bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Polymer Crystallinity on Deposition Efficiency and Porosity in Cold Spray of PEKK
Authors: Kaminskyj M. S. , Schwenger M. S. , Brennan D. A. , Haas F. M. , Stanzione Joseph F. 
Published: September 2022

Abstract
Polymer cold spray has yielded lower deposition efficiency (DE) and quality deposits compared to metal cold spray. The disparity stems from metals being studied far longer than polymers in cold spray; in addition, polymers exhibit richer thermo-mechanical behavior. An experimental study was conducted to examine the effects of polymer feedstock degree of crystallinity (D) on cold sprayed deposits of polyetherketoneketone (PEKK), a thermoplastic used in aerospace and other high-performance applications. As deposition relies on the plastic deformation of the impacting particle, polymers with high D may inhibit deposition, reducing deposit quality and efficiency. This study evaluates three PEKK grades produced using different ratios of terephthalic (T) to isophthalic (I) monomer moieties (T/I = 60/40, 70/30, 80/20). The ratios control D, with higher proportions of T monomers corresponding to higher crystallization rates and degrees of crystallinity. A parametric study was completed to evaluate functional process set points of system carrier gas temperature and powder mass flow rate. Using operational parameters common among the PEKK grades, spray cycles were completed for each material and quantitative responses to variation in crystallinity were evaluated through a suite of analyses. DE of the materials was assessed gravimetrically, deposit porosity was evaluated by scanning electron microscopy, and thermophysical changes to the feedstock during the spray cycle were determined by differential scanning calorimetry. Overall, we found that cold spray processing of powders of lower D formed less porous deposits with a higher DE than more crystalline powders sprayed at the same process conditions. PEKK grades with lower T/I ratios achieved DEs in the range of 60-75%, whereas the most T enriched grade only reached ~10% DE.
Pull-Off Testing and Electrical Conductivity of Sn-Based Metal Powder Mixtures Cold Sprayed on Carbon Fiber Reinforced Polymers
Authors: Liberati A. C. , Che H. , Fallah P. , Yue S. , Vo P. 
Published: September 2022

Abstract
Tin was successfully cold sprayed onto carbon fiber reinforced polymers (CFRPs) in previous studies at McGill University and a “crack-filling” mechanism was described as the mechanism that allowed deposition of the metal onto the composite counterpart. By adding other metal powders (aluminum, copper, zinc), it was possible to improve the deposition efficiency (DE) of the tin on the CFRP, as well as improve the electrical conductivity of the coating (notably with copper). While the effect of mixing powders with tin, and more notably the effect of the secondary component (SC) properties on the deposition improvement, were more thoroughly addressed in following studies, the question of the properties of these coatings remained. With the perspective of providing a metallic coating to a relatively poorly conductive composite substrate, this study aims to explore the electrical conductivity and the coating strength of cold sprayed tin with other SCs onto CFRPs. An extensive study on fractured surfaces highlighted the importance of the CFRP surface finish, and it was observed that the coating strengths improved with decreasing DE of pure tin.
The Characteristics of In-Flight Ti-6Al-4V Particles and the Coatings Formed by the Inner-Diameter High-Velocity Air-Fuel (ID-HVAF) Process
Authors: Khamsepour P. , Oberste-Berghaus J. , Aghasibeig M. , Moreau C. , Dolatabadi A. 
Published: September 2022

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, slightly higher temperature of HVAF may allow further particle softening and in turn 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 process, an investigation was made into the effect of spraying parameters (i.e., spraying distance, fuel pressure, and nozzle length) on the characteristics of in-flight particles and the attributes of the as-fabricated coating such as porosity, oxygen content, and hardness. Using online diagnostics to monitor temperature and velocity of in-flight Ti-6Al-4V particles is challenging due to 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 led to an increase of 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 deposits. It was also observed that the phases of the Ti-6Al-4V deposits were altered by producing vanadium oxide due to the high temperature of the spray jet.
Comparison of Microstructure and Residual Stress of HVOF Double Carbides Coatings Deposited on Magnesium Substrate
Authors: Łatka L. , Jonda E. , Godzierz M. , Górnik M. , Tomiczek A. 
Published: September 2022

Abstract
Cermet double carbide coatings (WC-Cr3C2-Ni) were HVOF sprayed onto magnesium substrate. The variable parameter was spray distance (320, 360 and 400 mm). The microstructure of the coatings has been characterized by means of scanning electron microscopy (SEM) and X-ray diffraction (XRD). Additional, porosity and residual stress have been estimated. Phase composition of WC-Cr3C2-Ni cermet coatings consists of hexagonal WC carbide, as well as the Cr3C2 and Cr7C3 carbides. For the longest spray distance, minor presence of WC6O6 was detected, most likely as an effect of higher spraying distance, leading to partially oxidation of WC at powders particles boundaries. Comparing lattice parameters with model data it should be noted that no significant contribution of stress is present, due to minor changes in WC lattice parameters in comparison to ICDD data. It also should be noted that Cr7C3 carbide in WC-Cr3C2-Ni coating has different lattice parameters than ICDD data what shows its reactive nature. In obtained results it is clearly seen, that residual stress have the lowest values for coating sprayed from the shorter distance. This tendency is visible for both, linear and shear stress. The crystallite sizes are also the smallest for the shorter spray distance. Such fine structure shows a tendency to good redistribute of the thermal stress in the sprayed coating and also on the coating-substrate interface.
Improved Environmental Safety of Pipelines Using Highly Efficient Wire Arc Spraying
Authors: Hohnen T. , Lichtenthäler F. , Stark M. 
Published: September 2022

Abstract
Whenever large amounts of liquids or gases have to be transported over long distances, steel pipelines are used. They supply industry with raw materials, guarantee drinking water supplies to large cities, and convey energy sources around the globe. Despite the most stringent safety regulations, pipelines regularly suffer damage and leaks. Severe environmental pollution occurs when oil or gas pipelines, in particular, are damaged. In the case of both onshore and offshore pipelines, decontaminating the affected areas involves a great deal of time, effort, and cost. Moreover, in most cases the contamination cannot be eliminated completely. There are various reasons for damaged pipelines. Corrosion poses one of the greatest challenges here, and this can be influenced by the pipeline owners. There is a need for safe and reliable corrosion protection, and this is set to grow over the coming years. Based on current market data, between 13 and 18 million tons of line pipe were delivered in the years 2015 to 2020. This corresponds to a pipeline length of approx. 86,000 km per year. The objective of this paper is to illustrate why the corrosion protection currently used fails to work in some cases. It also aims to show how thermal coating can improve corrosion protection and what requirements its technical implementation must fulfil. To this end, line pipe is presented in the next chapter. Common standards and manufacturing processes are introduced. The third chapter outlines current corrosion protection measures. Moreover, weak points are analyzed by looking at damage that has already occurred. The requirements for thermal coating are determined based on this.
Influence of Process Parameters on Overall Costs of Surfaces Coated by Wire-Arc Spraying
Authors: Knoch M.A. , Wolf R. 
Published: September 2022

Abstract
Surface treatments and coatings are widely used to protect components from wear and corrosion. Of all available methods, thermal spraying is arguably the most versatile with regard to coating material and morphology. Surface roughness and porosity can be adjusted in a wide range depending on the requirements. However, as-sprayed coating surfaces inevitably exhibit a certain roughness necessitating post-treatment if a smooth surface is required. The surface roughness of thermal spray coatings is usually determined by the used powder fraction and the particles’ melting degree. Using wires as feedstock material allows for a certain influence on the particle size distribution by adjusting process parameters. In this study, the influence of nozzle geometry and atomizing gas pressure on coating quality, surface roughness and cost-efficient post-treatments of wire-arc sprayed Fe-based alloys with a wide hardness-range is investigated. To allow for easy transfer to real components, the sample geometry is based on real world examples of coatings for new components and repair of worn parts. Using adapted process parameters and air-flow, the surface roughness could be decreased to allow for a less time-consuming post-treatment by grinding. Especially in repair coatings for large area applications requiring a smooth surface finish, significant runtime and cost reductions are feasible.
Potentials of Thermal Spraying Processes in Silane-Doped Inert Gases
Authors: Rodriguez Diaz M. , Szafarska M. , Nicolaus M. , Möhwald K. , Maier H. J. 
Published: September 2022

Abstract
In addition to the proper functional properties, the adhesive strength represents one of the key criteria for industrial use of thermally sprayed coatings. Since conventional thermal spraying processes are almost carried out exclusively in air atmosphere, this leads to the oxidation of the particles and of interfaces within the coatings. As a result, conventional thermally sprayed metallic and metal-ceramic coatings are characterized by heterogeneous microstructures with interlamellar oxide fringes at the interfaces between individual splats and also between the coating and the substrate. This has a decisive influence on the bond strength and on the wear and corrosion protection properties of thermally sprayed coatings. The aim of this study is to present the potentials of thermal spraying processes carried out in a mixture of monosiliane and an inert gas at ambient pressure as an alternative to the known vacuum spraying process in order to prevent oxidation during the coating process. Using the example of arcsprayed coatings, it is demonstrated that the extremely low oxygen partial pressure in the silane-doped medium leads to coatings free of oxide seams with a reduced porosity and substantially enhanced properties.
Analysis and Comparison of In Situ Coating Thickness Measurements Using Two Different Sensing Techniques
Authors: Hudomalj U. , Fallahi Sichani E. , Weiss L. , Nabavi M. , Wegener K. 
Published: September 2022

Abstract
Coating thickness is considered to be one of the most important characteristics of thermally sprayed coatings. Therefore, it has long been the goal to be able to control it. This could be achieved by implementing an online, closed-loop control. A prerequisite for such a control mechanism is a feedback signal of the coating thickness with sufficiently small measurement uncertainty. Optical distance measurement techniques have been demonstrated in the past to produce promising results for such applications. This paper analyses the measurement uncertainty of an optical distance measurement technique based on confocal distance sensors used for in situ coating thickness evaluation. As an alternative, pneumatically actuated length gauges are also used for the in situ measurement. Both techniques are applied during atmospheric plasma spraying of samples in a carousel setup. The two sensing techniques are compared with a reference, destructive coating thickness measurement method. Pros and cons of using different in situ coating thickness measurement techniques for process control applications are discussed.
Optical Diagnostic Tools for Thermal Spray Processes
Authors: Zierhut J. 
Published: September 2022

Abstract
Thermal spray is a widespread technology on the way to large scale production. Driven by industrial importance, companies of all sizes employ this technology, with research mainly driven to improve quality and reduce cost. In order to produce high-quality coatings, efforts have been made to provide on-line process control. To find out which parameters affect coating formation and thus which of these parameters should be monitored high level cost intensive diagnostic systems have to be used. This work introduces selected diagnostic systems for the on-line process control under the condition of serial production: shadow imaging for the particles (PSI), a system to measure particle velocities (PVI) and an integral working system using a qualitatively image algorithm (PFI).
Optimization of Segmented Thermal Barrier Coatings (s-TBC) for High-Temperature Applications
Authors: Yalcinyüz B. A. , Thomas G. , Hentschel Y. , Rupprecht C. , Kamutzki F. , Gurlo A. 
Published: September 2022

Abstract
Hot section components of stationary gas turbines such as turbine blades are coated with thermal barrier coatings (TBCs) to increase the high thermal strain tolerance thereby the improvement of the performance for the gas turbines. TBCs represent high-performance ceramics and are mostly composed of yttria-stabilized zirconia (YSZ) in order to fulfil the function of thermal insulation. The microstructure of conventional TBCs should be porous to decrease heat conduction. Besides porous TBCs, the recently developed vertically segmented thermal barrier coatings (s-TBCs) feature outstanding thermal durability. In this work, process parameter development for atmospheric plasma spraying (APS) of s-TBCs is presented. Within the experiments, relevant process parameters such as powder feed rate, surface speed and pathway strategy have been optimized. The aim of this work is to achieve a combination of low internal residual stress and high adhesive tensile strength for s-TBCs. For the formation of vertical cracks, the heat input into the powder feedstock material and the substrate must be controlled precisely.
Sublayer-Assisted Cold Spray Metallization of Carbon Fiber Reinforced Composites
Authors: Zhang T. , Padyyodi E. , Raoelison R.-N. , Sagot J.-C. 
Published: September 2022

Abstract
In order to investigate the potentials to improve the deposition efficiency and to functionalize the polymer-based substrates, six configurations of microparticles Sn, Zn, Al, Sn+Al2O3, Al+Al2O3, Cu+Al2O3 were cold sprayed on the substrate of Carbon Fiber Reinforced Polymer (CFRP) composites equipped with Cu-based sublayer or Al-based sublayer. The process conditions were kept unchanged. Microanalysis of sublayers and coatings was performed via a Scanning Electronic Microscope (SEM), the deposition mechanisms of different powders couplings on CFRP substrate were then discussed. The results indicated that although the deposition efficiencies were negative, the systems of Zn, Al and Al+Al2O3 perform better among all the configurations. It was found that the addition of alumina led to a lower deposition efficiency (DE), compared to the corresponding pure coatings. For single-component Sn, Zn and Al powders, they all showed an increasing trend of DE when changing the substrate from Cu-based systems to Al-based systems. The aim of this present work is to elaborate the intrinsic causes of erosion issues and to provide a reference value for picking spraying materials and preparing functionalized CFRP substrates. According to the SEM analysis, the insufficient deformation and escape behaviours of spherical copper powders explained for the difficulty of coating formation. It was noticeable that the surfaces of Al-based systems were more uniform than those of Cu-based ones, due to their desirable deformation abilities. Besides, the significant flattened particles, material mixing and melting phenomenon were observed in Al-involved systems, which would definitely contribute to the adhesive bonding between coating and substrate.
Novel Method of Predicting Deposition Efficiency in Cold Spray by Incorporating Sphericity into 1D Numerical Models
Authors: Ozdemir O. C. , Muftu S. 
Published: September 2022

Abstract
In cold spray (CS) additive manufacturing process, micrometer scale particles accelerated through a supersonic nozzle are targeted on a surface with velocities in the rage of 300-1500 m/s in solid state. The impact energy of the particles leads them to deform plastically with high shear energy near the impact interface and adhere to the surface metallurgically, mechanically, and chemically. Using CS, deposition of metals, metal matrix composites, and polymers are achieved with high adhesive/cohesive strength and low porosity. Sensitivity of the CS additive manufacturing process to the variabilities in the process parameters are still being understood. Among the process parameters, particle morphology can have significant implications on drag forces, and therefore, on the particle impact velocity. This in turn affects the deposition efficiency (DE) and the quality of products. In this work, a new approach is introduced for computing DE by incorporating particle sphericity and its variation into one-dimensional numerical models. Size, sphericity, and the variability of size and sphericity of aluminum, copper, titanium, and tantalum particles are measured from static optical microscope images. The data is used for predicting impact velocity, temperature, and DE. The model results are then compared with particle velocity measurements.
As-Sprayed Highly Crystalline Yb2Si2O7 Environmental Barrier Coatings (EBCs) by Atmospheric Plasma Spray (APS)
Authors: Arhami F. , Moreau C. 
Published: September 2022

Abstract
High amorphous phase formation tendency, a desirable microstructure and phase composition and silicon evaporation are the challenges of spraying Yb2Si2O7 environmental barrier coatings (EBCs). This research addresses these issues by depositing as-sprayed high crystalline Yb2Si2O7 using atmospheric plasma spray (APS) without any auxiliary heat-treating during spraying, vacuum chamber, or subsequent furnace heat treatment, leading to considerable cost, time, and energy savings. Yb2Si2O7 powder was sprayed on SiC substrates with three different plasma powers of (90, 72 and 53 kW) and 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-ff distance of 50 mm, and an optimum fraction of Yb2SiO5 secondary phases (&lt;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 kW to 53 kW, while conducive for mitigating the silicon mass loss, was detrimental for microstructure by increasing the fraction of porosities 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 hours 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.%).
High Velocity Flame Spraying (HVOF) of Ceramic – Polymer Composite Filaments
Authors: Sauter M. , Killinger A. , Grebhardt A. , Bonten C. 
Published: September 2022

Abstract
Thermal spraying of fine and ultrafine powders is realised by a novel method based on highly filled filaments as feedstock material for high velocity oxy fuel flame spraying (HVOF). Hereby, the desired coating material is supplied as finely dispersed powder within a polymer filament. Thus, the polymer works only as a transport medium and is fully decomposed when entering the combustion zone instantly releasing the solid dispersion, similar to the liquid dispersion medium in a suspension. It can work as an appropriate method to process fine and ultrafine powders. The solid nature of the dispersion medium poses several benefits compared to liquids, especially from the manufacturing point of view, since the process is geared to a wire flame spraying method. This work focusses on the challenges and benefits of this novel approach. First experimental results of spraying different filaments are presented.
Evaluation of Mechanical Properties of Dense HAD Al2O3 Coatings by Nanoindentation Method
Authors: Sanami K. , Shahien M. , Yumoto A. , Shinoda K. , Akedo J. 
Published: September 2022

Abstract
Hybrid aerosol deposition (HAD) is a new coating method to deposit homogeneous nano-structured ceramic coatings. An accurate evaluation of the fabricated coating properties is required. In this study, α-Al2O3 fine powder was sprayed by HAD. The obtained coatings were dense and uniform with a nanocrystalline structure. An X-ray diffraction measurement revealed that the fabricated HAD Al2O3 coatings mainly consisted of α-Al2O3 phase. The hardness and Young's modulus of the HAD Al2O3 coatings were evaluated by a micro-Vickers method and a nanoindentation method using the Weibull distribution. The hardness of HAD Al2O3 coatings measured by micro-Vickers was ~1400 HV (~15 GPa). The variation of mechanical properties of HAD coatings measured by the nanoindentation method was extremely small compared to those of plasma-sprayed coatings, which also indicates that HAD coatings contain less pores and cracks than plasma-sprayed coatings.