Journal of Thermal Spray Technology最新文献

The high temperature catalytic and radiative performance are the intrinsic properties of the thermal protection materials, and the low catalytic coefficients and high emissivity reduce the thermal loads, which could enhance the heat resistance and prolong the service life under high temperature conditions. In this study, ZrB₂-SiC, ZrC-SiC, HfC-SiC and HfC ultra-high temperature ceramic (UHTC) coatings were fabricated using vacuum plasma spray technique. The catalytic coefficients and emissivity of the coatings were measured by the inductive coupled plasma wind tunnel and related equipments, and the effects of main and additive phases of the coatings on them were analyzed. Results demonstrated that the catalytic coefficients and emissivity of the ZrB₂-SiC and ZrC-SiC coatings exhibited similar values at 1500 °C, which is about 1.3 × 10⁻² and 0.8, respectively. Compared with the Zr-based coatings, the HfC-SiC coating possessed lower catalytic coefficients (1.053 × 10⁻²) and higher emissivity (0.92). Moreover, the addition of SiC was beneficial to the decrease of the catalytic coefficients of the HfC-SiC coating, but also led to a decrease of the emissivity. The catalytic and radiative behaviors of UHTC coatings were closely related to the oxidation products.

Cold spray has emerged as an effective technique for fabricating high-strength aluminum alloys, leveraging its solid-state nature to prevent melting and oxidation. Despite these advantages, challenges like porosity and residual stresses introduced during deposition necessitate post-deposition treatments to enhance mechanical properties. This study explores the evolution of microstructure and residual stress and their influence on hardness and tensile properties in cold-sprayed Scalmalloy deposits produced using helium (He) and nitrogen (N₂) as carrier gases, followed by direct aging and solution treatment with aging. He-sprayed deposits exhibited lower initial porosity (0.12 ± 0.03%) than N₂-deposits (1.20 ± 0.51%). Solution treatment increased porosity to 6.9% (He) and 2.5% (N₂) due to gas expansion within defects, while porosity remained unchanged after direct aging. Direct aging significantly reduced residual stresses, with a 69% reduction in He-deposit and a 55% reduction in N₂-deposit. The formation of Al₃(Sc_x, Zr_1−x) precipitates during aging led to precipitation strengthening, increasing hardness by 20% (He) and 25% (N₂) relative to the as-deposited condition. Hardness increase contributed to a 23% rise in tensile strength in He-deposits (575 ± 9 MPa) and 58% in N₂-deposits (542 ± 23 MPa). Additionally, profilometry-based indentation plastometry revealed anisotropy in pileup distribution, which was more pronounced in the as-deposited state but significantly reduced after aging, indicating improved structural uniformity. These findings emphasize the importance of residual stress relaxation, defect reduction, and precipitation in achieving superior mechanical properties in cold-sprayed Scalmalloy deposits for structural applications.

This study presents a scratch test-based framework for evaluating interfacial adhesion, inter-splat cohesion, and fracture toughness of cold-sprayed SS316L coatings on SS304 substrates, representing the first such application for this coating system. To systematically investigate the influence of process parameters on microstructure and mechanical performance, coatings were deposited at four traverse speeds (20, 100, 250, and 400 mm/s). Among these, the coating produced at 250 mm/s demonstrated the lowest porosity (0.14%) compared to porosities of 0.2, 2.04, and 2.04% at 20, 100, and 400 mm/s, respectively. Notably, this coating also achieved the highest fracture toughness (28 ± 4 MPa-m^0.5, as determined by Zhang’s model), closely approaching the bulk SS316L value (34 MPa-m^0.5). Superior inter-splat cohesion was evidenced by the smallest projected cone area (0.12 mm²) at the scratch indenter tip, with no splat debonding or cracks observed under progressive loading. Furthermore, exceptional interfacial adhesion was demonstrated, as coatings deposited at 250 and 400 mm/s exhibited no interface failure even at maximum applied loads (50 N). These findings establish scratch testing as a reliable quantitative tool for assessing fracture toughness in cold-sprayed coatings. Additionally, an intermediate traverse speed is identified as optimal for achieving the best combination of fracture toughness, inter-splat cohesion, and interfacial adhesion.

The present study investigates the effect of graphene nanoplatelets (GNPs) on the microstructure and corrosion resistance of WC-CoCr coatings deposited via high-velocity air fuel (HVAF) spraying. The HVAF process effectively mitigated decarburization through its controlled lower combustion temperature. The addition of 1 wt.% and 2 wt.% GNPs markedly improved coating densification by filling nanoscale pores, thereby reducing porosity and achieving a relative density of 99.57% for WC-CoCr + 2G. The high thermal conductivity of GNPs enabled uniform heat dissipation during spraying, leading to a 9.7% reduction in crystallite size, and a 25.6% decrease in lattice strain. Electrochemical studies in 3.5 wt.% NaCl solution revealed a remarkable reduction in the corrosion rate, dropping from 4.27 × 10^–6 mpy for WC-CoCr to 1.71 × 10^–8 mpy for WC-CoCr + 2G, demonstrating an almost 99% improvement. The enhanced corrosion resistance is attributed to GNPs acting as a diffusion barrier against Cl⁻ and Na⁺ ions while simultaneously catalyzing the rapid formation of a protective Cr₂O₃ passivation layer. This novel insight into the functional role of GNPs in tuning microstructure, strain relaxation, and electrochemical stability establishes HVAF-sprayed GNP-reinforced WC-CoCr coatings as a transformative solution for high-performance corrosion protection in aggressive environments.

Thermal barrier coatings (TBCs) represent an effective technical approach for augmenting the high-temperature resistance of turbine blades. The microscopic interfacial characteristics of TBCs are directly influenced by the macroscopic structural configuration and mechanical loading conditions of turbine blades. Elucidating the correlation between macroscopic curvature and interfacial strength evolution in TBCs substantially improves the predictive accuracy of thermal fatigue life estimation. In this work, a stress-driven predictive model for TBCs thermal fatigue life is established through combining phenomenological and S-N curve methods with an oxide layer growth model. The master–slave method is implemented to analyze the influence of macroscopic curvature on the interface stress of TBCs. It is demonstrated that both equivalent stress and maximum shear stress at the interface are found to increase as the curvature of TC-layer decreases, whereas maximum principal stress exhibits limited sensitivity to macroscopic curvature variations. The comparison between predictive outcomes and experimental measurements is revealed to exhibit a 32.89% deviation in thermal fatigue life estimation. Moreover, a significant reduction in coating thermal fatigue life is identified with decrease in macroscopic curvature. These findings are validated through correlation with failure characteristics observed in serviced turbine blade TBCs, thereby substantiating the proposed conclusions. The developed predictive framework is established as a valuable reference for the design of high-performance turbine blade systems incorporating TBCs.

Metallic surfaces exposed to natural or marine water are susceptible to the adhesion of living microorganisms, a process called biofouling. Different thermal spraying processes, especially the high kinetic energy ones, can be used to face the challenges of distinct types of material wear. This work deposited pure Cu coatings using different variations of high-velocity oxy-fuel (HVOF): propane, kerosene, and ethanol fuel, and compared to 304SS and Cu deposited by high-pressure cold spray (CS). The samples were characterized by OM, SEM, XRD. Corrosion properties were measured during electrochemical tests in NaCl solution. Biofouling test conducted with Pseudomonas aeruginosa pathogen was cultured to prepare the challenge suspension and then applied on each replicate for 21 days in a Time-Kill assay. The HVOF-propane splats were less deformed than HVOF-ethanol ones, and the HVOF-kerosene promoted the highest microhardness among the samples due to its higher oxide content. The HVOF-propane coating has the lowest count in the biofilm formation test, followed by the HVOF-ethanol. All HVOF Cu coatings had a better antifouling performance than the 304SS reference.

In this study, the high-temperature oxidation behavior and mechanism of Hastelloy-C22 coatings modified with La₂O₃ by laser cladding were systematically investigated. The microstructural morphology and oxidation product characteristics of the coatings were characterized through various analytical methods, including scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), x-ray diffraction (XRD), and laser confocal microscopy. The results indicate that La₂O₃ particles are primarily distributed along the grain boundaries of the coating, facilitating the entry of a solid solution of Cr, Mo, and Co into the γ-Ni lattice during the cladding process. With increasing La₂O₃ content, the content of the Ni-Cr-Co-Mo phases in the coating also increased. In the temperature range of 700-900 °C, the average thickness of the oxide layer of the coating with 1 wt.% La₂O₃ was reduced by 37%. After the addition of La₂O₃, the coating formed a La₄MoO₉ phase upon high-temperature oxidation. This phase effectively protects the metallic elements within the coating from oxidative attack, such as Ni, Cr, and Fe, resulting in optimal oxidation resistance for the coating. Furthermore, as the oxidation temperature increased, the mass of the C22-xLa₂O₃ coating gradually increased, displaying a parabolic relationship with the duration of oxidation.

To address the challenges of low efficiency and inconsistent quality in repairing carbon fiber-reinforced polymer (CFRP) components, a cold spraying remanufacturing repair process of CFRP was proposed. Using damaged carbon fiber-reinforced polyether ether ketone (CF-PEEK) as the study object, a finite element model of the Laval nozzle and substrate was developed in ANSYS FLUENT to conduct computational fluid dynamics analysis and determine optimal process parameters. Based on the simulation results, cold spray repair experiments were carried out. The performance of the repaired composites was evaluated through tensile strength testing, porosity measurements, and wear resistance testing. The finite element analysis indicated that the optimal experimental parameters were 473K and 1MPa, using repair particles with a size of 75 μm. The tensile strengths of pure polyether ether ketone and CF-PEEK repaired specimens were reached 91.3 and 93.3% of their non-destructive counterparts, respectively. Micro-morphology indicated that the repair layer was well bonded with the substrate, and the porosity and wear resistance were also relatively excellent. These findings demonstrate that cold spraying is a promising on-site repair technology for composite structures. This study provides both theoretical insight and technical guidance for achieving rapid and efficient on-site repair of composites.

During cold spraying, the interaction between the powder carrier gas and the main working gas plays an important role in determining coating quality and deposition efficiency by influencing both gas flow dynamics and particle behavior. However, comparative studies examining the effects of different gas stream designs on gas flow fields and particle acceleration behaviors remain limited. In this study, three key configurations of the two gas streams—coaxial, 45° inclined, and perpendicular—are systematically analyzed through numerical modeling. The configuration of the two gas streams considerably affects the gas temperature distribution and particle acceleration behavior upstream of the spraying gun but exhibits minimal influence on the velocity field downstream and the particle impact area on the substrate. When the two gases are placed at a 45° angle, the preheating effect on the powder carrier gas and particles is optimal. However, this arrangement also leads to the most severe particle backflow, increasing the probability of particle–wall collisions, which in turn increases the risk of nozzle blockage. In comparison, when the gas streams are arranged perpendicular to each other, the particle backflow phenomenon and nozzle clogging risk drastically decrease, and this risk is further minimized when the two gases are coaxial. Therefore, for low-melting-point powders that are prone to nozzle clogging (such as aluminum), coaxial or perpendicular gas arrangements are recommended. For high-melting-point particles that are less likely to clog the nozzle (such as copper), a 45° gas arrangement is preferred to optimize particle impact temperature, thereby improving coating quality. The outcomes present valuable insights into the benefits and limitations of the three distinct arrangements between the powder carrier gas and the main working gas, broadening the understanding of their effects on particle deposition efficiency and coating quality.

The application of thermal spray (TS) coatings on polymers and polymer matrix composite substrates has recently attracted considerable scholarly interest, leading to the publication of numerous review articles that articulate the current advancements in the field. Nonetheless, most of these reviews have primarily concentrated on metallization methodologies, including cold spray (CS) and thin-film deposition techniques. Despite the widespread implementation of CS and metallic coatings, alternative TS methodologies, such as arc, plasma, and combustion-based spraying, along with various coating materials like ceramics, polymers, and composites, are similarly gaining prominence. This review offers a comprehensive analysis of various feedstock materials and TS techniques, with a particular focus on their compatibility with polymer-based substrates. The aim is to accomplish a wide array of augmented material characteristics while accentuating the unique attributes of each TS technique. Detailed discussion is provided on each TS process, including particle–substrate interactions, required preparation, interlayers, coating buildup, and bonding mechanisms. By synthesizing the available literature, this review presents a comprehensive overview of the historical development of TS technologies, outlining major innovative advancements. It seeks to elucidate researchers' contributions to addressing deposition mechanism challenges and to underscore the merits and limitations of each TS methodology. The coatings are analyzed in terms of the properties they impart to the substrate, with a focus on potential applications. Examples of practical applications in various fields, such as thermal protection, biomedical engineering, electrical engineering, and tribology, are presented. Furthermore, the review summarizes the challenges facing the development of these techniques as efficient treatments for P/PMC substrates provide guidelines for future research. Novel application domains are proposed based on the most recent research outcomes. Ultimately, this critique aspires to facilitate the selection of feedstock substances and spraying methodologies, taking into consideration the intended application.