bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structure and Properties of Stainless Steels Coatings Produced by Supersonic Plasma Spraying Method
Authors: Borisov Yu. , Borisova A. , Golnik V. , Murashov A. , Bobrik V. 
Published: May 2021

Abstract
Stainless steel coatings were produced by supersonic air-gas plasma spraying method. Mixture of air and natural gas was used as a plasma forming gas. Powders of 304L and 316L stainless steels were used for plasma spraying. Thickness of coatings was up to 3 mm. Coating structure was studied. Dependence of oxygen content in coatings upon particle sizes and spraying conditions was established. Investigation of electrochemical properties of coatings was carried out by potentiostatic method. Corrosion potential and corrosion rate in sea water, hydrochloric and sulphuric acid solutions were determined.
Metallographic Preparation of Thermal Spray Coatings: Coating Sensitivity and the Effect of Polishing Intangibles
Authors: Sauer J.P. 
Published: May 2021

Abstract
The heterogeneous or composite nature of the thermal spray deposit can make choosing a metallographic preparation process very difficult. Hard vs. soft phases, brittle ceramics, and mixtures of many phases can create a variety of issues. When a procedure is developed, it becomes a necessity to document all the parameters or intangibles that define the process. Examples of procedure definition will be discussed and a suggested list of critical intangibles such as polishing abrasives (concentration vs. frequency of application), lubricant (pH, type), and many other factors will be highlighted.
Thermal Measurements of Substrate during Spray Processes
Authors: Brandt O. , Wandelt M. 
Published: May 2021

Abstract
Most research work about thermal spraying involves the special process itself, the spray powder materials and the coatings. The major aim is to clarify the basic relations between different spray parameters and the coating properties, such as bond strength, porosity, wear resistance and residual stress. This paper presents temperature measurements of the substrate while a spray stream is directed at the surface. The substrate temperature was measured with an infrared camera at the back side of a sample. The camera allows a measuring frequency of 4 Hz using 140 by 140 pixel view field. Basic studies were carried out with a High Velocity Oxygen Fuel (HVOF)- System. Typical HVOF parameters were compared while spraying different tungsten carbide alloys on aluminum substrates. Comparative studies with plasma processes were performed. These results should help to calculate the temperature and thermal expansion of real parts with various structures before the spray process is used to apply a coating.
Elasticity Characteristics of Plasma Spray Coatings
Authors: Dekhtyar L. , Kleyman A. , Berman S. , Andreychuk V. 
Published: May 2021

Abstract
Future development of thermal spray processes and new composite materials raises an important problem concerning the transition from qualitative to quantitative methods of coatings evaluation. It is well known that thermal spray coating deposition in most cases is accompanied by the formation of temporal and residual stresses through the coating thickness. For proper evaluation of formed stressed state it is extremely important to know the real value of elastic characteristics in different layers of the coating. This problem has become more complicated taking into consideration the variety of materials, different spray parameters, number of coating layers and extreme service conditions. These values can be obtained only from experimentation. Elastic characteristics (EC) could be used in many calculations, such as durability, stiffness, fatigue, vibration and others. This paper describes new methods of experimental determination of elastic characteristics presumed as variable throughout the coating thickness. Influence of coating composition, particle size of initial powders, spray parameters, post-treatment and other factors on elastic modulusses were studied. Obtained experimental data for different materials supplement existing data and can be used for evaluation of residual stresses and other purposes.
Residual Stress Development during Thermal Spraying of WC-Co on Titanium
Authors: Pejyrd L. , Wigren J. , Greving D.J. , McGrann R.T.R. , Shadley J.R. , Rybicki E.F. 
Published: May 2021

Abstract
Tungsten carbide cobalt thermal spray coatings are used in the aircraft industry to reduce wear damage of lightweight metals such as titanium The performance and life of tungsten carbide (WC-Co) coated titanium materials depend on many factors. An important factor that has received increased attention in thermal spray research is the residual stresses in the coating and substrate. Residual stresses depend on the parameters of the application process. Parameters affecting residual stresses include the prespray treatment of the substrate material (grit blasting, shot peening) and the type of spray application process (HVOF, plasma arc) During the in-service life of a WC-Co coated material, residual stresses can change significantly. The goal of this work is to quantitatively evaluate the changes in residual stresses of the substrate and the WC-Co coating during various stages of processing. A destructive laboratory method, called the "Modified Layer Removal Method," was used to evaluate the through-thickness residual stresses of the WC-Co coating and the titanium substrate material. Residual stresses are determined for three conditions: (1) shot peened, (2) shot peened and grit blasted, and (3) shot-peened, grit blasted and thermal spray coated. The changes in the residual stresses are shown at selected stages during the processing history of the coated materials. Differences between residual stress levels at selected stages are identified and discussed. The effect of coating thickness and HVOF application process on the residual stress in the coating is also examined.
Effects of Substrate Temperature and Thermal Cycles on Residual Stresses in Yttria Stabilized Zirconia Thermal Barrier Coatings
Authors: McGrann R.T.R. , Graves J.A. , Rybicki E.F. , Shadley J.R. , Brindley W.J. 
Published: May 2021

Abstract
Residual stresses are inherent in thermal barrier coatings (TBC's) and can influence in-service performance and life of the coatings. Therefore, the effective design and processing of TBC's requires knowledge about residual stress generation and the effect of residual stresses on TEC life. Understanding residual stress generation and the effects on thermal barrier coating life are formidable tasks that have received little attention in the literature. This work addresses the first task. Specifically, the objectives of this work were to better understand how processing and post-processing residual stresses are generated in TBC's. The approach was to evaluate the effect of substrate temperature during processing and the effect of post-processing thermal cycling on the generation of coating residual stresses. Residual stress measurements were conducted using an experimental residual stress evaluation technique called the "Modified Layer Removal Method." Results showed residual stresses could be changed both by controlling the substrate temperature during processing and by thermal cycling after processing. Residual stresses in specimens with a higher substrate temperature during processing were found to be more compressive than residual stresses in specimens with a lower processing substrate temperature. Post-processing thermal cycling caused the residual stresses to become more compressive for specimens with both the higher and lower substrate processing temperatures. Residual stresses for one and ten post-processing thermal cycles were evaluated. For both substrate processing temperatures, the change in TBC compressive residual stresses for the first cycle was more than three times the total residual stress change that occurred in cycles two through ten. Interestingly, the increase in residual stresses in cycles two through ten for the higher substrate processing temperature was greater than that for the lower processing substrate temperature. In other words, based on results obtained here, compressive residual stresses generated during thermal cycling appear to depend on the existing processing residual stress. For these conditions, higher processing compressive residual stresses lead to higher post-processing changes in compressive stresses per thermal cycle.
New Set-Up to Measure Residual Stresses during Plasma Sprayed Coating Formation and Cooling
Authors: Leger A.C. , Grimaud A. , Fauchais P. , Catteau C. 
Published: May 2021

Abstract
A new instrument has been developed for measuring stresses due to particle quenching, temperature gradients during spraying, temperature fluctuations during coating formation and expansion mismatch between coating and substrate upon cooling. It records in situ and continuously the curvature of a substrate during spraying and upon cooling after spraying with a contacting displacement sensor. The substrate is fixed onto a pair of knife edges by springs. The knife edges are disposed on a water-cooled rotating cylindrical substrate holder and the substrate (2*15*100 mm3) is parallel to the holder axis. The torch is moved back and forth parallel to the holder axis and the substrate temperature is recorded by a thermocouple spot welded to it. Examples of results with alumina coatings on steel substrates are presented.
Thermal Spraying as a Forming Process of Thermoelectric Material
Authors: Lugseheider E. , Langer G. , Herbst C. , Schilz J. , Müller E. 
Published: May 2021

Abstract
The direct conversion of heat into electric current is still less developed form of energy conversion. Thermoelectric material working in a temperature gradient is able to induce a voltage that can drive a serial resistor. New research activities try to broaden the employment of thermoelectric generators from spacecraft technologies to terrestrial applications. The main problem at the moment is rather the lack of economic production methods, than the low efficiency of conversion. After an overview about the basics of thermoelectrics and possible applications the paper presents the thermal spraying as an alternative processing method with first attempts to realize graded structures. Al-doped and Co-doped FeSi2 has been consolidated by APS, SPS, VPS and HVOF spraying. The microstructure, phase composition and oxygen input have been investigated and set into relation to thermoelectric properties.
Friction and Wear Behavior of Thermally Sprayed Al-Cu-Fe Quasicrystal Coatings
Authors: De Palo S. , Usmani S. , Sampath S. , Sordelet D.J. , Besser M. 
Published: May 2021

Abstract
Gas atomized Al63Cu25Fe12 powders of varying size fractions were plasma sprayed to study the relationships between coating microstructure and tribological behavior. After spraying, annealing was performed on one of the coatings. Abrasion and sliding wear tests were performed on the coatings. The results indicate a correlation between the abrasion resistance and hardness of the coatings. Furthermore, sliding wear tests reveal lower coefficients of friction for the as-sprayed coatings compared to the annealed coatings.
Characterization of Electrochemically-Aged Thermal-Spray Titanium Anodes on Concrete
Authors: Covino B.S. , Holcomb G.R. , Cramer S.D. , Bullard S.J. , Collins W.K. , McGill G.E. 
Published: May 2021

Abstract
Steel-reinforced concrete slabs coated with a thermal-sprayed titanium anode were used to simulate impressed current cathodic protection systems. The titanium anodes were activated with a cobalt nitrate catalyst and subjected to accelerated electrochemical aging representing approximately 23 years at 0.00215 A/m2 (0.2 mA/ft2). During the aging experiment, current was kept constant at 0.0215 A/m2 (2 mA/ft2), voltages were recorded, and water was applied periodically when voltages exceeded compliance levels. At the end of the experiment, coating resistivity, adhesion strength, and titanium-concrete interfacial chemistry were determined. Results show that the coating resistivity increases and adhesion strength decreases with electrochemical aging. Voltages for the slabs varied with the relative humidity. Electrochemical reactions at the titanium-concrete interface caused deterioration of the cement paste by leaching of calcium compounds. Accelerated aging results are compared to similar ones for an uncatalyzed titanium anode and to results from the Depoe Bay Bridge.
The Corrosion Behaviour of a Cermet Coating Applied by HVOF Spraying
Authors: Neville A. , Hodgkiess T. 
Published: May 2021

Abstract
Many of the state-of-the-art thermal-spray coatings (e.g. plasma, HVOF) have been developed with wear resistance as a primary aim. However, these coatings are increasingly being required to function in environments where corrosive attack is possible. This paper comprises a description of a study of the corrosion a WC-based coating containing 10%Co and 4%Cr as the metallic binder. The coating, in the form of test coupons, involving a substrate of superduplex stainless steel, has been exposed to seawater at ambient temperature (18°C) and 50°C. The corrosion behaviour and detailed corrosion mechanisms have been investigated using electrochemical monitoring techniques supported by precise post-test microscopical examination using light microscopy, scanning electron microscopy, atomic force microscopy and x-ray microanalysis. Results have shown the corrosion resistance of the coating material to be critically dependent on the temperature of the solution and that important changes in corrosion mechanisms arise as a function of the temperature.
Thermally Sprayed Ternary Materials for Enhanced Corrosion Protection
Authors: Lester T. , Harris S.J. , Kingerley D. , Matthews S. 
Published: May 2021

Abstract
Thermal spraying has been used to protect many steel structures from aqueous corrosion using Zinc and Aluminium, and to some extent their alloy coatings to provide galvanic protection. The lifetimes of the coatings can approach 50 years even when exposed in severe marine environments. Zinc coatings work by continuously sacrificing themselves and slowly dissipating over time. Aluminium coatings passivate more readily and form a barrier layer, the passivity makes them less able to protect damaged areas and to self heal. A new ternary coating system involving Aluminium, Zinc and Magnesium has been shown to be capable of providing both a passive barrier layer as well as being able to give galvanically active protection. Salt spray tests have shown that the resistance to red rust of these new coatings increases by 300% over similar thicknesses of the separate metal coatings. Processing by arcspray is straightforward and both adhesion and deposition efficiency are better than where Zinc is sprayed alone.
Flame Spraying of Polymers
Authors: Varacalle D.J. , Zeek D.P. , Couch K.W. , Benson D.M. , Kirk S.M. 
Published: May 2021

Abstract
Statistical design-of-experiment studies of the thermal spraying of polymer powders are presented. Studies of the subsonic combustion (i.e., Flame) process were conducted in order to determine the quality and economics of polyester and urethane coatings. Thermally sprayed polymer coatings are of interest to several industries for anticorrosion applications, including the chemical, automotive, and aircraft industries. In this study, the coating design has been optimized for a site-specific application using Taguchi-type fractional-factorial experiments. Optimized coating designs are presented for the two powder systems. A substantial range of thermal processing conditions and their effect on the resultant polymer coatings is presented. The coatings were characterized by optical metallography, hardness testing, tensile testing, and compositional analysis. Characterization of the coatings yielded the thickness, bond strength, Knoop microhardness, roughness, deposition efficiency, and porosity. Confirmation testing was accomplished to verify the coating designs.
Plasma Spraying of Functionally Graded NiCrAIY/Yttria Stabilized Zirconia Coatings Using Pre-Alloyed Powders
Authors: Khor K.A. , Gu Y.W. 
Published: May 2021

Abstract
Pre-alloyed, plasma spheroidized powders were used as feedstock in the plasma spraying of functionally graded ZrO2/NiCrAlY coatings. The advantage of using pre-alloyed powders was to ensure chemical homogeneity and promote uniform density along the graded layers, and these pre-alloyed powders could be successfully used to prepare the different inter-layers of functionally graded coatings. The microstructure, density and microhardness changed gradiently in the ZrO2/NiCrAlY coatings. The bond strength of ZrO2/NiCrAlY coatings with different graded layers was measured. Results showed that for as-sprayed coatings with the same thickness, the bond strength increased with the number of graded layers. The bond strength of the coatings with five graded layers was about twice as high as that of the duplex coatings because of the significant reduction of the residual stress in the coatings. Experimental results also showed that the bond strength of as-sprayed coating increased significantly after hot isostatic press (HIP) and vacuum heat treatments, and the reason can be attributed to the densification of the microstructure, the decrease of defects in the coatings, inter-diffusion between layers and further reduction in the residual thermal stress.
Multi-Layered Thermal Barrier Coating for Land-Based Gas Turbines
Authors: Tamura M. , Takahashi M. , Ishii J. , Suzuki K. , Sato M. , Shimomura K. 
Published: May 2021

Abstract
Multi-layered thermal barrier coatings (TBC) having different functions were proposed for the hot section components of land-based gas turbines. This paper describes the multi-layered TBC with an oxidation resistant layer. A conventional duplex TBC and a triplex TBC, in which an aluminized layer was added to the conventional duplex TBC to increase oxidation resistance, was prepared. It was confirmed by a burner rig test that the triplex TBC with the aluminized layer is resistant to oxidation and shows high durability in a thermal cycle test, compared with the conventional duplex TBC. The spalling in the thermal cycle test of each TBC specimen occurred at the same position and when the thickness of the oxidation layer was 11-13 μm. The mechanism of spalling of the coating in the thermal cycle test was discussed in terms of stress in the coating. Stress in the direction of spalling occurs by an uneven interface between the bond coat and top coat, and increases with growth of the oxidation layer. It is thought that the high durability of the triplex TBC in the thermal cycle test is derived from suppressing the growth of the oxidation layer and decreasing the stress due to the addition of the aluminized layer.
The Influence of Injector Geometry and Carrier Gas Flow Rate on Spray Pattern
Authors: Fincke J.R. , Swank W.D. , Haggard D.C. 
Published: May 2021

Abstract
The performance (particle velocity and velocity distribution) of a typical injector, and the resulting particle spray pattern for metallic (NiCrAlY) and ceramic (ZrO2) particles are examined as a function of carrier gas flow rate and the effect of varying the geometry immediately upstream of the injector. Injector performance is also examined for a 1:1 mixture of ceramic and metallic particles such as is used in the spraying of functionally graded materials. The upstream geometries tested included a 90° "tee," a 90° elbow, and a straight entrance. The elbow geometry was tested in both "up" and "down" orientation to determine the influence of gravity. The upstream geometry can alter the average particle injection velocity by 10-15% influencing both the spray pattern trajectory and width.
Suspension Plasma Spraying (SPS) of Cobalt Spinel
Authors: Schiller G. , Müller M. , Gitzhofer F. , Boulos M.I. , Heimann R.B. 
Published: May 2021

Abstract
Fine (median size 6 μm and 0.3 μm) cobalt spinel (Co3O4) powders were processed suspended in a suitable liquid phase. Suspensions exceeding 50 wt.% solid phase content were successfully injected into an inductively coupled plasma. Spheroidized powders with large particle size (up to 80 μm) were prepared, and cobalt oxide coatings were produced by this novel RF-SPS method. The microstructural features of the coatings can be controlled by parameter optimization similarly to plasma spraying of dry powders. Numerous variations of the physical and chemical conditions of the process were performed in an attempt to overcome the main disadvantage of the process, i.e. the decomposition of the spinel phase to CoO. So far, the spinel phase could be reestablished only by a post-treatment of the deposited coatings with atomic oxygen in the RF plasma.
Powder Processing by Suspension Plasma Spraying
Authors: Bouyer E. , Gitzhofer F. , Boulos M.I. 
Published: May 2021

Abstract
Suspension Plasma Spraying (SPS) is a thermal spray process based on a suspension of fine (&lt;10 μm) or even ultrafine (&lt;100 nm) powders which is axially fed into the induction plasma through an atomization probe. The atomization of the suspension results in microdroplets (20 μm in size). They are flash dried in the plasma, melted and finally can impact a substrate to build a coating or be cooled down and collected as a spheroidized powder. The large industrial potential of this technology results first from the use of fine powder or even sol-gel which is one of the starting step for many ceramic processes, and second from the various side benefits of the liquid phase in the SPS. Indeed, the liquid phase can be simply a carrier for ultrafine powder, or a protection against oxidation in the case of metals, or a protection for health in the case of whiskers, for instance. It can also take a part in chemical reactions when the liquid phase is a solution of chloride, nitrates... or it can be an organic liquid for the synthesis of carbide, where CO is a strong reducer. Furthermore the liquid phase can also release some energy because of its combustion at the very end of the process. It can also change the local atmosphere surrounding the in flight droplets in the plasma where it is possible to use H2O2 as a carrier in order to increase the oxygen partial pressure around sensitive to oxygen decomposition materials. The applications of SPS are in the powder synthesis (in R&D or production), in the spraying of metals, ceramics or composites directly synthesized, or in production of very reactive with air materials. Applications of SPS will be presented for hydroxyapatite (HA) and NiAlMo. Induction plasma SPS coatings and/or powders properties will be discussed as a function of the SPS process variables.
A New Electromagnetic Powder Deposition System
Authors: Bacon J.L. , Davis D.G. , Polizzi R.J. , Sledge R.L. , Uglum J.R. , Zowarka R.C. 
Published: May 2021

Abstract
Existing state of the art thermal spray processes (HVOF, D-Gun, Plasma Spraying) are limited to powder velocities of about 1 km/sec because they rely on the thermodynamic expansion of gases. A new thermal spray process using electromagnetic forces can accelerate powder particles to a final velocity of up to 2 km/sec. At this velocity powder particles have sufficient kinetic energy to melt their own mass and an equivalent substrate mass on impact. The process is based on railgun technology developed by the Department of Defense. A railgun is filled with argon gas and a high energy electrical pulse, provided by a capacitor bank, drives the gas down the railgun to a final velocity of up to 4 km/sec. This gas passes over a powder cloud and accelerates the powder through drag forces. The electrical and powder discharge frequency can be adjusted so that the deposition rate and thermal input to the substrate can be controlled.