bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Comparative CFD Study of the Influence of Combustion Chamber Geometry in the HVSFS Process
Authors: Plachetta M. , Eckert P. , Kroner M. , Killinger A. , Krieg P. , Gadow R. 
Published: November 2022

Abstract
Suspensions have shown a great potential for being employed as the spraying materials in flame spraying processes with the aim of producing thin and dense coatings. The internal axial injection of a suspension within processes like the high-velocity suspension flame spraying (HVSFS) offers the advantage of complete suspension entrainment within the gas stream, which therefore results in enhanced momentum and heat transfer to the particles. Experimental assessment of the achieved particle velocities and temperatures within the combustion chamber is nonetheless practically infeasible. A better insight into the process is attainable through employing computational simulations. Following a computational fluid dynamic (CFD) modelling approach for HVOF processes, combustion and gas flow turbulences were simulated for different combustion chamber geometries and ethene/oxygen ratios commonly used in the HVSFS process. Simulations were done with the commercial software ANSYS CFX 16.2. To account for the highly turbulent flow characteristics, the k-ε model and the Shear Stress Transport (SST) turbulence model were chosen, employing an eddy-dissipation-model for fuel gas combustion. Second-order upwind discretization was used to enable a good resolution of flow features like shock diamonds. The results of the simulation using different levels of detail of the combustion reaction were compared to experiments employing the modelled combustion chambers and gas flows. Chamber pressure and positions of the shock diamonds were monitored in order to allow a qualitative evaluation of the calculated values.
Effect of Nozzle Geometry on the Microstructure and Properties of HVAF Sprayed Hard Metal Coatings
Authors: Matikainen V. , Koivuluoto H. , Vuoristo P. , Schubert J. , Houdková Š. 
Published: November 2022

Abstract
Thermally sprayed hard metal coatings are the industrial standard solution for numerous demanding applications. Often the performance of thermally sprayed coatings is improved by using finer particle sizes due to improved surface finish and decreased defect sizes. In the aim of utilizing finer particle and primary carbide sizes in thermal spraying of hard metal coatings, several approaches have been studied to control the spray temperature. The most viable solution is to use the modern high velocity air-fuel (HVAF) spray process, which has already proven to produce high quality coatings with dense structures. In HVAF spray process, the particle heating and acceleration can be efficiently controlled by changing the nozzle geometry. In this study, fine WC-10Co4Cr powder (-25+5 µm) was sprayed with three nozzle geometries to investigate their effect on the particle temperature, velocity and coating microstructure. The study demonstrates that the particle melting and resulting W2C formation can be efficiently controlled by changing the nozzle geometry from cylindrical to convergent-divergent. Moreover, the average particle velocity was increased from 780 to over 900 m/s. This increase in particle velocity significantly improved the coating structure and density while deposition efficiency decreased slightly. Further evaluation was carried out to resolve the effect of particle in-flight parameters on coating structure and cavitation erosion resistance, which was significantly improved with the increasing average particle velocity.
High Speed Steel Deposited by Pulsed PTA – Frequency Influence
Authors: Rohan P. , Boxanová M. , Zhang L. , Kramar T. , Lukac F. 
Published: November 2022

Abstract
The powder of HSS (HSS23, AISI M3:2) was deposited by pulsed-PTA method on to low alloyed steel substrate. The influence of pulsation frequency was evaluated on the surface of deposits and on their cross sections by both light microscope and by Vickers hardness measurement apparatus and extreme properties mapping (XPS). Surfacing parameters at current frequency from 0 to 200Hz were tested during deposition of single weld bead. Dilution and heat affected zone were evaluated and compared for all tested parameters. The presence of retained austenite after deposition was determined by X-ray diffraction. The beads deposited with different frequencies differ in their shape, dilution degree, microhardness and penetration depth. It was found that the microhardness increases with current frequency.
Aptitude of Different Types of Carbides for Production of Durable Rough Surfaces by Laser Dispersing
Authors: Wank A. , Schmengler C. , Müller-Roden K. , Beck F. , Schläfer T. 
Published: November 2022

Abstract
Different types of tungsten carbide materials (fused tungsten carbide, nickel clad fused tungsten carbide, macrocrystalline WC and sintered and crushed WC/Co) are used for laser dispersing of construction steel surfaces. Surface roughness analyses and metallographic evaluation of cross sections concerning efficiency of carbide embedding as well as crack formation tendency are carried out. Generally, all types of tested carbides permit production of rough surfaces with metallurgical bonding to the metallic matrix, but only use of nickel clad fused tungsten carbide permits to prevent crack formation. The effectiveness of silicon and silicon carbide for production of durable rough surfaces on aluminium alloys is investigated. Both silicon and silicon carbide qualify for production of rough surfaces by laser dispersing. While silicon carbide particles show higher hardness, use of silicon does not include danger of embrittlement due to formation of aluminium carbide.
Ultrafine Powders for Low-Power HVOF and HV-APS Spraying
Authors: Matthäus G. , Verlotzki V. 
Published: November 2022

Abstract
The currently available powders are for conventional high power HVOF or APS. There is an increasing need for low-power HVOF and HV-APS torches for coating temperature-critical parts and inner diameters. Using them for the new applications causes massive restrictions such as poor coating efficiency, much overspray, rough surface or defects in the layer structure. However, just using ultrafine powders does not solve the problem. The disadvantages in terms of fluidity and oxidation resistance need to be solved, too. Beside the development of modern HVOF, ID-HVOF and Three-cathode-APS coating systems Thermico pursues a continuous enhancement of customized powders. Due to this steady development, Thermico has realized spraying inner diameters with just 10 – 20 mm stand off by using a new WC carbide powder which is able to absorb enough energy out of the low power flame to build up a very dense high quality coating. The modified WC Co 83 17 powder is available for ID HVOF. The high quality coating of outer diameters with a HV-APS is another solution which Thermico has successfully developed. Beside this Thermico had the goal to establish a high quality HV-APS coating to prices competitive to HVOF.
Impact of the Stand-Off Distance and Spray Angle on the Corrosion, Cavitation and Erosion Behaviour of the Thermal Spray Layers Deposited by the Three-Cathode Spraying
Authors: Oechsner M. , Siebers M. , Andersohn G. , Ellermeier J. , Bobzin K. , Zhao L. , Öte M. , Königstein T. 
Published: November 2022

Abstract
Fe-based coatings, such as novel FeCrMnBC alloys, have both economic and ecological advantages compared to other coatings like Ni-based or Co-based coatings. In recent years, high performance Fe-based wear and corrosion resistant coating systems have been developed. Some of them have even been introduced into the market. However, the suitability of the FeCrMnBC alloy as coating for cast iron under complex erosive and corrosive stresses in particle-loaded fluids for pump parts has not been investigated yet. Especially the impact of the process robustness of three-cathode plasma spraying coatings applied with variable process parameters like stand-off distance and spray angle is in the focus of interest. The objective of the present work has been the characterization of novel FeCrMnBC alloys, for the first time deposited via Thermal Spray processes. The corrosion resistances as well as the cavitation and erosion properties were separately evaluated by current density-potential measurements and supersonic cavitation in artificial sea water. Erosion corrosion behavior has been investigated in a pump test rig with 10 wt.-% corundum (Al2O3) particles. The results show that the reduction of spray angle and the variation of stand-off distance limit the corrosion and cavitation resistance in different ways. The erosion behavior shows only small variations for the tested parameters. The results reveal that the FeCrMnBC coatings exhibit high process robustness for the chosen parameter variations and a large potential to improve the protection of cast iron even for not optimized conditions.
Thermal Spraying of Pure Nickel Via HVOF: Effect of Fuel and Shroud Gas Variation on Particle In-Flight Characteristics and Final Coating Properties
Authors: Hambrock C. , Grill C. , Schimo G. , Hassel A.W. 
Published: November 2022

Abstract
In the course of this investigation, thermal spraying with different fuel and shroud gas combinations was investigated in terms of its effect on the in-flight particle properties (temperature, velocity) and on the final coating properties (coating thickness, porosity, oxygen content and corrosion behaviour). Independent on the shroud gas, the particle in-flight temperature and velocity were highest when using ethylene as fuel gas and lowest when using propane. Methylene resulted in intermediate properties. The change in the shroud gas from air to nitrogen generally resulted in lower in-flight particle temperatures and also lower velocity. The coating properties in terms of porosity and oxygen content directly correlated to the particle in-flight properties. With decreasing velocity and increasing temperature, the porosity and the oxygen content increased, respectively. The corrosion behaviour of the nickel coatings was studied in 0.5 M sulfuric acid media by means of potentiodynamic polarization curves. Good corrosion properties were observed when methylene and air served as fuel gas and shroud gas, respectively.
Effect of Composition on the Performance of Coatings for the Protection of Metal Surfaces Against Open Flame
Authors: Ismagilova R. , Baldaev S. , Mazilin I. , Baldaev L. , Fedorova M. 
Published: November 2022

Abstract
High temperature and fire-proof protection of metal structures issue involves formation of dense insulating coatings which possess low thermal diffusivity and capable to withstand high temperatures caused by open flame and other severe conditions. Such coating should be considered as sacrificial as it slowly decomposes during extreme high temperature impact. Such coatings intend significant extension of time required for heating and development of inelastic deformation in metal-based structures increasing service time in severe conditions. Several modifications of fire-proof coatings composed of organic binders were developed and investigated. Fireproof coatings were subjected to open flame test on an adapted burner rig. Open flame simulation with 1100°C was carried to estimate coating’s protection properties. Investigates coating showed reduction of temperature for 1000°C during 10 minutes. Such results achieved due to spumescent effect of coating’s coke layer.
Design of Cold Spray Nozzle to Optimize the Particle Velocity by Numerical Simulation
Authors: Han T. , Li W. , Guo X. , Yang X. 
Published: November 2022

Abstract
This study investigated the accelerating behavior of spray particles during cold spraying (CS) by employing a computational fluid dynamics program, FLUENT. Optimization of the dimensions of CS nozzle was conducted to maximize particle velocity. The results show that the expansion ratio, divergent length, particle density and size, operating temperature significantly influence particle acceleration. It is found that the spray particles in nozzles with long divergent length can obtain a relatively higher impact velocity, but too long divergent length will reduce the particle velocity. Besides, the particle impact velocity shows a downward trend with increasing the particle size or density. Hence, the optimal divergent length should increase with the increase of particle mass. Moreover, higher gas temperature leads to a higher particle velocity, but it has no influence on the optimal divergent length.
Liquid Flame Spray Fabrication of WO3-Graphene Nanocomposite Coatings for Gas-Sensing Applications
Authors: Liu Y. , Huang J. , Gong Y. , Li H. 
Published: November 2022

Abstract
There have been increasing demands for adequate gas sensors to monitor O3, a respiratory irritant gas associated with a spectrum of adverse health events. Here we report film construction by liquid flame spray route and characterization of nanostructured WO3-reduced graphene oxide (rGO) composites and their gas-sensing activities to O3. The starting feedstock was prepared from WCl6 and rGO for pyrolysis synthesis by flame spray. Nanosized WO3 grains exhibited oriented nucleation on rGO flakes and rGO retained intact nano-structural features after the spraying. Constrained grain growth of WO3 was realized in the rGO-containing films with 60-70 nm size as compared to ~220 nm in the pure WO3 film. The WO3-rGO film sensors showed quicker response to O3 and faster recovery than the rGO-free WO3 film sensors. Addition of rGO in 1.0wt.% or 3.0wt.% in the films caused significantly reduced effective working temperature of the film sensors from ~250°C to ~150°C. These results might shed some light on liquid flame spray fabrication of novel functional nanocomposites for gas-sensing applications.
Functional WC Cemented Carbide by the Direct Selective Laser Forming
Authors: Yamada J. , Ibe H. , Sato K. , Kato N. 
Published: November 2022

Abstract
Metal and polymer additive manufacturing is advancing on several applications. On the other hand, materials cermet such as WC/Co for functional structure molding by additive manufacturing are under studying. There are few reports for WC cemented carbide additive manufacturing process by forming with polymer binder then sintering. This indirect process has difficulties to make high precision functional parts due to shape control during additional sintering process. Direct forming is desired for high precision parts. However, factors and/or mechanism to achieve direct formed functional structure have been unclear in many aspects. In this study, the process conditions of the direct selective laser melting were investigated to achieve dense and hard WC cemented carbide mold parts. The optimization of laser melting conditions for WC/Co agglomerated and sintered powder was examined. In order to forming a dense and high hardness parts, the optimum conditions between powder preparation and laser energy density which related with laser power, scan speed and spot diameter were appeared by this experiments. Moldings more than 1500HV are achieved at low laser energy density. However, some of pores were observed in moldings. In addition, the dense molding could be obtained by high laser energy density. This means optimum dense functional WC cemented carbide molding is available by optimization of the molding condition. It is applicable for growing industries like automotive, aviation and cutting tool.
Amorphous Steel Coatings Deposited by HVOF and Cold Gas Spray Processes
Authors: Tului M. , Bezzon A. , Marino A. , Marra F. , Matera S. , Pulci G. 
Published: November 2022

Abstract
This paper considers the deposition of a commercial steel powder with a chemical composition that allows the coating to obtain an amorphous structure using thermal spray techniques. The processes used are characterized by high cooling speeds of the particles after the impact upon the substrate. The powders were sprayed with two different processes: cold gas spray (CGS) and high velocity oxyfuel (HVOF). A comparison between the samples obtained reveals that only the CGS coatings are completely amorphous; the HVOF samples exhibit nanocrystalline phases, detected with XRD analysis and SEM micrographs. Furthermore, the CGS coatings are more compact and show lower hardness with a comparable Young’s modulus. A hypothesis is that the formation of the amorphous structure is related to plastic deformation at impact (due to the high energy of the particles), rather than to the temperature; the mechanism could resemble that of a severe plastic deformation process. Additional thermal treatments and mechanical tests are in progress to investigate the toughness and other mechanical properties of the coatings.
High Velocity Atmospheric Plasma Sprayer
Authors: Chivel Y. 
Published: November 2022

Abstract
An electromagnetic plasma-dynamic system and method for producing high-power plasma flows at atmospheric pressure with high frequency has been developed. In this system, plasma flow velocity reaches 2-4 × 103 m/s at temperatures up to 20 × 103 K. This paper reports results from evaluation of this system for surface layer modification and processing with very high particle acceleration.
Non-Parabolic Isothermal Oxidation Kinetics of Low Pressure Plasma Sprayed MCrAlY Bond Coat
Authors: Zhang B.-Y. , Yang G.-J. , Li C.-X. , Li C.-J. 
Published: November 2022

Abstract
The non-parabolic isothermal oxidation kinetics of low pressure plasma sprayed MCrAlY bond coat was investigated. To qualitatively explain the abnormal growth phenomenon of thermally grown oxides (TGO), the changes that occurred to their microstructure during the oxidation process were studied. Based on these observations, a modified model was developed to understand and quantitatively predict the non-parabolic oxidation and growth kinetics of TGO. This modified model, which fits well with experimental results, provides a novel method to quantitatively predict the long-term growth behaviour of TGO, and thereby benefits the development of long-life and highly reliable thermal barrier coatings.
Micro Structure and Characterization of Hydroxyapatite Coating (HAP) by Rod Flame Spray Process
Authors: Upadhyaya R. , Shrivastava S. , Modi S. C. , Modi A. 
Published: November 2022

Abstract
Hydroxyapatite (HAP) is available in powder form for plasma spraying. HAP powder was fabricated indigenously in the Rod form of diameter 4.17mm. This rod was sprayed with the help of MEC make Rodojet 9810 (flame spray process). Rodojet parameter were optimised for HAP rod. Crystallinity and purity level of HAP rod was measured. XRD and SEM were used to analysed the microstructure of rod and coating. The microstructure, mechanical properties of the coating were investigated, and measure the Ca/P ratio of coating and rod. The micro-hardness and elastic modules were determined by indentation tests and bond strength was determined by tensile test. The results showed that the microstructure, mechanical properties was observed same as in plasma spray process. Porosity was observed more than 15%. The bond strength of coating was observed 20 MPa. Scratch test was done to measure the cohesive strength of coating. This new experiments play an important role for reduction the cost of the HAP powder coating.
Development of Methodology of Cohesive Strength Evaluation of Thermally Sprayed Coatings
Authors: Schubert J. , Česánek Z. 
Published: November 2022

Abstract
Measuring the cohesive strength of thermally sprayed coatings is relatively difficult matter, which can be accessed in many directions. This issue is nowadays solved by use of Scratch test method. This method is not completely sufficient for the cohesive strength testing because the coating is under load of combined stresses during the Scratch test. The reason to develop this method was need for exact measurement of tensile cohesion toughness of thermally sprayed coatings, which could provide results as close to a classic tensile test as possible. Another reason for development of this method was the impossibility of direct comparison with results obtained by other methods. Tested coatings were prepared using HP / HVOF (Stellite 6, NiCrBSi, CrC-NiCr and Hastelloy C-276). These coatings were selected as commonly used in commercial sector and on because of rising customer demand for ability to provide such coating characteristics. The tested coatings were evaluated in terms of cohesive strength (method based on tensile strength test). Final fractures were evaluated by scanning electron microscopy and EDS analysis. As expected higher cohesive strength showed metallic coatings with top results of coating Stellite 6. Carbide coatings showed approximately third of the cohesion strength in comparison with metal based coating.
Investigation of Microstructure and Mechanical Properties of Alumina-Titania Coatings by Flexicord Flame Spraying
Authors: Altincu E. , Ustel F. 
Published: November 2022

Abstract
Thermally sprayed Al2O3-TiO2 coatings were in the area of interest over the last decade because they showed improved wear properties over conventional coatings. In this study, flexicord flame spray gun was used to deposit Al2O3-TiO2 coatings at different spray parameters. The microstructural morphology variation and phase transformation of coatings were investigated. In addition, as one of the most important properties for ceramic coatings, hardness, solid particle abrasive wear resistance of coatings were measured before and after heat treated condition. Test results show that the higher mechanical properties and wear resistance by the heat treatment at elevated temperatures.
Evaluation of Low-Pressure Cold Spray MMC Coatings by Acoustic Emission-Coupled Four-Point Flexural Testing
Authors: Lee Y. T. R. , Shibly M. , Hussain T. , Fisher G. , McDonald A. 
Published: November 2022

Abstract
Low-pressure cold spray has been used as an innovative method to deposit metal matrix composite (MMC) coatings: boron carbide-nickel (B4C-Ni) and tungsten carbide-cobalt-nickel (WC-Co-Ni) composites. The coatings were studied using scanning electron microscopy, X-ray diffraction with Rietveld refinement, and acoustic emission-coupled four-point flexural test. Indentation fracture toughness tests were performed on the WC-Co-Ni coatings, only. The results showed that the composites had reinforcing particle volume fractions of 45.8 ± 0.3 vol.% and 22.7 ± 0.1 vol.% for the WC-Co-Ni and B4C-Ni MMC coatings, respectively. Flexural tests were used to evaluate the fracture strain of the composites. In these tests, the WC-Co-Ni composite failed by brittle facture at approximately 0.5% nominal strain. The B4C-Ni composite showed flexural behaviour similar to that of an unreinforced Ni matrix. These results suggest that there was insufficient B4C within the coating to affect significantly the ductile failure mode of Ni matrix. Post bending fracture analysis showed the presence of straight, continuous cracks on the WC-Co-Ni surface and the indentation fracture toughness of WC-Co-Ni was found to be 1.2 ± 0.2 MPa·m0.5. Discontinuous, random cracks were observed on the B4C-Ni surface. The quantification of these properties is essential in evaluating the performance of the low-pressure cold sprayings to determine their potential applications.