bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Modeling Approach of DC Arc Plasma Flows by Implementation of the CFD Phoenics Code
Authors: Eichert P. , Coddet C. , Imbed M. 
Published: May 2021

Abstract
This paper is devoted to the presentation of a modeling approach of DC arc plasma flows by implementation of the CFD PHOENICS code. The equations of mass, momentum and energy, of elliptic type, are discretized using a finite/control volumes method. The closure of the equations set is obtained with the standard k-ε turbulence model. Finally, the algebraic equations set is solved by means of the SIMPLE algorithm. 3D calculations are performed from the point of the cold gas injection into the torch to the plasma ejection into the surrounding atmosphere, taking into account some currently used spray parameters (i.e., plasma gas flow rate, power, etc.). Results are discussed and compared with experimental values taken from the literature.
Voltage and Current Fluctuations in Wire Arc Spraying as Indications for Coating Properties
Authors: Watanabe T. , Wang X. , Heberlein J. , Pfender E. , Herwig W. 
Published: May 2021

Abstract
Electric arc spraying with dual wires is an economical coating process finding diverse applications. Turbulence and velocity of an atomizing gas exert strong effects on the droplet formation and therefore on the coating properties. Turbulence intensity of an atomizing gas flow can be estimated by analysis of the waveforms of arc voltage fluctuations, and the velocity can be estimated by the frequency and the amplitude of these waveforms. Higher gas velocities result in higher frequencies and smaller amplitudes of the voltage fluctuations, and in smaller molten droplets leading to coatings with lower porosity but higher oxidation levels. Lower turbulence levels at the electrode tips result in more periodic waveforms with less high frequency content, and in lower oxidation of the coatings. Nozzle configurations such as a converging-diverging nozzle provide higher gas velocities with less turbulence leading to coatings with lower oxidation and lower porosity.
Coating Thickness Prediction and Robot Trajectory Generation of Thermal Sprayed Coatings
Authors: Nylén P. , Fransson I. , Wretland A. , Mårtensson N. 
Published: May 2021

Abstract
Off-line programming (OLP) techniques can be used to reduce programming time and to be able to better control process parameters, such as spray distance and nozzle orientation. This paper presents a simulation method to predict coating thickness build-up on complex geometries. Discretization in time and space is done by using a finite difference model. The model starts with an empirical deposit rate function, which calculates the thickness on a flat surface normal to the spray cone. This model is integrated into a commercial robot simulation program (IGRIP) where discretization of a free form surface into planar polygons is carried out. The thickness is then calculated by stepping the process in increments of time. A robot trajectory is calculated, maintaining spraying distance and normal orientation to the surface. This trajectory is optimized numerically giving a collision free path and a uniform coating thickness. Devices are then programmed, the programs are translated and finally downloaded to the robot controller.
A Complete Predictor Methodology for the Plasma Spray Process
Authors: Varacalle D.J. , Barnett K. 
Published: May 2021

Abstract
To enhance usage of the plasma spray process, a better physical understanding of the process is required, which entails a synergistic mix of analytical and empirical studies. Better understanding can lead to development of optimal thermal spray coatings for future applications. This study presents an analytical method that can be used for these purposes. Experimental and analytical studies were conducted to investigate gas, particle, and coating dynamics and the resulting coating properties in the plasma spray process for the Tribaloy 800 powder system. Historical full-factorial statistically designed experiments were the basis for the analytical-experimental comparisons. The thermal plasma produced by a commercial plasma spray torch was then numerically modeled from the electrodes to the standoff distance in the free plume for sixteen experiments. This information was then used as boundary conditions to solve the plasma/particle interaction problem for the experiments. The predicted temperature and velocity of the droplets at the spray distance were then used as initial conditions to a coating dynamics code. Multiple polynomial regression analysis was then used to establish the sequential relationship between the process parameters (i.e., power, total flow, hydrogen flow), the coating properties (porosity, oxides), and the coating mechanical performance properties (tensile strength, microhardness, superficial hardness). The equations derived from the regression analysis were used to construct a predictor code for the process. The code predicts the process and coating attributes reasonably well. The predicted coating properties exhibit excellent correlation with the actual properties obtained from the experimental studies in the range of the parameter settings.
The Effect of Spray Distance and Chemistry on Pore and Crack Development in Plasma Sprayed Ceramic Deposits
Authors: Ilavsky J. , Long G.G. , Allen A.J. , Herman H. , Berndt C.C. 
Published: May 2021

Abstract
The porous microstructure of plasma-sprayed deposits prepared from gray-alumina feedstock and from two different yttria-stabilized zirconia (YSZ) feedstocks were studied as a function of spray distance. For each material, the behavior of the two major void systems—intralamellar cracks and interlamellar pores—was investigated. The results offer the first proof that the quantity and the character of the porosity in these materials can be controlled independently by selecting the appropriate processing protocols.
Microstructure and Properties of Thermally Sprayed TiC-Ni and (Ti,Mo) C-NiCo Coatings
Authors: Vuoristo P. , Stenberg T. , Mäntylä T. , Berger L.-M. , Nebelung M. 
Published: May 2021

Abstract
Hardmetal-like coatings on the base of titanium carbide as a hard phase and nickel as a metal binder were prepared from agglomerated and sintered powders by plasma spray, detonation gun spray and high-velocity oxygen-fuel spray processes. The powders used in the spray experiments were plain TiC-Ni type and alloyed (Ti,Mo)C-NiCo type powders with different binder content. The coatings were characterized by optical and scanning electron microscopy, microhardness measurements, XRD analysis and in an abrasion wear test. The results showed that the sprayability of these novel hardmetal-like powders is good in all spray processes studied and the coatings deposited were found to have dense microstructures and good properties. The XRD analysis showed that the coatings have a phase structure similar to that found in the spray powder. The amount of retained carbides in the coatings was high. Some regions in which the carbides had dissolved with the metallic binder phase during spraying were also found, especially in plasma sprayed coatings. In such microstructural regions submicron size reprecipitated carbides were detected. These were clearly detectable in detonation gun sprayed coatings. HVOF sprayed coatings were found to contain a very high content of retained carbide phase. In this process the heat effect to the material seemed to be the lowest. The wear tests clearly showed the importance of alloying the hard phase and the binder phase in order to improve the wear resistance of the coatings. All studied spray processes produced coatings with nearly similar coating wear properties.
The Structure and Thermal Properties of Plasma Sprayed Beryllium for the International Thermonuclear Experimental Reactor (ITER)
Authors: Castro R.G. , Bartlett A.H. , Elliot K.E. , Hollis K.J. 
Published: May 2021

Abstract
Plasma spraying is under investigation as a method for in-situ repair of damaged beryllium and tungsten plasma facing surfaces for the International Thermonuclear Experimental Reactor (ITER), the next generation magnetic fusion energy device, and is also being considered as a potential fabrication method for beryllium and tungsten plasma-facing components for the first wall of ITER. Investigators at the Los Alamos National Laboratory's Beryllium Atomization and Thermal Spray Facility have concentrated on investigating the structure property relationship between the as-deposited microstructures of plasma sprayed beryllium coatings and the resulting thermal properties of the coatings. In this study, the effect of the initial substrate temperature on the resulting thermal diffusivity of the beryllium coatings and the thermal diffusivity at the coating/beryllium substrate interface (i.e. interface thermal resistance) was investigated. Results have shown that initial beryllium substrate temperatures greater than 600°C can improve the thermal diffusivity of the beryllium coatings and minimize any thermal resistance at the interface between the beryllium coating and beryllium substrate.
Stereological Characterization of the Apparent Void Content of Thermal Spray Deposits
Authors: Montavon G. , Coddet C. 
Published: May 2021

Abstract
Properties and characteristics of a material depend mainly upon its morphological structure. In the case of plasma sprayed deposits, the properties (i.e., mechanical, thermal, electrical, etc.) are especially related to the deposit void content. Voids are coming from pores, cracks and delaminations. Implementing image analysis and stereological protocols, the apparent void content (AVC) of a vacuum plasma sprayed deposit was studied, in terms of the pore size distribution and spatial distribution. Results were compared with data obtained implementing water immersion porosimetry. This study showed on the one hand that the pore size distribution is described by a bimodale function, and, on the other hand, that pores are spatially distributed evenly within the deposit (isotropic distribution). In such a condition, the stereological protocol can be implemented on a single random plane section of the deposit.
A Comprehensive Approach for Advancing Plasma Spray Processing Technology
Authors: Sampath K. , Onesto E.J. 
Published: May 2021

Abstract
A comprehensive approach is presented for facilitating the implementation of advanced plasma spray processing technology in the manufacture, repair, and refurbishment of industrial components. This approach employs an integrated methodology for combining several advanced computer-based methods, including: 1) an interactive multimedia-based education and training tool to effectively store and retrieve plasma spray processing information in a variety of formats; 2) an expert system to select plasma spray feedstock material for a specific coating function; 3) a one-dimensional plasma spray process model that allows simulation of plasma spray processing conditions for identifying operational envelopes for a selected feedstock material; 4) an interface fracture model for identifying appropriate acceptance criteria for reduced cracking along the coating/substrate interface; and 5) a set of computer-based nondestructive test methods for performing quality assurance and control. This comprehensive approach and the integrated methodology provide an advanced engineering tool for the selection, optimization and implementation of specific advances in plasma spray processing technologies. A major outcome is the reduced need for expensive and time-consuming trial-and-error methods in evaluating the application of plasma spray coatings for the manufacture, repair, and refurbishment of specific industrial components. This comprehensive approach and integrated methodology can be extended to include other thermal spray processing technologies as well.
An Investigation of the Electrical Behavior of Thermally Sprayed Aluminum Oxide
Authors: Swindeman C.J. , Seals R.D. , Murray W.P. , Cooper M.H. , White R.L. 
Published: May 2021

Abstract
Electrical properties of plasma-sprayed aluminum oxide coatings were measured at temperatures up to 600 °C. High purity (&gt;99.5 wt% pure Al2O3) alumina powders were plasma-sprayed on stainless steel substrates over a range of power levels, using two gun configurations designed to attain different spray velocities. Key electrical properties were measured to evaluate the resultant coatings as potential insulating materials for electrostatic chucks (ESCs) being developed for semiconductor manufacturing. Electrical resistivity of all coatings was measured under vacuum upon heating and cooling over a temperature range of 20 to 600 °C. Dielectric constants were also measured under the same test conditions. X-ray diffraction was performed to examine phase formation in the coatings. Results show the importance of powder composition and careful selection and control of spray conditions for optimizing electrical behavior in plasma-sprayed aluminum oxide, and point to the need for further studies to characterize the relationship between high temperature electrical properties, measured plasma-spray variables, and specific microstructural and compositional coating features.
Fatigue Strength of Ceramic-Coated Steel at Elevated Temperature
Authors: Sonoya K. , Tomisawa Y. 
Published: May 2021

Abstract
Low cycle fatigue tests were performed at room temperature (RT) and at 673 K for l%Cr-0.5%Mo steel comparing the specimens coated with chromium carbide by gas spraying and the ordinary uncoated specimens, and the mechanism of fatigue crack formation was investigated. Following observations and conclusions were made: (1) When sprayed with ceramic, the fatigue life suffers reduction at either temperature, but at 673 K, the degradation was so much smaller than that at RT that the fatigue life was actually, though slightly, longer than that at RT. (2) The cracks are initiated in the ceramic layer very early in the whole fatigue life, the crack initiation lifetime becoming the longer, the smaller the strain range. (3) The fatigue failure process can be viewed as comprising following steps: first, early initiation of fatigue crack at the surface of the ceramic coating, rapid propagation through it to the substrate metal, and initiation of crack in the metal, the initial rate of propagation of such a crack being a number of times (perhaps as much as one full order of magnitude) faster than that in uncoated steel.
Residual Stress in Net-Shape Plasma Sprayed Tubes: Measurement, Modeling and Modification
Authors: Bartlett A.H. , Castro R.G. 
Published: May 2021

Abstract
Residual stresses in net-shaped plasma sprayed tubes was measured by X-ray microdiffraction, as a function of radial position in the sample. A tensile to compressive hoop stress profile was measured, ranging 200 MPa in tension at the outer diameter, to ~125 MPa at the inner. A force balance model was used to explain the evolution of stresses when incrementally adding layers to the pre-existent material.
Effects of Powder Morphology, Microstructure, and Residual Stresses on Thermal Barrier Coating Thermal Shock Performance
Authors: Wigren J. , de Vries J.-F. , Greving D. 
Published: May 2021

Abstract
Thermal barrier coatings are used in the aerospace industry for thermal insulation in hot sections of gas turbines. Improved coating reliability is a common goal among jet engine designers. In-service failures, such as coating cracking and spallation, result in decreased engine performance and costly maintenance time. A research program was conducted to evaluate residual stresses, microstructure, and thermal shock life of thermal barrier coatings produced from different powder types and spray parameters. Sixteen coatings were ranked according to their performance relative to the other coatings in each evaluation category. Comparisons of residual stresses, powder morphology, and microstructure to thermal shock life indicate a strong correlation to thermal barrier coating performance. Results from these evaluations will aid in the selection of an optimum thermal barrier coating system for turbine engine applications.
Repair of Water Turbine Blades by Wire Electric Arc Spraying
Authors: Musil J. , Dolhof V. , Dvorácek E. 
Published: May 2021

Abstract
Water turbine parts damaged by cavitation erosion (CE) and/or slurry erosion (SE) may cause excessive operational costs for plants worldwide. The damages can be reduced by choosing more resistant materials and right technology in the first-production or at repair and overhaul. Thermal spray technologies have a great potential in the field of repairing works. Thick multilayered coatings deposited by wire electric arc spraying (WAS) has been developed and applied as CE and SE protection at the repair of stationary Francis turbine blades. Repair technology by WAS was performed on large eroded areas (1-3 m3) of preguide blades of Francis turbine: 1) local damaged depths 30-35 mm maximum were repaired by sprayed materials, 2) subsequently wire arc spraying of functional coating was applied. Three types of functional coatings with total thickness 10 mm a) duplex high - Cr stainless steel with NiAl bond coat, b) graded NiAl - Cr stainless steel coatings, and c) multilayered graded NiAl - Cr stainless steel coatings were compared by means of stress measurements and structural analysis. The coating structure influences very strongly the residual stress level and adhesive-cohesive strength. Multilayered graded NiAl - Cr stainless steel coatings showed the best results and were sprayed on water turbine blades in 4 Czech water power station during regular cut-off repair periods. After 30 - 36 months' continuous operation, Francis turbine blades repaired by WAS technology show better behaviour in comparison with original material from the point of wear resistance, reliability, cost-effect and life-time.
Modeling and Characterization of Residual Stresses and Microstructure in Thermal Barrier Coatings after Plasma Spraying
Authors: Persson C. , Bengtsson P. , Wigren J. , Greving D. 
Published: May 2021

Abstract
Thermal barrier coatings with a zirconia top coating and a NiCoCrAlY bond coating were plasma sprayed onto a nickelbase alloy. The pre-heating of the bond coated substrates and the cooling during the top coating spraying were varied to produce five different spray sets. A finite element model was developed to predict the heat transfer and the resulting thermal stresses during the spraying. A layer removal technique was used to measure the residual stresses in the as-sprayed samples. The measurements revealed low residual stresses in the top coatings and tensile stresses in the order of 150 MPa in the bond coating. A correlation between the measured top coating residual stresses and the substrate temperature in the end of the top coating spraying was found. In general, good agreement between modelled and measured residual stresses was found. The top coatings were found to contain vertical microcracks and the densities of the cracks were point-counted in the spray sets. A slight increase in microcrack densities was found as the spraying was performed onto a colder substrate. The densities of vertical microcracks were correlated to modelled in-elastic strain in the top coatings.
Nondestructive Characterization of Plasma Sprayed Coatings by Laser Ultrasonics
Authors: Viens M. , Drolet D. , Blouin A. , Monchalin J.-P. , Moreau C. 
Published: May 2021

Abstract
Nondestructive methods previously developed for the detection of flaws, such as delaminations, or for the evaluation of the elastic properties of materials, could be judiciously adapted in order to get a better assessment of plasma-sprayed coatings. Laser ultrasonics is a nondestructive evaluation method which relies on both optics and ultrasonics. A short-pulse laser generates an ultrasonic wave into the material to be inspected, and a long-pulse laser, coupled to an interferometer, detects the resulting ultrasonic displacement. Laser ultrasonics is a remote sensing method and therefore could be used for the monitoring of hot plasma-sprayed coatings during the deposition process. In this work, experiments were performed on samples composed of ZrO2 sprayed under different conditions onto thick copper substrates. The samples were first probed by conventional ultrasonic transducers and then by a non contact laser-ultrasonic scanning system. The two series of measurements agreed well. These experiments showed that, after calibration, the coating thickness could be measured during the deposition process, with a relatively good accuracy, by laser ultrasonics. The laser-ultrasonic scanning system also revealed non uniformity of more than 10% in the coating thickness of the tested samples. This thickness variation is possibly caused by a temperature gradient induced in the coatings during spraying.
Plasma Spraying of Self-Lubricating Cr2O3-CaF2 Coatings
Authors: Vos F. , Delaey L. , De Bonte M. , Froyen L. 
Published: May 2021

Abstract
Results are presented of a project analysing the relationship between the production parameters of plasma sprayed self-lubricating Cr2O3-CaF2 coatings and their structural, wear and lubricating properties. The production method consists of a preparation step where a powder blend of the matrix material (Cr203) and solid lubricant (CaF2) is agglomerated, followed by atmospheric plasma spraying (APS) of the agglomerates. Selection of the most appropriate agglomeration and plasma spray parameters as well as the microstructure of the coatings will be discussed.
Thermal Shock Resistance of Plasma Sprayed Tungsten Coatings
Authors: Urquiaga Valdes M. , Saint-Jacques R.G. , Moreau C. 
Published: May 2021

Abstract
Plasma sprayed tungsten coatings are considered as potential candidates for materials in contact with the plasma in future fusion reactors. In this work, the thermal shock resistance of these coatings is studied to determine which of five changed deposition parameters most influences the coating's performance. The thermal shocks were generated with a pulsed electron beam gun. The pulse duration was 0.2 and 0.5 s and the absorbed power density 60 MW/m2. Two series of samples were analyzed. One was plasma sprayed at atmospheric pressure (AP) and the other at low pressure (LP). The LP coatings were deposited on a molybdenum alloy (TZM). AP coatings were deposited on molybdenum and on water cooled copper coupons for fatigue tests. The porosity seems to be a positive factor for thermal shock resistance. The thickness of the coatings and the spraying atmosphere were found to strongly influence the thermal shock resistance. In the case of the fatigue test, some coatings withstood up to 1000 shocks of 0.5 s duration.
Technology Transfer
Authors: Naisbitt G. , Alderton T. , Bruce C. 
Published: May 2021

Abstract
High Velocity Oxy Fuel, (HVOF), is a high energy Thermal Spraying Combustion Process, producing high density coatings with hardness values in excess of 1200 VPN. Such coatings, using metal carbide spray material, are used extensively in the aerospace industry, in areas where high wear resistance is particularly important. The Linde Detonation Gun, CD-Gun'), has until recent times been the predominant system for applying these hard faced coatings. However, the advent of a number of new HVOF systems approximately 5 years ago, allowed Gas Turbine Repair and Overhaul bases the opportunity to offer a more competitive coating service, i.e. these "1st generation" HVOF systems allowed the development of comparable, if not superior coatings to these produced by the D-Gun. Having successfully developed and approved HVOF coatings for the use on Rolls-Royce Gas Turbine components for both Repair and New Manufacture, Rolls Wood Group addressed the problem of transferring HVOF technology from aerospace components to alternative markets, i.e. refurbishment of equipment used in Oil and Gas Production.