Journal of Thermal Spray Technology最新文献

This research engineers a high-performance superhydrophobic composite system by synergizing an Al arc-sprayed bond coat with a nanostructured CeO₂ topcoat deposited via solution precursor plasma spraying (SPPS). The objective was to utilize the intrinsic micro-roughness of the arc-sprayed layer to stabilize a Cassie–Baxter wetting state without organic modifiers. Optimization of the SPPS process identified the critical parameters for achieving a hierarchical topography: a standoff distance of 7 cm, a liquid feed rate of 42 rpm, a transverse speed of 500 mm/s, and a total of 4 spray passes. This optimized protocol leveraged the “shadowing effect” of the Al bond coat (Ra ~ 13µm), resulting in a 90% reduction in the required spray passes compared to conventional coatings on smooth substrates. Microstructural analysis confirmed the formation of a phase-pure CeO₂ topcoat with a refined crystallite size of 81 nm. The resulting hierarchical architecture yielded a water contact angle of 151° and a contact angle hysteresis of 2°. Mathematical modeling via the Cassie–Baxter equation quantified a liquid–solid contact area fraction of 0.04, indicating that 96% of the droplet base was supported by trapped air pockets. Electrochemical performance evaluated via potentiodynamic polarization and electrochemical impedance spectroscopy after 96 hours of immersion in 3.5 wt.% NaCl demonstrated superior durability. The Al-CeO₂ composite exhibited a 128% increase in corrosion resistance and a 50.5% reduction in the corrosion rate compared to the bare Al bond coat. While the single-layer benchmark system experienced a 95.5% reduction in coating resistance due to electrolyte infiltration, the optimized Al-composite restricted degradation to 40%. Surface chemistry analysis via x-ray photoelectron spectroscopy revealed that the transition to superhydrophobicity is governed by the spontaneous adsorption of airborne volatile organic compounds, ensuring chemical stability up to 450°C. These results establish a robust, industrially scalable manufacturing route for protective coatings in aggressive marine environments.

NiCrAlY coatings hold broad application prospects in the aero-engine field owing to their excellent densification and microhardness. To address the lack of systematic research on process parameters for preparing NiCrAlY coatings via detonation spraying, this study adopted the uniform design method to investigate the effects of four key parameters (powder feeding angle, loading distance, control timing, and spraying distance) on the coating’s microstructure, porosity, and microhardness. Quadratic polynomial regression analysis was employed to optimize the process parameters. Results indicate that the coatings exhibit no obvious delamination, with an overall average porosity of 4.93% and an optimal porosity below 1%; microhardness is predominantly determined by the loading distance (dominant factor), followed by control timing and spraying distance, while the powder feeding angle has a negligible effect; the regression model has excellent fitting performance, with a coefficient of determination of 0.988; a microhardness exceeding 700 HV_0.2 is achieved within the parameter ranges of 75-100 mm spraying distance, 345.5-465.5 mm loading distance, and 10-15 Hz control timing.

Garnet-type Li₇La₃Zr₂O₁₂ (LLZO) is a promising solid electrolyte (SE) for solid-state batteries (SSBs). However, identifying a suitable processing method to allow dense film fabrication without high sintering temperatures remains challenging. Powder aerosol deposition method (PAD, a.k.a. ADM) enables the fabrication of dense LLZO films at room temperature. To date, studies on PAD-LLZO films primarily addressed the electrical properties in terms of conductivity, while their cycling performance remains largely unexplored. In this study, we show that PAD-LLZO films can be used for the reversible transport of lithium with current densities up to 0.41 mA cm⁻² with no thermal post-treatment of pristine films after deposition, albeit at high overvoltage. A mild annealing at 400 °C is performed to reduce microstrain, which is known to lead to high overvoltage during cycling in the as-deposited state. Higher ionic conductivities are achieved after annealing, while the cycling stability deteriorates. These phenomena are attributed to reduced compressive stress as well as microstrain after annealing of the PAD-LLZO films with a nanocrystalline microstructure. Based on these assumptions, we propose a possible strategy to improve cycling stability by adapting a post-treatment process to reduce the volume fraction of grain boundaries by controlled grain growth.

Yttria-stabilized zirconia (YSZ)-based abradable sealing coatings (ASCs) have attracted increasing attention in aero-engine sealing systems. However, their wear resistance at high temperatures remains a critical concern. In this work, two coatings with different unmelted nanoparticle contents (UNCs) were prepared by supersonic atmospheric plasma spraying (SAPS), and the influence of UNC on the high-temperature tribological performance of YSZ ASCs was systematically investigated. The microstructure, phase composition, and wear behavior of coatings were characterized using scanning electron microscopy, X-ray diffraction, and high-temperature tribological tests, respectively. The results showed that at a temperature of 1000 °C, changing the UNC significantly altered the friction coefficient and wear rate of the ASCs. For both coatings, wear behavior is primarily governed by abrasive wear, accompanied by extensive adhesion of wear debris. At elevated temperature, the unmelted nanoparticles act as weak regions within the coating. Under friction-induced shear stresses, they preferentially fragment and detach, which improves the abradability. These findings provide insights into the structural design of high-temperature ceramic-based ASCs.

The development of low-cost and durable electrocatalysts for the hydrogen evolution reaction (HER) is essential for the large-scale implementation of water electrolysis technologies. In this study, Fe-based (W,Ti)C composite coatings were successfully fabricated for the first time using a scalable wire-arc-spraying process and evaluated as electrocatalysts for HER in alkaline media. Structural and microstructural analyses revealed a heterogeneous architecture composed of α-Fe, WC, W₂C, TiC, Fe₃C, and minor oxide phases, forming a conductive and catalytically active network. SEM and optical profilometry confirmed the presence of a hierarchical rough surface morphology, which enhances the electrochemically active surface area and facilitates electrolyte access. Electrochemical measurements demonstrated efficient catalytic behavior, characterized by low charge-transfer resistance, stable interfacial kinetics, and a mixed capacitive–faradaic response. The Fe-based (W,Ti)C coating exhibited a HER onset potential of approximately 0.2 V versus RHE and a Tafel slope of about 0.62 V dec⁻¹, indicating a Volmer–Heyrovsky reaction mechanism. Furthermore, long-term electrolysis tests showed a stable hydrogen production rate of 2551.92 µmol h⁻¹, confirming the durability of the coating under operating conditions. These findings demonstrate that wire-arc-sprayed Fe-based (W,Ti)C coatings represent a promising and industrially scalable class of noble-metal-free HER electrocatalysts, offering a cost-effective pathway for sustainable hydrogen production.

As a critical microstructural characteristic of thermal barrier coatings (TBCs), porosity serves to reduce their thermal conductivity, thereby enhancing its heat insulating capability. In this work, porous thermal barrier coatings were fabricated via atmospheric plasma spraying (APS) using a composite powder blended of Yb₃Al₅O₁₂ (YbAG) and polymethyl methacrylate (PMMA) in a weight ratio of 90:10. The effects of the PMMA pore-forming agent on the coating’s microstructure, thermal insulation, thermophysical properties and thermal cycling performance were systematically investigated. The findings revealed a 5.23% enhancement in the coating’s porosity with the addition of PMMA. The heat insulation capability was improved by 24.1 °C, corresponding to 16.07% decrease in thermal conductivity. Conversely, the thermal cycling lifetime diminishes with PMMA addition, which could be explained by a fraction rise in the amorphous phase as well as by a decline in mechanical properties. The degradation of the coatings is primarily caused by the volume shrinkage caused by sintering transformation and the stress resulting from thermal expansion mismatch.

Industry 4.0 and 5.0 approaches in thermal spraying seek to use AI modeling to tackle research issues. One common multi-criteria decision-making task is the optimization of deposition conditions to achieve desired coating characteristics and, based thereon, performance targets of specific interest. With most thermal spray technologies, this is a complex task due to the large number of influencing factors. Innovative, human-centered decision support needs to address two key challenges: (1) use experimentally collected small and smart data sets of coating characteristics and corresponding performance; and (2) integrate expert knowledge into modeling in order to obtain user-friendly, transparent decision recommendations. The present contribution illustrates how a model-based description of relationships between process conditions, coating characteristics (e.g., hardness), performance measures (e.g., sliding and abrasive wear, cavitation), and resource efficiency criteria (e.g., deposition rate) for smart data from HVAF- and HVOF-sprayed WC-CoCr coatings can be used to establish decision support. With the fuzzy pattern classification models used here, it is possible to describe patterns in a multidimensional feature space taking uncertainties and small data into account. The models are capable of formally representing complex relationships between input, process and output variables and enable predictions for the adjustment of input parameters such as nozzle type and particle size in order to optimize the coating performance flexibly, according to the defined application-related goal criteria.

Interfacial bonding in cold-sprayed polymer and composite deposits depends on complex mechanisms that remain insufficiently understood, limiting component reliability under extreme conditions encountered in aerospace and automotive systems. The present study addresses this knowledge gap by elucidating the bonding mechanisms in high-performance poly(ether-ether-ketone) (PEEK)-boron nitride nanoplatelet (BNNP) nanocomposites. Single-splat studies of pure PEEK and PEEK-BNNP composite particles, combined with microstructural, spectroscopic, and mechanical characterization, were conducted to elucidate particle–substrate interactions, revealing that impact-induced plastic deformation and molecular-level chemical interactions drive splat bonding. Knowledge from these single-impact studies was applied to fabricate bulk PEEK and PEEK-BNNP deposits using identical deposition parameters, enabling correlation between splat-scale bonding and deposit consolidation. Fourier-transform infrared spectroscopy confirmed interfacial chemical bonding through O–H···O=C and B–O linkages between PEEK chains and BNNPs. Incorporation of BNNPs increased deposition efficiency from 88% to 95%, enhanced hardness by 243%, and raised the elastic modulus by 62% due to their ability to promote interparticle bonding and stress transfer during impact. Thermal analysis revealed an 18% improvement in the degradation temperature, indicating superior thermal stability. These findings establish the mechanistic relationship between impact-driven densification, interfacial bonding, and the resulting mechanical and thermal properties, advancing cold spray for durable, high-temperature PEEK-based nanocomposite deposits.