bluuebunny/crossref_metadata_2025 huggingface dataset:
Wear Evaluation of Plasma Sprayed Oxide and Carbide Coatings
Authors: Ding C. , Li J. , Zhang L. , Yu X.
Published: May 2021

Wear of plasma sprayed Cr2O3 TiO2, Cr3C2-NiCr and WC-Co coatings have been evaluated with a block-on-ring arrangement under dry and lubricated conditions. The results indicated that the wear of the coatings was interpreted in term of subsurface grain fracture which was related to the special microstructure of the coatings such as size, shape and distribution of pore as well as crack. Among the four kinds of coating, Cr2O3 coating possesses the lowest wear coefficient. Water accelerated cracking and fracturing and deteriorated the wear resistance of both Cr3C2-NiCr and TiO2 coatings. Ethanol reduced the wear of Cr3C2-NiCr coating, which was attributed to the formation of a smooth surface film mainly consisting of Cr2O3. Wear of Cr2O3, coating against an Al2O3 ball at high temperature has been also produced. The wear of Cr2O3 coating against Al2O3 ceramics decreased with increase in temperature and load. The reaction between Cr2O3 coating and Al2O3, ceramics at high temperature and the formation of a protective film consisting of Cr2O3, Al2O3 and SiO2 glass on the surface of Cr2O3 coating improved the wear resistance of Cr2O3 coating.
Synthesis and Characterization of Nanocrystalline 316-Stainless Steel Coatings by High Velocity Oxy-Fuel Spraying
Authors: Lau M.L. , Jiang H.G. , Lavernia E.J.
Published: May 2021

The present paper describes the synthesis of nanocrystalline 316-stainless steel coatings by high velocity oxy-fuel (HVOF) thermal spraying. The feedstock powders were synthesized by mechanical milling to produce flake-shaped agglomerates with an average grain size of less than 100 nm. The powders were introduced into the HVOF spray to successfully produce nanocrystalline coatings. X-ray diffraction analysis and transmission electron microscopy were used to determine the average grain size of the milled powders. Scanning electron microscopy and transmission electron microscopy were used to study the morphology of the nanometric particles and the microstructure of the as-sprayed coatings. The properties of various coating materials were characterized by microhardness measurements performed on the polished surface of the cross section.
Numerical Modeling of an Impinging Dusted Plasma Jet Controlled by a Magnetic Field in a Low Pressure
Authors: Nishiyama H. , Kuzuhara M. , Solonenko O.P. , Kamiyama S.
Published: May 2021

The present study is conducted to clarify the magnetic control characteristics of a particle-laden plasma jet impinging on a substrate for the improvement of a low pressure plasma spraying process and its controllable optimization. The plasma jet is described by Eulerian approach and each injected particle is described by Lagrangian approach respectively taking into account the compressible effect, variable transport properties and plasma-particle interactions, coupled with the Maxwell's equations. The effects of the location of the applied radio-frequency electromagnetic field, and of the injected particle size on the particle trajectory, particle velocity and its phase change are clarified by numerical simulation. It is concluded that the particle trajectory is influenced effectively and the injected particle temperature can be controlled strongly by applying the radio-frequency electromagnetic field to the nozzle. The reasonable agreement of particle velocity between calculation and experiment is observed.
Plasma Spraying with Atmosphere and Temperature Control: Cryogenic Flux Modeling
Authors: Meillot E. , Legeay O. , Richet J.N.
Published: May 2021

Production of ceramic coatings by plasma spraying on thermally sensitive substrates requires a hard cooling onto the substrate immediately after the plasma and particles jet getting-through. That implies a cryogenic cooling spray. In order to have a better understanding of thermal transfer between cryogenic droplets and substrate, we simulate with a home-made software, PARTIX, the transport of pulverized jet in the atmosphere and calculate the droplet size distributions impacting the substrate. Knowing that, we can determine the thermal flux. Simulations of different pulverized flows are presented.
Thermal Spray Quasicrystalline Coatings Part I: Relationships Among Processing, Phase Structure and Splat Morphology
Authors: Sordelet D.J. , Besser M.F. , Kramer M.J.
Published: May 2021

A study was performed to examine the effects of starting powder composition, substrate thermal conductivity, and substrate temperature on the composition and structure of individual Al-Cu-Fe splats formed during thermal spraying. The fraction of quasicrystalline phase which formed was found to depend on the chemistry and solidification history of the splats. Due to evaporative loss of Al during spraying, an initial powder composition higher in Al produced splats closer to the desired composition, which yielded more of the quasicrystalline phase. Deposition onto lower thermal conductivity surfaces resulted in an increase in the quasicrystalline phase, as did solidification onto higher temperature substrates.
Effect of Particle-Substrate Materials Combinations on Morphology of Plasma Sprayed Splats
Authors: Li C.J. , Li J.-L. , Wang W.-B. , Ohmori A. , Tani K.
Published: May 2021

The structure and morphology of plasma sprayed splats are experimentally investigated using different droplet materials and substrate materials. Droplet materials include aluminum, copper, nickel and refractory metals such as molybdenum and tungsten, and substrate materials include aluminum, stainless steel, and molybdenum plates. The results show that the splashing occurs during the splatting of a completely molten droplet. Most splats formed by droplets molten completely are only central part of the ideal disk type ones, which are defined as the annulus-ringed disk-like splat. It is found that the morphology of such annulus-ringed disk-like splat is greatly influenced by the combination of droplet and substrate materials depending on whether substrate melting occurs. With the combinations of droplet and substrate materials which are of similar thermal properties the splashing of central area of splat tends to occur to present a honeycomb structure at the center of splat. When droplet impacting can cause melting of substrate annulus-ringed splat prefers to present a split type. The flattening ratio of an annulus-ringed disk splat is typically less than 2.
Morphology of Splats of Thermally Sprayed Coatings
Authors: Sobolev V.V.
Published: May 2021

Different mechanisms of splashing of droplets impacting onto the substrate surface during thermal spraying are considered. It is shown that supercooling formed in the flattening droplet consists of the thermal supercooling and that arisen due to the high pressure developed upon the droplet impact. Solidification starts when the supercooling exceeds some critical value. With a "cold" substrate when its temperature is less than a transition temperature the marked contribution to the supercooling is due to its high pressure part. In this case a regular disc-shaped splat will be formed in the central part of the flattening droplet and splashing will occur in the periphery. With a "hot" substrate when its temperature exceeds the transition temperature the thermal supercooling is high enough, no splashing occurs and a regular disc-shaped splat is formed. Theoretical results agree with the experimental observations.
Degradation of In-Flight PMMA Particles During Thermal Spraying
Authors: Zhang T. , Gawne D.T. , Bao Y.
Published: May 2021

Kinetic and heat transfer analysis have been undertaken in order to predict the decomposition of polymer feedstock particles during thermal spraying. Thermogravimetric measurements indicated that the decomposition of PMMA had an order of reaction of unity and an activation energy of 135 kJ mol-1. The polymer decomposition temperature is shown to be a function of the particle residence time in the flame and is much higher than in conventional polymer processing. This has an important influence on process modelling, since the choice of decomposition temperature used in the heat transfer analysis has a major effect on the calculated temperature profiles. The work shows that realistic predictive data can only be obtained by using the dynamic decomposition temperature. Application of the model indicates that only the surface layers of the polymer feedstock particles undergo significant decomposition during plasma spraying and that the feedstock injection position is an important control parameter.
Evaluation of Fatigue Strength of WC Cermet- and 13Cr Steel-Sprayed Materials and Their Coatings
Authors: Ogawa T. , Tokaji K. , Ejima T. , Kobayashi Y. , Harada Y.
Published: May 2021

Rotating bending fatigue tests have been conducted at room temperature in laboratory air using specimens of medium carbon steel (S45C), low alloy steel (SCM435) and titanium alloy (Ti-6AI-4V) with HVOF sprayed coating of a cermet (WC-12%Co) and S45C with WFS sprayed coating of a 13Cr steel (SUS420J2). Plane bending fatigue tests were also conducted at stress ratios, R, of -1, -0.5 and 0 for S45C with WC-12%Co coating. The fatigue strength and fracture mechanisms were studied. The fatigue strength evaluated by nominal stress was strongly influenced by substrate materials, R and the thickness of sprayed coatings. Detailed observation of crack initiation on the coating surface and fracture surface revealed that a crack was initiated in the coating and then cracks were initiated in the substrate due to the stress concentration of the crack in the coating. The fatigue strength of the sprayed materials was dominated by that of the sprayed coating. Therefore, the fatigue strength could be evaluated uniquely in terms of the true stress on the coating surface. The influence of compressive residual stress of the sprayed coatings on fatigue strength was discussed based on the fatigue mechanisms at different stress ratios.
Impact Evaluation of Plasma Spray Coatings
Authors: Shao T.M. , Xu D.J. , Luo J.G. , Wu C.-J.
Published: May 2021

Impact performance of plasma spray coatings is usually evaluated by means of surface observation after impact action. As a matter of fact, the dynamic response characteristics of coatings in the course of impact action are also very important. In this paper, a method of response frequency spectrum analysis is developed for the impact evaluation of plasma spray coatings. An impact test machine, in which the impact load is generated by a pivot-rod-lever system, is specially designed, allowing both single impact test and repeated impact test. The frequency spectra of Cr2O3 ceramic coating and WC-Co17% alloy coating under single and repeated impact action are analyzed. The results show that there is an obvious relationship between the impact performance and the impact response frequency spectrum. Abrupt changes in the coating, such as appearance of surface cracks and surface damage, correspond the sudden changes of the response frequency spectrum.
Internal Stresses in Plasma Coatings with an Amorphous Structure
Authors: Borisov Y. , Korzhyk V.
Published: May 2021

This paper examines the stress state of plasma-sprayed amorphous coatings of Fe-B with additions of Ni, Cr, and Mo. Internal stresses depend on the type of plasma gas used, the thickness and composition of the coating, and the material and temperature of the substrate. In this study, additional cooling of the substrate was found to be the most efficient way to reduce internal stresses. Amorphous coatings were also found to improve fatigue strength by as much as 25-30%, which is attributed to the formation of compressive stresses in the coating layers adjoining the substrate.
Quantities and Properties of Layers Sprayed with Cored Wire of Type Fe-Cr-C
Authors: Drzeniek H. , Milewski W.
Published: May 2021

Results of macro- and microhardness investigations of newly developed coatings are presented in this paper. The coatings were produced with flame- and arc spraying technique. The coating structure and hardness is significantly influenced by the spraying method and spraying parameters. It will be shown that properties for flame sprayed coatings are more effected by parameter variations than for arc sprayed coatings. A higher hardness, a greater density and a better particle cohesion can be obtained by using the arc spraying method.
Measurement Technology for Inflight Particle Diagnosis in Plasma Spraying
Authors: Schutz M. , Barbezat G. , Fluck E.
Published: May 2021

A new measurement technology in plasma spraying has been established at SULZER METCO AG, Switzerland. Based on the principle of C. Moreau, CNRC, it is now possible to simultaneously measure surface temperature and velocity of melted particles in a plasma flame. Since temperature and velocity are two of the most important parameters affecting coating characteristics in the thermal spray processes, the knowledge and control of these parameters offers new methods and assistance in the development of coating solutions. The object of this paper is to outline some important measurement results, to show correlations to splat formation and coating characteristics and to demonstrate applications in an industrial environment.
The Influence of Several Powder Feed Parameters on Feed Precision and Continuity
Authors: Huang X. , Xu L. , Ma X. , Fan B. , Yin X.
Published: May 2021

This paper provides a summary of conventional thermal spray powder feeders, examines the influence of carrier gas flow, powder tube diameter, powder tube type, and gas flow path on the feed precision and continuity of pressure-type powder feeders, and discusses the cause of pulsation associated with the injection of super fine ceramic powders.
Measurement of Spraying Particle Behaviors by Three-Intensified-Sensor Color High Speed Video Camera System
Authors: Yamakawa M. , Oki S. , Gohda S.
Published: May 2021

A high-speed video recording system was developed to measure the velocity and temperature of thermal spray particles in flight. The system consists of three image sensors and a cubic beam-split prism that directs light, based on color or wavelength, to three imaging planes. In this study, one of sensors is used to measure particle velocity while the other two measure particle temperature. The prospect of simultaneously measuring the temperature and velocity of individual particles in flight is discussed along with the insight it provides on the formation of spray coatings.
Comparison of Different Fuel Gases in HVOF
Authors: Gourlaouen V. , Verna E. , Sattonnet J.
Published: May 2021

Although high-velocity oxyfuel (HVOF) spray coating is a relatively new thermal spraying process, interest is growing rapidly along with the pace of development in areas such as torch design, powder quality, and modelling. The gases used in HVOF spraying are also important because they directly influence the state of the particle striking the substrate. This presentation reviews the HVOF combustion process with an emphasis on the gases used and their influence on coating quality.
Research on Heavy-Loading Thermal Spray Turntable with High Precision and Self Controlled Frequency Conversion
Authors: Huang X. , Xu L. , Wang R. , Wang J. , Yin X.
Published: May 2021

This paper discusses the basic design and operating characteristics of a precision heavy-duty thermal spray turntable. The system incorporates eccentricity and speed control and accommodates working pieces up to 100 mm in diameter and 2000 mm in height weighing as much as 1500 kg. Site tests, as reported in the paper, indicate that the turntable also meets dust and heat tolerance requirements.
Deposit Model for Offline Programming in a Spray Process
Authors: Montillet D. , Dombre E. , Valentin P.
Published: May 2021

This paper presents research work aimed at path planning for continuous processes; we treat the general case and examine thermal spraying in particular. The objective is to simulate the process for the offline programming of a sprayer robot. Integrating process models with those of the robot and workpiece in a single CAD environment simplifies the preparation and optimization of spraying tasks. This paper describes the principles and specifications of the application package with emphasis on the development of the process model and motion generation satisfying the constraints of thermal spraying.
Unusual Application of Plasma Sprayed Coating for Boiler Tubes in Oil-Fired Boilers
Authors: Tani K. , Harada Y. , Kobayashi Y.
Published: May 2021

The unusual effects of plasma sprayed coating on the fire-side of evaporator tubes located in an oil-fired steam generating boiler are discussed. The main heat transfer surfaces are constructed by heat exchanger tubes, evaporator tubes and superheaters. Maintenance to prevent of the boiler failure or the preserve heat exchanger effectiveness is a very important factor in the operation of boiler facilities. In a boiler which employs heavy gravity oil as a fuel, plasma sprayed Ni-Cr alloy has often been applied to boiler tubes for the relief of hot corrosion by combustion gas. However, the circulation of boiler water causes an internal deposit to form on the inner wall of evaporator tubes. The internal deposit generates excess heat load against the tubes. As the overheating of the tubes often causes the evaporator tubes to fail, they are chemically cleaned periodically. In this paper, the influence of Ni-Cr plasma sprayed coating for the heat flux, which dominates the formation of the internal deposit, is investigated. Ni-Cr plasma sprayed coating is substitutionally hot corrosion resistant and is a composite coating into which the fuel ash containing a vanadium or sulfur compound are interstitially penetrated and solidified. It is derived that the existence of the coating on the fire-side of the evaporator tubes normalizes the heat load in their inner walls. Moreover, the suppression of internal deposit formation decreases the frequency of chemical cleaning for tubes. The dual effects of plasma sprayed coating for hot corrosion resistance in the fire side and the suppression of internal deposit on the water side of the tubes are reported.
Internal Plasma Spray Process for Cylinder Bores in Automotive Industry
Authors: Barbezat G. , Keller S. , Wuest G.
Published: May 2021

In the Automotive Industry the need for lower manufacturing costs, the use of less strategic material, and easier, faster, and more flexible routes for manufacturing are being looked for continuously. The environmental concerns relating to the use of galvanic coatings is growing. This has led to the examination of the plasma-powder spray process for the application of coatings for surface modification. In the area of engine cylinder bore coatings a major advance is taking place in the use of a rotating plasma spray device. This paper covers the use of a plasma-powder spray process for the coating of aluminum-silicon cylinder block bores using a rotating plasma gun capable of producing coatings of reliable microstructure and integrity. Properties and microstructures of the applied coatings will be presented. Test results will be shown that the necessary bond strength of the coating can be achieved without the use of a bond coat. Surface preparation prior to coating and surface finishing methods after coating will also be discussed. Experience in Europe, Japan and the Unites States will be discussed which show that the plasma-powder spray process offers a performance proven and cost effective solution for the coating of cylinder bores, thus demonstrating the future application potential for this technology.
Component Repair and Chrome Plating Replacement with New Thermal Spray in the United States Navy: Successes and the Future
Authors: Rigney R.W. , Grubowski A. , McCaw R. , Scandell K.
Published: May 2021

High Velocity Oxy-Fuel Thermal Spray has been used by the Navy for repairing components for several years with great success. This paper will discuss some of the applications being done, the results of these applications and where the technology will be utilized on the future. The Office of Naval Research in conjunction with Naval Research Laboratory and Naval Surface Warfare Center is investigating replacements for chrome plating. One of the technologies being looked at is HVOF Thermal Spray. This paper will discuss this program, new materials being developed and new applications being done. The superior physical characteristic of HVOF has increased the utility of this technology from mechanical components to aircraft and submarine components. Acceptance of these coatings at various levels at NAVSEA will be discussed and criteria established for these acceptances will be reviewed. The role of these coatings in ship repairs as well as the implications for new construction will be discussed. Specific examples of repairs will be shown and updated reports will be provided as to their service. Locations that have services available will be detailed and future growth of this technology within the Navy will be reviewed. A quick overview of similar emerging technologies will be provided. A highlight of the presentation will be an update of the repair done with HVOF Tungsten Carbide on the Rudder Rams on the USS Saipan.
The Development and Implementation of Thermal Spray Coatings for Helicopter Components
Authors: Guillemette R.
Published: May 2021

Many components in helicopter dynamics systems depend on hard, wear resistant coatings for reliable performance. Component replacement times are currently limited by performance of these coatings in many cases. Thermal spray coatings have been evaluated for these applications to replace nickel and chromium electroplate. The effect of coatings on fatigue strength is quantified by a strain limit concept to reduce test requirements during development phase. Full scale bench testing and coupon wear testing were conducted to reveal large improvement in sliding and fretting wear resistance. A fine porosity network in thermal spray coatings, high hardness and high fatigue strength are shown to be the main contributors to improved wear performance. Thermal spray coatings also exhibited enhanced corrosion resistance in salt fog and crevice corrosion conditions. These data permitted implementation on several critical helicopter components.
Mechanical Properties of Spray-Formed Composite Structures
Authors: Brogan J.A. , Berndt C.C. , Claudon A. , Coddet C.
Published: May 2021

In this study, ethylene methacrylic acid copolymer (EMAA) was used as the matrix to produce EMAA/Al2O3 and EMAA/NiCr composite coatings from dry-blended powder mixtures. This work was conducted to determine processing concerns when using similar sized reinforcement particles of different density in a flame-spray process. This work has utility for applications that require a reduction in mechanical wear and/or to confer upon a polymeric deposit a certain functional property by the introduction of value-added powder. Free-standing coatings were produced to test the mechanical properties of the sprayed deposit. The effects of the filler content on the secant modulus, yield stress, and tensile strength are discussed. The differences in deposition efficiencies among the EMAA, Al2O3, and NiCr are highlighted with respect to particle size and density.
Oxidation, Thermo-Mechanical, and Novel Lattice-Gas Particle Deposition Modeling Aspects in Plasma Spraying of Ti-6Al-4V/SiC Fiber Composites
Authors: Cochelin E. , Borit F. , Frot G. , Jeandin M. , Decker L. , Jeulin D. , Al Taweel B. , Michaud V. , Noel P.
Published: May 2021

Plasma spraying is known to be one of the main promising processes for the manufacturing of Ti/SiC long fiber composites. However, some improvements remain to be done for this process to be applied in a routine industrial route. These include: oxygen contamination of the sprayed material through that of Ti particles before and during spraying damaging of fibers due to a high level of thermal stresses induced at the spraying stage adequate deposition of Ti-based powder to achieve a low-porosity matrix and good impregnation of the fiber array. This contribution deals with work in the 3 previously mentioned fields, which resulted in a whole 3-fold study of the process. Oxidation was studied using electron microprobe analysis of elementary particles quenched and trapped into a closed box at various given flight distances. Oxygen diffusion phenomena within the particles are discussed from a preliminary theoretical approach coupled with experimental data. Isothermal and thermo-mechanical calculations were made using ABAQUS code to determine stresses arising from contact of a liquid Ti-6Al-4V particle onto a SiC fiber. On a higher scale, i.e. that of the sprayed powder flow, a 2-dimensional original model simulating the deposition of droplets onto a substrate was developed. This model is based on a lattice-gas automaton which reproduces the hydrodynamical behavior of fluids.
Realization of Mirror Shells for X-Ray Telescope by Plasma Forming
Authors: Roussel E. , Fromentin J.P. , Freslon A.
Published: May 2021

Future X-ray space missions will require telescopes with very large effective area, good angular resolution and low weight. To obtain these characteristics it is necessary to produce very thin and light mirror shells that, once integrated into a suitable mechanical structure, will fulfil the requested specifications. To meet these requirements, one approach which seems promising is the use of ceramic materials combined with the plasma forming technology to produce ceramic carriers that are subsequently used to manufacture the x-ray mirror shells by means of the epoxy replication technology on superpolished mandrels. The CEA/Le Ripault has shown the feasibility of producing ceramic carriers (diameter: 600 mm, height: 239 mm). The mass saving is substantial in comparison with the nickel electroforming technology which is now used to manufacture high throughput, medium angular resolution x-ray optics. The achieved out of roundness of the carriers is ± 70 microns; an effort must still be made to meet the requested specification of ± 20 microns.
Near Net-Shape Forming of Thermal Barrier Coated Components for Gas Turbine Engine Applications
Authors: Kim G.E. , Tsantrizos P.G. , Grenier S. , Cavasin A. , Brzezinski T.
Published: May 2021

Many of the recent improvements in gas turbine engines have been attributed to the introduction of thermal barrier coatings (TBC) for superalloy components. There exists, however, some limitations in current fabrication methods for closed hot-section components: less than ideal coating quality, the need for welding, and limited choice of superalloy material. This paper describes a vacuum plasma near-net-shape process that overcomes these limitations. The process is used to fabricate closed components from yttria-stabilized-zirconia with a CoNiCrAlY bond coat and IN-738LC outer layer. The results from the study show that it is possible to produce near-net-shape superalloy parts with good coating properties and the absence of welds. The mold was reusable after minor reconditioning and the coatings were uniform in thickness and microstructure with a smooth surface finish. The bond coat and structural superalloy layers were very dense with no signs of oxidation at the interface. After heat treatment, the mechanical properties of the IN-738LC compare favorably to cast materials.
Thermal Spray Coatings for Fiber Reinforced Polymer Composites
Authors: Ashari A.A. , Tucker R.C.
Published: May 2021

Fiber-reinforced polymer composites are an important class of structural materials, offering high strength-to-weight ratios and high rigidities. For many applications, however, their wear resistance is less than desirable. Wear-resistant thermal spray coatings have the potential to improve the surface properties of fiber-reinforced polymer composites, although some require the application of a bond coat to achieve sufficient adhesion. The present study was conducted to find acceptable bond coat materials and compare their performance. Materials such as polyamides, polyimides, polyether-ether-ketone, or simply aluminum or nickel were found to be suitable bond coats for many composite substrates.
Preparation of Films for Solid Oxide Fuel Cells by Center-Injection Low Pressure Plasma Spraying
Authors: Chen H.C. , Heberlein J. , Yoshida T.
Published: May 2021

A new plasma spray process was developed for the rapid deposition of very dense electrolyte layers for solid oxide fuel cells (SOFCs). The dense yttria-stabilized zirconia (YSZ) film was prepared by a center-injection low pressure plasma spraying (CI-VPS) process on various substrates in a triple-torch reactor. For deposition on porous substrates, an intermediate layer was applied using conventional atmospheric plasma spraying (APS) to close the large pores in the substrate. The films were characterized by XRD, SEM, and EMPA. The porosity of the film was analyzed by computerized image analysis of the micrographs. The film was also fractured by four-point bending to characterize the nature of bonding of layer-to-layer and within the deposit. The film analysis showed that YSZ layers with porosities of 0.3 % could be obtained at very high deposition rates with the CI-VPS process, with a very good functional performance of the layer as an electrolyte. Building of a complete SOFC by successive deposition of an atmospheric pressure sprayed porous cermet film, the dense YSZ electrolyte layer, and a porous perovskite film is discussed.
Triplex – An Innovative Three-Cathode Plasma Torch
Authors: Zierhut J. , Haslbeck P. , Landes K.D. , Barbezat G. , Muller M. , Schutz M.
Published: May 2021

Dc plasma torches typically use a mixture of inert and molecular gases when spraying high melting powders. The addition of molecular gases increases the enthalpy of plasma jets, but it also produces arc root fluctuations that can cause variations in injected powders. This paper describes an innovative plasma torch system characterized by a long nozzle and three parallel cathodes. The nozzle consists of several electrically insulated rings and a ring-shaped anode. By adding more rings, the arc gap and voltage can be increased along with the enthalpy of the plasma jet. The results of various tests, comparing the spray rates and deposition efficiencies of new and conventional torches, are presented in the paper.
Effect of Spray Parameters on the Plasma in High Pressure Plasma Spraying up to 300 kPa
Authors: Sodeoka S. , Suzuki M. , Inoue T. , Ueno K.
Published: May 2021

his paper examines the influence of nozzle bore diameter and plasma gas flow on the characteristics of plasma torch spraying. Large bore size allows high plasma gas flow rates to be achieved without an excessive increase in voltage, which is apt to damage the cathode. High flow rates (Ar: 1.3x10-3, H2: 1.3x10-4, He: 2.7x10-4 m3/s) are effective in imbuing more power into the plasma without the damage associated with higher chamber pressures. The relationships among key process parameters, including effective plasma power, electrical efficiency, chamber pressure, and plasma gas flow, are expressed qualitatively in the paper based on multiple regression analysis.
Electron Beam Post-Treatment of Coatings Plasma Sprayed onto Magnesium Alloys
Authors: Wielage B. , Fleischer K.
Published: May 2021

Magnesium alloys are widely used as lightweight metals in cars and trucks, but they require special surface treatments to offset corrosion and wear limitations. One such treatment, electron beam remelting, is the focus of this present work. As described in the paper, copper and nickel powders were plasma sprayed onto magnesium in a vacuum chamber, then heated to melting temperatures with a swept electron beam. Copper and nickel were chosen because they form hard intermetallic compounds when melted with magnesium. The structure and properties of the remelted Cu- or Ni-alloyed surface layer were found to be dependent on the properties of the plasma sprayed coating and the parameters of the e-beam treatment. In the course of the investigation, the coatings were assessed based on their microstructure, the thickness of the remelting zone, occurring phases, and the determination of hardness and abrasive wear resistance.
Role of Atmosphere During Plasma Processing for Application to Plasma Spraying of Aluminum onto Polyethyleneterephtalate (PET)
Authors: Hubert H. , Blein F. , Freslon A. , Jeandin M. , Le Paven C. , Houdy P.
Published: May 2021

Polymeric substrates must be effectively cooled during plasma spraying to limit detrimental effects due to heat flow from the plasma jet. Even with the use of auxiliary cooling systems, however, some polymer substrates can undergo superficial modifications caused by particle heating at impact. This paper deals with chemical modifications in PET as a function of surrounding atmospheres during plasma processing. It also explains how aluminum coating adhesion was determined using tensile tests.
Heating and Acceleration of Ceramic Particles in 20-kA Pulsed Plasma
Authors: Miyamoto M. , Sakuta T. , Tago M.
Published: May 2021

In this paper, the authors evaluate a pulsed plasma spraying process for producing ceramic coatings. Experiments were conducted with a specially developed torch with a discharge current of 24 kA and a pulse duration of 400 μs. The in-flight characteristics of alumina particles injected into the pulsed plasma stream were measured and analyzed. The surface temperature of alumina particles reached 2,700 to 3,300 K, which is well above the melting point. Particle velocity was found to be around 200 m/s, which is comparable to particle velocity in dc plasma streams. Coatings formed with one shot of pulsed plasma were examined using scanning electron microscopy, and the results confirm the applicability of pulsed plasma to the spraying of refractory materials.
High Heat Flux Thermal Cycling of Multi-Layered Deposits Using a HVOF Gun: Modelisation and Experiments
Authors: Verdy C. , Riad H. , Raviart O. , Abboudl S. , Coddet C. , Cornu D. , De Monicault J.-M.
Published: May 2021

The aim of this work was to determine the behavior of multi-layered structures under high heat fluxes. A direct simulation by the implicit finite difference method was used to predict the transient temperature distribution in each layer of the multimaterial. The influence of the thickness of layers was also studied. Experimentally, high heat fluxes were produced using a HVOF gun operated with a methane-oxygen mixture and internally cooled samples. Multi-layered deposits were vacuum plasma sprayed onto a copper block containing coolant channels for a circulation of water. Transient and static tests were performed with heat fluxes up to 100 MW/m2 and durations of a few minutes to several hours.
Phase Composition Changes in Plasma Sprayed Zircon-Alumina Tubes
Authors: Dubsky J. , Kolman B.J. , Buchal A.
Published: May 2021

Protective tubes ( Ø 90x1500 mm) were manufactured by spraying with a water stabilized plasma gun. Mixtures of zircon (ZrSiO4) and alumina (Al2O3) were used as feedstock powders. Products made of these powders exhibit very good properties during thermal cycling. Previous results of the phase composition and phase changes were obtained from as-sprayed and annealed samples using X-ray diffractometry (XRD) and scanning electron microscopy. During plasma spraying zircon decomposed into ZrO2 and SiO2, which on impact and after rapid quenching formed a very fine eutectic mixture of tetragonal or monoclinic ZrO2 and amorphous SiO2. During this process alumina, in feedstock as α-phase (corundum), formed the spinel γ-phase. On annealing the y-phase transformed into the a-phase, whereas amorphous SiO2 crystallized and reacted with tetragonal ZrO2 to form ZrSiO4. Mullite (3Al2O3.2SiO2) was found at the highest annealing temperature of 1500°C when alumina reacted with SiO2. High temperature XRD was used for direct observation of phase changes during heating and cooling between room temperature and 1500°C in powdered as-sprayed deposits. This method confirmed the phase changes observed at room temperature in annealed samples, in particular the partial transformation of tetragonal to monoclinic ZrO2.
Stress Intensity Factors for Interfacial Cracks in Thick Thermal Barrier Coatings
Authors: Bjerken C. , Persson C.
Published: May 2021

A straight-forward method for calculating the stress intensity factors (or the energy release rate and mode mixity) for interfacial cracks in bi-materials has been developed. An existing method for homogeneous materials, based on the computation of the energy release rate from the nodal forces and displacements given by a finite element analysis, was modified to include the mismatch in material properties. Thick thermal barrier coatings usually fail as a result of cracking near the interface. The influence of the thickness and the edge angle of the coating on the energy release rate and mode mixity for a small edge crack at the interface of a TBC system subjected to thermal loading was investigated. It was established that the high energy release rates obtained for thick coatings can be reduced by decreasing the edge angle of the coating. Additionally a comparison with energy release rates given by J-integral computations has been done.
Analisis Peraturan Pemerintah Nomor 101 Tahun 2014 Terhadap Bahan Berbahaya Dan Beracun di Kota Batam
Authors: Ukas Ukas , Arman Zuhdi
Published: May 2021

Lingkungan merupakan hal yang sangat penting dalam siklus kehidupan manusia. Di zaman moderen ini timbul permasalah mengenai lingkungan. Dalam tulisan ini permasalahan yang diangkat adalah dampak pencemaran lingkungan yang disebabkan oleh limbah dan sampah serta upaya pemerintah dalam mencegah pencemaran lingkungan hidup. Permasalahan tersebut terjadi seiring dengan perkembangan teknologi yang tanpa memperhatikan lingkungan. Pencemaran lingkungan memiliki dampak terhadap kesehatan, estetika, kerugian ekonomi, dan terganggunya ekosistem alami. Metoda yang digunakan dalam karya tulis ini adalah yuridis-empiris, dengan menggunakan teori pendekatan fakta dan peraturan perundang-undangan. Kesimpulan dari permasalahan tersebut adalah dengan tidak adanya kesadaran dari pihak pengusaha industri dan masyarakat untuk melindungi lingkungan hidup dari pencemaran limbah dan sampah akan berdampaknya pada rusaknya ekosistem alami serta berkurangnya baku mutu lingkungan.
Analisis Pembebasan Pemenuhan Prestasi Akibat Adanya Overmacht Karena Corona Virus Disease 2019 (Covid-19) Di Indonesia
Authors: Dewi Rachma Ayu Kusuma , Pantjo'u Amelia Bellatrix , Chandra Widya Dika , Sa'baniah Sa'baniah
Published: May 2021

Corona Virus Disease 2019 atau yang biasa disebut sebagai Covid-19 merupakan wabah penyakit yang menyerang hampir seluruh dunia, termasuk Indonesia. Covid-19 telah menimbulkan banyak dampak sosial dan ekonomi, dimana salah satunya adalah terkait dengan pemenuhan prestasi yang timbul dari suatu kontrak. Tentunya Covid-19 ini merupakan peristiwa yang tidak diduga-duga sebelumnya, sehingga menghambat pemenuhan prestasi dalam kontrak. Hal ini kemudian, membuat pihak yang tidak dapat memenuhi prestasi tersebut mendalilkan Covid-19 sebagai overmacht agar bebas dari pemenuhan prestasi tersebut Berdasarkan latar belakang tersebut, maka penelitian ini bertujuan untuk mengetahui 1) Apakah Covid-19 dapat digunakan sebagai alasan overmacht, dan 2) Apakah akibat hukum Covid-19 sebagai overmacht? Penelitian ini adalah penelitian hukum dengan menggunakan pendekatan peraturan perundang-undangan (statute approach) dan pendekatan konseptual (conceptual approach). Berdasarkan penelitian ini, ditemukan bahwa Covid 19 merupakan overmacht karena memenuhi syarat suatu peristiwa dapat dikatakan sebagai overmacht dan ditegaskan secara expressis verbis di dalam beberapa peraturan perundang-undangan, seperti UU 24/2007, Perpu 1/2020, dan KEPKABNPB 13.A/2020. Akibat hukum yang timbul dari Covid-19 merupakan overmacht adalah 1) kreditur tidak dapat meminta pemenuhan atas prestasi, 2) debitur tidak dapat dinyatakan lalai, sehingga tidak perlu membayar ganti rugi, dan 3) kreditur tidak dapat meminta pemutusan perjanjian.
Anterior sacral meningocele repair assisted by intraoperative intrathecal fluorescence and 3D printing model: illustrative case
Authors: Yeh Yu-Chaing , Lin Ya-Jui , Yeh Chih-Hua , Hsieh Pao-Shiu , Wu Chieh-Tsai
Published: May 2021

BACKGROUND

Marfan syndrome is rarely accompanied by anterior sacral meningocele (ASM) resulting from erosion of the sacrum by dural ectasia. ASM may induce symptoms due to severe mass effects. ASM may also mimic ovarian cysts, and the risk of cerebrospinal fluid (CSF) leakage is high if spontaneous rupture of the cyst occurs. In this study, the authors presented a rare case of ASM with iatrogenic CSF leakage in a 34-year-old woman with suspected Marfan syndrome.

OBSERVATIONS

The patient initially presented with a giant ASM that was first misdiagnosed as an ovarian cyst. Previously, it had been partially resected, which was followed by iatrogenic CSF leakage. Symptoms of intracranial hypotension, including postural headache and dizziness, developed within 1 month. Brain magnetic resonance imaging (MRI) showed pituitary enlargement, bilateral subdural effusion, and tonsillar herniation. Preoperative computed tomography myelography provided three-dimensional (3D) examination of the deformed sacrum and CSF leakage site. Transabdominal approaches led to primary repair, and repair of the meningocele was achieved by intraoperative fluorescein fluorescence and 3D printed model–guided polymethyl methacrylate bone cement reconstruction. No CSF leakage or recurrent ASM was found at the 1.5-year follow-up visit.

LESSONS

Intraoperative intrathecal fluorescence and 3D-printed models are useful for ASM repair. Preoperative MRI is helpful for differentiating ASM from other causes of a huge pelvic mass, including ovarian cyst.
A retro-odontoid pseudotumor treated with fixation and tumor resection by the lateral approach: illustrative case
Authors: Oda Yoshiaki , Tokioka Takamitsu , Ozaki Toshifumi
Published: May 2021

BACKGROUND

A retro-odontoid pseudotumor is not a condition that requires resection. However, pathological diagnosis is required when a tumor such as a meningeal tumor or chordoma is suspected. The authors report a case of a large lesion treated with posterior fixation and tumor resection using a lateral approach.

OBSERVATIONS

A 77-year-old man visited the authors’ department complaining of neck pain and decreased dexterity of the upper extremities. Magnetic resonance imaging showed a large, beak-shaped lesion behind the dens and severe compression of the spinal cord. Surgery consisted of occipitocervical–C2 fixation, followed by tumor resection with a left lateral approach. The pathological diagnosis was consistent with a retro-odontoid pseudotumor. The tumor was resected to a relatively large extent and shrank over time, leading to complete disappearance.

LESSONS

Pathological examination is also possible with a posterior approach if the tumor can be reached through the lateral edge of the dura. In that situation, the amount of resection is limited, and there is a risk of spinal cord compression. Intradural dissemination of tumors is a concern with the transdural approach. If tumor resection by the posterior approach is difficult, the lateral approach can facilitate tumor resection.
Spinal arthrodesis via lumbar interbody fusion without direct decompression as a treatment for recurrent radicular pain due to epidural fibrosis: patient series
Authors: Swong Kevin , Strong Michael J. , Nathan Jay K. , Yee Timothy J. , Smith Brandon W. , Park Paul , Oppenlander Mark E.
Published: May 2021

BACKGROUND

Lumbar radiculopathy is the most common indication for lumbar discectomy, but residual postoperative radicular symptoms are common. Postoperative lumbar radiculopathy secondary to scar formation is notoriously difficult to manage, with the mainstay of treatment focused on nonoperative techniques. Surgical intervention for epidural fibrosis has shown unacceptably high complication rates and poor success rates.

OBSERVATIONS

Three patients underwent spinal arthrodesis without direct decompression for recurrent radiculopathy due to epidural fibrosis. Each patient previously underwent lumbar discectomy but subsequently developed recurrent radiculopathy. Imaging revealed no recurrent disc herniation, although it demonstrated extensive epidural fibrosis and scar in the region of the nerve root at the previous surgical site. Dynamic radiographs showed no instability. Two patients underwent lateral lumbar interbody fusion, and one patient underwent anterior lumbosacral interbody fusion. Each patient experienced resolution of radicular symptoms by the 1-year follow-up. Average EQ visual analog scale scores improved from 65 preoperatively to 78 postoperatively.

LESSONS

Spinal arthrodesis via lumbar interbody fusion, without direct decompression, may relieve pain in patients with recurrent radiculopathy due to epidural fibrosis, even in the absence of gross spinal instability.
Local language programs in cultural radios to maintain Indonesian national identity
Authors: Wahyuningtyas Dwi , Kusuma Ade , Febrianita Roziana , Achmad Zainal Abidin
Published: May 2021

Private radio, which relies on programs with local cultural content in local languages, affects the success of reaching large audiences and financial benefits. In East Java, four private radios have the advantage of local cultural programs, namely Radio Jodhipati FM in Nganjuk, Radio Sritanjung FM in Banyuwangi, Radio Nada FM Sumenep, and Radio Media FM in Surabaya. This study aims to determine what cultural programs can increase the number of listeners and profitability on the four cultural radios. Furthermore, to find out why listeners like local cultural programs of each radio. This research on broadcast content on four cultural radios uses virtual ethnographic methods by collecting data, both offline and online. Researchers are involved in broadcasting activities on four cultural radios (offline) and listener interaction activities in the virtual world (online), namely Facebook and WhatsApp. This study conducted interviews with twelve informants representing radio management, local cultural figures, and loyal listeners. The results showed that each radio has excellent cultural programs with a solid appeal to maintain listener loyalty. The four cultural radios involve cultural experts in designing cultural programs. Listeners try to maintain local tastes because they realize that love for local culture is a strengthening of national identity, which is the richness of Indonesian culture.