bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical Investigation of the Melting Degree of Ceramic Powder Particles During Air Plasma Spraying
Authors: Bobzin K. , Öte M. , Knoch M. A. , Alkhasli I. 
Published: November 2022

Abstract
Air plasma spraying is a variation of thermal spraying that is used, among others, for the production of thermal barrier and wear resistant coatings. High plasma temperatures enable the processing of ceramic powder particles which have a high melting point and cannot be processed otherwise. Due to their low heat conductance, the ceramic particles are not necessarily fully melted during their flight in the free jet and prior to the impact on the substrate surface. Experimental particle temperature measurements by means of particle diagnostics systems deliver merely the surface temperature of the particles while the melting degree of the ceramic particles remains unknown. Therefore, the temperature field within spherical Al2O3 particles is numerically investigated for a commonly used particle size distribution by considering different particle sizes. The model includes a two-way coupled particle-laden free jet model and takes the latent heat of melting and evaporation into account. The effect of the particles size as well as the stand-off distance on the melting degrees of the particles in the given powder size distribution is determined.
Mechanical Properties of Yttria-Stabilised-Zirconia for Thermal Barrier Coating Systems: Effects of Testing Procedure and Thermal Aging
Authors: Planques P. , Vidal V. , Lours P. , Proton V. , Crabos F. , Huez J. , Viguier B. 
Published: November 2022

Abstract
Cyclic oxidation failure of Atmospheric Plasma Sprayed Thermal Barrier Coatings systems (APS TBCs), commonly used to insulate hot sections in gas turbines, usually results from the spallation of the ceramic top coat. Consequently, in order to predict such spalling phenomena, understanding the mechanisms for cracks initiation and propagation in thermal barrier coatings is of utmost concern for engine-makers. Failure of the TBC is strongly related to the thermal and mechanical properties of each component of the multi-materials system (substrate, bond coat and ceramic) but also to the response of the TBC as a whole. The purpose of the work is to assess the mechanical behaviour of thick TBC using experimental approach for TBC standard lamellar, porous and microcracked microstructure (classically obtained through APS coatings). The experimental characterisation of the mechanical behaviour of the ceramic top coat of the TBC is addressed on specifically designed and prepared free-standing specimens using three points bending (3PB) tests and Small Punch Testing (SPT). The tests are performed on free-standing top coats made of YSZ in the as deposited states and for specimens that undergone isothermal aging at 1100°C for various durations (1h, 10h and 100h). The results of test performed at room temperature using both mechanical testing techniques are compared. This allows to show the evolution of mechanical properties after thermal aging. Tests performed at 850°C in the SPT ring show that the evolution of properties resulting from this aging may be different at room temperature as compare to 850°C.
Porosity Measurements on Heat Treated Suspension Plasma Sprayed YSZ Coatings Using NMR Cryoporometry
Authors: Ekberg J. , Klement U. , Creci S. , Nordstierna L. 
Published: November 2022

Abstract
Suspension plasma sprayed (SPS) coatings can be produced with fine powder particles and tailor-made porosity. This allows to achieve low thermal conductivity which makes the coatings attractive as e.g. topcoats in thermal barrier coatings (TBCs). Used in gas turbine applications, the TBCs are exposed to high temperatures which leads to alterations of the microstructure. To obtain coatings with optimized properties, possible microstructure alterations like closing of pores and opening of cracks have to be taken into account. Hence, in this study, TBC topcoats consisting of 8 wt.% yttria-stabilized zirconia (YSZ) were heat treated in air at 1150°C and thereafter investigated using scanning electron microscopy, X-ray diffraction, and nuclear magnetic resonance (NMR) cryoporometry. For all investigated samples, the porosity decreased as a result of the heat treatment. The finer pores and cracks disappeared and the larger pores grew slightly and achieved a more distinct shape as the material seemed to become more compact.
Microscale Adhesion Strength Evaluation of Cold Sprayed Copper Deposit
Authors: Ichikawa Y. , Tokoro R. , Ogawa K. 
Published: November 2022

Abstract
Adhesion strength is one of the most important characteristics when discussing the reliability of a cold spray. A focused ion beam (FIB) was used to conduct ultra-micro tensile tests for micro-scale adhesive strength evaluations of high-pressure type cold-sprayed copper deposition on an aluminum substrate. It was also used to determine the essential factor of adhesion strength and the coating formation mechanism. The micro-scale local adhesion strength of cold-sprayed copper deposits on an aluminum substrate was successfully evaluated by FIB microtensile tests. The average local adhesion strength of this deposit was 223 MPa. The variations in adhesion strength between deposit and substrate were smaller than the interfacial strength of cold-sprayed deposits. This was caused by the repeated collision of these subsequent particles.
Development of HVAF-Sprayed Novel Fe-Based Coatings for Large Area Applications
Authors: Bobzin K. , Öte M. , Knoch M.A. , Sommer J. 
Published: November 2022

Abstract
One important trend in thermal spraying is the application of novel Fe-based corrosion/wear protection coating systems. A typical field of application for such corrosion and abrasive wear protection coatings are rotary dryers of paper machines. At the moment, these cylinders are coated by wire arc spraying. A disadvantage of the wire arc sprayed coatings is their high thickness, which has a heat-insulation effect, and their high roughness. Therefore, an expensive post production grinding process is necessary in order to achieve the required surface quality. The goal is to develop a HVAF process that enables the production of thin, dense and near net shape corrosion/wear protection coating systems, which significantly reduce the post-production time and costs. In this study, the HVAF coating process and a novel Fe-based feedstock material are investigated. In the first step the Fe-based powder is analysed thermally using differential scanning calorimetry, to investigate the solidification and melting temperature of the feedstock material. Furthermore, the influence of the spraying distance and the powder feed rate on the microstructure and porosity of the resulting coatings is investigated using light microscopy. Furthermore, the deposition efficiency of HVAF coatings is analysed regarding their economic efficiency.
Development of HVAF ID Coating Technology and Materials
Authors: Verstak A. , Gries B. , Breitsameter M. 
Published: November 2022

Abstract
The HVAF process provides a slightly different (to HVOF and other thermal spray processes) and unique combination of thermal and kinetic energy, which presents a technical challenge to material manufacturers who have over the past years optimized their material offerings to the demands and characteristics of plasma, combustion and more recently the various HVOF processes. The recent development of HVAF ID torches, capable of applying the highest quality coatings into dimensions of less than 100mm (4”), has provided a further need to optimize spray materials for the best possible interaction between the spray device and the feedstock in order to meet developing coating specifications from various industries. This paper will discuss the methodologies utilized from the points of view of torch design, material manufacture, spray parameter and procedure optimization, as a means of producing the highest performing coatings to meet specific industry aspirations.
Practical Experiences Using HVOF Sprayed Tungsten Carbide Coatings in the Plastic Foil Industry
Authors: Brandt O. , Möhwald K. , Reimche W. , Bruchwald O. 
Published: November 2022

Abstract
For most HVOF sprayed tungsten carbide coatings powders with identical particle-size distributions and compositions are interchangeable, within the meaning that as long as the manufacturing process is identical other properties are nearly irrelevant. In plastic foil industry often complex strains occur on the surfaces of the used tools. These strains comprises from a chemical attack by means of released process gases due to the thermal conditions and from an abrasive component caused by additives of the plastic. Shaping calender rolls with a high gloss mirror finished surface may show only a minimal wear in such complex strains because otherwise the quality of the foil is affected in a negative way. In this range of applications the practical experience shows that with commercial characterization values such as microhardness and porosity HVOF sprayed tungsten carbide coatings are not sufficiently described. The article describes the effects of different microstructures on the application behaviour of a coating. For that purpose analytical methods such as quantitative phase analysis due to X-ray diffraction by means of Topas-Rietveld-Method were used. Preliminary results of the use of a novel high frequency eddy current test method suggest the potential to allow a local correlation of specific properties of the coatings with their microstructure.
Tribological Behaviour of Flame-Sprayed HDPE/Cu Composite Coatings
Authors: Xu Y. , Liu Y. , Jia Z. , Suo X. , Li H. 
Published: November 2022

Abstract
Electroless plating was employed for making copper (Cu)-high density polyethylene (HDPE) core-shell particles for following coating deposition by flame spraying. Our previous works already reported large-scale fabrication of HDPE/Cu composite coatings against corrosion, biofouling and ageing for marine applications. In this work, we further investigated tribological behaviours of the HDPE and the HDPE/Cu composite coatings. The structure of the composite coatings was designed via controlling the thickness of the copper shell coated on the composite powder. The result shows that the addition of copper slightly decreased the anti-wear property of the composite coating. The tribology mechanisms of the composite coating and the HDPE coating were discussed.
Iron-Based Hardfacing Alloys for Abrasive and Impact Wear
Authors: Maroli B. , Dizdar S. , Bengtsson S. 
Published: November 2022

Abstract
Iron-based hardfacing alloys are widely used to counteract abrasive and impact wear of industrial components soil in, sand and mineral processing applications. These alloys show a high performance to cost ratio as well as a low environmental impact. The wear resistance of the components hardfaced with these alloys depends on achieved coating microstructure i.e. on the alloys chemical composition, the coating method and process parameters selected. The present work focuses on iron based hardfacing alloys with varying amount of chromium, vanadium, tungsten, molybdenum, boron and carbon deposited by plasma transferred arc (PTA) overlay welding. Weldability, hardness, abrasive and impact wear of the overlays are presented and interpreted through their microstructure. The performance of the iron based overlays is compared with that of nickel-based metal matrix composite coatings with tungsten carbide (MMC) commonly used for hardfacing of parts subjected to severe abrasive wear. The hardness of the iron based overlays investigated ranges between 60 and 65 HRC while abrasive wear is typically below 20 mm3 (ASTM G65, procedure A). Microstructure consists of different primary precipitated carbides or borides, a martensitic matrix and eutectic structures.
Advanced Processes and System Technology for High-Performance Laser Cladding
Authors: Nowotny S. , Hillig H. , Kubisch F. , Toma F. , Leyens C. 
Published: November 2022

Abstract
Laser cladding technology is widely used in industry to precisely apply tailored surface coatings, as well as three-dimensional deposits for repair and additive layer-by-layer fabrication of metallic parts. However, the processing of larger components, like tools for oil and gas production, is economically challenging due to the conventionally low deposition rates. Consequently, industry is requesting more powerful technologies that maintain the quality advantages of the laser technology, but also make the process more productive and time effective. The modern highest power diode lasers offer practical solutions for applying of large-area laser cladding with significantly increased productivity. Using a fiber-coupled diode laser of 20 kW power and the accordingly developed laser cladding heads, real deposition rates of metal alloys, e.g. Inconel 625, could reach 14 kg/h. With the new-developed powder nozzles with rectangular profile of the powder jet allows at a laser power of 20 kW single tracks with 45 mm-width can be produced. Besides the laser source, the processing laser head is the key parameter for a high productivity and efficiency of the whole cladding procedure. The paper presents a new generation of high-performance laser cladding heads with integrated process sensors, which guarantee a stable long-time operation at highest power levels. The deposition rates achieved with this technology are equal or even exceed typical values of the common PTA technique. Current applications are large-area coatings on power plant components, hydraulic cylinders for off-shore equipment, and large metal forming tools for automotive bodies.
Alloyed Carbides Beyond WC as a New Material Platform for Solving Challenges in Hardfacing
Authors: Fiala P. , Hepp R. , Zikin A. 
Published: November 2022

Abstract
Tungsten carbide in nickel based self-fluxing alloy overlays has been dominating hardfacing applications due to its excellent properties, namely extremely high wear resistance. Nevertheless, there are still applications and limits which tungsten carbide has not conquered. This study focuses on (TiW)C1-x which was deposited with several matrix materials and tested in wear, corrosion and impact resistance and benchmarked against tungsten carbide. Results for several other carbides such as (NbW)C1-x, (VW)C1-x, NbC1-x and TiC1-x overlays deposited by plasma transferred arc (PTA) and laser cladding (LC) will be presented and discussed. As a result of deposition trials and overlay testing, it was found that better thermodynamic stability of alloyed carbides allows them to be used in an iron based matrix and/or a matrix with a high chromium content, in applications requiring improved corrosion and oxidation resistance, better impact resistance and lower weight.
Understanding the Infiltration Behaviour of Sealers Into Thermally Sprayed Coatings
Authors: Bobzin K. , Öte M. , Knoch M. A. , Kunde C. , Dettloff P. 
Published: November 2022

Abstract
Sealants are widely used in order to enhance the performance of porous thermally sprayed coatings, e.g. for electrical insulation or corrosion protection. In order to accomplish required properties, a good infiltration is necessary. The methods to assess the success of a sealing often rely on determining the infiltration depth by SEM or adding colour pigments to the sealer. In this study, a new approach for assessing the success of a sealing operation is investigated. The underlying assumption is that porous coatings are not gas-tight and by sealing them, the measurable gas flow can be reduced. Therefore, the success of a sealing operation may be assessed by comparing gas flows at defined conditions prior and subsequent to sealing. This hypothesis is investigated by coating special highly porous substrates with a wide range of coating porosities and thicknesses, sealing these coatings, comparing nitrogen flows at a defined pressure prior and subsequent to the sealing operation and correlating the measured changes of nitrogen flow with traditionally assessed infiltration depth and filling degree.
Isothermal Oxidation Behavior of HVAF-Sprayed NiCoCrAlY Coatings: Effect of Surface Treatment
Authors: Zhang P. , Sadeghimeresht E. , Peng R. , Li X. , Markocsan N. , Joshi S. , Johansson S. 
Published: November 2022

Abstract
NiCoCrAlY coatings are widely used as bond coats for ceramic thermal barrier coatings (TBCs) and oxidation and corrosion protective overlay coatings in industrial gas turbines. High temperature oxidation behaviour of NiCoCrAlYs has a great influence on the coating performance and lifetime of TBCs. A promising route to decrease the oxidation rate of such coatings is post-coating surface modification which can facilitate formation of a uniform alumina scale with a considerably slower growth rate compared to the as-sprayed coatings. In this work, the effect of surface treatment by means of shot peening and laser surface melting (LSM) on the oxidation resistance of high velocity air-fuel (HVAF) sprayed NiCoCrAlY coatings was studied. Isothermal oxidation was carried out at 1000 °C for 1000h. Results showed that the rough surface of as-sprayed HVAF sprayed coatings was significantly changed after shot peening and LSM treatment, with a compact and smooth appearance. After the exposure, the oxide scales formed on surface-treated NiCoCrAlY coatings showed different morphology and growth rate compared to those formed on as-sprayed coating surface. The oxidation behaviour of surface treated HVAF-sprayed NiCoCrAlY coatings were revealed and discussed.
Heat Treatment of the Thermally Sprayed Coating System NiCrSi/NiCoCrAlY/Al for Repair Brazing High Pressure Turbine Blades
Authors: Nicolaus M. , Möhwald K. , Maier H. J. 
Published: November 2022

Abstract
Depending on the size and type defects of nickel-based alloy turbine blades two procedures are used mainly: cladding and high temperature brazing. The repair brazing of turbine blades is used to regenerate cracks and surface defects and is the focus of this work. In this contribution a two stage hybrid repair brazing process is presented which allows reducing the current process chain for repair brazing turbine blades. In the first stage of this process the filler metal (NiCrSi) then the hot gas corrosion protective coating (NiCoCrAlY) and finally the aluminium are applied in this order by atmospheric plasma spraying. In the second stage of this hybrid technology the applied coating system undergoes a heat treatment in which brazing and aluminising are combined. The temperature-time regime has an influence on the microstructure of the coating which is investigated in this work.
Influence of the Stand-Off Distance and Spray Angle on the Coating Formation and Properties During Three-Cathode Plasma Spraying
Authors: Bobzin K. , Zhao L. , Öte M. , Königstein T. , Oechsner M. , Siebers M. , Andersohn G. , Ellermeier J. 
Published: November 2022

Abstract
Three-cathode plasma spraying is characterized by high process robustness in terms of particle in-flight properties due to high stability of plasma jet. However, during coating parts with complex geometries, process parameters such as stand-off distance and spray angle usually cannot be kept at optimized conditions. In this study, the process robustness during three-cathode plasma spraying of a novel FeCrMnBC alloy was investigated by varying stand-off distance and spray angle to simulate spray conditions for complex geometries. A three-cathode plasma generator TriplexProTM-210 was used to spray FeCrMnBC powder with a fraction of -45 +20 µm onto substrates of cast iron EN-GJL-250. The stand-off distance and the spray angle were varied from d=90 mm to d=110 mm and between ø=90° and ø=60°, respectively, while the other process parameters were kept constant. The results revealed that the reduction of spray angle caused an about 15 % decrease of coating thickness, about 40 % porosity increase and about 15% increase of bond strength. In contrast, the variation of stand-off distance changed only insignificantly the coating thickness, porosity and bond strength. The variation of stand-off distance and spray angle did not result in significant changes in the coating microhardness. The reduction of spray angle resulted in significant worsening of the corrosion protection ability of the coating system.
Effect of Nozzle-Length, Powder Feed-Rate and Spray Distance on HIPOJET 2700 HVOF Sprayed Cr3C2-NiCr Coatings
Authors: Matthews S. , Woo J. , Daniel J. 
Published: November 2022

Abstract
The high wear resistance of Cr3C2-NiCr coatings is reliant on the formation of a dense coating containing a high percentage of carbide grains, with minimal carbide degradation. Such coating characteristics are typically achieved through the use of high velocity oxygen fuel (HVOF) spraying. The propane fuelled, manually operated HIPOJET 2700 HVOF system is one of a suite of smaller sized commercial HVOF systems recommended for smaller job shops. However, few works have characterised the properties of carbide composite coatings produced with this system. In this work a full factorial design of experiment analysis was used to assess the effect of key operating parameters on the quality of Cr3C2-NiCr coatings. The combustion parameters (fuel and oxygen flows) were fixed at the manufacturers recommended settings in order to focus on the effect of nozzle length, powder feed rate and, spray distance. The effect of these variables on the porosity/oxide content, carbide content, microhardness, coating thickness, and relative deposit efficiency is discussed.
An Experimental Approach to Gain Insight Into Cold Gas Spraying of Ceramics
Authors: Gutzmann H. , Irkhin I. , Gärtner F. , Klassen T. 
Published: November 2022

Abstract
In this study, an experimental approach to investigate basic dependencies on impact and bonding of agglomerated ceramic particles in cold spraying is presented. Single impact morphologies of ceramic particles obtained from wipe tests are correlated with data obtained from powder compression experiments with a modified nanoindenter. Different feedstock powders of agglomerated TiO2-nanoparticles were used and also partially heat treated. The powder shapes and sizes prior and after the compression tests were analyzed by confocal microscopy. The single particle impacts were characterized by SEM. Besides the expected influence of substrate material, substrate temperature, and spray conditions, the deformation and bonding of ceramic particles to metal substrates critically depend on the powder properties. To which degree particles fracture or contribute to layer formation upon the high-energy impact is highly correlated to their individual deformation behaviour in quasi-static compression tests.
Spray Pattern and Microstructure of Copper Coatings with the Optimized Rectangular Cross-Section Nozzle by the Computational Fluid Dynamics (CFD) in High-Pressure Cold Spraying
Authors: Sakaki K. , Arai S. 
Published: November 2022

Abstract
In the cold spray process, cross-sectional shape of the nozzle has a significant effect on spray pattern of coatings. There is a rectangular and a circular cross-sectional shapes on the cold spray nozzle. It has been reported that the rectangular nozzle provide a more uniform particle velocity across the exit of the nozzle. The circular exit nozzle is parabolic in shape. So spray pattern with the rectangular nozzle is wider than that with the circular spray nozzle. The goal of this investigation is to establish a design for the cold spray gun nozzle in order to gain more uniform spray profile of coatings. We have investigated the influence of expansion ratio, nozzle total length and the ratio of nozzle length of divergent section and parallel section of rectangular nozzle on behaviours of gas and particle by the computational fluid dynamics (CFD) in high pressure cold spraying. In this study, the spray pattern and microstructure of copper coatings with the rectangular cross-section nozzle optimized by CFD analysis in high-pressure cold spraying are reported. The optimized rectangular nozzle provide a more uniform spray profile of coatings. Relatively finer powder tended to deposit on the end of the coating.