Journal of Thermal Spray Technology最新文献

In this study, a Genetic Algorithm-Enhanced Machine Learning (GAML) model has been established to predict stress variations (σ_ave) and equivalent strain (ε_cr) in porous thermal barrier coatings (TBCs) subjected to diverse thermal loading conditions. The input parameters encompass loading parameters, geometrical characteristics, and porosity features. Remarkable predictive performance was observed, with determination coefficient values of 0.971 for ε_cr and 0.939 for σ_ave, emphasizing a robust correlation between predicted and actual values. The hierarchical nature of the GAML model allows latent patterns and relationships within the data to be effectively unveiled. Moreover, the study illustrated that the relevance of each input parameter undergoes substantial changes with variations in output target values, indicating unique sensitivities of each output to specific input parameters. Specifically, at high stress levels, the weight factors of porosity features became more significant in predicting σ_ave due to their direct influence on stress concentration effects, while thermal loading parameters are more effective in predicting ε_cr. Lastly, through an illustrative example, the model’s utility in facilitating coating design and parameter adjustment for achieving desired mechanical properties was demonstrated.

A silicon carbide/yttrium aluminum garnet (SiC/YAG) composite powder feedstock material developed and patented by NTNU (Norway) in 2012 has been used to produce industrial SiC thermal spray coatings since 2014. This powder is the first of its kind in the thermal spray industry. The commercial powder is produced by the agglomerated and sintered route (A&S), making it suitable mostly for High-Velocity Oxygen Fuel, but it can also be produced by the sintered and crushed (S&C) manufacturing route for Atmospheric Plasma Spray (APS). In this work, a S&C route is proposed using jaw crusher, hammer mill, and ball milling techniques. The resulting powders were then deposited using APS and were compared with the reference A&S powder. The chemistry and the microstructure of the powders and coatings were characterized using electron microscopy, x-ray diffraction, and Vickers microhardness. The S&C powders showed a density higher than the A&S powder and a blocky morphology. The S&C powders had almost no internal porosity and kept the same chemical composition as the A&S version. The coatings obtained with the S&C powders outperformed the A&S coatings, having less porosity, higher hardness, and no secondary phases.

High-performance polymers such as poly(ether ether ketone) (PEEK) are appealing as composite components for a wide variety of industrial and medical applications due to their excellent thermomechanical properties. However, conventional PEEK metallization methods can often lead to poor quality control, low deposition rate, and high cost. Cold spray is a promising potential alternative to produce polymer–metal composites rapidly and inexpensively due to its relatively mild operating conditions and high throughput. In this study, we investigated the deposition characteristics of metal–polymer composite feedstock, composed of PEEK powder and copper flake in varying ratios, onto a PEEK substrate. Copper-PEEK powder blends were prepared by both hand-mixing and cryogenic milling (cryomilling), which predominantly creates composite particles with micron-scale copper domains coating PEEK particle surfaces. This process non-monotonically affects the relative dominance and length scales of the multiple contributing deposition mechanisms present in mixed-material cold spray. In low-pressure cold spray, deposits showed significant changes in deposition efficiency and composition as a result of milling, with improvements in these characteristics most dramatic at lower Cu fractions. Deposits of a cryomilled blend of nominally 30 vol.% copper in PEEK exhibited minimal porosity under scanning electron microscopy, complete retention of powder composition, and the highest deposition efficiency among all samples tested. Notably, neither neat PEEK nor neat Cu meaningfully deposited at the same mild conditions as this 30 vol.% Cu blend, indicating a synergistic departure from linear mixing rules driven by the relative balance of local deposition interactions (e.g., hard–soft, soft–soft, etc.). Intentional powder and process design toward optimizing this balance may facilitate cold spray metallization applications.

This study aims to investigate the impact of substrate preheating on the cracking and wear resistance of laser-clad T-800 alloy coatings on DD5 single-crystal alloy substrates. Two different conditions, namely non-preheated (22 °C) and preheated (300 °C), were employed to deposit T-800 alloy coatings on the surface of DD5 single-crystal alloy using laser cladding technology. The experimental results reveal that substrate preheating at 300 °C reduces the degree of variation in microstructure morphology within each region of the coating. This reduction effectively mitigates the internal stresses caused by the difference in solidification rates of the various parts of the coating, thereby preventing coating cracking. Additionally, the presence of Ni in the DD5 substrate enhances the dilution effect on the coating. Compared to the non-preheated condition, the preheated condition increases the Ni content in the primary Laves phase, secondary spherical Laves phase, and Co-based solid solution of the coating by 6.6%, 7.5%, and 14.8%, respectively, and the Co, Cr, Mo, and Si contents were all reduced. Consequently, this reduces the primary Laves phase and secondary spherical Laves phase precipitation and further inhibits coating cracking. The crack defects within the coating in the non-preheated condition of the substrate weakened its wear resistance. Despite a 13.6% reduction in coating microhardness attributed to preheating of the substrate, the high hardness properties of the T-800 alloy coating were preserved. Moreover, the internal hard Laves phase structure was more diffusely distributed in the softer Co-based solid solution, resulting in improved wear resistance through increased anti-adhesion ability and resistance to hard particles intrusion. Specifically, the preheated coating shows a 14.0% reduction in average coefficient of friction, a 37.9% reduction in mass loss. The wear mechanisms observed in the coatings include abrasive wear, adhesive wear, and oxidative wear.

The main objective of this work is to investigate the microstructure, mechanical and corrosion properties of 304 stainless steel-H13 composites produced using high pressure cold spray process. 304 stainless steel powders with varying amount of H13 tool steel powders (0, 25, 50 and 75 wt.%) were pre-mixed and cold spray deposited using nitrogen process gas to produce metal-metal composites. H13 tool steel addition improved plastic deformation, reduced porosity, increased microhardness, and tensile properties of 304 cold spray coatings. The tensile properties increased with the increase in H13 tool steel content and with post deposition heat treatment. Post deposition heat treatment at 900 °C significantly improved the tensile strengths and ductility of the composite coatings. However, the wear rate and corrosion susceptibility increased with the tool steel addition in the as-deposited condition, but improved when heat treated to 900 °C. The overall results suggest that the addition of H13 in 304 cold sprayed coatings deposited with nitrogen process gas could be used as a cheaper alternative to helium as well as improve both the microstructure and mechanical properties over pure 304 cold spray coatings.

Multi-layered thermal barrier coatings (TBCs) are deposited on gas turbine metallic components to protect them against high temperatures, oxidation, and corrosion. However, TBCs have limited working temperatures and lifetimes due to their material properties. Several approaches are tested to increase TBC topcoats' phase stability and properties. Increasing entropy to stabilize phases is a concept introduced in 2004 and required decreasing the Gibbs free energy. Many high entropy ceramics are developed for structural and functional applications, and different types of high entropy oxides (HEOs) are promising TBC ceramics due to their unique characteristics. HEOs are single-phase solid solutions that contain five or more cations, usually a mixture of transition metals and rare-earth elements. Due to the cocktail effect, the final material has a different behavior from its constituents, making it a viable method to improve the properties of traditional materials. Generally, high entropy materials are characterized by three additional phenomena: sluggish diffusion, severe lattice distortion, and high entropy. A review of possible improvements in the lifetime of TBC topcoats using different HEOs in terms of their composition, properties, and stability is presented here. Different HEOs are then examined, and various thermophysical properties, high-temperature stability, and sintering resistance are discussed.

In the current work, twin-wire arc-sprayed copper coatings are investigated to reduce the spread of pathogenic germs in broiler farming. Compressed air and nitrogen are used as process gasses, while the coating torches are varied. The results demonstrate a reduction of 99% pathogenic load due to the presence of coatings in comparison with the uncoated nickel-chromium-steel. This accounts especially for the bacterial strains E.coli, S.aureus and E.cecorum, which are the predominant bacteria in broiler farming. Moreover, posttreatment processes like cold plasma, tungsten inert gas arc processing and shot peening are investigated to further increase the bactericidal properties and abrasion resistance characteristics of the coatings. Further investigations involve the microstructure and the electrical conductivity of the coatings. In this work, it is demonstrated that copper-coated surfaces have an inhibitory effect on bacterial growth of the three investigated bacterial strains compared to the uncoated bulk nickel-chromium-steel material.

In order to improve the tribological properties of Inconel 718 alloy at elevated temperature, nickel-based composite coatings with in situ TiC and MoSi₂ reinforcement were deposited onto Inconel 718 alloy via laser cladding the complex Hastelloy C276 alloy and Ti₃SiC₂ powder in this study. The influences of the in situ TiC and MoSi₂ reinforcement from the complete decomposition of Ti₃SiC₂ powders on the microstructure, mechanical and tribological properties of prepared coatings were systematically investigated. These coatings exhibited a microstructure consisting of coarse γ-Ni dendrites, slender interdendritic MoSi₂ phases, and TiC ellipsoidal particles. The inclusion of an appropriate amount of in situ fine TiC and MoSi₂ precipitates significantly inhibited the directional growth and coarsening of γ-Ni dendrites, resulting in improved mechanical properties and wear resistance. Among the three types of coatings applied through laser cladding, the Ni-based composite coating with 20 wt.% Ti₃SiC₂ addition demonstrated relatively high hardness (538.4 HV_0.3) and flexural strength (1651.37 MPa), coupled with a lower mean friction coefficient (0.39) and wear rate (3.16 × 10^–5 mm³/N m) at 30 °C. These TiC and MoSi₂ reinforcements proved effective in reducing cutting stress and resisting plastic deformation, thereby enhancing friction coefficients and wear rates across the temperature range from 30 to 400 °C. The prepared coatings also exhibited promising wear resistance at 800 °C, attributed to the formation of protective tribofilm oxidative layers. However, the breakage of the lubricating tribofilms caused obvious wear damage and exacerbated friction coefficients and wear rates at 1000 °C.