bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Simulation of the Thermo-Mechanical Behaviour of Thermally Sprayed Abradable Coatings
Authors: Seichepine J. , Faraoun H. , Peyraut F. , Chandler P. , Coddet C. , Sporer D. , Hertter M. , Sellars C.
Published: September 2022

The newly designed abradable coatings are usually validated by rig tests, where samples are rubbed by the contact of a dummy blade with given running speed and incursion rate, simulating actual working conditions in an aircraft engine. The aim of this work was to develop a model of abradable coating rig tests, allowing extensive studies on the influence of coating properties and test conditions on the thermal behaviour of the system. The proposed model includes several steps implementing different numerical tools. Firstly, a relevant structural description of an abradable coating is obtained from micrographs, using an original image analysis route. FE (Finite Element) calculations based on this description allow then to estimate the coefficients of an anisotropic elastic law of mechanical behaviour. Furthermore, a plasticity law is deduced from a FE simulation of the material HR15Y hardness. These parameters are used as input of a FE simulation of a single blade-to-coating rubbing hit, resulting in calculated stresses and temperatures. Finally a global approach of the complete abradability test, based on the results obtained from the simulation of a single hit and on various assumptions, provides predictions of the blade and coating temperature variations versus time during a complete abradability test.
Processing and Properties of Hybrid YSZ Coating Deposited by Thermal Plasma Directed Vapor Deposition
Authors: Lavaud T. , Vardelle M. , Fauchais P. , Menuey J.
Published: September 2022

The aim of this study is to develop for thermal barrier applications a new process in which coatings exhibit properties between those of APS and EBPVD. This process includes two conventional D.C. plasma torches working in a chamber whose pressure can vary between 30 and 100 kPa. Micro-sized yttria stabilized zirconia powders are injected in both plasma jets to vaporize them, at least partially, and produce finely-structured coatings from vapor and micro-droplets deposition. The torch arrangement allows separating the vapor and the very small particles (less than 1 µm) from the partially vaporized bigger ones. The diagnostics are based on optical emission spectroscopy, pyrometry, imaging of particles trajectories and coating microstructural characterization.
Microstructural Characterization of Plasma-Sprayed YSZ/AI2O3 Thermal Barrier Coatings
Authors: Saral U. , Toplan N.
Published: September 2022

In the present study, yttria-partially-stabilized zirconia (YSZ)/Al2O3 coatings, which are used for jet engines, gas turbines and diesel engines were coated with thermal barrier coatings (TBCs) to provide high thermal resistance, reduce the metal surface temperatures, and increase component durability. The effect of alumina addition from 0 to 80 wt% on the properties of plasma sprayed YSZ coatings was investigated. The coatings were produced using a METCO 3MB plasma spray gun on stainless steel and graphite substrates. Scanning electron microscopy (SEM) was used to analyze the microstructures of the coated samples. The microhardness was investigated depending on the alumina contents. Vickers hardness on cross section of coatings was observed to increase with the increase in alumina mixing ratio. The presence of alumina phase commonly improves the mechanical properties of YSZ.
Tools for Online Monitoring of Failure Evolution of Thermal Barrier Coatings in Gas Burner Thermal Cycling Rig Environment
Authors: Mack D.E. , Vaßen R. , Stöver D.
Published: September 2022

One major shortcoming of thermal barrier coatings applied to gas turbine components is the spallation of the ceramic coating under mechanical stress developing during thermal cycling environments. In order to study the evolution of failure and the expectancy of lifetime under realistic conditions cycling burner rig tests are a well established matter of choice. In the same way the techniques of acoustic emission (AE) testing and infrared (IR) thermography have been widely proofed to provide insight to microscopic crack formation and localization of hidden delaminations, respectively. Both techniques can be utilized to record the evolution of microscopic and macroscopic defects in advance to the apparent failure. Indirectly, this knowledge allows to verify and to improve lifetime models. The aim of this study is to expand the use of AE and IR testing as a rugged in-situ monitoring tools for combustion driven cycling rigs and to provide spatial resolved information on thermal load and failure evolution of the TBC in those tests. For a successful application to an experiment using a gas fired and air cooled burner rig some it is necessary to overcome some limitations which are mainly due to the high level of interfering signals under those experimental conditions.
Thermal Conductivity of AlSi/Polyester Abradable Coatings
Authors: Bolot R. , Seichepine J.L. , Vucko F. , Coddet C. , Sporer D. , Fiala P. , Bartlett B.
Published: September 2022

Abradable seals are used in aerospace applications to control the overtip leakages between the blades of an engine rotor and its static parts. To achieve the combination of properties required, these seals have been developed with thermally sprayed coatings and are generally elaborated from a range of two or three phase powder mixtures. In the present study, the thermal conductivity of thermally sprayed AlSi/Polyester abradable coatings produced with Metco 601 NS and Durabrade 1605 powders was measured and investigated using finite element and finite difference methods based on two-dimensional structures obtained from micrographs. The computed values were compared to the experimental results.
Valence Band XPS and FT-IR Evaluation of Thermal Degradation of HVAF Thermally Sprayed PEEK Coatings
Authors: Patel K. , James B.J. , Hyland M.M.
Published: September 2022

Coatings of poly(ether-ether-ketone) (PEEK) have been produced using the high-velocity air fuel (HVAF) thermal spray technique. These coatings have been produced at 50 and 100 mm nozzle lengths and 200, 300, and 400 mm gun-to-substrate distances on stainless steel 304 substrates. The techniques used to characterize and determine the extent of thermal degradation of the PEEK coatings were valence-band XPS and FTIR-ATR. Valence-band XPS showed that, in general, minimal degradation of the PEEK occurred during the HVAF thermal spraying process. FTIR-ATR results showed that more surface degradation of the PEEK coating occurred at the 200 mm gun-to-substrate distance for both nozzle lengths than at the larger gun-to-substrate distances. Specifically, absorption bands appeared at 2918 and 2850 cm-1, which correspond to alkane –CH2– asymmetric stretching modes. The resolution of the 672 cm-1 peak, which corresponds to C–H vibrations on the phenyl ring, increased from one to two peaks in the spectra of the 200 and 300 mm gun-to-substrate runs. This indicates a structural change in the phenyl ring, possibly indicating a change in the extent of crystallization of the PEEK polymer.
Spraying Process, Microstructure, and Relaxation Stress Behavior of Cylindrical Standalone YSZ Coatings with and without Segmentation
Authors: Karger M. , Vaßen R. , Stöver D. , Petorak C. , Trice R.
Published: September 2022

Segmentation cracked coatings are promising candidates for thermal barrier coatings (TBC) because of their high strain tolerances. By atmospheric plasma spraying (APS), cylindrical stand-alone YSZ coatings with and without segmentation cracks were fabricated. The diameter of the tubes was 10 mm, and the thickness of the coatings approximately 1 mm. The segmentation crack densities were in the range up to 3.5 cracks/mm, while the porosity amounted for all coatings between 5% and 7%. Further details of the spraying process and the obtained microstructures will be given and discussed. The samples were tested in an uniaxial high temperature compression rig to measure the stress relaxation. The comparison of the stress relaxation measurements yielded a different performance of segmented and non-segmented coatings with advantages for the cracked ones. It was observed that the cracks increase the resistance to stress relaxation.
Phase Stability and Structure of Conductive Perovskite Ceramic Coatings by Thermal Spraying
Authors: Lagerbom J. , Nikkilä A.-P. , Kylmälahti M. , Vuoristo P. , Kanerva U. , Varis T.
Published: September 2022

Perovskites are considered as potential materials in solid oxide fuel cells (SOFC) for different reasons at different parts of the fuel cells. Perovskites such as La0.8Sr0.2MnO3 (LSM) and other compositions are electrically conductive which is necessary for SOFC applications. One possible application is protection coating for interconnect plates (bipolar plate) to avoid chromium oxide evaporation from the surface of ferritic stainless steel. Different commercial and experimental perovskite powders were sprayed by plasma and HVOF spraying under different spray conditions. Spraying of pervoskites was found to be challenging and required careful parameter optimization in both spray methods. Microstructure and phase structure of the coatings were investigated. A very fine crack structure, possibly caused by low mechanical strength and low ductility of the compounds, was easily formed in coatings prepared by plasma and HVOF spraying. Spraying method, parameters and spraying atmospheres were found to affect the stability of the perovskite compounds due to low chemical stability at high spray temperatures. Oxygen deficiency or oxygen surplus was concluded to cause distortion of the compounds crystal structure, causing thus shifting of XRD-peaks due to change of lattice parameters. Electric conductivity was affected by the crystal structure.
Anode SOFCs Produced by Suspension Plasma Spraying: Interests and Prospects
Authors: Marchand O. , Rampon R. , Bertrand G.
Published: September 2022

In order to achieve Solid Oxide Fuel Cells (SOFC) with reduced costs, the atmospheric plasma spray process (APS) could be an attractive technique. However, it is difficult to produce plasma sprayed coatings with the appropriate porosity for the electrodes and full density for the electrolyte. The spray process has been adapted by providing a suspension or a powder as feedstock material combined with optimized spray conditions to manufacture SOFC layers with required compositions, microstructures and properties. Suspensions or powders were injected in a plasma jet originating from a conventional torch (F4) implementing external devices. By using optimized suspensions of nickel oxide (NiO) and yttria stabilized zirconia (YSZ) in ethanol, porous anodes have been produced with thicknesses around 50 µm. By the same way aqueous suspensions of yttria stabilized zirconia (YSZ) powders have been prepared to achieve a fine layer as electrolyte to produce the first half cells and the porous cathode layers based on lanthanum strontium manganite (La0.8Sr0.2MnO3 or LSM) have been manufactured by conventional atmospheric plasma spraying of powders.
Cold Spraying Technique to Process Nanomagnetic Coatings
Authors: Cherigui M. , Fenineche N. , Liao H. , Coddet C. , Li W. , Ji V.
Published: September 2022

The cold gas dynamic spray process, or cold spraying (CS), represents a radical departure from conventional thermal spray (TS) methods in that the deposition process relies purely on kinetic energy rather than on a combination of thermal and kinetic components. A potential advantage of this process over TS is the ability to generate dense coatings retaining initial material chemistry and phase composition with a very little oxidation. Also, low temperature process (no bulk particle melting) eliminates solidification stresses and enables thicker coatings. However, hard brittle materials like ceramics can not be sprayed without using ductile binders. In this study, magnetic alloys such as FeSiBNbCu also called Finemet and FeSiBNbCu-Al with various percentages of Aluminum coatings were synthesized using cold spray technique in order to produce ferromagnetic materials. Ultra-fine grain coatings were obtained using FINEMET nanostructured powders mixed with Aluminum as ductile binder in order to improve adherence. Magnetic measurements revealed a soft magnetic character for all the powders and the coatings. 25% of Al was considered as ideal to produce a homogenous coating with suitable magnetic properties.
Development of Ceramic Composite Coatings with Titania Nanofibers
Authors: Watanabe M. , Chivavibul P. , Komatsu M. , Kuroda S.
Published: September 2022

In recent years, nano alumina/titania ceramic composite coatings have been investigated and exhibited very attractive properties in several mechanical applications such as wear resistance. One of the reasons for significant improvement of those coatings properties is considered to be “nanostructure” preserved in the coating during depositions. Thus, it is of interest to introduce nanostructure with high aspect ratio into coatings and to investigate the effects on the coating properties, especially fracture properties. In this study, alumina/titania composite powders were fabricated by spray dry procedure, which consist of the alumina nano particle (~50nm) and the titania nano fibers (diameter 100~200nm, length 2~3µm). The developed powders were sprayed by APS process. The deposited coatings contain fibrous titania structures which were not melted during deposition. Fracture resistance was evaluated as a function of a crack length by Double Cantilever Beam (DCB) Test for the coatings fabricated under various spray conditions and corresponded to the microstructure.
Preparation and Characterization of Nickel Clad h-BN Composite Powders for Abradable Sealing Coating
Authors: Liu J. , Yang Z. , Wang L. , Yan S. , Zhang J. , Lin F.
Published: September 2022

Nickel clad hexagonal boron nitride (h-BN) powders were prepared by reducing nickel ions from a solution under hydrogen pressure in the presence of ammonia as a complexing agent, and plasma spraying was carried out to deposit the corresponding coating. The microstructure, morphology and phase composition of the powders and the coating were characterized by optical microscope (OM), Scanning Electronic Microscope (SEM) and X-ray Diffraction (XRD), respectively. The results show that alkali solution pretreatment and activation procession are necessary for acquiring a dense and uniform nickel coating on the surface of the h-BN particles, and the h-BN particles are distributed well throughout the coating with the porosity of about 26%, which indicate that the coating was potential for abradable sealing application.
Particle Trajectories by Arc Spraying with Cored Wires
Authors: Tillmann W. , Vogli E. , Abdulgader M. , Gurris M. , Kuzmin D. , Turek S.
Published: September 2022

To use the manifold possibilities that arc spraying offers to deposit wear resistance layers, the knowledge of the particle formation and their characteristics are necessary. The work is focused on studying the particle trajectories during arc spraying with cored wires. Different cored wires under various spraying parameters are investigated by means of a high speed camera. Particle properties in-flight, such as velocity and temperature are determined. Correlation between particle trajectories and particle characteristics at different spraying conditions are established. At the same time, the particle-laden gas flow is simulated numerically and the computed solutions are used to illustrate the utility of the proposed CFD model and compared with experimental results. The employed mathematical model represents a system of macroscopic conservation laws for the continuous gas phase and for the gas-solid mixture. This formulation makes it possible to circumvent the numerical difficulties associated with the implementation of a (potentially ill-posed) two-fluid model. The discretization in space is performed using a high-resolution finite element scheme based on algebraic flux correction in terms of local characteristic variables. The artificial diffusion operator is constructed on the discrete level and fitted to the local solution behavior using a multidimensional flux limiter of TVD type.
Study on Corrosion Resistance Behaviors of Zn, Al, Zn/Al 85/15 Coatings Produced by Twin Arc Spray Technique on Steel
Authors: Cevher O. , Gulec A. , Turk A. , Ustel F. , Yilmaz F.
Published: September 2022

Twin wire arc sprayed Zn, Al and Zn/Al 85/15 coatings were investigated for comparison of their corrosion resistance, electrochemical behavior. The Zn, Al and Zn/Al 85/15 coatings possess prominent electrochemical passivation behavior. Oxide formation mainly onto the coating surfaces were identified with energy-dispersive X-ray analysis and were believed to be responsible for the passivation phenomena observed in the electrochemical polarization. Zn and Al are more negative in electrochemical potential than iron. Zn coatings act as a sacrificial anode and providing cathodic protection. Aluminum shows passive corrosion protection according to stable oxide layer occurs on coating surface. Zn/Al 85/15 coating show two corrosion protection mechanisms together. In this study, steel samples were coated with Zn, Al and Zn/Al 85/15 in optimum conditions by wire arc spraying technique. These coatings were investigated behaviors of polarization and corrosion resistance with electrochemical test.
The Effect of Process Parameters on the Microstructure and Mechanical of Arc Sprayed Zn, Al, Zn/Al 85/15 Coatings
Authors: Gulec A. , Turk A. , Ustel F. , Yilmaz F.
Published: September 2022

Zn and Zn/Al coatings were manufactured by using twin wire arc spray (TWEA) system under various gas pressure and current. Microstructure, hardness, surface roughness and adhesion strength of the coatings were investigated by using standard characterization methods. Test results show that increasing atomizing gas pressure increased mechanical properties and surface quality. The process current had an important role on microstructural, mechanical properties and surface quality.
Cavitation Resistance and Mass Loss Mechanism in Coatings Deposited by Thermal Spraying
Authors: Pukasiewicz A. , Capra A. , Paredes R.
Published: September 2022

The cavitation erosion result mass loss. Welding is the most common technique used to recover the geometrical profile of the blades. However it is known that tensile residual stress can develop. The search for manufacture process that could reduce or eliminate the residual stress level will contribute for a longer life service. The target in this study to evaluate the potential of ASP thermal spray to recover surfaces. The influence of processing parameters on the cavitation resistance and mechanisms was evaluated for three alloys, AWS309LT1, AWS410NiMo and a Co stainless steel known as Cavitec. Coatings were analyzed by optical and electronic microscopy, microhardness and cavitation tests regarding the effect of air pressure. The results showed that lamellae morphology, oxide volume fraction and cavitation resistance were modified by the ASP parameters. The increase in the pressure modified the oxide fraction from 26 to 37% in AWSI309LT1, 23 to 31% for AWS410NiMo and 16 to 23% for Cavitec. Mass loss varied from 3.5 to 4.8 mg/h for AWSI309LT1, 6.65 to 18.19 mg/h for AWS410NiMo, and 3.4 to 4.0 mg/h for Cavitec; the best performance occurred with Cavitec and was associated with higher pressure of deposition and minor oxide volume fraction.
Substrate and Powder Preheat Effects on the Kinetic Spray of Hard Metal and Composite Coatings on Cast Iron
Authors: Powell N.E. , Patel N. , Elmoursi A.A. , Zhao Z.B. , Gillispie B.A. , Fuller B.K.
Published: September 2022

We investigate the sprayability of various hard metal and composite powder coatings via kinetic spray on cast iron by utilizing both powder and substrate preheat. These coatings include copper, a copper-zirconia composite, nickel, a zinc-nickel composite, and Ti6Al4V alloy. Using the kinetic spray process the coatings were applied to a cast iron substrate which was ground and sand blasted prior to spray. Analysis performed on powders and coating includes: cross-sectional microscopy, hardness of powders and substrate, substrate temperature as a function of heating and cooling times, and adhesion at the coating/substrate level. Results include spray parameters to allow for nickel and copper coatings to be developed on cast iron, adhesion strength as a function of powder hardness, porosity of nickel and Ti6Al4V coatings, and incorporation rates of zirconia in a copper matrix on cast iron. This is an attempt to spray hard powders on a hard substrate. Harder particles are more difficult to spray because they require more energy to plastically deform. Therefore the hardness of the particles plays a significant role in the deposition of a coating. Similarly, harder substrates are more difficult to spray on. This work demonstrates techniques that make spraying hard particles on hard substrates possible.
Formation of NiAl Intermetallic Compound by Cold Spraying of Ball-Milled Ni/Al Alloy Powder Through Post Annealing Treatment
Authors: Zhang Q. , Wang X. , Ren Z. , Yang G. , Li C. , Li C.
Published: September 2022

Ni/Al alloy powders were synthesized by ball milling of nickel-aluminum powder mixture with a Ni/Al atomic ratio of 1:1. Ni/Al alloy coating was deposited by cold spraying using N2 as accelerating gas. NiAl intermetallic compound was evolved in-situ through post-spray annealing treatment of cold-sprayed Ni/Al alloy coating. The effect of annealing temperature on the phase transformation behavior from Ni/Al mechanical alloy to intermetallics was investigated. The microstructure of the mechanically alloying Ni/Al powder and NiAl coatings was characterized by scanning electron microscopy and X-ray diffraction analysis. The results show that a dense Ni/Al alloy coating can successfully be deposited by cold spraying using the mechanically alloyed powder as feedstock. The as-sprayed alloy coating exhibited a laminated microstructure retained from the mechanically alloying powder. The annealing of the subsequent Ni/Al alloy coating at a temperature higher than 850°C leads to the complete transformation from Ni/Al alloy to NiAl intermetallic compound.
Low Pressure Gas Dynamic Spray of Polymer Doped Nanoparticle Contained Feedstocks
Authors: Maeva E. , Leshchinsky E. , Beneteau M. , Villafuerte J. , Maev R.
Published: September 2022

A new approach is explored to achieve the aluminum alloy powder layer from nanoparticle contained metallic powder mixture feedstock by Low Pressure Gas Dynamic Spray (LPGDS) or Cold Spray (LPCS). In this approach, mixtures of micron-sized aluminum powder (average size of 10 µm) and alloying nano-powder of Cu, Si and TiC (200-500 nm), at appropriate proportions to compositions of Al-5wt%Cu, Al-5wt%Cu-0.75wt%Si and Al- 5wt%Cu-5wt%TiC with polymer binder were prepared by stirring. Then, the powder mixture was compacted into pellets, dryed, and further milled to obtain the particle agglomerates (average size of 50 µm) . The powder feedstock were sprayed by LPCS. In this paper, we investigate the spraying behavior Al-based nanoparticle contained powder mixtures the microstructural development and mechanical properties of deposited layers using a microindentation, scanning probe microscopy, scanning electron microscopy and energy dispersive X-ray analysis.
Effect of the Increase in the Entrance Convergent Section Length and Geometry of the Gun Nozzle on Properties of Cold Sprayed Copper and Titanium Coatings
Authors: Sakaki K. , Takahata M. , Takeda K. , Shinkai S. , Hosono T. , Shimizu Y.
Published: September 2022

Nozzle geometry influences gas dynamics, such as gas density, velocity and temperature, making sprayed particle behavior one of the most important parameters in cold spray process. Gas flow at the entrance convergent section of the nozzle takes place at relatively high temperature and are subsonic. Thus, this region is a very suitable environment for heating spray particle. In this study, numerical simulation and experiments were conducted to investigate the effect of nozzle contour (convergent –divergent and convergent-divergent-barrel), entrance geometry of convergent–divergent nozzle and powder injection position at nozzle on the cold spray process. The process changes inside the nozzle were observed through numerical simulation studies and the results were used to find a correlation with coating properties. A copper and titanium powder was used in the experiments. Working gas (is nitrogen) pressure and temperature at nozzle-intake were 3MPa and 623K, respectively. In addition, the change in the nozzle contour and the change in the entrance convergent section length of the gun nozzle were found to have a slight effect on the coating microstructure. Powder injection position was also found to influence deposition efficiency and coating properties. Deposition efficiency of both copper and titanium increase with increasing the length of the convergent section of the nozzle.
Microstructures and Tribological Performances of Cold Sprayed Tin-Bronze Based Composite Coatings
Authors: Guo X. , Zhang G. , Liao H. , Coddet C. , Li W. , Gao Y.
Published: September 2022

In this paper, tin-bronze/TiN and tin-bronze/quasicrystal (AlCuFeB) composite coatings were fabricated by cold spray process. Microstructures and microhardness of coatings were characterized. Ball-on-disc dry sliding wear tests were conducted in an ambient condition to examine the tribological performance of the composite coatings. The results show that the microhardness and densities of composite coatings increase significantly compared to those of the pure tin-bronze coating. The friction coefficients of coatings decrease with the introduction of reinforces. Furthermore, the tin-bronze/quasicrystal composite coating yields a lower friction coefficient and wear rate compared to the bronze/TiN coating. The tribological mechanisms were discussed.
Al-12Si Cold Sprayed Coatings with Controlled Porosity
Authors: Christoulis D.K. , Borit F. , Guipont V. , Jeandin M.
Published: September 2022

The demand of industry for metallic thermal sprayed coatings with controlled porosity until now is fulfilled by the spraying of metallic powders mixed with additives (organic element in many cases) which play the role of pores. The new technology of cold spray can lead to the formation of innovate coatings of controlled porosity by using pure metallic (or alloy) powder without any further addition. A fine Al-12Si powder (<45 µm) was sprayed with a cold spray system (CGT Kinetic 3000-M) on stainless steel substrate under different spraying conditions. In the present study, the new polymeric nozzle PBI-33 of CGT was used for the formation of al-based coatings. The microstructure, the porosity, the Vickers microhardness and the superficial Rockwell hardness (R15Y) of the produced coatings are examined.
Development of a Low Cost System for the Cold Spray Process with Helium
Authors: Verdy C. , Liao H. , Landemarre O. , Coddet C.
Published: September 2022

The use of helium with the cold spray process is well-known to give a higher velocity to the particles and thus denser coatings than those obtained with the classical use of nitrogen. The LERMPS-UTBM laboratory has developed a unique system to use helium without losses. The spray process occurs in a LPPS tank and a specific closed circuit including the cooling and filtering of helium allows its circulation. The spray operations can be made at low helium pressure with no pollution by oxygen. The control device allows to work with different pressures and gas temperatures at the torch with the same tank pressure. Helium gas flow can reach 180 Nm3/h and current cold spray torches could be used. The circulation and reuse of helium in a closed circuit result in a very low consumption of helium. The first coatings of copper alloys are presented in this work.
Flame Sprayed Al-12Si Coatings for the Improvement of the Adhesion of Composite Casting Profiles
Authors: Voyer J. , Peterlechner C. , Noster U.
Published: September 2022

Flame sprayed Al-12Si coatings were produced onto the surface of composite castings parts in order to enhance the adhesion of such castings. Due to the high surface roughness and the presence of pores in the coatings combined with the formation of an intermetallic phase at the interface, the adhesion of flame sprayed composite castings could be enhanced by a factor of 2 in comparison to blank castings and by a factor of 1.3 when compared to sand-blasted castings. However, results also show that gaps are mostly present at the interface between the Al profiles and the flame sprayed coatings and these gaps have a negative effect on the adhesion values of the composite casting parts. Therefore, an optimization of the adhesion of the coating on the Al profiles through an optimization of both the sand-blasting and the flame spraying parameters would be beneficial for further enhancement of the adhesion of composite casting parts.
Thermal Fluxes Transferred by HVOF Jets Produced by Different Guns
Authors: Bolot R. , Landemarre O. , Coddet C.
Published: September 2022

Thermal fluxes transferred during HVOF thermal spray have an important influence on the thermal history of the work-piece. Thus, there is an interest in quantifying these fluxes. Today, different studies based on the use of calorimeters were proposed in the literature and CFD calculations may also be used to confirm the measures. In the present study, a new method based on the measurement of the transient increase of the work-piece temperature was used in order to estimate the thermal exchanges between an HVOF jet impinging on different diameter cylinders. The results indicate that fluxes of several MW/m2 may be transferred depending on the standoff distance, spray parameters and gun.
Influence of Particle Velocity on Splat Formation during Thermal Spraying
Authors: Kharlamov Y.A.
Published: September 2022

Current understanding of mechanisms of splat formation during thermal spraying are discussed. Schematic of influence of particle velocity on change of impact and forward pressure during particle-substrate interaction are given. The existence of three typical zones of particle-substrate contact is shown. These zones are: (1) central circle type mechanically activated by hammer and head pressure; (2) middle ring-shaped mechanically activated by head pressure and friction of spreading particle; (3) peripheral ring-shaped mechanically activated by friction of spreading particle. It is possible to estimate dimensions of these zones analytically. The stress distribution on particle-substrate contact during splat formation is discussed. It is shown that relative values of area for these zones depends from particle velocity. The presence of these typical zones during splat formation shown by conduction of special model experiments.
Investigation of a Novel Plasma Sprayed YSZ Ceramic Coating Deposited by Amorphous YSZ Ceramic Powder Feedstock
Authors: Lin F. , Yang Z.Y. , Li X.F. , Yan S.K. , Liu J.H. , Zhang J.H. , Wang L.M.
Published: September 2022

An amorphous Yttria Stabilized Zirconia (YSZ) ceramic powder feedstock is successfully used to produce a novel YSZ ceramic coating by plasma spraying process, in this paper. Unlike conventional atmosphere plasma spray (APS) and solution precursor plasma spray (SPPS) YSZ coatings, the YSZ ceramic coating fabricated by plasma spraying amorphous YSZ ceramic powder feedstock reveals complex structure of cell and ultrafine particles instead of conventional splats and porous structure. A large number of ultrafine particles are found in the cell. Phase structure of the YSZ ceramic coating is tetragonal. Porosity is about 31%. In addition, thermal cycling test is nearly 370 cycles, and the thermal conductivity is 1.0 W.m-1.K-1, at 1250 temperature. Based on these excellent properties, the YSZ ceramic coating fabricated by plasma spraying amorphous YSZ ceramic powder feedstock should be used as high-temperature abradable sealing coatings and thermal barrier coatings (TBCs).
Experimental Simulation Study of Intersplat Bonding Formation by Deposition of YSZ Splats on Preheated YSZ Substrate
Authors: Li C.-J. , Xing Y.-Z. , Li Y. , Li C.-X. , Yang G.-J.
Published: September 2022

Yttria stabilized zirconia (YSZ) splats were plasma sprayed on the YSZ substrate preheated to different temperature to examine the influence of the temperature of the underlying surface on which molten droplet impacts on deposition characteristics. The splat morphology and the bonding at the splat-substrate interfaces were examined by SEM. It was found that the crack density decreases rapidly with the increase of the temperature when the splat were formed on an YSZ substrate preheated to above 800°C. The nucleation of YSZ melt on the base of YSZ substrate grains takes place during solidification leading to the formation of the bonding between the splat and substrate when the temperature is increased to over 600°C. The substantial bonding was observed at the interface between YSZ splat and YSZ substrate as the temperature is increased to over 800°C. The results revealed that the temperature of the previous splat on which a molten droplet impacts significantly influence the formation of the interface bonding. In addition, the mechanism and condition for the bonding formation of a splat on a substrate with the identical compositions were discussed.
Influence of Plasma Generation Conditions in Gas-Water Torch on Spraying Process
Authors: Kavka T. , Maslani A. , Kopecky V. , Sember V. , Chumak O. , Hrabovsky M.
Published: September 2022

The present paper examines a hybrid DC arc thermal plasma torch with gas-water stabilisation and its application for thermal spraying. The torch was worked out based on the water-stabilised plasma torch WSP, main features of which are high temperature of the generated plasma and high powder through-put. In the hybrid torch the cathode part is modified in the way like in gas torches, which not only provides proper stabilisation of the arc in this region and cathode protection from contact with stabilising water but also allows to vary properties of the generated plasma. Change of the secondary gas flow rate, which is usually argon, results in strong changes of the plasma gas density, while the energy balance of the torch remains almost unchanged. This in turn leads to modification of the plasma jet properties. The paper describes effect of the plasma torch parameters on behaviour of the generated plasma jet and injected powder particles. The results show how particle velocities follow changes of the plasma jet properties according to the plasma torch operation parameters. Both increase of arc current and argon flow rate provided increase of particle velocities.
Fundamental Understanding of the Liquid Precursor Plasma Spray Process Through Modeling and Experiments
Authors: Jordan E.H. , Cetegen B.M. , Gell M. , Chen D. , Basu S. , Teicholz M. , Ma X.
Published: September 2022

Abstract-Solution precursor plasma spray (SPPS) is a relatively new thermal spray process in which chemical precursors are injected into DC-arc plasma spray torch in place of powder. This process is able to make relatively porous (15-25% porosity) thermal barrier coatings with through-thickness cracks that enhance their thermal strain resistance. The SPPS process can also make dense titania and alumina zirconia coatings. The process can make thin and thick coatings, dense and porous coatings, structural and functional preforms, new compositions, and metastable materials. Metastable materials arise because the solution is molecularly mixed and the cooling rate in thermal spray is high. The process has the disadvantage of needing to provide energy to evaporate the solvent and of being a new process where less extensive empirical knowledge and modeling insights exist, compared to air plasma spray with powders. The microstructure process parameter relation is explored. Results from modeling studies concerning evaporation of droplets and related solute concentration gradients, modeling studies of aerodynamic break-up and experimental studies of non-aero-based droplet break-up and of the effects of solution concentration will be described. These studies will be related to experimental results for making dense coatings.
Effects of Heat Treatment on Properties of Plasma Spray NiAl Coatings
Authors: Moshref Javadi M. , Edris H. , Salehi M.
Published: September 2022

For production of intermetallic coatings, various types of Ni-Al powders were plasma sprayed at different spray distance and the effect of heat treatment on phases, microstructures and microhardness of coatings was examined. XRD, SEM, EDAX and microhardness were used for characterization of the coatings. Heat treatment of the coatings in various temperatures caused changes in hardness of the coating, increased percentage of intermetallic compounds, completed intermetallic production reactions, but did not change porosity percent. Increasing heat treatment temperature caused oxidation and decreased improvement of coating properties.
Mathematical Model of Surface Plasma Hardening Process of Steel Parts
Authors: Markovnik D. , Kundas S. , Ivanov D.
Published: September 2022

The plasma surface hardening, as one of methods of surface treatment by heating sources with high power density, finds presently wide and effective application in conditions of short-series and single-part (including repair), and large-scale and wholesale manufacture. One of effective methods for research and optimization of the plasma surface hardening is the use of computer simulation. The complex mathematical model of steel parts hardening at high-speed plasma heating is presented in the article. Model includes mathematical description of steel parts heating and cooling, and also forming of their stress-strain state. The distinctive feature of the presented model is taking into account under modeling of phase transformations and plastic deformations. It allows to achieve the maximally adaptation of the simulation results to real physical characteristics of the process. The algorithm of model computer realization, based on the application of final elements method is offered.
An Effect of Low Pressure Gas Dynamic Spray on Micro-Corrosion Behavior of Al Alloys
Authors: Leshchynsky V. , Maeva E. , Lubrick M. , Villafuerte J. , Maev R.
Published: September 2022

The corrosion behavior of Al alloys, produced by cast and powder (Low Pressure Gas Dynamic Spray or Cold Spray) technologies, was examined in 3% sodium chloride solution from the viewpoint of localized corrosion. The susceptibility to localized corrosion is known to be strongly affected by intermetallic phases present in the alloy’s microstructure. The influence of individual cathodic and anodic intermetallic phases was investigated by using a microelectrochemical setup and by electrochemical methods. The optical and scanning electron microscopy data reveal that the cast and powdered alloys experience localized corrosion due to presence of the intermetallic phases which results in the micro-corrosion effects such as exfoliation corrosion, intergranular or crevice corrosion, and most severely pitting. Cast material has lower corrosion properties because of the higher heterogeneity of the structure as compared with powder sprayed composite.
Effect of Zinc and Aluminium Thermal Spray Coatings on Hydrogen Embrittlement in Marine Industry
Authors: Moshref Javadi M.
Published: September 2022

Hydrogen embrittlement in high strength marine structural steels can occur by improper cathodic protection. In this article the possibility of Hydrogen embrittlement (HE) in high strength steels caused by zinc and aluminium thermal sprayed (TS) coatings has been considered. Provided potential from the TS coatings in marine environments and permissible potential for performing cathodic protection and inhibiting HE has been described. Also effective parameters on HE and prevention methods for HE by thermal sprayed coatings has been reviewed. An effective method for quality stabilizing and potential regulating in anticorrosion TS coatings is utilization of the alloyed materials. Most used material for anticorrosion TS coatings is aluminium that provides relatively moderate potential and low current density and in particular situation can cause HE.
Tribological Behaviour of Thermally Sprayed Coatings at Elevated Temperatures
Authors: Houdková Š. , Zahálka F. , Kašparová M. , Berger L.-M.
Published: September 2022

Hardmetal coatings prepared by high-velocity oxy-fuel (HVOF) spraying represent an advanced solution for surface protection against wear. The work presented in this paper focussed on the comparison of the tribological behaviour of WC-Co, Cr3C2-NiCr and (Ti,Mo)(C,N)-NiCo hardmetal coatings under dry sliding wear conditions at room and elevated temperatures (at 500°C and 700°C). The friction properties of these HVOF-sprayed coatings were studied in detail. The progression of the coefficient of friction (CoF) was measured during the pin-on-disc tests at the different temperatures. The mechanisms of wear and the heat-related changes in surface roughness and microhardness of the coatings were studied.
Comparing Study of High Temperature Erosion of HVOF Sprayed Cr3C2-NiCr Coating and Mild Steel for Boiler Tube
Authors: Yang G. , Zhang S. , Wang Y. , Li C. , Li C.
Published: September 2022

The significant erosion of the boiler tube at high temperature becomes an important problem for the safe operation of circulating fluidized bed boiler. This paper investigated the erosion behavior of the HVOF sprayed Cr3C2-NiCr coating at high temperature comparing with the typical mild steel for boiler tube. Results showed that the erosion rate of the mild steel increased with the increase of temperature. The erosion rate of the mild steel at 800°C was 4 times that at 300°C at an erosion angle of 30°. However, the erosion rate of the HVOF sprayed Cr3C2-NiCr coating was not influenced by the temperature in the range of 300 to 800°C. It is found that the erosion resistance of HVOF sprayed Cr3C2-NiCr coating was more than 3 time higher than that of the mild steel at 700 to 800°C. In addition to the ploughing on the surface of the worn coating, the cracking along splats interfaces in the coating was clearly observed on the cross-sectional microstructure of the coating. The results indicate that the erosion performance of the HVOF sprayed Cr3C2-NiCr coating is controlled by the cohesion between splats in the coating and can be further enhanced by improving splat cohesion.
Comparisons of Microstructure and Properties of Three Cobalt-Based Cermets Deposited by High Velocity Oxy-Fuel Spraying using Clad Powders
Authors: Wang Y.-Y. , Li C.-J. , Yang G.-J. , Li C.-X.
Published: September 2022

Three types of cobalt-based cermet coatings were prepared by high velocity oxy-fuel (HVOF) spraying using cobalt- clad TiC-50Co, SiC-50 Co and WC-18Co powders. The microstructure of three coatings was characterized using a scanning electron microscope (SEM). The adhesive strength of the coatings was tested according ASTM C633-79 standard. The hardness of three coatings was measured using a HV-5 Vickers hardness tester. The abrasive wear performance of the coatings was examined by a dry-sand rubber wheel tester according to ASTM G65-61 standard. The results show that the density, thermo physical properties and volume fractions of the solid carbide phases in the spray particle have a significant influence on the adhesive strength of the coatings. The hardness of WC-18Co coating is higher than that of TiC-50Co and SiC-50 coatings and is much lower than WC-17Co coating deposited with sintered-crushed powders. Moreover, the abrasive wear volume loss of the WC-18Co coating is about 60 times higher than that of the WC-12Co coating sprayed by sintered-crushed powder, and greatly lower than that of TiC-50Co and SiC-50 coatings. The wear mechanisms of three coatings are discussed.
Improvement of the Corrosion Resistance of Magnesium Alloys by Means of Coating and Remelting
Authors: Wielage B. , Lampke Th. , Pokhmurska H.
Published: September 2022

The implementation of magnesium alloys for automotive, aeronautic and other applications is of the great importance due to their especial properties. Magnesium offers greater weight saving capacity than aluminium, as its density, 1.7 g/cm-3, is two thirds the density of aluminium, 2.7 g/cm-3, without significant loss of strength and magnesium alloys show high specific strength. On the other hand surface properties of magnesium alloys like wear and corrosion resistance are rather poor. A large amount of methods are intensively elaborated to overcome this problem from developing of new alloys, different surface treatment methods and a great variety of coating systems. In present work the results concerning improvement of corrosion and wear resistance of magnesium alloys by means of zinc based coatings are presented. Coatings are deposited on magnesium substrates (AM20, AZ31, AZ91) by arc spraying with Zn, ZnAl4 and ZnAl15 solid wires as well as by electroplating of zinc. Nevertheless the onset of bimetallic corrosion between Zn and Mg significantly increases corrosion current density. In order to provide longer protection, two main technological solutions are taken into consideration. First relies upon a modification of the main electroplating technology, second is based on the selection of an effective post treatment. For the first approach a consecutive process is elaborated based on the two-step electrodeposition. The first is from alkaline bath followed by the second step in acidic chloride bath. A dense and compact complex layer is obtained. The second approach is based on the post treatment of deposited coatings and provides a formation of thick and uniform reaction layer in magnesium on the interface between zinc or zinc based coating and substrate. These layers have fine eutectic structure with microhardness 3-4 times higher than that of the base material. Heat treatment is carried out with focused irradiation of tungsten halogen lamp line heater in atmosphere. Microstructure of deposited coatings as well as that of modified surface layers is investigated by metallographic methods. Corrosion properties are estimated by electrochemical measurements. Abrasion wear resistance of the modified layers is determined by scratch test and oscillating wear tests. It is shown that the both applied methods improve corrosion properties of magnesium alloys. Electrolytic zinc coatings deposited by electroplating in the elaborated two- step process demonstrate good barrier properties. Durability increases about three times in comparison with a single coat obtained from alkaline bath. Infra red heat treatment of thermal spray coatings results in formation of modified layers in magnesium substrates that prevent the galvanic corrosion of investigated systems. Wear resistance of reaction layers is up to 4 times higher to compare with the base material.
Diffusion Barrier Coatings for CFC Components by Plasma Spraying – Some Research Results of the Project "IGF 14.880 N"
Authors: Bobzin K. , Zhao L. , Ernst F. , Richardt K.
Published: September 2022

Carbon fibre reinforced carbon (CFC) composites have been more and more used in different industrial areas as high temperature materials. Some application examples are CFC components in modern furnaces for heat-treatment and brazing. Because CFC components can react with metallic materials when they contact each other, diffusion barrier coatings are essentially important for such CFC components. The aim of the project IGF 14.880 N “Thermally sprayed diffusion barrier coatings for CFC components in high temperature applications” is to develop diffusion barrier coatings by thermal spraying technology. In the project, different coating systems have been developed and investigated regarding the coating build-up, coating microstructure, bonding, thermal shock resistance and diffusion barrier function. The research results reveal that some developed coating systems are suitable for applications in furnaces. In the present paper, some research results of this project are reported.