bluuebunny/crossref_metadata_2025 huggingface dataset:
In Flight Particles Analysis for the Characterization of the Arc Spray Process
Authors: Planche M.P. , Liao H. , Coddet C.
Published: August 2022

The aim of this study was to point out the role of each electrode in the droplets formation in twin arc spraying. This way, two consumable wires of different properties, namely steel and copper, were sprayed simultaneously. The DPV 2000 diagnostic system was used to determine the size, temperature and velocity of in-flight particles, detected at the same locations than those previously tested on particles collection. Then, a model based on the particle temperature was developed to separate particles from the anode and the cathode wires. Results showed significant modifications in term of size, velocity, temperature and repartition when changing material electrodes. To validate the proposed model, modelling results were first compared to results found on properties of collected particles, i.e. sizes and percentages. Then, important differences of in-flight particles characteristics, velocity and temperature, were pointed out depending on the electrode nature and on radial locations in the spray jet. Finally, some coatings were sprayed at the same locations and analyzed in term of thickness. Results showed that the thickness distribution was largely dependent on the anode nature, which was in close agreements with in-flight particles analysis.
Correlation of Inflight Particle Parameters and Properties of HVOF Sprayed Cermet Coatings
Authors: Wielage B. , Wank A. , Rupprecht C. , Wank A.C.
Published: August 2022

HVOF sprayed cermet coatings are used for wear protection in numerous application fields. Most feedstock powders can be processed successfully with different spraying guns but optimized parameters for high quality coating production cannot be transferred directly. Besides substrate temperature only particle velocity and temperature inflight and at impact on the substrate determine the resultant coating properties. Two typical HVOF powders, WC/Co 88/12 and Cr3C2/Ni20Cr 75/25, are sprayed using the kerosene fuel system GTV K2 and particle parameters are recorded just prior to impact on the substrate with the passive diagnostic tool Spray Watch. Detailed correlation of particle parameters and the coating properties porosity and micro hardness as well as deposition efficiency is worked out in order to deduce particle parameter ranges providing coatings with defined optimum properties. The transferability to another kerosene fuel HVOF spraying gun, Tafa JP5000, is tested. It is also shown that effects like wear of the nozzle can be detected by use of the Spray Watch. Secondary correlation of particle parameters and machine settings is carried out to build a base for straight forward closed-loop control of the HVOF spraying process applying process diagnostics
Dense Titanium Coatings by Modified HVOF Spraying
Authors: Kawakita J. , Fukushima T. , Kuroda S. , Katanoda H. , Matsuo K. , Fukanuma H.
Published: August 2022

Titanium has an excellent corrosion property in chloride containing environments such as seawater. A modified HVOF spray process was developed by introducing a mixing chamber between the combustion chamber and the powder feed port. Nitrogen gas was fed into the mixing chamber to control the temperature of the combustion gas generated in the combustion chamber. By controlling the flow rate of nitrogen, various Ti coatings with different degree of oxidation and porosity could be fabricated. The densest coating produced by this process with surface polishing treatment maintained excellent corrosion protection over a steel substrate in artificial seawater in a laboratory test over 1 month.
Effect of Angle of Impingement on Erosion-Corrosion Behaviour of a WC-Co-Cr HVOF Sprayed Coating
Authors: Hodgkiess T. , Perry J.M. , Neville A.
Published: August 2022

This paper describes an investigation of the influence of impingement angle of a solid/liquid jet upon the erosion corrosion behaviour of a tungsten carbide-cobalt-chromium thermal sprayed coating. The coating type investigated was a nominal WC-10%Co-4%Cr material, HVOF-sprayed onto a stainless steel substrate. This coating was subjected to a submerged impinging jet at 12 m/s of 3.5% NaCl solution containing various concentrations of suspended sand particles at 18°C. The angles of impingement employed were 30, 45, 60, 75 and 90 degrees and the measured total weight losses exhibited a significant influence of impingement angle with reduced material losses at more oblique angles of jet impact. The implementation of cathodic protection to the specimens enabled the pure mechanical component of the overall erosion-corrosion damage to be determined and this was also found to be dependent upon the angle of impingement of the liquid/solid stream. In contrast, the pure corrosion component (determined from in-situ electrochemical monitoring) exhibited no systematic trends with impingement angle. The findings are discussed in terms of the detailed erosion-corrosion mechanisms and implications for operational durability of cermet coatings
Effects of Substrate Surface Condition on the Flattening Behavior of Impinging Splat
Authors: Li H. , Liao H-L. , Costil S. , Coddet C.
Published: August 2022

Thermal spray coatings are formed by successive molten droplets impinging onto a substrate. It is commonly admitted that the flattening behavior determines the interaction of splats with the substrate or previously deposited under layer and hence governs the overall quality of the sprayed deposit. Therefore a number of works have been devoted to explain the splashing mechanisms and the flattening behavior from different aspects, such as fluid dynamics, solidification behavior, surface wettability or surface adsorbates/condensates. It was thus shown that surface conditions such as surface roughness, contaminants, adsorption, etc. play a very important role in controlling the splat flattening behavior. In this study, the role of the substrate condition as well as that of the impinging particle parameters are emphasized in the case of a copper deposit formed on a titanium base alloy and on a stainless steel substrates. The plasma sprayed copper splats were examined for different surface conditions. It was thus confirmed that favorable surface conditions tend to suppress splashing and to promote the occurrence of disc-shaped splats while the substrate nature and particle parameters also affect the splat flattening behavior. Results also indicated that disc-shaped copper splats prepared on a cold substrate have a smaller flattening degree than those obtained on a preheated substrate.
Microwear in Thermally Sprayed Hard Coatings by Different Abrasives
Authors: Eronen V. , Ahmaniemi S. , Niemi K. , Vuoristo P.
Published: August 2022

Microscale wear mechanisms in thermally sprayed hard coatings were examined. A test procedure for examining microwear with various abrasives was developed. Different abrasivity of kaolin, precipitated calcium carbonate and titania was found to affect wear mechanisms. Fine-particle abrasion caused the surface to loose its gloss and smoothness. Coatings subjected to fine-particle abrasion were examined with optical gloss measurements and scanning electron microscopy. It was shown that in tungsten carbide based hard coatings the microscale wear was governed by preferential wear of the soft binder phase. However, also coating defects like pores or poorly adhered splats tended to provide nucleation points for microscale wear. It was found that coatings that performed well in dry-sand rubber wheel abrasion or wet abrasion tests did not necessarily have good microwear resistance. The results showed that different abrasives had effect on the wear phenomena and wear rate of hard coatings. Coatings also behaved differently and novel modifications in the composition affected the wear behaviour. In conclusion, the results provided deep understanding of the role of various abrasives in the wear phenomena of thermally sprayed hard coatings.
Correlation of Microstructure with Abrasion and Oscillating Wear Resistance of Thermal Spray Coatings
Authors: Wielage B. , Wank A. , Pokhmurska H. , Friesen E. , Grund T. , Schwenk A.
Published: August 2022

Detailed studies concerning influence of microstructural features on the resistance of different thermal spray coatings against dry abrasive wear (Taber Abraser test) and oscillating wear (ball on disk configuration) are carried out. Besides WC and Cr3C2 based cermet coatings produced by a triple cathode APS system with axial powder feed and by HVOF systems using kerosene fuel also APS Cr2O3 and Al2O3 coatings are tested. At the example of WC/CoCr coatings the influence of carbide size and content, powder size fraction, powder manufacturing process and spraying process parameters is studied. For APS Al2O3 investigations concerning the influence of powder feed rate and nozzle geometry of single cathode APS torch are imparted. Oscillating wear tests are performed using alumina and hardened steel balls as counter bodies. Coatings are characterized concerning phase composition and residual stress state by means of XRD. Additionally microstructure is evaluated by SEM investigations and micro hardness is measured. Guidelines for manufacturing of thermal spray coatings fitting the specific demands of the two applied wear conditions are deduced.
HVOF Coatings Properties of the Newly Thermal Spray Composition WC-WB-Co
Authors: Bouaricha S. , Legoux J.-G. , Marple B.R.
Published: August 2022

A new WC-WB-Co feedstock material was sprayed with two HVOF torches. During spraying, the in-flight temperature and velocity history were monitored using the DPV2000 tool. Coatings sprayed with both guns had a relatively high microhardness and good abrasion properties, even with a higher level of porosity for some coatings. This was explained by the nature of the matrix which was composed of an amorphous/nanocrystalline structure and W-Co-B phases. It is suggested that the matrix is harder than conventional binders such as cobalt, for instance, and exhibits a better cohesion with the WC hard phase.
Controlled Removal of HVOF Hard Coatings by Abrasive Water Jet
Authors: Ruusuvuori K. , Lahdenperä K. , Oksa M. , Turunen E. , Lundberg R.
Published: August 2022

This paper presents development of adaptive Abrasive Water Jet (AWJ) removal method for HVOF hard coatings. High pressure water jet using Al2O3 powder was used to remove WC-CoCr and Cr3C2-NiCr HVOF coatings in a controlled manner. As a result, coating thickness was reduced down to 10-20 µm without damaging the base material. With this novel method use of environmentally problematic chemicals can be avoided or reduced in coating stripping process. To control the coating removal process and to prevent unwanted base material erosion through jetting, a system capable of measuring the coating thickness non-destructively with adequate accuracy was integrated to the AWJ removal cell. Depending on the substrate and coating materials used, the applied measurement technique is based on the eddy current or X-ray fluorescence methods.
Improvement of Mechanical Properties of Alumina and Zirconia Plasma Sprayed Coatings Induced by Laser After-Treatment
Authors: Ctibor P. , Nohava J. , Karovicova I. , Chraska P. , Tuominen J. , Vuoristo P.
Published: August 2022

Alumina and stabilized Zirconia were plasma sprayed in air using the water-stabilized plasma torch. In the case of Alumina two different stand-off distances were applied at spraying. Nd-YAG laser was then used for additional treatment of plasma sprayed coatings. The laser was maintained in a quasi-continual regime and defocused from the surface to increase the treated coating's area. Energy density was varied together with the laser scanning velocity to ensure variance in thermal history of the treated surfaces. Microhardness, surface roughness and slurry abrasion resistance (SAR) were measured before and after the laser treatment. Results vary in dependence on the laser treatment's parameters. When the treatment results in substantial changes of the structure (up to a complete re-melting of the surface), enhancement of all measured properties was proven. It is demonstrated that the extent of change of mechanical properties can be correlated with optical properties of coating materials at the laser wavelength. Microstructural aspects of the laser treatment are discussed as well, especially at the boundary between the laser-annealed layer and the basic coating's microstructure. It is pointed out that laser overheating due to use of an extremely high energy density can cause delaminating of the coatings.
Influence of Reduction Process on the Microstructure and Composition of Plasma Sprayed Al2O3-3TiO2/CuO Composite Coating
Authors: Zórawski W. , Chatys R. , Jamrozek J.
Published: August 2022

Undesirable changes in the coating composition can be reduced if plasma spraying is performed in a special chamber with a regulated atmosphere, the process being extremely costly, though. Another method allowing changes in the structure of coatings is thermal treatment. Numerous works present and discuss the results of the research into the influence of carburizing, nitriding, and laser or electron beam treatment on the properties of plasma sprayed coatings. This work concerned composite coatings obtained by plasma spraying of the blend of Al2O3-3TiO2 and CuO powders, which were then reduced at an atmosphere of dissociated ammonia. Their chemical composition and morphology were determined by means of the EDS microprobe and the Joel 5400 scanning microscope respectively. It has been reported that the process of reduction contributes to the homogeneity of the coating, and that the modified structure contains Al2O3 and Cu. Abstract only; no full-text paper available.
The Laser Shock Adhesion Test (LASAT) for Production Control of Thermally-Sprayed Ceramic Coatings
Authors: Boileau S. , Guipont V. , Jeandin M. , Nivard M. , Berthe L. , Jerôme J. , Boustie M. , Li H. , Khor K.A.
Published: August 2022

The adhesion strength of a ceramic coating deposited through direct spraying on a roughened substrate is a key issue in the manufacture of high-quality coatings on industrial components. The purpose of this work was to develop a rapid and discerning procedure for establishing adhesion level of a ceramic coating on a metallic substrate. The Laser Shock Adhesion Test, namely LASAT, was successfully applied to ceramic coatings with irradiation impact on the metallic side. Suitable parameters were found to determine the LASAT adhesion threshold using a standard Nd:YAG laser source. With a laser-irradiated area of several millimetres in diameter, it allowed assessment of the coating threshold on several areas of a coated plate sample. A control procedure for a qualitative assessment of coating adhesion was developed. This testing procedure could be easily used in industry, with possible location of the LASAT unit near to the spraying booth, for a direct production control on coated sample to improve the tracability of manufactured parts. Additional work was carried out to investigate a quantitative approach of the LASAT test to ceramic coating. The purpose was to simulate the shock wave propagation with the RADIOSS® code (a 3D software originally developed for car crash simulation). This code was implemented to calculate the velocity of the material and corresponding pressure throughout the substrate and the coating during the shock wave release (less than 2 ms). Experimental VISAR profiles ('Velocity Interferometer System for Any Reflector') were monitored in the straight direction of the laser-irradiated area on the rear side. These experimental signals (velocity measures) of the ceramic coating could be fitted and compared with a fairly good agreement with simulated profiles obtained by RADIOSS®. This modelling work was the first step towards a more comprehensive coating adhesion strength calculation in the future.
Comparative Study of Wear and Corrosion Properties of Electric Arc Thermally Sprayed Coatings
Authors: Lima C.R.C. , Barrera R. , Camargo F.
Published: August 2022

The use of thermally sprayed coatings to improve wear and corrosion resistance of industrial components has been found to be an effective and viable choice. Coatings based on several materials can be used for such applications, including situations when they are combined, using distinct deposition methods. The analysis for choice of the ideal coating and application process should generally take into account both coating performance and cost. In this work a comparative study of three commercial coating materials is performed. The used coating materials are High Chromium (HCr), High Chromium + 420 Stainless Steel and 420 Stainless Steel + 1080 Carbon Steel wires applied by Electric Wire Arc Spaying. The obtained coatings are tested for wear (ASTM-G-65-91 rubber wheel test) and corrosion (ANSI/ASTM-B117 and Electrochemical Measurements). Coatings microstructure, microhardness and adhesion (ASTM-C633-85) are also evaluated.
Microstructure Characterization of WC-25%NiCr Cermet Coating by Plasma Laser Hybrid Spraying Technique
Authors: Kim H.-G. , Katayama S. , Ohmori A.
Published: August 2022

Thermal sprayed WC-metal binder cermet coating is widely used for their resistance to abrasive wear in various harsh environments and generally sprayed by high velocity oxy-fuel (HVOF) method and atmospheric plasma spray method (APS). However, even during HVOF spraying, WC-metal binder cermet powder has to be exposed to high temperature flame jet for heating and accelerating, furthermore, oxygen is usually entrained into the flame jet, the decomposition and decarburization of tungsten carbide owing to the oxidation of WC, cannot be totally eliminated. This frequently causes defects such as pores, cracks and unmelted particles, which deteriorate coatings properties. To improve the properties of sprayed coatings, numerous studies have been examined post treatments such as laser irradiation, diffusion treatment, hot isostatic pressing (HIP) treatment, sealing treatment. Laser irradiation was speedy treatment and simplicity of process control and enables not only the post treatment but also the pre and simultaneous treatment by combining with spraying process. However, it is not easy to produce a uniformly treated coating by conventional laser treatment method as desired. To obtain a near-uniform beam intensity for practical laser irradiation, a kaleidoscope was installed in a conventional YAG laser. In this work, laser beam properties of YAG laser equipped with a kaleidoscope and its effect on surface modification of WC-25%NiCr coating was investigated. Abstract only; no full-text paper available.
Hot Gas Atomized Melts - Potentials for Thermal Spray Powders
Authors: Wolf G. , Bendix D. , Faulstich M.
Published: August 2022

The atomization of molten materials using hot gases has advantages in comparison to the conventional gas atomization techniques. Some of these advantages favour the hot gas technology for the powder production for thermal spraying. Firstly, a considerably higher output of fine powder, in particular within the important particle size range between 5 and 30 µm, is a result of hot (inert) gas atomization. The reasons are the strongly increased gas exit velocity and the higher overall temperatures inside the interaction zone of the gas and the melt droplets. The enhanced shear forces acting on the molten liquid and the prolonged liquid state of the atomized particles lead to a more efficient atomization. Secondly, the extended time regime for liquid droplets facilitates the atomization of highly viscous melts, such as oxide melts, and results in more spherical particle shapes with good flowability. Thirdly, oxide or nitride powders can be generated directly from the molten metal by the usage of hot reactive gases or gas components for atomization. This paper describes the special features of a 25 bar hot gas atomization technique with pre-heated gases up to 1200°C and discusses its potentials for the generation of powders in view of their suitability in thermal spray applications.
Hydroxyapatite Coating of Biomimetic Polymer Composite Materials
Authors: Legoux J.-G. , Bureau M. , Priscillia G.
Published: August 2022

One of the largest successes of modern medicine is the total hip replacement. Presently this procedure has one of the highest success rate among surgical interventions, only second to the appendix removal procedure. However the lifetime of the prosthesis itself is still limited to 10 to 20 years, which means that for numerous patients replacement of the procedure will become mandatory. This replacement finds its origin in aseptic loosening of the prosthesis mainly caused by the formation of wear particles at articular joints and by the difference in stiffness between the bone and the metallic prosthesis leading phenomena called stress shielding. To overcome this problem, new designs of more biomimetic prostheses, with stiffness similar to that of cortical bone, are being studied. Among the latter, a novel design based on polymer composite materials of total hip replacement prosthesis is under development. One of the key characteristics of this biomimetic prosthesis is its hydroxyapatite coating, which permits Osseo integration (integration into the bone). Thermally sprayed hydroxyapatite coatings are already used successfully for metallic implants, but plasma sprayed hydroxyapatite coatings have yet to be developed for polymer composites due to quite challenging heat management and adhesion concerns. This paper describes and discusses the optimization of the plasma sprayed technique and the formation of the adequate underlayer enabling the plasma spray on highly heat sensitive substrate. Adhesion, shear and fatigue results are presented. Abstract only; no full-text paper available.
Optimizing of LVOF Spray Parameters to Coat Ceramics by Studying Particles In-Flight Characteristics
Authors: Modi S.C. , Modi A. , Rayudu G.R.
Published: August 2022

A new variant of LVOF system was developed to deposit ceramics. For this study Cr2O3 powder was used. To save on time and reduce mathematical iterations optimizing of parameters was carried out by using an online particle diagnosing system. The spray parameters were varied to study their influence on the particle in-flight characteristics. The parameters which gave best particle temperature and velocity was used for coating. The resulted coating was dense and hard.
Research on Microstructure and Properties of Ni-Al2O3 Coatings Produced by HVO/AF
Authors: Hangong W.
Published: August 2022

In the paper, Ni-Al2O3 coatings were prepared by HVO/AF . The microstructure and composition of the Ni-Al2O3 coatings were investigated by metallographic microscope, scanning electron microscope and X-rayed diffraction, Bonding strength and hardness and mechanics properties were tested. The experimental results show the Ni- Al2O3 coatings possessed high microhardness and higher bonding strength with substrate and excellent comprehensive mechanical properties. Abstract only; no full-text paper available.
Air Gas Dynamic Spraying of Powder Mixtures: Theory and Application
Authors: Maev R. , Aczel A. , Leshchynsky V. , Salloum G. , Islam M.-Ui
Published: August 2022

The Radial Injection Gas Dynamic Spray (RIGDS) technology of powder wear resistant coatings deposition is considered. A coating is created by injection of powders with variable composition into the supersonic air jet and deposited on the substrate. Functionally graded coatings with advanced mechanical and corrosion properties were produced and tested. It is shown that operational parameters of supersonic powder-gas jet have a significant influence on the coating’s microstructure, thus defining the high performance of the coating. Compaction and bonding of particles were analyzed. Shear localization features of the GDS process are also discussed.
Influence of the Spray Parameters and Particle Size on the Treatment of Fe-Cr and Stainless Steel Particles in Flight in APS
Authors: Ageorges H. , Ctibor P. , Fauchais P.
Published: August 2022

The aim of this paper is to study the influence of plasma spray set-up parameters, such as the hydrogen percentage in the plasma forming gas and arc current, as well as powder injection parameters: the carrier gas flow rate and injected particle size on the melting, vaporization and velocity of particles of a Fe-Cr based alloy and stainless steel AISI 316L. Particles were collected in flight in a cylinder where they were quenched by argon jets to prevent there flattening at impact and chemical interaction with their environment. After collection, particles were analyzed by SEM, EDS and X-ray diffraction. When the injected particle size was between 60 and 100 µm, particles collected in flight exhibit complex shapes with a mean diameter of 40 µm, and the higher was the percentage of hydrogen the smaller was the resulting mean diameter. This probably corresponds to an inefficient cooling by the argon jets resulting in particles impacting at the bottom of the collector and partially exploding. When the injected particle size was between 10 and 35 µm, collected particle were nearly spherical with almost the same mean diameter, but then the oxidation changed with spray parameters. Measurements of temperature and velocity of the in-flight particles during plasma spraying were done using the Spray Watch (Oseir, Finland) equipment. Relationships between in-flight particle parameters and characteristics of the collected particles were found. Abstract only; no full-text paper available.
Analysis of Bonding Mechanisms during Thermal Spraying
Authors: Kudinov V.V.
Published: August 2022

The paper is a brief overview of data obtained by A.A. Baikov Metallurgical Institute of the Russian Academy of Science in the field of bonding mechanisms for thermal spray processes. The following 3 phases of bonding are considered: forming of a physical contact between a particle and a substrate; activation of the contacted surfaces and possible chemical interaction between a spraying particle and a substrate; diffusion. Thermal and mechanical activation of a substrate are considered in the paper. It is shown that thermal activation by molten particles and substrate preheating have a major input into the bonding process of the thermal spray processes such as APS, twin wire arc and flame spraying with relatively low velocity of molten particles. Application of high velocity processes like HVOF, HVAF and Cold Spray changes the mechanism of bonding activation. In this case the deformation of a substrate in the contact zone and related bonding activation caused by dislocations play a major role in the bonding of a particle with a substrate. It is shown that the energy needed for bonding depends mainly on the properties of the substrate and the particle materials.
The Relation between the Morphology of Powders and the Spraying Parameters and Structure of Coatings in the HVOF Spraying
Authors: Huang X. , Zhang T. , Sun Y.
Published: August 2022

Research and selection the performance requirements for the coating, at the same time obtain the WC-Co powders with high efficient spray rate and low cost, through research on the relation between the WC-Co powders sprayed by the HVOF in different morphology and in different manufacturing process and the spraying parameters and structures of coatings. Abstract only; no full-text paper available.
Thermal Spraying of Basalt for Abrasion Protective Coatings using WSP, HVOF and APS
Authors: Oberste Berghaus J. , Moreau C. , Chráska P. , Chráska T.
Published: August 2022

Basalt, an abundant and inexpensive natural raw material, is a glass-ceramic with good abrasion-wear resistance and chemical stability. Traditionally cast-shaped into flag stones, pipe linings and even fibrous composites, basalt can be processed by thermal spraying, potentially yielding highly dense coatings with few defects. Such overlays can seal base materials for wear applications in corrosive environments. Basalt coatings are produced by a number of common thermal spray techniques, including water-stabilized plasma spraying (WSP), high-velocity oxy-fuel (HVOF) and conventional air plasma spraying (APS). In-flight particle temperature and velocities are monitored with a particle diagnostic system (DPV 2000). Using different feedstock size cuts, the attainable ranges of particle states are delineated. Spray parameters are selected for each of the processes, based on deposition efficiency and porosity criteria. For typical conditions, particle velocities vary from 100 m/sec for WSP to 800 m/sec with HVOF. The microstructure and composition of the coatings are evaluated by scanning electron microscopy (SEM) and EDS-SEM. Crystal phase analysis is performed by X-ray diffraction (XRD). Abrasion resistance (ASTM G-65) and hardness (Vickers) of the as-sprayed coatings are compared. The microstructures and tribological properties are related to the particle size, temperature and velocity distributions, which are distinctly different for each process.
CGS Sprayed Filler Coatings for Brazing of Light Weight Alloys
Authors: Wielage B. , Grund T. , Ahrens S. , Wank A. , Trommer F.
Published: August 2022

Application of cold gas spraying for deposition of braze filler coatings is investigated. Different light weight alloy substrates, i.e. aluminum AA1050, AA3005, AA5754 and AA7022, magnesium AZ91 and titanium TiAl6V4, are used. Filler coating materials depend on the substrate melting temperature. So for aluminum alloys Al12Si and zinc based fillers, for AZ91 pure zinc and for Ti6Al4V different Cu-Ni blends are applied. CGS process parameters are varied with regard to process gas (nitrogen) temperature and pressure, powder feed rate and spray distance. Correlation to process characteristics and economical aspects are given. The usability of the produced filler coatings is shown by different optimized brazing/soldering processes. In case of aluminum braze joints a full metallographical investigation is carried out by optical and scanning electron microscopy as well as EDXS analyses. The gathered results are compared with those of conventional filler material addition, i.e. wire, roll plating and foil.
Effect of Annealing Treatment on the Microstructure and Properties of Cold-Sprayed Cu Coating
Authors: Li W.-Y. , Li C.-J.
Published: August 2022

In the present study, Cu coating was deposited by cold spraying and the electrical resistivity of the coating in both directions parallel and perpendicular to the coating surface was measured to investigate the anisotropy of the coating. Annealing treatment was applied to the coating to examine its effect on the microstructure and properties of cold-sprayed Cu coating. The examination of coating microstructure evidently revealed that the coating was constituted by flattened particles and the interfaces were clearly observed between the deposited particles. The anisotropy in microstructure and electrical resistivity was present in cold-sprayed Cu coating. The electrical resistivity of the as-sprayed coating was higher than that of Cu bulk. Moreover, the electrical resistivity along the direction parallel to the coating surface was lower than that along the perpendicular direction. On the other hand, it was found that the annealing led to the enhancement of particle interface bonding and evident recrystallization of the elongated grains and remarkable grain growth as well. The annealed coating presented an equiaxed grain structures similar to annealed Cu bulk with particle interfaces almost disappeared under certain annealing condition. The coalescence of voids or oxides in the coating was clearly observed at high annealing temperature. Moreover, the annealed coating yielded an electrical resistivity and microhardness comparable to Cu bulk.
Laser Coating and Thermal Spraying - Process Basics and Coating Properties
Authors: Vuoristo P. , Tuominen J. , Nurminen J.
Published: August 2022

The paper describes the some differences of laser coating (laser cladding or laser spraying) process in comparison to thermal spraying. Laser coating is a novel coating process, which produces coatings with high density, metallurgical bonding and low heat input to the substrate. Laser coating types and coating properties are reviewed and compared with thermally sprayed coatings. Typical application areas of laser coatings are presented.
A Multi-Wire ARC-HVOF Hybrid Gun
Authors: Kosikowski D.M. , Stanisic J, J. , Mohanty P.S.
Published: August 2022

This paper presents process development efforts aimed at exploiting the benefits of both the electric arc-spray technique and the High Velocity Oxygen Fuel (HVOF) technique. This so-called hybrid process offers the benefits of using wire stock and high deposition rates of an electric arc-spray gun combined with the higher coating densities obtained using a HVOF gun. Various configurations starting from a single wire arc to 4-wire arc in combination with HVOF have been investigated. Experiments with single material wires to multi-material wire combinations have also been investigated. The feed rates of individual electric arc wire pairs and HVOF powder/wire are controlled independently allowing the creation of functional gradient materials (FGM). This gun has been used to create alloys as well as patterned deposits of different materials. The ability to create in-situ alloys and patterned deposits with excellent quality has been demonstrated.
Parametric Study of the Transient Cooling During Suspension D. C. Plasma Spraying of Stabilized Zirconia
Authors: Naoua S.B. , El Ganaoui M. , Fauchais P. , Sammouda H.
Published: August 2022

A numerical study has been conducted on yttria stabilized zirconia and molybdenum splat cooling taking into account the effects of various parameters. In particular, the effect of the splat thickness, the splat/substrate interface thermal resistance, the latent heat of solidification and the substrate initial temperature on the solidification occurrence and kinetics have been studied. A two-dimension model of heat transfer taking into account the phase change during rapid solidification with an enthalpy formulation has been used for these calculations.
Microstructure Characterization of Thermal Barrier Coating Deposits – Practical Models from Measurements
Authors: Ilavsky J. , Allen A.J. , Dobbins T. , Kulkarni A. , Herman H.
Published: August 2022

Advances in the functional properties of thermal barrier coating (TBC) deposits are important for increasing the efficiency of, and reducing emissions from both stationary and aircraft turbine engines. Computer modeling is the preferred method for developing new materials with minimum cost and development time. However, modeling of TBCs is complex and must take into account interactions among the layers and with the substrate, in-service phase changes, oxidation, and stress development. Understanding the microstructure of the ceramic layer is important for building these models, as it strongly influences the properties responsible for the basic TBC function – thermal resistance. As is well known the ceramic microstructure changes in service, potentially leading to coating and engine failure. A major challenge is ensuring that the model reliably describes the actual material. Thus, it is important to develop representative models, which can be related to real practical coating systems. We present such a model. It has been developed to interpret small-angle X-ray scattering data that characterize TBC ceramic deposit microstructures. This model is also suitable for incorporation into computer algorithms such as are used in finite-element analysis. Quantitative parameters that describe the microstructure changes occurring under service conditions are readily obtainable for current systems, and these can then be re-measured for future materials of interest.
Numerical Study of Particle In-Flight Characteristics in a RF Induction Plasma Spray
Authors: Xiong H.B. , Zheng L.L. , Zhang M.Y. , Zhang H. , Margolies J. , Sampath S.
Published: August 2022

Precursor Plasma Spraying (PPS) using Radio Frequency (RF) induction plasma spray is a new process used to synthesize functional materials. RF plasma spray has the advantages of stability, cleanness, high temperature and high chemical reactivity. In this paper, a two-dimensional numerical model has been developed to investigate the induction electromagnetic (EM) field and the thermo-fluid field in a radio frequency inductively coupled plasma (RF-ICP). In flight particle interaction with the plasma jet will be investigated. The traditional micron-size powder particles, e.g. zirconia (PSZ), are injected with carrier gas such as argon. During their interaction with the RF plasma, the powder particles experience acceleration, heating, melting and evaporation and particle heat transfer is considered coupled with the thermo-fluid flow of the RF plasma. A generalized particle model is developed and applied to the precursor plasma spray process operated in a vacuum chamber. The effects of power input, standoff distance and powder size on the RF plasma and particle in flight characteristics are investigated.
New Thermal Spray Coatings from WC-VC-Co Powders
Authors: Machio C.N. , Luyckx S. , Zimmermann S. , Keller H.
Published: August 2022

Thermal spray coatings were deposited by the HVOF technique using two grades of WC-VC-Co powders (WC- 10VC-12Co and WC-10VC-17Co), produced by agglomeration and sintering, from WC, VC and Co starting powders. The coatings were sprayed by a commercial enterprise producing WC-Co thermal spray coatings, using the same spray parameters as for WC-Co coatings. This paper presents results from the characterization of the powders as well as the results of abrasion and erosion tests performed under identical conditions on the new WCVC- Co coatings and on standard WC-Co coatings of equal cobalt content. Under many conditions, the WC-VC-Co coatings performed better than the standard coatings, despite their deposition conditions not having been optimized.
Microstructure Analysis of Thermally Sprayed Abradable Coatings
Authors: Faraoun H.I. , Seichepine J.-L. , Aourag H. , Coddet C. , Grosdidier T. , Zwick J. , Hopkins N.
Published: August 2022

This paper reports morphological study of coatings microstructure performed on two selected reference abradable materials: AlSi-hBN and NiCrAl-Bentonite. Scanning Electron Microscopy (SEM) was used to obtain adequate micrographs for analysis. The porosity and non-metal particles morphology was assimilated to elliptical inclusions within the metallic matrix. Accordingly, they were described by means of three different geometrical parameters related to the shape, size and orientation distribution, allowing additional statistical analysis on the coatings.
Analysis of Thermal Fluxes from an Impinging HVOF Jet
Authors: Klein D. , Bolot R. , Verdy C. , Coddet C.
Published: August 2022

The knowledge of thermal fluxes transferred from impinging high temperature jets is always important. For example, during thermal spray applications, the impinging jet acts directly on the transient surface temperature of the substrate. For preheating applications, it acts on the time required to reach the required surface temperature. It is also important to estimate it for some other applications like thermal cycling tests of parts for example. In the present paper, both CFD computations and experiments were carried out in order to quantify thermal fluxes from an impinging HVOF jet. The case of a CDS gun fueled by natural gas was considered. Stand-off distances ranging from 50 mm up to 300 mm were investigated. The model incorporates a 2-layer extension to k-å models for a better estimation of thermal exchanges through the viscous layer on the front body surface. The experiments were performed using a system incorporating two square calorimeters positioned one beside the other in order to attempt defining a radial profile. Abstract only; no full-text paper available.
KORUNMA MUHASEBESİ UYGULAMASININ BELİRLEYİCİLERİ VE KAZANÇ DALGALANMASINDA KORUNMA MUHASEBESİ ETKİSİ
Authors: KALDIRIM Yusuf
Published: August 2022

TFRS 9, finansal riskten korunma ve koruma muhasebesi uygulamasına yönelik düzenlemeler getirmektedir. Bu çalışmanın amacı, BIST Sınai endeksinde işlem gören şirketlerde korunma muhasebesi uygulamasında belirleyici olan faktörleri ve kazanç dalgalanmasında korunma muhasebesi uygulamasının etkisini araştırmaktır. Ulaşılan bulgular, bağımsız denetim firması, firma büyüklüğü, şirket yaşı ile korunma muhasebesi uygulaması arasında anlamlı ilişki olduğunu göstermektedir. Kazanç dalgalanmasına yönelik bulgular ise, korunma muhasebesi uygulamasının şirketlerin kazançlarındaki oynaklığı azalttığına dair anlamlı kanıt ortaya koymamıştır. Çalışma ortaya koyduğu bulgular ile konuya ilişkin sınırlı sayıdaki literatüre katkıda bulunmaktadır.
Experts’ perspective towards smart management in the post-war reconstruction of the city of Mosul
Authors: Abdulla Zina Riadh , Hussein Shaimaa Hameed
Published: August 2022

Motives: Urban developers around the world have been using smart management systems in redeveloping cities. This strategy allows a sustainable long term approach, built on scientific findings. Accurate data and information are key in achieving smart management in the reconstruction of post-war areas. Having the right information at the right time helps government officials, service providers and residents themselves make better choices when it comes to the reconstruction of post-conflict areas.
Aims: This paper explores the role of resident experts’ contribution and how they can aid officials make more educated choices when it comes to urban decision making. It also addresses the ambiguity of the impact of using the expertise of local urban planners and architects in urban decision making in the reconstruction process as one of the strategies to achieve a smart city. The Old City of Mosul was selected by the authors as a case study in the post-war regeneration process. Therefore, the paper attempts to reach a scientific decision in selecting the best approach towards the urban regeneration of the Old City of Mosul.
Results: The paper signifies the role of the local community experts in urban decision making as a bottom to top approach, and recommendations were made based on the research findings.
Introduction
Authors: Aragüete-Toribio Zahira
Published: August 2022

English Abstract:
In recent (post-)conflict scenarios, the diversity and complexity of mass violence, including acts of enforced disappearance and extrajudicial or summary executions, have transformed how knowledge about such crimes is performed and produced socially. In inquiries into human rights violations, the search for, exhumation and identification of missing bodies often buried in mass graves have led distinct applications of forensic work to emerge. These have some differences from traditional crime scene investigation approaches. Novel interactions between forensic science practitioners and the communities where they operate have given place to unprecedented sociocultural, affective and scientific understandings of evidencing mass crimes. Drawing on different ethnographic experiences of unearthing human remains around the world, this collection considers how, in its judicial but also its extrajudicial application, forensic expertise has been transformed in connection to other epistemologies, collective and individual mourning, kinship, memory and a new politics and ethics of care in distinct state- and civil society-led pursuits to account for the dead and missing.

French Abstract:
Dans les scénarios récents de (post-)conflit, la diversité et la complexité de la violence de masse (y compris les actes de disparition forcée et les exécutions extrajudiciaires ou sommaires) ont transformé la manière dont la connaissance de ces crimes est acquise et produite socialement. Dans le cadre des enquêtes sur les violations des droits de l’homme, la recherche, l’exhumation et l’identification des corps disparus, souvent enterrés dans des fosses communes, ont suscité l’émergence d’applications distinctes du travail médico-légal. Celles-ci diffèrent des approches traditionnelles des enquêtes sur les scènes de crime. Les nouvelles interactions entre les praticiens de la médecine légale et les communautés où ils opèrent ont donné lieu à des compréhensions de la mise en évidence des crimes de masse socioculturelles, affectives et scientifiques sans précédent. En s’appuyant sur différentes expériences ethnographiques de mise au jour de restes humains à travers le monde, cette collection examine comment, dans son application judiciaire mais aussi extrajudiciaire, l’expertise médico-légale a été transformée en relation avec d’autres épistémologies, le deuil collectif et individuel, la parenté, la mémoire, ainsi qu’une nouvelle politique et une nouvelle éthique de la prise en charge dans le cadre des efforts distincts menés par l’État et la société civile pour rendre compte des morts et des disparus.
Managing Mass Graves in Rwanda and Burundi
Authors: Jamar Astrid , Major Laura
Published: August 2022

English Abstract:
The governments of Rwanda and Burundi exhume mass graves with the promise of revealing truths about the contested histories of past conflict and genocide. In Rwanda, exhumations recover and conserve the bodies of victims of the genocide against the Tutsi. Since December 2019, the Truth and Reconciliation Commission in Burundi has also begun mass exhumations; these efforts are motivated by truth-seeking and reconciliation aspirations that articulate a specific narrative of victimhood and state legitimacy. The state employs vernacularised forms of forensic practices and ‘international’ rights-based discourses in both cases. Drawing on our respective ethnographic fieldwork, we describe and analyse exhumation practices in Rwanda and Burundi. The ‘forensic turn’ in post-conflict settings has been the subject of much discussion and debate among scholars since the proliferation of the practice over recent decades. We add to these debates in our consideration of two linked settings in which the exhumations had become powerful political tools, in this case serving as a source of power for specific regimes.

French Abstract:
Les gouvernements du Rwanda et du Burundi exhument des fosses communes en promettant d’éclaircir les vérités sur les histoires contestées des conflits et des génocides passés. Au Rwanda, les exhumations ont été organisée pour récupérer et conserver les corps des victimes du génocide contre les Tutsis. Depuis décembre 2019, la Commission Vérité et Réconciliation au Burundi a également entamé des exhumations de masse ; ces efforts sont motivés par des ambitions de recherche de la vérité et de réconciliation articulées autour d’un récit spécifique de victimisation et de légitimation de l’État. Dans les deux cas, l’État utilise des formes vernacularisées de pratiques médico-légales et des discours « internationaux » fondés sur les droits. En nous appuyant sur nos travaux ethnographiques de terrain respectifs, nous décrivons et analysons les pratiques d’exhumation au Rwanda et au Burundi. Le tournant médico-légal » dans les contextes post-conflits a fait l’objet de nombreuses discussions et débats parmi les chercheurs depuis la prolifération de ces pratiques au cours des dernières décennies. Nous contribuant à ces débats en examinant deux contextes liés dans lesquels les exhumations sont devenues de puissants outils politiques, servant dans ce cas de source de pouvoir pour des régimes spécifiques.