that a significant portion of the particles forming the coatings are deposited in the solid state. This work is based on the deposition of Ti-6Al-4 V coatings using the ID_HVAF gun. During deposition, increasing the nozzle length increases the particle velocity and substrate temperature. The particles hit a softer surface with higher kinetic energy, thus increasing the density of the samples. However, HVAF will still oxidize some Ti-6Al-4 V particles and produce vanadium oxide. To study the tribological behavior, Ti-6Al-4 V counterballs were used to simulate the dovetail interface. According to the result, the top deposited layers were densified by the application of counterbalance force. Compared to an α-β Ti-6Al-4 V bulk sample, the coatings have a smaller wear track width and a greater wear depth, resulting in less wear on the counterballs. Each of the three samples shows a combination of abrasive and adhesive wear. The low cohesion between the particles in the coatings results in smaller oxide debris with a greater amount on the wear track of the coatings. By acting as a roller between the counter ball and the coating, this debris can slightly reduce the coefficient of friction.

Photoelectrochemical (PEC) water splitting is a viable route for green hydrogen generation. In PEC cells, the electrodes are coated with suitable semiconductor materials, which absorb the sunlight, generating charge carriers that are used to split water molecules into H₂ and O₂. CuFeO₂ is one promising photocathode material for water splitting. However, its performance is limited by electron/hole pairs recombination within the film and at the film/substrate interface. Aerosol deposition (AD) can be employed to minimize charge recombination by spraying dense, thin films and by establishing a good back-contact interface. In this study, CuFeO₂ powders were synthesized through a conventional solid-state technique and sprayed by AD under varied parameter sets. The effect of particle size distributions, carrier gas, gas pressure and substrate temperature was investigated. The best spraying parameter set was then tuned to obtain thin coatings (< 1 µm). Single-particle deformation and coatings microstructure were investigated by scanning electron microscopy. Optical properties of CuFeO₂ films were analyzed by UV–Vis spectroscopy, while photoelectrochemical performances were estimated through amperometry tests under simulated sunlight. The results of this research show that CuFeO₂ photocathodes can be successfully manufactured by AD. Their performance can be optimized by adjusting coating thickness and by annealing in air.

Microstructural modeling at progressive length scales can enable the prediction of thermal and mechanical properties of thermal sprayed coatings with hierarchical features. Object-oriented finite (OOF2) element modeling conducted using microstructural images, although a powerful technique, has been employed to a limited extent in thermally sprayed materials. Consequently, there is little scientific understanding of the efficiency of the OOF2 technique for estimating bulk properties. For the first time, this study provides a comprehensive analysis of these factors’ role in the OOF2 technique’s capability to predict thermal and mechanical properties in ceramic and metallic coatings manufactured by plasma spray, high-velocity oxyfuel (HVOF) spray, wire_arc spray, and cold spray. The prediction efficiency generally increases for larger grain sizes as overall microstructural features are captured even at lower magnifications. The same effect is obtained in microstructures having lower and uniformly shaped pores. The data on the porosity suggest that OOF2 predictions are most accurate when conducted on coatings manufactured using sintered feedstock because of the dense powder. In contrast, OOF2 predictions are the least accurate when hollow spherical (HOSP) feedstock having empty cores is used. These multiscale facets of microstructure, porosity, etc., thus, highlight the importance of the selection of the representative volume element for accurate analysis in OOF2, which, depending upon the process, is captured at 300× − 500× for HVOF and wire-arc spray, and 1000× − 15,000× magnifications for plasma and cold spray. This overall assessment charts the relative importance of variables such as grain size, porosity, and feedstock as compared to that of the process and anisotropy in the prediction of properties in thermally sprayed coatings. While these conclusions are based on the limited literature of 37 articles, this study makes a bold attempt towards a guidebook for future thermal spray researchers in conducting more accurate OOF2 analysis.

Metal-supported solid oxide fuel cells have broad application prospects in distributed power generation, transportation, military, and other fields. The electrochemical performance of the cell is still a challenge in commercial applications. Regulating the anode microstructure and optimizing polarization characteristics are effective methods. In this study, atmospheric plasma spraying technology is chosen to prepare the Ni-Gd_0.2Ce_0.8O_1.9(GDC) anodes using different low plasma powers (18, 21, 24 kW), which is cost-effective and efficient. The power effect on anode microstructure and electrochemical performance is investigated. The results show that as the plasma power decreases from 24 to 18 kW, the anode’s gas permeability and three-phase reaction boundary (TPB) gradually increase. Reducing the spraying power can decrease polarization resistance and improve power density. The 18-kW anode exhibits the lowest polarization resistance and the best output performance. Open-circuit voltage and maximum power density are 1.03 V and 0.89 W cm⁻² at 750 °C, respectively. The polarization resistance and total resistance are 0.19 and 0.40 Ω cm², respectively. The experimental results prove that atmospheric plasma spraying can realize the rapid and low-cost anode preparation for high-performance MS-SOFC.

This work investigated the trade-off among cavitation erosion resistance, corrosion resistance, and antifouling properties in HVOF-sprayed WC-10Co4Cr coatings. By adding 316L stainless steel (316L) and copper to WC-10Co4Cr coatings, this work aimed to enhance their antifouling ability while maintaining their cavitation erosion and corrosion resistances, presenting a comprehensive evaluation of the modified coatings, including their microstructure, hardness, fracture toughness, and resistance to cavitation erosion, corrosion, and biofouling. The results revealed that Cu addition significantly improved the antifouling property but at a cost of the compromised cavitation erosion and corrosion resistances. In contrast, 316L enhanced the cavitation erosion and corrosion resistances but did not effectively improve the antifouling property. The dual addition of Cu and 316L demonstrated a balanced performance in all three aspects. This research contributed to the development of HVOF-sprayed WC-CoCr coatings suitable for marine environments, suggesting further optimization possibilities by altering Cu and 316L contents.

In this work, Fe-based alloy coatings were prepared on the surface of ductile iron by laser cladding. To improve its wear resistance and consider the economic and time cost of other post-treatment processes, laser remelting was chosen to strengthen the coatings. The effect of laser remelting energy density (0−11.45 J/mm²) on the phase composition, microstructure evolution, hardness, and wear resistance of the coatings were investigated. The results show that the coating consists of γ-(Fe, Cr) and carbides and that remelting energy density has little effect on its phase composition. After remelting, the hardness uniformity of the coating was significantly improved, but increasing the remelting energy density had little effect on it. The hardness and wear resistance of the coatings were inversely related to remelting energy density. At a low remelting energy density of 5.66 J/mm², the hardness and wear mass loss of the coating were 111.49% and 54.36% of the original coating, respectively. The mechanism for the improved hardness and wear resistance is the microstructure refinement induced by laser remelting. Increased remelting energy density reduces the microstructure refinement of the coating, but the coatings still showed good hardness and wear resistance due to the diffuse distribution of carbides at higher remelting energy density conditions of 9.43-11.45 J/mm².

A high-performance Al₂O₃-PF composite coating was prepared on the surface of polymer matrix composite materials using supersonic high-energy plasma spraying technology. The bonding strength between the composite coating and the matrix was used as the evaluation index. The spraying process parameters were optimized using orthogonal experimental design method. Subsequently, the optimal process was verified based on single-factor experimental method, further exploring the influence mechanism of Ar flow rate, spraying current, spraying voltage, and second powder feeding position on the composite coating. Analysis shows that spray voltage, Ar flow rate, and spray current have a significant impact on the experimental results and are the main influencing factors; the second powder feeding position has a relatively small impact on the experimental results and is a secondary influencing factor.