bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Benefits of the PROTAL Process on the Adhesion of Thermal Sprayed Coating
Authors: Barbezat G. , Folio F. , Coddet C. , Montavon G. 
Published: July 2021

Abstract
In this paper, the authors evaluate the effect of different laser parameters on the adhesion of coatings produced by the Protal method. The process incorporates an atmospheric thermal spray torch and a pulsed Nd:YAG laser, achieving surface preparation (comparable to grit blasting) and coating deposition in a single step. Coating adhesion was measured via tensile testing and an indentation method, and the rupture areas (along with some of the coating-substrate interfaces) were examined using SEM techniques. The results show that with the new process chemical and metallurgical bonding can be achieved between the substrate and coating by spraying in air.
Particle Flux Imaging (PFI) In-Situ Diagnostics for Thermal Coating Process
Authors: Zierhut J. , Landes K.D. , Krömmer W. , Heinrich P. 
Published: July 2021

Abstract
This paper presents a low-cost in situ diagnostic method that monitors and controls thermal spray processes using a CCD camera and a PC. The method, called particle flux imaging (PFI), records light emitted by thermal spray particles and the hot propellent carrier-medium in which they are conveyed. Brightness distributions corresponding to temperature and density profiles are represented by sets of ellipses that are compared in real time to a reference image. An image analysis algorithm adjusts relevant spray parameters based on the comparisons, maintaining a constant and unchanged spraying process.
Imaging Diagnostics in Thermal Spraying—SprayWatch System
Authors: Hämäläinen E. , Vattulainen J. , Alahautala T. , Hernberg R. , Vuoristo P. , Mäntylä T. 
Published: July 2021

Abstract
A novel technique and an instrument for on-line, quantitative imaging diagnostics and process control in thermal spraying have been developed and tested in laboratory and industrial conditions. In-flight spray particles are imaged by their natural luminosity with a short-exposure, digital CCD camera system. Particle images are processed using digital image processing techniques in a PC computer. The number of particles per frame and the spatially resolved particle velocities are calculated from the images. Spectrally resolved image information is further used to determine pyrometric two-color particle temperature. A number of different modes of data presentation have been developed. The developed instrument can be used to determine particle number, velocity and temperature distributions of individual in-flight particles from the imaged region of interest of the plume. Dividing the imaged area into smaller sections, spatial distributions of these parameters can be studied. SprayWatch system provides a technically simple, easy to operate, single imaging instrument, which can provide a visual overview of the spray plume in combination with quantitative evaluation of the most important spray particle parameters. In this paper examples of using the monitoring system with plasma and HVOF spraying are presented. Preliminary test results of using a semiconductor laser generated light sheet to detect cold particles is also demonstrated.
Powder Particle Velocity Measurement in Electrothermal Chemical Spraying Device
Authors: Rabani L. , Wald S. , Appelbaum G. , Zoler D. 
Published: July 2021

Abstract
A powder velocity diagnostic system in ElectroThermal Chemical Spray (ETCS) coating technology has been developed. The powder velocity is a crucial variable that influences the coating quality. However, non-of the existing methods is suitable for the velocity measurement in the special conditions of the ETCS technology. The proposed diagnostic system is based on a familiar technique called Double Rotating Disk. It measures the powder particle time-of-flight between two parallel disks. The disks are rotated by a high-speed motor. The front disk has holes distributed on its circumference. Particles passing a hole are deposited on the second disk. The displacement between the position of the deposited particles spot center and projection of the hole center on the second disk is inversely proportional to the velocity. The method allows the measurement of particle velocity with accuracy better than 10%. The results are in a good agreement with theoretical model predictions. The method is able, also, to observe the powder deposition rate and the particles spatial distribution inside the powder cloud according to their dimensions as a function of time during the coating process.
Application of Supersonic Expanding Plasma Jets to Nitriding of Steel Materials
Authors: Ando Y. , Tobe S. , Tahara H. , Yoshikawa T. 
Published: July 2021

Abstract
Since plasma jets, which have been used as heat sources of thermal plasma spraying process, expand adiabatically under a low pressure environment, the plasma temperatures drastically fell down to 2000K at the nozzle out let at 30Pa chamber pressure. However, the plasma jets still had enough reactivity to form hard nitride layer on the surface of the titanium samples by only a few minutes treatment. In this study, in order to obtain useful information for the practical applications of this plasma as low temperature and high rate surface modification processes, nitriding of nitriding steel and carbon steel using supersonic expanding hydrogen/ nitrogen mixture plasma jets were carried out. Consequently, though surface hardening was occurred slightly in the case of carbon steel, surface hardening was obviously promoted in the case of nitriding steel. In both cases, surface hardening was promoted with increasing hydrogen flow rate and thermal damages of the samples due to heat transfer from plasma jets weren't observed. Besides, according to the results of wear testing, wear mass loss of nitrided samples were much lower than that of non-nitrided samples. From these results, this process was found to have a high potential even in the case of surface modification of steel materials.
Fracture Toughness of HVOF Sprayed WC-Co Coatings
Authors: De Palo S. , Mohanty M. , Marc-Charles H. , Dorfman M. 
Published: July 2021

Abstract
Tungsten carbide-cobalt coatings are extensively used to protect surfaces from wear in many types of applications, such as compressor piston rods, pump plungers, shaft sleeves on centrifugal pumps and fans, and midspans of compressor blades in gas turbines. The wear behavior in any application is strongly influenced by the basic physical and mechanical properties of such coatings. Fracture toughness as a mechanical property indicates the resistance to fracture in the presence of a sharp crack, and thus provides a measure of the intrinsic strength of the cemented carbides coatings. In this study, Vickers indentation tests have been used to quantify the in-plane fracture behavior of various WC-based coatings deposited by the High Velocity Oxy-Fuel (HVOF) spray process. The indentation cracks are analyzed in terms of standardized relations that utilize radial-median crack geometries. It is shown that the fracture properties of HVOF WC-Co coatings are anisotropic, and depend strongly on the microstructure and composition of the coatings. The crack propagation is determined by the porosity, binder mean free path, and the shape, size, and distribution of the reinforcing carbide particles. The erosion resistances of the coatings have also been discussed as a function of the fracture properties and mechanisms. It is shown, in this study, that the Vickers indentation method is a useful and convenient technique for determining the in-plane fracture toughness of HVOF sprayed WC-based coatings.
Temperature Profiles and Thermal Stress Analysis of Plasma Sprayed Glass-Composite Coatings
Authors: Zhang T. , Qiu Z. , Bao Y. , Gawne D.T. , Zhang K. 
Published: July 2021

Abstract
Experimental measurements have been carried out with the aim of investigating the residual stresses generated during plasma spray deposition of glass composite coatings. The research shows that the behaviour of these materials is fundamentally different from metals and ceramics. The quench stress in the glass composites can be eliminated by plasma-scanning. This is attributed to their low glass transition temperatures, which enable the stresses to be completely relaxed. The work also shows that the addition of alumina as a second phase allows the expansion mismatch between the coating and the steel substrate to be controlled. Control of the second-phase volume-fraction enables the residual stress in the composite coatings to be reduced to zero. Real-time measurements on deflection and temperature show that the dimensions of the substrate, plasma operating conditions and scanning rate have substantial effects on the temperature profiles within the deposits. Keywords: glass composite coatings, thermal stress, plasma spraying.
Residual Stress Determination from a Laser-Based Curvature Measurement
Authors: Swank W.D. , Gavalya R.A. , Wright J.K. , Wright R.N. 
Published: July 2021

Abstract
Thermally sprayed coating characteristics and mechanical properties are in part a result of the residual stress developed during the fabrication process. The total stress state in a coating/substrate is comprised of the quench stress and the coefficient of thermal expansion (CTE) mismatch stress. The quench stress is developed when molten particles impact the substrate and rapidly cool and solidify. The CTE mismatch stress results from a large difference in the thermal expansion coefficients of the coating and substrate material. It comes into effect when the substrate/coating combination cools from the equilibrated deposit temperature to room temperature. This paper describes a laser-based technique for measuring the curvature of a coated substrate and the analysis required to determine residual stress from curvature measurements. Quench stresses were determined by heating the specimen back to the deposit temperature thus removing the CTE mismatch stress. By subtracting the quench stress from the total residual stress at room temperature, the CTE mismatch stress was estimated. Residual stress measurements for thick (&gt;1mm) spinel coatings with a Ni-Al bond coat on 304 stainless steel substrates were made. It was determined that a significant portion of the residual stress results from the quenching stress of the bond coat and that the spinel coating produces a larger CTE mismatch stress than quench stress.
An ASM Recommended Practice for Modified Layer Removal Method (MLRM) to Evaluate Residual Stress in Thermal Spray Coatings
Authors: Rybicki E.F. , Shadley J.R. , McGrann R.T.R. , Savarimuthu A.C. , Graving D. 
Published: July 2021

Abstract
Thermal spray coatings are subjected to mechanical loadings in many applications, and there is a need to evaluate the mechanical properties of these coatings. Mechanical properties of interest in the performance of thermal spray coatings include fatigue life, wear resistance, bond strength. Young's modulus, Poisson's ratio, and residual stresses. One property that has a large effect on the performance of thermal spray coated parts is the residual stress distribution in the thermal spray coating and in the substrate. Thus, it is important to have (1) a fundamentally sound method for evaluating residual stresses and (2) a written recommended procedure for applying the method. ASM International is not a standard writing organization. Yet, the increased use of thermal spray coatings and the need for documentation on methods for evaluating mechanical properties of thermal spray coatings have generated a need to prepare Recommended Practices. To meet this need, the ASM International Thermal Spray Society has formed three subcommittees to prepare Recommended Practices for thermal spray coatings. This paper describes a draft form of a Recommended Practice for evaluating residual stresses in thermal spray coatings. This Recommended Practice is being developed by the Subcommittee on "Evaluating of Mechanical Properties of Thermal Spray Coatings". The method, called the Modified Layer Removal Method, has been presented in several papers and has been used for a variety of different coatings. The paper describes the dimensions of the test specimen, the equipment needed, the procedure for removing layers, and the methods for collecting and interpreting the data to evaluate through thickness residual stresses. The Recommended Practice (RP) is in Draft form, but is presented to let the thermal spray community know about the RP effort and invite comments and volunteers to write other RP's.
Influence of the Plasma Spray Process on the Microstructure of Atmospheric Plasma Sprayed Yttria Stabilized ZrO2
Authors: Friis M. , Persson C. , Wigren J. 
Published: July 2021

Abstract
Plasma spraying is a very complex process, controlled by a large number of process parameters. The spray gun parameters control the plasma plume and thereby the velocity and temperature of the particles in the plasma. Some of the spray gun parameters are difficult or impossible to control, but variations of them give rise to fluctuations in the microstructure of the sprayed thermal barrier coating and thereby low reproducibility. By movement of the control from the spray gun to direct control of the particle properties in the plasma this problem will be avoided, and it should result in better process control, higher quality of the final coating and thus improved reproducibility. In this study, the influence of the plasma spray process on the coating microstructure was investigated. An orthogonal factorial designed experiment was performed, where eight process parameters were varied, resulting in 16 different coatings. The particle properties were observed in-situ with the optical measurement system DPV 2000. The microstructure of the coatings was studied using optical microscopy and the amount of different features, i.e. cracks and pores, was quantified. Multiple linear regression was used to find models describing the relation between the spray gun parameters and the particle properties, between the spray gun parameters and the microstructure, and between the particle properties and the microstructure. The results showed that the spray gun parameters well describe the variation in particle velocity and particle temperature. Further, it was found that particle velocity, particle temperature, spray angle, and substrate temperature are the most important parameters concerning influence on the coating microstructure. However, their influence on the different microstructure features varied. The study implies that focus can be set on one or two particle properties measured in the plasma, instead of the numerous spray gun parameters.
Tungsten Carbide-Cobalt Coatings for Industrial Applications
Authors: Dorfman M. , DeFalco J. , Karthikeyan J. 
Published: July 2021

Abstract
This paper compares the coating characteristics of two HVOF processes: air-cooled converging-nozzle Diamond Jet (DJ) spraying and Hybrid 2600 air/water-cooled converging/diverging technology. WC-Co coatings were deposited on steel substrates using different combinations of spray parameters, gas flow ratios, and cooling gas types. The coatings were then examined and tested to determine the extent to which microstructure, hardness, surface roughness, wear resistance, and deposition efficiency can be controlled. In addition to investigating process relationships, the paper also addresses the issues of practicality and cost.
Particle Behavior in a Powder-Laden HVOF Jet
Authors: Lugscheider E. , Herbst-Dederichs C. , Zhao L. 
Published: July 2021

Abstract
The paper deals with an analysis of particle behavior in a HVOF-jet as a function of process parameters. The experiments were carried out using a commercial HVOF gun with hydrogen as fuel gas. A commercial 316 L stainless steel powder was used for spray material. The experiments were conducted by using on-line particle diagnostics in order to simultaneously detect particle velocity, temperature and diameter. The results were correlated with caught spray powder and splats. The experiments released that among many parameters the oxygen/fuel gas ratio is the most important parameter. It was found, that fragmentation of partially melted particles in a supersonic jet is not a neglectable phenomenon. It may cause excessive oxidation inflight and therefore is to be avoided in the production of oxygen-poor coatings. Furthermore, it was found that velocity or temperature measurements of particles have to be interpreted very carefully in order to characterize the process. Without taking a possible change of the particle size due to inflight fragmentation into consideration either measurement value will lead to very limited information benefit.
Investigation of Splat/Substrate Contact During Molybdenum Thermal Spraying
Authors: Jiang X.Y. , Wan Y.P. , Wang X.Y. , Zhang H. , Goswami R. , Herman H. , Sampath S. 
Published: July 2021

Abstract
Molybdenum splats were produced at three plasma conditions on steel substrates preheated to three temperatures. Morphology of splats and corresponding craters formed on substrates were observed; dimensions of splats and craters were measured with an optical non-contact interferometer. It is found that substrate is significantly melted and deformed upon impact of the droplet, which leads to the formation of flower like splats and craters. On average, only about 36 to 53 % of the areas covered by splats were in good metallurgical/mechanical contact with substrate. Normalized crater volume increases with droplet size and the contact is improved for the high particle energy/high substrate temperature condition as compared with low particle energy/medium substrate energy condition. Splat morphology and crater formation is explained based on impinging jet heat transfer model.
Effects of Spraying Parameters on Phase Formation and Distribution in Plasma-Sprayed Hydroxyapatite Coatings
Authors: Sun L. , Berndt C.C. , Lima R.S. , Kucuk A. , Khor K.A. 
Published: July 2021

Abstract
Calcined spray-dried hydroxyapatite (Ca10(PO4)(OH)6; i.e., HA) powders were atmospherically plasma sprayed (APS) using various process parameters. The resulting phases within the coating surface and the interface between the coating and the substrate were analyzed using X-ray diffraction (XRD) methods. This XRD revealed the presence of both amorphous (i.e., amorphous calcium phosphate: ACP) and crystalline phases. The crystalline phases included both HA and some impurity phases from the decomposition of HA, such as tricalcium phosphate (α-TCP and β-TCP), tetracalcium phosphate (TTCP) and calcium oxide (CaO). The crystallinity of HA decreased with increasing spray power and stand-off distance (SOD). The percentage of all impurity phases increased with the spray power. The percentage of both TCP and TTCP decreased with the SOD while the CaO percentage increased. In addition, the percentage of ACP and CaO were higher in the interface than at the surface of the coating while the percentage of TCP and TTCP exhibited the opposite effect.
Development of Cordierite Coatings for Low Thermal Expansion Refractory Concretes
Authors: Weaver D.T. , Miller F.S. , Van Aken D.C. , Smith J.D. 
Published: July 2021

Abstract
Stoichiometric cordierite (2MgO-2Al2O3-5SiO2) with additions of titania have been investigated for use as coatings on low thermal expansion refractory concretes. These concretes have coefficients of thermal expansion on the order of 2 ppm/°C. Titania additions of up to 8 mole percent were investigated and the effect of titania in the crystallization of cordierite was examined. Cordierite coatings were air plasma sprayed and both glass and crystalline coatings were produced. The crystalline structure of the coating was found to be dependent upon the preheat temperature of the substrate. Preheats greater than 700 °C produced a mixture of a quartz solid solution and indialite whereas glass coatings were produced at preheats less than 700 °C. Coefficients of thermal expansion for the cordierite materials were dependent upon titania addition and generally increased with addition of titania. In the glass state, the thermal expansion was modestly increased (4.6 to 4.9 ppm/°C) with titania additions, but the quartz and indialite forms of the cordierite increased from 1.2 to 4.7 ppm/°C as the titania addition increased from 0 to 8 mole percent.
Comparison of Wear and Friction Characteristics of HVOF Sprayed WC-Co Coating and Carbon Steel
Authors: Kollia-Rafailidi V. , Neville A. 
Published: July 2021

Abstract
The focus of this paper is to determine the friction and wear characteristics between conventional metal-metal contacts and cermet-metal contacts. A WC-Co based cermet, applied by the High Velocity Oxy-Fuel (HVOF) process on a carbon steel substrate has been investigated in contact with cast iron pins. That has been compared with conventional carbon steel/cast iron couples. A mineral oil and a mineral oil containing the additive zinc dialkyl dithiophosphate (ZDDP) were used as the lubricants. The formation of a wear film has been shown to vary on the metal and cermet surface. The friction and wear response and the wear film nature are discussed.
Vacuum Plasma Spraying of Pre-reacted MoSi2 and SiC-Reinforced MoSi2 Produced by a New Kind of Powder Processing
Authors: Wielage B. , Steinhäuser S. , Reisel G. , Morgenthal I. , Scholl R. 
Published: July 2021

Abstract
Molybdenum silicides have the potential as protective coatings for high-temperature applications because of their high melting point and their high-temperature oxidation resistance. Reinforcing MoSi2 with SiC shows an improvement of its low toughness at room temperature and low creep resistance at temperatures above the brittle-ductile transition temperature of approximately 700-1000 °C. A new kind of powder processing was used to produce MoSi2 and MoSi2-SiC as a feedstock for thermal spraying. Mixtures of the elemental powders, molybdenum and silicon, were prepared by milling and subsequent heat treatment to get highly dispersed, pre-reacted powders. As high-energy milling equipment, a planetary ball mill was used to prepare the powders. In the case of reinforcement, SiC was mixed to the pre-reacted MoSi2 at the end of the milling process, that means before heat treatment. On these as-milled powders, X-ray diffraction characterization (XRD), scanning electron microscopy (SEM), electron probe micro analysis (EPMA) and determination of the oxygen level were carried out. Vacuum plasma spraying has been used to deposit the powders onto a carbon steel substrate. Evaluated coating characteristics were the microstructure (SEM), phases (XRD), EPMA, oxygen content, microhardness and surface roughness. Tests at high temperatures will be considered in future work.
Plasma Spheroidized Alumina/Zircon Mixtures
Authors: Li Y. , Khor K.A. 
Published: July 2021

Abstract
The plasma-spray process is specified by the associated processing parameters, where these influence the properties of the resultant deposits. This article describes the preparation and processing of composite powders for use in thermal spraying by mixing high purity zircon and alumina powders. The spheroidized powder were obtained by high energy ball milling and rapid solidification from the molten state during plasma spraying. The article discusses the processes involved in spray drying and plasma spheroidization, describing thermal analysis and mullitization kinetics in the spheroidized alumina/zircon mixtures.