bluuebunny/crossref_metadata_2025 huggingface dataset:
Depositing Titanium Alloy Additive Features to Forgings and Extrusions Using the Cold Spray Process
Authors: Blose R.E. , Walker B.H. , Walker R.M. , Froes S.H.
Published: September 2022

Development of new low-cost methods for spray forming Titanium alloys is critical for many industries. Direct fabrication technologies would have an impact on many industries because of the potential for quick manufacture of parts or additive features with minimal waste. For example, in the aerospace industry the buy to fly ratios can vary from 1.5:1 for turbine blades to over 22:1 for structural members. The buy to fly ratio is the mass of material that is require to machine a part compared to the mass of material in the finished part. For compressor and ring sections, the ratio is approximately 12:1. For this family of parts, an analysis by Pratt & Whitney indicated that the buy to fly ratio could be reduced by 41% to 7:1 if cold spray could be implemented to deposit isogrids, structural ribbing, bosses, and flanges reducing the material, machining, and post processing required for the final part. This paper summarizes the results of experiments conducted in Phase I of a National Science Foundation grant to spray form Titanium alloy using the cold spray process. This paper further describes the studies performed to date in Phase II and the techniques used to decrease the porosity of the as-sprayed coating from 18% to between 2% and 5% and the post processing methods employed to further consolidate the coating and restore the as-sprayed material to near wrought properties.
SIMAT Application for Aerospace Corrosion Protection and Structural Repair
Authors: Boro Djordjevic B. , Maev R. Gr.
Published: September 2022

Supersonically Induced Mechanical Alloy Technology (SIMAT™) also known as gas-dynamic spraying is under development for corrosion protection and material repair for aluminum airframe structures. This technology enables material powder consolidation that is not possible using other spray technologies. Similar to cold spray but based on compact spray head with nozzle powder feed, SIMAT™ is a low temperature process and does not create the high-temperature environment that affects both the substrate (especially thermally non-stable substrates) and the deposited coating. The emerging SIMAT™ technology, now in development, has the potential for coating, repairing, joining and rapid prototyping powder based materials. The SIMAT™ method adds new flexibility to powder material deposition producing thin to very thick deposits of various metals and metal-ceramic mixtures based on a cold spray particle kinetic approach inducing impact fusion. Solid particles in the size range of 10 to 100 microns are accelerated into a supersonic stream (ranging from 300 to 1200 m/s) using compressed air. These high velocity cold particles are projected on to a work piece. There is no heat discharge in the spray device itself, thus the powder material retains original characteristics. This spraying technique can generate a wide range of deposited layers with thickness ranging from tens of microns up to as much as centimeters. The process extends beyond the concept of “coatings” and includes the capability for in-situ material build-up and consolidation to three-dimensional structures and joining of the components. The deposition and consolidation can be performed from a range of hybrid powders consisting of metals, alloys, ceramics and glasses. Sample tests demonstrate examples of the process on typical aircraft components for new or restored corrosion protection and demonstrate damage repair for potential service life extension of the aircraft structure.
Numerical Simulation of the Cold Gas Dynamic Spray Process
Authors: Karimi M. , Fartaj A. , Rankin G.W. , Vanderzwet D. , Villafuerte J. , Birtch W.
Published: September 2022

A computational fluid dynamic (CFD) model of the cold gas dynamic spray process is presented. The gas dynamic flow field and particle trajectories within an oval shaped supersonic nozzle as well as in the immediate surroundings of the nozzle exit, before and after the impact with the target plane, are simulated. Predicted nozzle wall pressure values compare well with experiment. In addition, predicted particle velocity results at the nozzle exit are in qualitative agreement with those obtained using a side-scatter laser Doppler anemometer (LDA.) Details of the pattern of particle release into the surroundings are visualized in a convenient manner.
Low Pressure Gas Dynamic Spray: Shear Localization during Particle Shock Consolidation
Authors: Maev R. Gr. , Leshchinsky Ev.
Published: September 2022

Gas Dynamic Spray (GDS) is a high rate, direct material-deposition process that utilizes the kinetic energy of particles sprayed at supersonic velocities to cause bonding through the particle plastic deformation on impact. GDS seems to be similar to the powder shock consolidation process, which is governed by dynamic regimes of granular material deformation under impulse loading. These regimes are characterized by adiabatic shear band (ASB) formation. This paper describes the preliminary analysis of ASB formation during GDS on the basis of a combination of the Johnson-Cook and shock wave consolidation models. The dependence of the ASB width on different parameters, including initial powder porosity, average impact stress, shear strain, initial temperature, and contact time was determined. The ASB width was found to vary in the range of 0.5–15 μm, which reveals the great localization of particle deformation in the GDS process.
Properties of Cold Spray Nickel Based Coatings
Authors: Richer P. , Jodoin B. , Sansoucy E. , Ajdelsztajn L. , Kim G.E.
Published: September 2022

Nickel based alloys used in coating applications have been the focus of many studies, particularly in the aerospace industry. Their inherent corrosion and oxidation resistant properties have made them especially attractive for use as the metallic bond coat found in thermal barrier coating systems. Cold Spray is an emerging coating technology in which fine powder particles are accelerated in a supersonic flow and then deposited onto a substrate by means of plastic deformation. In this study, conventional CoNiCrAlY coatings and nanocrystalline nickel coatings are produced using the Cold Spray deposition technique. The coating quality is evaluated using scanning electron microscopy as well as porosity and microhardness measurements.
Effect of Particle Temperature on the Critical Velocity for Particle Deposition by Kinetic Spraying
Authors: Lee J.H. , Kim J.S. , Shin S.M. , Lee C.H. , Kim H.J.
Published: September 2022

This study evaluated the effects of particle temperature on deposition efficiency and critical velocity in kinetic spraying. A wide range of pressures and preheat temperatures of the process gas were used in these experiments to vary both particle velocity and temperature, and a bronze (Cu-Sn alloy) powder was deposited onto aluminum and bronze substrates. The deposition efficiency of the coatings was measured, and the critical velocity was estimated. The experimental results showed that the critical velocities of the bronze feedstock deposited onto either an aluminum or bronze substrate were different and that the critical velocity was strongly dependent on the particle temperature, which when increased, caused the critical velocity to decrease. Increasing the gas pressure caused an increase in particle velocity, while increases in the gas temperature not only affected the particle velocity but also the particle temperature. In our experiments, the critical velocity decreased by 50 m/s when the process gas temperature increased by 100 °C.
Critical and Maximum Velocities in Kinetic Spraying
Authors: Wu J.W. , Fang H.Y. , Lee C.H. , Yoon S.H. , Kim H.J.
Published: September 2022

Critical velocity has been accepted as a characteristic property of kinetic spraying (or cold gas dynamic spraying), which works by accelerating small solid particles to supersonic velocities and then impacting them onto a substrate. However, there is a lack of information about the impact of individual particles and their deposition behavior over a large range of impact velocities. To probe into the impact behavior of the particles and to elucidate the deposition mechanism, individual particle impaction tests have been carried out. A rebound phenomenon was found to occur at a high impact velocities, in which a large fraction of the particles rebounded. Based on experimental results, a model of a plastic particle impacting onto an un-deformed substrate was developed. The adhesion and rebound energies were calculated to estimate the particle/substrate interactions. A maximum impact velocity was found for particle deposition onto the substrate. The particle deposition behavior was controlled by the adhesion and rebound energies.
Characterization of Microstructure of TiO2 Coating Deposited by Vacuum Cold Spraying
Authors: Fan S.-Q. , Yang G.-J. , Liu G.-J. , Li C.-X. , Li C.-J. , Zhang L.-Z.
Published: September 2022

The control of microstructure of TiO2 coating through preparation methods influences significantly the performance of the coating. In this study, vacuum cold spray process as a new coating technology is employed to deposit nanocrystalline TiO2 coatings on glass and stainless steel substrates. TiO2 deposits were formed using two types of nanocrystalline TiO2 powders having mean particle diameters of 200 nm and 25 nm. The microstructure of the coating was characterized by scanning electron microscopy, x-ray diffraction analysis. The results demonstrate that a thick nanocrystalline TiO2 coating can be deposited by vacuum cold spray process. The coating was stacked of particles in agglomerate of several hundred nanometers. The coating presents a mesoporous microstructure which would be effective for applications in photocatalytic degradation, dye-sensitized solar cell and so on.
Measurement and Numerical Simulation of Particle Velocity in Cold Spraying
Authors: Li W.-Y. , Li C.-J. , Wang H.-T. , Li C.-X.
Published: September 2022

The velocity of cold spray particles was measured by a diagnostic system for thermal spray particles based on thermal radiation. A laser beam was employed to illuminate the cold sprayed particles in cold spraying for obtaining a sufficient radiant energy intensity for detection. The measurement was carried out for Cu particles of different mean particle sizes. The particle velocity was also estimated using the previously developed two-dimensional axisymmetric model. It was found that the measured results agreed well with the calculated ones. The proposed measurement method in this paper is reliable. On the other hand, it is confirmed that the particle acceleration behavior in cold spraying can be accurately predicted through the simulation method developed previously. The optimization of cold spray process can be conducted following the simulation method.
Comparison of the Microstructure of Cold Sprayed and Thermally Sprayed IN718 Coatings
Authors: Marrocco T. , McCartney D.G. , Shipway P.H. , Sturgeon A.J.
Published: September 2022

High-temperature nickel-based superalloys such as 1N718 are widely used in gas turbine components as they remain stable at operating temperatures up to ~750°C. There is now a growing interest in the repair and refurbishment of such components using spray deposition techniques. Although many investigations have been carried out to study the effect of conventional processing on the microstructure and mechanical properties of 1N718, much less attention has been given to the alloy when sprayed to form a coating. The purpose of the present study was to investigate and compare 1N718 deposits produced by HVOF spraying and cold gas spray deposition. Optical microscopy, scanning electron microscopy and X-ray diffraction were employed to examine the microstructural evolution of the coatings and to compare the deposition behaviour of the two different processes. Particular attention was paid to porosity, oxide content and the formation of secondary intermetallic phases. Coating microhardness and bond strength were also measured. Results will be presented and discussed in the context of the different thermal histories of the powder particles in the two processes.
Cold Spray Deposition of Metastable Alloys
Authors: Jodoin B. , Ajdelsztajn L. , Berube G. , Villafuerte J.
Published: September 2022

The proposed work describes recent efforts to develop metastable Al-Fe-V-Si coatings for internal-combustion engine applications with higher mechanical properties at high operating temperatures. To do so, the metastable solid powder alloy was engineered from rapid solidification technique (namely gas atomization). The metastable alloy powder was deposited using the Cold Spray process in order to produce protective coatings on top of existing parts. The critical velocity, above which Cold Spray deposition takes place, was successfully achieved and Al-Fe-V-Si coatings were produced. The microstructure of the feedstock powder was retained in the coatings produced, showing the potential of the Cold Spray process to produce metastable coatings for internal combustion engine applications.
Computational Modeling of Cold Spray Process: Effect of Substrate and Particle Size on Gas-particle Flow
Authors: Zhu Q. , Dolatabadi A.
Published: September 2022

This work involves modeling of cold spray process in order to predict gas flow as well as particle conditions upon impacting on a substrate. Particle normal velocity is found to be the most important factor to improve the deposition efficiency and coating quality. Particle velocity is influenced by the substrate geometry and location. The shape and strength of the bow shock near the substrate of different geometries (such as concave, convex, and flat) are studied, and particle normal velocities impacting on the substrates located at various stand-off distances are calculated. Furthermore, the numerical simulation is repeated with particles of various sizes and different feeding gas (Helium and Nitrogen). The results are compared to obtain the optimum substrate location and the appropriate particle size for each feeding gas.
Physical Bonding of Spray Particles to the Substrate for High Impact Velocity Droplet
Authors: Yang H.
Published: September 2022

The physical bonding of spray particles to the substrate is a main factor which contributes to the high adhesive strength of HVOF WC-Co coatings in addition to the mechanical interlocking effect. The adhesive strength between substrate and coatings deposited with partially melted particles under HVOF spray conditions has a significant contribution from physical bonding compared with conventional thermal spray processes having molten particles with relatively low velocity. The physical bonding results from the high impact velocity of partially-molten droplets during the HVOF spraying process.
Modelling a Plasma Torch for Atmospheric Plasma Spraying (APS): Optimization of Particle Injection Near the Torch Outlet According to the Gas Flow within the Torch
Authors: Marqués J.-L. , Ramachandran K. , Vaßen R. , Stöver D.
Published: September 2022

Understanding the particle injection into the gas flow issuing from an APS torch is necessary to optimize the spraying parameters. In order to solve numerically this task, the distribution of gas velocity and temperature at the torch outlet is required. In this work this is achieved by developing a model which not only delivers the solution for the electrically charged gas flow within the torch, but also includes the thermodynamical condition of minimum entropy production. This additional condition fixes the size of the electric arc inside the torch, whose radius is particularly responsible for the form of the calculated velocity and temperature profiles at the torch nozzle. The velocity and viscosity of the gas flow near the torch outlet mainly control the trajectory of particles injected into the gas flow. For the typical gas mass flow and torch power used in APS, the resulting temperatures at the gas core are slightly above the ionization temperature of the gas species. The radial location of the viscosity maximum corresponding to the ionization temperature is calculated, since this maximum strongly influences the particle trajectory. Finally, the influence of plasma fluctuations on the heat transfer to the injected particles is discussed.
Investigation of Splat Curling up in Thermal Spray Coatings
Authors: Xue M. , Mostaghimi J. , Chandra S.
Published: September 2022

The curling up of splats of molten metal deposited on a cold substrate was investigated both experimentally and numerically. An analytical model based on mismatch of thermal expansion between the splat and substrate was developed to calculate the deformation of the splat after curling up. The curling up angle at the edges of splats was predicted using the analytical model and compared with the experimental measurements. The prediction shows good agreement with the experiments.
Monte Carlo Simulation of Thermal Sprayed Coatings
Authors: Steinke T. , Bäker M.
Published: September 2022

The investigation of the splashing and spreading behaviour of an impacting powder particle during the plasma spraying process is a field of research often performed with the help of simulations. To simulate thermal sprayed coatings at large scale, the Monte Carlo method is a useful technology. In the Monte Carlo model presented in this manuscript, spreading starts from the particle impact point and continues over the coating so that the behaviour at steps or other surface structures can be taken into account. The discretisation of the model is only lateral so that the thickness of the coating perpendicular to the substrate can take arbitrary values. The rules for particle spreading and deposition used in the Monte Carlo model are derived from a fluid dynamics model. For a two-dimensional simulation the Monte Carlo results provides good agreement with the fluid dynamics results.
Application of Multiscale Modeling in the Coating Formation Simulation of APS-PYSZ-TBCs
Authors: Lugscheider E. , Bobzin K. , Nickel R.
Published: September 2022

The process parameters of atmospheric plasma spraying (APS) influence the coating formation and properties of partially yttria stabilized zirconia (PYSZ) thermal barrier coatings (TBCs). Simulations can be used to investigate this dependency and to design the coating process for a targeted production of TBCs. A whole process simulation was realized by modeling the linked sub-processes: plasma torch, plasma free jet, powder particles characteristics and coating formation. The coating formation can be described by model approaches with different physical assumptions and geometric scales. One approach is the simulation of single powder particles hitting the substrate surface. An alternative macroscale FEM-model-approach is applied in the coating formation simulation. A group of particles is pooled in a splash dependent on the pre-calculated particle distribution in front of the substrate. A third modeling approach is applied to calculate effective mechanical and thermodynamical properties of coatings dependent on the experimentally obtained or calculated microstructure of the PYSZ-TBC, which is based on different homogenization methods. The application of three simulation approaches in the whole process simulation of APS is discussed, advantages and disadvantages are elucidated. Results based on simulation and experiments are presented for a variation of process parameters. Missing links in the multiscale approach are detected to make suggestions for future modeling and simulation work.
Modeling Thermal Conductivity of Thermal Spray Coatings: Comparing Predictions to Experiments
Authors: Tan Y. , Longtin J.P. , Sampath S.
Published: September 2022

Thermal conductivity plays a critical role in the thermal transport of thermal sprayed coatings. In this paper, a combined image analysis and finite element method approach is developed to assess thermal conductivity from high-resolution scanning electron microscopy (SEM) images of the coating microstructure. Images are analyzed with a collection of image processing algorithms to reveal the microscopic coating morphology. The processed digital image is used to generate a two-dimensional finite element meshing in which pores, cracks and the bulk coating material are identified. The effective thermal conductivity is then simulated using a commercial finite element code. Results are presented for three coating material systems: yttria stabilized zirconia (YSZ), molybdenum and NiAl, and results are found to be in good agreement with experimental values, obtained using the laser flash method. YSZ coatings are also annealed and the analysis procedure repeated to determine if the technique could accurately assess changes in coating morphology.
Computer Simulation of Particle Velocity in HVO/AF
Authors: Zha Bailin , Wang Hangong
Published: September 2022

Flame and particle velocity mathematical model were constructed according to jet dynamics. Velocity of flame, and WC-17Co and NiCrBSi particles were simulated. Results show that velocity of the flame decreases continuously from supersonic to subsonic with the increasing of spray distance. Velocity of particles distributes in 300~800m/s, which relates to particle diameter, density and flame velocity.
SOFC Interconnector Coating using HVOF Process
Authors: Hwang S.Y. , Kim J.H. , Seong B.G. , Yang H.
Published: September 2022

This paper describes an initial development of oxidation resistant coatings for SOFC (solid oxide fuel cell) interconnectors using LaSrCoFe oxide (LSCF, (La0.6Sr0.4)(Fe0.8Co0.2)O3). The process involved the development of hermetic coatings using a HVOF (high velocity oxy-fuel) spray process, specifically a θ-gun spray process. The X-ray diffraction of the powder and the coating is analyzed at first. To get the hermetic coating, numerous process parameters were chosen using design of experiments (DOE). The hermeticity of the coating was tested using a salt spray test. After these tests, a hermetic LSCF coatings was obtained with virtually no interconnecting pores.
Application of Plasma Sprayed Coatings in a Novel Integrated Composite Seal for SOFCs
Authors: Huang X. , Ridgeway K. , Narasimhan S. , Reifsnider K. , Ma X.
Published: September 2022

Affordable and reliable solid oxide fuel cells (SOFCs) are being widely sought as the next-generation answer to the power needs of many applications throughout the world. Maintaining stable hermetic sealing is critical for SOFC stacks to achieve high efficiency and longevity. The authors have introduced a novel multi-layered composite seal, consisting of thin layers of oxidation resistant alloys, plasma sprayed ceramic, and hermetic filler materials. The seal structure will be directly fabricated onto the surfaces of mating adherends using low-cost manufacturing methods such as atmospheric plasma spray (APS). During stack assembly, sealing can be achieved through a simple heat/pressure-assisted curing process. As an important part of the layered composite seal, a plasma sprayed porous alumina-YSZ (yttria-stabilized zirconia) ceramic coating on Fe-Cr based interconnect material has been developed. The ceramic coating was made from low-cost commercially available powders and deposited by atmospheric plasma spray (APS) method. The coating composition and fabrication procedure were optimized for high mechanical robustness, low electric conductivity. Experimental results based on coated “button” samples have demonstrated good bond strength between the plasma-sprayed ceramic layers and interconnect substrates, excellent thermal shock resistance, good electrical insulation properties, and low permeability. Initial testing result of a composite seal formed with a glass filler has shown a low gas leak rate and good thermo-cycling resistance.
Comparison of the Photocatalytic Behavior of TiO2 Coatings Elaborated by Different Thermal Spraying Processes
Authors: Toma F.L. , Sokolov D. , Bertrand G. , Klein D. , Coddet C. , Meunier C.
Published: September 2022

In this paper a comparative study on the microstructure and photocatalytic performances of titanium dioxide coatings elaborated by various thermal spraying methods (plasma spraying in atmospheric conditions, suspension plasma spraying and high-velocity oxy-fuel spraying) was proposed. Agglomerated spray-dried anatase TiO2 powder was used as feedstock material for spraying. Morphology and microstructural characteristics of the coatings were mainly studied by scanning electron microscopy and X-ray diffraction. The photocatalytic behavior of the TiO2-based surfaces was evaluated from the conversion rate of gaseous nitrogen oxides (NOx). It was found that the crystalline structure strongly depended on the technique of thermal spraying deposition. Moreover, a high amount of anatase was suitable for the photocatalytic degradation of the pollutants. Suspension plasma spraying permitted to retain the original anatase phase and to obtain very reactive TiO2 surfaces for the nitrogen oxides removal.
Thermal Spray Coatings for Tribological Applications in the Automotive Industry
Authors: Barbezat G.
Published: September 2022

New advanced thermal spray technology allows providing wear resistant coatings on the cylinder surface of aluminum or magnesium engines. The obtained special surface topography after the finishing allows to decrease significantly the coefficient of friction and to decrease the fuel consumption of an amount of 2 to 4%. Engine tests on diesel and gasoline engines have confirmed the value of this technology regarding the aspect of energy saving. This coating technology is introduced since 5 years in Europe by the manufacturing of high power diesel and gasoline engines respectively. The combination of different MMC coating materials allows the development of new specific solutions for each type of engine. Coatings with improved corrosion resistance and abrasion resistance were also developed and are available now. A brief overview on other applications of thermal spraying in the automotive industry will be also given. The MMC coating shows interesting perspectives for its use in diesel engines equipped with EGR systems to reduce the wear of the cylinder bores.
Thermal Spray Joining—Soldering and Filling of Aluminum Substrates under Atmospheric Conditions by a Combined Thermal Spray-Fusing Technique
Authors: Bach Fr.-W. , Möhwald K. , Drößler B. , Kolar D.
Published: September 2022

Thermal spraying for joining and filling of aluminum substrates under atmospheric conditions represents an enrichment in soldering technology. In a respective process, rod-, wire- or cored wire type, zinc-aluminum-based spray materials are applied for joining components or area filling of substrate and fused simultaneously. The advantages, in contrast to soldering, result from the direct application of the spray material, in particular also in constraint positions, and an uncomplex processing, which enables a conditioned inline capability and the use as a comparatively simple procedure for construction-site services or repairs. The aluminum substrate surface and spray material passivation, which would prevent a successful fusing, can be effectively suppressed by the use of a flux in the cored wires as well as straight on the substrates or a brushing activation.
Characterization of YSZ SOFC Electrolyte Deposited by Atmospheric Plasma Spraying and Low Pressure Plasma Spraying
Authors: Zhang C. , Liao H. , Li W.-Y. , Coddel C. , Li C.-J. , Li C.-X. , Ning X.-J.
Published: September 2022

Yttria doped zirconia has been widely employed as electrolyte materials for solid oxide fuel cells (SOFCs). Plasma spraying is a cost-effective process to deposit YSZ electrolyte. In this study, the 8 mol % Y2O3 stabilized ZrO2 (YSZ) layer was deposited by low pressure plasma spraying (LPPS) and atmospheric plasma spraying (APS) with fused-crushed and agglomerated powders to examine the effect of spray method and particle size on the electrical conductivity and gas permeability of YSZ coating. The microstructure of YSZ coating was characterized by scanning electron microscopy and X-ray diffraction analysis. The results showed that the gas permeability was significantly influenced by powder structure. The gas permeability of YSZ coating deposited by fused-crushed powder is one order lower in magnitude than that by agglomerated powder. Moreover, the gas permeability of YSZ deposited by LPPS is lower than that of APS YSZ. The electrical conductivity of the deposits through thickness direction was measured by potentiostat/galvanostat based on three-electrode assembly approach. The electrical conductivity of YSZ coating deposited by LPPS with fused-crushed powder of small particle size was 0.043 S × cm-1 at 1000°C, which is about 20% higher than that of APS YSZ with the same powder.
Development of Porous Anode Layers for the Solid Oxide Fuel Cell by Plasma Spraying
Authors: Weckmann H. , Syed A. , Ilhan Z. , Arnold J.
Published: September 2022

This paper focuses on development of the anode layer for SOFCs by plasma spraying. The composite (cermet) anode, developed by thermal spraying, consisted of nickel and YSZ. The effect of different plasma spraying technologies on the micro structural characteristics and the electrochemical behavior of the anode layer were investigated. Coatings were fabricated by spraying nickel-coated graphite or nickel oxide with YSZ using a Triplex II plasma torch under atmospheric conditions as well as a standard F4-torch under atmospheric or soft vacuum conditions. The investigations were directed in order to have an open micro porous structure, higher electrical conductivity and catalytic activity of anode deposits. Porosity was investigated by measuring the gas permeability. SEM and XRD technologies were applied to examine the morphology, microstructure and composition of the layers. Electrical conductivity measurements were carried out to determine ohmic losses within the anode layer. Most promising layers were analyzed by measuring the electrochemical behavior to obtain information about catalytic activity and performance.
A Novel Method for Twin-Wire Arc Metallization of Plastic Surfaces using High- Melting Temperature Materials
Authors: Elmoursi A. , Fuller B. , Patel N. , Van Steenkiste T. , Whitehead D.
Published: September 2022

This paper presents a novel approach to metallize plastic surfaces. The approach has the ability to control the electrical resistance of a metallized surface by selecting the appropriate high-melting temperature metal or alloy to be thermally sprayed. Early stages of this study concluded that twin-wire arc thermal spray of high melting temperature metals do not form continuous adhering coatings on plastic surfaces. In addition, kinetic spray deposition of metals such as copper and tin on plastic surfaces also did not provide continuous uniform metallic coatings except on a few selected plastics such as Ryton and Ultem. Rather, the kinetic sprayed particles become embedded and isolated within the plastic substrate surface when using appropriate spray conditions. By combining the kinetic and thermal spray processes we developed a novel approach to metallize plastics. The kinetic spray process is used to prepare the plastic surface with anchoring sites to later accept thermally sprayed high-melting temperature metals or alloys that provide the metallization.
Coating Bores of Light Metal Crankcases
Authors: Bobzin K. , Lugscheider E. , Ernst F. , Zwick J. , Schlaefer T. , Verpoort C. , Schwenk A. , Schreiber F. , Wenz T. , Cook D. , Kowalsky K. , Conti J.
Published: September 2022

Crank cases of modern car-engines are made in general of light metal alloys, mostly aluminium alloys. Due to the low hardness of these materials, the use of cylinder liners, in general made of grey cast iron is required. The use of cylinder liners also leads to several disadvantages, such as the increase of the engines weight. The aim of this work in the long term is to replace these cylinder liners with a thermally sprayed nano-structured composite coating, characterised by high hardness. Therefore in this study a coating process employing a plasma transferred wire arc unit and a cored wire are used.
Graded Coatings for Light Gas Gun Flyer Plate Applications
Authors: Hall A.C. , Weyant C.M. , Wise J.L. , Hall C.A. , Jones S.C. , Urrea D.A. , Mccloskey J.F. , Cates J.W. , Roemer T.J. , Mayer A.J. , Beatty D.E. , Hirschfeld D.A.
Published: September 2022

Use of graded coatings is a well-known strategy for creating materials with continuously changing physical properties. The stiffness (modulus of elasticity) and density of flyer plates used in light gas gun testing directly influences the shape of the shock wave produced by the flyer plate. Many strategies exist for creating flyer plates that produce variable shock profiles, including stacked foils and powder compaction. We have investigated graded thermal spray coatings as an alternative method for creating flyer plates that produce variable shock profiles. An initial proof of concept demonstration has been completed by air plasma spraying a graded coating of Cu & Al onto a copper substrate. This composite flyer plate was tested in a light gas gun to demonstrate that a non-linear shock profile can be created. The plasma spray strategies used to create a group of similar graded density impactors are discussed. Initial light gas gun testing shows that graded density impactors can be created using thermal spray coatings.
Effects of Ce and Si Addition to CoNiCrAlY Bond-Coat Material on Oxidation Behavior and Bonding Strength of Thermal Barrier Coatings
Authors: Ogawa K. , Ito K. , Shoji T. , Tezuka H. , Kato H.
Published: September 2022

In thermal barrier coating (TBC) system, thermally grown oxide (TGO) forms at the interface between the top-coat and bond-coat during service. Delamination or spallation at the interface can be occurred by the TGO formation and growth. Therefore, Modifications of the bond-coat materials are one means to inhibit the TGO formation and to improve the bonding strength of TBCs. In this study, morphologies of TGO were controlled by using Ce and Si addition to conventional CoNiCrAlY bond-coat material. As a result, when the TBCs with Ce added bond-coat materials were aged at 1373K for 100 hours, morphologies of TGO were changed drastically. It is expected that the morphologies can improve bonding strength of TBCs. We carried out to evaluate the bonding strength by using four-point bending tests. As a result, TBC coated with Ce added bond-coat materials indicated excellent bonding strength.
Nanostructured Partially Stabilized Zirconia as an Interlayer in a Multi Layered Thermal Barrier Coating
Authors: Guru D.N. , Heberlein J.V.R. , Mook W.M. , Gerberich W.W. , Berndt C.C.
Published: September 2022

Stresses developed within a thermal barrier coating (TBC) due to the mismatch in thermal expansion of different coating components can cause coating failure. Nanostructured materials have an increased volume fraction of grain boundaries and this microstructural attribute may allow coatings to relieve the strain in the coating structure thereby improving the effectiveness and the lifetime of the TBC. Multi – layered TBCs were prepared using two techniques; atmospheric pressure plasma spray (APS) using a commercial system, and reduced pressure plasma spray using the Triple Torch Plasma Reactor (TTPR). The coatings were deposited on mullite and on NiCrAlY-coated steel substrates, and consisted of an inter – layer of nano-phase partially stabilized zirconia (n – PSZ) and a layer of conventional partially yttria stabilized zirconia coating (c – YSZ) as the top thermal barrier coat. The coatings were heat treated at various temperatures and the microstructural changes analyzed using scanning electron microscopy (SEM) images. Mechanical properties of the coating were studied using four point bend testing to better understand the effect of the n-PSZ inter-layer on the strain relief mechanisms that may be operative within the TBC.
Microstructure and Oxidation of MCrAlY Coatings Produced by Various Thermal Spray Processes
Authors: Shibata M. , Kuroda S. , Watanabe M. , Murakami H. , Ode M. , Sakamoto Y.
Published: September 2022

To protect various gas turbine components against high temperature in the hot sections of power generation plants and aircraft engines, thermal barrier coatings (TBCs) have been developed and widely used. Conventional TBCs consist of a MCrAlY bond coating for oxidation resistance and a ceramic top coating for thermal insulation. High quality coatings of MCrAlYs have been produced mostly by low pressure plasma spraying but other more economical processes are also used depending on the operating conditions of the component to be coated. In this study, CoNiCrAlY powders were deposited on Inconel 718 substrate with 3 types spraying system, i.e., low pressure plasma spraying, high velocity oxy-fuel spraying, and atmosphere plasma spraying. Specimens were isothermally tested for up to 100 h in air at 1373 K. Mass gain of the coatings was measured. Microstructure of the coating cross sections and the surface oxides were observed with SEM. To identify the crystal structure of the formed oxides, the specimens were analyzed by XRD from the surface.
Factors Affecting the Appearance of Air Plasma Sprayed Thermal Barrier Coatings
Authors: Xie L. , Dorfman M. , Patel A. , Aguilar I.
Published: September 2022

Factors affecting the appearance of 7~8 wt.% yttria stabilized zirconia thermal barrier coatings were investigated. The coating appearance can be separated into two aspects, darkening and coloring. Coating darkening is related to the retaining of off-stoichiometric zirconium oxide (ZrO2-x) or yttrium oxide (Y2O3-x). These off-stoichiometric oxides are stable at temperatures between 2300 °C and 2700 °C. Rapid cooling of these oxides leads to the retaining of them in the as-sprayed coatings. A heat treatment in air at temperatures higher than 500 °C transforms these off-stoichiometric oxides to stoichiometric oxides and therefore eliminates the coating darkening effect. Coloring of TBCs is attributed to the existence of impurity oxides. Coatings made from the ultra high purity powder, Z204NS, do not exhibit coloring phenomenon before or after heat treatment. As-sprayed coatings made from premium purity (M204NS) or regular purity (A204NS-1) powders exhibit metastable coloring effect. A 1-hour heat treatment at 500 °C can eliminate the metastable colors and turn the coating color back to the color of the starting powder.
Tailoring of YSZ Powders to Meet Fixed Process Windows, Parameters, and Properties for Land-Based Turbine Applications
Authors: Ladru F. , Reymann H. , Mensing M. , Zimmermann S. , Fischer J.
Published: September 2022

In a joint development project, TACR GmbH1 and H.C. Starck GmbH2 took an approach to adjust the properties of an agglomerated and sintered YSZ powder to a process setup optimized for a HOSP type powder. Within the OEM approved process parameters, which could be changed within narrow limits only, the particle size distribution of the agglomerated and sintered powder was adjusted to meet process parameters and spray setup. Key parameters for the comparison of coating properties and spray behavior were coating porosity and deposition efficiency (DE).
Microstructure and Properties of Plasma-sprayed Ultrafine Cr2O3 Feedstock Powder and Coating
Authors: Lin F. , Yu Y. , Zeng K. , Ren X. , Song X. , Li Z. , Cui Y.
Published: September 2022

Chromium oxide coatings are used in gas turbine engines in anti-wear applications. Ultrafine YPSZ and WC/Co feedstock powders have already been widely used to prepare the ultrafine structured YPSZ and WC/Co coatings, which exhibited improved mechanical properties when compared to those of conventional coatings. Ultrafine chromium oxide powders, prepared by the method of solution precipitation, can not be directly used as plasma spray feedstock powder, because of its low mass of individual ultrafine particle and not good flowability. In this paper, spray drying and heat treatment are used to reprocess the ultrafine chromium oxide powder. The chromium oxide coating is prepared by plasma spraying. X-ray diffraction (XRD) is used to analyze the phase constituents of the feedstock powder and coatings. Scanning electron microscopy (SEM) is used to observe the morphology and particle size of ultrafine powder feedstock powder as well as to examine the microstructure of the chromium oxide coating. In addition, loose density and flowability of the feedstock powder and hardness and bond strength of the ultrafine chromium oxide coating are measured. Experimental results show that the large agglomerated ultrafine chromium oxide feedstock powder after being reprocessed are spherical, have good flowability and high loose density, which are suitable for plasma spraying. The wear properties and microstructure of the ultrafine chromium oxide coatings are improved when compared to the ones of the conventional coatings.
Ceramic Metastable Powder through Plasma Spraying
Authors: Cano I.G. , Dosta S. , Miguel J.R. , Guilemany J.M.
Published: September 2022

Recent research in the field of nanostructured ceramic materials has underscored the importance of using feedstock powders with metastable phases. During material consolidation the metastable structure evolves into a dual structure where the grain growth stops when the crystallites reach their respective equilibrium grain size. The mutual suppression of the grain growth is a direct consequence of the immiscibility of the two phases in the solid state. Due to their small grain size and uniform structure, the nanocomposites exhibiting very interesting properties, are formed. Metastable structures can be produced using atmospheric plasma spray (APS) technique. The main target of this work has been the synthesis of Al2O3-TiO2 metastable powder through atmospheric plasma spraying (APS) and quenching route. The metastable phases have been produced from micron-sized feedstock powders and the effect of different raw powders have also been evaluated. The metastable phases have been characterised by XRD, SEM and FESEM analysis. The availability of producing nanostructured materials through these metastable phases have been studied. The phase and morphology evolution from this metastable phases to nanostructures has been observed.
Development of Zirconia Coatings by HFPD
Authors: Fagoaga I. , Parco M. , Barykin G. , Vaquero C. , de Juan J.
Published: September 2022

Different YSZ powders have been deposited by the high frequency pulse detonation (HFPD) thermal spray process leading to highly dense and hard coatings in comparison to standard APS zirconia layers. During this development, the gun configuration and the process parameters (gas flows, explosion frequency, spray distance and cinematic conditions) have been optimised to get the best deposition performance. In order to explore the potential of the HFPD system to process YSZ base materials, different type of commercial spray powders (agglomerated, fused & crushed, fully or partially stabilized compositions) and size distributions, have been investigated and the resulting coatings characterized. A qualitative comparison of the coating performance at elevated temperatures is presented and discussed. For this purpose, an experimental set-up was designed. Potential applications of these types of zirconia coatings in advanced thermal barrier coating systems, high temperature wear protection or ionic conductors (sensors and fuel cells) are discussed.
Ceramic Coatings Prepared by Plasma Spraying for Semiconductor Production Equipment
Authors: Kato N. , Mizuno H. , Ibe H. , Kitamura J.
Published: September 2022

Application of plasma sprayed ceramic coatings with a high purity of more than 99.9% has been sharply increasing in semiconductor and liquid-crystal-display (LCD) production equipments for dry etching, sputtering and ashing in the last few years. The size of the equipments becomes larger with increasing Si wafer size and the LCD size that promotes the replacement from conventional techniques, such as alumite film and bulk ceramics, to plasma spray coatings, where the high durability against the plasma erosion (anti-plasma erosion resistance) is required. However, as far as we know, no systematic studies on the plasma-erosion properties are reported. In this work, durability of plasma sprayed ceramic coatings against CF4/O2 plasma are investigated by reactive ion etching (RIE) system and are compared to that of the conventional techniques. The erosion mechanism is also discussed through the micro-structural analysis.
Flame Spraying of Titania and Magnetite
Authors: Morton S.S. , Hirschfeld D.A. , Hall A.C.
Published: September 2022

The effect of process conditions on flame spraying of titania (TiO2) and magnetite (Fe3O4) was investigated. Designed experiments were conducted to determine spraying conditions, specifically total combustible gas flow, stand off distance, and oxygen/acetylene ratio that produce high deposition efficiency (DE) and dense coatings. Along with DE, particle temperature and velocity were determined and correlated with process conditions. Results indicate that for both titania and magnetite, hot and high velocity molten particles result in higher DE and lower porosity coatings. Micrographs of coating cross-sections and surfaces were taken with both field emission scanning electron microscope (FESEM) and optical microscope. X-ray diffraction analysis shows that the titania coating retained its rutile structure while the magnetite coating had small amounts of magnetite (γ-Fe2O3) in addition to magnetite.
Cyclic Oxidation Behaviour of Plasma Sprayed Stellite-6 Coated Ni-Base Superalloys
Authors: Singh H. , Puri D. , Prakash S.
Published: September 2022

Stellite-6 coatings were deposited on two Ni-base superalloys namely Superni 75 and Superni 600 by shrouded plasma spray process and the oxidation behaviour of these coatings has been investigated in air and in aggressive environment of Na2SO4 - 60%V2O5. Accelerated oxidation tests were conducted in a silicon carbide tube furnace under cyclic conditions at an elevated temperature of 900°C for 50 cycles. Each cycle consisted of one hour heating and 20 minutes cooling in air. Thermogravimetric technique was used to approximate the oxidation kinetics. The corrosion scales were characterized by XRD, SEM/EDAX and EPMA analyses. It has been observed that coatings followed the parabolic rate law of oxidation, although minor deviations were observed. Overall weight gain conceived in air was just 51% of that in the aggressive environment in case of coated Superni 75, whereas in case of coated Superni 600, the cumulative weight gain in air was found to be one-third of that in the Na2SO4 -60% V2O5 atmospheres. Further the coating showed very good adherence to both of the substrates during the course of air oxidation, whereas some cracks were observed near the edges of the specimens during the molten salt induced oxidation. XRD analysis revealed the presence of phase like CoO, CoCr2O4 and Cr2O3 in the oxide scales, which are reported to be protective oxides. The XRD results were further supported by SEM/EDAX and EPMA.