bluuebunny/crossref_metadata_2025 huggingface dataset:
HVOF-Sprayed TiC-Strengthened Fe-Coatings as Alternative to Conventional Carbide Materials
Authors: Bobzin K. , Ernst F. , Richardt K. , Warda T. , Reisel G.
Published: September 2022

HVOF-sprayed carbide based coatings such as WC/Co or Cr3C2/NiCr are industrially well established for wear and corrosion protection applications. Due to their high carbide content of typically 75 wt.-% and more, they are providing a very high hardness and excellent wear resistance. Unfortunately costs for matrix materials like Ni or Co underlie strong fluctuations and are significant higher compared to iron. Therefore an alternative concept to the conventional carbides is based on TiC-strengthened low cost Fe-base materials, which are already in use for sintering processes. Depending on the carbon content the Fe-base material can additionally offer a temperable matrix for enhanced wear behaviour. Within this study the sprayability of TiC-strengthened Fe-powders with a gaseous and a liquid fuel driven HVOF-system has been investigated. The resulting coatings have been analysed with respect to microstructure, hardness and phase composition and compared to galvanic hard chrome, HVOF-sprayed and remelted NiCrBSi and HVOF-sprayed Cr3C2/NiCr (80/20) coatings as well as sintered Fe/TiC reference materials. Furthermore the Fe/TiC coatings have been heat treated to proof the retained temperability of the Fe-matrix after thermal spray processing. For determination of wear properties tribometer tests have been conducted. Currently the corrosion resistance of the sprayed Fe/TiC coatings is investigated as well the wear behaviour in a practical hydraulic test bench.
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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.
Residual Interfacial Strength in an Air Plasma Sprayed Thermal Barrier Coating After Thermal Cycle Fatigue
Authors: Yamazaki Y. , Yoshida T.
Published: September 2022

Air plasma sprayed thermal barrier coatings, which reduce the temperature in the underlying substrate material, are an essential requirement for the hot section components of an industrial gas turbine. For TBC systems, the adherence of the top coating is one of the most important parameter for the durability of TBC system. In this work, the thermal fatigue behaviour of an air plasma sprayed thermal barrier coating was investigated. In addition, the residual interfacial strength was also evaluated by means of the 4-point bending test. From the measurement of the AE signals during the thermal fatigue tests, micro-cracking occurred in each cooling stage of the thermal fatigue cycles and then such damage depends on the number of thermal cycle. In addition, TGO grew at the interface with the exposed time at elevated temperature (the time dependent damage). Thermal barrier coating undergoes both time dependent damage and cycle dependent one under thermal fatigue condition. The life of thermal cycle with high temperature dwell time is shorter than not only that of isothermal exposure but also that of thermal cycle without dwell time.
Effect of Spray Torch Nozzle Design Modifications on Arc and Plasma Jet Characteristics and Coating Properties
Authors: Outcalt D. , Suzuki S. , Vincenzi L. , Heberlein J.
Published: September 2022

In order to identify means to improve plasma spray consistency, various modifications to the design of a commercial plasma torch nozzle have been investigated. The modifications consist of preparing anode inserts with grooves in the axial direction (spline insert), and introducing a fraction of the plasma gas through a ring of micro-nozzles surrounding the anode nozzle (micro-jet ring). Different designs for each modification have been investigated, and these modifications have also been paired with a modified upstream gas injector. For each of the modified designs, a wide range of characteristics have been measured for the arc, the plasma jet, the in-flight particles and the coating. The results show that most nozzle modifications lead to higher particle velocities and temperatures. The plasma jet is significantly elongated by using some of the modified nozzles, and the cold gas entrainment somewhat reduced. The arc voltage and the luminosity fluctuations are little affected by the nozzle modifications, however, the modification of the gas injector does change the frequencies of the fluctuations. Each of the nozzle modifications can be easily implemented offering an economical way to enhance process reliability.
Influence of Parameters on Volt-Ampere Characteristic of Plasma Arc in High Velocity Plasma Spraying
Authors: Yang H. , Wang L.
Published: September 2022

The plasma torch is one of the most important equipment during air plasma spraying, is used to produce the plasma arc in the nozzle for the acceleration and heating of particles. The voltage-current characteristic of the plasma arc is very important to the fusion of particles. The volt-ampere characteristic is affected by many factors, such as gas species, gas flow rate, nozzle geometry and the type of gas injection. So the factors influencing the voltage-current characteristics in high velocity plasma spraying were studied. As the results showed, the arc voltage is increased with the increase of the primary gas flow rate in some range. The secondary gas flow rate has an important effect on the electric arc voltage. The influence of nitrogen on the arc voltage is more than argon when they are chose as the primary gas in plasma spraying. The arc voltage is decreased with the increase of the nozzle’s compression angle and the decrease of the nozzle’s aperture, when the length of the nozzle is unvarying.
Characterization of Cold-Sprayed Nickel, Titanium, and Copper Coatings for Process and Property Optimization
Authors: Rezaeian A. , Chromik R.R. , Yue S. , Irissou E. , Legoux J.-G.
Published: September 2022

The properties of pure Cu, Ni and Ti cold spray coatings on mild steel substrates were examined. Samples were prepared using CGTTM Kinetics 3000 system varying gun temperatures from 200 to 600 °C and gun pressures from 10 to 30 bars with N2 as propelling gas. For these conditions, deposition efficiencies and critical velocities were characterized. In addition, the microstructural and mechanical properties of coatings were examined.
Manufacturing of Diamond Abrasive Wheel from Ni Coated Diamond/Bronze Composite Feedstock Through Kinetic Spray Technology
Authors: Na H. , Bae G. , Kumar S. , Lee C. , Kim H.J.
Published: September 2022

Manufacturing of diamond abrasive wheel has been achieved through kinetic spraying in order to simplify the manufacturing process and improve the mechanical properties. However, size of the initial feedstock diamond particles is reduced by fracturing during the process. Uniform distribution of diamond particles in the coating layer is significantly important for obtaining grinding properties of diamond abrasive wheel. In this study, optimized nickel thin film which is coated around the surface of diamond particle was used to prevent the fracture of diamond particles during spraying and improve the properties. Thickness of the nickel thin film was optimized by ABAQUS 6.7-2 finite element analysis software as 3 µm for 20 µm diamond and bronze particles. Fraction and size distribution of the diamond particles present in the coating were analyzed through Scanning Electron Microscope (SEM) and Image analyzer methods.
Comparison of a High-Purity HOSP PYSZ Powder with Standard HOSP—Powder-Coating Characterization and Thermal Cycling Testing
Authors: Gray S. , Lawson K.J. , Dorfman M.R.
Published: September 2022

A high-purity (HP) HOSP (Hollow Oven Spherical Process) PYSZ powder has been evaluated and compared to standard PYSZ powders. The main difference is these two powders is the starting raw material purity. Four TBC systems (2 standard types and 2 high purity versions) were Air Plasma Sprayed (APS) onto CMSX-4 substrates with APS CoNiCrAlY bond coats. Thermal shock testing was performed to 50 % spallation at 1135°C with 1 hour hot cycles with forced air cooling. The as-deposited coatings and those after thermal shock failure were characterized using X-ray diffraction, Raman spectroscopy and scanning electron microscopy. The thermal cycling results show little difference in the thermal shock resistance of the coatings with all failing in an adhesive manner with failures occurring in excess of 180 hot cycles. XRD and Raman data is used to identify the levels of monoclinic and tetragonal phases present in each coating and SEM analysis used to identify differences between PYSZ with a broad particle size distribution and a tighter controlled PYSZ particle size distribution.
Low Pressure Gas Dynamic Spray of Hydroxyapatite Composite Coatings
Authors: Leshchynsky V. , Weinert H. , Maeva E. , Maev R.
Published: September 2022

Hydroxyapatite Composite (HAC) Coatings made by Low Pressure Gas Dynamic Spray (LPGDS) on the grit blasted Ti alloy substrate were studied. The powder feedstock for the HAC coating by LPGDS was prepared by mixing HA powder with Phosphate Glass particles in polyvinyl alcohol, drying and stirring. As-sprayed HAC films on the substrate were heat-treated by two steps (400-500°C and 600-900°C) and their physical characteristics were investigated by scanning electronic microscopy (SEM), X-ray diffractometer (XRD). During sintering-heat treatment, HA particles were consolidated and melted to form a dense and homogeneous coating layer which exhibits the grain structure. Application of HA-glass feedstock is found to be effective for Cold Spray HA based coatings.
Synthesis and Suspension Plasma Spraying of Hydroxyapatite Fine Powder
Authors: Jaworski R. , Pierlot C. , Pawlowski L. , Bigan M. , Quivrin M.
Published: September 2022

The synthetic hydroxyapatite (HA, Ca10(PO4)6(OH)2) is a very useful biomaterial for numerous applications in medicine, especially in view of using as fine powder for suspension plasma spraying. The powder was synthesized using aqueous solution of ammonium phosphate (H2(PO4)NH4) and calcium nitrate (Ca(NO3).4H2O) in carefully controlled experiments. The synthesized fine powder was characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The powder was formulated into water and alcohol based suspension and used to carry out the initial tests of plasma spraying onto titanium substrate. The phase analysis of sprayed coating was made with the used of XRD.
Thermal Spraying as a Manufacturing Technology for Light Metal MMC; Experimental and Numerical Process Analysis
Authors: Silber M. , Dongmo E. , Gadow R. , Wenzelburger M.
Published: September 2022

For the manufacturing of metal matrix composites, a combined process of thermal spraying followed by forging in the semi-solid state can be applied. In previous work, it has been shown that thermal spraying leads to a globular microstructure that is suitable for semi-solid forming. Thereby, penetration of the spray material into the reinforcement phase leads to reduced matrix flow paths and thus reduced forming time and fiber disarrangement during the forming process. The main requirement is a low substrate and coating temperature during matrix deposition. By control of the process temperature, geometrical accuracy of the prepreg material and it’s handling between each process step can be significantly improved, leading to an economical method that is a superior alternative to the well established MMC processes like diffusion bonding or squeeze casting. Moreover, due to low process temperatures and process time during matrix application, chemical attack of carbon fiber reinforcements can be reduced. Process development for the manufacturing of continuous fiber reinforced prepregs was focused on the analysis and control of particle properties and substrate temperature. In order to improve the temperature control during arc wire spraying, numerical process analysis of the cooling system was applied. Particle in-flight analysis with the SprayWatch system was used to obtain direct spray parameters as input data for the numerical models. The simulation results were verified by experimental infrared thermography of the substrate during coating. By the use of an optimized cooling system, dense coatings without cracks were achieved with different coating thickness, thereby tailoring the fiber volume content of the final MMC component.
New Health and Environment-Friendly Iron Based Materials Employed as Binders for Carbide Powders used in Thermal Spraying
Authors: Zimmermann S. , Gries B. , Fischer J.
Published: September 2022

Cobalt containing carbide powders such as WC-Co and WC-Co-Cr for thermal spraying exist in numerous modifications varying in chemistry, carbide size, and production method. They are widely used for wear, erosion and corrosion protection in many industrial fields. However, for decades it has been well-known from the hard metal industry that WC and Co containing hard metals in breathable dust form can provoke severe lung diseases if inhaled. Recent examinations have proven that this toxicity can be significantly reduced if the Co is pre-alloyed by Fe. In thermal spraying employees are also dealing with Co containing carbides, for example in powder and coating production. Therefore, in order to reduce the hazards for health and the environment, a new class of agglomerated and sintered carbide powders using Fe based binder materials have been developed and investigated. In the present study the powders were HVOF sprayed in order to examine the influence of their different composition and morphology on the microstructure and the properties of the coatings in comparison to standard materials. The experiments comprise microstructural examinations, wear and corrosion tests.
Metallization of Plastics by Detonation Spraying
Authors: Ulianitsky V. , Shtertser A. , Zlobin S. , Smurov I.
Published: September 2022

Metallization of plastics by thermal spraying is studied. The possibility to obtain high adhesion of metal particles to the surface of a wide range of plastic materials is shown. Powders are sprayed with a new generation detonation gun “Dragon” designed at Lavrentyev Institute of Hydrodynamics SB RAS. The apparatus is characterized by a high-precision gas supply system and a dosed localized powder feeding system. Computer control provides a flexible programmed readjustment of the detonation gases energy impact on powder particles which is a key factor in precision control of spraying parameters for low-melting point powder materials. It is found that under certain spraying conditions molten particles of a low-melting point material not only do not provoke erosion of plastic material at their high velocity impact on the substrate but strong-bond fusion, sufficient to further form a thick coating, occurs. Aluminium, zinc and tin powders are sprayed on substrates from fibreglass, polyester, fluoroplastic and some other plastics. Load capacity of the obtained coatings reaches 100 kg/cm2. It is shown that on top of a thin layer from a low-melting point powder material high-melting point metals and even ceramics can be deposited.
Residual Stresses in HVOF- and APS-Deposited AI2O3 and Cr2O3 Coatings
Authors: Bolelli G. , Lusvarghi L. , Varis T. , Turunen E. , Leoni M. , Scardi P. , Azanza-Ricardo C.L. , Barletta M.
Published: September 2022

Residual stresses in plasma-sprayed Al2O3 and Cr2O3 coatings, deposited using commercial powders, and in HVOF-sprayed ceramic coatings, deposited using conventional Al2O3 and Cr2O3 feedstock and nanostructured- Al2O3 feedstock, were studied by combining X-ray diffraction, substrate chemical removal technique and analytical modelling. The in-situ curvature technique was also employed for HVOF-sprayed Al2O3 coatings, for further verification. Both HVOF-sprayed Al2O3-based coatings display similar, tensile residual stresses (≈120 MPa) near the top surface and possess moderate through-thickness stress gradients (≈10 - 20 MPa). Plasma-sprayed Al2O3 possesses a smaller through-thickness stress gradient and a larger near-surface stress (≈220 MPa): this latter result seems to be due to higher quenching stresses in APS Al2O3, as determined by analytical computation The analytical model is validated by its fairly good agreement to the experimental results obtained both by substrate chemical removal and by in-situ curvature. Cr2O3-based coatings possess a lower near-surface residual stress (≈20 MPa); the HVOF one also exhibits a very large stress gradient (≈80 MPa). Machining and sliding processes (like polishing and dry sliding tribological testing) change their surface residual stresses to compressive ones.
Three-Dimensional Simulation of Porosity in Plasma-Sprayed Alumina using Microtomography and Electrochemical Impedance Spectrometry for Finite Element Modeling of Properties
Authors: Amsellem O. , Madi K. , Borit F. , Jeulin D. , Guipont V. , Jeandin M. , Boller E. , Pauchet F.
Published: September 2022

Moving from a 2-dimensional to a 3-dimensional approach to microstructure and properties has been expected eagerly for a long while to result in a dramatic increase in the knowledge of thermally-sprayed processes and coatings. To meet these expectations, in the present work, microtomography and electrochemical impedance spectroscopy (EIS) were carried out to simulate the microstructure of plasma-sprayed alumina. As-sprayed and excimer laser-processed deposits were studied. Some unexpected but relevant results, e.g. regarding pore orientation in the coatings, could be obtained. EIS simulation led to the establishing of an electrical circuit equivalent to the microstructure which simulated the insulating properties as a function of interfaces and pore interconnection. The latter was studied by microtomography. From this 3-dimensional simulation, a finite element analysis of mechanical properties was developed and compared to experimental measurements. Using this approach to microstructure and properties, excimer laser surface processing was shown to be an innovative process to modify insulating characteristics of plasma-sprayed alumina.
Mullite-Zircon Thermal Barrier Coating Production by Plasma Spraying Process
Authors: Toplan N. , Ustel F. , Toplan H.O. , Erdogan G.
Published: September 2022

Zircon (ZrSiO4) is a technologically important oxide ceramic material known for its high refractoriness and chemical stability. It shows excellent thermal shock resistance as a result of its very low thermal expansion coefficient and a low heat conductivity coefficient. Plasma spraying is a convenient method to produce large area coatings with high growth rates, necessary for many applications. ZrSiO4 is among the least expensive spraying materials for refractory applications. In this study, a single-step process was used to prepare mullite/zirconia ceramic composites by plasma spraying zircon/alumina mixtures. Mixtures of ZrSiO4 and Al2O3 powders with Al2O3 to SiO2 molar ratios of 3:2 were milled for 2 h in a zirconia medium using a ball mill. The as–milled powders were dried in the furnace and sintered at 1300 and 1350 °C for 2h then crushed to a size less than 100 μm. The powders were sprayed by an atmospheric plasma spray gun (Metco 3MB) using C/C+SiC ceramic matrix composite substrates. Scanning electron microscopy (SEM) was used to analyze the microstructures of the powders and plasma coatings. The phase composition analysis of the powder showed the presence of alumina and zircon. After plasma coating, alumina, zircon, and zirconia phases were determined.
Thermal Behaviour of Thermally Sprayed CaZrO3 Coatings
Authors: Garcia E. , Cano C. , Osendi M.I. , Miranzo P. , Coyle T.W.
Published: September 2022

CaZrO3 coatings were alternatively prepared by air plasma spray and flame spray processes. The microstructural characteristics and crystalline phases of the coatings were comparatively studied as a function of the spraying temperature achieved with each technique and the stand off distance. Image analyses were used to estimate their porosity. Thermal diffusivity was measured on free-standing thick coatings using the laser flash technique. Thermal conductivity was obtained from the experimental thermal diffusivity and density data. The hardness of the coatings was evaluated by Vickers indentation tests. Finally, different thermal treatments were carried out to evaluate the evolution of the crystalline phases and the properties of the coatings.
Bioactivity of Micro-Plasma Sprayed Yttria Stabilized Zirconia Coating
Authors: Wu Y. , Li Z. , He D. , Zhao Q. , Li H. , Li H.
Published: September 2022

Yttria-stabilized zirconia coatings were deposited onto a Ti-6Al-4V substrate through a microplasma spray technique and incubated in simulated body fluid (SBF) for different periods of time (3, 7, 14, 28 days). The formation of apatite on the surface was investigated to evaluate the bioactivity of the coatings. Surface morphologies and structural changes in the coatings before and after immersion were analyzed by optical microscopy, scanning electron microscopy, and x-ray diffractometry. The calcium (Ca2+) concentration in the solutions was measured directly after the samples were removed, using an inductively coupled plasma atomic emission spectrometer (ICP). The results showed that yttria-stabilized zirconia coatings can be produced by microplasma spraying and, even though the coatings contain few small unmelted particles, apatite can be formed on the coatings that are soaked in SBF solution. These results indicate that the yttria-stabilized zirconia coatings exhibited definite bioactivity.
Over Ten Years of Quality Assurance, Education and Training in Thermal Spraying
Authors: Huber R. , Ohliger-Volmer A.
Published: September 2022

Since 1993 education and training guidelines and as well as qualification standards of thermal spray personnel have been created step by step by the European Committees of EWF (European Federation of Welding, Joining and Cutting) and CEN (European Committee or Standardisation). ISO personnel qualification and quality management standards result together with the EWF education and training guidelines in a sound QM-system, which meets the increased demands of trade and industry of high quality sprayed coating. Meanwhile about 13 ETS courses were held at the German Welding Institute. Also ETS courses have been held in Finland. The EWF education and training course of the ETSS European Thermal Spraying Specialist will be offered by the German Welding Institute in Munich - SLV München - for the eleventh time in October 2008. DIN EN ISO 9000 series are commonly valid, that is why the product related quality management EN ISO 14922 ”Quality Requirements of Thermally Sprayed Structures, part 1 - 4” was created. This standard series puts principles for the fitness of the purchaser and of his spray production. The QM-system that was established by the GTS e.V.– the Association of Thermal Sprayers – was pioneer and does an excellent job concerning its requirements. The QM-standards are also involve the important ISO standards of the Thermal Spraying Co-ordinator and the Approval Testing of Thermal Sprayers.
Slight Change in Direction
Authors: Grimenstein L.
Published: September 2022

Each year a large number of papers are given at the International Conference. During your time at the conference, you will have the opportunity to hear of the latest developments in technology. Some of the presentations will be done by some of the best in the Thermal Spray Industry doing research and others from equipment and material suppliers. There are others, done by suppliers, who actually are doing the thermal spray applications on a large variety of parts. However even though the R & D papers have a lot of good scientific information a large amount of it is non usable in the industry. So, who should be changing directions?