bluuebunny/crossref_metadata_2025 huggingface dataset:
Deformation Behavior and Properties of a CuZrTiNi BMG Kinetic Spray Coating
Authors: Kim J.S. , Xiong Y.M. , Lee C. , Choi H.S. , Kim H.J.
Published: September 2022

The deformation behavior and mechanical properties of a Cu54Zr22Ti18Ni6 bulk metallic glass during and after deposition by kinetic spraying were investigated. The bulk metallic glass feedstock particles were manufactured by inert gas atomization and were subsequently deposited onto mild steel substrates by means of kinetic spraying at different powder carrier gas temperatures [room temperature, 450°C (within the supercooled liquid region), and 550°C (above crystallization temperature)]. In addition, the phase compositions of the feedstock and as-sprayed BMG coatings were investigated using X-Ray Diffraction (XRD), Differential Scanning Calorimetry (DSC), and Transmitted Electron Microscopy (TEM). With an increase of the powder feed temperature, it was deduced that more intimate contact of the particles with the substrate was achieved which decreased the porosity of the resulting coating. However, crystallizations, which seemed to be induced by severe deformation and accumulated heat, were observed at localized regions in the coating. In addition, micro-hardness and bond strength were affected by the crystallization degree of the as-sprayed coatings
Examination of the Estimating Approaches for the Critical Velocity in Cold Spraying
Authors: Li C.-J. , Yang G.-J. , Li C.-X. , Bang H.S. , Bang H.S. , Li W.-Y.
Published: September 2022

The particle critical impact velocity is a key parameter in cold spraying. The appropriate estimation of this critical velocity benefits the optimization of coating deposition in terms of deposition efficiency. The critical velocity can be estimated experimentally through measuring the relation between deposition efficiency and particle velocity. A recent study has revealed that the critical velocity can be estimated by the velocity resulting in the onset of adiabatic shear instability through numerical simulation of particle impact. However, it was found that the critical velocities of a pure metal material obtained by different investigators through simulation were significantly different. No reasonable explanation was provided to such difference. In the present paper, the critical velocities reported in the literature for Cu powder as a typical material were reviewed. The factors influencing the critical velocity were examined. The numerical simulation methods employed in the limited literature were also examined for a better understanding of the factors that influence the simulated results. A reasonable estimation method was proposed by using the numerical critical velocity.
DYMET Technology Evolution and Application
Authors: Kashirin A. , Klyuev O. , Buzdygar T. , Shkodkin A.
Published: September 2022

High requirements of Cold Gas Dynamic Spray (GDS) process caused the development of low pressure DYMET technology. The technology and equipment evolution is presented and discussed. Modern portable low pressure DYMET equipment may be easily applied for various technical problem solutions. Multiple applications are briefly described.
Improvement of Plasma Gun Performance using Comprehensive Fluid Element Modeling: Part 2
Authors: Molz R. , McCullough R. , Hawley D. , Muggli F.
Published: September 2022

Utilization of a comprehensive validated computer model of a thermal spray process enables an ability to improve, optimize, and fine tune the performance of that thermal spray process. A validated model of the Sulzer Metco TriplexPro 200 plasma gun has been used to improve the performance of the actual gun in terms of enhancing gas flow dynamics, thermal management, and overall performance in terms of a robust design. Internal changes to the gun geometry using the model have extended the life of the hardware beyond any current plasma gun. In addition the model has permitted the investigation of the fundamental operation of the gun, specific to the behavior and path of the arcs, as well as the ability to operate the plasma gun, under simulation, in operating regimes that currently cannot be supported by the physical hardware. The model has been run at gas pressures above 14 bar and/or voltages above 300V that currently cannot be obtained with the physical hardware due to equipment limitations to evaluate the potential to extend the operating window of the Sulzer Metco TriplexPro 200 gun beyond current levels in terms of particle velocity and temperature. The end result is an improved process tool for applying thermal spray coatings from high temperature ceramics to relatively colder and faster carbides and alloys.
Modeling and Diagnostic Study of a Supersonic Impinging Plasma Flow Near the Surface of a Substrate
Authors: Xue S. , Lakaf Y. , Gravelle D. , Boulos M.I.
Published: September 2022

A consistent thermal and chemical non-equilibrium model for inductive supersonic plasma flow, developed recently, is applied to the modelling of pure argon supersonic plasma flow, which impinges on a substrate below the Mach 1 nozzle. The model considers the ionization of argon atom and the corresponding recombination but the second order ionization is ignored and plasma charge neutrality is assumed. The transport and mass diffusion coefficients are computed using the collision cross-section data, published by Devoto and Murphy and the computations of transport properties are fully coupled with the calculation of the plasma flow fields. The model treats the subsonic discharge region above the supersonic nozzle and the supersonic region below the nozzle together. Two different turbulent models are incorporated into the model to describe the supersonic plasma flow. The modeled radial and axial profiles of electron and heavy species temperatures and electron number densities near the substrate are then compared to those measured by the method of optical emission spectroscopy and finally the most realistic model is identified.
Modeling of the In-Flight Particles Characteristics Using Neural Networks and Analytical Model
Authors: Kanta A.F. , Planche M.P. , Montavon G. , Coddet C.
Published: September 2022

In thermal spray process, the in-flight particle characteristics such as particle size, velocity and temperature influence significantly their flight duration as well as their melting degree. Consequently, they influence the splat formation and ultimately the coating properties. Thus, the knowledge of the interactions between the process parameters and the in-flight particle characteristics is very important for optimizing the coating properties. Artificial Neural Network (ANN) concept was used to predict in-flight particle velocity and temperature considering the case of alumina (Al2O3-TiO2) coatings. Databases of in-flight particle characteristics (diameter, velocity and temperature) versus spray process parameters (arc current intensity, hydrogen rate and plasma gas composition) were collected. ANN was trained with the database to establish the relationships linking the particle diameter and spray process parameters to particle velocity and temperature. Then, the established ANN relationships permitted to determine the inflight particle velocity and temperature versus their diameter for given spray process parameters. These velocity and temperature data were then used to determine the time for complete particle melting and the particle dwell-time before impact by an analytical model for given operating conditions.
Mathematical Modeling of Coating Under Shock Loading of Nanopowder Layer
Authors: Kiselev S. , Kiselev V.
Published: September 2022

A procedure for calculating the adiabat of copper nanopowder is developed. The nanopowder adiabat was determined from numerical calculations at the nano-level performed by the molecular-dynamics method. With the use of this procedure, the problem about copper nanopowder compaction in a metal container under the action of an oblique shock wave was addressed. The temperature rise behind an oblique shock wave in the nanopowder is two orders of magnitude greater than in the micropowder.
Predicting Splat Morphology in a Thermal Spray Process
Authors: Dhiman R. , Chandra S.
Published: September 2022

Splats formed during a thermal spray process may be either highly fragmented or intact and disk-like. To predict this change in splat morphology, a dimensionless solidification parameter (Θ), which takes into account factors such as the substrate temperature, splat and substrate thermophysical properties, and thermal contact resistance between the two, has been defined. Θ is the ratio of the thickness of the solid layer formed in the splat while it is spreading, to the splat thickness. The value of Θ can be calculated from simple analytical models of splat solidification and spreading. If the solid layer growth is very slow (Θ << 1), the droplet spreads out to a large extent. Once it reaches maximum spread it becomes so thin that it ruptures, producing fragmented splats. If, however, the solid layer thickness is significant (Θ ~ 0.1 – 0.4), the droplet is restricted from spreading too far and does not become thin enough to rupture. Under such circumstances, disk-type splats are expected. When the solid layer growth is rapid (Θ~1), spreading of the droplet is significantly obstructed by the solid layer, producing splats with fingers around their periphery. Predictions from the model are compared with experimental data.
Numerical and Experimental Study of Ni-Particle Impact on a Ti-Surface
Authors: Bahbou M.F. , Choquet I. , Nylén P.
Published: September 2022

The impact of plasma sprayed sieved Ni-5%Al particles on a titanium substrate was investigated. The particles had a narrow diameter range (-65 + 75 µm), and a speed and temperature just prior to impact of about 100m/s and 2400°C, respectively. These powder particles were sprayed on two sets of polished titanium alloy surfaces. One set was a non-oxidized surface and the other one was a previously oxidized surface at 600°C for two hours. Resulting splats were characterised experimentally by infrared pyrometry and scanning electron microscopy. The effects of the substrate’s oxide layer on the shape of the splat, also on the cooling rate and flattening speed during impact were studied and discussed. This problem is also being investigated numerically. A first step was devoted to the selection of relevant simulation parameters. Test cases to study qualitatively the effect of surface oxidation through parameters such as the contact angle and thermal contact resistance are in progress. They will be compared to the experimental results.
A New Concept of the Application of Shock Wave Technology in the Cold Gas Dynamic Spray Process
Authors: Bobzin K. , Lugscheider E. , Nickel R. , Parkot D. , Varava W. , Olivier H. , Luo X.
Published: September 2022

A new cold spray process for a combustion-free spraying is studied experimentally and by modeling and simulation. The high particle velocity at the front of the substrate is achieved by using the shock tube technology. The particles have been injected downstream of the nozzle throat into a supersonic nozzle flow. The shock tube of 6.5 m length and 56 mm inner diameter provides the necessary reservoir conditions for the nozzle flow. The measurements of the particle velocity made by a laser Doppler anemometry (LDA) setup showed that the maximum velocity amounts to 1220 m/s for stainless steel particles of 15 µm diameter. The CFD-Code (Fluent) is first verified by a comparison with available numerical and experimental data for gas and gas-particle flow fields in a long Laval-nozzle. The good agreement implied the great potential of the new dynamic process concept for cold gas coating applications. Then the flow fields in the short Laval nozzle designed and realized by the Shock Wave Laboratory (SWL) have been investigated. The gas flow for experimentally obtained stagnation conditions has been simulated. The gas-particle flow without and with the influence of the particles on the gas flow has been calculated by the Surface Engineering Institute (IOT) and compared with experiments. The influence of the injection parameters on the particle velocities has been investigated as well.
Simulation on Controllable-Porosity Coating by Plasma Spray
Authors: Zhang H.O. , Hu B.Y. , Wang G.L.
Published: September 2022

A new method was introduced to fabricate porous coating and to control its porosity by changing spray parameters. Two models were constructed to simulate the deformation of molten particle and the deposition process of splats on substrate. Considering the gap-pore, step-pore and shield-pore in the presented models, the influence of spray angle on the porosity of coating was mainly investigated. Besides, other spray parameters which influence porosity were analyzed, including the velocity of spray gun, particle velocity and particle size. Moreover, a new forming method of graded porous coating is discussed.
Influence of Droplet Breakup and Collision in the Solution Precursor Plasma Spraying Process
Authors: Shan Y. , Coyle T.W. , Mostaghimi J.
Published: September 2022

Finely structured ceramic coatings can be obtained by solution precursor plasma spraying. The final structure of the coating highly depends on the droplet size and velocity distribution at the injection, the evolution of the spray in the jet, and droplet breakup and collision within the spray. This paper describes a 3D model to simulate the transport phenomena and the trajectory and heating of the solution spray in the process. O’Rourke’s droplet collision model is used to take into account of the influence of droplet collision. The influence of droplet breakup is also considered by implementing TAB and Wave droplet breakup models into the plasma jet model. The effects of droplet collisions and breakup on the droplet size, velocity, and temperature distribution of the solution spray are investigated. The results indicate that droplet breakup and collision play an important role in determining the final particle size and velocity distributions on the substrate.
Fast Modeling of Phase Changes in a Particle Injected Within a dc Plasma Jet
Authors: Ben Ettouil F. , Pateyron B. , Ageorges H. , El Ganaoui M. , Fauchais P. , Mazhorova O.
Published: September 2022

When spraying ceramic particles with a low thermal conductivity such as zirconia using Ar-H2 direct-current (d.c.) plasma jets where the heat transfer is important, heat propagation phenomena take place with the propagation of melting, evaporation or even solidification fronts. Most models neglect these heat propagation phenomena assuming the particle as a lumped media. This work is aimed at developing a model coupling the effect of heat propagation with the particle dynamic within plasma jets. It uses an adaptative grid in which the coordinates of the phase change fronts are fixed. It allows minimizing the calculation costs (approximately 10 seconds on PC under windows XP against 1hour with an enthalpy model). Such calculations are illustrated for dense and porous agglomerated zirconia as well as iron particles which evaporation in an Ar- H2 (25 vol %) plasma is important.
Effect of Microstructure of HVOF-Sprayed WC-Co Coatings on Their Mechanical Properties
Authors: Chivavibul P. , Watanabe M. , Kuroda S.
Published: September 2022

Twelve commercially available WC-Co powders with different average carbide sizes (0.2, 2, and 6 µm) and cobalt contents (8, 12, 17 and 25 wt.%) were sprayed on carbon steel substrates using High Velocity Oxy-Fuel (HVOF) spraying Characterization of the coatings showed that the average carbide sizes and carbide volume contents in the coatings were lower than those of feedstock powders. Hardness and fracture toughness of the coatings were investigated using indentation techniques. Young’s modulus was measured by an ultrasonic technique. The hardness and Young’s modulus decreased with increasing cobalt content, while fracture toughness slightly increased. The effect of carbide size on the hardness showed no specific trend. These behaviors were discussed with the help of microstructure observations of the coatings by scanning electron microscopy, X-ray diffraction and chemical analysis. Using an improved HVOF process with a gas shroud could result in less decomposition of the powder and higher fracture toughness.
Optimization of a Rotating Twin Wire-Arc Spray Gun
Authors: Bolot R. , Liao H. , Mateus C. , Coddet C. , Bordes J.M.
Published: September 2022

The replacement of cast iron sleeves through thermal spray coatings is an interesting alternative to improve the inter bore reliability, to reduce weight and to reduce the inter bore distance for automotive engines. Most of the actual production and pilot equipments use the ROTAPLASMA process to provide such functional coatings. However, the wire-arc spray process may often present different advantages like a higher deposition rate and a lower cost of the produced coatings. The LDS (Lichtbogendrahtspritzen) technology developed by DaimlerChrysler is a wire-arc process working with two wires whereas the PTWA (Plasma Transferred Wire Arc) process designed by Flame Spray Industries and the Ford Motor Company use a single wire. The present paper shows that the wire-arc technology may replace efficiently the APS (Atmospheric Plasma Spray) for the generation of thermally sprayed coatings applied on engine cylinder bores. A first rotating wire-arc spray system was previously designed and tested a few years ago. The present paper shows how computational fluid dynamic (CFD) may help in solving industrial problems: the FLUENT CFD code was used in order to perform improvements of the initial gun design.
Plasma-Sprayed Calcium Oxide Stabilized Zirconia Coatings for Biomedical Application
Authors: Wang G.C. , Liu X.Y. , Ding C.X.
Published: September 2022

Calcium oxide stabilized zirconia coatings have been deposited onto Ti-6Al-4V substrates by means of atmospheric plasma spraying and incubated in the simulated body fluid for different periods of time to investigate the formation of apatite on their surface. The phase composition and microstructure of the coatings before and after immersion were examined by scanning electron microscopy and X-ray diffraction. The results obtained showed that apatite can be formed on the coating soaked in SBF solution, which indicated that calcium oxide stabilized zirconia possessed good bioactivity.
In Vitro Durability of Titanium/Dicalcium Silicate Composite Coatings
Authors: Xie Y.T. , Zheng X.B. , Liu X.Y. , Ding C.X.
Published: September 2022

Titanium/dicalcium silicate composite coatings with different ratios (weight ratios as Ca2SiO4: Ti = 3:7, 5:5, 7:3) were prepared by plasma spraying. Effects of titanium addition on coating properties, such as bonding strength, Young’s modulus and dissolution in simulated physiological environment, were studied. Results showed that the bonding strength between coating and Ti-6Al-4V substrate increased with increase of titanium content in the composite coatings. It was explained by the narrowed dissimilarity of thermal expansion coefficients between the coatings and substrates. Degradation of mechanical properties after immersion in simulated body fluid was also studied. The dissolution of dicalcium silicate in the composite coatings resulted in the decrease of bend strength and Young’s modulus of the coatings in the simulated physiological environment. The higher titanium content in the composite coatings, the stabler are the composite coatings in the physiological environment.
Progress in Plasma Sprayed Bioceramic Coatings
Authors: Ding C.
Published: September 2022

Plasma sprayed hydroxyapatite coating can bond to living bony tissue, and it is being widely used in clinical application. The problem of hydroxyapatite coating on metal substrate may mainly come from the instability of coating-substrate interface and the unstable duration of coating in the presence of body fluid. Therefore, it is desirable to develop newly bioactive coatings with good bioactivity and mechanical properties. In this paper, new progress in plasma sprayed bioactive coatings at Shanghai Institute of Ceramics are reviewed. The novel coatings including wollastonite, dicalcium silicate, diopside and titania were deposited. All the bioactive coatings mentioned above form a bone-like apatite layer on their surface immersed in simulated body fluid, indicating their good bioactivity. The formation of bone-like apatite is induced by Si-OH and Ti-OH on the surface of coatings. The results of cell culture test indicated that novel coatings can enhance osteoblast adhesion, proliferation and differentiation, indicating their good biocompatibility.
Properties and Performance of High Purity Thermal Barrier Coatings
Authors: Xie L. , Dorfman M.R. , Cipitria A. , Paul S. , Golosnoy I.O. , Clyne T.W.
Published: September 2022

It was found that the content of impurity oxides in 7YSZ, such as SiO2 and Al2O3, has a significant effect on the coating sintering resistance and phase stability of 7YSZ thermal barrier coatings (TBCs). The reduction of the impurity content will significantly improve the sintering resistance and phase stability of 7YSZ TBCs and thus allow the 7YSZ TBCs to be used at higher temperatures.
Evaluation of Adhesion/Cohesion of Plasma Sprayed Ceramic Coatings by Scratch Testing
Authors: Ding C.X.
Published: September 2022

Plasma sprayed ceramic coatings have been widely applied in modifying surface properties of metal components. They are useful to prevent various types of wear, corrosion, erosion and thermal degradation, thereby extending components service life and reducing the need for expensive and repetitive maintenance. The durability and functionality of plasma sprayed ceramic coatings is critically dependent on the adhesion between the ceramic coating and the underlying substrate as well as the cohesion between splats. In this work, both nanostructured and conventional Al2O3 coatings were prepared by atmospheric plasma spraying technology (APS). For each feedstock, four kinds of coating samples deposited under different spraying parameters were designed, and moreover, seven groups of conventional coatings with different thickness were deposited under the same spraying parameters. Adhesion/cohesion of the plasma sprayed Al2O3 coating samples were evaluated by scratch testing. The results obtained reveal that the spraying parameters have strong influences on the microstructure of plasma sprayed Al2O3 coatings, which in turn influence their properties including deposition efficiency, porosity, microhardness as well as adhesion/cohesion.
Evaluation of APS YPSZ Powder and Coating Homogeneity: XRD and Raman Spectroscopy Studies
Authors: Lawson K.J. , Ritchie L.J. , Xie L. , Dorfman M.R.
Published: September 2022

The monoclinic and tetragonal phase compositions and distribution in air plasma sprayed (APS) yttria-partially stabilized zirconia (YPSZ) thermal barrier coatings were studied. The coatings were produced from powders with varying phase concentrations, chemical purity and powder production processes. Both the powder and coatings were characterized using X-ray diffraction (XRD) and Raman spectroscopy. The use of environmental scanning electron microscopy (ESEM) and X-ray energy dispersive analysis (EDS) added morphological and elemental information to the study. XRD and Raman spectroscopy were shown to be powerful combined tools and shows an overall decrease in the monoclinic phase within the coatings produced from the different powders. The distribution of both the monoclinic and the tetragonal phases could be highlighted both in the coatings and the individual powder particles. This indicated changes in monoclinic concentration in the less dense areas of some of the coatings and a varying distribution across particles in some of the powders. Raman mapping over small areas also showed how phase surface distribution, on the coatings surfaces, could be assessed.
Zircon-Based Ceramics Composite Coating for Environmental Barrier Coating
Authors: Suzuki M. , Sodeoka S. , Inoue T.
Published: September 2022

Studies on plasma spraying of zircon (ZrSiO4) have been carried out by the authors as one of the candidates for an environmental barrier coating (EBC) application, and had reported that substrate temperature is one of the most important factors to obtain crack-free and highly-adhesive coating. In this study, several amount of yttria were added to zircon powder, and the effect of the yttria addition on the structure and properties of the coatings were evaluated in order to improve the stability of the zircon coating structure at elevated temperature. The coatings obtained were composed of yttria stabilized zirconia (YSZ), glassy silica, while the one prepared from monolithic zircon powder composed of the metastable high temperature tetragonal phase of zirconia and glassy silica. After the heat treatment over 1473K, silica and zirconia formed zircon in all the coatings. However, the coatings with the higher amount of yttria had less amount of zircon formed. This resulted in the less open porosity of the coating at elevated temperature. These yttria added coatings also showed good adhesion even after the heat treatment, while monolithic zircon coating had peeled off.
Properties of HVOF Sprayed Ferrous Coatings for Corrosion Protection
Authors: Bobzin K. , Lugscheider E. , Ernst F. , Hidalgo G. , Zwick J.
Published: September 2022

The increase of commodity prices for classical corrosion protection materials such as WC/Co and Cr3C2/NiCr are leading to significantly increased coating costs. This reduces the competitiveness when compared to other coating technologies such as electroplating, particularly if carbide coatings are representing an over engineered solution for the considered application. A promising economic alternative is the employment of advanced ferrous materials. Fe-base coatings have the potential for very good corrosion protection and favourable wear properties combined with a low cost level due to relatively low priced alloy materials. In this study three different Fe-base materials have been sprayed by liquid and gaseous fuel HVOF spraying and analysed with respect to microstructure, hardness and corrosion resistance. Corrosion tests have been carried out with sulphuric acid as well as artificial seawater.
Corrosion Behavior of Arc Spraying Nickel Based Coating
Authors: He D.-Y. , Dong N. , Jiang J.-M.
Published: September 2022

In this paper, Ni-based cored wires were prepared by using NiCr strip to wrap metal powders of Ni, Cr, Mo, CrB. Ni-based coatings were prepared by electric arc spraying process. The microstructures of Ni-Cr-Mo and Ni-Cr-B coatings were investigated by means of scanning electron microscopy (SEM) and energy-dispersive analysis (EDAX) and X-ray diffraction (XRD) analysis. The coatings have compact surface and presented the bonding strength higher than 40MPa. Corrosion-resistance performance of coatings was evaluated by salt-spray- test and electrochemical corrosion test. The results showed that Ni-based coatings containing Mo (5%) element or B element (2-4%) had better anti-chlorine ion corrosion performance than that of Ni-based coatings without Mo element, and PS45 (Ni-Cr-Ti) coating. The anti-chlorine ion corrosion coatings could be used for resolving the corrosion protection problem of the equipments and piping contacting sour, alkali, salt liquid in the petrochemical engineering.
Development and Application of DZ9000E Portable HVOF System
Authors: Wang R.J. , Xu L. , Zhang T.J. , Huang X.O. , Luo H.J.
Published: September 2022

Comparing with the traditional liquid oxygen and kerosene HVOF system (LHVOF), the development of the DZ9000E Oxygen Gaseous HVOF system (GHVOF) is emphasized on reduction of the cost of coatings and increasing the in-situ removability to suit various working conditions. DZ9000E hand-held spraying gun is assembled with dual-valve handle, ON/OFF switches for powder feeding, and compressing and cooling valve, which can provide portable and simple operation mode for users. The whole system is economical, which enables the system to meet the requirement of spraying medium or low cost HVOF coatings for medium and small job shops. The deposited cermets coatings by the DZ9000E system have good performance with average micro hardness of over HVOF 2900 and the bond strength between coating and substrate of over 50MPa.
Characterization and Evaluation of Nanostructured Bond Coats from Noncryogenically Milled Feedstock
Authors: Kim G.E. , Addona T. , Richer P. , Jodoin B. , Al-Mathami A. , Brochu M.
Published: September 2022

Thermal barrier coatings (TBCs) with nanostructured bond coats have shown significant thermal cycling enhancements over their conventional microstructured counterparts; however, the high cost inherent to the cryomilling processing of the MCrAlY powder limits commercial application. Hence, this study characterizes and evaluates nanostructured bond coats derived from non-cryogenically milled MCrAlY powder with emphasis placed on reduced processing cost and scale-up capability. After extensive development of both a high-energy planetary mill and its operating parameters, fine-grained equiaxed NiCrAlY powder has been produced. XRD and SEM characterization of the milled powder will be presented. Microstructural analyses of the coatings sprayed via the HVOF and cold spray processes will also be carried out, in addition to some preliminary static oxidation test results of the conventional and milled NiCrAlY.
Influence of Annealing Treatment on the Photocatalytic Performance of the Nanostructured TiO2 Coating Deposited by Vacuum Cold Spray
Authors: Yang G.-J. , Li C.-J. , Fan S.-Q. , Zhang L.-Z. , Li C.-X. , Wang Y.-Y.
Published: September 2022

Composite powder in sub-micrometer size was prepared using a primary nano-TiO2 powder and polyethylene glycol (PEG). The nano-TiO2 coating was deposited through vacuum cold spray using both the composite powder and primary nano- TiO2 powder. The influence of annealing treatment on coating adhesion and photocatalytic activity was investigated. The coating adhesion was estimated through erosion test by water jet. The photocatalytic performance of the TiO2 coatings was evaluated through photodegradation of phenol in water. The results showed that annealing of the coating at a temperature from 450 to 500 °C yielded both higher activity and better adhesion. The adhesion of the coating deposited using the composite powder was better than that using primary nano- TiO2 powder. It was found that TiO2 coating resulting from the composite powder presented much higher activity than that deposited with primary nano-particles. The better activity is attributed to the existence of large pores resulting from the stacking of composite powder, which benefits the reactants transportation through the porous coating.
Influence of Silver Doping on Photocatalytic Activity of Liquid Flame Sprayed Nanostructured TiO2 Coating
Authors: Yang G.-J. , Li C.-J. , Huang X.-C. , Wang Y.-Y. , Li C.-X.
Published: September 2022

Silver ion was added to liquid feedstock to deposit Ag+ doping nanostructured TiO2 photocatalytic coatings through liquid flame spraying. The coating microstructure was characterized by X-ray diffraction (XRD). The photocatalytic performance of coatings was examined by photodegradation of acetaldehyde. XRD analysis showed that the phase structure of coatings was not significantly influenced by the silver ion doping. However, a shift was found for XRD peaks of anatase TiO2. The photocatalytic activity of the TiO2 coatings was increased and then decreased with the increase of dopant concentration. The photocatalytic activity of doping coatings was higher than that of pure TiO2 coating, in spite of dopant concentration. The enhancement of photocatalytic performance of doping coatings is attributed to co-doping of Ag+ ion and metallic Ag.
Deposition and Characterization of WC–Co Coatings Prepared by Continuous- and Pulsed-Cold Spray Processes
Authors: Yandouzi M. , Sansoucy E. , Richer P. , Jodoin B. , Ajdelsztajn L.
Published: September 2022

Due to their mechanical properties, WC-based cermet coatings are extensively used in industrial wear-resistant applications. These coatings are usually prepared using thermal spray processes. However, due to the nature/environment of the spraying processes, the feedstock powder structure and properties suffer from severe decomposition, which subsequently degrade the performance of the coatings produced. The cold spray process appears to be a promising process alternative to preserve the properties of the feedstock powder during the coating preparation. Although, the later technique can eliminate or minimize the degradation of the material, the deposition of cermet is a complex process. In this study, nanocrystalline WC-15Co and conventional WC- 10Co4Cr coatings were deposited using both the continuous and the pulsed cold spray processes. Microstructures of the feedstock powders and the coated layers were investigated by OM, SEM and XRD. The results revealed the possibility of depositing cermet coatings onto aluminum substrates by both processes without any degradation of the phase composition of the feedstock powder. However, the continuous process experienced difficulty in depositing and building up dense coatings without major defects. Meanwhile, the new pulsed process revealed the capacity of depositing thick cermet (conventional and nanocrystalline) coatings with low porosity as long as the feedstock powder was preheated above 573 K.
Reactive Plasma Spraying of Fine Feedstock Powders for Fabrication of Nitride Ceramic Coatings
Authors: Yamada M. , Kouzaki Y. , Yasui T. , Fukumoto M. , Takahashi K.
Published: September 2022

Aluminum nitride (AlN) and iron nitride (Fe4N) coatings were fabricated by reactive plasma spraying using fine feedstock powders. Reactive plasma spraying, in which element particles react with surrounding active species in the plasma, enables to fabricate nitride ceramics which decompose without stable melting phase. However, it is difficult to fabricate the coatings which include higher concentration of nitride phase by reactive plasma spraying using conventional particle size of feedstock powders. Therefore, fine feedstock powders were used in order to enhance the nitriding reaction during spraying. Aluminum or iron particles were injected into Ar/N2 plasma and were deposited onto graphite substrates. It was possible not only to increase the nitride phase content in the coatings but also to densify the microstructure in both materials. Thus, it became clear that using fine feedstock powders are useful for fabrication of nitride ceramic coatings by reactive plasma spraying.
Solution Precursor Plasma Spray (SPPS) of Ni-YSZ SOFC Anode Coatings
Authors: Coyle T.W. , Wang Y.
Published: September 2022

Although the deposition of Ni-YSZ anodes by plasma conventional spray is more successful than other SOFC components, the large NiO and YSZ particles used for the spray process, about 50-150 microns for high porosity coating deposition, reduce the density of three phase sites for electrode reaction. In this paper, the solution precursor plasma spraying (DCSPPS) process, in which solution precursors of the desired resultant materials are fed into a DC plasma jet by atomizing gas, was used to synthesize and deposit porous Ni-YSZ composite anodes. The deposition results show that several process parameters have significant effects on the microstructure and phase composition of the deposited material. The deposits were composed of tower-like, irregularly shaped agglomerates and splats. The sizes of the agglomerates increase with the decrease of the plasma torch power and most are not completely molten during the impact. The amount of splats is proportional to the power and they are much smaller than the agglomerates in volume. After heat treatment to reduce the NiO present in the as deposited coatings, the coatings were found to contain small spherical YSZ particles about 0.5 micrometers in diameter distributed in a continuous Ni matrix. The coatings have 29%-51% porosity depending on the process parameters.
Experimental and Numerical Studies of Plasma Forming Process Parameters Effect on Optimum Particle Impact Locations
Authors: Zhang W. , Sampath S. , Zheng L.L.
Published: September 2022

This paper investigated the role of particle injection on inflight particle behavior and its coupling effect on plasma plume in an external orthogonally injected air plasma spray system as well as effects of primary, secondary and carrier gases on in-flight particle status through both experiments and simulations. Diagnostic sensors such as In-flight Particle Pyrometer (IPP) and Spray Position Trajectory (SPT) have been used to obtain the plume characteristics and ensemble temperature, while DPV-2000 was used to measure the distributions of individual particle status such as temperature, velocity and size at the maximum particle flux point. Three-dimensional simulations have been carried out for the corresponding experimental conditions to examine the effects of in-flight particle heating on the plasma plume and in-flight characteristics at different spray distances. Both experiment and simulation results show that particle temperature and velocity will initially increase with plume angle and then decrease after reaching a maximum value for different combination of process parameters at the same plume angle. Theoretical analysis shows strong dependence of the plume angle on the velocity ratio of vertical component from the carrier gas to the horizontal one from primary and secondary gas at their respective nozzle exits. This study enables a better understanding of influence of plasma forming and stabilizing parameters on the particle in-flight characteristics.
Microstructure Control of NiO(Graphite)/8YSZ SOFC Anode Coatings by Atmospheric Plasma (APS)
Authors: Kwon O.C. , Lee C. , Hwang S.Y.
Published: September 2022

Anode layer, as the main site for the reaction of fuel and removal of byproducts, plays an important role in anode-supported solid oxide fuel cell (SOFC). Generally, high electrical conductivity and gas permeability (porosity) of the anode materials are required to reduce the polarization loss of SOFC. This study focuses on the manufacturing of porous anode layers for SOFC. The NiO/8YSZ cermets anode coatings are fabricated by atmospheric plasma spray (APS) using the blended powder of nickel coated graphite (Ni-graphite) after oxidation (NiO-graphite) and 8mol%Y2O3-stabilized ZrO2 (8YSZ). To increase the porosity and the uniformity of the coatings, nickel coated graphite with low density is used as the starting feedstock instead of the conventional pure Ni powder. To balance the conductivity (Ni), porosity (graphite), and structural stability (8YSZ) of the coatings, the effects of process parameters such as hydrogen (H2) gas flow rate, spraying distance, and pore formation precursor (carbon black addition) on the microstructures of resulting coatings by APS are investigated. The results show that the NiO/8YSZ anode coatings with high conductivity, structural stability and porosity could be deposited by APS with moderate H2 gas flow rate and short distance. The microstructure of the coating is mainly associated with the degree of melting of impact particles.
Operational Limitations of the iPro-90 Plasma Spray Gun
Authors: Rusch W.
Published: September 2022

Plasma spray torches for spraying internal diameters have typically been limited to 40 kW in the past. A new internal plasma spray torch has been developed with an operational power limit above 90 kW. This high power torch was primarily developed to decrease the spray time required to apply coatings to large inside diameters such as land based gas turbine components. This paper explores the factors effecting the operation of this torch as well as the functional limits of its operation. The factors investigated are gas flow, gas ratios, current, voltage, water flow, and water temperature. Thermal efficiency and plasma enthalpy are presented.
Evaluation of Tungsten Carbide Coatings Sprayed with High Velocity Plasma Using a Process Map
Authors: McCullough R. , Molz R. , Hawley D.
Published: September 2022

Process mapping is an ideal method for tracking coating characteristics in the thermal spray process. With the increased utilization of in-flight particle diagnostic tools in recent years it is now possible to quickly and effectively characterize inflight powder particle properties. With industries' increasing understanding of the relationship of these properties and coating characteristics, it is now possible to rapidly understand the implications of in-process changes with respect to coating performance. This paper is an exploratory exercise that describes the utilization of process mapping of in-flight particle velocity and temperature characteristics to optimize tungsten carbide (WC) coatings sprayed with a High Velocity Plasma torch (HVP). Key performance factors of WC coatings include high inherent hardness, low porosity and neutral to compressive stress conditions. The combination of these factors all contribute to the coatings' overall success in it's intended application and elude to its toughness, wear resistance, corrosion resistance and general ability to protect the required components. Presently, the High Velocity Oxygen Fuel (HVOF) and High Velocity Liquid Fuel (HVLF) combustion processes are the favored method of applying dependable and commercially viable WC coatings that meet all of these criteria.
Titanium Nitride Spraying Using Supersonic Nitrogen and Nitrogen/Hydrogen-Mixture Plasma Jets in Thermodynamic and Chemical Nonequilibrium State
Authors: Tahara H. , Ando Y.
Published: September 2022

In low-pressure plasma spraying, a plasma jet generator with a supersonic expansion nozzle is useful for spray coating hard and large-area films adhering strongly to substrates. In the expansion nozzle, the pressure and the electron density drastically decrease downstream, and therefore the plasma is in thermodynamic nonequilibrium state. Additionally, the supersonic expanding plasma jet is expected to be in chemical nonequilibrium state in which excited plasma particles are carried downstream in chemically-active state. In this study, titanium nitride (TiN) reactive spraying was carried out under a low-pressure environment using a DC arc plasma jet generator with a supersonic expansion nozzle. Titanium powders were injected using a hollow cathode with argon gas, and the plasma gas was nitrogen or nitrogen and hydrogen mixture. Microstructure and properties of the coatings were examined using scanning electron microscope (SEM) and X-ray diffraction (XRD). A dense and high-quality TiN coating with a Vickers hardness of 2000 was formed at a low substrate temperature of 700 °C with a low input power of 5.3 kW. All results showed that the supersonic plasma jet in thermodynamic and chemical nonequilibrium state had high potentials for reactive spraying.
Fuzzy Logic Analysis of Alumina–Titania Deposition Yield During APS Process
Authors: Kanta A.F. , Montavon G. , Planche M.P. , Coddet C.
Published: September 2022

The behavior modeling of Atmospheric Plasma Spray (APS) process requires a global approach which considers interrelated non-linear relationships between coating characteristics / properties in-service and process parameters (power, feedstock injection, kinematics, etc.). Such an approach would permit to reduce the development costs. To reach this objective, the knowledge of the interactions between process parameters plays a relevant role in the optimization. This work intends to develop a behavior model based on fuzzy logic concepts. Here, the model considers the deposition yield as the result of the process and it establishes relationships with power process parameter (arc current intensity, plasma gas total flow rate, hydrogen content) on the basis of fuzzy rules. The model hence permits to discriminate the role and the effects of each power process parameters. The modeling results are compared to experimental data. The specific case of the deposition of alumina-titania (Al2O3-TiO2, 13% by weight) by Atmospheric Plasma Spraying (APS) is considered.
Submicron α-Fe/Nylon-12 Composite Absorber Coatings Produced by Low Temperature High Velocity Air Fuel Spray Technique
Authors: Yuan X. , Wang H. , Hou G. , Zha B. , Jiang L.
Published: September 2022

In this paper, submicron α-Fe/nylon-12 microwave absorbing composite coatings were deposited by a Low Temperature High Velocity Air Fuel (LTHVAF) spraying technique. The microstructure and the electromagnetic parameters of coatings and powders were tested. The coatings are dense and have low porosity. The microwave reflectivity coefficient of the coatings was calculated with permeability and permittivity of the powders. It shows that there is a relationship between the mass fraction of composite powders and microwave absorption ability of coatings. At the threshold value, the composite coatings can absorb microwave strongly. When the coatings thickness increases, the minimal reflectivity coefficient moves to the low microwave frequency. There exists an appropriate coatings thickness in order to optimize the absorption of the microwave energy. The mass fraction and the thickness can affect the performance of composite absorber coatings.
Sliding Wear Properties of HVOF Thermally Sprayed Nylon-11 and Nylon-11/Ceramic Composites on Steel
Authors: Jackson L. , Ivosevic M. , Knight R. , Cairncross R.A.
Published: September 2022

The high velocity oxy-fuel (HVOF) combustion spray process has previously been shown to be a successful method for depositing pure polymer and polymer/ceramic composite coatings. Polymer and polymer-ceramic composite particles have high melt viscosities and require the high kinetic energy of HVOF in order to generate sufficient particle flow and deformation on impact. One of the goals of reinforcing polymer coatings with particulate ceramics is to improve their durability and wear performance. Composite coatings were produced by ball-milling 60 µm Nylon-11 together with nominal 10 vol.% of nano and multi-scale ceramic reinforcements and HVOF spraying these composite feedstocks onto steel substrates to produce semi-crystalline micron and nano-scale reinforced coatings of polymer matrix composites. The room temperature dry sliding wear performance of pure Nylon-11, Nylon-11 reinforced with 7 nm silica, and multi-scale Nylon-11/silica composite coatings incorporating 7 to 40 nm and 10 µm ceramic particles was determined and compared. Coatings were sprayed onto steel substrates, and their sliding wear performance determined using a pin-on-disk tribometer. Coefficient of friction was recorded and wear rate determined as a function of applied load and coating composition. Surface profilometry and scanning electron microscopy were used to characterize and analyze the coatings and wear scars.