Subjects -> PHYSICS (Total: 857 journals)
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THERMODYNAMICS (30 journals)

Showing 1 - 28 of 28 Journals sorted alphabetically
Advances in Heat Transfer     Full-text available via subscription   (Followers: 27)
Applied Thermal Engineering     Hybrid Journal   (Followers: 38)
Araucaria. Revista Iberoamericana de Filosofía, Política y Humanidades     Open Access  
Archives of Thermodynamics     Open Access   (Followers: 11)
Chemical Thermodynamics and Thermal Analysis     Open Access   (Followers: 3)
Condensed Matter Physics     Open Access   (Followers: 2)
Diffusion Foundations     Full-text available via subscription   (Followers: 4)
European Journal of Mechanics - B/Fluids     Hybrid Journal   (Followers: 5)
Experimental Heat Transfer     Hybrid Journal   (Followers: 18)
Experimental Thermal and Fluid Science     Hybrid Journal   (Followers: 35)
Fluids     Open Access  
Heat and Mass Transfer     Hybrid Journal   (Followers: 28)
Heat Transfer Engineering     Hybrid Journal   (Followers: 38)
High Temperature     Hybrid Journal   (Followers: 2)
HTM Journal of Heat Treatment and Materials     Full-text available via subscription   (Followers: 3)
International Journal of Thermodynamics     Open Access   (Followers: 14)
International Journal of Thermophysics     Hybrid Journal   (Followers: 7)
Journal of Chemical Thermodynamics     Hybrid Journal   (Followers: 8)
Journal of Low Temperature Physics     Hybrid Journal   (Followers: 6)
Journal of Non-Newtonian Fluid Mechanics     Hybrid Journal   (Followers: 14)
Journal of Thermal Science     Hybrid Journal   (Followers: 22)
Journal of Thermal Spray Technology     Hybrid Journal   (Followers: 5)
Journal of Thermodynamics     Open Access   (Followers: 9)
Journal of Thermophysics and Heat Transfer     Hybrid Journal   (Followers: 95)
Low Temperature Physics     Hybrid Journal   (Followers: 6)
Metal Science and Heat Treatment     Hybrid Journal   (Followers: 36)
Quantitative InfraRed Thermography Journal     Hybrid Journal  
Thermophysics and Aeromechanics     Hybrid Journal   (Followers: 6)
Similar Journals
Journal Cover
Journal of Thermal Spray Technology
Journal Prestige (SJR): 0.688
Citation Impact (citeScore): 2
Number of Followers: 5  
 
  Hybrid Journal Hybrid journal (It can contain Open Access articles)
ISSN (Print) 1544-1016 - ISSN (Online) 1059-9630
Published by Springer-Verlag Homepage  [2467 journals]
  • Correction to: Wetting Behavior and Functionality Restoration of
           Cold-Sprayed Aluminum-Quasicrystalline Composite Coatings

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      PubDate: 2023-01-26
       
  • Effect of Surface Micro-Texturing on the Tribological Properties of
           TiB-TiC/Co-Based Coatings by Laser Cladding

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      Abstract: Abstract TiB-TiC/Co-based coatings with different surface micro-texturing were prepared on the sliding bearing by laser cladding and fiber pulse laser under the help of E-RSC-100 rotary workbench. The effect of different shape surface micro-texturing on the tribological properties of the Co-based coatings was systematically investigated. The results showed that the constituent phases of the coatings were not changed after surface micro-texturing. With the increase in the rotation speed and loading, the friction coefficient of the coatings with different shape surface micro-texturing was all reduced. The friction coefficient of the coatings with triangular surface micro-texturing was the smallest and followed by the circular and square surface micro-texturing. The microhardness of the coatings was not changed after surface micro-texturing. Compared with the coatings without surface micro-texturing, the mass loss of the coatings with surface micro-texturing was all reduced, and the mass loss of the coatings with the square, circular and triangular surface micro-texturing was reduced by 7.6, 21.7 and 31.5%, respectively. The wear mechanism of the coatings without and with surface micro-texturing was the typical abrasive wear and combined effect of the adhesive wear and the abrasive wear, respectively.
      PubDate: 2023-01-26
       
  • Exploring Miniaturized HVOF Systems for the Deposition of Ti-6Al-4V

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      Abstract: Abstract The exceptional properties of Ti-6Al-4V of high strength, lightweight, corrosion resistance and machinability make it one of the most widely used alloys in in the aerospace industry. Significant efforts are underway to establish powder bed additive manufacturing technologies for Ti-6Al-4V. There are also increasing attempts to use thermal and cold spray to build near-net-shaped parts with buildup rates orders of magnitude higher than powder bed. Thermal spraying, such as HVOF, can oxidize and degrade the alloy due to the high processing temperature. Lowering the flame temperature through inert gas addition in full-size HVOF systems is a possible approach to retain solid-state deposition of the feedstock particles, thereby limiting oxidation and detrimental α-case formation, while providing sufficient heat input for particle softening and plastic deformation at impact. Novel miniaturized HVOF systems, with spray jets of only a few millimeters in width, may further offer the possibility to improve the spatial resolution of the buildup for near-net shape forming. The process parameter range for solid-state deposition of Ti-6A-4V using the liquid-fuelled TAFA Model 825 JPid and the novel hydrogen-fuelled Spraywerx ID-NOVA MK-6 with the addition of nitrogen is shown. Buildups at over 80% deposition efficiency generally yield as-sprayed porosities below 3% and hardness above 200 HV100gf. Attainable microstructures and oxygen content as a function of spray parameters are delineated. Recrystallization and beta-annealing of selected samples lower the residual porosity and can create equiaxed α and intergranular ß-phases. Ultimate tensile strengths of up to 1100 MPa were attained; however, the residual oxygen content of above 0.7% was found to limit β-phase formation, which contributes to a limited elongation to failure.
      PubDate: 2023-01-25
       
  • Microstructural Characterization and Oscillating Sliding Wear
           Investigations of the Aqueous Suspension Sprayed HVOF WC-12Co Coatings

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      Abstract: Abstract Thermally sprayed WC-based hardmetal coatings offer high hardness, good sliding wear and abrasion performance and find large applications in mechanical engineering, valve construction, or offshore applications. WC-Co coatings are mainly produced by high-velocity oxy-fuel spraying (HVOF) from conventional spray feedstock powders. In this work, suspension-HVOF spraying (S-HVOF) was used to produce dense-structured WC-12Co coatings and their microstructural, mechanical and tribological properties were investigated. Significant work was devoted to the development of appropriate aqueous suspensions starting from commercially available fine WC and Co raw powders feedstock. Suspension spraying was carried out using gas-fuelled HVOF TopGun system; for comparison purposes, liquid-fuelled HVOF K2 was employed to spray WC-12Co coatings starting from commercially available spray powder. Microstructural characterization, x-ray diffraction and microhardness of the coatings were evaluated. Oscillating sliding wear tests were conducted against sintered alumina and WC-6Co balls. The sliding wear performances of the WC-Co sprayed coatings were discussed in term of their microstructure, phase composition and coating-ball test couples.
      PubDate: 2023-01-24
       
  • Modeling the Droplet Impact on the Substrate with Surface Preparation in
           Thermal Spraying with SPH

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      Abstract: Abstract The properties of thermally sprayed coatings depend heavily on their microstructure. The microstructure is determined by the dynamics of the impact of the droplets on the substrate surface and the subsequent overlapping of the previously solidified and deformed droplets. Substrate preparation prior to spraying ensures strong adhesion of the coating. This includes roughening and preheating of the substrate surface. In the present study, the smoothed particle hydrodynamics (SPH) method is used to model the Al2O3 impact on a preheated substrate and a roughened substrate surface. A semi-implicit enthalpy–porosity method is applied to simulate the solidification process in the mushy zone. In addition, an implicit correction for SPH simulations is used to improve the performance and stability of the simulation. To investigate the dynamics of heat transfer in the contact between the surface and the droplet, the discretization of the substrate is also taken into account. The results show that the studied substrate surface conditions affect the splat morphology and the solidification process. Subsequently, the simulation of multiple droplets for coating formation is also performed and analyzed.
      PubDate: 2023-01-23
       
  • Novel Method of Predicting Deposition Efficiency in Cold Spray by
           Incorporating Sphericity into a 1D Analytical Model

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      Abstract: Abstract Sensitivity of the cold spray (CS) additive manufacturing process to the variabilities in its process parameters is still being understood. Among the process parameters, particle morphology can have significant implications on drag forces and therefore the particle impact velocity. This in turn affects the deposition efficiency (DE) and the quality of the final products. In this work, a new approach is introduced for computing DE by incorporating particle size and size dependent sphericity distributions into a 1D analytical multiphase gas dynamic model that uses the Haider and Levenspiel drag coefficient that compensates for particle sphericity. To this end, size distributions and size-based sphericity distributions of Al alloy 6061 (Al6061), Ti, and Cu particles were measured using static optical microscope images. The analytical model was then used to estimate size and sphericity dependent velocity curves for helium and nitrogen spray cases for aluminum alloy 6061, and nitrogen spray cases for Ti and Cu powders, which showed that sphericity dependent velocity variations can be on the order of hundreds of meters per second. Following velocity predictions, a DE calculation method was developed by calculating the ratio of particles that exceed a semi-empirical critical velocity. Size informed velocity predictions were compared with predictions for using a spherical particle assumption and particle velocity measurements conducted by particle velocimetry. Ultimately, perfectly spherical particle assumption showed an underestimation of particle velocity while the sphericity data informed velocity predictions were successful in capturing the size versus velocity mean and the velocity range observed in measurements with acceptable accuracy. Furthermore, for nitrogen spray cases, DE was measured experimentally and compared to the newly introduced DE estimation methods, which showed that critical velocity is underestimated for non-spherical particles. Thus, critical velocity equation was calibrated for a more accurate DE estimation for given cases.
      PubDate: 2023-01-23
       
  • Numerical Analysis and Experimental Verification of Melt Pool Evolution
           During Laser Cladding of 40CrNi2Si2MoVA Steel

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      Abstract: Abstract In order to solve the lack of theoretical support in guiding the laser cladding process, this study was performed by conducting the laser cladding of F102 nickel-based alloy powder on the surface of 40CrNi2Si2MoVA steel through a combination of simulation and experiment. A laser cladding three- dimensional finite element model that includes the heat transfer, fluid flow, and material property that varies with temperature is proposed. In this study, the parameters of material that varies with temperature were firstly calculated by using the phase diagram calculation method and to solve the model. Then, the time required to melt the substrate and the depth of the melt pool were observed under different laser powers. The 1800 W optimal laser power was selected considering the powder utilization rate and the property of the cladding layer. The macroevolution of the melt pool during laser cladding was calculated. The melt pool that takes shape is similar to an ellipsoid with the size of 4476 μm × 3293 μm × 1026 μm. The distribution of capillary force and thermal capillary force in the melt pool was obtained to further explore the flow condition of the melt mass by analyzing the surface profile and temperature distribution in the melt pool. The morphology and scale of solidification structure were predicted from the transient thermal distribution (temperature gradient (G), solidification growth rate (R)). After the model calculations and experiments were completed, the experimental results were utilized to verify numerical calculations. The maximum relative error was less than 8% by comparing the numerical cross-sectional morphology with the experimental cross-sectional morphology. The solidification structure and scale obtained from the metallographic experiments were consistent with the predicted results from the numerical calculations. Considering this theoretical basis, the numerical model in this study can be utilized to calculate other materials defined by interpolation function. Hence, the numerical model herein is universally applicable to other substrate materials during laser cladding.
      PubDate: 2023-01-23
       
  • The Effect of Spraying Parameters of the Inner-Diameter High-Velocity
           Air–Fuel (ID-HVAF) Torch on Characteristics of Ti-6Al-4V In-Flight
           Particles and Coatings Formed at Short Spraying Distances

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      Abstract: Abstract High-velocity air–fuel (HVAF) is a combustion process that allows solid-state deposition of metallic particles with minimum oxidation and decomposition. Although HVAF and cold spray are similar in terms of solid-state particle deposition, a slightly higher temperature of HVAF may allow further particle softening and because of it, more particle deformation upon impact. The present study aims to produce dense Ti-6Al-4V coatings by utilizing an inner-diameter (ID) HVAF gun. The ID gun is considered a scaled-down version of the standard HVAF with a narrower jet, beneficial for near-net-shape manufacturing. To explore the potential of the ID gun in the solid-state deposition of Ti-6Al4V, an investigation was made into the effect of spraying parameters (i.e., spraying distance, fuel pressure, feeding rate, traverse speed, and nozzle length) on the characteristics of in-flight particles and the attributes of the as-fabricated coatings such as porosity, phases, and hardness. For studying in-flight particles characteristics, using online diagnostics is challenging due to the exothermic oxidation reaction of fine particles, while larger particles are too cold to be detected from their thermal emission. However, DPV diagnostic system was successfully employed to differentiate the non-emitting solid particles from the burning ones. It was found that increasing air and fuel pressure of the ID-HVAF jet as well as increasing the nozzle length led to an increase in the velocity of the in-flight particles and resulted in improved density and hardness of the as-sprayed samples. However, increasing the spraying distance had a negative effect on the density and hardness of the manufactured coatings.
      PubDate: 2023-01-23
       
  • Microstructure and Thermal Cycling Behavior of Ta2O5 and Y2O3 Co-doped
           ZrO2 Coatings

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      Abstract: Abstract Ta2O5-Y2O3 co-doped ZrO2 (TYSZ) powders were prepared by high-temperature solid-phase synthesis, and a TYSZ coating was prepared by atmospheric plasma spraying (APS). The phase structures, coefficient of thermal expansion (CTE), and thermal conductivity of the TYSZ and YSZ coating were studied. Thermal cycling was performed at 1400 °C to evaluate the feasibility of TYSZ as an optimal ceramic material for next-generation gas-turbine thermal barrier coatings. The results indicate that the sintered agglomerated TYSZ powders are regular solid spheres with uniform particle size and good flow performance, which meet the requirements of the APS. The TYSZ coating had a typical layered structure, and the coating bond strength was 27.5 MPa. In contrast to the stable t phase of the powder, the TYSZ coating has a cubic phase due to oxygen defects caused by oxygen escaping during spraying. After high-temperature heat treatment (>1300 °C), the cubic phase of the TYSZ coating reverted to the t phase. Due to the specially designed substitution defects, the coefficient of thermal expansion of TYSZ is slightly lower than that of YSZ, and the thermal conductivity is much lower than that of the YSZ coating. After 84 cycles, spalling and cracking occurred in the TYSZ coating near the bond coat and ceramic interface. The mismatch in the coefficient of thermal expansion between the TYSZ coating and the substrate appears to be the primary reason for the coating failure.
      PubDate: 2023-01-23
       
  • Replication of Particle Trajectories in the Plasma Jet with Two
           Consecutive Residual Neural Networks

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      Abstract: Abstract Due to the complexity of the multi-arc plasma spraying process in combination with the harsh ambient conditions, i.e., extremely high temperatures and velocities, the use of numerical analysis, such as modern methods from computational fluid dynamics (CFD), is unavoidable to gain a better understanding of the coating process. However, the tradeoff between the accuracy of the increasingly sophisticated CFD models and their computation time has always been a concern. This study presents a novel machine learning approach capable of predicting the temperatures, velocities, and coordinates of the in-flight particles in a plasma jet. To this end, two individual residual neural networks are trained consecutively with CFD simulation data sets, in a way that the deviations between the targets and predictions of the first network are used as additional inputs for the second network. The results for test data not used during the training of the networks reveal that the simulated particle trajectories in the plasma jet can be fully replicated by the developed machine learning approach. This indicates the potential of the approach to replace the CFD simulations of the plasma jet, which reduces the computation time from several hours to a few seconds.
      PubDate: 2023-01-23
       
  • Impact Wear Behavior of HVOF-Sprayed WC-10Co-4Cr Coating on Medium Carbon
           Steel Under Controlled Kinetic Energy

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      Abstract: Abstract A compact WC-10Co-4Cr coating with a thickness of about 210 μm was prepared by HVOF spraying, which is mainly composed of WC, W2C, Co6W6C, Co and W phases. By taking an Si3N4 ball as counterpart, the impact wear behavior of the WC-10Co-4Cr coating and its substrate (medium carbon steel) is systematically studied under the ball-on-flat contact mode. The results show that the increase in impact velocity will significantly change the peak stress, kinetic energy and absorbed energy fraction, while the impact time remains almost unchanged. With the increase in collision cycle, the impact energy absorption of WC-10Co-4Cr coating and medium carbon steel decreased first and then remained stable. In addition, the WC-10Co-4Cr coating has higher microhardness and kinetic energy rebound effect, which inhibits plastic deformation during repeated collision, and the initiation, propagation and connection of microcracks, as well as the crushing and spalling of surface materials. When the impact velocity reaches 150 mm/s, the depth and width of the wear mark, the wear rate and the wear loss of the WC-10Co-4Cr coating are 4.61 and 75.16, 11.96 and 7.51% than those of medium carbon steel, respectively. The dominant wear mechanism of the WC-10Co-4Cr coating is delamination wear and slight oxidation, while the primary wear damage of medium carbon steel is plastic deformation, which is followed by the gradual onset of additional oxidation and fatigue wear.
      PubDate: 2023-01-18
       
  • In Situ Synthesis of Cr2AlC Gradient Coating by Plasma Transferred Arc
           Cladding

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      Abstract: Abstract The high-purity MAX phase coatings with thickness lower than 10 μm are mainly deposited by physical vapor deposition. Still, they typically fail to meet the long-term stability demand of heavy load and high-temperature applications. In the present study, a process for in situ synthesis of Cr2AlC MAX phase coating based on plasma transferred arc cladding directly from pure Cr, Al and Cr3C2 powder has been proposed for the first time. The as-received powders were mixed at a molar ration Cr:Al:C = 2:1.1:1 in a mortar manually for 1800s. To reveal the possible in situ synthesis mechanism, the effects of the plasma gas flux on the phase formation and microstructure evolution of coatings were investigated. The results indicated that a Cr2AlC gradient coating with a 1 mm high-purity Cr2AlC top layer was formed on low-carbon steel by plasma gas flux 0.03 and 0.04 L/s. If plasma gas flux continued to increase to 0.05 L/s, no Cr2AlC MAX phase was observed in the coating. The study proved the possibility of in situ synthesis of Cr2AlC coating by plasma transferred arc cladding and revealed the in situ synthesis mechanism.
      PubDate: 2023-01-18
       
  • Effect of Cathode-Plasma Coupling on Plasma Torch Operation Predicted by a
           3D Two-Temperature Electric Arc Model

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      Abstract: Abstract In a DC plasma spray torch, the plasma-forming gas is the most intensively heated and accelerated at the cathode arc attachment due to the very high electric current density at this location. A proper prediction of the cathode arc attachment is, therefore, essential for understanding the plasma jet formation and cathode operation. However, numerical studies of the cathode arc attachment mostly deal with transferred arcs or conventional plasma torches with tapered cathodes. In this study, a 3D time-dependent two-temperature model of electric arc combined with a cathode sheath model is applied to the commercial cascaded-anode plasma torch SinplexPro fitted with a wide single cathode. The model is used to investigate the effect of the cathode sheath model and bidirectional cathode-plasma coupling on the predicted cathode arc attachment and plasma flow. The model of the plasma-cathode interface takes into account the non-equilibrium space-charge sheath to establish the thermal and electric current balance at the interface. The radial profiles of cathode sheath parameters (voltage drop, electron temperature at the interface, Schottky reduction in the work function) were computed on the surface of the cathode tip and used at the cathode-plasma interface in the model of plasma torch operation. The latter is developed in the open-source CFD software Code_Saturne. It makes it possible to calculate the plasma flow fields inside and outside the plasma torch as well as the enthalpy and electromagnetic fields in the gas phase and electrodes. This study shows that the inclusion of the cathode sheath model in the two-temperature MHD model results in a higher constriction of the cathode arc attachment, more plausible cathode surface temperature distribution, more reliable prediction of the torch voltage and cooling loss, and more consistent thermal balance in the torch.
      PubDate: 2023-01-11
       
  • A Novel Fe-Based Amorphous Powder and Coating with Excellent Wear and
           Corrosion Resistance

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      Abstract: Abstract A novel amorphous powder with the composition Fe43.6Ni17.4Cr9Co6Si1.5B17.5Nb5 was prepared by the high-pressure Ar gas atomization method. The amorphous coating was fabricated on an A32 hull steel substrate by high-velocity oxygen fuel (HVOF), and the wear and corrosion behavior was investigated. The results show that the amorphous coating exhibits a dense and uniform structure, with 0.9% porosity. Compared with the A32 hull steel, the coefficient of friction (COF) and the wear rate of the amorphous coating are steady and low (0.4 and 4.5 ± 2.1 × 10−5 mm3 N−1 m−1) under a 10 N load. The coating wear mechanism is oxidation wear, accompanied by peeling wear. The amorphous coating displays a wide passive region and a low Icorr (artificial seawater solution for 6.378 ± 0.021 × 10−7 A cm−2), indicating that the amorphous coating has excellent corrosion resistance. This work shows that the novel Fe-based amorphous coating possesses excellent corrosion and wear resistance and is a good prospect for industrial and commercial applications.
      PubDate: 2023-01-10
       
  • Numerical Prediction of the Influence of Rub-Induced Thermal Stress on the
           Abradability of CuAl-Polyester Sealing Coating

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      Abstract: Abstract Thermal stress is an important factor affecting the abradability of seal coatings. In this paper, the relationship between rub-induced thermal stress and abradability of CuAl seal coating was studied based on thermal–mechanical coupling finite element method using ABAQUS software and a high-temperature and high-speed abradability test rig. The thermal stress simulation results show that the contact friction coefficient and incursion conditions between blade and coating have an important influence on the rub-induced thermal stress of the coating. The peak stress of the coating surface and the coating–casing interface increased with the increase in the friction coefficient when it was in a range of 0.01-0.3, which increased by 192 and 233%, respectively. The peak stress of the coating surface and the coating–casing interface was the minimum when the blade incursion depth and speed were 100 μm and 500 μm/s, which were 406.23 and 313.71 MPa, respectively. The abradability of CuAl seal coating increased with the decrease of coating feed speed when it was in a range of 10-100 μm/s, and the incursion depth ratio decreased from 12.9 to 8.82%. Combined with the high-temperature hardness and residual thermal stress test results, the release of thermal stress from the porous structure and the reduction of hardness during the scraping process are concluded to be the main reasons for maintaining good abradability of the coating. This work has an important reference value for further study of the influence of thermal stress on abradability.
      PubDate: 2023-01-09
       
  • As-Sprayed Highly Crystalline Yb2Si2O7 Environmental Barrier Coatings
           (EBCs) by Atmospheric Plasma Spray (APS)

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      Abstract: Abstract High amorphous phase formation tendency, a desirable microstructure and phase composition, as well as silicon evaporation, are the key challenges of spraying Yb2Si2O7 environmental barrier coatings. This research addresses these issues by depositing as-sprayed high crystalline Yb2Si2O7 using atmospheric plasma spray without any auxiliary heat-treating during spraying, vacuum chamber, or subsequent furnace heat treatment, leading to considerable cost, time, and energy savings. The Yb2Si2O7 powder was sprayed on SiC substrates with three different plasma powers of 90, 72, and 53 kW. Exceptional high crystallinity levels of up to ~ 91% and deposition efficiency of up to 85% were achieved. The silicon mass evaporation during spraying was controlled with a short stand-off distance of 50 mm, and an optimum fraction of the Yb2SiO5 secondary phase (< 20 wt.%) was evenly distributed in the final deposits. The desirable microstructure, including a dense structure with uniform distribution of small porosities, was observed. The undesirable vertical crack formation and any interconnected discontinuities were prevented. Reducing the plasma power from 90 to 53 kW, while conducive to mitigating the silicon mass loss (up to 4%), was detrimental to the microstructure by increasing the fraction of porosities (up to ~ 15%) and partially melted or unmelted fragments. The gradual decrease of the coating temperature after deposition alleviated microcracking but has an insignificant effect on the crystallinity level. Coatings annealed close to their operating temperature at 1300 °C for 24 h demonstrated sintering and a crack-healing effect, closing the tiny microcracks through the thickness. An improved coating composition was detected after annealing by the transformation of Yb2SiO5 to Yb2Si2O7 (up to ~ 10 wt.%).
      PubDate: 2023-01-06
       
  • Ensemble Methods for APS In-Flight Particle Temperature and Velocity
           Prediction Considering Torch Electrodes Ageing

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      Abstract: Abstract The nonlinear relationship between the input process parameters and in-flight particle characteristics of the atmospheric plasma spray (APS) is of paramount importance for coating properties design and quality. It is also known that the ageing of torch electrodes affects this relationship. In recent years, machine learning algorithms have proven to be able to take into account such complex nonlinear interactions. This work illustrates the application of ensemble methods to predict the in-flight particle temperature and velocity during an APS process considering torch electrodes ageing. Experiments were performed to record simultaneously the input process parameters, the in-flight powder particle characteristics and the electrodes usage time. Random Forest (RF) and Gradient Boosting (GB) were used to rank and select the features for the APS process data recorded as the electrodes aged and the corresponding predictive models were compared. The time series aspect of the multivariate APS in-flight particle characteristics data is explored. Two strategies of time series embedding are considered. The first one simply embeds the attributes and the targets from the previous \(n\) time segments considered without any modification; whereas the second strategy first performs differencing to make the time series stationary before embedding. For the present application, RF is found to be more suitable than GB since RF can predict both the in-flight particle velocity and temperature simultaneously, properly considering the interactions between the two targets. On the other hand, GB can only predict these two targets one at a time. The superior performance of both embedded predictive models and the feature rankings of them suggest that it is better to consider the APS data as time series for the in-flight particle characteristic prediction. In particular, it is demonstrated that it is advantageous to first make the time series stationary using the traditional differencing technique, even when modeling using RF.
      PubDate: 2023-01-06
       
  • Microcrack Morphology in the Thermal Insulation Performance of 8YSZ
           Thermal Barrier Coatings: A Mesoscale Numerical Study

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      Abstract: Abstract The initiation and development of microcracks change the temperature distribution of thermal barrier coatings (TBCs). The effect of such a change on heat insulation performance cannot be ignored. A three-dimensional mesoscopic structure model of random microcracks coupled with a general pore structure was established by using the quartet structure generation set method and the Monte Carlo simulation method. Then, a mesoscale thermal analysis model was constructed on the basis of the lattice Boltzmann method to study the influence of microcracks on the thermal insulation properties, such as temperature field distribution and thermal conductivity, of TBCs, and the evolution law of thermal insulation properties, which guides the preparation and use of TBCs, was obtained. Results showed that the inhomogeneity of the temperature field was aggravated by the initiation, growth, and number of microcracks. The increase in the size and number of random microcracks was beneficial for improving the thermal insulation performance of spherical and columnar coatings, whereas the increase in microcrack size and the relative decrease in microcrack number were beneficial for improving the thermal insulation performance of layered coatings. Microcracks can improve the thermal insulation performance of coatings with different structures, and the thermal conductivities of the layered, spherical, and columnar coatings decreased by 8.71, 11.25, and 13.81 %, respectively.
      PubDate: 2023-01-04
       
  • Wetting Behavior and Functionality Restoration of Cold-Sprayed
           Aluminum-Quasicrystalline Composite Coatings

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      Abstract: Abstract Coating design is an efficient strategy to engineer wettability of surfaces and adjustment of the functionality to the necessities in industrial sectors. The current study reveals the feasibility of functional aluminum/quasicrystalline (Al-QC) composite coatings fabrication by cold spray technology. A commercially available Al-based quasicrystalline powder (Al-Cr-Fe-Cu) was combined with aluminum alloy (Al6061) feedstock materials to make coatings with various compositions. A set of cold spray process parameters was employed to deposit composite coatings with different QC-Al ratios and Al6061 coatings as counterparts. The wettability of the coating surfaces was measured by static water droplet contact angles using a droplet shape analyzer and investigation of the dynamic of water droplet impact by high-speed imaging. Through microstructural studies, the Al-QC composites revealed dense structure, well-integrated and adherent deposits, providing structural reliability and enhanced hydrophobic behavior. In the last step of this work, composite coatings were deposited over eroded cold-sprayed Al6061 and a selected composite to demonstrate the feasibility of repairing the damaged part and function restoring. The results and approach used in this work provide understanding of cold-sprayed Al-QC composite coatings manufacturing and their wetting behavior state for cross-field applications.
      PubDate: 2023-01-04
       
  • Microstructural, Mechanical and Wear Properties of Atmospheric
           Plasma-Sprayed and High-Velocity Oxy-Fuel AlCoCrFeNi Equiatomic
           High-Entropy Alloys (HEAs) Coatings

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      Abstract: Abstract In this investigation, atmospheric plasma spray (APS) and high-velocity oxy-fuel (HVOF) techniques were used to produce AlCoCrFeNi coatings. High-entropy alloys (HEAs), due to their mechanical, chemical, and physical properties are capturing the attention of the international scientific community. Starting feedstock powders were characterized in terms of size, phase, and size, and corrosion test in NaCl, ball on disk, rubber wheel, and jet erosion tests was carried out on the obtained coatings. The results of the tribological investigation show that in the case of APS coatings, corrosion and wear behavior depend on the microstructure phases of the coating, as well as the amount of oxides. In particular, the wear morphology of APS surfaces is characterized by brittle fracture, with the presence of pores, cracks, and grooves. For HVOF coatings, further investigations on process parameters are needed because of the poor adhesion strength between the coating and the substrate. Anyway, the obtained corrosion resistance of HVOF coating is greater than that of the C steel substrate used to benchmark the results, and in addition, it ensures better performances in rubber wheel and jet erosion tests, but its wear resistance in the ball-on-disk test is worse because of the debris remaining in the wear track.
      PubDate: 2023-01-04
       
 
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