bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Microstructure on Thermal and Optical Properties of Suspension Plasma Sprayed (SPS) and Atmospheric Plasma Sprayed (APS) Coatings
Authors: Kaßner H. , Stuke A. , Vaßen R. , Stöver D. 
Published: September 2022

Abstract
Normally the conventional thermal spray processes as the atmospheric plasma spraying (APS) have to use easily flowable powders in a size range between 10 and 100 µm. In contrast the suspension plasma spraying (SPS) makes it possible to process nano sized particles directly. Due to the use of nano materials new microstructures and properties could be generated. One point is the possibility to influence the porosity level, its size range and micro crack densities in a wide band. Microstructure features like the porosity and cracks serve as scattering centres and lead to changes of optical properties. Furthermore the thermal conductivity is affected by the porosity level. In this work yttria partially stabilized zirconia coatings were generated by the SPS and APS process. The influence of the different microstructures on the thermal conductivity, the hemispherical reflectance and transmittance for wavelengths between 0.3 to 2.5 µm has been investigated. Due to the higher porosity and crack level of the SPS coatings the thermal conductivity and hemispherical transmittance was significant reduced.
Advanced Production of Thermally Sprayed Prepregs for Unidirectional Fiber-Reinforced Light Metal MMCs
Authors: Silber M. , Gadow R. 
Published: September 2022

Abstract
Thermal spraying and thixoforging technologies can be combined in a new manufacturing method for the production of light metal matrix composites. Laminated prepregs are produced by coating unidirectional fiber bundles with light metal matrix material. The prepregs are heated up and densified by thixoforging to near net-shape composites. Compared to conventional technologies for the integration of fibers in light metal matrices, like squeeze casting, hot pressing and diffusion bonding, this method offers the possibility to realize complex component geometries with short cycle times. Due to its high deposition rate and reduced thermal load on the substrate, the arc wire spraying technique is used for the coating of fiber bundles with the matrix material (AlSi6). The final fiber volume content of the MMC can be tailored by the thickness of the coating. Prior to the coating process, a continuous fiber strand is coiled on a cylindrical workpiece with adapted dimensions by using a winding unit provided with fiber guiding system. The speed and horizontal range of the fiber guide unit can be continuously varied in order to control overlapping and ensure homogeneous thickness of the fiber layer. An efficient air cooling system is installed in order to control the thermal load, which affects the formation of microcracks and influence the final residual stress distribution in the coating. An innovative method to wind and coat continuous fibers for manufacturing fiber reinforced light metal matrix composites will be presented.
Peculiarities of Abrasive Wear of PEO Layers Obtained on Arc Sprayed Aluminium Coatings
Authors: Wielage B. , Pokhmurska H. , Grund T. , Meyer D. 
Published: September 2022

Abstract
Different post treatment methods are developed up to now to improve the properties of thermally sprayed coatings. In this work, arc sprayed aluminium coatings on aluminium substrates are post-treated by plasma electrolytic oxidation. To estimate the wear resistance of resulting oxide coatings, two abrasive wear tests (ASTM G65 and ASTM C1624) are carried out. Worn surfaces are examined by scanning electron microscopy in order to establish the wear mechanisms. These results of the abrasive wear tests are correlated with the parameters of the PEO process and the hence resulting micro structures of the coatings.
Characterisation of Thermally Sprayed Near Net Shape Oxide Ceramic and Cermet Coatings by Acoustic Emission Analysis
Authors: Bach F.-W. , Möhwald K. , Erne M. , Bause T. , Scheer C. 
Published: September 2022

Abstract
Near net shape coating is a trend in thermal spraying being aimed at for several years to lower costs through shortened spray time and reduced after treatment work. Because of better microstructure compared to conventional coatings, the thickness is often also reduced. To characterise the quality of those thin layer systems the standardized tensile adhesive test is not suitable, as the adhesion outweighs the cohesion by far due to reduced quantities of coating defects. To characterize the coatings behaviour under tensile stress, three-point bending tests were performed. As especially thin cermet coatings do not show abrupt catastrophic failure in bending tests, ultrasonic signals being emitted from cracks propagating through the coatings were taken during the tests. Three coating systems (Cr2O3, Cr3C2-NiCr and WCCoCr) were investigated in this work using fine grained feedstock powders with three different size distributions per system. The tests showed the negative influence of stress moments in case of the oxide ceramic and the embrittlement of the cermets, especially the Cr3C2-NiCr, with increasing spraying temperature regime due to increased formation of solid solutions and decarburization. It can be said, that the analysis of acoustic emission during bending tests gives valuable information about how to achieve thin wear and corrosive protecting coatings being qualified for high operational demands.
Investigation of Composites: Metal – Ceramics and Metal – Metal Coatings Produced with Cold Spray Equipment with Ejector
Authors: Papyrin A. , Kosarev V. , Klinkov S. , Sova A. , Smurov I. , Bertrand P. 
Published: September 2022

Abstract
This paper presents some results of investigation of the cold spraying various composites including metal-ceramics, metal-metal with a new nozzle design. The objective of this study was to develop a nozzle with an ejector that allows the injection of powder components in different points of the gas flow that can provide optimal spray parameters for each component. For this purpose the installation was equipped with three feeders and three powder feed ports. The first one was located in a pre-chamber (high pressure powder feeder) and two others were located in the ejector in supersonic part of the nozzle. Varying the powder injection location of any component allowed us to change the spray parameters of the mixture. Some preliminary spray results of different powder mixtures are presented to illustrate possibilities of such approach. It is shown that an addition of ceramic or metal powder to the sprayed metal can significantly change the spray process and coating characteristics
High Pressure Cold Spray Produced Bulk Forms
Authors: Karthikeyan J. , Kay C.M. 
Published: September 2022

Abstract
The footprint of a cold spray beam has narrow dimensions and a large particle density, which lead to fast growth of deposit on precise locations. Cold spray produces compressively stressed coatings which lead to well bonded ultrathick coatings over many substrates. Since cold spray produces dense coatings with wrought-like microstructure, it can be used to produce large bulk forms. Two different bulk forms were produced: (i) ultrathick coatings strongly bonded to substrates and (ii) free standing structures (FSS). Both forms were post machined to obtain net-shape or near-net-shape articles. Bulk forms up to 60 mm were produced with many powders including metals, alloys and composites. Well bonded ultrathick coatings were produced over many substrates including aluminum, copper, SS, etc. FSS, including pipes, plates, etc, were produced by fabrication of a mandrel, spray coating bulk forms and removal of the mandrel. Coatings in the as-sprayed condition were machined and fine features such as grooves incorporated to obtain net-shape articles.
How Cold is Cold Spray? An Experimental Study of the Heat Transfer to the Substrate in Cold Gas Dynamic Spraying
Authors: Irissou E. , Legoux J.-G. , Moreau C. , Ryabinin A.N. 
Published: September 2022

Abstract
Time-resolved thermographic measurements were performed by a high speed infrared camera on a substrate surface during cold gas dynamic spraying without powder particles. Experiments were carried out on three commercial cold spray systems (Centerline SST, CGT Kinetiks 3000 and Inovati KM-CDS 2.2) spanning a wide range of gas pressures, gas temperatures, gun traverse speeds and stand-off distances. The substrate surface temperatures were measured directly beneath the cold spray gun nozzle as well as at predetermined distances from the gun giving a general evaluation of the heat input to the substrate in actual deposition conditions. It is shown that the substrate surface temperature can rise to a value close to the inlet gas stagnation temperature in the area located beneath the cold spray gun (bow shock region). For the same set of process conditions, significant differences were found in measured surface temperature range between the three cold spray systems, due to differences in nozzle configuration.
Particle Image Velocimetry of Cold Spray CP Titanium
Authors: Zahiri S.H. , Jahedi M. , Yang W. 
Published: September 2022

Abstract
Titanium is widely used in aerospace, highly corrosive environments and implants due to unique properties such as high strength to weight ratio and excellent corrosion resistance. Cold gas dynamic spray (cold spray) technology in contrast to current fabrication technologies has provided the potential for titanium to be utilised in broader industrial applications and at lower cost. Particle velocity is the most important parameter in cold spray process that leads to successful deposition of titanium at supersonic speeds. In this study, particle image velocimetry (PIV) is used to determine particle velocities for a commercially pure (CP) titanium powder in respect to cold spray parameters such as temperature and pressure. The results show the significance of flow field measurements using PIV in optimization of the nozzle configuration to achieve the maximum velocity for particles. Further more, PIV results can be used to validate the current models developed for cold spray process.
Introduction to High Velocity Suspension Flame Spraying (HVSFS)
Authors: Gadow R. , Killinger A. , Rauch J. 
Published: September 2022

Abstract
High Velocity Suspension Flame Spraying (HVSFS) has been developed to thermally spray suspensions containing micron, sub micron and nanoparticles with hypersonic speed. For this purpose, the suspension is introduced directly into the combustion chamber of a modified HVOF torch. The aim in mind is to achieve dense coatings with a refined microstructure. Especially from nanostructured coatings superior physical properties are expected for many potential applications. Direct spraying of suspensions offers flexibility in combining and processing different materials. It is a cost saving process and allows the allocation of entirely new application fields. The paper gives an overview of the HVSFS spray method and will present some actual results that have been achieved by spraying the nanooxide ceramic materials Al2O3, TiO2, 3YSZ and Cr2O3.
Designing and Integrating A Semi Automated Powder Feed Device to Produce Functionally Graded Materials (FGM) using the HVOF Thermal Spray Process
Authors: Al Mamun M.K. , Hasan S. , Hasan M. , Hashmi S. , Stokes J. 
Published: September 2022

Abstract
The application of FGMs is quite difficult, but thermal spray processes like Plasma spray have demonstrated their unique potential in producing graded deposits, where researchers have used twin powder feed systems to mix different proportions of powders. FGMs vary in composition and/or microstructure from one boundary (substrate) to another (top service surface), and innovative characteristics result from the gradient from metals to ceramics or non-metallic to metals. The present study investigates an innovative modification of a HVOF (High Velocity Oxy- Fuel) thermal spray process to produce functionally graded thick coatings. In order to deposit thick coatings, certain problems have to be overcome. Graded coatings enable gradual variation of the coating composition and/or microstructure, which offers the possibility of reducing residual stress build-up with in coatings. In order to spray such a coating, modification to a commercial powder feed hopper was required to enable it to deposit two powders simultaneously which allows deposition of different layers of coating with changing chemical compositions, without interruption to the spraying process. Various concepts for this modification were identified and one design was selected, having been validated through use of a process model, developed using ANSYS Flotran Finite Element Analysis. In the current research the mixing of different proportions of powders were controlled by a computer using LabVIEW software and hardware, which allowed the control and repeatability of the microstructure when producing functionally graded coatings.
Effects of Diffusion Treatment on the Interface Microstructure Between Thermally Sprayed Cobalt-Based Self-Fluxing Alloy Coating and Steel Substrate
Authors: Sakata K. , Fujita S. , Miyahara H. , Ogi K. 
Published: September 2022

Abstract
Effects of diffusion treatment were investigated on the interface microstructure between a Co-based self-fluxing alloy coating and a mild steel substrate to improve the adhesion strength. Diffusion treatments were carried out at 1373 K to 1418 K for 600 s to 7200 s in an Ar atmosphere. Diffusion treatment improves the metallurgical bonding at the interface due to the diffusion of Co, Cr, W, Ni, and Si from the sprayed coating layer to the substrate and that of Fe and Mn from the substrate to the coating. This mutual diffusion forms a precipitate-free diffusion layer at the interface, and the width of this layer increases in a parabolic manner as temperature and holding time increase. The apparent activation energy for the formation of precipitate-free diffusion layer was evaluated as about 360 kJ/mol. The shearing adhesion strength of the diffusion-treated coating has been remarkably improved to 200 – 400 N/mm2 in proportion to the width of the precipitate-free diffusion layer formed along the interface, although the shearing adhesion strength of the as-sprayed coating was only 30 N/mm2.
Fast Regime – Fluidized Bed Machining (FR-FBM) of Thermally Sprayed Coatings
Authors: Barletta M. , Rubino G. , Bolelli G. , Lusvarghi L. , Bassani A. 
Published: September 2022

Abstract
Finishing of thermally sprayed metallic, ceramic and cermet coatings is required in order to meet tolerances and requirements on surface roughness in most industrial applications. Conventional machining is a costly and time-consuming process, difficult to automate. Therefore, this study investigates and develops a new technique highly amenable for automation: Fast Regime - Fluidized Bed Machining (FR-FBM). Atmospheric Plasma Sprayed (APS) TiO2, Cr2O3 and HVOF-sprayed WC-17%Co and Tribaloy-800 coatings, deposited on AISI 1040 steel substrates, were subjected to FR-FBM treatment. The effects of the leading operational parameters, namely, abrasive size, jet pressure and processing time, were evaluated on all coatings by using a two/three-levels full factorial Design Of Experiments (DOE). The FR-FBM treated surfaces were observed by FE-SEM and their surface finishing was evaluated by contact profilometry. Significant improvements in surface finishing of all the machined thermally sprayed coatings can always be detected, with FR-FBM being able to guarantee the precision and the respect of the closest geometrical tolerances.
Correlation of Particle Impact Conditions and Coating Properties in Cold Spraying
Authors: Schmidt T. , Gärtner F. , Kreye H. , Klassen T. 
Published: September 2022

Abstract
In cold spraying, the high strain rate plastic deformation during particle impact leads to a local temperature rise at the particle/substrate interface. This gives rise to thermal softening and thus further strain and heat generation, finally resulting in adiabatic shear instabilities, which are necessary to supply sufficient heat for successful bonding of the particles. These adiabatic shear instabilities can only occur, if a critical impact velocity is exceeded. A further increase of the impact velocity beyond this critical velocity continuously increases the fraction of well-bonded interfaces up to 95%, thus improving mechanical performance of the coatings. However, at far too high impact velocities, the efficiency again decreases and then changes to erosion due to hydrodynamic penetration. This erosion velocity is approximately two to three times higher than the critical velocity. The optimum velocity range between critical and erosion velocity is defined as “window of deposition”. Both critical and erosion velocity depend on the spray material properties, but also on particle impact temperature and particle size. Furthermore, they are also influenced by the powder purity. This study demonstrates the previously mentioned effects by calculations and experimental investigations. The presented link between fluid dynamics and impact dynamics enables to predict optimum spray parameters as well as the process effectiveness and resulting coating properties for certain cold spray conditions. Following this strategy, it was possible to increase the ultimate cohesive strength of cold-sprayed copper coatings from 80 MPa to more than 400 MPa, using nitrogen as process gas. In the annealed state, the ductility of these coatings corresponds to annealed bulk material. The overall optimization strategy is applicable to a wide variety of other spray materials. These developments should boost several new cold spray applications.
Influence of Particle Velocity on Adhesion of Cold-Sprayed Splats
Authors: Guetta S. , Berger M.H. , Borit F. , Guipont V. , Jeandin M. , Boustie M. , Ichikawa Y. , Ogawa K. 
Published: September 2022

Abstract
Cold gas dynamic spraying, namely cold spray, is an innovative coating process in which powder particles are injected in a supersonic gas flow to be accelerated above a certain critical velocity. Even though particles adhesion onto the substrate has not be yet elucidated, it appears clearly that it is influenced by particle impact velocity, which results from spraying conditions, diameter of particles and their positions from the center of the particle jet. Particle velocity can change dramatically depending on particle position from the core to the rim of the jet. In the present work, an original experimental set-up was designed to discriminate the particles as a function of the levels of velocity to investigate the influence of this parameter on adhesion. Particles at given positions in the jet could therefore be observed using SEM (Scanning Electron Microscopy), which showed different morphologies and microstructures as a function of impact velocity. High pressure and tangential velocity at the interface during impact were calculated from numerical simulations using ABAQUS. TEM (Transmission Electron Microscopy) analyses of thin foils were carried out to investigate into resulting local interface phenomena. These were correlated to particle impact velocity and corresponding adhesion strength which was obtained from LASAT testing (LAser Shock Adhesion Test).
Influence of Substrate Hardness on Deposition Behavior of Single Porous WC-12Co Particles in Cold Spraying
Authors: Gao P.-H. , Li Y.-G. , Li C.-J. , Yang G.-J. , Li C.-X. 
Published: September 2022

Abstract
Deposition of a dense coating with solid particles by cold spraying requires sufficient deformation of impacting particles and previously deposited underlying particles. The cermet particles and subsequent coating with a high hardness are difficult to deform upon impact. To increase the ability of deformation, the cermet spray particles with a porous structure design is proposed to fulfill the requirements of deformation on impact. To understand the deposition mechanism, the deposition behavior of single WC-Co spray particles impacting on the substrates with different hardnesses during cold spraying were examined using WC-12Co powders with different porosity. The substrates include stainless steel, nickel-based self-fluxing alloy coatings were employed to examine the effect of substrate deformation on the cermet particle deposition. It was found that using two porous powder of the porosity of 30% and 44% the WC-Co cermet particles were deposited on the substrate of different hardness from 200Hv to 800Hv. The deposition of the particles is mainly attributed to the deformation of powders themselves. The properly designed porous cermet powder with certain hardness is necessary condition to deposit hard WC-Co cermet coating.
Influence of Thermal Cycling on Internal Residual Stresses in a Thermal Barrier Coating with a Cold Sprayed Bond Coating
Authors: Niki T. , Ogawa K. , Shoji T. , Suzuki K. , Shobu T. 
Published: September 2022

Abstract
A kinetic metallization technique, which is one of the cold spraying systems, has been studied as a new coating system for metallic bond coats of thermal barrier coatings for components used in hot section of advanced gas turbines. In this study, in-situ residual stresses in atmospheric plasma sprayed yttria-stabilized zirconia (YSZ) top coating with two different bond coat spraying systems, deposited by a low pressure plasma spraying and a cold spraying, were evaluated and compared by thermal cycle tests. From the results of 1st thermal cycle, in the case of the plasma sprayed bond coat, a tensile residual stress was observed at the elevated temperature up to 400°C. Relaxation of the residual stress was started beyond 400°C. On the other hand, the gradual increase of tensile residual stress was observed up to 1000 °C in the case of cold sprayed bond coat. In addition, transition behaviors of residual stress between plasma sprayed and cold sprayed coatings were varied in 3-thermal cycles.
Characterization of Nanostructured and Conventional Alumina–13wt.% Titania Coatings
Authors: Ibrahim A. , Salem H. , Berndt C.C. 
Published: September 2022

Abstract
Nanostructured and conventional Alumina–13wt.% Titania powders were thermally sprayed using air plasma spray(APS) process. Scanning electron microscopy (SEM) was used to examine the morphology of the agglomerated powders and the cross section of the alumina-titania coatings. The microstructure and phase composition of the coatings were characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM).The fatigue and mechanical properties of the coatings were investigated. SEM analyses were also carried out on the fracture surfaces of fatigue-tested samples to assess the mechanisms of deformations. The experimental data indicated that the nanostructured coated samples exhibited higher stiffness, hardness, and fatigue strength compared to the conventional coated samples.
The Metallographic Characterization of Thermal Spray Coating Microstructures
Authors: Puerta D. , Anderson F. , Geary A. 
Published: September 2022

Abstract
Thermal spray coatings from several different coating families have been metallographically prepared using traditional and modern metallographic techniques. The different recipes used were intended to demonstrate the effect of abrasive on coating appearance. Traditional metallographic recipes, which rely heavily on the use of silicon carbide (SiC) abrasive papers, were found to produce a notably different appearance than those prepared using modern recipes. Modern recipes, which incorporate extended diamond grinding and polishing steps, were found to produce what appears to be a more representative coating structure. Other variables, including mounting media and use of vacuum impregnation, were also found to influence coating appearance.