bluuebunny/crossref_metadata_2025 huggingface dataset:
Wear and Corrosion Resistant Amorphous / Nanostructured Steel Coatings For Replacement of Electrolytic Hard Chromium
Authors: Branagan D.J. , Marshall M.C. , Meacham B.E. , Aprigliano L.F. , Bayles R. , Lemieux E.J. , Newbauer T. , Martin F.J. , Farmer J.C. , Haslam J.J. , Day S.D.
Published: September 2022

In severe corrosive or abrasive environments, steel is rarely used since the range of properties available, in existing steels, are insufficient, resulting in the prevalent usage of either corrosion resistant materials like nickel based superalloys or abrasion resistant materials like tungsten carbide based hardmetals. Recently, a host of carbide based alloys including WC-Co-Cr, NiCr-Cr3C2, WC-WB-Co etc. have been developed in an attempt to bridge the gap between providing both wear and corrosion protection. Data will be presented showing how a newly developed steel coating, SAM2X5, with an amorphous / nanocomposite structure can bridge the gap between conventional metallic alloys and ceramic hardmetal performance with excellent combinations of properties including corrosion resistance superior to nickel base superalloys in seawater / chloride environments and wear resistance approaching that of tungsten carbide. The unique combination of damage tolerance developed should be especially applicable for the replacement of electrolytic hard chromium coatings.
Nanostructured Photocatalytic Titania Coatings Elaborated by Suspension Plasma Spraying
Authors: Toma F.-L. , Bertrand G. , Lamy S. , Klein D. , Coddet C. , Meunier C.
Published: September 2022

This paper deals with the elaboration of titanium dioxide coatings designed for photocatalytic applications, obtained by suspension plasma spraying (SPS), an alternative of the atmospheric plasma spraying (APS) in which the material feedstock is a suspension of the powder to be sprayed. Two different TiO2 powders were dispersed in distilled water and ethanol and injected in Ar-H2 or Ar-H2-He plasma under atmospheric conditions. SEM and XRD analysis were performed to study the microstructure and surface features of the titania coatings. Photocatalytic efficiency of the elaborated samples was evaluated from the conversion rate of different air pollutants: NOx and SO2. The present results showed that the suspension plasma spraying allows to produce reactive surfaces for the removal of air pollutants that in the same working conditions, present a higher photocatalytic activity compared to that of the initial raw powders.
Preparation of an SOFC LSM/YSZ Composite Cathode by Air Plasma Spraying
Authors: White B.D. , Kesler O. , Ben-Oved N. , Burgess A.
Published: September 2022

A porous composite cathode containing (La0.8Sr0.2)0.98MnO3 (LSM) and yttria stabilized zirconia (YSZ) for use in a solid oxide fuel cell has been produced by air plasma spraying. Deposition was carried out using axial powder injection for increased deposition efficiency and composition control. A plasma composed of argon and nitrogen was used to decrease processing costs and avoid decomposition of the cathode material during deposition. Preliminary investigations focused on determining the range of plasma conditions under which each of the materials could be successfully deposited separately. A set of conditions was thereby determined that were suitable for the deposition of a composite cathode from pre-mixed LSM and YSZ powders. Graphite pore former was added to the powder mixture in order to achieve sufficient porosity in the final coating. A tape cast YSZ electrolyte was used as the substrate for the deposition of the cathode and also as the mechanical support layer in the finished cell. Following deposition of the cathode, an anode was produced by traditional wet ceramic processing techniques. Plasma sprayed cathode was characterized by SEM, EDX, and XRD, and the electrochemical performance of the full fuel cell was evaluated.
Properties of Polymer Coatings Fabricated by Low Temperature High Velocity Air Fuel Spraying
Authors: Yuan Xiaojing , Wang Hangong , Hou Genliang , Zha Bailin
Published: September 2022

The fracture behavior of polymer coatings fabricated by low temperature high velocity air fuel (LTHVAF) spray was investigated. It was shown that the coatings were dense and had a mean bonding strength of 13.5 MPa. During the tensile stress process, the fracture occurred in the interior of the coatings, which indicates that the cohesive strength within coatings is less than the bonding strength between the coatings and substrate. A significant amount of crazing and honeycombed holes existed in the fracture surface. Under a tensile stress, cracks initiated at porous defects in the coatings. Dispersed particles interrupted the crack expansion, and caused a change in direction of crack propagation.
Tailoring of Wire Feedstock and Processing Conditions in High Velocity Combustion Wire Spraying
Authors: Wielage B. , Wank A. , Rupprecht C.
Published: September 2022

Though wire flame spraying is a relatively old thermal spray process, modern equipment permits production of high quality coatings featuring outstanding homogeneity, high density and low roughness due to increased particle velocities as a result of increased combustion gas velocity. Typically spray particles are accelerated to velocities exceeding 250 m/s, if the wires are atomized adequately. In order to make a wide spectrum of coating materials available for wire flame spraying use of cored wires needs to be considered. A high speed camera is used to determine the particle velocity depending on process conditions for massive, grooved cored and tube cored AISI 316L wires. Thereby the influence of the wire design without simultaneous influence by the chemical composition is studied. Additionally nickel based carbide reinforced coatings are sprayed and characterized concerning their microstructure and properties in use.
Simulations of Curvature Evolution Splat-Substrate Systems under Thermal Cycling
Authors: Qu M. , Wu Y. , Gouldstone A.
Published: September 2022

The mechanical behavior of single splats on substrates can provide insight into a number of critical coating aspects, including stress evolution, inelastic behavior, and adhesion. Single splat studies provide a theoretically sound base for the understanding of properties, as they are essentially thin film structures on substrates – a geometrically simple arrangement. However, the experimental measurement of splat properties is non-trivial. Previous work has shown that residual stresses and hardness of splats can be measured successfully using X-ray diffraction and nano-indentation, respectively. Here we present the development of a new technique for the determination of in-plane splat properties, including modulus and flow stress, as well as splat-substrate adhesion. This method is based on the widely-used substrate curvature technique, and adaptations of the Stoney formula for electronic thin films. Critical aspects of the continuum-based analysis, including the effects of splat geometry and/or partial debonding, are discussed.
Optical Coherence Tomography for the Inspection of Plasma-Sprayed Ceramic Coatings
Authors: Veilleux J. , Boulos M. , Moreau C. , Lévesque D. , Dufour M.
Published: September 2022

Optical coherence tomography (OCT) is evaluated as a promising technique for microstructure characterization of plasma-sprayed ceramic coatings. OCT combines the principles of low coherence interferometry and optical heterodyne detection to obtain both a high sensitivity to weakly backscattered light and a high axial resolution. It can be used to accurately locate interfaces where the refractive index changes abruptly within translucent materials. In the present work, OCT cross-sectional images of thin yttria-stabilized zirconia (YSZ) coatings are considered. The interferograms forming the images are analyzed individually to successfully gather information related to light penetration depth inside coatings. The interferogram analysis allows the evaluation of the refractive index of the YSZ non-transformable tetragonal phase.
Evaluation of Fatigue Properties of Various Thermal Spray Coatings
Authors: Siegl J. , Adámek J. , Kovářík O. , Dubský J. , Chráska P.
Published: September 2022

Thermal spray is a flexible technique enabling deposition of wide choice of feedstock materials including ceramics, metals or the mixture of both. Various spray technologies are available, such as different types of thermal plasma methods, electric arc based methods, HVOF and other combustion methods. Obviously, the fatigue properties of coated bodies will differ based on the choice of feedstock material and on the spray technology used. Comparison was made of fatigue properties of bodies with Alumina, Ni-5wt%Al and composite coatings produced by gas and water stabilized plasma spray. It has been found, for instance, that Alumina coatings sprayed by water stabilized plasma torch (WSP) had substantially increased fatigue life times of specimens compared to specimens with coatings of the same feedstock deposited by the gas stabilized plasma torch. Measured fatigue data were related to a detailed structural characterization of the tested coatings. Obtained results are discussed with regard to our previous results obtained during fatigue tests of specimens with one-component coatings.
Laser Cladding of Ni-Cr-B-Fe-Al Alloy on a Steel Support
Authors: Levcovici S.M. , Gheorghies C. , Boiciuc S. , Levcovici D.T.
Published: September 2022

In order to increase the wear and corrosion resistance of 0.45% C surface steel layers, a multilayer coating was tested by injection of a powder with 8.9% Cr, 4.5% Fe, 5.1% B, 2.4% Al, 0.6% Cu and all remainder of Ni in the melted bath produced using a CO2 continuous wave laser. To determine the optimal melting regime, the layers obtained by different laser conditions were characterized by macro and microstructure analysis, as well as a phase qualitative analysis by X-ray diffractometry and microhardness analysis.
Laser Post-Treatment of Plasma Sprayed Al2O3-Cr2O3 Coatings
Authors: Dubský J. , Kolman B. , Chráska P. , Jančárek A.
Published: September 2022

Chromia admixture to alumina feedstock is used to block the formation of γ-Al2O3 in plasma sprayed coatings. In this work, a mechanical blend of alumina-chromia powders was used with the water stabilized plasma to make thick coatings. When additional post-treatment by a quasi-continuous laser was applied to the surface, the amount of the corundum phase substantially increased. Careful examination of the treated surface revealed that the individual splats at and near the surface were fully remelted and the structure is formed by a homogeneous phase with no visible splat boundaries. Segregation of Chromium has been detected in the remelted zones, which strongly affects the final properties of coatings. Fast melting and cooling of the ceramic material under certain laser parameters may result in the formation of undesirable cracks between traces of individual passes of the laser beam.
Thermal Barrier Coating Systems for Gas Turbine Engines by Thermal Spray and EBPVD—A Technical and Economic Comparison
Authors: Feuerstein A. , Knapp J. , Taylor T. , Ashary A. , Bolcavage A. , Hitchman N.
Published: September 2022

The most advanced thermal barrier coating (TBC) systems for aircraft engine and power generation hot section components consist of EBPVD applied yttria stabilized zirconia and platinum modified diffusion aluminide bond coating. Thermally-sprayed ceramic and MCrAlY bond coatings, however, are still used extensively for combustors and power generation blades and vanes. This paper highlights the key features of plasma spray and HVOF, diffusion aluminizing and EBPVD coating processes. The coating characteristics of thermally sprayed MCrAlY bondcoat as well as low density and dense vertically cracked (DVC) Zircoat TBC are described. Essential features of a typical EBPVD TBC coating system, consisting of a diffusion aluminide and a columnar TBC, are also presented. The major coating cost elements such as material, equipment and processing are explained for the different technologies, with a performance and cost comparison given for selected examples.
Micro and Nanomanufacturing Technologies – A Case for Using Thermal and Cold Spray Techniques
Authors: Jackson M.J. , Ahmed W.
Published: September 2022

There is a plethora of micro and nanofabrication processes that have been developed over the past ten years for use in the electrical and mechanical industrial sectors. Processes such as optical lithography, x-ray lithography, LiGA, selective laser sintering, laser micromachining, wet and dry plasma etching, casting, molding, etc., are already well established. However, newly emerging processes such as laser nanofabrication, diamond nanogrinding, thermal spray and cold gas dynamic manufacturing, etc., have yet to realize their potential. The future of micro and nanomanufacturing lies in the ability to convert micro and nanofabrication techniques into mass production manufacturing processes where small-scale products can be economically manufactured in a short period of time. This may be achieved by combining micro and nanoscale processes, or by combining ‘top down’ and ‘bottom up’ manufacturing techniques. The development of so-called hybrid manufacturing processes is set to take center stage in the future development of micro and nanomanufacturing processes. This paper will focus on current developments in the field of micro and nanomanufacturing and highlights the importance of processes such as thermal spray and cold gas dynamic manufacturing.
Hypersonic Plasma Particle Deposition – A Hybrid between Plasma Spraying and Vapor Deposition
Authors: Hafiz J. , Mukherjee R. , Wang X. , McMurry P.H. , Heberlein J. V. R. , Girshick S.L.
Published: September 2022

In the hypersonic plasma particle deposition process, vapor phase reactants are injected into a plasma and rapidly quenched in a supersonic nozzle, leading to nucleation of nanosize particles. These particles impact a substrate at high velocity, forming a coating with grain sizes of 10 to 40 nm. As previously reported, coatings of a variety of materials have been obtained, including silicon, silicon carbide, titanium carbide and nitride, and composites of these, all deposited at very high rates. Recent studies have shown that slight modifications of the process can result in nanosize structures consisting of single crystal silicon nanowires covered with nanoparticles. These nanowires are believed to grow in a vapor deposition process, catalyzed by the presence of titanium in the underlying nanoparticle film. However, simultaneously nanoparticles are nucleated in the nozzle and deposited on the nanowires, leading to structures that are the result of a plasma CVD process combined with a nanoparticle spray process. The combination of these two process paths opens new dimensions in nanophase materials processing.
Development of Composite Nano-Coatings by Comprehensive Thermal Plasma Deposition
Authors: Huang H.J. , Li J.Q. , Ma T. , Eguchi K. , Yoshida T.
Published: September 2022

The development of novel thermal barrier coatings (TBCs) by a 300 kW twin hybrid plasma spraying system was conducted as a case study of the integrated and comprehensive thermal plasma deposition technique, namely, the combination of thermal plasma powder spray (TP-PS) and the thermal plasma physical vapor deposition (TP-PVD). Microstructures of the coatings deposited from either vapor or melted droplets were tailored to compose peculiar functional layered Al2O3/YSZ and YSZ/YSZ coatings in the comprehensive deposition processes, aiming to meet the severe requirements of the next-generation TBCs. Even for the vapor deposition, ultrafast deposition rate over 150 µm/min was achieved. These results showed that the comprehensive spraying process has successfully integrated the potentials of different thermal plasma deposition techniques, and the effectiveness and flexibility of this process made it very promising to be applied in future coating industry.
Properties of WC-10Co-4Cr Powders and Coatings Made of Recycled Hard Metal
Authors: Kanerva U. , Kosme K. , Lagerbom J. , Vuoristo P. , Karhumaa T.
Published: September 2022

HVOF sprayed WC-CoCr coatings are used to in wear and corrosion applications. Commercially available hard metal powders for HVOF spraying are normally manufactured from virgin raw materials. In the present work, the possibility to manufacture WC-CoCr spray powder with excellent properties and quality from recycled cemented carbide tools and tool bits was studied. The powders were manufactured from hard metal scrap by a series of processing steps. The powders were sprayed by using the HVOF process. The properties of the powders and coatings were studied and compared to those of commercially available state-of-the-art WC-CoCr powders and coatings with the same nominal composition. Experimental powders worked well during spraying and the quality of the coatings was equal or even better than that of the reference coatings. Equal or even better corrosion properties compared to reference coatings were obtained with the new spray powder manufactured from recycled hard metal.
Life Cycle Assessment (LCA) of Thermal-Sprayed and Chromium Electroplated Coatings
Authors: Montavon G. , Vardelle A. , Krishnan N. , Ulloa P. , Costil S. , Liao H.
Published: September 2022

Electroplated chromium improves corrosion resistance while providing resistance to wear, fatigue and impact. However, hard chromium plating uses chromic acid, which releases fumes containing carcinogenic chromium +6 ions into air during the process. Therefore, numerous efforts have been carried out worldwide in the last decade to develop alternatives and several applications and processes were validated, among which trivalent chromium plating, electroless nickel and nickel alloy coatings, micro-welding, PVD, CVD, and thermal spraying. Nevertheless, these finishing processes have impacts on human health, ecosystems and resources. In this work, a Life-cycle assessment (LCA) methodology based on Eco-indicators 99 was used to compare the environmental impacts and benefits of thermal spraying (including APS- and HVOF-sprayed WC-Co coatings and TWEA- and APS-sprayed hard steel coatings) to conventional chromium plating.
Latest Technology for Commercially Available Cold Spray Systems
Authors: Richter P. , Hoell H.
Published: September 2022

The industrial use of cold spraying started in 2001 with the introduction of the Kinetic 3000 Cold Spray System from CGT. The heater is designed for a 24-hour operation and has proved its reliability in several installations. The powder feeder can run at the high feed rate of the Kinetic 3000 and is easy to operate. The nozzle design changed from a simple double cone-type to the latest MOC shape. The presentation will give an overview of the state-of-the-art technology in cold spraying.
Process Development of Brazed Aluminum Heat Exchanger Using a Kinetic Spraying Process
Authors: Yoon S.H. , Lee C. , Kim H.J.
Published: September 2022

The conventional manufacturing process of the automotive brazed heat exchanger includes complex preparation processes before brazing: aluminum brazing filler alloy is pre-claded on both sides of a fin by an extrusion method, and holed aluminum tubes are coated on both sides with Zn for corrosion protection by a wire arc spraying process. The intent of this study is to simplify the preparation process by kinetic spraying using all of the components, including Al-12%Si (for the brazing filler metal), Zn (for corrosion protection), and KAlF4 (flux powder). Four kinds of blended powder, with and without flux, were evaluated. The bond properties and composition distribution at the braze joint area were evaluated by SEM and an electron probe micro analyzer (EPMA). It was necessary to control the Zn content so that the corrosion resistance and brazeability of the aluminum heat exchanger would not be affected. An optimal kinetic spray condition was obtained, in order to fabricate the heat exchanger in this study. It was observed that the joints of the brazed specimens on each side of the brazing part were sounder than those achieved brazed by the conventional methods. Further, the kinetic sprayed heat exchanger showed acceptable corrosion protection.
Investigation of Spray Conditions and Performances of Cold-sprayed Pure Silicon Anodes for Lithium Secondary Batteries
Authors: Sakaki K. , Shinkai S. , Shimizu Y.
Published: September 2022

Currently, graphite is used for anodes of the lithium ion battery. The higher capacity of a battery with the lithium alloy anode requires the development of a larger theoretical electrochemical capacity than graphite. Silicon is a promising anode material, having a theoretical capacity more than 10 times that of the graphite used in these lithium alloy batteries. There are two common methods of fabricating silicon anodes: direct deposition techniques such as electron beam deposition and sputtering; and slurry coating of silicon particles with a binder. Alternative methods are being investigated. One of such methods is cold spray. In this study, numerical simulation of, and experiments investigating, cold spray conditions and the performances of cold-sprayed silicon anodes are presented. Silicon was cold-sprayed on copper foil substrates using three different starting materials (with particle sizes of 4.65 µm, 6.74 µm and 9.63 µm). First cycle efficiency was about 90%. Charge capacity initially improves with cycling (up to the 10th cycle). This is probably due to better electrolyte soaking during the first several cycles. A decrease in charge capacity is observed upon further cycling.
Pulsed-Cold Gas Dynamic Spraying Process: Development and Capabilities
Authors: Jodoin B. , Richer P. , Bérubé G. , Ajdelsztajn L. , Yandouzi M. , Erdi A.
Published: September 2022

A new process, the Pulsed-Cold Gas Dynamic Spraying process is presented in this work. A description of the process and of the experimental set-up developed at the University of Ottawa Cold Spray Laboratory is presented. It is envisioned that this process could allow for the feedstock particles to be accelerated to high impact velocities and intermediate temperatures, in a non-reacting gas. That way, the intermediate particle impact temperature would lead to a lower critical velocity as compared with CGDS that could be easily reached while preserving the chemical and microstructural composition of the feedstock particles in the coating. Selected examples of the variety of coatings produced with the system are presented, illustrating the potential of the process to deposit various materials as well as its main benefits.
Adhesion of Cold Sprayed Coatings: Effect of Powder, Substrate, and Heat Treatment
Authors: Mäkinen H. , Lagerbom J. , Vuoristo P.
Published: September 2022

In cold spraying, various issues affect the mechanical properties of the coatings. Adhesion strength is usually considered to be the most crucial mechanical property. The aim of this study was to investigate the adhesion strength of cold sprayed copper and nickel chromium alloy coatings. The focus was especially in studying the influence of powders, substrates and heat treatments on adhesion strength. Three different copper and three nickel-20%chromium powders were tested. The substrate materials were carbon steel and copper. Furthermore, effect of substrate pre-treatment to the adhesion strength of the cold sprayed copper coatings was investigated. The influences of the powders and the substrates on the cold sprayed coatings were dependent on the materials. Adhesion strength of the cold sprayed Cu coatings was significantly higher on the Cu substrate than on the steel substrate. Moreover, heat treatment improved the adhesion strengths with increasing annealing temperature.
Effect of Substrate Temperature on the Formation Mechanism of Cold Sprayed Aluminum, Zinc, and Tin Coatings
Authors: Legoux J.G. , Irissou E. , Moreau C.
Published: September 2022

When describing the cold spray process, one of the most widely used concepts is the critical velocity. Current models predicting critical velocities take the temperature of the sprayed particles explicitly into account but not the surface temperature (substrate or already deposited layers) on which the particle impact. This surface temperature is expected to play an important role since the deformation process leading to particle bonding and coating formation takes place both on the particle and the substrate side. The aim of this work is to investigate the effect of the substrate temperature on the coating formation process. Experiments were performed using aluminum, zinc and tin powders as coating materials. These materials have a rather large difference in critical velocities that gives the possibility to cover a broad range of deposition velocity to critical velocity ratio using commercial low pressure cold spray system. The sample surface was heated and the temperature was varied from room temperature to a high fraction of the melting point of the coating material for all three materials. The change in temperature of the substrate during the deposition process was measured by means of a high speed IR camera. The coating formation was investigated as a function of (1) the measured surface temperature of the substrate during deposition, (2) the gun transverse speed and (3) the particle velocity. Both single particle impact samples and thick coatings were produced and characterized. Both the particle-substrate and interparticle bondings were evaluated by SEM and confocal microscopy
Mechanical Characteristics of Al-Co-Ce Coatings Produced by the Cold Spray Process
Authors: Sansoucy E. , Jodoin B. , Kim G.E. , Moran A.L.
Published: September 2022

Gas atomized feedstock particles of an Al-13Co-26Ce alloy system were sprayed using the Cold Spray deposition technique. The microstructures of the coatings produced are examined and the mechanical characteristics, in particular the bending fatigue and the bond strength, of the Al-Co-Ce coatings are reported. The results show that the Al-Co-Ce coating improved the fatigue behavior of AA 2024-T3 specimens when compared to uncoated and Al clad specimens. During the bond strength tests, the bonding agent failed and no delamination of the coating from the substrate occurred. The microstructural features of the feedstock powder were also found in the coatings. The coatings contained amorphous and crystalline phase contents similar to the ones found in the feedstock powder. It is suggested that the increase in the fatigue properties can be attributed to the residual compressive stresses induced in the coatings and to the high adhesion strength of the coatings to the substrates.
Mechanism Underlying Anelastic Properties of Thermal Spray Coating
Authors: Liu Y. , Nakamura T. , Srinivasan V. , Gouldstone A. , Sampath S.
Published: September 2022

The microstructure of thermally sprayed ceramic coatings is characterized by the existence of various pores and microcracks. The porous microstructure makes coating desirable for thermal insulation, but this unique microstructural feature also gives rise to anelastic response under tension and compression loads. Detail investigations of curvature measurements of ceramic coated substrate indicate the coatings to exhibit anelastic behavior composed of nonlinear and hysteresis characteristics. In this paper, the mechanisms of such behaviors were studied from curvature-temperature measurements and finite element analysis through modeling the microstructure of yttria stabilized zirconia (YSZ) coating. Computational models contain numerous randomly distributed pores and microcracks with various sizes, aspect ratios, locations and orientations. The effects of such attributes of pores and microcracks on coating anelastic behavior were studied by simulations of curvature change during thermal cycles.
Modeling Vapor Deposition Assisted by Thermal Plasma
Authors: Cartel S. , Bansard S. , Mariaux G. , Vardelle A. , Vardelle M. , Menuey J.
Published: September 2022

This study deals with a plasma technique that combines two plasma spray torches to produce finely-structured zirconia coatings. Ideally, the deposition process path involves the vaporization of most of the particles injected in the plasma jet and the transport of the vapor to the substrate where it re-condenses. The arrangement of the plasma torches makes it possible to limit the deposition of non-completely evaporated particles onto the substrate. The experimental design of the vapor deposition process has been assisted by experimental characterization of the plasma temperature field and numerical simulations of the two plasma flow interactions and powder vaporization.
Modeling on Deformation Behavior of Al Particles Impacting on Al Substrate and Effect of Surface Oxide Films on Interfacial Bonding in Cold Spraying
Authors: Li W.-Y. , Liao H. , Coddet C. , Li C.-J. , Bang H.-S.
Published: September 2022

In this study, a comprehensive examination of deformation of Al particles impacting on Al substrate was conducted by using the Arbitrary Lagrangian Eulerian (ALE) method to clarify the deposition characteristics of Al powder and effect of surface oxide films in cold spraying. It was found that the deformation behaviour of Al particles is different from that of Cu particles under the same impact conditions owing to its lower density and thus less kinetic energy upon impact. The results indicate that the Al particles need a higher velocity to reach the same compression ratio as that of Cu particles. On the other hand, the numerical results show that the oxide films at particle surfaces influences the bonding condition between the particles and substrate. The inclusions of the crushed oxide films at the interfaces between the depostied particles inhibit the deformation.
Manufacturing Solid Oxide Fuel Cells with an Axial-injection Plasma Spray System
Authors: Tang Z. , Burgess A. , Kesler O. , White B. , Ben-Oved N.
Published: September 2022

Atmospheric plasma spraying has emerged as a cost-effective alternative to traditional sintering processes for solid oxide fuel cell (SOFC) manufacturing. However, the use of plasma spraying for SOFCs presents unique challenges, mainly due to the high porosity required for the electrodes and fully dense coatings required for the electrolytes. By using optimized spray conditions combined with appropriate feedstocks, SOFC electrolytes and electrodes with required composition and microstructure could be deposited with an axial plasma spray system. In this paper, the challenges for manufacturing SOFC anodes, electrolytes, and cathodes are addressed. The effects of plasma parameters and different feedstocks on coating microstructure are discussed, and examples of optimized coating microstructures are given.
Plasma Sprayed Biocompatible Coatings on PEEK Implants
Authors: Beauvais S. , Decaux O.
Published: September 2022

New advanced polymeric biomaterials such as implantable poly(etheretherketone) (PEEK) are changing the face of the implantable medical device industry. Due to its bioactive behavior in vivo, hydroxyapatite (HA) coatings are used to improve the bone growth and to repair around metallic implant. The objective of this work is to study the feasibility of plasma sprayed hydroxyapatite coating on PEEK material. Different PEEK (unfilled and composite) specimens were successfully coated with a 150 µm thick coating. Chemical and crystallographic compositions, adhesions and microstructures of HA coatings on PEEK and on Ti-6Al-4V were compared. The results showed that the structure of HA coatings were appreciably equivalent. Mechanical tests showed that the plasma spraying process did not severely degrade the initial properties of the PEEK substrate.
Preparation, Microstructure and Bioactivity of Plasma-Sprayed TiO2 Coating
Authors: Zhao X. , Chen Z. , Liu X. , Ding C.
Published: September 2022

In this paper, nano-structured TiO2 coatings have been successfully deposited onto titanium alloy substrates by atmospheric plasma spraying technology using optimized plasma parameters. A chemical treatment method was employed to induce bioactivity on the TiO2 surface. The bioactivity of as-sprayed and chemical treated TiO2 coatings were evaluated by investigating the formation of apatite on their surface after they were soaked in simulated body fluids (SBF) for a period of time. Microstructure and the phase composition of the as-sprayed coating and apatite were analyzed by Field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy-dispersive X-ray spectrometry (EDS). The results obtained indicate that as-sprayed TiO2 coating consists of rutile, anatase and suboxide such as Ti3O5. The surface of nano-TiO2 coating is covered by nano particles of about 50nm in size. The bonding strength of TiO2 coating with Ti alloy substrate is as high as 40 MPa. The corrosion resistance performance of nano-coating in SBF is better than that of Ti-6Al-4V alloy. The surface of as-sprayed TiO2 coating can not induce bone-like apatite formation. Chemical treatment, such as acid and alkali, can improve bioactivity of TiO2 coating surface.
Sintering Kinetics of Plasma-Sprayed Zirconia TBCs
Authors: Cipitria A. , Golosnoy I.O. , Clyne T.W.
Published: September 2022

A model of the sintering exhibited by EB-PVD TBCs, based on the principles of free energy minimization, was recently published by Hutchinson et al. In the current paper, this approach is applied to the sintering of plasma-sprayed TBCs and comparisons are made with experimental results. Predictions of through-thickness shrinkage and changing pore surface area are compared with experimental data obtained by dilatometry and BET analysis respectively. The sensitivity of the predictions to initial pore architecture and material properties are assessed. The model can be used to predict the evolution of the contact area between overlying splats. This is in turn related to the through-thickness thermal conductivity, using a previously-developed analytical model.
Nanostructured Ceramic HVOF Coatings for Improved Protection
Authors: Turunen E. , Kanerva U. , Varis T. , Knuuttila J. , Leivo J. , Silvonen J.
Published: September 2022

The potential of the high velocity oxy-fuel (HVOF) thermal spray process to produce coatings with reduced porosity is well known. The ability to produce high density ceramic coatings offers potential in high performance applications in the fields of wear, corrosion resistance and dielectric coatings. It has been, however, demonstrated that benefits from HVOF ceramic coatings can be obtained only if particles are melted enough and good lamella adhesion is produced. Therefore, due to the operational limits of the HVOF process, the process-structure- relationship must be well optimized. One strategy to improve melting of ceramic particles in the relatively low flame temperatures of the HVOF process is to modify particle crystal structure and composition. In this paper, the effects of the powder structure and the composition on coating microstructure and deposition efficiency of the HVOF spray process are studied. The effect of fuel gas, hydrogen vs. propane, was also demonstrated. The studied materials were agglomerated alumina- and titania-based pure and composite powders. Coating properties such as microstructure, hardness, and abrasive wear resistance, were compared to the coating manufactured by using conventional fused and crushed powders.
About the Dependence of the Stabilization of α-Alumina on the Spray Process
Authors: Stahr C.C. , Saaro S. , Berger L.-M. , Dubský J. , Neufuss K.
Published: September 2022

In result of the spray process normally a phase change from α-alumina (corundum) in the feedstock powder to predominantly α-alumina in the coating takes place. This is a well known but often neglected fact in the preparation and use of alumina coatings. This is of special interest since the high usage properties of thermally sprayed alumina coatings are generally derived from sintered alumina ceramics which consist of corundum. It is expected that the prevention of this phase transformation will significantly change the mechanical, electrical and other properties of thermally sprayed alumina coatings. There is controversial information about the possibility of stabilization of α-alumina by additions of chromia in the literature. In this work the stabilization using different spray processes (water stabilized plasma WSP, gas stabilized plasma APS and HVOF) was studied. Mechanical mixtures of alumina and chromia were used, as well as pre-alloyed powders consisting of solid solutions. The coatings were studied by X-ray diffraction and metallographic cross-sections. It was shown that in the case of the mechanically mixed powders the stabilization predominantly depends on the applied spray process. The stabilization by use of the WSP process was confirmed.
Processing and Properties of Advanced Ceramic Abradable Coatings
Authors: Sporer D. , Dorfman M. , Xie L. , Refke A. , Giovannetti I. , Giannozzi M.
Published: September 2022

Abradable seals have been used in jet engines since the late 1960's. Today abradable seals are seeing applications not only in low pressure and high pressure sections of the compressor but also in the high pressure turbine module of jet engines and are gaining ever more attention in industrial gas turbines. Thermal spraying is a relative simple and cost effective means to apply abradable seals. These work by minimizing gaps between rotating and stationary components by allowing the rotating parts to cut into the stationary ones. The types of coatings employed are zirconia based abradable material systems with polymer and, in some cases, hexagonal boron nitride additions. The coatings are designed to work at service temperatures of up to 1200 °C. The objective of this paper is to review various types of commercial and experimental ceramic abradable systems and to assess their performance profiles. The paper will review yttria stabilized zirconia based systems with modified polymer additions and with variable particle sizes of the ceramic phase. Alternative stabilizers and their influence on key coating properties such as thermal shock resistance and abradability will be studied. The paper will also review the influence of plasma spray parameters on coating properties and study the general influence of coating porosity on coating erosion properties and abradability.
Characterization of Adhesion Strength and Residual Stresses of HVOF Sprayed Inconel 718 for Aerospace Repair Applications
Authors: Lyphout C. , Nylén P. , Wigren J.
Published: September 2022

Thermally sprayed Inconel 718 coatings have been deposited by high velocity oxy-fuel (HVOF) spraying on Inconel 718 substrates. The aim of the on-going study is to understand and control the adhesion mechanisms and the residual stress state of the deposit/substrate system, in order to build up thick coatings for maintenance purposes. The coating adhesion strength was evaluated by the standard ASTM C633 tensile test. Coating shear strength was evaluated by the recently developed prEN15340 Shear Test. A modified Layer Removal Method (MLRM) test was carried out to measure residual stresses. The work is a part of an ongoing study for evaluation of relationships between process parameters, residual stress distribution and adhesion strength.
Nanostructured Plasma Sprayed Anodes for Solid Oxide Fuel Cells
Authors: Syed A.A. , Ilhan Z.
Published: September 2022

Nanostructured YSZ+NiO functional layers for SOFC anodes were developed by air plasma spraying. Spray processing was controlled to conserve finely porous and nanostructure of the feedstock in the deposit. The optimized deposits exhibiting high gas permeability, suitable high temperature electronic conductivity, enhanced triple phase boundaries and catalytic activity. The results were compared with conventional NiO+YSZ and Ni-C+YSZ anodes. YSZ electrolyte layer was deposited onto the anodes for electrochemical testing at 800°C in static conditions. Impedance spectroscopy measurements were performed to collect data on the polarization resistance and catalytic behavior of these anode layers. It was established that enlarged reaction zone, provided by high specific surface area of the nanostructured anodes, and finely porous microstructure, led to lower polarizations and enhanced cell performance by more than 60% compared to conventional cells.
Suspension Plasma Spraying of Solid Oxide Fuel Cell Electrolytes
Authors: Waldbillig D. , Kesler O. , Tang Z. , Burgess A.
Published: September 2022

Suspension plasma spraying is a promising modification to traditional plasma spray techniques that may allow plasma sprayed layers with finer microstructures and better porosity control to be produced. The fine microstructures and controlled porosity of these layers, combined with plasma spraying’s ability to produce layers rapidly without requiring a post-deposition heat treatment, makes this an interesting new manufacturing method to produce solid oxide fuel cell (SOFC) active layers. This study uses an axial injection suspension plasma spray system to produce thin, high-density layers of fully stabilized yttria-stabilized zirconia (YSZ) for use as an SOFC electrolyte. Three different aqueous feedstock suspensions with varying solid contents were sprayed, which resulted in coatings with splat thicknesses of approximately 0.5 µm and some intersplat porosity. Total coating thickness increased as the suspension solid content was increased, but suspension flow rates and deposition efficiencies decreased.
Development of Process Maps for Coating Evaluation for High Velocity Plasma
Authors: Molz R. , McCullough R. , Hawley D.
Published: September 2022

Development of coatings using the TriplexPro 200 plasma gun has provided an ideal means for implementing process maps due to the large operating window in terms of particle velocity and particle temperature, as well as the flexibility to use multiple plasma gasses to tailor the coating process. Process mapping enables tracking of coating characteristics, such as hardness, and relating those characteristics to the conditions of the particle that are induced upon the particle by the process parameters. Work performed to date has provided new insights into conditions of the powder particle that result in specific characteristics in the coating. An example is the ability to determine the critical particle energy state that affects coating stress. This work affords an understanding of general theory behind coating characteristics that result from the conditions of the particle. This paper describes the parameter impact in controlling coating stresses and determining optimum particle conditions to produce a desired, or set of desired, coating characteristics.
To Achieve Epitaxy Thermal Spraying by Substrate Melting
Authors: Wei G. , Zhang M. , Zhang W. , Zhang H. , Zhang L. , Sampath S.
Published: September 2022

There have been recent efforts to expand the thermal spraying capabilities for novel corrosion resistant coatings for metal bipolar plates were produced by thermal spraying for proton exchange membrane (PEM) fuel cell applications. Recently, substrate heated by plasma gun or by external laser beam has been proposed to enhance the mechanical and thermal properties of the coatings. Studies were found that with sufficient substrate heating, substrate melting may happen. When droplets solidified on a thin liquid layer on the top of the substrate, conditions will be similar to crystal growth and Epitaxy film growth will be possible. It is therefore possible that using substrate melting as tool to promote epi-layer growth using plasma spraying. Difficulty is how to control the substrate temperature to cause substrate melting during droplet solidification. In this study we will propose a new idea for better temperature control on the substrate. The capability of epitaxy growth using thermal spraying will be investigated. Molybdenum droplets impact on an Aluminum substrate will be studied. A splat formation model including undercooling, nucleation, and non-equilibrium solidification will be used to study the possibility of the substrate melting and grain size distribution.
Melting and Degradation of Nylon-11 Particles During HVOF Combustion Spraying
Authors: Ivosevic M. , Cairncross R.A. , Knight R.
Published: September 2022

Numerical predictions and experimental observations have been correlated to improve the qualitative understanding of the degree of thermal degradation occurring during the HVOF spray deposition of Nylon-11. Particle residence time (<1 ms) in the HVOF jet was insufficient for significant decomposition of the Nylon-11 but was sufficient for noticeable discoloration (yellowing) of the particles of a powder with a mean particle size of 30 µm. Experimental observations showed this to be the case even though numerical predictions indicated that the temperature of a 30 µm diameter particle should be considerably higher than the upper degradation limit of Nylon-11. Initial thermal oxidation of Nylon-11 promotes the formation of carbon-carbon double bonds that strongly absorb in the visible spectrum even at concentrations of parts per million, resulting in discoloration of the Nylon.
Study of Thick Tungsten Coatings Deposited on Various Molybdenum and Copper Substrates
Authors: Kuang Z.Q. , Liu M. , Deng C.G. , Zhou K.S. , Luo G.N.
Published: September 2022

Thick pure tungsten coatings were deposited on molybdenum and copper substrate by vacuum plasma spray for different purpose. The microstructures of tungsten coatings were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effect of preheating temperature of the substrate and introduction of gradient bond layer on the adhesive strength of the coating was investigated. High heat load was tested by high power electron beam bombardment only for tungsten coating on copper. All the results show that the properties of tungsten coating were strongly influenced by different processes, and the density of the coatings is close to 95% of theory density.
Tribological and Corrosion Behavior of Vacuum Plasma Sprayed Ti-Zr-Ni Quasicrystalline Coatings
Authors: Siegmann S. , Kern P. , Rohr L. , Bandyopadhyay P.P.
Published: September 2022

This investigation deals with a study of the friction, wear and corrosion behavior of vacuum plasma sprayed quasicrystalline (QC) Ti41.5Zr41.5Ni17 coatings. During pin on disc experiments, a change in the mode of wear has been found to occur with corresponding changes in normal load and sliding velocity. The low thermal conductivity of quasicrystals and its brittleness play a vital role in determining the friction and wear behavior of such materials. When these coatings are subjected to rubbing for a longer period of time, wear occurs by subsurface crack propagation and subsequent delamination within the coated layer. By comparing the QC to its polycrystalline counterpart during potentiodynamic measurements according to ASTM G 31, higher currents were found over the whole range of potentials for QC when immersed in 1MHCl solution.
Effect of Particle Size Range on Thermally Grown Oxide Scale Formation on Vacuum Plasma Sprayed CoNi- and CoCrAIY Coatings
Authors: Seo D. , Ogawa K. , Shoji T. , Murata S.
Published: September 2022

The effect of particle size range on oxidation behavior was investigated according to exposure time in isothermal oxidation condition. Emphasis was placed upon oxygen content, porosity, and oxide scale formation. Commercially available CoNi- and CoCrAlY powders of several different particle size ranges were vacuum-plasma sprayed on a nickel alloy substrate. The results show that the isothermal degradation of coatings is considerably influenced by the particle size distribution. It can be clearly observed that a remarkable increase in the oxygen content in the as-sprayed coating occurred with a decrease in the mean particle size. But after thermal exposure, the difference of the oxygen contents between the smaller and larger particle coatings is decreased. The distribution of particle size plays the important role of porosity than only the mean particle size. The powder which has the widest range and sample variance leads to make good porosity inside coatings during the deposition process.