bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deposition Mechanisms of Cold Gas Dynamic Sprayed MCrAIY Coatings
Authors: Ichikawa Y. , Sakaguchi K. , Ogawa K. , Shoji T. , Barradas S. , Jeandin M. , Boustie M. 
Published: September 2022

Abstract
Thermal-sprayed (i.e. LPPS or HVOF) MCrAlY coatings are widely used for land-based gas turbine applications against high-temperature oxidation and hot corrosion. However, due to requirement for further improvement of turbine efficiency, dense and stable coatings are necessary. The cold spray (also referred to as cold gas dynamic spray) makes it possible to increase coating density, due to high velocity particle impact during spraying. However, deposition mechanisms of cold spraying have not been elucidated yet. In this study, we investigated the deposition mechanisms focused on the behavior of interface between a coating and a substrate. The mechanisms were evaluated by the spray impact phenomena simulation tests, namely laser shock flier impact tests, and STEM-EDX elemental analyses at the interface between the substrate and the cold sprayed coating. From the results of STEM-EDX for as-sprayed coating and of SEM-EDX of the flier specimen, the bonding between the CoNiCrAlY coating and the substrate occurred at the only particular phase combination.
Oxidation Effects on the Critical Velocity of Pure Al Feedstock Deposition in the Kinetic Spraying Process
Authors: Kang K.C. , Yoon S.H. , Ji Y.G. , Lee C. 
Published: September 2022

Abstract
In the kinetic spraying process, the critical velocity is an important criterion which determines the deposition of a feedstock particle onto the substrate. It was experimentally and numerically proven that the critical velocity is determined by the physical properties and the state of materials such as initial temperature, size and the extent of oxidation. Compared to un-oxidized feedstock, oxidized feedstock required a greater kinetic energy of the in-flight particle to break away the oxide film during impact. The oxide film formed on the surface of particle and substrate is of a relatively higher brittleness and hardness than those of general metals. Because of its physical characteristics, the oxide significantly affected the deposition behavior and critical velocity. The effects of oxidation on the critical velocity and the deposition behavior of the feedstock were investigated and evaluated by individual particle impact tests in this study. The velocity of pure Al particles was measured for a wide range of process gas conditions.
Deposition Characteristics of Al-12Si Alloy Coating Fabricated by Cold Spraying with Relatively Large Powder Particles
Authors: Li W.-Y. , Zhang C. , Guo X.P. , Liao H.L. , Coddet C. 
Published: September 2022

Abstract
In this paper, the microstructure and microhardness of the Al-12Si coating produced by cold spraying with a relatively large powder were investigated. It is found that a thick, dense and well bonded Al-12Si coating could be produced by cold spraying with a relatively large powder through the control of spray conditions. The critical velocity for large Al-12Si particles was about 500 m/s under the spray conditions in this study. The as-deposited coating had the same phase as the Al- 12Si powder. The localized interface melting occurred resulting from both the adiabatic shearing upon impact and the thermal effect of hot gas. The precipitation of fine Si particles occurred in α-Al matrix in the coating deposited at an elevated gas temperature because of the thermal effect of hot gas during coating deposition. The dispersed Si particles in the coating improved the coating microhardness.
Effect of Process Parameters on the Deposition Characteristics of a Bronze-20 vol.% Diamond Composite in Kinetic Spraying
Authors: Shin S. , Lee C. , Han K.T. , Kim H.J. 
Published: September 2022

Abstract
The aim of this study was to ascertain the optimal process parameters that minimized compositional variation between the original powder mixture and composite coating. A bronze- 20 vol.% diamond composite powder was deposited by a kinetic spraying process with various feed rates, spraying distances and particle velocities. Experimental results showed that the diamond fraction, deposition efficiency and bond strength were dependent on process parameters, in particular, the particle velocity.
Microstructural Characterization of Cold-Sprayed Nanostructured FeAl Intermetallic Compound Coating and its Ball-Milled Feedstock Powder
Authors: Wang H.-T. , Li C.-J. , Yang G.-J. , Li C.-X , Zhang Q. , Li W.-Y. 
Published: September 2022

Abstract
It is difficult to deposit dense intermetallic compound coatings by cold spraying directly using the compound feedstock powders due to their intrinsic low temperature brittleness. A method to prepare intermetallic compound coatings in-situ employing cold spraying was developed using a metastable alloy powder assisted with post-annealing. In this study, a nanostructured Fe/Al alloy powder was prepared by ball-milling process. The cold sprayed Fe/Al alloy coating was evolved in-situ to intermetallic compound coating through a post-annealing treatment. The microstructural evolution of the Fe-40Al powder during mechanical alloying and the effect of the post-annealing on the microstructure of the cold sprayed Fe(Al) coatings were characterized by optical microscopy, scanning electron microscopy and X-ray diffraction analysis. The results showed that the milled Fe-40Al powder exhibits lamellar microstructure. The microstructure of the as-sprayed Fe(Al) coating depends significantly on that of the as-milled powder. The annealing temperature significantly influences the in-situ evolution of the intermetallic compound. The annealing treatment at a temperature of 500oC results in the complete transformation of Fe(Al) solid solution to FeAl intermetallic compound.
Improvement of Plasma Gun Performance using Comprehensive Fluid Element Modeling: Part 1
Authors: Muggli F. , Molz R. , McCullough R. , Hawley D. 
Published: September 2022

Abstract
The use of computational fluid dynamics (CFD) to model the operation of thermal spray processes has gained interest in the thermal spray community, able to provide an understanding as to how a process functions, and better yet how to make a process work better. Advancements to the science of modeling now permits the ability to create a comprehensive model of a plasma gun that not only simulates the dynamics of the gas but also the mechanics of arcs (plasma), thermodynamics, and entrained particulates to form a nearly complete model of a working thermal spray process. Work presented includes the methods and procedures used to validate the model to a Sulzer Metco TriplexPro 200 plasma gun and exploration of the operating regime to give an in depth and insightful look into the physics behind the operation of a triple arc cascaded plasma gun.
Numerical Simulations of Cascaded Plasma Torch Using Ar and Molecular Gases
Authors: Chen L. , Mostaghimi J. , Pershin L. 
Published: September 2022

Abstract
In this work, plasma flow inside a cascaded DC torch, effect of a plasma gas composition (Ar or CO2+CH4), and torch performance were studied. Both laminar model and k-ε turbulence model were employed and compared in the simulations. The results revealed that carbon contained gases can significantly increase the arc voltage and torch power. This gas mixture increases the arc voltage by up to 200% in comparison with argon. Voltage-current characteristics were also simulated for the current range of 200-400A. Differences in the torch performance can be attributed to the gases specific properties. For instance, at the same temperature the considered plasma gases have similar electric conductivities but the enthalpy of molecular CO2+CH4 is much higher. Experimental validation indicates that k-ε turbulence model provides better agreement.
Flame Flow Analysis for HVOF/HVAF System by Two-Dimension Computational Fluid Dynamics Method
Authors: Genliang H. , Kewei X. 
Published: September 2022

Abstract
Based on the principle of the liquid-fueled rocket engine, a combustion model is proposed for the HVOF/HVAF system. The combustion gas components and temperature for different mixture fractions were analyzed. At lower oxygen content condition (under-stoichiometry), the combustion temperature is lower and the solid carbon content is higher. The whole fluent flow mode was proposed for the supersonic spray, which consists of the gas combustion, the accelerating process, the cooling process and the decelerating process in the atmosphere. The velocity and temperature distributions were calculated according to this model; the results fitted well with experiments. The combustion gas parameter distributions are almost identical in the barrel, but differ significantly in the atmosphere. For HVOF system, the under-expanded gas will expand in the atmosphere, while HVAF system exhibits an opposite behavior. At the gun exit, the combustion gas reaches supersonic velocities both for the HVOF and HVAF condition.
Modeling of an Inductively Coupled Plasma for the Synthesis of Nanoparticles
Authors: Bolot R. , Coddet C. , Shreuders C. , Leparoux M. , Siegmann S. 
Published: September 2022

Abstract
Nanoparticles show novel properties compared to the bulk material of same chemistry. The small size is responsible for many changes in the thermo-physical properties. Thus, there was an increasing interest in nanomaterials since the past five years. Among other methods, inductively coupled plasma (ICP) torches can be used for the synthesis of nanoparticles. In this process, the precursor material is vaporized in a first step in the plasma core. In a second step, nucleation and condensation occur in the synthesis chamber where the plasma gets colder and form high-purity nanoparticles, the growth of which is stopped by gas quenching. From their low velocity and high temperature, induction plasmas are particularly adapted for this application. Numerical modeling is a good way to achieve a better knowledge and understanding of the process. In the present paper, a two-dimensional model of an inductively coupled plasma torch was developed and validated on the basis of comparisons with data obtained by some other authors. Finally, the current frequency (13.56 MHz), pressure level (400 mbar) and gas flow rates were adjusted for the specific conditions of nanoparticles synthesis.
Unsteady 3D Large Eddy Simulation of an Ar-H2 Plasma Jet: Analysis of Initial Results
Authors: Balmigere G. , Meillot E. , Vincent S. , Caltagirone J.-P. 
Published: September 2022

Abstract
Suspension plasma spraying (SPS) is of great interest for the realization of thin nanostructured coatings. The thermokinetic phenomena involved in the SPS process, from the plasma/liquid interaction to the growth of the coating are difficult to forecast and experiment. The present work focuses on the 3D simulation of an Ar-H2 (45-15 slm) plasma jet issuing into ambient air. A large eddy simulation model accounts for turbulence and provides us with the instantaneous temperature and velocity fields of the plasma flow. The results obtained with the CFD library AQUILON are compared to experimental ones as well as previous simulations realized with a commercial software.
Molecular Dynamics Simulation of Flattening Process of a High-Temperature, High-Speed Droplet: Influence of Impact Parameters
Authors: Shimizu J. , Ohmura E. , Kobayashi Y. , Kiyoshima S. , Eda H. 
Published: September 2022

Abstract
Three-dimensional molecular dynamics simulation was conducted to clarify at an atomic level the flattening process of a high-temperature droplet impacting a substrate at high speed. The droplet and the substrate were assumed to consist of pure aluminum, and the Morse potential was postulated between a pair of aluminum atoms. In this report, the influences of the impact parameters, such as the droplet velocity and the droplet diameter on its flattening behavior were analyzed. As a result, following representative conclusions were obtained: (1) the flattening ratio increases in proportion to the droplet velocity and the droplet diameter; (2) the flattening ratio for nanosized droplet can be rearranged by the same dimensionless parameters of the proper physical properties, such as the viscosity and the surface tension, as those used in the macroscopic flattening process.
Comparison of Molecular and Argon Gases for Plasma Spraying
Authors: Pershin L. , Chen L. , Mostaghimi J. 
Published: September 2022

Abstract
Thermal spray torches commonly use argon for plasma generation. Low thermal properties of argon, however, limit the thermal efficiency of the torches. Use of molecular gases, which must dissociate before ionization, requires larger energy input resulting in enthalpy increase of the plasma. In this paper, the effect of various gas compositions (Ar, Ar+H2, and CO2+CH4) on the torch voltage-current characteristics, power and thermal efficiency were studied. At the same time, in-flight YSZ particle conditions were compared. The higher thermal conductivity and efficiency of CH4+CO2 gas mixture produce more favorable sprayed particle conditions, in particular temperature. At a 50mm spray distance, YSZ particle temperatures were 2470°C and 2896°C for Ar+H2 and CH4+CO2, respectively. Typical arc voltage for the torch operating in CO2+CH4 was 130-180V compared to 45-60 V for Ar+H2. Thermal efficiency was also 20-40% higher.
Study on Cold Spraying of Al-based Brazing Alloys
Authors: Lugscheider E. , Bobzin K. , Zhao L. , Ernst F. , Zwick J. 
Published: September 2022

Abstract
The cold spray process is interesting for brazing technology due to its special properties: low oxidation of spray materials and rupture of oxide scales on the substrate and particles surfaces during deposition. In the present study, two brazing alloys AlSi12 and AlSi10Cu4 were deposited onto 6063 and 3003 aluminium alloys using the cold spray process. The influence of the spray parameters on the particle velocity was investigated by means of DPV 2000. The influence of spray materials and parameters on coating build up and on coating microstructure was investigated. Some of the AlSi12 coated samples were heat-treated at 500 and 600 °C to investigate the effect of the rupture of oxide scales on the diffusion processes. Some of the AlSi12 deposited samples were brazed under argon atmosphere using a flux or without any fluxes. The results show that the process gas temperature influenced the particle velocity and the deposition behaviour of the powders significantly. The AlSi12 powder showed a much better deposition behaviour than the AlSi10Cu4 powder. Due to the rupture of oxide scales, silicon in the brazing alloy coating could diffuse into the substrate. The brazed samples show a very good bond between the substrate and the brazing alloy.
Investigation about the Chrome Steel Wire Arc Spray Process and the Resulting Coating Properties
Authors: Wilden J. , Bergmann J.P. , Jahn S. , Knapp S. , van Rodijnen F. , Fisher G. 
Published: September 2022

Abstract
Nowadays wire arc spraying of chromium steel has gained an important market share for corrosion and wear protection applications. In order to optimize the process parameters and to evaluate the effect of the spray parameters DoE based experiments have been carried out as well. In this paper, the effects of the process parameters of spray current, voltage and atomizing gas pressure on the particle jet properties of mean particle velocity and mean particle temperature as well as plume width are presented. To monitor these values the AccuraSpray system was used. The properties of the coatings with regard to morphology, composition and phase formation are included as well. These investigations are part of the development of new power supplies and the enhancement of spray parameter range. As a result of these experiments the spray parameters can be adjusted according to the requirements of the chromium steel coatings.
New Process Adapted Power Supplies for Wire Arc Spraying
Authors: Knapp S. , van Rodijnen F. , Fischer G. 
Published: September 2022

Abstract
The precondition of a cost efficient wire arc spraying process is an ideal process setup according to the wire material. Modern power supplies are equipped with electronic control circuits to ensure stable arc conditions at the wire tips. This is necessary for high quality wire arc sprayed coatings. The key factors to achieve this are the arc energy and fluid mechanics as well. By the use of a PID controller to maintain set spray parameters, it is possible to reduce the spray voltage down to 15 V for zinc as feedstock material. Furthermore temperature dependent parameter fluctuations can be compensated with the electronic controller, while working at maximum capacity with one hundred percent duty cycle. The paper discusses the influence of a new power supply with regard to the process stability and the enhancement of former power supply based process limitation as well as the operator guidance.
A New Method for the Production of Particle Reinforced Coatings
Authors: Wilden J. , Bergmann J.P. , Jahn S. , Reich S. , Knapp S. , van Rodijnen F. , Fischer G. 
Published: September 2022

Abstract
A method for the production of particle reinforced coatings by wire arc spraying will be presented in this paper. This technology is based on twin-wire electric arc spraying (TWEA) process. Here, additional particles were injected into the atomizing gas stream and sprayed in a non molten state along with wire feedstock material onto the substrate. According to the reinforcing particles, the process can be applied to produce coatings with a high wear resistance as well as a high surface roughness. In a wide range of applications, these coating characteristics are required. Due to economic constraints, coatings of large surfaces have to be done in short times at low costs. Based on wire arc spraying, the thermal spray process with the highest deposition performance, the mentioned industry requirements can be fulfilled.
Influence of Microstructure on the Thermal Cycling Performance of Thermal Barrier Coatings
Authors: Vaßen R. , Stöver D. 
Published: September 2022

Abstract
Thermal barrier coatings (TBCs) with different types of microstructures were produced with the atmospheric plasma-spraying (APS) process. The investigation includes a variation of the micro-crack density and of the porosity level. In addition, also segmented TBCs were produced. Finally, also PVD-TBC systems have added to the investigation. The different TBC systems were cycled in a natural gas/oxygen burner rig with a surface temperature of about 1250°C and a bond coat temperature of about 1100°C or below. The use of relatively low surface temperature guarantees a failure mode close to the bond coat promoted by the growth of the thermally grown oxide (TGO). After failure, metallographic inspection was made to determine the thickness of the TGO layer and the β-phase depleted zone. In addition, the crack path was analyzed and compared for the different microstructures.
Thermal Fatigue Behaviour of Thick and Porous Thermal Barrier Coatings Systems
Authors: Scrivani A. , Rizzi G. , Bardi U. , Giolli C. , Muniz Miranda M. , Ciattini S. , Fossati A. , Borgioli F. 
Published: September 2022

Abstract
High temperature thermal fatigue causes the failure of Thermal Barrier Coating (TBC) systems. This paper addresses the development of thick TBCs, focusing attention on the microstructure and the porosity of the Yttria Partially Stabilized Zirconia (YPSZ) coating, in relation to its resistance to thermal cycling fatigue. Thick TBCs, with different grade of porosity, were produced by means of a CoNiCrAlY bond coat and Yttria Partially Stabilised Zirconia top coat, both sprayed by Air Plasma Spray. The thermal fatigue resistance of new TBC systems and the evolution of the coatings before and after thermal cycling were evaluated. The limit of thermal fatigue resistance increases with amount of porosity in the top coat. Raman analysis shows that the compressive in-plane stress increases in the TBC systems after thermal cycling, nevertheless the increasing rate has a trend contrary to the porosity level of top coat.
The Growth and Influence of Thermally Grown Oxide in a Thermal Barrier Coating
Authors: Wu X.J. , Chen W.R. , Patnaik P.C. 
Published: September 2022

Abstract
The growth characteristics of thermally grown oxides (TGO) and their influence on microcracking in an air-plasma sprayed (APS) thermal barrier coating (TBC) were studied. The TBC samples were prepared in either as-received condition or with a pre-heat treatment. In the as-received TBC, TGO that formed upon thermal exposure predominantly consisted of layered and clustered chromia, spinels and nickel oxide, whereas in pre-heat treated samples the TGO was predominantly alumina. The growth characteristics of TGO was found to exhibit a three-stage behavior that was most pronounced in the as-received TBC. Micro-cracks were found to nucleate in clustered oxides, these cracks would grow in association with thickening of the TGO layer. Eventually, oxide-induced cracking and cracking along pre-existing discontinuities near the ceramic/bond coat interface led to spallation of the topcoat. A relationship between the maximum crack size and TGO thickness was established based on fracture mechanics considerations. This relationship is shown to be useful for TBC life prediction.
Microstructure and Thermal Cycling Behaviors of Thermal Barrier Coatings on Near-α Titanium Alloy
Authors: He B. , Li F. , Zhou H. , Dai Y. , Sun B. 
Published: September 2022

Abstract
Two kinds of thermal barrier coatings with NiCoCrAlY bond coatings (BCs) deposited by electron beam-physical vapor deposition (EB-PVD) and high velocity oxy-fuel thermal spraying (HVOF), respectively, as well as their top 8wt.%Y2O3-ZrO2 (YSZ) ceramic layers deposited in one batch by EB-PVD were prepared on near-α titanium alloys. The field emission scanning electronic microscopy and microhardness indentation are used in comparatively study of microstructures, microhardness of samples. Cracking modes and crack characteristics in TBCs are investigated after thermal cycling in atmosphere, along with the discussion of roles of residual stresses, bonding strengths and mechanical properties of bond coatings in different failure extents. It is found that morphologies of BCs deposited by different methods (EB-PVD and HVOF) result in the different microstructures and microhardness of their upper YSZ. The denser and more homogeneous BC prepared by EB-PVD leads to the YSZ with finer and denser columnar clusters and higher microhardness, and the inhomogeneous and porous latter results in the upper YSZ with coarser and loosely bonded columnar grains and lower microhardness, and the TBC with BC deposited by EB-PVD is more protective, which is synthetically induced by residual stresses, bonding strengths and mechanical properties of bond coatings.
Making Dense Coatings with the Solution Precursor Plasma Spray Process
Authors: Jordan E.H. , Gell M. , Bonzani P. , Chen D. , Basu S. , Cetegen B. , Wu F. , Ma X. 
Published: September 2022

Abstract
The Solution Precursor Plasma Spray process allows the creation of coatings directly from chemical precursors, thus avoiding the task of making sprayable powders. To date, our research has been based on injecting chemical precursors into a DC plasma torch. The process has proven to be useful in making vertically cracked thermal barrier coatings and has shown special advantages for making thick thermal barrier coatings (up to 4 mm). More recently, the process has been modified to produce dense, crack free coatings. This development was enabled by an improved understanding of the process, including making a coating almost exclusively from ultra-fine splats and avoiding the formation of vertical cracks. A crack free, dense alumina-yttria stabilized zirconia coating has been produced which is 98% dense and has an average Vickers hardness (300 gf) of 1177.