bluuebunny/crossref_metadata_2025_split huggingface dataset:
Standardization in Quality Control of Thermal Spray Coatings
Authors: van Wonderen M. , Sauer J.P. 
Published: September 2022

Abstract
The goal of this work is to have standardized quality control of thermal spray coatings incorporated into the Standard Practices Manuals of all aircraft engine original equipment manufacturer’s around the world. With the many manufacturers’ criteria for evaluation of thermal spray materials, laboratories are forced to have multiple criteria/systems to test and analyze coatings. As airlines/repair shops are moving towards overhaul of more variable engine types/models in their shops, the need to have a common evaluation system has been identified and is currently being addressed. A sub-committee of the European Airline Committee for Materials Technology is currently working to formulate this common system for thermal spray coatings evaluation. Participants are from GEAE, Pratt & Whitney, Rolls Royce, SNECMA and KLM Royal Dutch Airlines. The progress and goals of this group will be documented and reported.
Evaluation of HVOF Coatings for Wear Applications
Authors: Lima C.R.C. , Camargo F. 
Published: September 2022

Abstract
The use of coatings to improve wear and corrosion resistance of mechanical components has been common for several decades. Various application techniques have been commonly used, including welding, cladding, electroplating, PVD (physical vapor deposition) and CVD (chemical vapor deposition). Thermal spraying has been found to be an interesting and viable alternative for those processes in such applications. Coatings of several types can be used for wear and corrosion protection, including situations when they are combined. The analysis for choice of the ideal coating and of the application process should take into account the environment and related limitations and specificities of each coating material and application process. In this work a study and characterization of tungsten and chrome carbides based coatings was carried out. The coatings were applied by high velocity oxy fuel thermal spraying (HVOF), using two different HVOF systems. Microstructure, hardness, as well as wear characteristics of the coatings were evaluated. The results show that the obtained coatings present great characteristics and can successfully face several wear conditions.
Modelling and Design of an Attachment to the HVOF Gun
Authors: Dolatabadi A. , Pershin V. , Mostaghimi J. 
Published: September 2022

Abstract
Although the HVOF process has shown to be a technological alternative to the many conventional thermal spray processes, it would be very advantageous to design a nozzle that provides improved performance in the areas of deposition efficiency, particle in-flight oxidation, and flexibility to allow coating of ceramic powders. Based on a numerical analysis, a new nozzle was modeled, designed, tested, and used to produce thermal spray coatings according to the industrial needs mentioned above. Performance of the new nozzle was investigated by spraying several coating materials including metallic (Nickel, MCrAlY, Stainless Steel), carbide (WC-Co), and ceramic (Al2O3) powders. Particle spatial distribution, velocity, and temperature corresponding to the new nozzle and the standard HVOF gun were compared. The new nozzle provides a superior particle spatial distribution, as well as higher and more uniform particle velocity and temperature.
High Velocity Oxygen/Air Fuel Spray
Authors: Wang Hangong , Zha Bailin , Su Xunjia 
Published: September 2022

Abstract
According to aerodynamics and thermodynamics, High Velocity Oxygen/Air Fuel Spray system was successfully developed. The system introduced stream atomization, high-pressure combustion chamber, converging/diverging nozzle, spark plug ignition, radial powder injection with reliable operation. The system has the function of both of HVOF and HVAF. It can not only use air and oxygen to spray respectively, but also the mixture of air and oxygen, so the velocity and temperature of the flame can be changed by adjusting the flux of air and oxygen. The system can produce high quality cermets, metal and alloy coatings for the adjustable of flame velocity and temperature.
Acoustic Emission as a Tool for Characterising HVOF-Sprayed WC-Co Coatings
Authors: Driver L.C. , Shipway P.H. , McCartney D.G. , Donohue L.A. , Rickerby D.S. 
Published: September 2022

Abstract
This research examined the use of 4-point bend testing, with in-situ acoustic emission analysis, for the characterization of the deformation of WC-Co coatings sprayed by the high-velocity oxy-fuel method. Coatings were deposited from WC- 17wt.%Co powders using a Praxair JP5000 system. Two sets of gun operating parameters were employed to produce coatings with distinctly different structures. In the present studies the cracking behaviour of the coatings was investigated through analysis of the acoustic emission (AE) data. In particular, AE data recorded has shown clear differences between the two coating types, in terms of the critical strain level and amount of energy released during cracking. The critical strain levels for the different coatings were 0.32% and 0.6% respectively. Analysis of the coatings by scanning electron microscopy and X-ray diffraction has allowed correlations to be made between the principle microstructural features of the coatings and the mechanical behaviour under bending. The AE responses for these cermet coatings were highly reproducible.
Property Evaluation of HVOF-Sprayed Magnetic Thick Films
Authors: Ma X. , Ge S. , Zhang T. , Zhang Y. 
Published: September 2022

Abstract
Spinel soft ferrites such as NiZnFe2O4 are of great interest due to their extensive applications in magnetic-optics, microelectronics, and microwave devices. This study deals with the production of thick Ni0.5Zn0.5Fe2O4 magnetic films (&gt;50 microns) using high velocity oxy-fuel (“HVOF”) thermal spray. With the HVOF process, high density films more than 98% theoretical density were prepared, apparently due to the high velocity of droplets in the process. The influence of the fuel composition on coating structure, deposition efficiency, and magnetic properties of the Ni-Zn ferrite films was investigated. Better magnetic properties were obtained in the as-sprayed film formed with a neutral or oxygen-rich flame. The decomposition of the ferrite material occurred with a fuel-rich flame and resulted in a reduction in magnetic properties. However, the magnetic properties could be improved dramatically after heat treatment. Pellet and toroid samples of these films were produced for evaluation of magnetic properties by saturation magnetization and magnetic permeability. The permeability exhibited a very flat response to high frequencies up to 13 MHz.
Coating Formation by Impact of Molten Metal Droplets with Uniform Size and Velocity
Authors: Dhiman Rajeev , Chandra Sanjeev 
Published: September 2022

Abstract
The adhesion of splats formed by impact of molten metal droplets was studied experimentally. Tin droplets (550 µm diameter) were produced using a drop-on-demand generator. To achieve high impact velocities the stainless steel coupons used as substrates were mounted on the rim of a rotating flywheel and heated using cartridge heaters. To hit a falling droplet with the substrate and photograph its impact, a timing circuit was used to synchronize three events with the position of the substrate: ejection of a droplet, triggering of the camera and a flash to provide illumination. The impact velocity was varied from 10 – 40 m/s whereas the substrate average roughness (2.0 µm) and the droplet diameter (~550 µm) were kept constant. We measured the adhesion strength of splats by a simple pull test. A wire was attached to the upper surface of each splat using epoxy and the force required to separate the splat from the substrate was recorded. A significant increase in adhesion strength was observed as the impact velocity was increased. Coatings were produced by depositing many droplets sequentially. Substrate temperature and impact velocitiy were the main parameters varied. SEM images of cross-sections through coatings showed that increasing impact velocity and substrate temperature produced better adhesion between the coating and substrate.
Splat Profile of Impinging Droplets on Rough Substrates
Authors: Amada S. , Imakawa I. , Aoki S. 
Published: September 2022

Abstract
Thermal sprayed coatings are influenced by the wettabillity of the molten particles to substrates. The contact angles of several molten metal droplets are measured in air and vacuum. The flattening ratio is evaluated by taking into account of wettability. Comparing with the experimental data of the freefall droplet, it was concluded that the wettability to the roughened substrates influenced on the flattening characteristics.
Modeling Residual Stress Build-Up in the Coating Microstructure
Authors: Ghafouri-Azar R. , Chandra S. , Mostaghimi J. 
Published: September 2022

Abstract
We used an object oriented finite element numerical method to examine residual stress build-up in a simulated crosssection of coating. The cross-section image of coating was the result of simulation produced by a 3-D stochastic model of thermal spray coatings, which model features of coating microstructure including internal pores and surface roughness. An adaptive meshing technique was used to fit a grid in a section through the simulated coating, and stresses in the coating calculated using a finite element method. The results showed that stresses are sensitive to the thickness and roughness of the coating.
Model of Thermal Spraying Using a Monte-Carlo Approach
Authors: Zhang T. , Liu B. , Bao Y. , Gawne D.T. 
Published: September 2022

Abstract
The motion and heating of a single particle in a plasma jet is strongly influenced by the feedstock injection conditions and can be predicted using computational modelling as described in the literature. In practice, however, the size and initial velocity of a given particle are essentially random variables within the fairly wide limits of the injected feedstock population. This is compounded by the non-uniformity of the plasma jet. As a result, the motion and heating of particles take on a substantial random element. There are three independent variables that jointly affect the particle motion and heating in a given jet: the diameter, the radial coordinate and the azimuthal angle of a particle. Nevertheless, these parameters cannot be specified for every particle in the jet in a deterministic manner owing to the above complexities and so a simulation based on a single particle cannot provide a realistic prediction of the deposition process. In the present study, the random element present in practical spraying is simulated using a Monte-Carlo approach. The distributions of the motion and heating of a population of particles are simulated rather than those for a single particle. The statistical method presented in this paper gives more detailed information on the effects of processing parameters and the assessment of process quality. The results show that this is able to provide a more accurate means of simulating the thermal spraying process.
Plasma Spraying Flow Modeling: Generation of the Plasma Column and Turbulent Flow into a Dense Atmosphere
Authors: Guenadou D. , Meillot E. 
Published: September 2022

Abstract
This paper presents the numerical simulation of the plasma flow into a dense atmosphere. The plasma generation is performed by the simple model developed by Eichert. Two models are exposed to take in account the arc fluctuation inside the anode. They permit us to simulate plasma puffs convected into the flow. The aim of this study is to compare these two models with experiments and to determine which one is the most relevant.
On the use of SYSWELD and PHOENICS for the Computation of Heat Transfer in a Substrate Exposed to an Impinging Plasma Jet
Authors: Li J. , Bolot R. , Liao H. , Coddet C. 
Published: September 2022

Abstract
The study of heat transfers in a substrate exposed to an impinging plasma jet is proposed using two different software products. Thermal exchanges between the plasma jet and the substrate were first calculated using the PHOENICS CFD software in which a two-layer extension to the Chen-Kim k-s model was implemented in order to consider both the turbulent nature of the plasma jet and heat transfer phenomena through the viscous sub-layer formed at the surface of the substrate. The model is supposed to provide accurate predictions of thermal exchanges. However this preliminary step is not described since it is part of some previous studies. In a second step, two different commercial software products are used to perform three dimensional transient calculations of the heat conduction inside the substrate. The first approach consists in the use of the finite element based SYSWELD software whereas the second one consists in the use of the finite volume based PHOENICS software. Numerical results are presented and compared for the case of an impinging plasma jet displacing linearly on the substrate. Additionally, the influence of different parameters such as the substrate sample thickness, the stand-off distance, the displacement velocity or the nature of the substrate is also discussed. The results show a good accordance between numerical predictions obtained using the two methods concerning the maximum temperature observed. These results are useful since the substrate temperature is known to have an important influence on the coating adhesion and properties.
Turbulence Modeling of Inductively Coupled Plasma Flows
Authors: Xue S. , Proulx P. , Boulos M.I. 
Published: September 2022

Abstract
Various turbulent models (Spalart-Allmaras, Standard k-ε, RNG k-ε, Realizable k-ε and Reynolds Stress Models) along with Standard, and two-zonal wall functions are used to simulate inductively coupled plasma flows. The computational results can be classified into two categories: All the turbulent models that include low Reynolds number effects, such as, Low Reynolds number k-ε model, Spalart-Allmaras one-equation model, Standard k-ε model with two-zonal wall function, RNG model with turbulent viscosity determined by a differential equation, RSM etc., give similar modelling results. These models predict almost the same temperature contours which are similar to the one predicted by laminar model. The viscosity ratios in plasma region predicted by these models are very close to zero except for in the wall-neighbouring cells, which means the plasma flow is almost laminar. The other category contains those models that do not include the low Reynolds number effects, such as Standard, RNG and so-called Realizable k-ε models with standard wall function. They predict the plasma flow to be turbulence-dominated. In comparison with the results of experimentally measured heat fluxes to a substrate, the heat fluxes predicted by these models that include low Reynolds number effect are very close to experimental measurements while these models that do not include low Reynolds number effects deviate greatly from experimental measurements. It is found that the Reynolds stress model(RSM) appears to be the best predictive model.
Diagnostic of Supersonic High Frequency (HF) Plasma Flow
Authors: Léveillé V. , Boulos M.I. , Gravelle D.A. 
Published: September 2022

Abstract
In this study, two complementary techniques of diagnostic are used to study the properties of a supersonic HF plasma flow: namely, an enthalpy probe measurement and a flow visualization. A PL-35 induction plasma torch operating with three convergent-divergent Laval-type nozzles generates the plasma: a Mach 3.0 velocity water-cooled (wc) nozzle, a Mach 1.5 velocity wc nozzle and a Mach 2.45 velocity radiation-cooled (rc) nozzle. The plasma plate power is fixed at 20 kW and chamber pressure varies between 1 and 10 kPa. The plasma gas is argon and its flow is fixed at 60 slpm. The enthalpy probe profiles of local enthalpy and stagnation pressure are measured, from which, temperature, velocity and Mach number are obtained. The effect of nozzle design on plasma properties is investigated. The RC nozzle creates a plasma jet hotter with a steeper thermal profile and a higher mean velocity than the wc nozzle. The enthalpy probe calculations imply the assumption that the static pressure of the flow is similar to the chamber pressure. Experimental results show that this assumption is still applicable in the jet fringes, but its value changes strongly along the radial and axial axis. Also, photographs of the oblique shock wave in front of a cone in the plasma flow allow the approximation of the flow Mach number produced by a Mach 1.5 velocity wc nozzle. Its approximate value is 2.0, which is higher than predicted.
Modeling of Transport and Evaporation of Liquid Droplets Sprayed into RF-ICPs
Authors: Shan Y. , Mostaghimi J. 
Published: September 2022

Abstract
Study of the injection of liquid sprays into thermal plasmas has a number of important applications. Examples include Thermal Plasma Chemical Vapor Deposition (TPCVD), hazardous waste destruction and, ICP atomic emission or mass spectrometry in analytical chemistry. The spray is comprised of thousands of single liquid droplets. To calculate the mass, momentum and energy exchange between the gas and the spray, one must account for a distribution of droplet sizes, velocities, and temperatures. For some cases, droplet collision and breakup also are important. This paper developed a model for the transport and evaporation of liquid droplets sprayed into an radio frequency inductively coupled plasma (rf-ICP). The model considers the evolution of spray distribution function as the liquid spray travels through the discharge. Coupling calculations between plasma gas and water spray is performed for a typical rf-ICP torch. This model is capable of predicting the thermal and dynamic behavior of the liquid spray and its effects on the plasma gas for different rf-ICP operating conditions.
Substrate Melting During Thermal Spray Splat Quenching: Case Study for Molybdenum Droplets on Various Substrates
Authors: Li L. , Wang X.Y. , Vaidya A. , Sampath S. , Wei G. , Zhang H. 
Published: September 2022

Abstract
Molybdenum powder has been plasma sprayed on stainless steel, brass and aluminum substrates. The substrate melting phenomenon is observed and investigated by means of scanning electron microscopy (SEM) and scanning white light interferometery (SWLI). It is found that the flower-shape splat morphology is typical for molybdenum on all three substrate materials when the substrate is at room temperature. Notable substrate melting is manifested through the energy dispersion analysis of X-ray (EDAX) map and Robinson back-scattered image of cross-sections of splats. It has been shown that the substrate material plays an important role in substrate melting phenomenon. The lift angle of the petals of splats and the maximum crater depth have been characterized and compared. Both of these increase in the sequence, from stainless steel, brass to aluminum. A ‘volume of fluid’ (VOF) based model coupled with rapid solidification has been used to simulate splat deformation, solidification, substrate melting and resolidification. The numerical & analytical results agree quite well with the experimental data. A substrate melting mechanism is proposed based on the time scales of the droplet solidification and substrate melting to explain the formation of flower like splat morphologies.
Polymerlike C:H Thin Film Coating of Nanopowders in Capacitively Coupled RF Discharge
Authors: Kouprine A. , Gitzhofer F. , Boulos M. , Fridman A. 
Published: September 2022

Abstract
Nanopowders of amorphous SiO2, with typical particle sizes of 30-80 nm, were treated under non-equilibrium plasma conditions created by a capacitively coupled (CC) RF discharge in pure methane or ethane. The gas flow rate was varied between 0.02-0.06 slpm, with reactor pressures maintained between 1000 and 5000 Pa, and applied RF power inputs between 700 and 1500 W. The plasma properties were monitored through measurements of the C2 rotational and the atomic hydrogen excitation temperatures. The compositions of the gases that passed through the plasma were analyzed by mass-spectrometry. In spite of the evidence indicating the presence of CnH2n+2 and CnH2n (n=1-3) species, as well as acetylene, in the discharge, the homogeneous formation of soot was not observed. At the same time, introduced nanoparticles acted as centers for the inception and growth of C:H thin coatings in the form of polymer-like hydrocarbon layers, whose thickness lay between &lt; 5 - 30 nm. The results of TEM, IR spectroscopy, thermo-gravimetric and precision calorimetric analyses performed on the plasma treated powders provided evidence for the formation of an amorphous, high density C:H matrix on particles' surfaces.
Correlations Between Processing Parameters, Coatings Properties and In-Flight Particle Characteristics
Authors: Guessasma S. , Montavon G. , Coddet C. 
Published: September 2022

Abstract
The reproducibility of the coating properties is the result of an efficient control of the thermal spray process. Actually, it is not possible for the sprayer to guarantee the temporal reproducibility of the coating properties without online control. However, adjusting the system fluctuations with regards to the temperature, velocity and size of particle could alter some properties that depend or not on the in-flight particle characteristics. This study aims at discussing the existing correlations between the processing parameters and the coating properties established with a Neural Network methodology. It demonstrates the segmentation of the correlations by comparing the result of the merging procedure of two sub-network structures and the direct correlation from the processing parameters to the coating properties. The sub-structures are built considering respectively the in-flight particle characteristics relationship with the operating conditions and the in-flight particle characteristics relationship with the coating properties.
Investigations of In-Flight Particle Characteristics Through DPV Measurements and Correlation with Impact Analysis and Coating Properties
Authors: Planche M.P. , Lakat A. , Liao H. , Coddet C. 
Published: September 2022

Abstract
While twin wire arc spraying, strong dependences are usually noticed between elaboration process parameters and coating properties. Therefore, control is needed for increasing coating performances. The aim of this paper is to investigate the coating properties in relation with in-flight particle characteristics and with the impact modes. Measurements were achieved on iron particles when changing either the current intensity or the air flow rates. In-flight particle characteristics were determined by using the DPV diagnostic system 200 mm from the gun exit and for three different radial locations. The same locations were kept for the impact analysis. Then, the morphology of the splats was evaluated by its flattening and shape factors when the substrate is preheated or not. Finally, the coating properties were characterized in terms of porosity, oxide contents, microhardness and thickness. Through the determination of related interactions, a better knowledge of coating elaboration conditions will lead to improve reliability and properties of the deposits.