bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparative Analysis of Tribological Properties of Cermet Detonation Coatings
Authors: Ulianitsky V. , Shtertser A. , Zlobin S. , Smurov I.
Published: September 2022

Properties of detonation coatings from composite powders based on carbides are studied. The main focus is on tungsten carbide. Powders with carbide inclusions of different size ranging from a ten of microns down to the submicron level are analysed. Composites with cobalt binder content from 12 to 30 % and composite binders with chromium and nickel additions are studied. A comparative analysis between composites with chrome carbide and the complex titan-chrome carbide produced by self-propagating high–temperature synthesis is done. Powders are sprayed with a new generation detonation gun “Dragon” designed at Lavrentyev Institute of Hydrodynamics SB RAS. The apparatus is characterized by a high-precision gas supply system and a dosed localized powder feeding system. Computer control provides a flexible programmed readjustment of the detonation gases energy impact on powder particles thus allowing selecting the optimal for each material spraying parameters to form high-quality cermet composite coatings. Physical properties and functional performance of the obtained coatings are studied. Microstructure and microhardness analyses, adhesion/cohesion, abrasion, erosion and friction wear tests of the coatings are performed. It is found that the studied materials do not exhibit overwhelming advantages in performance compared with one another. Fore example, though composites with a great content of binder has a relatively low wear resistance, they exhibits the highest adhesion to the substrate while composites with titan-chrome carbide compared to tungsten carbide-based composites have higher dry friction and lower lubricated friction.
A New Way in HVOF Technology—CFD Optimized TopGun AirJet for Powder and Wire
Authors: Wielage B. , Rupprecht C. , Paczkowski G. , Menzen R. , Weissenfels G. , Bernhardt H.-U. , Runkel M.
Published: September 2022

The thermal spray industry requires universal and economical HVOF systems for the production of high-quality coatings with high deposition efficiencies. In the last years classic HVOF guns have been adapted insufficiently to these requirements. This paper shows how modern numeric simulation and new inventions in gas safety engineering enable the development of a spray system for powder and wire feedstock that is optimized especially for the needs of the market. The new IBEDA TopGunAirJet is equipped with an air-cooled ‘de Laval’-like nozzle. The optimized expansion of the gas leads to high gas and particle velocities as well as to moderate flame and particle temperatures. Advantages of the TopGunAirJet are the achievable high coating quality, the low energy consumption (propane, ethene), the utilization of powder or wire and the efficient air cooling of the thermally loaded nozzle parts. Additionally, as a result of the axial powder injection, the free jet divergence and the nozzle wear are minimized. By varying the powder gas flow, the dwell time of the particles inside the flame can be influenced in order to avoid fusing of hard phases. As an example, WC-Co 88-12 coatings are presented and compared to coatings sprayed with a standard HVOF system of the 3rd generation. Different 316L coatings are produced and tested in comparison to standard HVCW coatings to show the workability of solid and cored wires. Finally, extensive LDA measurements are used for in-flight particle analysis, and investigations concerning the achievable deposition efficiencies are carried out.
Homogenization of Coating Properties in Atmospheric Plasma Spraying – Technical Objectives and First Results of a DFG Funded Research Group
Authors: Bach F.-W. , Möhwald K. , Hartz K. , Bobzin K. , Bagcivan N. , Petkovic I. , Schein J. , Forster G. , Zimmermann S.
Published: September 2022

The disadvantage of plasma torches using conventional single cathode techniques is the occurrence of azimuthal and axial instabilities inside the plasma torch. This causes electrical power fluctuations which result in inhomogeneities of the plasma jet enthalpy and with that an uneven plasma particle interaction. Hence, variations in particle properties occur and consequently an uneven coating quality is produced. Using the triple-cathode technique these electrical power fluctuations were successfully reduced, resulting in a stationary plasma flow. Thus this technique appears to offer the potential to homogenize coating properties. Similar results have been shown for plasma torches with triple anode arrangements. The goal of this research group is to homogenize properties of plasma sprayed coatings using of 3-cathode and 3-anode technologies based on numerical simulations. The approach used is to subdivide the complete APS process into the areas plasma torch, free jet as well as coating formation and characteristics. By simulation of the individual areas and combination with experimental results the corresponding process parameters will be obtained for the desired coating properties.
Gaseous Pulse Detonation Spraying: Current Status, Challenges, and Future Perspective
Authors: Kharlamov Y.A.
Published: September 2022

The paper is devoted to gaseous detonation spraying and presents the state of current knowledge, as well as the following research and development needs: gaseous detonation as spraying heat source; operation cycle of detonation guns and its possible versions; operating frequency; impulse jet formation; basic detonation guns design concepts, as fuel and oxidant types, features of barrel design, predetonation distance control, valved and valveless detonation guns concepts, etc.; gas dynamic characteristics of detonation spraying.
Atmospheric IC-Plasma Spraying of Coatings – A Too Little Attended Alternative?
Authors: Dzur B.
Published: September 2022

Although the history of using the thermal inductively coupled RF-plasma (ICP) for spraying processes has been started in the early sixties, up to now all but no industrial applications are known. ICP-spraying of coatings has been investigated in various labs for interesting applications like coatings for medical implants and electrodes for SOFC´s. All the processes are VPS-applications. This on one hand of course is caused by the oxygen affinity of the used materials, on the other hand the current view in thermal spraying is, that very dense and excellent adherent coatings can be sprayed only by increasing the particles velocity. In contrast to this mind this contribution will try to show, that also under atmospheric and low vacuum conditions, i.e. using a laminar flowing plasma with nearly no acceleration of the axially injected particles, it becomes possible to spray coatings with comparable values of porosity and bond strength but special features that can not be produced with common technologies. This can be explained by the changed condition of heating, deformation and cooling down of the considerably larger particles. Actual examples are given for various spraying materials like ceramics and hard magnetic materials.
Thermal Spray Fabrication of Cermet-Supported Tubular Solid Oxide Fuel Cells
Authors: Li C.-J. , Li C.-X. , Yang G.-J.
Published: September 2022

Ni-Al2O3 cermet supported tubular solid oxide fuel cell (SOFC) has been fabricated by thermal spraying processes to aim at reducing fabrication cost. Ni-Al2O3 cermet support was deposited by flame spraying and the anode, electrolyte and cathode were deposited by plasma spraying on the support tube. YSZ-Ni was used as the anode and lanthanum strontium manganate was used as the cathode. Plasma-sprayed ScSZ and YSZ deposits, after post-spray densification treatment by nitrate solution, were used as the electrolyte at thicknesses of 40 µm to 100 µm to assemble SOFC single test cell. It was found that the output power density was increased with the decrease of electrolyte thickness. The cells assembled with ScSZ exhibited a higher powder density than YSZ electrolyte. The maximum output powder density reached 0.89 W/cm2 with ScSZ electrolyte of 40 µm thick at 1000°C in comparison of 0.76 W/cm2 obtained with YSZ electrolyte. The results showed that the tubular SOFC fabricated fully by thermal spray processes exhibits excellent performance.
Effect of Substrate and Cathode Parameters on the Properties of Suspension Plasma Sprayed Solid Oxide Fuel Cell Electrolytes
Authors: Waldbillig D. , Tang Z. , Burgess A. , Kesler O.
Published: September 2022

An axial injection suspension plasma spray system has been used to produce layers of fully stabilized yttria-stabilized zirconia (YSZ) that could be used as solid oxide fuel cell (SOFC) electrolytes. Suspension plasma spraying is a promising technique for the rapid production of coatings with fine microstructures and controlled porosity without requiring a post-deposition heat treatment. This new manufacturing technique to produce SOFC active layers requires the build up of a number of different plasma sprayed SOFC functional layers (cathode, electrolyte and anode) sequentially on top of each other. To understand the influence of the substrate and previously-deposited coating layers on subsequent coating layer properties, YSZ layers were deposited on top of plasma sprayed composite lanthanum strontium manganite (LSM)/YSZ cathode layers that were first deposited on porous ferritic stainless steel substrates. Three layer half cells consisting of the porous steel substrate, composite cathode, and suspension plasma sprayed electrolyte layer were then characterized. A systematic study was performed in order to investigate the effect of parameters such as substrate and cathode layer roughness, substrate surface pore size, and cathode microstructure and thickness on electrolyte deposition efficiency, cathode and electrolyte permeability, and layer microstructure.
Automated Substrate Cooling System for HVOF Coating Operations
Authors: Zurecki Z. , Ghosh R. , Mebrahtu T. , Thayer M.J. , Stringer S.R.
Published: September 2022

High production rate and feed powder efficiency are critical in the HVOF hardfacing of aircraft landing gear, turbine, and actuator components traditionally electroplated with carcinogenic hard chromium. Desired improvements are hindered by rapid heat build-up in substrate component and thermal expansion mismatch between the carbide coating and steel, titanium or aluminum substrate. A new, cryogenic nitrogen gas (-195°C) cooling system has been developed which limits the thermal expansion and substrate softening problems, and enables a non-stop, gun-on-target spraying. Fully automated, the operation of the new AP LIN-Cooling System is based on thermal imaging of the entire substrate and multi-zone cooling with novel, cryofluidic nozzles. Thermal logs and images of components processed are saved by the system for quality auditing purposes. This paper presents results of industrial tests of the system during WC-10Co4Cr coating of Boeing 737 landing gear, demonstrating a 50% reduction in spraying time, corresponding reductions in the consumption of powder and HVOF gases, and additional labor savings due to the use of flexible masking, unfeasible with the traditional cooling methods. Analysis of residual stresses, structures and properties of the coating and AISI 4340 steel substrate shows that the cryogenic nitrogen cooling results in high-quality products.
A Life Cycle Comparison of Hard Chrome and Thermal Sprayed Coatings: A Case Example of Aircraft Landing Gears
Authors: Krishnan N. , Vardelle A. , Legoux J.G.
Published: September 2022

Electroplated hard chromium (EHC) is widely coated onto parts to provide resistance to corrosion, wear and impact. The electroplating process, however, has significant health and environmental impacts. Air emissions during the electroplating process contain hexavalent chromium (Cr+6) - a known carcinogen, furthermore the process is energy intensive and generates hazardous waste. Because of health and environmental issues related to hard chromium plating, there have been several efforts to find alternatives. One of the more efficient technologies among the substitutes is High Velocity Oxy-Fuel (HVOF) thermal spraying. This technology is commercially available today, with a major commercial opportunity in aerospace applications. In this paper, we therefore compare the life cycle environmental footprints of hard chromium and HVOF coatings for aircraft landing gear. Our results indicate that from an environmental perspective, HVOF spraying is generally preferable to EHC plating, with 5-10 times lower human health impacts and 30-50 times lower ecosystem impacts. However, in terms of resource consumption, the processes have similar impact profiles with EHC plating having a potential for lower impact on resources in areas with a significant share of renewable electricity.
HVOF-Sprayed WC-(W,Cr)2C-Ni Coatings and their Properties
Authors: Berger L.-M. , Saaro S. , Jordan C. , Naumann T. , Kašparova M. , Zahálka F.
Published: September 2022

The composition WC-(W, Cr)2C-Ni is one of the standard hardmetal compositions used for the preparation of thermally sprayed coatings by high velocity oxy-fuel (HVOF) spraying. Surprisingly, this composition has been poorly investigated in the past. Frequent use of the commercial designations WC-“CrC”-Ni, WC-Cr3C2-Ni, and WC-NiCr indicate the insufficient knowledge about the phase compositions of the powders and coatings. In this paper, the processability of five commercial feedstock powders was studied. These feedstock powders were of different origin and were sprayed with two different liquid-fueled HVOF systems (K2 and JP-5000). The microstructures and phase compositions of the powders and the coatings were studied. Focus was on the appearance, composition, and distribution of the (W, Cr)2C phase, which is either formed or changes its Cr/W ratio during the spray process. The composition of the (W, Cr)2C phase was estimated from the lattice parameters. Hardness, density, and Young’s modulus were determined for the coatings. Additionally, the abrasion wear resistance of the coatings was studied. Unlike WC-Co and Cr3C2-NiCr, WC-(W, Cr)2C-Ni is not a simple binary hard phase-binder metal composite. The excellent properties of this composition, for instance, its oxidation and corrosion resistance, will surely attract more attention to this composition than it has in the past.
Influence of the Spray Angle on Characteristics for Atmospheric Plasma Sprayed Hard Material Based Coatings
Authors: Tillmann W. , Vogli E. , Krebs B.
Published: September 2022

This paper presents an investigation of the influence of the spray angle on thermally sprayed coatings. Spray beads were manufactured with different spray angles between 90° and 20° by means of atmospheric plasma spraying (APS) on heat-treated mild steel (1.0503). WC-12Co and Cr3C2-10(Ni20Cr) powders were employed as feedstock materials. The spray beads were characterized by a Gaussian fit. This opens the opportunity to analyse the influence of the spray angle on coating properties. Furthermore, metallographic studies of the surface roughness, the porosity, the hardness and the morphology were carried out and the deposition efficiency as well as the tensile strength were measured. The thermally sprayed coatings show a clear dependence on the spray angle. A decrease in spray angle changes the thickness, the width and the form of the spray beads. The coatings become rougher and their quality decreases. In addition, the spray process becomes inefficient as the deposition efficiency declines. Especially, below 30° for Cr3C2-10(Ni20Cr) and below 50° for WC-12Co a significant change in microstructure was observed.
Advanced Knowledge System for Coatings and the Gas Turbine MRO Industry
Authors: Chandler P.E. , Hall W. , Shadbolt N.R. , Alani H. , Szomszo M.
Published: September 2022

The growth of data generated within thermal spraying is, for many, a daunting business. Yet, this growing resource represents a largely untapped and potentially valuable asset capable of providing “knowledge” rather than just “information”. Many companies already use a range of Web based tools. However, the Web itself is changing and the vision for the future, the “Semantic Web”, is set to revolutionise how business will be done. One important aspect of this Web “future” is that web pages will be greatly enriched and data will have additional information (tags) which help to describe it and more significantly, put the data into a context. This will enable machine readability and the use of query languages to ask direct questions. Following on from ideas introduced at ITSC 2007, a proof of concept demonstrator has been built for thermal spray coatings used in the Maintenance Repair and Overhaul (MRO) of gas turbines. A system has been built which stores and manipulates a range of data including; aircraft deliveries, RSS feeds of aircraft sales, engine types, MRO business details, thermal spray coatings and market dynamics. This paper presents the development of this system and discusses its future potential.
Development of Oxide Dispersion Strengthened MCrAlY Coatings
Authors: Bobzin K. , Ernst F. , Richardt K. , Brühl M.
Published: September 2022

MCrAlY materials are widely used as bond coats for thermal barrier coatings on turbine blades. The aim of this work is to improve mechanical properties and wear resistance of thermal sprayed NiCoCrAlY-coatings by strengthening the coating with hard phase particles. In order to retain the effect of the dispersion reinforcement at high temperatures, the use of temperature-stable oxide hard phases such as ZrO2 is necessary. To realise this new material structure, the high energy ball milling process is applied and analysed. With this process it is possible to achieve a homogeneous distribution of the oxide hard phases in the NiCoCrAlY matrix. The mixture ratio between NiCoCrAlY and ZrO2 was varied between 5 wt-% and 10 wt-% ZrO2. The influences of the milling time of the high energy ball milling process on the distribution of the hard phases in the metal matrix were analysed. After spraying with a HVOF system the mechanical properties of the coatings are measured and compared with conventional NiCoCrAlY coatings.
Wire Arc Spraying Technology for Spraying Particle Reinforced Coatings
Authors: Wilden J. , Jahn S. , Reich S. , Fischer G. , Knapp S. , van Rodijnen F.
Published: September 2022

The introduction of new wire arc spraying equipment with chopped power supplies offers many possibilities to improve the wire arc spraying process. These power sources provide higher process stability even at reduced voltages. On the one hand conventional applications can be enhanced and on the other hand new processes can be developed. Due to the high process stability the introduction of additional particles into the atomizing gas stream is possible. This can be applied to produce coatings with a high wear resistance as well as a high surface roughness. A combined technology of particle injection and the productive wire arc spraying process enables the economic production of innovative functional surfaces. In the last years ITSC, the injection of corundum particles had been presented. In this paper further strategies for inserting particles into the gas stream and experimental results are shown for iron based coatings. For the reinforcement different carbides were injected into the atomizing gas stream.
Newest Light Weight Closed-Loop Arc Spray Gun
Authors: van Wonderen M. , Sedov V. , MacMillan I.
Published: September 2022

Within the Aircraft MRO (Maintenance, Repair and Overhaul) business KLM Royal Dutch Airlines Engineering & Maintenance Division has been involved with Thermal Spraying since the late 60’s. The latest procurement on thermal spraying is the state of the art light weight electric arc spray gun (the EM-14) for the closed-loop electric arc spray system of Praxair TAFA called the CoArc. With this new piece of equipment KLM is up-to-date in the high-tech approach of applying thermal spray coatings on aircraft engines with a electrical twin-wire arc spray system. Close teamwork between an end-user in aircraft industry (KLM) and a thermal spray supplier (Praxair) resulted in a new state of the art arc spray gun. This paper shows the first spray results with the EM-14 gun.
Corrosion of Alumina-Based Coatings
Authors: Stahr C.C. , Berger L.-M. , Herrmann M. , Deska D.
Published: September 2022

Corrosion protection has long been a challenge to thermally sprayed coatings. Alumina is known for its good corrosion properties, although especially thermally sprayed alumina-based coatings corrode if exposed to certain environments. The coating therefore becomes the limiting part for the component lifetime. Besides the corrosion of the coatings themselves, corrosion of the substrate can result from the existing porosity in the coatings. This work shows the influence of corrosion on alumina-based coatings as a function of the TiO2 content and the coating process used. The effects of corrosion are quantified to enable lifetime prediction and tailoring of protective coatings. The coatings were analyzed using electrochemical methods and were exposed for long periods to acids and bases at 85 °C. Corrosion properties of the coatings were compared with those of bulk parts, prepared by hot-pressing. An electrochemical method was developed to estimate interconnected of porosity as an alternative to long-term corrosion experiments.
Effect of Al on the Performance of Ni Based PTA Coatings
Authors: Cangue F. , D'Oliveira A.
Published: September 2022

Degradation of components that operate under elevated temperature and carburizing environments involves the diffusion of C and the precipitation of carbides. Industries have been seeking for materials that can withstand these service conditions. The present work aimed to develop coatings to address this challenge through the enrichment of a Ni based alloy with Al. An atomized Ni alloy without Al and different powder mixtures with 15 and 30wt%Al were deposited by PTA on a carbon steel. Coatings were analyzed in the as deposited condition and after temperature exposure in an air furnace and pack cementation tests at 650º and 850ºC. Vickers microhardness profiles under a 500gf load, X-ray diffraction, optical and scanning electronic microscopy were done Results revealed that the presence of Al lead to the development of a complex intermetallic phases which were associated with the enhanced metallurgical stability of the coatings under the tested temperatures. The superior performance of the coatings deposited with the powder mixture containing 30wt%Al after pack cementation was associated with the development of the NiAl intermetallic phase and of the oxide layer Al2O3 that stabilized the microstructure at the tested temperatures and reduced the diffusion of C.
Degradation Behavior of HVOF Sprayed Ni-Based Coatings on Superalloy in 40%Na2SO4-60%V2O5 Environment at 900°C
Authors: Mahesh R.A. , Kamal S. , Jayaganthan R. , Prakash S. , Modi A.
Published: September 2022

High velocity oxy fuel thermal spray (HVOF) processing is one of the proven thermal spray technologies to develop high temperature oxidation and corrosion resistant coatings for various high temperature applications such as thermal power plants, aero turbines, and energy conversion systems. In the present investigation Nickel based coatings, viz. Ni-5Al, NiCrAl, and NiCrAlY-0.4wt%CeO2 were sprayed on Fe based superalloy (Superfer 800) by HVOF spray process as the chosen superalloy finds extensive use steam boilers, furnace equipment, heat exchangers and piping in chemical industry The degradation behaviour of the coated superalloy was studied in the aggressive environment of 40%Na2SO4-60%V2O5 at 900°C, using thermogravimetric technique, to understand the protective nature of the coatings under cyclic conditions. The coatings were found to be effective in increasing the resistance to the degradation in the given environment. Among the coatings investigated, NiCrAlY-0.4wt%CeO2 coating was found to be more protective on the superalloy in the given aggressive environment. The corrosion mechanisms were elucidated through the X-ray diffraction (XRD) analysis and microstructural characterization techniques such as FE-SEM/EDAX analysis of the corroded products formed at high temperature.
Structure and Corrosion Behavior of 316L Stainless Steel Coatings Formed by HVAF Spraying
Authors: Zeng Z. , Sakoda N. , Tajiri T. , Kuroda S.
Published: September 2022

SUS316L coatings were sprayed by a high-velocity air fuel (HVAF) system to reduce oxidation and thereby improve the corrosion behavior of stainless coatings. The effects of powder feed rate and particle size on the microstructure, oxide amount and adhesion strength of the coatings were investigated. The corrosion resistance of the coatings was evaluated by conducting salt spray tests. The oxide amount in the coatings sprayed by the HVAF process is below 7 % and adhesion strength is below 34 MPa. In comparison with those of coatings sprayed by a high velocity oxygen fuel (HVOF) system, the oxide amount and adhesion strength are decreased because the particles heated below the melting point of the alloy and insufficient softened in HVAF process. The coatings deposited are original porous, and they become denser through the impinging effect caused by the following sprayed particles. With the increase of powder feed rate and particle size, there is a tendency of reduction in oxides, and an obvious decrease in adhesion strength. Corrosion resistance of the unsealed coatings is insufficient, and this becomes notable with increasing powder feed rate and particle size. The sealed HVAF coating sprayed with the largest particles shows the best corrosion resistance.
Innovation of Ultra-Fine Structured Alloy Coatings Having Superior Mechanical Properties and High Temperature Corrosion Resistance
Authors: Ma X.Q. , Gandy D.W. , Frederick G.J.
Published: September 2022

High temperature protection requires full coating density, high adhesion, minor oxide inclusions, and preferably fine grains, which is not achievable in most thermal spray processes. High velocity oxygen-fuel (HVOF) thermal spray process has been applied extensively for making such coatings with the highest density and adhesion strength, but the existence of not or partially melted particles are usually observed in HVOF-formed coatings because of relative low flame temperature and short particle resident time in the process. This work has investigated the development of an innovative HVOF process using a liquid-state suspension/slurry containing small alloy powders. The advantages of using small particles in a HVOF process include uniform coating, less defective microstructure, higher cohesion and adhesion, full density, lower internal stress and higher deposition efficiency. Process investigations have proven the benefits for making alloy coatings with full density and high bond strength attributing to increased melting of the small particles and the very high kinetic energy of particles striking on the substrate. High temperature oxidation and hot corrosion tests at 800°C have demonstrated that the alloy coatings made by the novel process have superior properties to conventional counterpart coatings in terms of oxidation rates and corrosion penetration depths.
Detonation Flame Sprayed Diamond-Bronze Coatings for Grinding Applications
Authors: Tillmann W. , Vogli E. , Nebel J.
Published: September 2022

Grinding applications for the machining of stone and concrete require composite tools where large diamonds are perfectly embedded into a metallic matrix. With the detonation flame spraying process it is possible to manufacture these superabrasive composites. Excellent embedment of the voluminous superabrasive particles into the matrix coating material can be realized in order to produce high quality composite layers for grinding applications of stone and concrete. In this paper different diamond sizes as well as different volume contents of diamond in matrix are compared. Especially, the influence of particle size on its implantation efficiency is investigated and the influence of process and substrate temperature is analyzed. The thermal sprayed grinding tools are evaluated in the sense of their morphology as well as their grinding abilities. Compared to sintered diamond-bronze samples the results of an adaptively designed grinding test for the machining of concrete are presented and analyzed.
Hot Corrosion and High Temperature Oxidation Performance of WC-Co Coatings by Detonation-Gun Spray on a Boiler Steel
Authors: Kaur M. , Singh H. , Prakash S.
Published: September 2022

Detonation-gun spray technology is a novel coating deposition process which is capable of achieving very high gas and particle velocities approaching 4-5 times the speed of sound. This process provides the possibility of producing high hardness coatings with significant adherence strength. In the present study, this technique has been used to deposit WC-Co coatings on T22 boiler steel. Investigations on the oxidation performance of detonation-sprayed WC-Co coatings in air and in molten salt Na2SO4-82Fe2(SO4)3 at 700°C under cyclic conditions have been carried out. The thermogravimetric technique was used to establish the kinetics of corrosion. The uncoated boiler steel suffered a catastrophic corrosion in the form of intense spalling of its oxide scale during air, as well as, molten salt induced oxidation. The WC-Co coated specimens showed lesser overall weight gains in comparison to their uncoated counterparts in both the environments. The oxidation kinetics for the coated specimens followed nearly the parabolic rate law. The overall weight gain has been found to be higher in the case of air oxidation as compared to that in salt environment for all the cases. Scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) techniques were used to analyse the corrosion products, which indicated the formation of W and O as main elements in the oxide scales of the coated steel in both the environments.
Characterisation of Ceramic Nanostructured Coatings Prepared by Thermal Spraying of Suspensions
Authors: Toma F.-L. , Berger L.-M. , Naumann T. , Langner S.
Published: September 2022

Functional characteristics of materials including the mechanical, electrical, environmental and tribological performance can be significantly improved using nanostructured feedstock. Over the last few years much research has been dedicated to the development of thermal spraying techniques with liquid precursors to prepare fine nanostructured coatings. In this work nanostructured ceramic coatings were prepared using the technique of suspension spraying. Titania and alumina powders with sizes in the nanometre to submicrometre range were used to prepare aqueous and alcoholic suspensions. Atmospheric plasma and high-velocity flame were employed as enthalpy sources. The morphologies and crystalline structures of the sprayed ceramics were mainly characterised by SEM and XRD. The aim of this work was to carry out a comparative study and to discuss the nanostructured ceramic coating microstructures as a function of the physicochemical properties of the feedstock suspensions and spraying parameters.
Microstructural and Tribological Aspects of Thermally Sprayed Ti-Cr-Si Coatings
Authors: Bandyopadhyay P.P. , Siegmann S. , Hadad M. , Jaeggi C.
Published: September 2022

This paper is a first report of thermally sprayed Ti 60 Cr 32 Si 8 (at-%) alloy coating. It has been reported previously that such an alloy assumes quasicrystallinity in presence of oxygen, when made to undergo rapid quenching. In these cases, either TiO or SiO2 is used as an ingredient in the alloy so that it can act as a source of oxygen. This paper describes an attempt to produce a quasicrystal by thermally spraying the alloy in air, i.e. in presence of oxygen, either by flame or atmospheric plasma spraying. The spray parameters for both the processes have been varied in the experiment in a wide range. A vacuum plasma sprayed coating served as the reference. This investigation includes a detailed study of the microstructure and phases by optical microscopy, Scanning Electron Microscopy (SEM), X–Ray diffractometry (XRD), microhardness and porosity. An estimate of the composition of the coating has been done using Glow Discharge Optical Emission Spectroscopy (GDOES). The parametric variations have been correlated with the coating microstructure. It has been found in the study that there is a likelihood of obtaining quasicrystalline phase by atmospheric plasma spraying of this alloy under favourable parametric conditions. The tribological properties of these coatings were studied using a ball on disc reciprocating tribometer.
Improving the Properties of HVOF- Sprayed Cr2O3 by Nanocomposite Powders
Authors: Varis T. , Knuuttila J. , Suhonen T. , Kanerva U. , Silvonen J. , Leivo J. , Turunen E.
Published: September 2022

Superior wear performance combined with excellent friction properties against metals makes chromium oxide (Cr2O3) an interesting coating material for many industrial applications. However, Cr2O3 is a challenging material for HVOF spraying due to its high melting temperature. Fracture toughness and lamella cohesion of a coating is limited and may be improved by using ceramic-ceramic –nanocomposite powders, which forms phases with improved properties. In this study Cr2O3-TiO2 systems were selected aiming to improve the toughness and lamella cohesion of coating without reducing the excellent wear properties.
The Effect of Undercooling on Solidification of YSZ Splats
Authors: Liu H. , Bussmann M. , Mostaghimi J.
Published: September 2022

The impact and solidification history of individual YSZ particles has been the subject of many experimental and theoretical studies. Yet it is customary to assume that solidification occurs at the equilibrium temperature. Furthermore, the diffusion of the solute (yttria) in the liquid phase during solidification of a splat has not been considered. Using our model, we study non-equilibrium effects during the rapid solidification of a molten YSZ particle, by solving the so-called hyperbolic equations for heat and mass transfer. The hyperbolic model predicts the interface undercooling (due to thermal and solutal effects) and velocity as a function of time, as well as the yttria redistribution within the solid phase. Results are then compared to corresponding ones that we obtained from a parabolic model, in order to assess the extent to which YSZ solidification is influenced by non-equilibrium effects. Results indicate that these effects are limited to the early part of the solidification process when undercooling is most significant. At this stage, the interface velocity is unsteady, and solute redistribution is most evident. As solidification decelerates, the non-equilibrium effects wane and solidification can then be properly modeled as an equilibrium process.
KINETIKS 4000—New Perspective with Cold Spraying
Authors: Hoell H. , Richter P.
Published: September 2022

Seven years after its introduction, the KINETIKS cold spray system from Cold Spray Technology GmbH is proving its reliability in various industrial applications. As pressure and temperature of the process gas are the primary parameters generating high particle velocities, the improvement respective development of the system family was focused on those. A further step of improving coating properties was the development of a powder preheating feature. Applications using this technology are now starting in a wide field from automotive up to aerospace products.
The LARGE Plasma Torch for Surface Chemistry Applications and CVD Processes: A Status Report
Authors: Zimmermann S. , Theophile E. , Landes K. , Schein J.
Published: September 2022

The LARGE is a new generation DC-plasma torch featuring an extended arc which is operated with a perpendicular gas flow to create a wide (up to 45 cm) plasma jet well suited for large area plasma processing. Using plasma diagnostic systems like high speed imaging, enthalpy probe, emission spectroscopy and tomography the LARGE produced plasma jet characteristics have been measured and sources of instability have been identified. With a simple model/simulation of the system LARGE III-150 and numerous experimental results, a new nozzle configuration and geometry (LARGE IV-150) has been designed, which produces a more homogenous plasma jet. These improvements enable the standard applications of the LARGE plasma torch (CVD coating process and surface activation process) to operate with higher efficiency.
Standard HVOF Process Compared to the HVOF Process for Internal Coating with Fine Powders
Authors: Matthaeus G. , Brandl W. , Secosan I.-F. , Marginean G. , Chirila V. , Ackermann D.
Published: September 2022

The main argument against the use of the internal HVOF process is the high thermal stress to which the substrates are subjected during the coating process. Traditional HVOF guns operate with a flame-stream energy level of 100–200 kW. Rendering HVOF technology usable for the application of internal coatings requires the reduction of the energy level of the flame stream to 20 kW, while safeguarding high particle velocity and sufficient temperature despite the reduced energy level. This requires an integrated process consisting of the HVOF gun, powder feeder, fuel control, and fine powder; the particle sizes of the powder are -25+5 µm, -15+5 µm, and -10+3 µm. Thermico’s ID CoolFlow M HVOF internal spraying gun comes equipped with a 5 mm acceleration nozzle and radial powder feed. It is suitable for internal diameters of 80 mm and above and eliminates the typical overheating problem. The ID CoolFlow M HVOF gun is suitable for internal coatings with Thermico 776 WC-CoCr powder, which comes in grain sizes of -15+5 µm and -30+15 µm. A comparison of both processes requires a number of specimen coatings with different parameters, which have to be compared to reference coatings. These reference coatings are produced using a Thermico CJS K4.2-776/G gun in combination with WC-CoCr 86 10 4 powder with a grain size of -30+15 µm, and a CJS K5.2-776 gun, using a finer powder with a grain size of -15+5 µm. The base material consists of heat-treated steel rings with a hardness of 45 HRC, an internal diameter of 130 mm and a wall thickness of 10 mm. Subsequently, the density, porosity, and structure of the specimen is assessed, and they are checked metallographically and with a scanning electron microscope, including EDX analysis. The specimen wear is monitored using the prototype of an internal coating test stand, developed by the Institute of Materials Science at the University of Applied Sciences Gelsenkirchen. It is essentially based on the same principle as the pin-on-disc tribometer for relative movements.
Effects of SO2 on Decay Durability of the 8YZ Coating Having Cermet Under Coat
Authors: Hamashima K. , Ishikawa Y.
Published: September 2022

In the production line of glass sheets, the 8%Y2O3-ZrO2 thermal spray coatings have put into practical uses. These coatings have under layers of metal Cr3C2-Ni/Cr cermets, to improve their bonding strength. In forming process of glass, non-oxygenated atmosphere containing sulfur dioxide is selected continually to improve the surface condition of glass sheets. Degradation and pealing of these coating have been observed frequently due to increasing of SO2 concentration. In this study, effects of SO2 on decay durability of the 8YZ coating having meta cermet under coat are examined. Interactions between the atmosphere and the top-layer or the under layer are clarified individually by some basic examinations and analysis. It is clarified that peeling of the bi-layer coating was occurred at the boundary region between top coat and under coat. By exposure test of the coated sample and some powders for N2-SO2 at 113K, following results obtained, 1) Some cracks and fine streaks are observed also, in the bottom region of the ZrO2 top layer after the exposure test of coated sample.. 2) Main components of these streaks are Cr and S. 3) Sulfur contents of Cr3C2 cermet and Cr3C2 are increased remarkably by the exposure test. 4) By the exposure, Cr3C2 can be converted into a Cr2O3 or a CrSx. due to reaction with SO2. As peeling of the coating on carrying roll is induced by oxidation and sulfurization of Cr3C2, the under layer of Cr3C2 cermet is not suitable especially as its under coat.
New Approach to the Problem of Cathode Wear in DC Arc Plasma Torches
Authors: Kavka T. , Arnold J. , Syed A. , Kupke T. , Schneider G.
Published: September 2022

High heat load on the surface of electrodes in DC arc plasma torches results in strong wear of electrodes. This takes place during the start up and shutting down procedure as well as during long-term running of the torch and results in arc voltage reduction. Such changes in voltage lead to a modification of the plasma jet properties and effect adversely reproducibility of deposits, which are undesirable for industrial applications. The present work offers a new approach to compensate cathode wear in DC arc gas stabilized plasma torches by using moveable anode. With this design of torch, the distance between the cathode tip and anode can be varied. Voltage fluctuation analysis show the possibility of a reasonable arc modification by approaching the nozzle to the cathode caused by a change of the flow field inside the arc chamber and the arc dynamics. Smaller cathode tip-nozzle distances result in higher arc voltage with reduced fluctuations accompanied by a positive effect on the plasma jet properties. Thus, the negative influence of cathode wear on generated plasma properties can be suppressed and the lifetime of the cathode can be extended by simple approaching the nozzle.
Microplasma Spraying of ZrO2 Coatings
Authors: Borisov Y. , Vojnarovich S. , Kislitsa A. , Borisova A. , Karpets M. , Tunik A.
Published: September 2022

Experiments for estimation of influence of microplasma parameters in ZrO2 – coating properties were performed with using of fractional-factorial design of the experiments. Regression equations for determination of the parameters significance and a selection of conditions for a deposition of coatings with specified properties were obtained. Possibility of deposition of ZrO2 - Y2O3 coating with tetragonal phase content 90 wt.% and more without cubic phase content by microplasma spraying was shown. Conditions of microplasma ZrO2-coating spraying with high content of tetragonal phase (93-95%) and porosity (1,3-1,8%) were established. Measurement of microplasma sprayed ZrO2-coating spots has established that the spots have an elliptical shape. Size of major and lateral axis (and also sprayed hill altitude) depends on spray parameters, mainly on amperage and spray distance. Microplasma sprayed ZrO2-coating can be applied for repair of small local defects on thermo barrier coatings and a deposition of zirconia electrolyte layer in solid oxide fuel cell.
Thin and Dense Yttria-Partially Stabilized Zirconia Electrolytes for IT-SOFC Manufactured by Suspension Plasma Spraying
Authors: Brousse E. , Montavon G. , Fauchais P. , Denoirjean A. , Rat V. , Coudert J.-F. , Ageorges H. , Wittman-Teneze K. , Caron N.
Published: September 2022

Intermediate temperature - solid oxy-fuel cells (IT-SOFCs) include in their design a solid electrolyte layer made of yttria-partially stabilized zirconia (Y-PSZ), an ionic conductor, through which oxygen ions diffuse. This layer needs to fulfill several characteristics among which a low leakage rate corresponding to a non-connected pore network and a low level of stacking defects such as microcracks or globular pores. Moreover, the thickness of this layer needs to be as low as possible (about 20 µm) in order to limit ohmic losses. Suspension plasma spraying (SPS) appears as a potential technological route to manufacture such layers structured at micrometric or sub-micrometric scales. In SPS, a stabilized suspension, made of a liquid, solid particles and a dispersant, is injected within the plasma flow. The liquid is very quickly fragmented and then vaporized and the individual particles, or the particle agglomerates, depending on the average size and morphology of the solid feedstock, are heated and simultaneously accelerated towards the substrate surface where they impact, spread and solidify, analogously in a first approximation to larger particles, to form a layer. The architecture of the layer is very closely related to plasma operating parameters (from which derive plasma flow stability), from the suspension characteristics, in particular the feedstock particle size distribution and from the suspension injection parameters. This work aims at presenting recent developments made to optimize some of these operating parameters to maximize the electrolyte layer characteristics.
Simulation of PYSZ-Particles Impact and Solidification in Atmospheric Plasma Spraying Coating Process
Authors: Bobzin K. , Bagcivan N. , Parkot D. , Petkovic I.
Published: September 2022

In this work numerical simulation results of the impact and solidification of molten PYSZ-particles on flat and rough substrate surfaces are presented. This investigation deals with the effect of the particle state prior impact, particle diameter and substrate roughness, on splats spreading behaviour and final morphology. The particles have a diameter range between 20 – 60 µm. Particle initial conditions prior to impact: speed, temperature and melting state, are taken from previous simulation modelling approaches of particle accelerating and heating. Simulations of fluid dynamics, heat transfer and solidification during the particle impact were performed using computational fluid dynamics. Tracing of free surfaces determinates volume of fluid method. Heat flux at the particle-substrate interface and temperature dependent liquid phase viscosity of PYSZ are studied and discussed. Simulated splat morphologies are compared with experimentally obtained splats.
How Long is the Way to Manufacture Solid Oxide Fuel Cells with Suspension Plasma Spraying?
Authors: Marchand O. , Rampon R. , Bertrand G. , Filiatre C.
Published: September 2022

In order to achieve SOFC at reduced costs, atmospheric plasma spraying (APS) could be an attractive technique. However, it is difficult to elaborate plasma sprayed coatings with the appropriate porosity for the electrodes and full density for the electrolyte. The spray process has been adapted by providing a suspension as feedstock material. SPS shows important advantages over APS, since it is now possible to spray finer powders to obtain either a thin (10 µm) dense layer as electrolyte or thick and finely structured porous layers for the electrodes. Nevertheless some questions still remain before considering manufacturing SOFC by SPS. The major one is to understand the influence of the suspension and the injection parameters on the drops formation and transformation in plasma before impinging upon the substrate as well as of the suspension characteristics (formulation, particle size and amount, viscosity, surface tension,...). To answer these questions, suspensions based on nickel oxide (NiO) and YSZ (yttria stabilized particles) have been prepared and functional layers have been produced by SPS. This work is compared with previous studies of YSZ sprayed suspensions.