bluuebunny/crossref_metadata_2025_split huggingface dataset:
Performance of WC-Based, HVOF-Processed Coatings in Sliding Wear
Authors: Marple B.R. , Arsenault B. , Voyer J. 
Published: May 2021

Abstract
For applications in which two contacting surfaces are in constant motion relative to each other, materials that are both wear resistant and non-abrasive are often required. Such attributes become even more important when the moving contact occurs with no liquid lubricants present to facilitate sliding. In the present study several WC-based coatings deposited using the HVOF process and containing one or more metal constituents as the binder (or matrix) phase were evaluated to determine their performance under conditions cf sliding wear. Image analysis of the coatings indicated a level of porosity of less than 1%. Hardness measurements found that values for the Vickers microhardness number were in the range of 1100-1500. For the wear tests, the test couple consisted of a coated ring (thrust washer type design) rotating against a stationary carbon disk. For each test, the contact load, speed of rotation and duration were controlled. During the test, the temperature of the carbon disk and the torque were recorded using a data acquisition system. This data was used to determine the coefficient of friction for each couple which, together with the results of measurements of weight change, provided a measure of the comparative performance of the various coatings. The preliminary results indicated that the values for the coefficient of friction for the various couples ranged from 0.15 to 0.29. The three coating compositions consisting of lONi-WC, 12Co-WC and 17Co-WC were found to out-perform other WC-based materials in these sliding wear tests.
Cavitation Resistance of Thermal Spray Coatings
Authors: Kumar A. , Boy J. , Zatorski R. , March P. 
Published: May 2021

Abstract
Cavitation and erosion damage to hydroelectric turbines and pumps can be a major problem. The effectiveness of thermal sprayed cavitation-erosion resistant coatings for hydroelectric turbine and pumps was evaluated. The coatings evaluated were applied using High Velocity Oxyfuel (HVOF) and Plasma Spray systems. Hard facing cobalt based alloys were evaluated on coupons in the laboratory. Testing was performed using a cavitating jet erosion apparatus utilizing an operating pressure of 27.6 MPa. The results were compared to welded 308 stainless steel. Cavitation resistant austenitic stainless steel weld alloys were also evaluated. The results showed that the cavitation rate of the austenitic stainless steel weld alloys were as low as one third of the rate of the 308 stainless steel. The cavitation rate of the thermally sprayed hard facing coatings were more than three times higher than the rate of the 308 stainless steel. CERHAB glass enamel coatings containing 7 wt % wollastonite fibers were successful applied by using two combustion spray processes. The applied CERHAB coatings were successfully annealed using field portable heaters and may have application as a seal coat for thermal spray coatings applied in the field.
Effect of Metallic Matrix Composition on the Erosion-Corrosion Behavior of WC-Coatings
Authors: Rogne T. , Solem T. , Berget J. 
Published: May 2021

Abstract
In corrosive media the wear resistance of ceramic-metallic coatings is dependent on the corrosion resistance of the metal matrix. Other factors that will affect the coating deterioration are the corrosivity of the medium and any galvanic interaction from the surrounding material. This paper presents results from a study where different types of WC(Co/Cr/Mo/Ni) powders have been sprayed by HVOF, Diamond Jet 2600 Hybrid equipment. The properties of the sprayed coatings have been verified by metallographic studies and by erosion-corrosion testing both under corrosive and non-corrosive conditions. The results clearly demonstrate the importance of having a metal matrix at least as corrosion resistance as the surrounding materials. When wear exposed components in pipe systems, pumps or valves are coated with a WC type coating, the corrosion resistance of the metal matrix should be compatible to the material of the rest of the system. This is especially important when the surrounding materials are corrosion resistant alloys as stainless steels, where the coatings otherwise will act as an anode.
Tribological Behavior of Plasma-Sprayed Coating Layers in Cr2O3/TiO2
Authors: Park J.M. , Lee S.W. , Kim B.K. 
Published: May 2021

Abstract
Wear property of plasma spray coating in Cr2O3/TiO2 powder manufactured of spray dry method on the aluminum substrate was inspected for the application of piston-ring of automotive engine. The plasma spray coatings were varied with feed rate and particle size. Using the ball-on disc type tribometer, wear volume property and surface roughness were investigated. The delamination of the coating layers and wear track were observed with SEM. Also, the cross-section of wear track were investigated, using optical microscopy. As a result of experiment, wear mechanism was addressed.
Composite Fe/TiC Powders for Wear Resistance Coatings Using Plasma Spray Process
Authors: Vitiaz P. , Azarova T. , Talako T. , Ilyuschenko A. , Steinhauser S. , Wielage B. , Gieland U. 
Published: May 2021

Abstract
This work evaluates the potential of using new competitive powders of Fe/TiC system for plasma spraying of wear resistant coatings. To improve coating properties, Cr and Ni were added to the iron matrix. The results of complex investigations of plasma coatings from such materials are presented.
Characterization of Thermal-Sprayed Titanium Anodes for Cathodic Protection
Authors: Holcomb G.R. , Cramer S.D. , Bullard S.J. , Covino B.S. , Collins W.K. , Govier R.D. , McGill G.E. 
Published: May 2021

Abstract
Thermal-sprayed titanium coatings were investigated as anodes for impressed current cathodic protection systems for steel reinforced concrete structures. The coatings were applied by twin-wire thermal-spraying using air and nitrogen as atomizing gases. The coatings were non-homogeneous due to oxidation and nitridation of the molten titanium with the atmospheric gases oxygen and nitrogen. The primary coating constituents were α-Ti (containing interstitial nitrogen and oxygen), γ-TiO and TiN. Nitrogen atomization produced coatings with less cracking, more uniform chemistry, and lower resistivity than air atomization.
An Assessment of Galvanic Effects in Thermal Sprayed Coating Systems
Authors: Hodgkiess T. , Neville A. 
Published: May 2021

Abstract
This paper focuses on the influence and role of galvanic interactions in the corrosion behaviour of thermally-sprayed coated components. Coatings, of different chemistry and applied by various processes (including HVOF) to substrates of carbon steel or stainless steel, have been utilised to facilitate study of galvanic corrosion phenomena both between coating and substrate and also within the coating itself. The experiments have involved the measurement of galvanic currents between separate specimens and also the microscopical examination of galvanic interactions on single specimens. Galvanic corrosion effects, on both a macroscale or microscale, have been observed and the implications of these for coating and coating/substrate integrity are discussed.
Effect of Thermal Spray Parameters on the Adhesion of Polymer-Based Coatings on Steel
Authors: Bao Y. , Gawne D.T. , Zhang T. 
Published: May 2021

Abstract
The adhesion of plasma sprayed polyamide and PMMA coatings to steel depends markedly on the plasma arc power, the spraying distance and the substrate temperature. Each of these process parameters shows an optimum value with respect to adhesion. The underlying reason for this behaviour is the pronounced sensitivity of polymers to temperature. Heat transfer analysis and electron microscopy indicate that a critical amount of heat is required to be transferred from the flame to the feedstock particles in order to provide sufficient splat flow but avoid coating thermal degradation. Inadequate flow leads to interfacial voidage while degradation gives inferior bonding and porosity.
On the Change in Stress State Associated with Bond Coat Oxidation during Heat Treatment of a Thermal Barrier Coating System
Authors: Tsui Y.C. , Clyne T.W. , Reed R.C. 
Published: May 2021

Abstract
Thermal barrier coating systems have been heat treated in order to study the oxidation kinetics of the bond coat. All the surfaces of Ni superalloy substrates were sprayed with ~100 μm of a NiCrAlY bond coat, with or without ~250 μm of a ZrO2 top coat. Thermogravimetric analysis (TGA) was used to monitor continuously the mass change as a result of oxidation of the bond coat during heating at 1000°C for 100 hours in flowing air. In addition, some specimens were heated to 1000°C in static air, cooled to room temperature, weighed and re-heated cyclically. The total exposure time was 1000 hours. Rates of weight gain were found to be higher for the cycled specimens, despite the absence of air flow. This is attributed to damage to the oxide film, which was predominantly α-Al2O3, as a consequence of differential thermal contraction stresses. The changing residual stress state during heat treatment was predicted using a previously-developed numerical model. A thin (1 mm) substrate with ~100 μm bond coat and ~250 μm ZrO2 top coat was used in these simulations, which incorporated creep of the bond coat and the lateral strain associated with oxidation. It is concluded from these computations that, while high stresses develop in the oxide layer, the associated driving forces for interfacial debonding remain relatively low, as do specimen curvature changes. It seems likely that coating spallation after extensive oxide layer formation arises because the interface is strongly embrittled as the layer thickens.
Properties of ZrO2-7wt%Y2O3 Thermal Barrier Coatings in Relation to Plasma Spraying Conditions
Authors: Funke C. , Siebert B. , Stöver D. , Vaßen R. 
Published: May 2021

Abstract
Superalloy samples were coated with thermal barrier coatings (TBC). This TBC-system consisted of two layers. The first layer was a vacuum-plasma sprayed, corrosion resistant layer (MCrAlY) which also acted as a bond coat. The ceramic top layer was atmospheric-plasma sprayed Y2O3-stabilized ZrO2. In order to produce different microstructures, the plasma-spraying parameters for the production of the ceramic coatings were varied. The different ceramic coatings were characterized in terms of porosity and mean elastic modulus. The porosity distribution was also investigated due to its influence on the measured elastic modulus. To record the changes of the plasma sprayed Zirconia due to sintering, the mean elastic modulus of selected coatings was measured as a function of annealing time. One series of TBC-coated specimens was cyclically oxidized at a maximum temperature of 1100°C. After 500 h of thermal cycling, creep within the MCrAlY-bond coat led to a coating failure at both the internal beveled edge and free edge around the specimen. A finite element analysis study of the cyclic oxidation experiment was performed to gain insight into the stress redistributions within the bond coat as a function of time. During the initial temperature increase, critical tensile normal stresses developed above the MCrAlY-Zirconia interface at the free edge. However, these normal stresses became compressive for all following cooling cycles. On the other hand, large tensile normal stresses developed above the MCrAlY-Zirconia interface at the beveled edge during all the cooling cycles. Therefore, high normal stresses responsible for debonding were present within the ceramic coating during all cooling cycles with the most critical stresses occurring at the free edge during the first cooling cycle and near the beveled edge for all the following cooling cycles.
Assessment of Thermal Barrier Coatings by Plasma Deposition
Authors: Ravichandran K.S. , An K. , Taylor R. 
Published: May 2021

Abstract
Thermal conductivity is an important design parameter for thermal barrier coatings. Accurate thermal conductivity data is therefore required to ensure proper design and reliability of gas turbine blades. In the present research, thermal conductivities of Al2O3 and 8wt.% Y2O3 stabilized ZrO2 (8YSZ) coatings, made by air plasma spray, were determined from the measurements of thermal diffusivity and specific heat as a function of temperature. Thermal diffusivity was determined by the laser flash technique. Specific heat was determined by a Differential Scanning Calorimeter (DSC). Detailed analyses of the results indicate that the thermal conductivity is sensitive to coating density (porosity), interfaces between splats as well as the interface between the coating and the substrate. Additionally, thermal conductivity evaluations of these coatings were also influenced by the accuracy and relevance of the data on bulk monolithic materials. Further, analyses of sensitivity of the laser flash technique to variations in the coating and the substrate parameters, for the coatings evaluated in this study, were also performed. The results are discussed in the context of coating characteristics, reference conductivity data for dense materials and the sensitivity of the measurement method to coating parameters.
Process Combination Thermal Spraying/Nitriding—Wear, Corrosion Resistance, and Coating Structure
Authors: Nestler M.C. , Spies H.-J. , Herrmann K. 
Published: May 2021

Abstract
At the present, components which require both nitriding and locally a thermal sprayed coating or nitrided components which should l)e reworked are usually nitrided before spraying and the area to be coated is masked during nitriding or is prepared before spraying by locally removing the nitrided layer by grinding. Seen technically, advantages are to be expected if the nitriding process can be carried out after spraying. Moreover a post-nitriding of thermal sprayed coatings is of interest for improving coating characteristics, mainly wear resistance. Understanding the behaviour of sprayed coatings during nitriding in comparison to bulk materials will help to understand generally the behaviour of such coatings in gas atmospheres at increased temperatures. The objectives of the project are the investigation of the interaction between thermal spraying and nitriding, and the optimisation of both processes to achieve improved bonding, wear and corrosion characteristics respectively to get nitriding of the substrate through the coating without spalling or cracking. Furthermore the behaviour and structural changes of different coatings at increased temperatures are determined. The metallographic, X-ray, wear and corrosion results of the resulting compound coatings and parts are presented. Possible new applications are discussed. The project is funded by the German Research Ministry.
Phase Composition Changes in Annealed Plasma-Sprayed Zircon-Alumina Coatings
Authors: Dubsky J. , Neufuss K. , Kolman B. 
Published: May 2021

Abstract
Phase transformations and/or decomposition of deposited compounds have an indisputable influence on materials properties of plasma sprayed deposits. Using water stabilized plasma, free-standing parts were manufactured from a mechanical mixture of zircon and alumina powders and annealed. The phase composition was determined by X-ray diffraction and the chemical composition was checked by x-ray microanalysis. ZrSiO4 during plasma spraying decomposes into ZrO2 and SiO2. In the as-sprayed condition, after a relatively fast quenching, the following phases can be found: a very fine eutectic mixture of tetragonal and monoclinic ZrO2, amorphous SiO2 and a spinel phase of Al2O3. On annealing for 2 hours at 1300 and 1500 °C the spinel Al2O3 transformed to corundum. At the same time, amorphous silica crystallized. Tetragonal ZrO2 transformed to the monoclinic modification and together with SiO2 formed again ZrSiO4. At the highest annealing temperature Al2O3 and SiO2 partialy reacted to form a small amount of mullite (3Al2O3.2SiO2).
The Gas Permeability of Plasma Sprayed Ceramic Coatings
Authors: Fox A.C. , Clyne T.W. 
Published: May 2021

Abstract
A simple test procedure, based on steady state flow through a membrane, has been developed for measurement of the gas permeability of specimens over a range of temperature. The reliability of this equipment has been verified by testing solid disks containing single perforations and comparing the measured flow rates with those expected on the basis of laminar flow. Coatings of yttria-stabilised zirconia have been produced by plasma spraying in vacuum and in air. The specific permeability of these coatings has been measured at temperatures ranging up to 600°C, using hydrogen gas. It has been found that permeability is increased for coatings produced with longer stand-off distances and at higher pressures. Porosity levels have been measured using densitometry and microstructural features have been examined using SEM. A model has been developed for prediction of the permeability from such microstructural features, based on percolation theory. Agreement between predicted and measured permeabilities is good, although it is clear that more comprehensive data are needed in order to validate the model systematically.
Increase in the Reliability of Thermal Sprayed Coatings
Authors: Steinhäuser S. , Wielage B. , Hofmann U. , Zimmermann G. 
Published: May 2021

Abstract
The characterisation of the effectiveness of sealing was studied by metallographical investigations as well as comparing the investigations with respect to the corrosion- and wear behaviour of the used thermal sprayed coatings and last but not least by measuring of the insulation resistance of the coating system. The obtained results show that there are differences between the used sealants and it is possible through a mechanical treatment of sealed coatings to remove the sealants from the coatings. In the corrosion test the sealants show their efficiency. The sealants insulate the open porosity and prevent the corrosion attack owing to the interconnected pores.
High Performance Super-Austenitic Surface Alloy Using Plasma Coating and Laser Treatment
Authors: Khanna A.S. , Sridhar K. , Deshmukh M.B. 
Published: May 2021

Abstract
Stainless Steels are required for many applications for ship building as well as for offshore structures such as oil exploration. AISI type 304 stainless steel is not very suitable for such applications as it has a strong tendency for pitting and crevice corrosion. Even type 316 and 317 stainless steels which have respectively 2.5 and 3.5% Mo are not very effective in these environments. Commercially available stainless steels, viz., Avesta 254 SMO is being employed for such applications because of its strong resistance to pitting and crevice corrosion. This is mainly because of high Mo concentration (6.5%). Such steels are not only costly but are prone to form deleterious phases such as delta ferrite and sigma during welding or other heat treatment operations. Hence, an alternative technique to restrict Mo at the surface is needed. In the present work, surface alloys consisting of an austenitic stainless steel with Mo content as high as 10-12% have been formed on stainless steel type 304 substrates. These steels show enhanced passivity and strong resistance to pitting corrosion.
The Effects of Post Heating an HVOF Sprayed Fusible Coating
Authors: Moskowitz L. 
Published: May 2021

Abstract
Fusible coatings of Nickel-Chromium alloys with various amounts of Boron and Silicon commonly used for severe load applications. The coating is normally sprayed, then fused by heating to the point of liquation. The fusing process causes powder coalescence and increases density. At the same time, the high fusing temperatures creates a “brazed” bond which gives these coatings extremely high adhesive bond strengths. The improved bond strength is the result of the metallurgical bond as compared to the majority of thermal spray coatings which rely only on mechanical bonding mechanisms. The fusing operation is very sensitive, especially when a hand torch fuse is required. To circumvent these problems, a study was conducted to see if high density HVOF sprayed coatings might achieve fused quality by furnace heating to temperatures well below the liquation point. Various times and temperatures were surveyed. Bond strength tests of coatings sprayed to heavy thicknesses, hardness and impact tests, and metallography were used for evaluation. It was determined that heating as low as 1500° F for three hours could improve the properties of an as-sprayed HVOF coating to where it developed characteristics very similar to that of a fused coating.
Inflight Behavior of Dissimilar Co-Injected Particles in the Spraying of Metal-Ceramic Functionally Graded Materials
Authors: Fincke J.R. , Swank W.D. , Haggard D.C. 
Published: May 2021

Abstract
In the spraying of functionally graded coatings the particle ensemble delivered to the substrate can vary from a relatively low melting point metallic particle to a significantly higher melting point ceramic particle. At various stages in the spray process the particle ensemble can be either predominantly metallic, ceramic, or an intermediate combination. For co-injected particles the mixtures do not behave as a simple linear superposition of the spray patterns of the individual particle types. The particle temperature, velocity, size distributions, and pattern characteristics of the resulting spray fields is examined for all ceramic particle sprays (ZrO2), all metallic particle sprays (NiCrAlY), and for a 1:1 mixture. The major particle-particle interaction occurs in the injector itself and results in a modified spray pattern which is different from that of either material sprayed alone. The particle velocity distributions generally exhibit a bimodal nature which is dependent on the size and density of the injected particles.
Computational Analysis of a Three-Dimensional Plasma Spray Jet
Authors: Dussoubs B. , Fauchais P. , Vardelle A. , Vardelle M. , Themelis N.J. 
Published: May 2021

Abstract
An analysis of a d.c. plasma jet is presented using a three-dimensional commercial fluid dynamics code, ESTET. This code solves the coupled conservation equations of mass, species, momentum and thermal energy equations for a compressible and turbulent fluid in control volume and finite difference formulation. Computations take into account fluid turbulence using a standard k-s model with the Launder and Sharma correction for the laminar zones, e.g. the plasma core. Two series of spraying conditions differing in the total gas flow rate (30 and 60 slm) and the arc current (300 and 600 A, respectively) are computed. The process parameters are independently varied about the nominal operating conditions. The effect of the variation of primary and secondary gas flow rate, effective power and powder carrier gas flow rate on flow fields characteristics, is discussed.
In-Situ Measurement of Particle Concentration and Velocity Using a Non-lntensified CCD Camera
Authors: Knuuttila J. , Saarenrinne P. , Hernberg R. , Lehtinen T. , Mäntylä T. 
Published: May 2021

Abstract
The deposition efficiency (DE) of a particular powder for a particular thermal spray process is very important factor when coating economics is being considered. There are many coating applications, however, where it is also important to know how the deposition efficiency changes during a longer coating process. Normally the DE is determined as mass ratio of powder fed into the process and corresponding weight gain of the sample. In this work the deposition efficiency has been determined for aluminum oxide powder in atmospheric plasma spraying using different spray parameters and electrode wear states. The coating process and in-flight particles were monitored using a fast non-intensified CCD-camera. Using digital image analysis the relative hot particle concentrations and velocity distributions were calculated from images. The possibility to use a CCD camera based monitoring system for in-situ measurement of DE is discussed. Additional laser illumination and PTV measurements were performed to verify the cold particle flux unseen by the plain CCD camera.