bluuebunny/crossref_metadata_2025 huggingface dataset:
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

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

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

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

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

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

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

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

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

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

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

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

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

Suspension Plasma Spraying (SPS) is a thermal spray process based on a suspension of fine (<10 μm) or even ultrafine (<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

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.
The Diagnostic History of a New Electromagnetic Powder Deposition System
Authors: Bacon J.L. , Davis D.G. , Sledge R.L. , Uglum J.R. , Zowarka R.C. , Polizzi R.J.
Published: May 2021

This paper describes the diagnostic tools used in the development of a new electromagnetic powder deposition system. The instrumentation, interpretation of data, and subsequent decisions regarding the direction of system development are discussed. Important system parameters, their impact on system performance, and techniques to measure them are presented. The electromagnetic powder deposition system is based on railgun technology developed by the Department of Defense. The system drives an ionized plasma sheet down the length of a railgun, reaching a final plasma velocity of 4 km/sec. The high velocity plasma, in turn, snowplows [1] a shock compressed gas column in front of it. This gas column sweeps through a powder cloud and accelerates it by viscous drag to a final velocity of 2 km/sec. Important system parameters include particle velocity, gas velocity, gas column pressure, and plasma propagation and velocity. Diagnostic tools include pressure transducers, a high speed digital framing camera, fiber optics and magnetic probes.
Ceramic and Metallic Powder Spheroidization Using Induction Plasma Technology
Authors: Dignard N.M. , Boulos M.I.
Published: May 2021

A study is carried out of the spheroidization of ceramic and metallic powders using induction plasma technology. The process is based on the central injection of the powder in the plasma discharge followed by the in-flight cooling and solidification of the molten droplets prior to their collection at the bottom of a stainless-steel water cooled chamber. The degree of spheroidization is evaluated using image analysis. The results are correlated as a function of the powder feed rate, the plasma operating conditions and the thermophysical properties of the powders treated. The model's fit to the obtained experimental data is very good. The results show that the technology can be successfully used for the spheroidization and densification of a wide range of materials.
Plasma Spraying of Silicates
Authors: Chráska P. , Neufuss K. , Kolman B. , Dubsky J.
Published: May 2021

A search for cheap spraying materials offering interesting properties is conducted in connection with utilization of the high throughput water stabilized plasma. In this regard very promising materials are silicates. WSP PAL 160 was used for spraying garnets in their natural form and fused and crushed basalt. Chemical composition of both these materials is based generally on the same components but their contents are different. Paper reports on the spraying parameters used and then describes the structure and phase composition of deposits as well as their selected properties. Garnet of almandine type can be sprayed very well at a wide variety of parameters while pyrope type spraying is more difficult. Very interesting coatings were made of basalt.
Vaporization and Ultra-Fine Particle Generation during the Plasma Spraying Process
Authors: Gross K.A. , Fauchais P. , Vardelle M. , Tikkanen J. , Keskinen J.
Published: May 2021

The thermal spray process melts powder at very high temperatures and propels the molten material to the substrate to produce a coherent deposit. This heating produces a certain amount of vaporization of the feedstock. Upon exiting the plasma plume the fast cooling conditions lead to condensation of the vapor. An electrical low pressure impactor was used to monitor the concentration of ultra-fine particles at various radial and axial distances. Metal, namely iron powder, showed very high concentration levels which increase with distance. Ultra-fine particles from ZrO2-8Y2O3 reached a peak concentration at 6 cm. Use of an air barrier during spraying decreases the population of ultra-fine particles facilitating the production of a stronger coating.
Plasma Processing of Functionally Graded Materials Part I: Process Diagnostics
Authors: Smith W.C. , Jewett T.J. , Sampath S. , Swank W.D. , Fincke J.R.
Published: May 2021

An investigation into the dependency of the formation of functionally graded materials (FGMs) on process variables was carried out. The initial stage of the investigation involved a complete analysis of the plasma spray parameters used in the fabrication of an FGM constructed of NiCrAlY and partially stabilized zirconia (PSZ). In flight particle temperature, velocity and trajectory data were gathered for individual powders, as well as mixtures of the particle species, over a range of spray parameters. This data was combined with material specific properties such as flowability, apparent density, particle morphology and size distribution. The end result of the studies allowed for size matching of the particle species so as to ensure both species were molten at the nominal spray distance and possessed coincident impact velocities. Following the initial investigation, two spray conditions were selected for further analysis. Individual layers of specific powder mixture ratios were deposited as well as a complete FGM structure. The resulting structures were then compared based on their deposition efficiencies, porosity levels, compositional homogeneity and microstructures.
Engineering Formulas for Flattening of Composite Powder Particles during Thermal Spraying
Authors: Sobolev V.V. , Guilemany J.M. , Martín A.J.
Published: May 2021

Engineering analytical formulas describing variations of the final values of the splat thickness and radius during flattening of composite particles in thermal spraying are obtained. The effective values of the droplet parameters (impact velocity and viscosity) and the Reynolds number are introduced taking into account a composition of the composite particles. Analytical results obtained agree well with the experimental data available.
Scale-Sensitive Fractal Analysis for Understanding the Influence of Substrate Roughness in Thermal Spraying
Authors: Siegmann S.D. , Brown C.A.
Published: May 2021

It is widely recognized that substrate surface roughness, or topography, plays an important role in droplet-substrate interaction and the adhesion of sprayed coatings. A key difficulty in understanding the role that topography plays during droplet impact, wetting and solidification has been the availability of methods for appropriate characterization of the topography. The complex nature of the substrate topographies cannot be adequately characterized by conventional methods such as Ra. In this work, scale-sensitive fractal analyses are considered for advancing the understanding of roughness of grit blasted surfaces in thermal spray applications. Area-scale analysis is performed on 3D data sets acquired from different grit-blasted substrates. From fractal analysis it is known that the apparent area of a rough surface increases as the scale of observation decreases. The area-scale relations are used to guide experimental design for topographical data acquisition and analysis and to better understand the influence of grit blasting on substrates for thermal spray. The potential of these scale-sensitive analysis techniques to fulfill the above bases for supporting statistical correlations and clear physical interpretations is discussed.
Influence of CaSi2 and Si Additions on Properties of Coatings Produced by Plasma Spraying of Composite Powders
Authors: Borisov Yu. , Borisova A. , Tunik A. , Knyaz M. , Bobrik V.
Published: May 2021

Addition of CaSi2 in steel melt leads to a decrease of oxygen content, an increase of the melt flow capability, an improvement of a metal ductility and weldability. For an estimation of CaSi2 and Si additions effect in conditions of thermal spraying composite powders were produced. A base material of these powders particles is nickel, nichrom and iron. CaSi2 and Si are additional components of the powders (3-12 wt. %). Plasma coatings produced with using of these powders exhibit high density and adhesion. The coatings structure has a high grade of microcrystallinity with a decreasing size of lamels. Oxides content in the coatings decreases with an increasing of CaSi2 and Si content in the composite powders, moreover this effect is more essential in case of CaSi2 addition. Addition of CaSi2 and Si to Ni-base coatings increases a microhardness from 1900-2000 MPa to 2200-2850 MPa. In case of NiCr-base coatings this increasing is from 1800-2100 MPa to 2400-3500 MPa.
Characterization of Cr2O3-TiO2-CaF2 Coatings Using Plasma Spray Process
Authors: Ilyuschenko A.Ph. , Shipica N.I. , Vityaz P.A. , Yerstak A.A. , Beliaev A.Y.
Published: May 2021

This paper presents the results of a study on the wear resistance of plasma spray coatings made from Cr2O3-TiO2-CaF2 powders. The composite powders used were produced by self-propagating high temperature synthesis. They were then applied under various conditions in order to optimize the material system, spray process, and application procedures. Based on the results of microstructural examination and wear testing, the thermally sprayed composite coatings have excellent wear resistance, good adhesion, and are self-lubricating at high temperatures.
Elastic Modulus Measurements in Plasma Sprayed Deposits
Authors: Wallace J.S. , Ilavsky J.
Published: May 2021

A technique has been developed to characterize the elastic modulus of zirconium oxide - 8 % yttrium oxide plasma sprayed deposits. A commercial hardness indenter has been modified to record load - displacement as a spherical ball is elastically loaded onto the surface of the material to be measured. The resulting data are used to calculate the elastic modulus. Since the loads used are in the elastic region, the technique is, in theory, nondestructive. Relatively small areas of the material, approximately 50 μm in diameter, are sampled by the indenter, allowing local mapping of elastic modulus variations throughout the deposit. Using this technique, elastic modulus variations have been measured through the thickness of the deposit. Also, different moduli were measured in the cross-section and through the thickness and these differences are correlated with the microstructure. Finally, significant increases in elastic modulus have been found in samples annealed for 2.5 h at 1100°C. These changes have been correlated with small angle neutron scattering measurements of void surface area.
Influence of WC Particle Size and Matrix Composition on the Behavior of WC-Co-Cr Coatings Sprayed by the HVOF Process
Authors: Berget J. , Bardal E. , Rogne T.
Published: May 2021

WC-Co-Cr powders with different WC particle size have been sprayed by the HVOF process. At constant spraying conditions the powders give coatings of different quality. The deposition efficiency during spraying of powders containing large WC particles was found to be low compared to powders with finer WC grains. In addition the amounts of porosity and cracks were different. The coatings have been characterised by different methods. Erosion and erosion-corrosion tests showed that the WC particle size also influence the wear resistance of the coatings. Small WC particle size was found to be beneficial. Chemical composition of the matrix was also found to be decisive for the coating properties. An increase of the chromium content improved the erosion-corrosion resistance.
Residual Stress Measurement in Plasma Sprayed Coatings by X-Ray Diffraction
Authors: Matejicek J. , Sampath S. , Dubsky J.
Published: May 2021

Processing induced residual stresses play an important role in the performance of thermally sprayed coatings. Their precise determination is a key to influence the coating properties by modification of process variables and to understand the processing-property relationship. Among various methods for residual stress measurement, x-ray diffraction holds a specific position by being nondestructive, phase distinctive, localized and applicable for real parts. The sin2ψ method is commonly applied for bulk materials as well as coatings. However, the results are often reported without sufficient experimental details and the method is used in its simplified form without justification of certain assumptions. In this investigation, the sin2ψ x-ray diffraction method was used to measure residual macrostress in plasma sprayed Ni, NiCrAlY and ZrO2+8%Y2O3 coatings. Reproducibility of the method was tested and the assumptions allowing its use are discussed and experimentally verified. For Ni coatings, a comparison with blind hole and neutron diffraction measurements is presented. The results are discussed with respect to processing, structure and properties of the coatings.
Methods of Determination and Control of Residual Stresses in Plasma Spray Coatings
Authors: Dekhtyar L. , Kleyman A. , Andreychuk V. , Berman S.
Published: May 2021

Residual stresses exert profound influence on the longevity of parts with thermal spray coatings. The distribution and value of the residual stresses depend on method of coating deposition, composition of the applied material, parameters of thermal spraying and methods of post-treatment. Therefore, the study of the influence of the various technological factors on the residual stresses in the plasma spray coatings is very important. Due to heterogeneity of the coating, residual stresses can be determined only by the experimentation by using new methods which take into consideration real values of elastic characteristics and density of elementary layers. Methods and formulas for the calculations of the residual stresses in coatings deposited on bars, rings, discs, cylinders are presented. Experimental results for the various thermal spray coatings are also shown. These results can be used for the optimization of coating deposition and would supplement the existing database.
HVOF-Sprayed Alloy In718 – The Influence of Process Parameters on the Microstructure and Mechanical Properties
Authors: Voggenreiter H.F. , Huber H. , Spies H.-J. , Baum H.
Published: May 2021

New near-net-shape structures of alloy Inconel 718 processed by HVOF spraying require optimum mechanical properties. Dominant factors defining the material quality are the particle properties velocity and temperature adjusted by the HVOF process parameters. Based on theoretical analysis of the HVOF process, experiments were performed with a defined variation of primary process parameters, producing coating samples of alloy 718 and measuring the particle velocities. Microstructural and X-ray analysis shows that in coatings with a high fraction of molten phase and high velocity, mainly divalent and spinell-type oxides are formed during particle impact on the substrate. Due to severe oxidation of the y'/y''- forming elements Ti, Al and Nb, precipitation-hardening effects of In 718 coatings are low. This leads to merely mediocre mechanical properties. The reduction of the molten phase to nearly zero leads to a drastic decrease of the oxide formation. The hardening γ'/γ'' phases are precipitated homogeneously in the Ni-base matrix. Strength values comparable to cast and wrought alloy In718 are attained by spraying with a low molten-phase fraction and high particle velocity. However, extensive intergranular 8-phase precipitation due to too high an Nb content of the powder causes only mediocre fracture elongation. Coatings up to 10 mm thick have been sprayed. The construction effort and hence the costs and weight of combustion chambers for hypersonic propulsion systems are to be reduced through direct thermal spraying of the loadbearing metallic pressure jacket onto the tubular cooling system. As a semifinished product, the selected Inconel 718 alloy exhibits good mechanical properties in the cryogenic temperature range as well as under higher thermal loads, and is commercially available in powder form. Aging serves to increase the strength up to the range of 1,200 N/mm2. For the sprayed In718 version, coating thicknesses in the centimeter range, a porosity < 1% and mechanical properties comparable with those of the cast version are required. The objective of the research work is to optimize spray-process control so that the resultant structural thick layers meet the design as well as the material requirements with respect to combustion-chamber technology. This necessitates elaborating the dominant microstructural parameters influencing the mechanical properties and the effect on them of the spraying process, and correlating them with the particle-condition parameters and the process parameters [1].
High Velocity Oxy-Fuel Thermal Sprayed Coatings as Alternates to WC-12Co Coatings and Chromium Plating
Authors: Mutasim Z. , Banker V. , Rimlinger C.
Published: May 2021

Tungsten carbide-12 wt.% cobalt (WC-12Co) coatings and chromium plating are used to provide wear resistant surfaces in gas turbine applications. These treatments provide surfaces with hardnesses greater than 60 Rockwell C. In addition, a surface finish better than 8 microinches RMS is required for optimum performance. To achieve this surface finish, diamond grinding is required. The diamond grinding step adds considerable cost to the product and economical benefits could be achieved if more conventional grinding techniques were incorporated. A program was initiated to develop an alternative thermal spray coating, with a target hardness lower than 60 Rockwell C, but high enough to provide the wear resistance required. Spray development was conducted on five commercially available materials using the Diamond Jet 2600 high velocity oxy-fuel process. Laboratory evaluation included coating microstructure, macro- and microhardness, bond strength, salt spray corrosion, and cyclic compression tests.
WC-Co Detonation Coatings Having a Hybrid Amorphous-Nanocrystalline Structure Display Improved Properties
Authors: Shmyreva T. , Britun V.
Published: May 2021

X ray diffraction and transmission electron microscopy studies and measurements of hardness and void content were carried out for WC-20% Co coatings produced by detonation flame spraying at various oxygen/acetylene ratios in the detonating gas mixture. It was demonstrated that successive transition from (WC+Co) to (W2C+Co3W3C) to (W+CO7W6) occurs as the oxygen content in the mixture is increased, and that amorphous-nanocrystalline structures form in the coating. Two types of these hybrid structures were revealed, one including an amorphous metallic matrix containing precipitates of intermetallic nanocrystals, the other having an amorphous oxide matrix and nanocrystalline precipitates of CO3O4 and WO3. The hybrid structures were shown to improve coating density and hardness.
Structure-Property Relationships of TiC-Ni+Ti and (Ti,W) C-Ni Powders Manufactured by the SHS Process, and the Resultant HVOF-Sprayed Coatings
Authors: de Paco J.M. , Nutting J. , Guilemany J.M. , Sánchez F.J. , Miguel J.P. , Smith P.
Published: May 2021

The technology of thermal spraying is approaching maturity, and in the quest to reduce production costs whilst maintaining coating quality, attention is turning increasingly to more cost-effective routes for the manufacture of the starting powders. One such route is self-propagating high-temperature synthesis (SHS), which reduces the required energy input for powder production. In this work, TiC-Ti+Ni and (Ti, W)C-Ni powders produced by the SHS process have been studied in the as-received and as-sprayed states, to evaluate the suitability of SHS powders for the production of wear-resistant coatings. The starting powders and the coatings produced by atmospheric-plasma and HVOF spraying have been characterised using analytical (XRD, EDS) and microscopical techniques (optical, SEM). The technological properties of the as-sprayed coatings have also been characterised, including hardness, wear resistance (using a Rubber-Wheel test (ASTM G-65)) and corrosion resistance (in marine water environment).
The Effect of Mounting Technique on the Microstructure of Thermal Barrier Coatings
Authors: Sauer J.P. , Leonhardt T. , Geary A.R.
Published: May 2021

The characterization of a thermal barrier coating (TBC) using routine metallographic methods has had investigators uncertain as to the authenticity of the microstructure concerning porosity, cracking and other features. Mounting is a very important step in the process. A greater understanding of relationships between high and low viscosity mounting epoxies exposed to vacuum impregnation, pressure impregnation procedures (PIP), and the combined methods is the goal of this paper. This study will attempt to show how variations in sample mounting procedures will affect the final results in conjunction with varied metallographic procedures.
The Effects of Manual vs. Semi-Automatic Metallographic Specimen Preparation of Thermally Sprayed Coatings
Authors: Blann G.A.
Published: May 2021

If the microstructure of thermally sprayed coatings is to be accurately evaluated, proper metallographic specimen preparation techniques need to be utilized to reveal the true coating characteristics. Variations of the materials used and the method of application on a substrate requires variations in the metallographic preparation procedure. The ASTM and Best Recommended Practices Committee of TSS are developing metallographic standards for thermally sprayed coatings using semi-automatic or automatic preparation equipment There are laboratories that continue to prepare coating specimens manually due to an inability to upgrade their equipment, and they must meet industry standards of evaluation. The purpose of this paper is to assist these laboratories in manual preparation that will enable them to produce accurate coating characteristics.
Dutch Progressive Jews and Their Unexpected Key Role in Europe
Authors: Brasz Chaya
Published: May 2021

Liberal Judaism remained absent in the Netherlands during the nineteenth century but finally became successful in the early 1930s under the influence of the Liberal Jewish Synagogue in London and the establishment of the World Union for Progressive Judaism in 1926. It had a specific Dutch character which was more radical than the German refugees who joined in were used to. The Shoah barely left survivors of the prewar congregations, but Liberal Judaism made a remarkable comeback in the Netherlands and had a key role position for Liberal Judaism on the continent of Europe. In a much smaller Jewish community than the French one, the Dutch Progressive congregations for a considerable period formed the largest Progressive community on the continent, next to France. Even today, while comprising ten congregations, it still has a growing membership.
Progressive Judaism in Austria
Authors: Adunka Evelyn
Published: May 2021

The article describes the historical circumstances and context of the beginnings of Progressive Judaism in Central Europe in the nineteenth century, with the rabbis I.N. Mannheimer and A. Jellinek and the famous cantor Salomon Sulzer in the historic Viennese city temple (which still stands today) as the main protagonists. In the interwar period, the founding of the Verein für fortschrittliches Judentum in Vienna, its president Heinrich Haase (1864–1943) and its dissolution (in 1936) are discussed, and biographies of Liberal rabbis in Vienna and in some parts of the Austrian provinces are presented. After 1945 the focus is on the history of the Liberal Viennese community Or Chadasch, founded in May 1990, which is celebrating twenty-five years in November this year with a Festschrift and a Festakt with a keynote speech by Anat Hoffman.
Prayer Book Reform in Europe, Continued
Authors: Boeckler Annette M.
Published: May 2021

The classic bibliography of European Progressive prayer books appeared in 1968 (Jakob J. Petuchowski, Prayerbook Reform in Europe). It provided a chronological bibliography of prayer book publications in Europe from the very first in 1816 until ‘The Service of the Heart’, published in 1967. Based on these sources Petuchowski depicted the typical features of Progressive Jewish liturgy and their developments. European Progressive Jewish liturgy has developed a lot since then. During the last forty-eight years several new liturgical issues and themes arose. These will be described in the second part of this article. The first part aims to present a complete chronological bibliography of European Progressive liturgy from 1967 till 2015.1
The Ninetieth Anniversary of the World Union for Progressive Judaism
Authors: Hirsch Richard G.
Published: May 2021

The ninetieth anniversary of the World Union enables us to highlight our achievements. In 1973 we moved the international headquarters from New York to Jerusalem and built a magnificent cultural/educational centre there. We pioneered the development of a dynamic Reform/Progressive movement in Israel consisting of congregations, kibbutzim, an Israel religious action centre and educational, cultural and youth programmes. We became active leaders in the Jewish Agency for Israel and the World Zionist Organization. We established synagogues and educational programmes in the Former Soviet Union, Europe, Latin America and the Far East, thus fulfilling our mandate to perpetuate Jewish life wherever Jews live. We formulated an ideology of Reform Zionism as an antidote to the contracting Jewish identity induced by contemporary diaspora conditions. Whereas we encourage aliyah for Jews who want to live in Israel, we are adamantly opposed to those who advocate aliyah as a positive response to anti-Semitism. Instead, we demand that European democracies guarantee equal rights and full security to Jews as well as to all other groups in society.
Liberale Judentum and British Reform Jews
Authors: Bayfield Tony
Published: May 2021

Two narratives dominate British Jewry: (1) Do not get too close to wider society or you will assimilate physically and theologically; and (2) The only future for Jews is in Israel. Ned Curthoys in The Legacy of Liberal Judaism identifies the German Liberale tradition as offering a third option – engagement. First, engage both to learn from wider society and contribute distinctively to it. Second, question the justice of society out of the Jewish experience of injustice. Third, include uncomfortable minorities and subversive voices; do not create pariahs. Fourth, maintain a cautious optimism about collaborating beyond narrow nationalisms to create a better society. It is possible this alternative has been proven vain by history but we have no alternative but to try again. It is not a comfortable place but it is a good place to be.
Queer Jews Talking Their Way in
Authors: Adler Rachel
Published: May 2021

A tradition is a centuries-long conversation about the goods and concerns of the philosophical or religious systems in which these goods and concerns inhere. LGBTQ Jews are the latest newcomers to Judaism’s conversation. Entering an established conversation places stressful demands upon incomers and veteran participants alike but enlarges and enriches the discourse. LGBTQ participants bring new topics and categories concerning gender that challenge participants of longer standing. Bringing to the existing categories and topics of the tradition experiences of which it was unaware implicitly requires that those topics be reexamined in the light of new data and situations. All this revitalizes the conversation.
A Totem and a Taboo
Authors: Schonfield Jeremy
Published: May 2021

This article discusses two academic events devoted to Holocaust studies in which participants became unconsciously involved in re-enacting the behaviour respectively of Holocaust perpetrators, and of victims turning aggressively on each other in a manner reminiscent of ghetto life. In one conference an out-group was created and silenced, while in another an individual became the object of projected guilt and was victimized. These projections were mediated by implied competition between film, sculpture and literature as the medium best suited to Holocaust memorialization. A description of each event is followed by analyses of the dynamics involved, with the support of psychoanalytic literature. Factors which led to the author’s twenty-year delay in publishing the article, which was drafted in 1995, are also examined psychologically.
The Concept of the Victim in Midrashic Literature
Authors: Weinberg Joanna
Published: May 2021

The creative authors of the Midrashim treated the topic of ‘the persecuted’ or ‘the victim’ in a constellation of fascinating homilies on the lectionary portion for Passover. This short article will examine how the theme of persecution is elaborated in various midrashic texts, and point to similarities between rabbinic exegesis and Jewish Hellenistic and Christian Syriac discussions of the same theme.
Religion and Organisation
Authors: Blue Lionel
Published: May 2021

This conference sermon delivered to the UK Reform Jewish movement (Reform Synagogues of Great Britain) in 1965 explored the challenges facing this growing religious organisation, ‘a worldly instrument to serve non-worldly purposes’. What are the traps that have to be recognized and avoided? Does God become the rationalization for our prejudices? How do we relate to issues in the Jewish and wider world? Inside the complex bureaucratic system, how do we find place for the freedom of religious experience?
Convening
Authors: Blue Lionel
Published: May 2021

In this article, Lionel Blue describes the role played by the Beth Din, the Jewish religious court, of the UK Reform Jewish movement, of which he was the Convenor. He writes with humour of the way he tried to humanize what might otherwise be a strange and daunting experience for people. The court deals with conversion to Judaism, issues of Jewish status, legal matters associated with divorce. He describes the emphasis that has to be placed on supporting the individuals facing these deeply personal life-changing situations. Beyond the purely traditional legal issues and formality, greater attention and understanding should be given to the relationships people actually enter into today, and to the people themselves, their needs and their possibilities.
Inklings
Authors: Blue Lionel
Published: May 2021

The three essays collected here are occasional pieces Lionel Blue contributed to the magazine Manna, The Forum for Progressive Judaism, edited by Rabbi Tony Bayfield. They address: his experience visiting monasteries and convents, his observations and what he gained from them; the changing stages in Jewish-Christian dialogue and what the next steps might be; the paradoxes of religion and the temptations of idolatry.