bluuebunny/crossref_metadata_2025 huggingface dataset:
Unique Thermal Spray Cabinet with High Enthalpy Plasma
Authors: van Wonderen M.
Published: September 2022

KLM Royal Dutch Airlines has the oldest Maintenance, Repair and Overhaul (MRO) shop for aircraft in the world (more than 80 years old). The company’s philosophy in all areas, including thermal spray, has always been to pursue the latest innovations and to maintain well-equipped facilities with state-of-the-art processes, equipment and materials for performing repairs. In the area of thermal spray, the latest procurement is a state-of-the-art unique cabinet with a high enthalpy plasma spray process. This new cabinet and new plasma spray process provides up-to-date technology for applying thermal spray coatings on aircraft engines. In this paper, experiences and the latest results obtained using this system to deposit various types of coatings used on aircraft will be reported.
The Way to CE Conformity for Equipment in Thermal Spray
Authors: Wernli H. , Kammermann F. , Moll R. , Windler W.
Published: September 2022

The advantages of thermal spray technology open an increasing number of applications in several fields. However, it has to be considered that thermal spray processes contain several, partly substantial potentials of danger. As other machinery in Europe, thermal spray equipment is subject to essential health and safety requirements. This paper lists the necessary steps for the manufacturer to develop and to bring into market machinery and parts of machinery that are in conformity with the CE requirements. “CE” represents “Communauté Européenne”, the French term for the European Community. The directives, codes and legal basics, the procedure of risk assessment, the requirements to the technical documentation as well as the conditions regarding declaration and marking are discussed under the point of view of thermal spray. Some sections treat the status of modified and reconditioned machinery, the duties of users of thermal spray equipment as well as similarities and differences in the requirements in Europe to other markets.
Metallic Fume Emission and Operator Exposure During WC-10%Co-4%Cr Spraying by HVOF
Authors: Legoux J.-G. , Oberste Berghaus J. , Moreau C.
Published: September 2022

The increasing use of HVOF (high-velocity oxy-fuel) coatings to replace hard chrome plating was initially motivated by the environmental and health risks associated with hexavalent chromium (Cr6+) emissions during the plating process. Following performance optimization and proper coating selection, it has been found that the potential increase in performance and the cost/process-time reduction offered by the HVOF process often justifies its application. Recently, the use of Cr-containing alloys processed by HVOF has drawn attention to the potential release of Cr6+ during heating of metallic chromium. For instance a new California regulation for airborne toxic control measures to reduce emission of hexavalent chromium from thermal spraying is in preparation. The present study focused on monitoring operator exposure during the HVOF spraying of WC-10%Co-4%Cr. The spraying was performed using a JP-5000 HVOF gun in a spray room in which a ventilation flow rate of 10,000 scfm was imposed. Air sampling was taken in the spray room as well as in the adjacent control room in accordance with the NIOSH 7300 and 7600 standard methods. A portable sampler attached on the operator’s chest was also used to monitor the operator exposure during a typical workday. Results indicate that even though metallic fumes of Co and Cr are present in the spray room during spraying, the hexavalent form Cr6+ is not detected. It was concluded that an operator entering the spray room for a limited amount of time with the gun in operation would be exposed to only low fume levels that can still be reduced by wearing an appropriate respiratory mask.
Influence of Industrial Gases on the Thermal Spray Process
Authors: Kroemmer W. , Heinrich P.
Published: September 2022

The trend in thermal spraying is more and more towards a globally uniform level of high-grade spray coatings. It is therefore extremely important that auxiliaries such as spray materials or industrial gases undergo precise examination in order to exactly define their influence. Based on their application, these auxiliary materials can always be supplied at the required purity level. In order to guarantee such high levels, the gas industry invests a great deal in analysis and supply concepts which ensure this purity from the tank or cylinder through to the point of delivery. A further point is of particular significance in today’s business world. With ever-increasing raw material prices, it is absolutely essential that spray processes are optimized to the maximum. This is not only made possible by selecting the right system, but also by choosing the right gas and gas mixture.
GTS Certificate—A Successful Means of Benefiting Its Members
Authors: Böhme D. , Huber R. , Grasme D. , Heinrich P.
Published: September 2022

The GTS certificate, is the only certificate worldwide which, in addition to the quality management elements of DIN EN ISO 9001:2000, includes a personnel, process and, on request, also a product certification for thermal spraying. The rules for certification were worked out by the thermal spray users, i.e. GTS members, themselves and have proved to be very effective. Today, the GTS certificate serves as a basis for assessing a certified GTS member should inconsistencies or legal disputes arise. The certificate demonstrates that the certified company has a visible quality standard and that it also meets specified quality requirements in its day-to-day business operations.
Impact Fusion of Particle Interfaces in Cold Spraying and Its Effect on Coating Microstructure
Authors: Li W.-Y. , Zhang C. , Guo X.P. , Dembinski L. , Liao H. , Coddet C. , Li C.-J.
Published: September 2022

In this study, the impact melting phenomenon at the interfaces of particles deposited by cold spraying and its effect on coating microstructure were examined. Different powders with various thermal and mechanical properties were selected as feedstock. They are respectively Al2319, Ti, Ti-6Al-4V, Ni and MCrAlY powders. The results showed that most of the sprayed materials possibly experienced local melting at the contact interfaces of particles under certain gas conditions. Low melting point and reaction with the atmosphere are the two main factors contributing to the impact fusion during cold spraying. The results indicated that the local melting would benefit the formation of the metallurgical bonding between the deposited particles and enhance the coating adhesion.
Numerical Study of Combination Parameters for Particle Impact Velocity and Temperature in Cold Spray
Authors: Katanoda H. , Fukuhara M. , Iino N.
Published: September 2022

Numerical simulations of gas/particle flows of cold spray are performed for N2 and He as a process gas respectively, to investigate the usefulness of the two material-independent combination parameters derived from the equations of particle motion and temperature. The first combination parameter is the particle-diameter multiplied by the material density, which governs the particle velocity. The second one is the squared particle-diameter multiplied by the material density and specific heat, which affects the particle temperature. In the numerical simulation, the materials of the spray particle selected are WC-12Co, Cu and Ti. The diameter of the particle is in the range of 0.1 – 30 µm. The present numerical results show that the maximum impact velocity of particle is obtained when the first combination parameter takes specific value regardless of the material type. Furthermore, it is shown that the particle diameter and its temperature corresponding to the maximum impact velocity can be graphically estimated by using the two combination parameters for any powder-materials normally used for the thermal spray.
Deposition Behavior of Sprayed Metallic Particle on Substrate Surface in Cold Spray Process
Authors: Fukumoto M. , Wada H. , Tanabe K. , Yamada M.
Published: September 2022

Self designed cold spray equipment was installed in the laboratory and deposition behavior of sprayed individual metallic particles on the substrate surface was fundamentally investigated. As a preliminary experiment, pure Cu particles were sprayed on mirror polished stainless steel and Al alloy substrate surfaces. Process parameters changed systematically were particles diameter, working gas, gas pressure, gas temperature and substrate temperature, and effect of these parameters on the flattening or adhesive behavior of an individual particle was precisely investigated. Deposition ratio on substrate surface was also evaluated on these parameters. From the results obtained, it was quite noticeable that the higher substrate temperature brought about higher deposition rate of Cu particles even under the condition with particles temperature kept at room temperature. This tendency was promoted more effectively by using helium instead of air or nitrogen as a working gas. Both higher velocity and temperature of the particles sprayed are the necessary conditions for the higher deposition ratio in the cold spraying. However, instead of particles heating, substrate heating may bring about the equivalent effect for the deposition of the particles. This finding is quite new and has never been reported.
Investigation of Al-Al2O3 Cold Spray Coating Formation and Properties
Authors: Irissou E. , Legoux J.G. , Arsenault B. , Moreau C.
Published: September 2022

Coating build-up mechanisms and properties of cold sprayed aluminum-alumina cermets were investigated. Two spherical aluminum powders having average diameters of 36 and 81 microns were compared. Those powders were blended with alumina at several concentrations. Coatings were produced using a commercial low pressure cold spray system. Powders and coatings were characterized by electronic microscopy and microhardness measurements. In-flight particle velocities were monitored for all powders. The deposition efficiency was measured for all experimental conditions. Coating performance and properties were investigated by performing bond strength test, abrasion test and corrosion tests, namely, salt spray and alternated immersion in salt water tests. These coating properties were correlated to the alumina fraction either in the starting powder or in the coating.
Development of Coatings and the Influence of Industrial Gases on the Thermal Spray Process
Authors: Kroemmer W. , Heinrich P.
Published: September 2022

Not least because of the multitude of the possibilities which this process has to offer, has thermal spraying established itself in an extremely wide range of industrial sectors. In quest of new applications, special attention is frequently paid to the properties of individual systems. However, the trumps of the process can only be played out in combination with all the components as a whole. In industry nowadays, it is often the costs alone which are hotly disputed, and especially so when it comes to industrial gases. Yet precisely here infinite opportunities present themselves to positively influence the process. Starting with the optimization of costs, followed by the lifetime of the systems, through the variety of coating properties which can be tailored to the application, the influencing variables are endless. Investigations into this potential are already in full swing. Powder manufacturers are testing the many possibilities in their laboratories and have put their heads together with the R&D departments of hardware and gas suppliers in an effort to continually broaden the coating spectrum.
Numerical Simulation of the Solution Precursor Plasma Spraying Process
Authors: Shan Y. , Coyle T.W. , Mostaghimi J.
Published: September 2022

Solution precursor plasma spraying has been used to produce finely structured ceramic coatings with nano- and sub-micrometric features. This process involves the injection of a solution spray of ceramic salts into a DC plasma jet under atmospheric condition. During the process, the solvent vaporizes as the droplet travel downstream. Solid particles are finally formed due to the precipitation of the solute, and the particle are heated up and accelerated to the substrate to generate the coating. This paper describes a 3D model to simulate the transport phenomena and the trajectory and heating of the solution spray in the process. The jet-spray two-way interactions are considered. A simplified model is employed to simulate the evolution process and the formation of the solid particle from the solution droplet in the plasma jet. The temperature and velocity fields of the jet are obtained and validated. The particle size, velocity, temperature and position distribution on the substrate are predicted.
Development of Superabrasive Composite Layers through Thermo-Kinetic Coating-Technologies
Authors: Tillmann W. , Nebel J. , Vogli E.
Published: September 2022

Superabrasive composite materials are typically used for grinding stone, minerals and concrete. Sintering and brazing are the key manufacturing technologies for grinding tools production. But restricted geometry-flexibility, absence of repair possibilities for damaged tool surfaces as well as difficulties in controlling materials interfaces are main weaknesses of these production processes. Thermal spraying offers the possibility to avoid these restrictions. In this research work a fabrication method based on the detonation flame spraying technology has been investigated to bond large superabrasive particles (150 – 600 µm, needed for grinding minerals and stones) in a metallic matrix. Layer morphology and bonding quality are evaluated with respect to superabrasive material, geometry, spraying- and powder-injection-parameters. Influences of process temperature and possibilities of thermal treatment of MMC-layers are analyzed.
Several Application Cases of Thermal Spraying Technology on Industrial Components and Its Considerations
Authors: Huang X.O. , Wang R.J. , Zhang T.-J. , Luo H.J. , Lű Y.F.
Published: September 2022

Thermal spraying technology was one of the listed advanced manufacturing technologies to be developed with great effort in “the eleventh five-year” programming and the perspective layout for the years to 2020 of China. It is also a very important technology to promote establishment of economical society. This paper analyzed some application cases of thermal spraying technology to several typical components such as the corrugated roller used for packaging industry, injection molding screw for plastic industry, insulated bearing for railway industry and ball valve with large diameter for petroleum & chemistry industry which were practiced by Surface Engineering Research Institute of CAAMS in recent years. This paper presented some new developments on applications of thermal spraying technology in China and some considerations on the developing trends of thermal spraying applications in China in future are put forward in comparison with the current situation of oversea thermal spray practices.
Influence of H2SO4 Treatment on Biological Properties of Plasma Sprayed Titania Coatings
Authors: Li B. , Li X. , Zhao X. , Ding C.
Published: September 2022

In this work, the plasma sprayed titania coatings were treated by H2SO4 for 24h at room temperature to improve the biological properties. The bioactivity was measured by simulated body fluid soaking test, and the biocompatibility was evaluated by quantifying the grafted collagen amount and in vitro cell culture test. The results showed that titania coatings treated by 0.1M and 1M H2SO4 can induce bone-like apatite formation after immersion in SBF for 28 days, while the titania coating treated by 0.01M H2SO4 can not. H2SO4 treatment can promote the grafting of collagen on titania coatings. The in vitro cell culture test confirmed that collagen improved the cellular adhesion and proliferation on titania surface. In conclusion, a certain concentration of H2SO4 treatment is beneficial in improving the bioactivity and biocompatibility of plasma sprayed titania coatings.
Effect of Thermal Spray Condition on Characterization of Thermal Barrier Coating
Authors: Arai M. , Wada E. , Kishimoto K. , Ohno N.
Published: September 2022

It is well known that thermal spray condition affects the coating properties such as porosity, elastic modulus, coefficient of thermal expansion (CTE), coating fracture strength and coating cohesive strength. Therefore, residual stress formed in the sprayed coating and coating stress generated during in-service is dramatically changed with the thermal spray condition. In this study, effect of several kinds of thermal spray conditions on these properties of the coating was examined experimentally. Typical thermal barrier coating system composed of a partially stabilized zirconia (its chemical composition is 8wt%Y2O3-ZrO2) and CoNiCrAlY bond coating was selected herein. In-flight particle velocity and temperature, and the substrate temperature were changed as the thermal spraying process parameters varied. For the ceramic coating layer, the coating properties such as porosity, Vickers hardness, CTE, elastic modulus, bending fracture strength, fracture toughness of splat boundary and then coating residual stress were measured systematically.
Electromagnetic and Mechanical Properties of Silica - Aluminosilicates Plasma Sprayed Composite Coatings
Authors: Cipri F. , Bartuli C. , Valente T. , Casadei F.
Published: September 2022

The physico-chemical and thermo-mechanical properties of aluminosilicate ceramics (high melting point, low thermal expansion coefficient, excellent thermal shock resistance, low density and good corrosion resistance) make this class of materials a good option for high temperature structural applications. Al2O3-SiO2 compounds show an excellent refractory behaviour allowing a wide use as wear resistant thermal barrier coatings, in metallurgical and glass plants and in high temperature heat exchangers. Moreover the low values of thermal expansion coefficient and of complex permittivity allow to extend the use of this ceramic for microelectronic devices, radome for antennas and electromagnetic windows for microwaves and infrared. The present paper presents the results of an extensive experimental activity carried out to produce thick aluminosilicate coatings by plasma spray technique. APS deposition parameters were optimized on the basis of a surface response approach, as specified by design of experiments (DoE) methodologies. Samples were tested for phase composition, total porosity, microstructure, microhardness, deposition efficiency, fracture toughness and modulus of rupture. Finally, coatings were characterized for their particularly interesting electromagnetic properties: complex permittivity was measured at microwave frequency using a network analyzer with wave guide.
Analysis of In-Flight Particle Properties of Ultrafine Powders
Authors: Bobzin K. , Ernst F. , Zwick J. , Brühl M. , Matthäus G.
Published: September 2022

Demands on functional coatings with high dimensional accuracy and high surface quality has led to increasing interest in processing of very fine powder grades in a particle size range < 25 µm. Fine powders are not only showing a distinct potential for application of thin and dimensionally accurate coatings, but are also very promising for the production of dense and homogeneous coatings with improved mechanical properties. The large specific surface of fine powders is allowing for relatively low thermal energy levels that are introduced into the process. Nevertheless this also requires a very sensitive temperature control, to prevent overheating of the particles. The reduction of the thermal energy level is resulting in significant advantages particularly for the usability of the HVOF process for coating of inner diameters. Within this work in-flight particle properties of ultrafine carbide powders were analyzed. The studied HVOF process allows the adjustment of a broad parameter range by utilization of a hydrogen stabilized liquid fuel combustion process. A conventional straight nozzle type as well as a curved nozzle for internal spraying was studied. For a further assessment of the potential of ultrafine carbide powders also spray trials with a plasma spraying system have been made.
Repeatability of Measuring Method for HVOF Application
Authors: Malavolta C. , Liao H. , Zhang Ga , Coddet C. , Keller S. , Hansz B.
Published: September 2022

A statistical study of the Spraying Xplorer AMT system was undertaken in order to check that if it can be used as a means of assistance for on-line production control. A patented procedure of the system calibration is explained and some results are presented.
Microstructure Characterization and Property of Plasma Sprayed Nanostructured TBCs
Authors: Li Q. , Li S. , Yang W.
Published: September 2022

The technology and thermal shock properties and thermal conductivity of plasma sprayed nanostructured yttria-stabilized zirconia thermal barrier coatings (TBCs) are studied in this paper. The TBCs on the substrate of Ni3Al based alloy IC-10 were fabricated by using the nanostructured yttria-stabilized zirconia powder under certain plasma spraying conditions. By manipulating the plasma spray process, nanostructured TBCs were obtained. The specimens were thermally shocked from 1000°C, 1100 °C and 1200°C into 20°C water and the morphology and microstructure of the TBCs were evaluated by light microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The thermal diffusivity was tested by a laser pulse method. The results showed that the nanostructured TBCs had more than 30% reduction in thermal conductivity and the thermal shock lifetimes were much longer than that of the conventional TBCs.
Mechanical and Thermal Transport Properties of Suspension Thermal Sprayed Alumina-Zirconia Composite Coatings
Authors: Oberste Berghaus J. , Legoux J.-G. , Moreau C. , Tarasi F. , Chráska T.
Published: September 2022

Al2O3-ZrO2 composite coatings were deposited by suspension thermal spraying of submicron feedstock powders. The suspensions were injected internally into a Mettech Axial III plasma torch and a Sulzer-Metco DJ-2700 HVOF gun. The different spray processes induced a variety of structures ranging from finely segregated ceramic laminates to alloyed amorphous composites. Mechanisms leading to these structures are related to the feedstock size and in-flight particle states. Compositionally segregated crystalline coatings, obtained by plasma spraying, showed the highest hardness of up to 1150 Hv0.3, as well as the highest abrasion wear resistance (ASTM G65). The HVOF coating exhibited the highest erosion wear resistance (ASTM G75), which was related to the toughening effect of small dispersed zirconia particles in the alumina-zirconia alloyed matrix. The HVOF microstructures also led to low thermal diffusivity, due to high amorphous phase content and limited particle bonding.
HVOF-Sprayed Al2O3-TiO2 Coatings Using Hybrid (Nano+Submicron) Powders: An Enhanced Wear Performance
Authors: Lima R.S. , Moreau C. , Marple B.R.
Published: September 2022

In previous studies, it has been demonstrated that nanostructured Al2O3-13wt%TiO2 coatings deposited via air plasma spray (APS) exhibit higher wear resistance when compared to that of conventional coatings. This study aimed to verify if HVOF-sprayed Al2O3-13wt%TiO2 coatings produced using hybrid (nano+submicron) powders could improve even further the already recognized good wear properties of the APS nanostructured coatings. According to the abrasion test results (ASTM G 64), there was an improvement in wear performance by a factor of 8 for the HVOF-sprayed hybrid coating as compared to the best performing APS conventional coating. When comparing both hybrid and conventional HVOF-sprayed coatings, there was an improvement in wear performance by a factor of 4 when using the hybrid material. The results show a significant anti-wear improvement provided by the hybrid material. Scanning electron microscopy (SEM) at low/high magnifications showed the distinctive microstructure of the HVOF-sprayed hybrid coating, which helps to explain its excellent wear performance.
Induction Plasma Deposition of Refractory Metal: Processing Parameters Optimization
Authors: Fan X. , Boulos M. , Masini G. , Kovářík O. , Bensch J.
Published: September 2022

To prepare a dense, defect-free deposit of refractory metals relies not only on the droplets’ state, their temperature and velocity prior to impact on the surface of substrate and/or the precedent deposited layer, but also on the surface temperature of the substrate, whereupon the droplets impact. This paper presents a comprehensive investigation, in which the particles temperature, velocity, and the substrate temperature are studied all-in-one step to understand their influence on the deposit quality. The experimental results make our knowledge of the induction plasma spray of refractory metals process more integrated. Based on our estimation on the effect of all of the three factors, a set of optimized process parameters was established and proved by applying it in producing stationary deposits and coating layers. The results obtained distinguish the induction plasma spray a unique technique, which is ideal to be utilized in refractory metals deposit.
Transition Curvature in Flattening Behavior of Plasma Sprayed Metallic Materials
Authors: Fukumoto M. , Yamaguchi T. , Yamada M. , Yasui T.
Published: September 2022

A variety of metallic powder particles were thermally sprayed onto the mirror polished metallic substrate surface and the effect of both substrate temperature and ambient pressure on the flattening behavior of the particle was systematically investigated. In the flattening behavior of the sprayed particle onto the substrate surface, critical conditions were recognized both in the substrate temperature and ambient pressure. That is, the flattening behavior changed transitionally on that critical temperature and pressure range, respectively. A transition temperature, Tt, and transition pressure, Pt, were defined and introduced, respectively for those critical conditions. The fact that the dependence both of transition temperature and transition pressure on the sprayed particle material had similar tendency indicated that the wetting of the substrate by the molten particles seemed to be domination in the flattening. Three dimensional transition curvature by combining both transition temperature and transition pressure dependence was proposed as a practical and effective controlling principle of the thermal spray process.
Spraying Using Magneto-Plasma-Dynamic Arc Jet Generator
Authors: Tahara H. , Ando Y.
Published: September 2022

In magneto-plasma-dynamic (MPD) arc jet generators, plasma is accelerated by electromagnetic body forces. Silicon nitride reactive spraying was carried out using an MPD arc jet generator with crystal silicon rods and nitrogen gas. Because higher-velocity, higher-temperature and higher-density and larger-area plasmas are produced with the MPD arc jet generator than those with conventional thermal plasma torches, nitriding of silicon can be enhanced. A dense and uniform β-Si3N4 coating 30 µm thick was formed after 200 shots at a repetitive frequency of 0.03 Hz with a discharge current of 9 kA and a substrate temperature of 700 °C. The Vickers hardness reached about 1300. Furthermore, silicon carbide and aluminum nitride sprayings were conducted with the same spraying system. Surface modification is under study with lots of chemically reactive gases. All results showed that the MPD arc jet generator had high potential for spraying and surface modification.
Relation between the Arc Root Fluctuations, the Cold Boundary Layer Thickness and the Particle Thermal Treatment
Authors: Noguès E. , Fauchais P. , Vardelle M. , Granger P.
Published: September 2022

In plasma spraying, the arc root fluctuations, modifying the length and density of the plasma jet, have an important influence on particle thermal treatment. These voltage fluctuations are strongly linked to the properties of the cold boundary layer, surrounding the arc column, depending on the plasma spray parameters (composition and plasma forming gas flow rate, current, etc.) and the plasma torch design (anode-nozzle internal diameter and shape, etc.). In order to determine the influence of these different spray parameters on the cold boundary layer properties and voltage fluctuations, experiments were performed with two different plasma torches from Sulzer Metco. The first one is a PTF4 torch with a cylindrical anode-nozzle, working with Ar-H2 plasma gas mixture and the second one is a 3MB torch with both a conical and a cylindrical anode-nozzle, working with a N2-H2 plasma gas mixture. Moreover, the arc voltage fluctuation influence on particle thermal treatment was observed through the measurements of temperature and velocity of particles, using an yttria partially stabilized zirconia powder with a size distribution between 5 to 25 µm.
Process Characterization of LPPS Thin Processes with Optical Diagnostics
Authors: Gindrat M. , Refke A. , Schmid R.
Published: September 2022

Low pressure plasma spraying (LPPS) and LPPS-Thin Film (LPPS-TF) processes cover a broad operational pressure range from typically 200 mbar down to a few millibars, filling the gap between conventional thermal spray processes, where coatings are made from the liquid phase, and conventional thin film technologies such as PVD or CVD, where coatings are produced from precursors species in the vapor phase. Using some specific parameters of the LPPS-TF process, the injected material can be partially or even completely in gaseous phase, disqualifying diagnostics based on the detection of solid or liquid particles such as the DPV-2000 (Tecnar, St-Bruno, QC, CA). In this case, other optical diagnostic tools have to be used, such as optical emission spectroscopy (OES) to characterize the LPPS-TF process. In this paper, a qualitative study of the properties of the injected material in the plasma jet using DPV-2000 and optical emission spectroscopy is presented by varying specific plasma parameters. Moreover, in some particular cases, it is shown that the combination of DPV measurements and OES can help to monitor the coating process and to improve the basic understanding of the LPPSTF technology.
Detection of Wear in One-Cathode Plasma Torch Electrodes and Its Impact on Velocity and Temperature of Injected Particles
Authors: Mauer G. , Marqués J.-L. , Vaßen R. , Stöver D.
Published: September 2022

Wear at the electrode surfaces of a one-cathode plasma torch changes the characteristic fluctuation pattern of the plasma jet. This affects the trajectory of the particles injected into the plasma jet in a non-controllable way, which degrades the reproducibility of the process. Time-based voltage measurements and Fourier analysis were carried out on a one-cathode F4 torch at different wear conditions to determine the evolution of wear-dependent characteristics. A significant correlation is observed between increasing torch wear and decreasing voltage roughness and high frequency noise. Furthermore, by means of particle diagnostic systems, the change in the particle velocity and temperature has been measured. The variations of the particle characteristics are significant and thus an influence on the sprayed coating microstructure is to be expected.
Non-Destructive Testing of Coatings by Surface Acoustic Waves
Authors: Berger L.-M. , Schneider D. , Großer T.
Published: September 2022

The steadily increasing requirements to the properties of thermal spray coatings have to lead to the development of new characterization tools, in particular for non-destructive testing. Laser acoustic surface waves relate to the most promising methods for cost-effective non-destructive testing. In this work seven HVOF-sprayed WC-based coatings were systematically studied by laser acoustic surface waves using the LAWave device. Due to short measurement and calculation times the coating can be easily multiply tested. Young`s modulus and densities of the coating were obtained by this method. The values of the Young's modulus were compared with those derived from a micro-indentation method using Vickers indents and were found to be in a good agreement. Moreover, Vickers hardness values of the coatings obtained by using different loads were compared and the phase composition was studied by X-ray diffraction. The coating porosity was determined by image analysis of optical micrographs of metallographic cross-sections. It is proposed that in the case of WC-based coatings changes in the theoretical density of the material composition due to phase transformations induced by the spray process (formation of W2C and solid solutions on their base) prevent a direct access to the porosity values.
Effect of Aluminum Additive on Friction and Wear Behaviour of Plasma Sprayed Ceramic Coatings
Authors: Tao S.Y. , Yin Z.J. , Zhou X.M. , Ding C.X.
Published: September 2022

In this study, three different types of Al2O3 coatings were prepared by atmospheric plasma spraying. Some physical properties of these coatings were measured. Microstructure and wear morphologies of coatings were investigated by scanning electron microscopy (SEM) and optical microscopy (OM). The tribological behaviour of various coatings against stainless steel using a block-on-ring configuration were investigated in terms of the microstructure, physical properties especially the thermal diffusivity of coatings and the evaluation of tribological heat. Results revealed that the wear resistance of coatings used in this work showed a high dependence on their thermal diffusivity rather than other properties such as porosity, microhardness and bond strength: the higher the thermal diffusivity of a ceramic coating, the better is its wear resistance.
Characterization of Coatings Sprayed with AMT200 HVOF System
Authors: Zhang G. , Liao H. , Coddet C. , Malavolta C. , Hansz B. , Keller S.
Published: September 2022

The development of High Velocity Oxy-Fuel (HVOF) process shows a clear trend toward the design of new gun in which high pressure and large power are expected in order to obtain a stable flame and a high powder feed rate for industrial applications. In this work, a new HVOF gun, AMT-200, was used to prepare NiCrAlY and WC-Co-Cr coatings. To optimise the spraying parameters, i.e., flux rates of oxygen and fuel gas and spraying distance, the on line control system AMT Spraying Xplorer was used. The results show that the spraying parameters play significant roles on the properties of NiCrAlY coatings. Employing optimized parameters, a dense NiCrAlY coating, with a high coating/substrate bonding strength and low oxygen content, could be obtained by this system. Moreover, thermal treatment could reduce significantly the coating porosity and increase greatly coating/substrate bonding strength. The preliminary tests on WC-Co-Cr coating indicate that dense cermet based coatings could be deposited with this system.
Testing Method for Heat Resistance Under Temperature Gradient
Authors: Takagi K. , Kawasaki A. , Itoh Y. , Harada Y. , Ono F.
Published: September 2022

“Testing Method for Heat Resistance under Temperature Gradient” is a Japanese Industrial Standard (JIS) newly established by the Minister of Economy, Trade and Industry, after deliberations by the Japanese Industrial Standards Committee, in accordance with the Industrial Standardization Law. This standard specified the testing method for heat resistance under temperature gradient of materials and coated members of equipment exposed to high temperature, such as aircraft engines, gas turbines, reciprocating engines, accelerators, power switchgears etc. Three kinds of testing method, such as burner heating test, arc heating test and various beam heating tests are involved.
Investigation on HVOF-Technique for Fabrication of SOFCs (Solid Oxide Fuel Cells) Electrolyte Layers
Authors: Gadow R. , Killinger A. , Candel Ruiz A. , Weckmann H. , Öllinger A. , Patz O.
Published: September 2022

Thermal spray processes represent a cost effective and flexible method for the production of functional coatings by using metallurgical, ceramic and cermet materials. Due to the high kinetic energy of the impinging particles, the HVOF (High Velocity Oxygen Fuel) technique is able to produce extremely dense coatings with very low porosity. In this study, several yttria stabilized zirconia (YSZ) powders have been sprayed by HVOF for the fabrication of electrolyte layers for SOFCs (Solid Oxide Fuel Cells) applications. Coatings were characterized regarding their porosity, leak tightness and electrochemical properties. Results were compared to VPS sprayed coatings. The electrochemical behavior of the cells sprayed with the optimized set of parameters was determined applying U(i)-characteristics and impedance spectroscopy. With a destination thickness of about 40 µm, competitive leak tightness of the electrolyte and performance of the cells could be established.
Cladding of Aluminum Substrates with Nano Crystalline Solidifying Wear Resistant Iron-Based Materials
Authors: Wilden J. , Bergmann J.P. , Reich S. , Schlichting S. , Schnick Th.
Published: September 2022

Since many years, aluminum alloys are established as lightweight construction materials. To reach a partial wear protection for aluminum components in conjunction with seal faces, inlays, made of wear resistant materials, are commonly used. Problems concerning this approach are the necessary space and the endurance strength of the inlay - part joint. In the following paper an alternative for the replacement of the inlays by cladding with an innovative and easy to handle short arc technology will be discussed. This technology offers the potential to control the energy input into the substrate and so the formation of brittle intermetallic phases in the aluminum-steel interface as well as the thermal stresses. The usage of new nano crystalline solidifying wear resistant iron-based feedstock materials with advantageous physical and mechanical properties enables further applications beside the wear protection of surfaces, for example as metallic heat insulation layer with a low heat conductivity, close to the values of ceramics.
Dye Sensitized Solar Cells Using Titanium Oxide Photo Voltaic Devices Fabricated by Different Thermal Plasma Processes
Authors: Ando Y. , Tobe S. , Tahara H.
Published: September 2022

Since Dye sensitized solar cell (DSC) is a solar cell which uses anatase film as photo voltaic device, production cost of DSC can be very low in comparison with that of silicon solar cell. Besides, according to some theoretical discussion on DSC, the electric power conversion efficiency can be raised to 30%. Therefore, DSC will be mainly used in future. In this study, in order to develop a low cost fabrication process for photo voltaic device of DSC, photo-catalytic titanium oxide film depositions were carried out by thermal plasma CVD (TPCVD) and thermal spraying. As working gas for plasma jet, and substrate, Ar gas and 20mm×40mm×1mm copper plate were used. Feedstock materials were titanium tetra butoxide in TPCVD and rutile powder in thermal spraying. In the DSCs using these films, cathodes (titanium oxide coated electrodes) were located beneath the transparent anodes. Consequently, in the case of TPCVD, anatase dominant film could be deposited and the DSC using this TPCVD film could generate 50 mV in electro motive force. Furthermore, even in case of thermal spraying, though rutile powder was used, photo-catalytic coating (anatase and rutile mixture coating) could be obtained by cooling substrate during coating and post heat treatment. It was confirmed that the electromotive force of the DSC using this thermal spray coating was almost the same as that of the DSC using the TPCVD film. From these results, these thermal plasma processes was found to have high potential for DSC fabrication.
Production and Characterization of Metastable ZrO2-Al2O3 Coatings Obtained by APS + Quench
Authors: Dosta S. , Cano I.G. , Miguel J.R. , Guilemany J.M.
Published: September 2022

Producing nanostructured materials through metastable phases is an interesting novel route in the field of ceramic materials. Due to their small grain size and uniform structure, these nanostructured bulk materials exhibit very interesting properties. Metastable coatings can be produced starting from microstructured powders through atmospheric plasma spray (APS) technique, followed by a quenching route. The initial powders are melted during the spraying and deposited over a substrate that is quenched with liquid nitrogen (LIN) feeders, producing metastable coatings. The thermal sprayed coatings have been characterized using XRD, SEM, FESEM and EDS in the Thermal Spray Centre (CPT) of the University of Barcelona. The properties of such coatings have been also studied obtaining promising results.
Laser Cladding: A New Technology for Corrosion and Erosion Protection of Boiler Tubes
Authors: Fantini V.
Published: September 2022

In Municipal Waste Incinerators (MWI) considerable corrosion problems of critical components, such as superheater or boiler tubes, are always reported. Especially in modern WTE plants the need of efficiency increase requires operation at higher temperatures, which in turn enhances the corrosion rates. Laser cladding technology was successfully used for the production of anticorrosion and resistant-to-erosion coatings on tubes of superheaters and boilers. Compared to protective coatings produced by flame spraying devices, laser cladding is virtually porosity free and metallurgically bonded to the substrate, ensuring the possibility of bending the clad tubes without any damage such as cracks or spalling. This ability to sustain high deformation rate is absolutely necessary for the construction of superheaters serpentines, opening the door to the production of a whole superheaters assembly protected by a laser cladding. Due to the very low thermal load of the process, if compared to usual GMAW welding, laser cladding allows producing coatings with very low iron content (1-3%) even in a single pass with thickness lying in the range 0.7 -1.0 mm. Therefore laser technology enables to produce high quality coatings with a considerable saving in feeding materials, when compared to conventional GMAW welding where 2.5 - 3 mm thick cladding is necessary to have the same iron content of a single pass laser cladding. In this paper are presented advantages of this new technology and CESI RICERCA facilities for industrial production of MWI superheater and boiler clad tubes by its new automatic diode laser workstation. Results of a campaign of in-plant tests and performances obtained in operation by several laser clad components installed in European MWI plants are also presented.
Formation of WC/12%Co Coatings by High Velocity Oxygen-Fuel Spraying with High Wear Resistance and Lower Surface Roughness
Authors: Sato K. , Ibe H. , Mizuno H. , Kitamura J.
Published: September 2022

The structural and mechanical properties, in terms of surface roughness, hardness and wear resistance, of WC/12wt%Co coatings are investigated as a function of powder properties, such as powder size and WC grain size, as well as high velocity oxygen-fuel (HVOF) spray conditions. It has been found that the WC/12wt%Co coatings with relatively smoother surface, about 2 µm in average surface roughness (Ra), retaining high wear resistance can be formed by optimizing the powder and spray parameters. Further, we have found that powder size can control the surface roughness over a wide range; from about 2 to 7 µm (about Δ5 µm) in Ra. On the other hand, Ra changed only about Δ1 µm or more when changing spray conditions, such as barrel length and spray distance.
Characterization of Nano-Structured WC-Co Deposited by Cold Spraying
Authors: Li C.-J. , Yang G.-J. , Li C.-X. , Wang Y.-Y. , Ma J. , Gao P.-H.
Published: September 2022

Nano-structured WC-Co coating was deposited by cold spraying using a nanostructured WC-12Co powder. The critical velocity for the particle to deposit was measured. The coating microstructure was characterized by X-ray diffraction analysis, scanning electron microscopy and transmission electron microscopy. The coating hardness was tested by using a Vickers hardness tester. The deposition behavior of single WC-Co particles was examined. WC particle size was also measured for comparison of deposit properties to that of sintered bulk. The result shows that the nanostructured WC-Co coating can be successfully deposited by cold spraying using nanostructured powders. The coating exhibited a dense microstructure with full retention of the original nanostructure in the powder to the coating. The test of microhardness of the coating yielded a value of over 1820 Hv0.3, which is comparable to that of sintered nanostructured WC-Co. The deposition behavior of WC-Co powders as superhard cermet materials in cold spraying and powder structure effects are discussed.
Development and Investigation of SiC-based Thermal Spray Powders with Alumina-Yttria Binder Matrix
Authors: Wielage B. , Grund T. , Nebelung M. , Thiele S. , Wank A. , Schwenk A.
Published: September 2022

The combination of excellent mechanical, thermal and chemical properties of silicon carbide (SiC) and titanium carbide (TiC) has made these materials very attractive both for structural ceramics applications and for thermal sprayed coatings. To suppress oxidation and to avoid the formation of silicides during spraying of SiC-based composites, feedstock spray powders have been developed containing 32 wt.-% of an alumina-yttrium ceramic binder matrix. The spray powders are prepared by spray-drying and sintering (a&s). Also, TiC-based composite spray powders showing the same matrix material and content have been developed and produced. Thermal spray processing of the described powders by atmospheric plasma spraying (APS) using an F6 APS torch and high velocity oxygen fuel spraying (HVOF) with the Top Gun G acetylene torch is carried out. Both the produced coatings and feedstock powder are characterized by optical microscopy, X-ray diffractometry (XRD) and scanning electron microscopy (SEM) including energy dispersive X-ray analyses (EDXS).
Semantic Technology as a Core Business Activity for Thermal Sprayers
Authors: Chandler P.
Published: September 2022

Globalisation is moving business’s emphasis away from basic technologies towards “information and knowledge”. Indeed, knowledge based processes and products have become a new paradigm. As such, the management (control and retrieval) and use of data has become a central activity both for companies themselves and, increasingly, within wider supply chains. Adding “value” to data and creating “knowledge” will be a key element of future business growth. Handling and, more importantly, exploiting the current explosion of electronic information represents a real challenge to companies. However, the emergence of new, semantic tools which can “intelligently” interrogate and manipulate data could turn a potential problem into an opportunity.