bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling of Temperature and Residual Stress Fields Resulting from Impacting Process of a Molten Ni Particle Onto a Flat Substrate
Authors: Fan Q. , Wang L. , Wang F. , Wang Q.
Published: August 2022

Several effective numerical techniques, based on finite element analysis, have been developed and computed independently in this paper. Results are presented describing the impacting process, and the subsequent temperature and residual stress fields of a molten nickel particle impacting onto a flat substrate. Problems of this type, especially the prediction of the thermal residual stresses, are of major practical interest in thermal spray operations as a pioneering approach.
Modeling of Non-Equilibrium Supersonic Plasma Jets at Low Pressure
Authors: Blais A. , Jodoin B.
Published: August 2022

Low Pressure Plasma Spraying (LPPS) is a spraying technique developed in the 1970s that uses a converging-diverging nozzle (i.e. de Laval nozzle) inside a controlled atmosphere chamber. With such a set-up, it is possible to obtain a plasma jet in the supersonic flow regime, which may encounter several non-equilibrium phenomena. First, the operating pressures (i.e. chamber and torch exit) determine the aerodynamic state of the supersonic plasma jet. Operating at the nozzle design pressure insures aerodynamic equilibrium of the plasma jet while other chamber pressure brings a state of “aerodynamic non-equilibrium” for which expansion, compression and shock waves appear. Second, a low chamber pressure corresponds to a decrease in the number of collisions between electrons and heavy species (i.e. atoms and ions). This rarefaction of the plasma causes a state of “thermal non-equilibrium” for which there exist two different temperature distributions, Te and Th, respectively representing the electrons and the heavy species. Third, the high velocity of the plasma jet can bring a state of “chemical non-equilibrium” as the hydrodynamic time scale of the flow might become smaller than its chemical time scale. Hence it is a challenging task to model a phenomenon as complex as the low pressure supersonic plasma jet. The model developed in this work uses a commercial code in which recent advances in the field of plasma transport properties are implemented. It considers chemical non-equilibrium through the solution of the electrons conservation equation while the two temperature distributions each require the solution of an energy balance. The validation of the model is possible from recent measurements with a new method enhancing the capabilities of the enthalpy probe technique to supersonic jets in aerodynamic non-equilibrium. Abstract only; no full-text paper available.
Effect of the Surface Adsorbates on the Morphology of Plasma-Sprayed Splats
Authors: Li C.-J.
Published: August 2022

Copper splats are deposited on the flat stainless steel surface at the ambient and preheated conditions. The splashing occurs as the splats are deposited at an ambient atmosphere. The characteristics of the splashing occurring at different splat regions during spreading of the droplet are examined. The splashing can be classified into two types according to the splashing mechanisms. At the surrounding region of the splat larger than flattening ratio about 1.5 to 2, the radial splashing takes place by jetting-away of splat materials, which leads to the formation of a splat with a reduced diameter. At the central area of the reduced splat, the upward splashing occurs through the blowing up of the top surface layer which results from the high pressure of gas bubbles. At the preheated condition which can remove surface adsorbates, no evident splashing occurs under the normal spray conditions. Two types of splashing can be explained by the gases evolved through evaporation of the adsorbates resulting from the heating of the high temperature droplet. The spreading of the droplet involved in the wave urging flow is presented.
Influence of Powder Size Distribution and Heat Flux on Yttria Stabilised Coatings Elaborated by Liquid Suspension Injection in a DC Plasma Jet
Authors: Delbos C. , Fazilleau J. , Rat V. , Coudert J.F. , Fauchais P. , Bianchi L.
Published: August 2022

This paper is devoted to the study of coatings elaborated by a process permitting Air Plasma Spraying (A.P.S.) of finely structured ceramic coatings. This process mainly consists in injecting in a d.c. plasma jet, a ceramic suspension containing sub-micron ceramic particles. Coating characteristics are close to those observed in P.E.C.V.D., but with a faster elaboration rate (. 15 µm/m2.h) and, the possibility to produce a wide range of thicknesses (1 < e < 100 µm). This paper is aimed at producing the Yttria Stabilized Zirconia electrolyte (Y.S.Z.) of Solid Oxide Fuel Cells with a thickness of 5 to 30 µm. Previous studies of this process have been devoted to the influence of the spray parameters on the structure of Y.S.Z. splats collected and have allowed determining some well adapted working conditions. The new stage described in this paper, is related to the study of the growth of Yttria Stabilized Zirconia coatings and the influence of different parameters such as the ceramic particle size distributions contained in the suspension and the heat flux imposed to the surface of the substrate and successive passes during the coating elaboration.
Influence of the Voltage Modulation Frequency on Voltage Trace and Wire Arc Coatings Properties
Authors: Wilden J. , Bergmann J.P. , Jahn S. , Zimmermann S.
Published: August 2022

Due to the low running costs, high spray rates and efficiency wire arc spraying has become one of the most important thermal spray technology, especially as a tool for coating large areas with high deposition rates. The main applications are corrosion and wear protection of large structures, such as coating with zinc for anodic corrosion protection or with high-alloyed chromium steel for longer surface service time. Disadvantages of the arc spraying process are on the one hand that only electrically conductive materials can be processed and on the other hand the higher oxygen content within the coating compared to other thermal spray processes such as HVOF or APS. Innovative and flexible power supply systems were developed for arc welding technologies in the last decade. Today power supply devices with new features for arc wire spraying technologies are present at the market, too. Particle flow conditions as well as coating properties such as morphology and oxide content can be optimized by changing the current generator characteristic and modulating the energy input for example by pulsing the spray voltage up to 500 Hz. As a consequence of the power modulation the oxidation of the particles can be reduced by a lower heat input based on lower average spray voltage. Investigations in order to influence the droplet behaviour and the coating microstructure using dynamic current generators were performed for zinc, aluminium and copper. The effect of different modulation frequencies, pulse lengths and pulse voltages are presented.
Production of Samarium Doped-Ceria Plasma Sprayed Nano-Coatings Using an Internal Injection of a Suspension Containing Nanoparticles
Authors: Bouaricha S. , Oberste-Berghaus J. , Legoux J.-G. , Moreau C. , Ghosh D.
Published: August 2022

For solid fuel cell application, thin electrolyte is needed for novel materials that allow reducing their operating temperature. The influence of what called ‘the thermal management of the coating and the substrate’ is discussed. In particular, influence of substrate temperature and the nature of the substrate. It was found that adequate control of the coating and substrate temperature, together with an equivalent substrate/coating thermal expansion coefficients (CTE) are the key-factor to successfully obtain an SDC nanosized thin and dense coating free of cracks.
Deposition and Crystallization of Thermally Sprayed Amorphous Metallic Coatings
Authors: Rohan P. , Bouaricha S. , Legoux J.-G. , Moreau C. , Denoirjean A. , Vardelle A. , Le Niniven C.
Published: August 2022

The high cooling rate (>105 - 106 K/s) achieved in thermal spraying makes it possible to deposit coatings that exhibit a high content of amorphous phase and can be, afterwards, heated above the crystallization temperature to form nano-structured coatings. In this study, the relationship between the characteristics (temperature and velocity) of the sprayed particles at impact and degree of amorphization of the as-sprayed coatings was investigated for both plasma and wire-arc spraying techniques A Fe-Cr-based alloy that exhibits a high glass forming ability and is commercially available in the form of powder and wire with close chemical composition was used. The amorphous phase content was higher in plasma sprayed coatings than in wire arc sprayed ones and both types of coatings presented an increase in microhardness after heat treatment.
Plasma Spraying Behaviour and Properties of Aynthesized/Agglomerated Calcium/Magnesium Zirconates versus Lime/Magnesia Stabilized Zirconia
Authors: Písačka J. , Neufuss K. , Dubský J. , Kolman B. , Nohava J.
Published: August 2022

Calcium zirconate and magnesium zirconate prepared by synthesis and agglomeration were sprayed using a water stabilized plasma gun under varied spraying conditions. The same set of conditions was maintained during spraying of fused lime stabilized zirconia and magnesia stabilized zirconia. The intent of the study was to compare spraying behaviour and deposit properties of pairs of feedstock material that have just about the same chemical composition but differ considerably in the way of preparation. Free-flight particles as well as deposits were characterised by standard techniques, such as light microscopy, scanning electron microscopy with energy-dispersive spectroscopy, X-ray diffraction, differential thermal analysis, and pycnometry. The differences between relevant coatings were evaluated namely in terms of morphology, chemical and phase composition, density and porosity. Sources of observed differences are discussed.
Simultaneous Deposition of LSM and YSZ for SOFC Cathode Functional Layers by an APS Process
Authors: Hathiramani D. , Mobeen A. , Fischer W. , Lersch P. , Sebold D. , Vaßen R. , Stöver D. , Damani R.J.
Published: August 2022

In order to reduce the manufacturing costs of SOFC layer systems the atmospheric plasma-spray (APS) process is an attractive technique. Especially the deposition of high performance cathodes, which are essential for a high power density of the SOFC, are of major importance. The cathode functional layer (CFL) has to provide a high amount of triple-phases boundaries to allow the cathodic oxidation reaction. A typical materials mixture used for such a CFL is the perovskite (La0.65,Sr0.3)MnO3 (LSM) and the fully Y2O3-stabilized zirconia (YSZ). A sufficiently porous layer has to be formed where both components are mixed on a sub-micrometer scale. In addition to the tough challenge concerning the creation of a suitable microstructure of a CFL deposited by an APS process two additional difficulties have to be solved: i.) a decomposition of the perovskite and ii.) a chemical reaction between the LSM and the YSZ during the atmospheric plasma-spray process must be avoided. Suitable spray processing strategies were developed to overcome these problems. Cathode functional layers were produced by an atmospheric plasma-spray process using a multi-cathode Triplex-APS torch. Coatings are characterized by SEM, EDX, XRD and the porosity was determined by digital image analysis. SOFC layer systems with the new developed CFL are tested in single fuel cell tests.
Microstructures of Sprayed SiCp/Al Composites
Authors: Hu M. , Kang S. , Euh K.
Published: August 2022

The SiCp/Al composite was fabricated by a plasma spraying technique. By mean of OM SEM, TEM, XRD, SAED, EDS techniques, the microstructures for sprayed SiCp/Al composite were investigated in detail. The composite consisted of SiC and Al, along with single crystal Si and amorphorous Si, and tiny Al2O3. On the whole, the interfaces between SiC particle and Al bonded well, and tiny reactants like Al2O3 can be found near the interfaces. The mechanisms of chemical reactions were given during spraying. The nano-Al grains and nano-Al particles were seen in the sprayed composite. The formation mechanism of nano-Al grains and particles of SiCp/ Al composite was explained. Some interface relationships existed in the sprayed composite.
Cytocompatibility of Plasma Sprayed Bioceramic Coatings
Authors: Liu X. , Ding C.
Published: August 2022

In this paper, the Al2O3, ZrO2, TiO2, wollastonite, dicalcium silicate and their composite coatings were deposited onto Ti-6Al-4V substrates by an atmosphere plasma spray system. The rat osteoblasts were seeded onto the surface of the coatings to evaluate the growth behavior of osteoblasts on different implant materials. Scanning electron microscopy was used to observe the morphologies of the osteoblasts seeded on the surface of the coating for different time. The SEM observation indicated the osteoblasts are difficult to survive and proliferate on the Al2O3 coating surface. Osteoblasts can survive and proliferate slowly on the TiO2 and ZrO2 coating surface. Osteoblasts grow and proliferate very well on the surface of the wollastonite and dicalcium silicate coating, which present the two coatings possess excellent cytocompatibility. The addition of wollastonite and dicalcium silicate into ZrO2 and TiO2 can improve their cytocompatibility.
Plasma-Sprayed Particles : Impact Imaging and Flattening Particle Thermal History
Authors: Cedelle J. , Vardelle M. , Pateyron B. , Fauchais P. , Fukumoto M. , Ohgitani I.
Published: August 2022

In plasma spraying, the individual droplet behavior at impact is the fundamental element to understand the resulting coating microstructure. A new experimental set-up, developed in SPCTS laboratory (Limoges, F) with two fast shutter cameras (exposure time : 100 ns…1ms) allows visualisation at impact of a single particle plasma sprayed with a direct current (d.c) torch. A fast two color pyrometer enables to monitor particle temperature just prior to its impact, its flattening and its thermal history. Working in parallel with a free falling drop experiment, enables to obtain larger (about three orders of magnitude) time and dimension scale (realized in Advanced Joining Process Laboratory, Toyohashi, J). Each technique gives interesting and complementary results thanks to pyrometric signals and images. Results obtained with plasma sprayed particles allow studying the matter ejections generated on impact splashing .while both techniques allow following the flattening splashing. Calculation and comparison of quenching rates for millimetre sized drops on a stainless steel substrate give indications concerning the disk shaped splat formation.
HVOF Coating of Metallic Surfaces: Corrosion and Bending Characteristics of Coating
Authors: Fadhli H.Y. , Hashmi M.S.J. , Yilbas B.S.
Published: August 2022

HVOF coating finds wide applications in power generation industry to protect the hot path components from high temperatures gases. The mechanical properties influence the life span of such components. In the present study, mechanical properties of HVOF spray of Inconel-625 alloy onto stainless steel surface was examined. The three point bending tests are carried out to determine the load and the flexural displacements characteristics of the coated workpieces. The workpieces were subjected to aqueous static corrosion environment before and after the three point bending tests. The surface morphology and elemental composition of the coating after the bending tests are examined using SEM and EDS. It is found that the local corrosion site in the coating result in high stiffness of the coating and the cracks extending along the surface of the coating are resulted due to the shear on the surface of the coating.
Microstructure and Electrochemical Corrosion Behavior of the Zn-Al-Mg Coatings Produced by Cored Wires and High Velocity Arc Spraying
Authors: Xu B. , Zhu Z. , Yan Y.-L. , Ma S. , Chen Y.
Published: August 2022

Cored wires and high velocity arc spraying technique (HVAS) were used to produce high Mg content Zn-Al-Mg alloy coatings on low carbon steel substrates. The microstructures, mechanical properties and electrochemical corrosion behaviors of the Zn-Al-Mg coatings were investigated comparing with Zn and Zn-Al alloy coatings. And the electrochemical corrosion mechanisms of the coatings were discussed. The coatings show a typical aspect of layered thermal sprayed material structure. Chemical analysis of the coating indicated the composition to be Zn-14.9Al-5.9Mg-3.0O (wt.%). The main phases in the coatings are Zn, Mg2Zn11, Al12Mg17 and MgAl2O4, together with a little Al2O3 and ZnO. The Zn-Al-Mg coatings show higher electrochemical corrosion resistance in salt solution than Zn-Al coatings. The corrosion potential of Zn-Al and Zn-Al-Mg coatings decreased a little and then increased towards the noble potential. The analysis of XRD and Electrochemical impedance spectroscopy (EIS) shows that, with addition of Mg, the corrosion products can block off the pores in the Zn-Al-Mg coating, which is so-called self sealing, and thus prevent attack on the underlying steel substrate.
Adhesion Tests for Thermal Spray Coatings: Application Range of Tensile, Shear and Interfacial Indentation Methods
Authors: Hadad M. , Marot G. , Démarécaux Ph. , Lesage J. , Michler J. , Siegmann S.
Published: August 2022

Three adhesion measurement methods for thermal spray coatings, namely tensile adhesive strength (according to EN 582), interfacial indentation and in-plane tensile tests were investigated in terms of accuracy of the results and application potential for different coating / substrate conditions. Whereas the tensile adhesive strength test is widely used in industry, the other two methods are still under development in research laboratories and therefore only few experimental data on the accuracy of the methods and on the potential in an industrial context are available. For that reason, dissimilar coating-substrate combinations covering a wide range of types of thermal spray coating-substrate systems were tested using all these methods. Ceramic (Al2O3) and metallic (NiCr 80-20) coatings were thermally sprayed by flame spraying with two different thickness on titanium alloy and steel substrates exhibiting each two distinct roughness levels. The distinguished coating properties include the coating toughness, shear strength, interfacial toughness, and adhesive strength. Thermally sprayed coatings do not only show an interfacial complexity, but also the integrity of the interface of substrate and coating has to be considered, as well as porosity, cracks and residual stresses. In this paper, each measurement method was found to be related to certain type of loading conditions and fracture mode. The results of the different methods are compared and the limits of applicability of the different methods are discussed.
Properties of Composite Coatings Sprayed by the Low Temperature High Velocity Air Fuel Spray
Authors: Wang H. , Yuan X. , Hou G. , Zha B.
Published: August 2022

Based on the HVO-AF (High Velocity Oxygen-Air Fuel) thermal spray system, the Low Temperature High Velocity Air Fuel Spray was realized by additional liquid feed stocks. In this paper, the microstructure and characteristics of composite coatings sprayed by this spray technology were analyzed. Composite powders were composed at three mass fractions, Fe, 5mass%Fe -polymer, 15mass%Fe-polymer. In the experiments, the coatings properties were tested. The results indicated that all the coatings microstructure is dense and low porosity; metal particles were dispersed with polymer in the coatings. There were little oxide phase in the coatings. The coatings were closely combined with substrate, the reflectance coefficient of 5mass%Fe-polymer composite coatings is better than others, the reflectance coefficient curve of the coatings is 2~6dB at 2~18GHz.
Characterization of the Porosity of a TBC Sprayed by a High Power Plasma System for SOFC Application
Authors: Goubot N. , Dhers J. , Gallet D. , Thery A.
Published: August 2022

The purpose of this work is a general assessment of the evolution of the porosity of a thermal barrier coating (PSZ : Partially Stabilized Zirconia with 7% wt yttria) used as an SOFC electrolyte sprayed by a High Power Plasma system Plazjet using commercial powders. The properties of these coatings are investigated using a microstructural and a physical approach. The different steps concern : - the optimisation of the spraying parameters of the Plazjet gun, in order to obtain either very dense, or porous top coat microstructure. We focused on parameters such as the gun (external, or step) or the morphology of the powder. The use of a strict methodology to analyze the results. Characteristics obtained by various measures, qualitative and quantitative, are compared and discussed.
Comparative Study on Segmented Thermal Barrier Coatings Sprayed from Different Feedstocks
Authors: Guo H.B. , Kuroda S. , Murakami H.
Published: August 2022

Type of powder feedstock greatly affects properties of zirconia coatings since they interact differently in a plasma flame and hence influence microstructure development. In this study, ZrO2-8wt% Y2O3 thermal barrier coatings (TBCs) have been produced by atmospheric plasma spraying fused and crushed (FC) and hollow sphere (HOSP) feedstock powders. The sprayed coatings contained segmentation cracks going through the coating thickness. High substrate temperature during spraying gave rise to increased segmentation crack density (Ds). The FC powder has the capability of providing coatings with high segmentation crack density compared with the HOSP one. At lower temperature, the HOSP coating was more porous than the FC coating sprayed at similar temperature and hence exhibited a much reduced thermal diffusivity. At high plasma temperature, the HOSP particles attained higher particle surface temperatures and velocities than the FC ones. The particles temperatures and velocities for the HOSP particles were influenced more significantly by spray condition than those for FC particles.
Study of CVD Overaluminising on Different CoNiCrAlY Bond Coats Deposited by High Velocity Oxygen Fuel (HVOF), Low Pressure Plasma Spray (LPPS) and Vacuum Plasma Spray (VPS)
Authors: Scrivani A. , Rizzi G. , Stanic V.
Published: August 2022

Coating technology is progressing at a steady rate with continuous significant improvements in the coatings performance. In the aerospace field, as well as in the stationary gas turbine field, coatings deposited by different processes (thermal spray, CVD, EBPVD) play an important role in order to increase the performances of the engines. In particular, in order to improve the resistance to oxidation and corrosion at high temperature, aluminium is deposited by several techniques (pack aluminising, above the pack and CVD) in alternative or addition to thermal spray coatings (mainly MCrAlY alloys where M stands for Co, Ni or CoNi). These MCrAlY coatings are generally deposited by Low Pressure Plasma Spray (LPPS) or Vacuum Plasma Spray (VPS), but also by High Velocity Oxygen Fuel (HVOF) and Air Plasma Spray (APS). This paper addresses the study of aluminium coatings deposited by CVD on CoNiCrAlY bond coats deposited by different processes: VPS with F4 gun, LPPS with EPI gun and HVOF. The aim is to verify if and how the different CoNiCrAlY coatings obtained by these three processes with different content of oxides and porosity could affect the deposition rate and quality of the Al coatings. The obtained samples have been characterized from the metallographic point of view in order to determine porosity, thickness and structure of both CoNiCrAlY and Al coatings. Al coating thickness has been taken as parameter in order to define the Al coating deposition rate on the three different CoNiCrAlY coatings. Further tests for the determination of aluminium content and chemical composition of the coatings are in progress.
HVOF Spraying of WC-Co Coatings with Liquid-Fuelled and Gas-Fuelled Systems: Competing Mechanisms of Structural Degradation
Authors: Shipway P.H. , McCartney D.G. , Sudaprasert T.
Published: August 2022

It is widely known that during high velocity oxy-fuel (HVOF) spraying of tungsten carbide – cobalt (WC-Co) coatings, decomposition occurs resulting in the formation of W2C and a relatively brittle amorphous binder phase (along with other carbides and even metallic tungsten). Decomposition has generally been seen to be deleterious to the wear resistance of these coatings and, as such, there have been moves to reduce it. Since decomposition during spraying initiates with WC dissolution into the molten binder phase, strategies for its minimization have been based on reduction of particle temperatures and exposure times during spraying. Moves in spraying from gas-fuelled systems to liquid-fuelled systems have contributed towards these goals. This paper examines microstructural features and wear behaviour of WC-Co coatings deposited with both a liquid-fuelled and a gas-fuelled system. Contrary to expectation, it was found that the wear rate of the liquid-fuel sprayed coating was five to ten times higher than that of the gas-fuel sprayed coating. It was shown that whilst the degree of decomposition was limited during spraying with a liquid-fuelled system, the solid core of WC-Co suffers significant mechanical damage on impact as it is deposited, resulting in carbide fracture and size reduction and thus to the low observed wear resistance.
Oxidation of HVOF-Sprayed Hardmetal Coatings
Authors: Berger L.-M. , Zieris R. , Saaro S.
Published: August 2022

In the current study, the oxidation of hardmetal coatings (WC-12%Co, WC-17%Co, WC-10%Co4%Cr, WC-20%“CrC”-7%Ni, Cr3C2-25%NiCr, (Ti,Mo)(C,N)-29%Ni and (Ti,Mo)(C,N)-29%Co) in the temperature range 350- 900°C was studied for test durations ranging from 2 h to 128 h. The formation of oxide scales was investigated by X-ray diffraction, as well as by optical microscopy and SEM (including EDX) of coating cross sections. For coatings obtained by spraying with DJH 2700 and TopGun HVOF systems, the phase composition had only a moderate influence on high-temperature oxidation behavior in atmospheric conditions. The first oxides detectable by X-ray diffraction appeared on the coating surfaces after oxidation at 350°C for 128 h for all coatings. Pronounced oxidation (formation of oxide scales with thicknesses of greater than 10 µm) started at 600°C. Oxide scale growth differed significantly above this temperature among the hardmetal compositions studied here. WC-20%"CrC"-7%Ni and Cr3C2-NiCr had the highest oxidation resistance, with the oxide scale thicknesses lying below 10 ìm after oxidation at 800°C and 900°C for the two materials, respectively.
Influence of Spraying Parameters on the Properties of HVOF Alumina Coatings
Authors: Riley M.A. , Sturgeon A.J.
Published: August 2022

The HVOF spraying process has recently been considered for the deposition of dense alumina coatings for dielectric coatings in semiconductor applications and as a turbine blade tip coating in aeroengines. However, due to the lower flame temperature of the HVOF process compared to the plasma spray process it is necessary to have good control over the key process parameters to achieve the correct coating characteristics. The work reported presents the results of a design of experiment study carried out on a TopGun HVOF system used to prepare coatings of alumina. The influence of several key parameters on coating characteristics such as porosity, alumina phase type, microhardness, surface roughness and adhesion have been determined. The parameters varied included oxygen and hydrogen fuel gas flow rates, and spray distance. Based on the results of these investigations recommendations are made on the control of key parameters and the range of coating characteristics that can be expected.
Relationship between Surface Topography Parameters and Adhesion Strength for Plasma Spraying
Authors: Bahbou F. , Nylén P.
Published: August 2022

To achieve sufficient adhesion strength within thermal spraying, the surface to be coated has to be modified. Grit blasting is the most common way to generate a clean and roughened surface. The bonding mechanism between the grit-blasted substrate and the coating is assumed to be due to mechanical anchoring, why an optimal surface roughness is essential. The surface roughness is usually evaluated using Ra which cannot fully characterize the complex nature of the chaotic substrate topography. This study was performed in order to evaluate if Ra can be replaced by other surface characteristic parameters such us RΔq, Rpk, Rpv, Rk…with higher correlation to adhesion strength. Average roughness was measured by a perthometer and with white light interferometry to get 3D images of the surface topography. Disc shaped substrate samples of Ti6Al4V (AMS 4928) were grit blasted with aluminium oxide grit and plasma sprayed with a Ni5%Al coating. Adhesion strength was determined according to the ASTM C633 standard. The correlation between a number of different surface-parameters and adhesion strength were evaluated and compared with Ra.
New Technique of Laser Cladding with Tungsten Carbide and Diamond
Authors: Machi F. , Dezert D. , Maybom H. , Desmette S. , Lamiene E. , Bauninger G. , Nicholson C. , Cerny E. , Magnee A. , Zenati R. , Fantozzi G.
Published: August 2022

Wear resistance of materials in very aggressive environment of different industrial sectors like drilling, mining, cutting, etc, appears to be critical and many efforts have been made to limit the major economic loss that represents a broken or damaged tool. The objective of the CLADIAM project (G5ST-CT-2002-50179) is to develop a cladding technique to coat complex parts based on an innovative cladding material composed of diamond pellets and cast spherical tungsten carbide particles using an automated high power diode laser (HPLD) equipment. The result of these two and a half years of work has led to the finalization of following techniques: A pelletizing alloy that takes into account the constraints of laser cladding, Enrobing of diamond particles to avoid their damage, An industrial technique, technically and economically efficient, of laser cladding that allows the realization of complex shapes. The combination of a new technique of wear and abrasion tests has led to the characterization of the obtained cladding. The results have been compared with the tests on industrial parts in severe and even extreme wear conditions. The development of this new cladding technology has been possible thanks to the use, the characterization and the optimization of specific cladding nozzles associated with the special beam of high power diode laser. The results obtained are very encouraging and open the doors to new claddings that combine the specific advantages of diamond and tungsten carbides for the nature of cladding, but also the fineness of the structure, the improvement of behaviour in wear conditions, the small thermal impact of the parts, some of the well known advantages of laser cladding.
The Effects of Deposition Parameters and Gaseous Detonation Equipment Design on the Coating Formation
Authors: Kharlamov Y. , Chattha J.A. , Kharlamov M.
Published: August 2022

By use of up-to-date methods of gaseous detonation spraying it is possible to obtain coatings with wide range of thermal and kinetic energy of sprayed particles and their state (liquid, solid, semiliquid, with change of their chemical and phase composition duration of stay in impulse hot gaseous detonation jet, etc.). The philosophy of gas detonation sprayed coating structure and properties control include next basic methods: (1) change of values and ratio of thermal and kinetic energy of sprayed particles; (2) governing of thickness and sizes of single layers of coating (“coating spot“), D-Gun rate of fire, and relative velocity of moving of D-Gun and workpart; (3) change of dispersion and shape of powder particles; (4) regulation of thermal cycle of coating in process of spraying by use preliminary, concomitant or post spraying heating or cooling; (5) use of variable spraying modes for obtaining of individual layers and zones of coating (change of composition and flow rate of gases and powder, D-Gun fire rate, powder dispersion, distance of spraying, etc.); (6) settlement of ratio between percentage of amorphous, microcrystalline and crystalline phases, metastable and equilibrium phases by selection of rational conditions of spraying; (7) control of degree of physico-chemical transformations into powder particles (polymorphic transformations, dissociation, oxidation, interaction between components of composite powders, etc.), change of time of particles stay into gas products flow, composition and parameters of gaseous medium, etc.; (8) alloying of sprayed powders as for assurance of necessary properties of coatings as for improvement of their inclination to coating formation (oxidation resistance into high temperature gas flow, inclination of seizure, etc.); (9) use of composite powders; (10) spraying at mode with powder particles which have premelting temperature at time of coating formation; (11) treatment of sprayed coatings (thermal, thermo-chemical, thermo-mechanical, etc.); (12) control of coating macrostructure by successive deposition of layers, bands and spots of coatings with smooth or abrupt change of composition, deposition of discrete coatings; etc. Abstract only; no full-text paper available.
Construction and Analysis of Ozone Condensation System for Oxide Superconductor Thin Film
Authors: Cheon M.-W. , Park Y.-P.
Published: August 2022

An ozone condensation system is evaluated from the viewpoint of an ozone supplier for oxide thin film growth. Ozone is condensed by the adsorption method and its concentration is analyzed using the thermal decomposition method. The concentration of ozone exceeds 90 mol% and ozone is supplied for a sufficiently long time to grow oxide thin films. Investigation of the ozone decomposition rate demonstrates that ozone can be transferred into the film growth chamber without marked decomposition. The ozone concentration is also evaluated using a quadrupole mass analyzer and the accuracy of this method is compared with the results of the thermal decomposition method.
Oxidation Behavior of In-Flight Molten Aluminum Droplets in the Twin-Wire Electric Arc Thermal Spray Process
Authors: Guillen D. , Williams B.G.
Published: August 2022

This paper examines the in-flight oxidation of molten aluminum sprayed in air using the twin-wire electric arc (TWEA) thermal spray process. The oxidation reaction of aluminum in air is highly exothermic and is represented by a heat generation term in the energy balance. Aerodynamic shear at the droplet surface: (1) enhances the amount of in-flight oxidation by promoting entrainment and mixing of the surface oxides within the droplet, and (2) causes a continuous heat generation effect due to the exothermic oxidation reaction that sustains droplet temperature as compared to a droplet without internal circulation. This continual source of heat input keeps the droplets in a liquid state during flight. A linear rate law based on the Mott-Cabrera theory was used to estimate the growth of the surface oxide layer formed during droplet flight. An explanation is provided for the elevated, nearly constant surface temperature (~ 2000 °C) of the droplets during flight to the substrate and it is shown that the majority of oxide content in the coating is produced during flight, rather than after deposition. The calculated oxide volume fraction of an average droplet at impact agrees well with the experimentally determined oxide content for a typical TWEA-sprayed aluminum coating, which ranges from 3.3 to 12.7%.
Corrosion Properties of Plasma-Sprayed Coatings using Oxide Powders
Authors: Song Y. , Ahn J. , Kim B-Y. , Lee D. , Nam K. , Lee K-H.
Published: August 2022

Three different oxides of CrO2-TiO2, Al2O3 and Al2O3-TiO2 were plasma-sprayed on Ti substrate to evaluate the crystal structure and the corrosion properties of the coatings. No phase change of the coatings after corrosion test in 0.5 M H2SO4 solution at 25°C was found regardless of the presence of the NiCoCrAlY bond layer. Electrochemical measurements and SEM results revealed that the single coatings without the bond layer were always effective against corrosion resistance due to lower current density within the passive region. Pitting corrosion of the surface was observed for the Al2O3 coating. It can be concluded that the Al2O3-TiO2 coating without the bond layer may be the best oxide among the oxides investigated due to low porosity (5.4%), smooth surface roughness (4.5 m), low current density (6.3×10-8 A/cm2) in the passive region, low corrosion potential (Ecorr, -0.55 V) and no pitting corrosion.
Plasma Sprayed Self Lubricant Coatings
Authors: Tului M. , Valente T. , Becker D. , Wagner S.
Published: August 2022

The present work aimed at demonstrating the effectiveness of graphite containing plasma sprayed coatings to reduce friction coefficient in dry or starving lubrication conditions. Operative, environmental and economic considerations were important driving factors. Graphite particles were mechanical mixed with a cermet powder containing a fine dispersion of chromium carbide particles in a nickel-chrome metallic matrix. The coatings material was deposited by Atmospheric Plasma Spray onto steel substrates. The microstructure of the obtained coating was characterised by XRD and SEM/EDS. A strip draw apparatus, simulating the stamping process of steel sheets, was used to test the coatings. Several operative conditions were reproduced, by modifying the load and the amount of lubricant used. For comparison, uncoated samples were tested in the same conditions. The comparison of the results of strip draw tests carried out on coated and uncoated samples, shown that the use of graphite based self-lubricant coatings, deposited by plasma spray, allowed to decrease drastically the amount of lubricant.
Visualization of Impact of Plasma-Sprayed Molybdenum Particles on Hot and Cold Glass Substrates
Authors: McDonald A.G. , Lamontagne M. , Moreau C. , Chandra S.
Published: August 2022

Plasma-sprayed, molten molybdenum particles (~50 µm diameter) were photographed during impact (with velocity ~135 m/s) on a glass surface that was maintained at either room temperature or 400°C. A droplet approaching the surface was sensed using a photodetector and after a known delay, a laser was triggered to illuminate the spreading splat and photograph it with a CCD camera. A rapid two-color pyrometer was used to collect the thermal radiation from the impacting particles to follow the evolution of their temperature and size after impact. Molten molybdenum particles impacting on a surface at room temperature splashed and broke up after impact leaving only a small portion adhering to the substrate. On a surface held at 400°C, there was no splashing and a circular splat remained on the surface. Splats on a glass surface held at room temperature had a large maximum spread diameter, approximately 2.7 times that on a hot surface. The cooling rate on a cold surface was an order-of-magnitude lower than that on a hot surface, suggesting that thermal contact resistance was much greater.
Stellite 6 Coatings Obtained by HVOF using Different Fuel Gases
Authors: Guilemany J.M. , Nin J. , Miguel J.R.
Published: August 2022

Bulk, welded or laser cladded Stellite based materials are widely used in chemical industry due to their excellent combined properties against corrosion and wear processes and as a superalloy they have a high melting point and are designed to withstand high temperature for long periods of time. Problems related with poor inter-splat bonding arise when this kind of materials are sprayed with HVOF because it is characterized by having relatively low flame temperatures and high particle speed, and so dwell time may not be long enough to melt or soften Stellite particles completely. For these reasons, typical structured composed by a superposition of non-melted particles are obtained when spraying with propylene fuel gas. The aim of this work is to study the effect of using Hydrogen as a fuel gas and also to study the effect of the variation of the propylene flame characteristics. The coatings are characterized by SEM-EDS, XRD, and ASTM G99-90 sliding wear test has been done to compare the coatings. SWLI has been used to measure the volume lost after the wear test. Splat morphology studies have been also done in order to compare the melting behavior of the impinging particles.
Kinetic Spraying Deposition Behavior of Bulk Amorphous NiTiZrSiSn Feedstock
Authors: Yoon S. , Lee C. , Kim H.J. , Choi H.
Published: August 2022

Kinetic spraying process that is basically a solid-state deposition process was used for the formation of a fully amorphous coating. As the application of pre-heating system for the powder carrier gas and using Helium for the process gas, it was possible to form of amorphous coating. Main process parameters evaluated in this study were gas species[N2 and He]and pre-heating temperature[RT(below Tg) and 550 (liquid metallic region)] for carrier gas. Aside from empirical approach, in-flight particle velocity within kinetic spraying process was measured with spray-watch- 2i. The deposition behaviors of a NiTiZrSiSn bulk amorphous powder were observed when it was sprayed using kinetic spraying process. When the bulk amorphous feedstock material was coated, both kinetic energy and thermal energy of the in-flight particle are important. The former did affect on the deposition of the bulk amorphous coating, while the later did more affect on mechanical properties of coating. Particle deposition behaviors were considered from the viewpoint of the environmental effect such as particle energy combination on the deposition behaviors. The bonding of the impacting NiTiZrSiSn bulk amorphous particle was primarily dependent on the temperature dependent deformation and fracture(local liquid drop formation) behavior.
Diagnosis of In-Flight Particles During Arc Spraying of Carbon Steel and Relationships with Microstructures of the Deposited Layers
Authors: Seong B.-G. , Kim J.-H. , Hwang S.-Y. , Baik K.-H.
Published: August 2022

An experimental study was conducted to study the effects of properties of in-flight particles on microstructures of coating layers using a wire arc spraying system. In this study, 0.8% carbon steel wires were used for arc spraying and nitrogen gas was used as atomizing gas. Temperature, velocity and distributions of the in-flight particles were measured by DPV2000 for different working conditions. Specimens of spray-footprint were made and microstructures of them were evaluated. As a result, amount of oxide in a coating layer was proved to be related with the temperature of the in-flight particles. Because oxidation of the molten steel particles is an exothermic reaction, higher temperature of the particles during arc spraying means higher area fraction of oxide in the coating layers. For this reason, oxide level is lowest at the central area of spray footprint and it becomes higher as the distance from the center increases. Hardness, porosity and phase are changed according to the distance from the center. Abstract only; no full-text paper available.
Computational Modelling of a Thermo-Aabrasive Blasting Gun
Authors: Gorlach I.A. , Markgraaff J.
Published: August 2022

In the last few years, a new method for surface preparation has evolved, namely thermo-abrasive blasting. This technique utilises a high enthalpy thermal jet to propel abrasive particles. The thermo-abrasive blasting gun, also called a thermal gun, is based on the principles of High Velocity Air Fuel (HVAF) processes. Some empirical data is available on thermo-abrasive blasting method and systems. To effectively improve on nozzle design and productivity, modelling of the thermo-abrasive blasting process was required. This paper describes the computational modelling of the thermal gun with computational fluid dynamic software, namely STAR-CD. The developed computational model can be applied to HVAF systems used for thermo-abrasive blasting and thermal spraying.
Modeling of the Heating of Cast Iron Particles during Plasma Spraying
Authors: Kharlamov Y.A. , Shevchenko A.V. , Budagyunts N.A. , Chattha J.A.
Published: August 2022

The mathematical model intended for modeling of the acceleration, heating, and melting of alloyed cast iron particles into plasma jet is presented. Comparison of mathematical modelling and experimental measurement results showed fairly good agreement.
Effect of Substrate Surface Change by Heating on Flattening Behavior of Thermal Sprayed Particles
Authors: Fukumoto M. , Ohgitani I. , Nagai H. , Yasui T.
Published: August 2022

It has been confirmed in the flattening behavior of the thermal sprayed particles that the splat shape on the flat substrate surface changes to a disk type from a splash type at relatively narrow temperature range with increasing the substrate temperature. The temperature increasing actually causes a certain non-reversible change on the substrate surface, because the changing effect is maintained till the substrate is cooled down to the room temperature. We have pointed out that this non-reversible change on substrate surface due to the heating might be the possible domination for the transition phenomenon of the thermal sprayed particles, that is, the essence of the substrate surface change due to the heating is surface roughness in nano-meter range. In this study, several kinds of substrates once heated to some elevated temperature were analyzed precisely by atomic force microscope (AFM) to characterize the change in their surface roughness character. The fundamental static wetting behavior of the substrate surface by a water droplet was investigated for the reference in the present study. The results obtained revealed that the change of the substrate surface topography in nano-meter range affect most effectively the wetting behavior of the droplet or splat on the surface. Hence, the substrate heating may bring about the change in the physical way on the substrate surface and this change induces the transition phenomenon.