bluuebunny/crossref_metadata_2025 huggingface dataset:
Atmospheric Plasma Spraying of High Melting Temperature Complex Perovskites for TBC Application
Authors: Jarligo M.O. , Mack D.E. , Mauer G. , Vaßen R. , Stöver D.
Published: December 2022

In this investigation, two complex perovskite powders, Ba(MgTa)O and Ta(AlMgT)O, are deposited by atmospheric plasma spraying and evaluated for use as thermal barrier layers. Process parameters are optimized to provide sufficient melting without causing the formation of secondary phases. Deposited coatings are assessed based on composition, morphology, porosity, and thermal cycling lifetime. It is shown that the nature of the starting powders has a significant effect on the lifetime and performance of perovskite-based thermal barrier coatings.
Mullite Coatings Produced by APS and SPS: Effect of Powder Morphology and Spray Processing on Microstructure, Crystallinity, and Mechanical Properties
Authors: Wang Y. , Lima R.S. , Moreau C. , Garcia E. , Guimaraes J. , Miranzo P. , Osendi M.I.
Published: December 2022

This study investigates the influence of powder morphology and spray processes on the microstructure, crystallinity, hardness, and elastic modulus of mullite coatings. Coatings produced from mullite powders and suspensions are deposited by plasma spraying while measuring in-flight particle temperature and velocity. Powder morphology and spraying conditions are correlated with measured coating properties, creating a process map for engineering mullite coatings for specific applications. It is shown that coating crystallinity, microstructure, and mechanical properties vary widely depending on powder morphology, processing, and in-flight particle characteristics.
Plasma Spraying of Lanthanum Silicate Electrolytes for Intermediate Temperature Solid Oxide Fuel Cells (ITSOFCs)
Authors: Dru S. , Meillot E. , Wittmann-Teneze K. , Saboungi M.-L. , Benoit R.
Published: December 2022

This study investigates the feasibility of manufacturing lanthanum silicate coatings for solid oxide fuel cells by atmospheric plasma spraying. The coatings produced are cohesive, relatively dense, and contain no secondary phases. Test results show that the starting composition of the powder is maintained after spraying and that particle velocity depends primarily on the plasma gas mixture. Due to the relatively high melting temperature of the particles, dense apatite coatings with few microstructural defects are obtained.
Gastight Yttria-Partially Stabilized Zirconia Layers Manufactured by Suspension Plasma Spraying for SOFC Electrolyte Functional Layers
Authors: Brousse E. , Montavon G. , Denoirjean A. , Fauchais P. , Wittmann-Teneze K.
Published: December 2022

Intermediate temperature solid oxide fuel cells include in their design a solid electrolyte layer, usually made of yttria-stabilized zirconia, that acts as an ionic conductor through which oxygen ions diffuse. This layer must be as thin as possible to limit ohmic losses yet have a low leakage rate corresponding to a low level of connected stacking defects such as microcracks. Suspension plasma spraying (SPS) appears to be a viable method for manufacturing such layers and is used in this study to produce gastight coatings that with further improvements may meet the requirements of SOFCs. The paper describes the setup and optimization of the SPS process and the methods used to evaluate the solid electrolyte layers.
Plasma Sprayed Metal Supported SOFCs Having Enhanced Performance and Durability
Authors: Ansar A. , Ilhan Z. , Arnold J.
Published: December 2022

This paper describes recent improvements in metal supported solid oxide fuel cells produced by plasma spraying. By optimizing the process, incorporating nano-micro structured electrodes, and introducing additional layers to prevent interlayer diffusion, the power density of these cells has doubled, voltage has increased to 1.1 V, degradation rates have been cut in half, and redox stability has improved. Although upscaling to larger substrates initially caused distortion in the metal supports, the problems were successfully overcome.
High Velocity Suspension Flame Spraying (HVSFS): Process Development and Industrial Applications
Authors: Rauch J. , Stiegler N. , Killinger A. , Gadow R.
Published: December 2022

This paper provides an overview of the high velocity suspension flame spraying (HVSFS) process that covers spray gun design, suspension and substrate preparation, and process optimization. Examples are given showing how the process is used to produce tribofunctional coatings for engine applications, electrolyte layers for SOFCs, and netshape chromia for high-end scissor blades. The substrates in the three examples are AlSi9Cu3, Crofer nickel cermet, and low carbon steel.
Suspension Plasma Sprayed Titanium Oxide and Hydroxyapatite Coatings
Authors: Jaworski R. , Pawlowski L. , Pierlot C. , Roudet F. , Kozerski S. , Petit F.
Published: December 2022

In this investigation, titanium dioxide and hydroxyapatite (HA) suspensions are plasma sprayed onto stainless steel, titanium, and aluminum substrates and the structure and properties of the resulting layers are correlated with spraying conditions. The suspensions were formulated with fine TiO2 pigment and HA milled from spray-dried powder or synthesized from calcium nitrate and ammonium phosphate. In some experiments, an atomizer was used to inject the suspensions into the plasma jet, and in others, the suspensions were fed into the jet using continuous stream injection. The deposits are characterized on the basis of morphology, chemical and phase composition, scratch hardness, and dielectric strength.
Suspension Plasma Spraying: Process Development and Applications
Authors: Vaßen R. , Kaßner H. , Mauer G. , Stöver D.
Published: December 2022

Suspension plasma spraying (SPS) offers the manufacture of unique microstructures which are not possible with conventional powder feedstocks. Due to the considerably smaller size of the droplets and also the further fragmentation of these in the plasma jet, the attainable microstructural features like splat and pore sizes can be downsized to the nanometer range. Our present understanding of the SPS deposition process including injection, suspension plasma plume interaction, and deposition is outlined in this report. The conclusions drawn are based on microstructure analysis in combination with enthalpy probe and particle temperature and velocity and measurements. Measurements with a water-cooled stagnation probe provide valuable information on the interaction of the carrier fluid with the plasma plume. The examples presented include segmented thermal barrier coatings for turbine components, LSM cathode deposits for SOFCs, and TiO2 layers for photovoltaic Gratzel cells.
Deposition Behavior of Copper Particles onto Flat Substrate Surface in Cold Spraying
Authors: Fukumoto M. , Mashiko M. , Yamada M. , Yamaguchi E.
Published: December 2022

This study investigates the deposition behavior of cold sprayed copper particles on flat surfaces. In the experiments, a Laval-barrel nozzle was used to spray water atomized spherical copper particles with a mean diameter of 5 µm onto mirror-polished stainless steel. The particles were similar in morphology regardless of spraying conditions with an average bonding strength of 60 MPa as determined by nano scratch (shear) testing. An amorphous-like layer at the particle-substrate interface indicates that the deformation of the particles initially destroys their surface oxide, revealing an active fresh surface that facilitates metallic bonding. At higher spray velocities, metal jetting is observed at the periphery of flattened particles and its relationship with deposition efficiency is statistically analyzed and put forth as a potential method for controlling the cold spray process.
Effects of Gas Pressure of Cold Spray on the Formation of Al Based Intermetallic Compound
Authors: Lee H. , Shin H. , Ko K.
Published: December 2022

Post-annealing of cold spray coatings has great potential for wear applications because it produces intermetallic compounds at low temperature far below equilibrium. This study investigates the effects of spraying pressure on the intermetallics formed and their dispersion characteristics. In the experiments, Al and Al-Ni powders were sprayed on Ni and Al substrates at 0.7, 1.5, and 2.5 MPa and a portion of the coating samples were annealed in argon at 500, 550, and 600 °C. Detailed examinations showed that Al particles are subject to peening effects that can interfere with the formation of intermetallic compounds during annealing, but that the effects can be mitigated by controlling gas pressure. Spraying pressure was also found to have an effect on the formation of eutectic pores in Al-Ni composite coatings, with higher pressures corresponding to fewer pores.
TEM Microstructural Investigation of MCrAlY Coatings Manufactured by Cold Gas Dynamic Spraying
Authors: Richer P. , Yandouzi M. , Jodoin B. , Zúñiga A.
Published: December 2022

This study is part of an ongoing effort to develop high performance CoNiCrAlY bond coats by means of cold gas dynamic spraying in order to have complete control of bond coat microstructure. As such, the objective of the work presented in this paper is to perform a detailed analysis of cold sprayed CoNiCrAlY layers to assess any changes in microstructure, relative to the original feedstock powder, that may have occurred during layer build-up and compaction. Based on SEM, TEM, and XRD examination results, it is shown that, contrary to the generally accepted theory, important microstructural changes occur during the cold spray deposition process. In the coating samples examined, investigators observed evidence of grain refinement in the CoNiCr γ-phase matrix and partial dissolution of NiAl β-phase precipitates. These changes are a result of severe plastic deformation due to the high-velocity impact of sprayed particles.
Influence of Spray Materials and their Surface Oxidation on the Critical Velocity in Cold Spraying
Authors: Li C.-J. , Wang H.-T. , Zhang Q. , Yang G.-J. , Li W.-Y. , Liao H.L.
Published: December 2022

Critical velocity is an important parameter in cold spraying. It determines the deposition efficiency under a given spray condition. It depends not only on material types, but also particle temperature and oxidation conditions. In this present work, three types of materials including copper, 316L stainless steel, and Monel alloy were used to deposit coatings by cold spraying. The critical velocities of spray materials were determined using a novel measurement method. Oxygen content in three powders was changed by isothermal oxidation at ambient atmosphere. The effect of oxygen content on the critical velocity was examined. It was found that critical velocity was significantly influenced by particle oxidation besides material properties. The critical velocity of Cu particles increased from about 300 m/s to over 610 m/s with a change in oxygen content in the powder. The results suggest that with a severely oxidized powder, critical velocity tends to be dominated by the oxide on the powder rather than material properties.
Nano Titania Embedded Hydroxyapatite Coating by Precursor Plasma
Authors: Varadaraajan V. , Visveswaran R. , Mohanty P.S.
Published: December 2022

In recent studies, titania has been added to hydroxyapatite (HA) coatings to impart photocatalytic properties. The benefits of such additions are maximized when titania is in nanocrystalline anatase form. In this study, nano-titania was synthesized in-flight from a liquid precursor consisting of ethanol and titanium isopropoxide. The precursor and HA powder were fed into a plasma gun, forming nano-titania particles that embedded in the HA. Coatings of pure titania and titania-embedded HA were deposited under different spray conditions on titanium coupons and then characterized via XRD and SEM analysis. The titania coatings contained ultrafine anatase and rutile particles with anatase being favored by more power input and rapid quenching. The composite coatings contained dispersed ultrafine titania particles in a matrix consisting primarily of HA with trace amounts of calcium phosphate and amorphous phases. The effect of spraying parameters on phase and microstructure evolution is discussed as well.
Bactericidal Effects of HVOF-Sprayed Nanostructured TiO2 on Pseudomonas Aeruginosa
Authors: Jeffery B. , McDonald A. , Peppler M. , Lima R.S.
Published: December 2022

This study assesses the photocatalytic properties of HVOF-sprayed nanostructured TiO2 coatings, particularly their bactericidal effect. The surfaces of the coatings were lightly polished before being exposed to bacterial solutions of known concentration. The solution was dispensed on the coating and irradiated with white light in 30-minute intervals up to 120 minutes. On polished HVOF-sprayed TiO2 coatings, 24% of the bacteria were killed after 120 minutes of exposure. On stainless steel controls, the percentage of bacterial cells killed was approximately 6% for most of the exposure times studied.
Research on Plasma Sprayed High Crystallinity Degree Hydroxyapatite Powder for Biological Coating
Authors: Zhenduo Li , Yueguang Yu , Keli Zeng , Jia Zhan , Xiaodong Zhao
Published: December 2022

In this paper, a new treatment method, flame remelt spheroidization, is used to improve the crystallinity of hydroxyapatite (HA) powders. Based on SEM and XRD analysis, the treated powder is more crystalline than spray-dried and sintered HA powder and has higher density and a smoother surface morphology as well. In addition, coatings produced by plasma spraying the treated powder are shown to have better surface microstructure than coatings synthesized from untreated powder.
Numerical Approach and Optimization of the Combustion and Injection Techniques in High Velocity Suspension Flame Spraying (HVSFS)
Authors: Dongmo E. , Gadow R. , Killinger A.
Published: December 2022

The aim of this work is to develop an analytical methodology for the analysis and prediction of high-velocity suspension flame spraying (HVSFS) under various operating conditions, to determine the effect of individual parameters on the process, and to aid and promote the design of HVSFS torches. A key aspect of the work is the development of a model that accounts for fuel gas combustion, evaporation of organic solvents, and heat, momentum, and mass transfer between the flame and suspension droplets.
Predict Flexural Rigidity of Sandwich Structures Using Mechanical Properties of the Constituents
Authors: Azarmi F. , Coyle T.W. , Mostaghimi J.
Published: December 2022

Recently, an advanced technique was developed to fabricate sandwich structures for high temperature applications by depositing alloy 625 skins on Ni alloy foam core by thermal spraying. This study tries to utilize an analytical model to estimate the mechanical performance of these structures based on the mechanical properties of the constituents. The mechanical behavior of the Ni alloy foam is assessed via compression testing, while tensile tests are used in the case of the alloy coating. The flexural rigidity of the sandwich structure is calculated using analytical models and experimentally obtained elastic moduli of the alloy 625 coating and Ni alloy foam. The model is also used to calculate the flexural rigidity of sandwich samples with different skin thicknesses to check the accuracy of the model and to understand the effect of skin thickness on the predicted mechanical performance of sandwich structures. The effect of heat treatment on the mechanical behavior of sandwich structures is investigated as well.
The Role of Substrate Surface Chemistry on Splat Formation during Plasma Spray Deposition by Experiments and Simulations
Authors: Tran A.T.T. , Hyland M.M.
Published: December 2022

NiCr was plasma sprayed at room temperature on aluminum and stainless steel substrates that had been hydrothermally treated in deionized water for 30 minutes. A major difference was observed in that splat formation occurred only on the stainless steel. A numerical model was developed to simulate the impact of molten nickel splats on the treated substrates. The simulation closely matched experimental results in terms of splat morphology, porosity, delamination, and specific locations of substrate melting. Moreover, it confirmed that splat morphology is influenced, not by oxide thickness, but rather by water release from the dehydration of oxyhydroxide at the outermost surface. The insulating layer of released water inhibits heat transfer from the splat to the substrate, which reduces solidification rates, resulting in further spreading and thinning of splats. These findings shed light on splat spreading and solidification and provide insights on the effect of substrate surface chemistry on thermal spray splat morphology.
A Study on Arc Instability Phenomena of a Hollow Cathode Plasma Torch in a Low Pressure Environment
Authors: Stanisic J. , George A. , Mohanty P.S.
Published: December 2022

This study investigates arc instability phenomena associated with hollow-cathode plasma torches under low pressure. Stable and unstable regimes are evaluated based on Fourier analysis of gun voltage. For comparison, arc fluctuations with a solid-cathode torch are studied as well. Different internal hardware configurations are used during spraying to identify and assess important factors in the design of hollow and solid cathode guns. This work also characterizes a number of parameters that would exploit plume elongation and accelerated gas velocities under low-pressure conditions.
Modeling a New Spray Process Combining Plasma and HVOF
Authors: Martinez B. , Mariaux G. , Vardelle A. , Barykin G. , Parco M.
Published: December 2022

The aim of this study is to model a spray process that combines aspects of plasma and HVOF spraying. The process is characterized by its stability over a broad range of fuel-oxidant conditions and ability to produce coatings using relatively little gas with rather low gross heating values The mathematical model developed accounts for the formation of the plasma jet, the combustion process, and supersonic flow issuing from the spray torch. Simulating the new process made it possible to investigate the effect of the plasma on the velocity and temperature of the gas flow inside and outside the gun. The equations were solved using CFD code and predictions were compared with experimental observations. The benefits of the plasma jet are discussed on the basis of predictions and fuel combustion mechanisms.
Current Status and Future Prospect of Thermal Spray Coating Applications and Coating Service Market of Job Shops in Japan
Authors: Nakahira A.
Published: December 2022

According to a recent survey, the thermal spray market in Japan is approximately 100 billion yen. The market consists of three sectors, coating services (45 billion yen), in-house production (45 billion yen), and sales of thermal spray equipment and consumables (10 billion yen). This paper provides an overview of the coating services market broken out by application segments. It also discusses future trends.
Market Direction and Application Opportunities for Thermal Spray Growth in Korea
Authors: Lee C.
Published: December 2022

This paper provides a summary of the status and potential of thermal spray activities in Korea. It describes how various market sectors in Korea are using spray coating technology and presents annual sales estimates and share of market data broken out by industry, spraying technology, and patents awarded. It also reviews recent advancements in the development and use of thermal spray technology in Korea along with anticipated future impacts.
Thermal Spraying in India: Status and Prospects
Authors: Sundararajan G. , Mahajan Y.R. , Joshi S.V.
Published: December 2022

This paper provides a summary of the status and potential of thermal spray activities in India. A meaningful indicator of the future growth of thermal spray technology in India is the rapid rise in the number of job shops that offer thermal spray coating services. The number of captive units meeting in-house coating needs has also increased markedly in recent years. These trends have in part been fueled by an increase in the number of home-grown Indian companies manufacturing spray systems, handling equipment, and performance evaluation test rigs. Research in areas such as cold gas dynamic spraying (CGDS) and solution precursor plasma spraying (SPPS) is also on the rise in India.
Thermal Spraying of FeNiW Coatings to Improve the Performance of Casting Molds in the Aluminum Industry
Authors: Wilden J. , Jahn S. , Drescher V.E.
Published: December 2022

The lifetime of casting molds in the aluminum industry is strongly limited by the corrosiveness of aluminum melts and alternating thermal and mechanical loads. With the added protection of sintered tungsten pseudoalloy inlays, casting molds have been known to last as much as 1000 times longer, and the work presented here indicates that it may be possible to replace the massive liners with a twin wire arc or plasma sprayed coating that can be tailored by varying spraying parameters.
Microstructure Evolution and Dielectric Properties of Plasma Sprayed BaTiO3 Coatings
Authors: Kim Y.-M. , Baik K.-H. , Park K.-S.
Published: December 2022

BaTiO3 coatings are very promising for a wide range of applications in microelectronics because of their high dielectric constant and low leakage current. In this study, atmospheric plasma spraying is used to produce thick BaTiO3 coatings and their microstructural features and dielectric properties are examined. The coatings were mainly composed of amorphous phase with small amounts of crystalline phase due to the incorporation of partially-molten droplets. The as-sprayed coatings were crystallized to BaTiO3 by low temperature heat treatment and a mixture of BaTiO3 and BaTi2O5 at higher temperatures. At 1200 °C, the coating formed an equiaxed grain structure due to sintering effects and the dielectric constant was significantly improved.
Development of Kinetic Sprayed Coatings for the Application of Die Soldering Resistance
Authors: Khan F.F. , Bae G. , Kang K. , Kumar S. , Na H. , Kim J. , Lee C.
Published: December 2022

This study assesses the potential of kinetic-spray coatings for dealing with the effects of soldering and erosion on aluminum casting dies. In the experiments, molybdenum-boride cermet and cobalt-based alloy powders are cold sprayed onto SKD61 substrates. Coating microstructure is assessed via SEM and XRD analysis and several mechanical properties are measured. In order to evaluate soldering resistance, the coatings are immersed in a molten aluminum bath. Although cold-sprayed CoCrNiWC exhibited high coating density and low porosity, its soldering resistance was significantly lower than that of MoB-NiCr. The boride cermet coating not only exhibited superior soldering resistance, but also higher hardness, bond strength, and wear resistance. However, its deposition efficiency needs further improvement.
Defect Reduction in Semiconductor through Thermal Spray Technology
Authors: Wang H.
Published: December 2022

Bead blasting and thermal spray coatings are often applied on process kits used in vacuum deposition chambers to improve adhesion between kit surfaces and deposited films. This study shows that in order to maximize chamber service time and reduce processing defects, thermal expansion mismatches must be considered between chamber components, sprayed coatings, and vacuum deposited films. When a titanium sheet coated with arc sprayed aluminum was placed in a titanium nitride deposition chamber, significant particle spiking was observed. However, during the same period of chamber service time, particle performance was stable for titanium coated with arc sprayed molybdenum. It should be noted that the thermal expansion coefficients of Ti and Mo are much closer than those of Ti and Al. By further optimizing the cohesion strength of the arc-sprayed Mo coating, even lower particle counts have been achieved, corresponding to fewer processing defects and prolonged chamber kit lifetime.
Direct Write of Antenna Aperstructures and Electronic Interconnects Using Kinetic Metallization
Authors: Tapphorn R.M. , Henness J.A. , Gabel H.
Published: December 2022

A direct write method of fabricating antenna structures onto doubly curved dielectric surfaces has been developed using low temperature kinetic metallization. This paper describes the process and its use for depositing copper on various dielectrics and silver on alumina substrates and copper lead frames.
Electrically Conductive Plasma Sprayed Oxide-Metal Coatings on Glass Ceramic Substrates
Authors: Floristán M. , Gadow R. , Killinger A.
Published: December 2022

Coating operations over glass ceramic substrates represent a new field for thermal spray applications. Due to the unique thermal and mechanical properties of glass ceramics, especially the low or even negative CTE, coating processes must be adapted to reduce the distribution of thermal stresses in the system and to not damage the substrate. This study investigates the deposition of a complex-shaped ceramic-metallic multilayer coating system that could potentially serve as a heating element in a glass ceramic cooking plate. To ensure coating adhesion, the substrates are preheated and their surfaces are grit blasted. In order to minimize stresses associated with the deposition of metal, the movement of the spraying mechanism was automated with robot control and new masking concepts were developed to ensure the accuracy of the shape and placement of the coating. The influence of spraying parameters on coating properties and residual stress distribution is analyzed as well.
Plasma Sprayed Ceramic Tray Members for Firing Ceramic Capacitors
Authors: Yamakawa O. , Nihonmatsu H. , Morisasa M. , Hotta H.
Published: December 2022

Multilayer ceramic chip capacitors (MLCCs) are produced in large numbers for use in automobiles, cell phones, flat panel displays, and other products. Like many circuit components, they are being required in more compact sizes, larger capacities, and reduced costs year by year. MLCCs are kiln-fired on stacked carriers made from Al2O3-SiO2 covered with a Y2O3-stabilized ZrO2 topcoat and an Al2O3 basecoat. This paper presents the rationale behind the selection of the coating materials and evaluates processes by which they can be applied. It compares the microstructure and properties of sintered, atmospheric plasma sprayed (APS), and water stabilized plasma sprayed (WSP) yttria-stabilized zirconia and discusses the advantages and disadvantages of each process.
Optimized Arc Wire Sprayed Fiber Prepregs for Advanced Manufacturing of Metal Matrix Composites (MMCs)
Authors: Silber M. , Gadow R.
Published: December 2022

The production of light metal matrix composites (MMCs) using coated fiber prepregs processed by thixoforging offers several advantages over well-established technologies like squeeze casting and diffusion bonding. In order to obtain the required globular microstructure prior to thixoforging, reinforcement fibers are coated with the matrix material by twin wire arc spraying. Damage to the sensitive fibers is avoided by reducing the thermal load via optimized cooling. This study analyzes the influence of spraying parameters on the microstructure and mechanical properties of MMCs. An innovative method for automated the coating of reinforcement fibers is presented.
Parameters Affecting Bond Strength and Surface Roughness in Twin Wire Arc Spray Aluminum Coatings
Authors: Watson M. , Gansert R.
Published: December 2022

Twin wire arc sprayed aluminum coatings are used extensively in semiconductor processing equipment. In certain applications, such as metal reclamation, rough coating textures are desirable as the added surface area facilitates the collection of metals and lowers manufacturing costs. There are many factors that affect the surface roughness of twin wire arc sprayed coatings. This study investigates coating conditions that produce rough textures and the influence of surface roughness on bond strength. Traditional theory of arc spraying has been that to obtain a rough coating, particle velocity should be reduced by decreasing the atomizing air pressure of the system. Decreasing air pressure, however, may have a negative impact on bond strength, the extent of which is assessed in this study.
High Temperature Corrosion Behavior of Cold Spray Ni-20Cr Coating on Boiler Steel in Molten Salt Environment at 900 °C
Authors: Bala N. , Singh H. , Prakash S.
Published: December 2022

In this investigation, Ni-20Cr alloy powder was deposited on SA 516 boiler steel by cold spraying. The oxidation kinetics of both coated and uncoated samples, evaluated in molten salt, followed a parabolic rate. The rate constant of the Ni-20Cr coated steel was much lower than that of the bare boiler steel. X-ray diffraction, SEM-EDX, and X-ray mapping were used to analyze the oxidation products of the coated and uncoated boiler steel. The uncoated steel exhibited intense spalling and peeling of its oxide scale, which may be due to the formation of Fe2O3 oxides. The Ni-20Cr coating reduced the weight gain of the steel by more than 87% possibly due to the formation of nickel and chromium oxides.
Corrosion and Erosion Resistant Thermal Spray Coatings of Fe-Si Intermetallics
Authors: Okagaito T. , Fukuda Y.
Published: December 2022

This study evaluates Fe-Si intermetallic powders as an alternative to powders currently used to coat furnace walls in pulverized coal fired boilers. The developed powder mainly consists of Fe2Si, which has a relatively low melting point among iron silicides. The powders were deposited on CrMo steel substrates by HVOF and atmospheric plasma spraying and the resulting coatings were subjected to corrosion and erosion testing. Under conditions simulating the operating environment in a low NOX boiler, the HVOF sprayed Fe-Si coatings exhibited sulfidation resistance nearly equal to that of Cr-Ni layers, and in high-temperature erosion tests, the APS intermetallic coatings with boron additions were found to be more erosion resistant than conventional Cr3C2-NiCr coatings.
Wire Arc Sprayed High Quality Anti-Corrosion and Wear-Resistant Coatings
Authors: Wilden J. , Jahn S. , Reich S. , Drescher V.E. , Durham R. , Schütze M.
Published: December 2022

Due to its easy handling and low operating costs, wire arc spraying has become one of the most established processes for applying protective coatings to components used in waste incineration plants. This paper discusses the development of relatively low-cost Fe-Cr-Si coating materials for incinerator applications and the corrosion and wear properties that have been achieved using conventional arc spraying methods.
High-Velocity Collision of Hot Particles with Solid Substrate under Detonation Spraying: Detonation Splats
Authors: Zlobin S.B. , Ulianitsky V.Yu. , Shtertser A.A. , Smurov I.
Published: December 2022

The aim of this study is to analyze the shape of splats deposited by detonation spraying and correlate splat morphology with the velocity and temperature of particles as they hit the substrate. The obtained results are in good agreement with numerical calculations for nickel splats and show that the thermo-physical properties of composite particles can be estimated from their splat characteristics as well. An understanding of these relationships for various materials is necessary to calculate particle heating in the detonation barrel.
Further Developments in Internal Diameter HVOF Application of WC-CoCr for Hard Chrome Replacement in Critical Applications Such as Landing Gear
Authors: Matthäus G. , Henry J. , Ackermann D. , Brandl W.
Published: December 2022

This paper describes an inner diameter HVOF spraying technique and associated tests methods. In the experiments, WC-CoCr was applied to an internal diameter of 150 mm and evaluated using a dedicated pin-on-disk wear test and standard axial fatigue tests. The results are presented and discussed along with the potential for further development of the inner diameter HVOF spraying technique.
Vapor Phase Deposition Using LPPS Thin Film
Authors: von Niessen K. , Gindrat M. , Refke A.
Published: December 2022

Low-pressure plasma spray thin film (LPPS-TF) is a recently developed vacuum plasma spray technology that makes it possible to deposit coatings not only by melting feedstock material, but also by vaporizing injected particles. This capability fills a gap between conventional vapor deposition and thermal spray processes. The vaporizing of coating material and formation of layers out of the vapor phase result in unique coating microstructures with superior properties. This paper reports on the progress made in the development of functional coatings built up from the vapor phase of metal and oxide ceramics.
LPPS – Thin Film Processes: Overview of Origin and Future Possibilities
Authors: Muehlberger E. , Meyer P.
Published: December 2022

This paper discusses the history of the low-pressure plasma spraying (LPPS) process and some of the developments that led to its use as a thin film deposition technique. It also discusses the advantages of the process and its potential for further improvement and additional applications.
A Novel Single Cathode Plasma Column Design for Process Stability and Long Component Life
Authors: Mohanty P.S. , George A. , Pollard L. , Snyder D.
Published: December 2022

Arc instability in dc plasma guns has a detrimental effect on coating quality and electrode life. This paper investigates the impact of a single-cathode plasma column design on process stability, versatility, and component life. The design increases arc length and minimizes restrike, enabling high voltage, low current operation as well as the use of ternary gas to increase enthalpy. Arc behavior is assessed by monitoring fluctuations in electrical signals and correlated with particle temperature and velocity. The takeover-steady mode is shown to be the typical operating mode of the plasma jet for this design, resulting in steady particle characteristics over long periods of maintenance-free operation.
Investigation of Plasma Spraying with Internal Axial Powder Injection
Authors: Gao Y. , Yang D-M. , Yan Z.-J.
Published: December 2022

Plasma spraying with axial powder injection inside the anode nozzle is a method considered to markedly enhance deposition efficiency and reduce plasma power compared to the most general method of injecting powder at the nozzle exit. However, powder injecting inside the nozzle will also likely cause problems from powder deposition on the nozzle wall and clogging of the particle feed channels. In this study, spherical stainless steel 316 and angular alumina powders with a mean size of 20-40 μm are used to deposit coatings via axial powder injection. The effect of powder feed rate, gas flow rate, and plasma power on deposition efficiency and particle clogging are investigated. The results show that particle clogging can be avoided by reducing powder feed rate and increasing the velocity of the plasma jet.
Plasma Spraying of Refractory Cermets by the Water-Stabilized Spray (WSP) System
Authors: Ctibor P. , Chraska P. , Brozek V. , Cheong D.-I. , Yang S.-H.
Published: December 2022

The goal of this study is to find applicable spray conditions for producing tungsten (W), zirconium carbide (ZrC), and W-ZrC cermet layers. In the experiments, W and ZrC powder mixtures were fed into the plasma of a water-stabilized plasma gun and coatings approximately 1 mm thick were sprayed on graphite substrates. Pure W and pure ZrC were deposited under similar conditions. Microhardness, surface roughness, XRD, XRF, dilatometry, and spectroscopic techniques were used to characterize the coatings. The resulting coatings were found to be hard with a high elastic modulus.
The Influence of Spray Parameters on the Characteristics of Al2O3 Particles and Coatings Sprayed by Detonation Spray
Authors: Sun B. , Fukanuma H. , Ohno N.
Published: December 2022

This study investigates the influence of high-frequency pulse detonation (HFPD) spraying parameters on particle characteristics and coating quality. A dual-slit velocimeter was used to measure the velocity and temperature of Al2O3 particles as fuel flow ratio and spray distance were adjusted. Experimental results show that particle velocity varied from 600 to 820 m/s as the fuel flow ratio was changed, but particle temperature remained relatively constant at about 2200 °C. Spraying distance had essentially no effect on in-flight particle properties although it influenced deposition efficiency, as did fuel flow ratio.
Particle Image Velocimetry Diagnostics for Suspension Plasma Spraying
Authors: Marchand O. , Bertrand G. , Planche M.P. , Bailly Y. , Girardot L.
Published: December 2022

In this investigation, particle image velocimetry (PIV) diagnostics were employed to analyze the spray produced by a two-fluid atomizer as used in suspension plasma spraying (SPS). This led to a change in the design of the atomizing nozzle in order to achieve a high-speed spray with narrow distributions in droplet size. The resultant spray was characterized and the diagnostic was adapted accordingly. Various suspensions of YSZ powders were then injected into the plasma under different conditions and particle velocities were determined and correlated with the coating morphologies obtained.
Influence of Convergent-Divergent Nozzle Design on Plasma Properties and Resultant Coatings
Authors: Caron N. , Macqueron C. , Meillot E.
Published: December 2022

The peculiar microstructure of plasma-sprayed coatings affects their physical properties. Many of these properties are, to a great extent, dominated by the influence of the spraying process on in-flight particle parameters. In order to improve the quality of plasma-sprayed coatings and to enhance the efficiency of plasma spray deposition, a wide range of anode nozzles have been developed for air plasma torches. The objective of this work is to investigate the influence of two convergent-divergent nozzle designs on plasma-sprayed YSZ particles at impact and the permeability, porosity, and microstructure of the resulting coatings.
Improved Thermal Spray Consistency via Plume Sensors – An Aerospace Perspective
Authors: Sauer J.P. , Grijilva T. , Pouliot L.
Published: December 2022

This paper discusses the different ways plume sensors can be used in thermal spraying and presents examples highlighting the use of a commercial plume sensor in actual production situations.
Alumina Splat Investigation: Visualization of Impact and Splat / Substrate Interface for Millimeter Sized Drops
Authors: Goutier S. , Vardelle M. , Labbe J.C. , Fauchais P.
Published: December 2022

The aim of this work is to investigate the effect of substrate surface chemistry (e.g., oxidation and atom diffusion) on the flattening of a single millimeter-sized alumina drop. To that end, a new technique to produce such drops with different impact velocities has been developed. It consists of a rotating crucible heated by a transferred plasma arc and a piston that controls substrate velocity and, as a result, the impact velocity of the drop. A fast camera working in concert with a fast pyrometer precisely records drop flattening and cooling. This system makes it possible to study interface phenomena, such as desorption and wettability, as well as the effects, at impact, of the kinetic energy or Weber number of the flattening drop.
In Situ Monitoring of Particle Consolidation during Low Pressure Cold Spray by Ultrasonic Techniques
Authors: Lubrick M. , Titov S. , Leshchynsky V. , Dzhurinskiy D. , Maev R.Gr.
Published: December 2022

This work assesses the potential of using an ultrasonic probe attached to the back of the substrate to monitor the cold spraying process. While this is only a preliminary study, focusing more on presenting the results than analyzing them, a few conclusions may be drawn. With acoustic sensing, not only can the final value of thickness be estimated, it is also possible to see the dynamics of how the buildup takes place in real time. As shown in the data plots, the buildup process for aluminum-alumina composites is fairly universal across the spray with slower buildup at the outer edges of the coating. More importantly, it is shown that nozzle speed, spray diameter, and thickness estimates fit well with measured values.
Corrosion Behavior and Microstructure of Al-Al2O3 Coatings Produced by Low-Pressure Cold Spraying
Authors: Villafuerte J. , Dzhurinskiy D. , Ramirez R. , Maeva E. , Leshchynsky V. , Maev R.Gr.
Published: December 2022

In this study, low-pressure cold spraying was used to deposit Al and Al-Al2O3 composite powders on different substrate materials, including steel, aluminum, and magnesium alloy. Corrosion performance was evaluated by electrochemical testing in 1M NaCl electrolyte and microstructure was examined by means of SEM analysis. The results show that the corrosion potential of Al-Al2O3 coatings depends on the content of alumina and that its presence does not appear to accelerate dissolution and failure of passivation oxide films. The investigation also revealed that pure aluminum coatings on aluminum alloy substrates can act as sacrificial anodes, thus providing corrosion protection.
Relationship between the Interlamellar Bonding and Properties of Plasma-Sprayed Y2O3-ZrO2 Coatings
Authors: Xing Y.-Z. , Li C.-J. , Li C.-X. , Yang G.-J.
Published: December 2022

In this study, yttria-stabilized zirconia (YSZ) coatings were plasma sprayed on heated substrates at temperatures ranging from room temperature to 1100 °C. Lamellar mean bonding ratio was estimated from the ionic conductivity of the coatings and mechanical properties were measured by indentation testing. The bonding ratio, elastic modulus, and fracture toughness of the YSZ coatings were found to increase with substrate surface temperature. The results show that the mechanical properties of plasma sprayed ceramic coatings are determined by interlamellar bonding and that significant improvements can be achieved by controlling coating surface temperature.
Effects of Some Light Alloying Elements on the Oxidation Behavior of Fe and Ni-Cr Based Alloys during Air Plasma Spraying
Authors: Zeng Z. , Kuroda S. , Kawakita J. , Komatsu M. , Era H.
Published: December 2022

This study investigates the effect of alloying additions on the oxidation behavior of iron (Fe) and nickel-chromium (NiCr) powders during atmosphere plasma spraying. The chemical composition and phases of oxides in the particles as well as in the coatings are assessed for different powder mixtures and spraying parameters. The results show that oxygen content can be significantly reduced by adding silicon (Si) and boron (B) to iron powders and Si, B, and carbon (C) to NiCr. The preferential oxidation and subsequent vaporization of Si, B, and C from the surface of the sprayed particles are believed to play a major role in controlling oxidation in the APS process.
Study of the Splat-Substrate Interface for a NiCr Coating Plasma Sprayed on to Polished Aluminum and Stainless Steel Substrates
Authors: Brossard S. , Munroe P.R. , Tran A. , Hyland M.M.
Published: December 2022

A study of plasma-sprayed NiCr splats shows that the morphology and characteristics of the splat-substrate interface depends on the substrate material. Splats on stainless steel tend to be regular and disc-shaped and localized melting of the substrate and intermixing and diffusion were observed at the interface. Splats on aluminum, on the other hand, were slightly more irregular and the contact at the splat-substrate interface was found to be porous and poor. For both types of splats, several oxide phases were observed. Their formation and the formation of the splats are discussed, although further study is required to fully identify the origins of the differences observed.
Testing Method of Spalling Resistance for Thermal Barrier Coating by Thermal Cycle and Thermal Shock
Authors: Harada Y. , Itoh Y. , Kojima Y. , Ono F.
Published: December 2022

“Testing Method for Thermal Cycle and Thermal Shock Resistance of Thermal Barrier Coating (TBC)” is a Japanese Industrial Standard (JIS) newly established by the Minister of Economy, Trade, and Industry in 2008, after deliberations by Japanese Industrial Standards Committee, in accordance with the Industrial Standardization Law. The standard specifies a testing method that evaluates the spalling resistance of TBCs based on operating conditions in gas turbines. This paper provides an overview of the standard along with examples of its use.
Effect of Powder Characteristics on Properties of Warm-Sprayed WC-Co Coatings
Authors: Chivavibul P. , Watanabe M. , Kuroda S. , Komatsu M. , Sato K. , Kitamura J.
Published: December 2022

In this present work, WC-Co coatings with different Co contents were deposited by warm spraying using two different powder sizes and their microstructure, hardness, fracture resistance, and wear properties were investigated. The coatings produced from fine powders showed higher hardness and better wear behavior for all Co contents than those deposited from coarse powders, which is attributed to improved splat-splat bonding and a reduction in porosity that comes with using fine powder.
The Effect of Heat Treatment on the Oxidation Mechanism of Blended Powder Cr3C2-NiCr Coatings
Authors: Matthews S. , James B. , Hyland M.
Published: December 2022

This work assesses the effect of heat treatment on the oxidation resistance of blended-powder CrC-NiCr coatings produced by HVOF spraying. The as-sprayed coating phases oxidized independently with NiCr rapidly forming nickel oxide, which was subsequently consumed by a solid-state reaction with Cr2O3. The NiO formed two distinct morphologies: large bulbous oxides on thin regions of exposed alloy and thin, flat oxide layers on large alloy regions. Heat treatment led to sintering of the splats and diffusion of Cr from the carbide phase into the NiCr alloy, increasing Cr to the point where Cr2O3 dominated the oxide composition from the earliest exposure time. The implications of the change in oxidation mechanism and oxide morphology are discussed.
A Comparative Study of the Isothermal Oxidation Behaviour of APS, VPS and HVOF CoNiCrAlY Coatings
Authors: Di Ferdinando M. , Fossati A. , Lavacchi A. , Borgioli F. , Bardi U. , Giolli C. , Scrivani A. , Rizzi G.
Published: December 2022

Thermal barrier coatings (TBCs) are widely used in gas turbines to reduce thermal exposure of structural components and increase turbine efficiency. They typically consist of a MCrAlY bond coat and a YSZ topcoat. At high temperatures, a thermally grown oxide (TGO) layer forms between the bond coat and topcoat. If this layer is a continuous scale of alumina, it will act as a diffusion barrier to suppress the formation of other detrimental oxides, thus helping to protect the substrate from further oxidation. It has been reported, however, that other oxides, such as chromia, spinel, and NiO, may form along with the TGO layer, ultimately leading to TBC failure. To investigate such claims, coatings of comparable thickness were deposited by various spraying methods onto a superalloy substrate using a powder of the same composition. Samples were isothermally oxidized at 1273 K for different periods up to 3000 hours. The samples were examined before and after furnace tests and the results are presented and discussed.
Densification of Atmospheric Plasma Sprayed Wear Resistant Coatings
Authors: Tillmann W. , Vogli E. , Krebs B. , Tekkaya A.E. , Brosius A. , Franzen V.
Published: December 2022

Thermal spray coatings produced from hard materials show good potential for extending the service life of sheet metal forming tools. However, post-process methods currently used to improve coating surface quality are slow and expensive, especially on complex surfaces. A novel approach, demonstrated in this study, is the optimization of thermally sprayed coatings by roller burnishing. This process shows a high potential to not only reduce surface roughness and porosity, but also increase hardness even on free-formed surfaces. In the experiments, atmospheric plasma-sprayed CrC-NiCr coatings were produced and the burnishing process was performed on a CNC milling machine. Both the spraying and surface finishing processes are described and the results are presented and discussed.