bluuebunny/crossref_metadata_2025 huggingface dataset:
New Thermal Spray Powders for SOFC Components
Authors: Brüning B. , Gries B. , Nakadate H. , Zimmermann S.
Published: November 2022

In Solid Oxide Fuel Cells (SOFC), thermal spraying has become a preferred process in order to create functional and protective coatings. After a long period of research, SOFC is on the way to become a fully developed technology starting into mass production. Cost aspects of coating generation are becoming decisive. For this reason, thermal spraying has become the preferred process to apply e.g. Manganese Cobalt Iron Oxide (MCF) coatings which prevent the formation of volatile Cr oxides in the SOFC air supply and off-gas. Also Lanthanum Strontium Manganese Oxide (LSM) is now preferentially applied via thermal spraying. The presentation highlights the properties of commercially available spray powders for SOFC, their processing via different spray processes, and the properties of coatings achieved.
Nanostructured WC-Co Coatings Manufactured by Fine Powders (-10+2 µm) with Ultra-Fine Carbides (400 nm) by Means of HVOF
Authors: Tillmann W. , Hollingsworth P. , Baumann I. , Tolan M. , Paulus M.
Published: November 2022

Thermal sprayed WC-Co coatings are widely used for various industrial applications due to their high hardness and corresponding wear resistance. Recently, it has been reported by many researchers, that the use of agglomerated and sintered micron powders with submicron or nanosized carbides can provide the deposition of WC-Co coatings with enhanced or even superior mechanical and tribological characteristics. This can only be achieved, as long as optimized coating conditions adapted to the specific thermo-kinetic behavior of such powders are considered. However, the porosity in the coating morphology represents an inherent problem when using powders with conventional agglomerate size (10-50 µm) and high internal porosity. Consequently, a minimum coating thickness is often necessary to provide suitable wear properties, which reduces the shape or dimensional accuracy when applying such coatings to complex surfaces. In addition, a reduction in surface roughness of the coating cannot be accomplished by fine carbides, since large agglomerates are employed. In this study we used two different fine WC-12Co powders in the HVOF process to manufacture nanostructured coatings with high hardness, moderate toughness, low surface roughness and low porosity. The first powder is a fine agglomerated and sintered powder with particle size of -10+2 µm and carbides in the ultrafine range (400 nm) The second one consists in two loose mixtures of fine Co (Fisher grain size FSS = 3.5 µm) with (a) WC (FSS = 3.0 µm) and (b) WC (FSS = 0.8 µm). Statistical design of experiments (DoE) were utilized to determine main effects of spray conditions on coating properties. Mechanical properties, microstructure and the phase development has been correlated to the in-flight particle behavior. Phase analyses were performed by XRD using synchrotron radiation.
Understanding of Spray Coating Adhesion through the Formation of a Single Lamella
Authors: Goutier S. , Vardelle M. , Fauchais P.
Published: November 2022

Plasma spraying allows melting totally or partially micrometer sized particles, which flatten in about one is onto the substrate to build the coating by layering resulting solidified splats. The coating adhesion is essential and depends mainly on the behaviour of first lamellae in contact with the substrate. But in the plasma spray process about 108 particles/sec impact onto the substrate, and thus it is difficult to understand the role of the different spray parameters onto the coating quality. In order to get a better understanding of phenomena involved, it is necessary to study a single lamella formation. The experimental set-up is composed of a fast (50ns) two-colour pyrometer and an imaging system, comprising two fast (1 to 10 µs) CCD cameras triggered by the velocity signal of the particle in flight prior to its impact. This work is focused on alumina particles flattening onto stainless steel (304L) substrates preheated at different temperatures during different times.
Erosion Resistance of WC-12Co High Velocity Oxy-Fuel Coatings
Authors: Clavette P. L. , Nardi A. J. , Laube B. L. , Shi J. , Ely R. , Centolanza L.
Published: November 2022

In this work a number of different WC-12Co powder formulations were applied to coupons of steel using HVOF (high velocity oxy-fuel) and DSC (detonation spray coating) spray techniques. Two different HVOF guns and a super detonation gun (Super D-Gun ) were used to apply the coatings. The coated specimens were heat treated in an inert atmosphere at various temperatures in the range of 540°C -1000°C and subsequently characterized using optical microscopy, a Vicker’s microhardness tester, SEM (Scanning Electron Microscopy) and XRD (X-Ray Diffraction) to identify the phases generated. Additionally, in situ XRD was performed on a subset of these samples to explore the progression of the phase transformations as a function of temperature. Samples were also exposed to sand erosion with 20-30 mesh Ottawa sand at 825 feet per second to quantify performance. The work shows that the heat treatment and the transformation of amorphous metallic phases, WC and W2C to the η phase (Co6W6C) results in higher hardness and lower sand erosion rates.
Reducing the Cost of Thermal Barrier Coatings by Optimizing the Atmospheric Plasma Spray Process
Authors: Mihm S. , Duda T. , Thomas G. , Gruner H. , Dzur B.
Published: November 2022

The global economic growth has triggered a dramatic increase in the demand for resources over the last few years, resulting in steady price increases for energy and raw materials. In the gas turbine manufacturing sector, process optimizations of cost-intensive production steps involve a heightened savings potential and form the basis for securing future competitive advantages in the market economy. In this context, the atmospheric plasma spraying (APS) process for thermal barrier coatings (TBC) has been optimized. A constraint for the APS coating process optimization is the use of the existing coating equipment. Furthermore, the current coating quality and characteristics are not allowed to change in order to avoid new qualification and testing. Using experience in atmospheric plasma spraying and empirically gained data, the process optimization plan included the variation of e.g. the plasma gas composition and flow rate, the electrical power, the arrangement and angle of the powder injectors to the plasma jet, the grain size distribution of the spray powder and the plasma torch movement procedure like spray distance, offset and iteration. In particular, plasma properties (enthalpy, velocity, temperature), powder injection conditions (injection point, injection speed, grain size distribution,) as well as the coating lamination (coating pattern, spraying distance) are examined. The optimized process and resulting coating was compared to the current situation by several diagnostics methods. The improved process provides significantly lower costs by achieving the requirement of comparable coating quality. Furthermore, a contribution was made to a better comprehension of the atmospheric plasma spraying of ceramics and a method for future process developments was defined.
The Protectiveness of Thermally Grown Oxides on Cold Sprayed CoNiCrAlY Bond Coat in Thermal Barrier Coating
Authors: Manap A. , Ogawa K.
Published: November 2022

This paper presents the results of a study of the oxidation behavior of thermal barrier coating (TBC) with air plasma sprayed (APS) yttria-stabilized zirconia (YSZ) top coat and CoNiCrAlY bond coat deposited using low pressure plasma spray (LPPS) and cold spray (CS). The TBC is subjected to isothermal oxidation and creep tests at 900 ¢XC and evaluated using scanning electron microscopy (SEM), energy dispersive X-ray spectrometry (EDX) and transmission electron microscopy (TEM). The thermally grown oxide (TGO) developed in TBC with LPPS bond coat was composed of only α-Al2O3 and the TGO developed in TBC with CS bond coat is composed of α-Al2O3 and γ-Al2O3. Despite the presence of this metastable γ phase, the TGO in the CS specimens exhibits a dense microstructure and lower amounts of mixed oxides. The correlation between γ-Al2O3 and the formation of mixed oxides was investigated through the measurement of γ- Al2O3 thickness ratio and mixed oxides coverage ratio. It was found that the mixed oxides coverage ratio is inversely proportional to the γ- Al2O3 thickness ratio. Overall findings indicate that the oxidation behavior of the TBC with CS bond coat is superior compared to that of the TBC with LPPS bond coat.
Impact Conditions for Cold Spraying of Hard Metallic Glasses
Authors: List A. , Gärtner F. , Schmidt T. , Klassen T.
Published: November 2022

As compared to thermal spray techniques, cold spraying allows to retain metastable phases of the feedstock material like amorphous structures, due to lower process gas temperatures. Compared to crystalline metals, metallic glasses are brittle at ambient temperature but viscous at higher temperatures. Therefore, cold spray parameters must be optimized for conditions that allow softening of the amorphous spray material for successfully producing coatings. For this study, a FeCoCrMoBC metallic glass was used that in comparison to others offers advantages with respect to higher hardness, less costly feedstock powder and minimum reactivity with the environment. Necessary impact conditions were investigated to meet the window of deposition. According to calculations and cold spray experiments, neither the glass transition temperature Tg nor the melting temperature Tm can describe required conditions for bonding. Thus, a so called softening temperature between the glass temperature and the melting temperature had to be defined to calculate the critical velocity of metallic glasses. With respect to the bonding mechanism, impact morphologies could prove that a transition to viscous flow gets more prominent for harsher spray conditions. By sufficiently exceeding critical condition for bonding, coatings with rather dense microstructures can be processed at deposition efficiencies of about 70 %. The coatings have a hardness of 1100 HV 0.3, but the results also demonstrate that further work is still needed to explore the full potential for bulk metallic glasses.
Deposition of Composite LSCF-SDC and SSC-SDC Cathodes by Axial-Injection Plasma Spraying
Authors: Harris J. , Qureshi M. , Kesler O.
Published: November 2022

The performance of solid oxide fuel cell cathodes can be improved by increasing the number of electrochemical reaction sites. This is often done by controlling microstructures and using composite materials that consist of an ionic conductor and a mixed ionic and electronic conductor. LSCF (La0.6Sr0.4Co0.2Fe0.8O3-δ) and SSC (Sm0.5Sr0.5CoO3) cathodes were manufactured by axial-injection atmospheric plasma spraying (APS), and composite cathodes were fabricated by mixing SDC (Ce0.8Sm0.2O1.9) into the feedstock powders. The plasma power was varied by changing the proportion of nitrogen in the plasma gas. The microstructures of cathodes produced with different plasma powers were characterized by scanning electron microscopy and gas permeation measurements. The deposition efficiencies of these cathodes were calculated based on the mass of the sprayed cathode. Particle surface temperatures were measured in-flight to enhance understanding of the relationship between spray parameters, microstructure, and deposition efficiency.
LPPS Hybrid Technologies for Emerging Energy Applications – Recent Developments
Authors: Gindrat M. , Damani R.
Published: November 2022

Recent developments in hybrid low pressure thermal spray technologies such as Plasma Spray-Thin Film (PS-TF), PS-PVD, PS-CVD are being increasingly used to develop functional inorganic coatings and films for emerging high end energy applications. The requirements of such coatings and films are more highly specified than those of conventional plasma spray coatings. Successful film deposition therefore requires not only the development and application of novel operating parameters, but also goes hand-in-hand with tailored feedstock materials development. Targeted development by Sulzer Metco has allowed applications to evolve into fields where conventionally competitive manufacturing technologies would be applied; potentially enabling entirely new fields of plasma spray manufacturing to emerge. Such applications include corrosion protection and electrolytic films in SOFC, gas tight mixed electron and ion conducting membranes for gas separation and thin, transparent functional layers in photo-voltaic applications. This paper provides a brief overview of the status of developments of several high end emerging energy applications which are being developed using such hybrid low pressure plasma spray technologies.
Effect of Solution Chemistry on Solution Precursor Plasma Spray Deposition of LiFePO4
Authors: Chien K. L. C. , Golozar M. , Coyle T. W.
Published: November 2022

Solution precursor plasma spray (SPPS) is a thermal spray process in which deposits are formed by injecting solutions with the appropriate chemistry directly into the plasma. The deposits consist of grains or particles as small as ~20nm, and may be very porous or nearly dense, depending on the solution and deposition parameters. Recently, the potential of SPPS to deposit fine particle, porous coatings suitable for use as electrochemical electrodes for fuel cells and gas sensors has been demonstrated. This paper describes the efforts to deposit LiFePO4 coatings which may be of interest for Li ion battery electrodes with SPPS. In this case, along with the porosity, surface area, and microstructure of the deposited coatings, crystal structure also plays an important role in determining the performance of the LiFePO4 electrodes. Solution precursors with different solution chemistries containing lithium, iron and phosphorus ions are injected into hydrocarbon plasma issuing from a DC-arc torch. The effects of solution chemistries on coating morphologies and crystal structure were investigated. The results indicate that the porosity and crystal structure of the coatings can be tailored by selecting different additives.
The Efficient Management of Public R&D Funding in Order to Promote the Development of the Territory
Authors: Meneghetti S. , Giolli C. , Giorgetti A. , Scrivani A.
Published: November 2022

The current critical situation of the world economy pushes the companies to make themselves adaptable and to change their usual rigid behaviour in order to survive globalization of the market, to face the competition of the so called low cost countries (LCCs) and to overcame the current financial crisis. For the western companies, the possible way to face the movement of production to the LCCs, is to invest and increase the technological level of their products by means of effective R&D. This is even more valid for the Small and Medium Enterprises (SMEs) and is particular valid for the power generation sector. This paper addresses the policies adopted by the Public Administrations in the different countries in order to support the companies. The Public Administrations have the interest to support the companies not only in order to promote their own growth but, above all, in order to support the development of the territory where the company is located with the growth of the job numbers and the increasing of the subsuppliers activities. A review of the financial instruments available for companies in order to obtain financial help for research and innovation is provided, advantages and disadvantages are discussed. The focus is placed to the energy sector. An industrial case study is shown, related to a thermal spray shop dealing with gas turbine components, where the efficient and effective use of research allows the set up and the development of the company and also contributes to the surrounding market.
E-Learning Training in Plasma Spraying Area
Authors: Planche M.-P. , Costil S. , Montavon G.
Published: November 2022

The field of materials processing experiences many applications and developments in multiple industrial sectors where the used materials have to operate in most cases under extreme conditions (of temperature, pressure, reactivity of the environment, etc.). Under such conditions, he implementation of a system dedicated to the knowledge capitalization and ability concerning the use of technologies of the manufacturing processes remains today very important for the promotion of collective progresses in these fields. This is the main objective of this project which aims at promoting distance learning (e-learning) and at developing new knowledge-based systems to undergo scientific and technological skills. Currently, the research and education world is experiencing many urges of change, partly enabled and stimulated by the new possibilities offered by the Web. There is clear evidence that e-learning offers increased opportunities for training assessment leading to real benefits in terms of learner retention and achievement. This paper outlines the steps of the development of thermal spraying training supports using appropriate technologies in the thermal spraying field.
Supersonic Flame Sprayed Cylinder Liner Coatings and the Benefits of their Intrinsic Porosity
Authors: Manzat A. , Killinger A. , Gadow R.
Published: November 2022

To meet new regulations and specifications for internal combustion engines, new approaches to significantly decrease fuel consumption and emissions are needed. The deployment of tribologically functional coatings applied by supersonic flame spraying represent a promising technology for achieving these targets. Thermally sprayed coatings can help in improving efficiency of internal combustion engines by reducing the internal friction and improving the durability and wear resistance of the engine’s cylinder wall thereby facilitating extreme engine downsizing concepts. Thermal spraying is also capable of processing highly corrosion resistant materials like alloys and ceramics to enable the safe utilization of biofuels in modern combustion engines. In addition, specific surface structure of thermal spray coatings, including their intrinsic porosity, shows the benefit of reducing the friction by sustaining hydrodynamic friction even in spots with low relative movement, e.g. top and bottom dead center. On top, the open surface porosity can reduce the oil consumption and thereby decrease the polluting emissions of internal combustion engines. The thermally sprayed coatings were applied using HVOF and HVSFS processes deploying various materials, including novel nanostructured powders. The coated cylinders and engines have been compared to state-of-the-art components with respect to friction coefficient, wear and oil consumption.
Friction Improvement of New Generations of Engines by PTWA Cylinder Bore Coating and New Piston Rings
Authors: Schramm L. , Verpoort C. , Schwenk A. , Bobzin K. , Bagcivan N. , Schläfer T. , Theiß S. , Yilmaz K.
Published: November 2022

In an effort to inhibit a climate change, the European Union has decided to reduce the CO2 emissions by approx. 30% by year 2020, as compared to the level of emissions in year 1990’s. In general, traffic is responsible for 20% of all CO2 emissions and 84% of those emissions result specifically from road traffic. In accordance with the present targets of the CO2 emission reduction the automotive industry has to meet strict regulations. The strict emission goals can only be reached by weight reduction of the vehicle and by an improved efficiency of engine and drive train. Close to 50% of the friction losses in a combustion engine result from the interaction between the piston ring and the cylinder bore surface. Therefore the cylinder bores as well as the piston rings were coated with new, low-friction materials. The friction behaviour was characterized in linear reciprocating tribometer-test in order to identify the best combination of bore and ring coatings.
Thermal Coating of Cylinder Bores Needs Approved Processes of Pre and Post Treatment
Authors: Flores G.
Published: November 2022

The application of thermal coatings in cylinder bores is depending on above all functionality, process reliability and economy of pre treatment of the substrate surfaces. Different removing processes like water jetting or sand blasting are increasingly substituted by mechanical machining. Thereby great importance is attached to functionality and degree of automation. For an assured engine function, high bond strength is required. The roughening process as a modified cutting machining meets the requirements of modern production lines. Removing overspray after thermal coating by a water jetting process, is a further contribution for a higher automation degree. The final machining of sprayed surfaces is effected by a multi stage honing process. The composite structures of thermal coated layers call for high performance diamond abrasives. The finished functional cylinder surface comprehends cavities of thermal coated layer and smooth honing pattern. The technological description of roughening and honing, the process components as well as the machining results will be presented. Pre and post treatment are essential processes, which enable the application of high performance thermal coating materials in friction optimized combustion engines.
Performance Analysis and Modeling of Thermally Sprayed Resistive Heaters
Authors: Lamarre J.-M. , Marcoux P. , Perrault M. , Abbott R. C. , Legoux J.-G.
Published: November 2022

Many processes and systems require hot surfaces. These are usually heated using electrical elements located in their vicinity. However, this solution is subject to intrinsic limitations associated with heating element geometry and physical location. Thermally spraying electrical elements directly on surfaces can overcome these limitations by tailoring the geometry of the heating element to the application. Moreover, the element heat transfer is maximized by eliminating the air gap between the heater and the surface to be heated. This paper is aimed at modeling and characterizing resistive heaters sprayed on metallic substrates. Heaters were fabricated using a plasma-sprayed alumina dielectric insulator and a wire flame sprayed iron-based alloy resistive element. Samples were energized and kept at a constant temperature of 425°C for up to four months. SEM cross-section observations revealed the formation of cracks at very specific locations in the alumina layer after thermal use. Finite element modeling shows that these cracks originate from high local thermal stresses and can be predicted according to the considered geometry. The simulation model was refined using experimental parameters obtained by several techniques such as: emissivity and time-dependent temperature profile (infra-red camera), resistivity (four probe technique), thermal diffusivity (laser flash method) and mechanical properties (micro and nanoindentation). The influence of the alumina thickness and the substrate material on crack formation was evaluated.
Effect of Suspension Characteristics on Microstructure of Suspension Plasma Sprayed SiC Submicron Coatings
Authors: Mubarok F. , Puranen J. , Vuoristo P. , Johnsen R. , Espallargas N.
Published: November 2022

Thermal spraying of pure SiC is difficult due to decomposition issues at elevated temperatures. However, the development of suspension plasma spray opens a new path to investigate the deposition of this material since the liquid carrier can hinder this phenomenon. The present work investigates a new route for producing SiC submicron structured coating by suspension plasma spraying (SPS). Classical SiC manufacturing routes using suspension (i.e: spray drying, tape casting) are studied regarding their feasibility to be used on suspension plasma spraying. Aqueous-based suspensions containing 10 wt.% SiC powder (0.60 µm) along with sintering additives are dispersed and stabilized. Both suspensions are sprayed on martensitic stainless steel substrate (AISI 440C) to achieve finely structured and dense coatings. Digital image analysis, X-ray diffraction and scanning electron microscopy are utilized to characterize the coating microstructures. Their dependency on suspension characteristics and spray operation parameters are discussed with respect to the final coating performance.
Silicon Carbide Based Plasma Sprayed Coatings
Authors: Tului M. , Giambi B. , Pulci G. , Valente T.
Published: November 2022

Coatings containing up to 65 volume % of silicon carbide were deposited by plasma spray. Potential applications can be found in the protection of CMC (Ceramic Matrix Composite) against wear and high temperature oxidation. It is well known that SiC can not be deposited by thermal spray because it decomposes before melting. To face this problem, a mixture of SiC and ZrB2 was deposited, since those two compounds form an eutectic phase, at a temperature lower to the one of SiC decomposition. Coatings microstructure was characterised by XRD, SEM, and EDS, confirming the presence of SiC in the deposited layer and the formation of the eutectic phase during spraying. Samples of the coatings were exposed in air at high temperature, in the range between 1373 and 1873 K. The oxide scale was investigated by means of SEM and EDS. It was constituted by a SiO2 layer, which includes islands of ZrO2. Test results showed the good potentiality of the material investigated to be used as a protection against the high temperature oxidation.
Synthesis of Porous Super-Capacitor Electrodes using the SPPS Deposition Technique
Authors: Golozar M. , Chien K. , Coyle T. W.
Published: November 2022

Electrical double-layer capacitors (EDLCs) owe their large capacitance to high specific surface area carbon-based electrode materials adhered to a current collector via an adhesive. However, recent studies attribute greater electrical energy storage capacity to transition metal oxides/nitrides: a new generation of electrode materials for use in super-capacitors with mixed double-layer and pseudo-capacitive properties. Solution Precursor Plasma Spray (SPPS) deposition is a technique that allows coatings to be fabricated with fine grain sizes, high porosity levels, and high surface area; characteristics ideal for application as transition metal oxide super-capacitor electrodes. A liquid injection apparatus was designed to inject the liquid into the DC-arc plasma and to investigate the effects of various operating parameters such as spray distance, solution concentration and solution flow rate on the chemistry and surface topography of the deposits. Understanding and controlling the evolution of the precursor solution in the DC-arc plasma jet is crucial in producing coatings of the desired structures. DTA/TGA, SEM, XRD, and electrochemical analyses performed to characterize the coatings will be discussed, and the potential of the deposits for use in super-capacitors will be assessed.
Deposition of Nickel-Yttria Stabilized Zirconia and Nickel-Samarium-Doped Ceria by Solution Precursor Plasma Spraying for Solid Oxide Fuel Cells
Authors: Metcalfe C. , Lay E. , Kesler O.
Published: November 2022

Nickel – yttria stabilized zirconia coatings and nickel – samaria doped ceria coatings were fabricated by solution precursor plasma spraying using the Northwest Mettech Axial III plasma torch. Three sets of plasma spray parameters were used resulting in comparatively low, intermediate, and high plasma powers of 63 kW, 102 kW, and 152 kW, respectively. The high and low power conditions resulted in powdery type coatings with poor adhesion to the substrate and between particles. The intermediate power conditions resulted in harder coatings with improved adhesion and electrical conductivity.
Influence of Boron Content on Microstructure and Properties of Wire-Arc Sprayed Fe-Based Coating
Authors: Zhou Z. , He D. Y. , Zhang G. Z. , Li R. , Jiang J. M.
Published: November 2022

A series of FeCrBCSi coatings were prepared by two-roll wire-arc spraying to investigate the influence of the boron content on the microstructure and properties of the coatings. Microstructural studies show that the as-deposited coatings present a dense layered structure with the porosity around 3%, and are primarily composed of a composite structure of amorphous phase and nanocrystalline phase. It is found that the addition of boron content within the composition range examined exhibits a significant effect on the phase component, as well as the microhardness and wear resistance of the coatings. The optimal composite phase structure, in terms of higher amorphous fraction and lesser nanocrystalline size distribution, leads to the relatively best performance of the coating with 26% boron added. The relative wear resistance of this coating is about 18 and 4 times higher than that of the Q235 steel and commercially available SHS 7170 coating, respectively, therefore wire-arc sprayed FeCrBCSi coating could be an effective and economic approach to withstand wear environment.
Investigation of Heat Treatment on Cold Sprayed Aluminum Coatings on Magnesium Substrates with Different Status
Authors: Bu H. , Jodoin B. , Yandouzi M. , Lu C.
Published: November 2022

Large pure aluminum powders were deposited on as cast-, T4- and T6-AZ91D magnesium substrates using cold spray. Heat treatment was applied to the coated components under vacuum at 400°C for different holding time. The effects of the heat treatment on the microstructure as well as the coating/substrate adhesion strength were investigated. Thick (~ 400µm) and dense (<1% porosity) Al coatings have been obtained on the three different substrates. During heat treatment, Mg17Al12 (β) and Al3Mg2 (γ) intermetallic phases were formed at the Al/Mg interface and the thickness of the intermetallics layers increased with the holding time. No significant thickness difference of the intermetallics layers were observed on as cast- and T6-AZ91D substrates, while thicker layers took place on the T4- substrate. It is believed that the higher Al concentration within the T4-AZ91D material could be beneficial for intermetallic growth because less enrichment is required to reach the critical level for intermetallic formation in the substrate. Shear strength tests were performed on the as sprayed and after heat treatment coatings. The results revealed lower adhesion strength in the samples after heat treatment than the as sprayed ones which is attributed to the presence of brittle intermetallics layers at the coating/substrate interface.
Sliding Wear Behavior of HVOF Sprayed Coatings, Suitable for Piston Rings Application
Authors: Houdková Š. , Kašparová M. , Zahálka F.
Published: November 2022

The HVOF sprayed wear resistant hardmetal coatings with favourable sliding properties are suitable for increasing the lifetime of sliding applications, such as pistons of combustion engines, pumps and other hydraulic devices. In practice, the coatings face the problem of their interaction with other media, in the case of sliding wear usually lubricants. In the paper, the friction properties of five different HVOF sprayed coatings are evaluated by pin-on-disk test according to ASTM G-99 under dry and lubricated conditions and lubricated block-of-ring test according to ASTM G77. Several types of lubricants designed for combustion engines were used to compare their influence on coatings sliding wear behavior. Based on the results, the suitability of coatings for the application on the engines parts is discussed and the effect of counterpart material and different types of lubricants on the coefficient of friction and coatings wear rate is analyzed. It was confirmed, that the CrC-based coating are more suitable for the application under the condition corresponding to combustion engines, e.g. elevated temperature and steel counterpart, than the WC-based coatings. From the group of CrC-based coatings, the superior behavior was observed at the CrC-CoNiCrAlY coating, the matrix material of which offers further enhancement of the sliding wear behavior.
Electrical Properties of Al2O3-TiO2 Plasma Sprayed Coatings for Electrode of Corona Discharge
Authors: Abukawa S. , Takabatake T. , Namba Y. , Tani K.
Published: November 2022

Thermal sprayed ceramic coatings are well used as the electrode of corona discharge treatment in order to modify the surface of many kinds of films and papers due to its superior durability and adaptability. Some kinds of Al2O3-TiO2 were sprayed by APS on the parallel plate electrodes, and output power of corona discharge generated by the electrodes was measured by using Sawyer-Tower circuit. In addition, discharge output power was calculated with an equivalent circuit of corona discharge. By comparing them, effects of the electrical property of the coating on discharge was researched. As a result, the electrostatic capacitance of the coatings influences the impedance of the whole circuit, and higher relative permittivity of the coating brought higher output power in a constant voltage.
Innovative Testing Method for Interconnected Porosity of Thermally Sprayed Ceramic Coatings Using Electroplating
Authors: Harada Y. , Takatani Y. , Tani K.
Published: November 2022

New concept and method of testing for the interconnecting porosity of thermally sprayed nonconductive ceramic coatings is proposed. This process is useful to differentiate the open porosity from the closed porosity. Thermally sprayed ceramic coating with metallic substrate is plated, and the intergranular gaps in the coating are filled by deposited metal. Typically, 304 stainless steel substrate deposited with atmospheric plasma sprayed alumina coating is immersed in copper(II) sulphate bath, and electroplated. Inward of the alumina coating, plating solution penetrates toward the interface of coating/substrate via interconnected porosity, and attains the coating-substrate interface to deposit metallic copper. Deposit of copper is gradually grown up along the coating intergranular. The exposure of deposited copper on the coating surface can be visible. Because these phenomena occur only in the interconnected pore structure, it is easy to differentiate the interconnected porosity from the closed porosity. Also the proposed process suggests the unprecedented possibility of manufacturing method of three-dimensional structure of thermally sprayed ceramic coating.
Modern Applications of the Low Pressure Cold Spray
Authors: Kashirin A. , Klyuev O. , Buzdygar T. , Shkodkin A.
Published: November 2022

The main advantage of the cold spray process is minimal influence on the substrate properties with sufficiently high bond strength. This advantage allows metal coating to be applied to the specific objects which were never subjected to the thermal spray process. The examples of the low pressure cold spray application to the glass objects, magnet sensors and electronic elements are presented and discussed.
Annealing Effect on the Intermetallic Compound Formation of Cold Sprayed Fe/Al Composite Coating
Authors: Wang H.-T. , Li C.-J. , Ji G.-C. , Yang G.-J.
Published: November 2022

In this paper, an iron/aluminum composite coating was prepared by cold spraying using iron and aluminum powder mixture and then annealed to aim at forming iron aluminides by suitable annealing treatment. The annealed coating was characterized using X-ray diffraction (XRD) to determine the coating phases and scanning electron microscope (SEM) with an EDXA energy dispersive spectroscopy (EDS) to examine the coating microstructure evolution. Results showed that the Fe2Al5 intermetallic layer along some regions of the aluminum-iron boundaries forms after annealing at a temperature of 450°C, where true metal to metal contact had occurred. The content of Fe2Al5 phase increased with raising annealing temperature. It was observed that some cracks were developed in Fe2Al5 layer after annealing treatment at a high temperature of 600°C.
Effect of In-situ Softening on the Deposition Behavior of Particles by Controlling Gas Stream Traversing During Cold Spraying
Authors: Yang G.-J. , Wang J. , Li C.-J. , Zhang Q. , Li C.-X.
Published: November 2022

The deposition behavior of particles during cold spraying is determined by plastic deformation of both substrate and impinging spray particles. In this paper, the in-situ heating and subsequent softening of the local substrate were examined to reveal their influence on the deposition behavior of spray particles and the microstructure and property of the cold-sprayed 316L stainless steel and copper coatings. Results show that the temperature of the substrate surface, where the spray gas stream and high velocity particles were projected on, increased to 300°C when the gas temperature was 500°C. Such effect is referred to as the in-situ substrate heating. The in-situ heating of the substrate surface was enhanced with the decrease in the gun nozzle traverse speed. With the decrease of nozzle traverse speed from 100 to 20 mm/s, the relative deposition efficiency significantly increased and the porosity of cold-sprayed 316L coatings decreased from 5.6% to 2.5%, and the micro-hardness of the coatings increased from 283 Hv to 351 Hv. The influence of the nozzle traverse speed on the microstructure and property of cold-sprayed coatings is discussed based on the influence of the in-situ heating and softening effect of substrate surface on its deformation behavior and particle deposition upon the impact of spray particles. The in-situ substrate surface heating is proposed as an essential processing parameter as a function of gun traverse speed during cold spraying.
Thermal Analysis of Cold-Sprayed Copper Coatings
Authors: Alishir F. , Nekoumanesh H. , Assadi H.
Published: November 2022

In this study copper coatings were deposited by cold spraying, under different spraying conditions. Microstructure of the coatings was investigated by optical and scanning electron microscopy. Additionally, differential scanning calorimetry (DSC) and thermal gravimetric analysis were used to examine the quality of the coatings, especially with regards to the extent of the bonded area between the particles. The DCS results indicated exothermic reactions at certain temperatures, which revealed correlations with the spraying conditions and some of the observed microstructural features. In view of these results, it is concluded that thermal analysis can be utilized reliably to assess the quality of coatings, and in particular, to examine the fraction of bonded areas in cold-sprayed deposits.
Influence of Deposition Conditions and Heat Treatment on Tensile Strength of Cold Spray Aluminium Coatings on Al2O3 and AlN Substrates
Authors: Kuemmel S. , Grund T. , Loeschner P. , Wielage B.
Published: November 2022

A novel process to produce dense, well adherent aluminium coatings on ceramic materials is cold gas spraying (CGS). The mechanical, physical and chemical processes leading to the bonding of cold-sprayed coatings on ceramic substrates have only been described rudimentarily. A survey of the literature on adhesion mechanisms of cold spray coatings is given, where influences on bond strength are discussed and parameters identified. Using the example of coating Al2O3 and AlN substrates with pure aluminium via cold gas spraying, a process and substrate parameter variation is presented. A significant raise in tensile coating strength was seen at elevated substrate temperatures and after subsequent annealing. Tensile strength also depended on chemical composition and roughness of the substrate. The results allow the discussion of the bonding mechanisms of cold spray aluminium on ceramic substrates as a function of deposition and annealing parameters.
Interface Reactions in Composite Coatings Deposited by Cold Spray and Detonation Spraying
Authors: Leshchynsky V. , Bielousova O. , Ryashin N. , Yadroitsava I. , Smurov I.
Published: November 2022

Deposition of Metal Matrix Composites (MMC) has been the subject of extensive research in the recent years. The desired functional properties of a composite coating can be achieved by analyzing and controlling the major structural processes taking place during deposition. The latter are reactions at the particle-particle and particle-substrate interfaces which can be controlled by applying advanced spraying technologies. Cold Spray (CS) and Computer Controlled Detonation Spraying (CCDS) are well-proven reliable methods for deposition of composite coating. The energy (thermal and kinetic) imparted to the particles-in-flight by CS and CCDS allows initiating interface reactions that will define distinct properties of the deposited composite layers. The applied spraying technologies are characterized by different ratio of thermal-to-kinetic energy that results in different conditions of the compounds interaction. The objective of the present study is to define the effect of CS and CCDS technologies on structure and properties of Al-Ti-based composite coatings by analyzing intermetallic reactions occurring during the process. It is shown that both CS and CCDS composites present differently sized zones of interfacial reactions.
Corrosion Behaviour of HVOF-Sprayed Ni-20Cr Coating in a Molten Salt Environment at 900°C
Authors: Kaushal G. , Singh H. , Prakash S.
Published: November 2022

HVOF thermal spray technique was used to deposit Ni-20Cr coating on a ASTM-SA213-T22 boiler steel. The corrosion behaviour was investigated for the uncoated and HVOF spray Ni-20Cr coated boiler steel in a molten salt environment (Na2SO4-60%V2O5) at 900°C for 50 cycles. Each cycle consisted of 1 hour heating in the silicon carbide tube furnace followed by 20 min cooling in air. Mass change technique was used to approximate the kinetics of high temperature corrosion. The uncoated sample suffered intensive spallation along with a significant mass gain as compared to the coated sample. The exposed specimens were characterized by X-ray diffraction [XRD] and scanning electron microscopy/energy dispersive spectroscopy [SEM/EDS]. It was observed that HVOF sprayed Ni-20Cr coating was suitable to provide high temperature corrosion resistance to the given steel in the said(salt) environment.
Microstructure and Properties of FeAl Coatings Prepared by APS, LPPS and HVOF
Authors: Yang D.-M. , Tian B.-H. , Gao Y.
Published: November 2022

The FeAl intermetallic compound coatings were sprayed by low pressure plasma spraying (LPPS), air plasma spraying (APS) and high velocity oxy-fuel spraying (HVOF). The influence of three kinds of thermal spraying processes on the microstructure, microhardness, elastic modulus and fracture toughness of coatings were investigated. The results showed that the APS and HVOF coatings exhibited similar microhardness, about 540HV0.3, which is much lower than that of LPPS coatings, 860HV0.3. The elastic modulus measured for APS, HVOF and LPPS coatings using Knoop indentation were 96, 84, 176GPa, respectively. The APS coatings were also observed to have lower elastic modulus values in the in-plane direction than those in the perpendicular direction, as a result of microcracks scattered within the coatings. In fracture toughness tests, the LPPS coatings revealed the lowest fracture toughness, as compared with other two spraying processes, indicating low porosity and crack levels are related to low fracture toughness. From these results, it appeared that potential improvements to certain mechanical properties can be achieved using low pressure plasma spraying process.
Suppressing Oxidation of Ni-Cr Alloy with Addition of Si, B and C in Atmosphere Plasma Spray Process
Authors: Zeng Z. , Sakoda N. , Tajiri S. , Kuroda S. , Komatsu M.
Published: November 2022

Oxidation is a serious issue for thermally sprayed alloy coatings, especially in atmospheric plasma spray (APS) process, by which it is believed to be impossible to obtain alloy coatings with low oxide content. Oxidation behavior of Ni20Cr alloy and NiCrSiBC alloy in APS were compared by evaluating collected in-flight particles and sprayed coatings in our previous study. The results clearly show that the oxide content in the in-flight particles and coating of NiCrSiBC alloy was significantly lower than that of Ni20Cr alloy. In the present study, further study of the surface oxide layer of NiCrSiBC coating was carried out by TEM, which showed 10 nm thick oxygen enriched layer. The effects of particle temperature and velocity on the oxidation of the NiCrSiBC alloy were investigated. It was found that increasing particle temperature and velocity did not affect the oxidation of inflight particle of the NiCrSiBC alloy but significantly increased the oxidation after particle impacting substrate. The results are discussed in conjunction with effectiveness of preferential oxidation of Si, B, C and simultaneous vaporization of the formed oxides on suppressing in-flight oxidation and influence of a large amount of sub-particles produced upon impacting substrate on oxidation characteristics when increasing plasma power.
New Method of Generating Robot Trajectory on Complex Geometric Workpiece
Authors: Cai Z. , Deng S. , Liao H. , Coddet C. , Zeng C.
Published: November 2022

Off-line programming technology is frequently used in advanced robot assisted thermal spraying process, such as ABB RobotStudio, which offers excellent functions to simulate the real working environment of robot in order to test the robot trajectory. It also provides the add-in programs to make the simulation easier. ANSYS is an engineering simulation software which offers the function of modeling analysis with grids. The mesh on the surface of workpiece represents a layer with good coverage that can be the reference to create robot trajectory on it. This study provides a new ideal to combine those two technologies (or software) in order to realize the auto-generation of the robot trajectory for thermal spraying. Based on the function of the add-in program, we can transfer the data between RobotStudio and ANSYS using C# programming and then create the trajectory according to the operation parameters. Some experiments have shown that this method can effectively reduce the time required for robot programming.
Shock-Wave Induced Spraying: Modeling and Physics of a New Spray Process
Authors: Karimi M. , Rankin G. W. , Jodoin B.
Published: November 2022

The Shock-wave Induced Spray Process (SISP) is a method of applying coatings of various metallic-based materials onto a wide range of different substrates. It utilizes the kinetic and thermal energy induced by a moving shock-wave to accelerate and heat powder particles. A transient axisymmetric model for the process is developed using Fluent. The model is validated with reference to a simplified one-dimensional approximation of the flow field. Values of pressure, axial velocity, Mach number, as well as static and total temperature are carefully examined. It is found that a zone develops in the flow that experiences elevated levels of temperature and velocity simultaneously. This is the main distinction between SISP and traditional CGDS processes. The effects of varying supply pressure and temperature on these flow variables are investigated in detail. Additionally, the effect of changing the driving gas type is investigated using air and helium as examples.