bluuebunny/crossref_metadata_2025 huggingface dataset:
La avenida Alfonso Ugarte, otra vez muralla de Lima
Authors: Córdova Adolfo
Published: May 2021

El espacio que ocupa la avenida Alfonso Ugarte tiene vocación (¿o maldición?) de muralla. Durante decenas de años virreinales, hecha de hiladas de piedra asentadas con mortero de cal y arena (proporción 1:3), coronada por almenas, tuvo en tiempos republicanos casi un siglo de pretensiones parisinas, para retornar recientemente a su anterior misión de muralla, edificada esta vez con tramos de mala arquitectura metálica y largas hiladas de maloliente CO2 (anhídrido carbónico), asentadas con ruidos de claxon, motores y de silbatos policiacos (proporción 3:1).
On the Microstructures of Thermally Sprayed “Peek” Polymer
Authors: Liao H. , Beche E. , Coddet C. , Berger F.
Published: May 2021

Polymer coatings find increasing interest for anticorrosion applications and others. Thanks to its extraordinary properties (high chemical stability, low creep rate and good electrical resistivity at relatively high temperature) PEEK (Polyetheretherketone) polymer is now considered as a challenging matierial. In this work, PEEK polymer powder was thermally sprayed with different processes. Particle impacts were observed and coating was analyzed by infrared spectrometry. The temperature of the substrate was shown to play an important role in the formation of dense and continuous coatings. Thermal degradation during spraying produces new carbonyl species due to chain scissions; but the amount of decomposition could be controlled from the choice of spraying conditions.
Plasma Sprayed Self-Lubricating Cr2O3-CaF2 Coatings: Friction and Wear Properties
Authors: Vos F. , Delaey L. , De Bonte M. , Froyen L.
Published: May 2021

An alternative production route to obtain thermally sprayed self-lubricating ceramic coatings is proposed and microstructural, friction and wear properties of these coatings are discussed. A preliminary powder treatment shows to induce a higher degree of homogeneity compared to conventionally deposited composite coatings, offering some perspectives for a further improvement of the lubricating and wear properties. This approach is illustrated using CaF2 as a solid lubricant dispersed in a Cr2O3 matrix, where the high melting point of the latter (Tm{Cr2O3} = 2460°C) necessitates plasma spraying as deposition technique. The microstructure of the coatings is evaluated by a metallographic study of sections perpendicular and parallel to the substrate surface. Wear and friction behaviour is evaluated using reciprocating wear test Wear tracks are analysed by means of laser profilometry. The results are discussed in relation to test and production parameters. Test temperature as well as solid lubricant concentration predominantly affects the wear and friction properties. Using a surface temperature of 400°C, a friction coefficient of 0.25 and a wear volume of 37 x 103 µm3 after 10,000 cycles are obtained for a coating containing 16 vol.% of CaF2.
Wet Abrasion and Slurry Erosion Resistance of Sealed Oxide Coatings
Authors: Knuuttila J. , Ahmaniemi S. , Leivo E. , Sorsa P. , Vuoristo P. , Mantyla T.
Published: May 2021

Several recently published studies have shown remarkable improvements in dry abrasion resistance and corrosion resistance of aluminum phosphate sealed oxide coatings when compared to unsealed ones. There are numerous applications in chemical industry where a corrosive environment is accompanied with abrasive or erosive particles. In this study the wet abrasion resistance and slurry erosion resistance of aluminum phosphate-sealed and unsealed oxide coatings were studied and compared to their dry abrasion resistance. In wet abrasion tests kaolin and water mixture was used as the abrasive. In slurry erosion tests several abrasives in water with various pH values was used as the erosive medium. The coatings were characterized for microstructure and their wear mechanisms were analyzed using SEM. The results from wear tests are reported and correlated with coating properties. The influence of coating quality to the relative improvement achieved by sealing is presented and discussed.
Elevated Temperature Erosion Resistance of Several Experimental Amorphous Thermal Spray Coatings
Authors: Wang B.
Published: May 2021

The elevated temperature erosion resistance of experimental amorphous thermal spray coatings was determined in a laboratory elevated temperature erosion tester. Test conditions attempted to simulate the erosion conditions found at the combustor waterwall tubes in fossil fuel fired boilers. Erosion tests were conducted on four experimental amorphous thermal spray coatings, using the bed ash retrieved from an operating coal fired boiler. An experimental arcspray process was used to spray coatings. These results were compared with erosion test results of two common structural materials, two commercially available arc-sprayed coatings, and a proprietary HVOF coating. Test results indicated that the Duocor coating had the highest erosion resistance among the four experimental coatings, it showed equal resistance to the HVOF coating (DS-200). Compared to AISI 1018 steel, both Duocor and DS-200 coatings reduced material wastage by 26-fold. Other test results indicated that the XJ-16, 60T and Armacor M coatings had equal erosion resistance reducing material wastage approximately 7-fold, while Armacor CW reduced by 10-fold. Only slightly better than the unprotected 1018 steel, the X-20 coating performed poorly on erosion tests. The high erosion resistance of Duocor and DS-200 coatings was attributed to their high densities and fine splat structures.
A Study on the Wear Characteristics of Plasma Sprayed NiCrSiB/WC-12Co Mixed Coating
Authors: Ahn H.S. , Lee C.H.
Published: May 2021

Air plasma spray coatings of three different WC-12%Co powders based on the powder manufacturing methods were conducted. S&F (Sintered and Crushed) WC-12%Co and NiCrSiB mixed powder with different ratio were also sprayed. The best wear resistance of S&F WC-12%Co coating was mainly due to its high hardness related with large amount of homogeneously and uniformly distributed retained carbides. The wear resistance of blend coatings increased with increasing WC-12%Co weight percent which was associated with the fact that the wear resistance of all coatings increased with increasing hardness and decreasing friction coefficient. But the exact relation of wear resistance with cohesive bond strength could not be found. The dominant wear mechanisms of WC-12%Co coatings were adhesive wear, tribo-film formation by material transfer, fatigue crack, particle (splat) fracture and delamination (spallation of coating layers). In the case of blend coatings, when the weight percent of WC-12%Co was small plastic deformation and abrasive mark (or scratching) by asperity and/or hard particle were observed. with increased weight percent of WC-12%Co the wear mechanism was closer to that of WC-12%Co coatings where no plastic deformation and abrasive mark was observed.
Effect of Powder Type and Composition on the Erosion and Abrasion of HP/HVOF Deposited WC-Co Coatings
Authors: De Villiers Lovelock H.L. , Van Wyk P.
Published: May 2021

WC-Co and WC-CoCr coatings were deposited with the JP-5000 liquid fuel HP/HVOF system using various thermal spray powder types. The microstructure, microhardness, deposition rate and wear resistance of the coatings were characterized. The results show that these coatings provide significantly more protection from dry three-body abrasion than from dry sand erosion, when compared to mild steel. They also provide more advantage at low angles of erosion than at high angles of erosion. Furthermore, the coating composition was found to have a significant effect on the wear rates, with WC-CoCr providing the best wear resistance even after taking the higher cost of the powder into account. The powder manufacturing route had only a secondary effect on the wear rates, except in the case of fused and crushed powder, which produced an inferior coating.
Friction and Corrosion Behavior of Different Ceramic Coatings (Oxides) Obtained by Thermal Spray for Qualification Tests in Sea Water
Authors: Giroud A. , Jouanny C. , Heuze J.L. , Gaillard F. , Guiraldenq P.
Published: May 2021

Different oxides layers have been studied by friction in natural sea water medium under the same conditions (Cr2O3, Al2O3, Al2O3 + Cr2O3). The evolution of different parameters have been analyzed: friction coefficient, electrochemical potential, degradation of the layers in the contact, impedance spectroscopy. The main result observed is concerned by the cracking of the coatings under stresses, in such a way interconnection paths are rapidly present between the substrate and the sea water medium through the layers. The coating impregnation process by epoxy, before the tribocorrosion tests, improve the protection of the substrate against the corrosion.
The Tribology of Amorphous Surfaces Formed by Wear of Thermal Spray Coatings
Authors: Scruggs D.M.
Published: May 2021

This paper describes the wear induced transformation of crystalline metal surfaces into amorphous and/or microcrystalline surfaces that exhibit gross changes in the fundamental properties of friction, wear, hardness and toughness. The coatings are applied using wire and powder feed to TWAS and HVOF equipment. Wear processes investigated include adhesive wear, low stress abrasion, grinding wear and galling. The effects of chemical makeup of the surfaces and the alloy structure are examined using microscopy and x-ray diffraction. The surface & underlying coating characteristics including roughness, microstructure, hardness and friction coefficient are determined. Results show that the surface structure is dependent on the wear vector. The structural transformation is a function of the chemical makeup and intrinsic wear resistance of the crystalline alloy coupled with the energy input of the wear process. High energy wear such as grinding wear can overcome the transformation. The results also suggest that the micro-welding that occurs between asperities in crystalline alloys is replaced by a flow process on the transformed surface. Coating structure, glass transition temperature, crystallization temperature and critical cooling rate of the transformed surface are much more significant than the chemistry of the alloy once the transformation takes place.
Wear Mechanisms of MCrAlY Abradable Plasma-Sprayed Coatings
Authors: Li S. , Langlade-Bomba C. , Treheux D. , Crabos F. , Monge-Cadet P.
Published: May 2021

Reducing operating clearance between the HP turbine and shroud is a means often used by engine manufacturers to improve the efficiency of new generation gas turbines. This, in turn, requires the development and use of clearance control coatings to minimize the effects of degradation and wear associated with rubbing. In this study, the authors assess two coating systems: VPS NiCoCrAlYTa coatings for blade tips and plasma-sprayed MCrAlY, a potential abradable coating. In order to understand the wear mechanisms of these systems, block-on-ring and fretting tests were conducted and the relationship between microstructure and wear was examined. The results were then compared to those of rub tests performed with real engine components.
Plasma Spray Jets and Plasma-Particulate Interaction: Modeling and Experiments
Authors: Pfender E. , Chang C.H.
Published: May 2021

The first part of this overview on plasma spraying covers the general behavior of plasma jets generated by d.c. and r.f. plasma torches, including the fluid dynamics of such jets. In the second part, interactions of injected powders with the plasma are considered with emphasis on those processes which dominate heat and momentum transfer from the plasma to the powder particles. Both experimental studies as well as modeling efforts are included in this overview.
PTA Reclamation of Cast Iron and Aluminum Alloys Substrate with NiCu Film Deposited by Tape Casting
Authors: Leylavergne M. , Grimaud A. , Fauchais P. , Chartier T. , Baumard J.F.
Published: May 2021

Plasma transferred arc (PTA) is now currently used for reclamation of worn materials or to provide wear or corrosion resistant coatings welded to the base material. However, the powder injection in the molten pool created at the coated part surface is a critical parameter. In order to avoid coating reproducibility problems induced by the powder feed rate, the way to coat substrate surface with powder before the PTA treatment has been studied. As the powder cannot simply be deposited onto the substrate because of the plasma flow which would blow it off before melting it, tape casting process was used to obtain an adherent powder layer on the material surface. In this paper, tape casting of NiCu particles is described and the different organic additives used to obtain a homogeneous nickel copper film on cast iron and AG3 aluminum alloys are presented. The first results of the treatment of these films by PTA reclamation are then shown.
The Influence of Powder Particle Velocity and Temperature on the Properties of Cr3C2-25NiCr Coating Obtained by Detonation-Gun
Authors: Srinivasa Rao D. , Sen D. , Somaraju K.R.C. , Ravi Kumar S. , Ravi N. , Sundararajan G.
Published: May 2021

The detonation gun (D-Gun) coating technology which results in coatings with outstanding properties has found extensive applications especially in the aerospace and engineering industry. Though the D-Gun process has been in use for the last 30 years or so, the basic mechanisms which lead to such an outstanding combinations of properties is not yet fully understood. This has been primarily due to the fact that the coating property ultimately depends on the combination of powder particle temperature and velocity at the time of its impact on the substrate to be coated and so far measurement of these parameters has not been possible. As a result, indirect correlations between D-Gun variables like fuel gas to oxygen ratio, powder feed rate, firing frequency and working distance and coating properties have been developed but without the knowledge base of how these D-Gun variables affect the powder particle temperature and velocity. An in-flight particle diagnostic sensing system has been recently installed in our laboratory and this system allows for the simultaneous measurement of particle velocity and temperature. In view of the above, a major programme has been launched to study the effect of particle velocity and temperature on the coating properties (like coating hardness, porosity, bond strength, XRD etc.) for a wide range of coatings. The preliminary results from the above investigation, pertaining to Cr3C2-25NiCr coatings obtained using D-Gun, will be presented and discussed in this paper.
Nucleation and Phase Selection in Plasma-Sprayed Alumina: Modeling and Experiment
Authors: Robert C. , Denoirjean A. , Vardelle A. , Wang G.-X. , Sampath S.
Published: May 2021

This paper presents a one-dimensional heat transfer model which predicts the solidification and cooling of a plasma-sprayed alumina splat after the flattening process is completed. A heterogeneous nucleation process taking place on the substrate surface was assumed. The density and average size of the formed nuclei were determined from the integration of the nucleation rate calculated from the classical kinetic theory for nucleation. This rate depends on the activation energy required for nucleation which takes into account the effect of the surface via a wetting angle between the growing nucleus and the catalytic surface. This contact angle was estimated from the comparison of the computed grain density with the density observed on splat surface using an atomic force microscope. When 67% of the splat surface in contact with the substrate are covered by grains, a planar solidification front was assumed to move through the melt. The theoretical model accounted also for the selection of the crystalline phase. Calculations were performed for various substrate materials at different initial temperatures. Results are expressed in terms of nucleation temperature, nucleation rate, density and grain size distribution.
Effects of Gun Nozzle Geometry on High Velocity Oxygen-Fuel (HVOF) Thermal Spraying Process
Authors: Sakaki K. , Shimizu Y. , Gouda Y. , Devasenapathi A.
Published: May 2021

Effect of nozzle geometry (such as throat diameter of a barrel nozzle, exit diameter and exit divergence angle of a divergent nozzle) on HVOF thermal spraying process (thermodynamical behavior of combustion gas and spray particles) was investigated by numerical simulation and experiments with Jet Kote II system. The process changes inside the nozzle as obtained by numerical simulation studies were related to the coating properties. A NiCrAlY alloy powder was used for the experimental studies. While the throat diameter of the barrel nozzle was found to have only a slight effect on the microstructure, hardness, oxygen content and deposition efficiency of the coatings, the change in divergent section length (rather than exit diameter and exit divergence angle) had a significant effect. With increase in divergent section length of the nozzle, the amount of oxide content of the NiCrAlY coatings decreased and the deposition efficiency increased significantly. Also, with increase in the exit diameter of the divergent nozzle, the gas temperature and the degree of melting of the particle decreased. On the other hand the calculated particle velocity showed a slight increase while the gas velocity increased significantly.
Mathematical and Computer Modeling of Particles Interaction with Plasma Jet in Low Pressure Condition
Authors: Ilyuschenko A. , Okovity V. , Kundas S. , Gurevich V.
Published: May 2021

On the base of gases molecular and kinetic theory a mathematical model of interaction between powder particles and plasma jet is developed. Three-dimensional description of plasma forming gas density distribution as well as particle motion in the plasma jet are a characteristic property of the model. A software for practical realization of the mathematical model is created. Said software provides the possibility to investigate an effect of low-pressure plasma spraying parameters on particle velocity and coordinates in the plasma jet. Computer simulation of particle velocity for powders from aluminium and tungsten oxides in argon plasma under 60 Mbar is conducted. A "Plasma-Technik" VPS unit is used for testing the developed model. Particle velocity measurement is made by a specially developed optical-electronic unit.
Characteristics of Residual Stress Produced by MoSi2 Plasma Spraying and Its Production Mechanism
Authors: Kim Y.C. , Chang K.H. , Horikawa K.
Published: May 2021

MoSi2 powder was deposited by low pressure plasma spraying on the specimen with 50%Ni-50%Cr based coat after blasted SS400 substrate. Compressive stress was generated in MoSi2 spray deposit. Tensile stress was generated in 50%Ni-50%Cr spray deposit. Large compressive stress was generated in SS400 substrate adjacent to the interface. Investigating the production mechanism of residual stress and the validity of provided residual stress, a series of the experiments were done. Blasting on the substrate, residual stress near the surface of the substrate was compressive and that of the inner part of the substrate was tensile. After the blast treatment on SS400 substrate, depositing on the substrate with 50%Ni50% Cr, residual stress of the spray deposit was tensile. This is because SS400 substrate restricts the contraction of 50%Ni-50%Cr spray deposit which has large thermal shrinkage. Depositing MoSi2 after the blast treatment, compressive stress was generated in the spray deposit. This is because the linear expansion thermal coefficient of MoSi2 is extremely small comparing with that of SS400 substrate nevertheless the temperature of the spray deposit is higher than that of the substrate. As the result, the spray deposit restricts thermal shrinkage of the substrate. The validity of estimated residual stress was shown.
Evaluation of Residual Stresses and Fatigue Life of Tungsten Carbide Thermal Spray Coated Aircraft Landing Gear Materials
Authors: Mcgrann R.T.R. , Shadley J.R. , Rybicki E.F. , Bodger B.E. , Emery W.A. , Somerville D.A. , Greying D.J.
Published: May 2021

Tungsten carbide thermal spray coatings have been used for more than twenty years in the commercial aircraft industry in applications such as turbine blade and flap-track wear surfaces. Additionally, the evaluation of tungsten carbide (WC) coatings to replace chrome plating in other aircraft applications has been underway for several years. For example, WC coatings applied by the high velocity, oxy-fuel (HVOF) process are being evaluated for use on aircraft landing gear parts. One factor that affects the suitability of WC coatings is the fatigue life of the coated part. This study compares the fatigue life of electrodeposited chrome plated specimens to the fatigue life of WC HVOF-sprayed specimens on aircraft landing gear alloys. Fatigue tests were run on cantilever flat beam specimens coated on one side and subjected to bending fatigue loads. Residual stress levels for the coatings were determined using the Modified Layer Removal Method on rectangular residual stress specimens processed with the flat beam specimens. Also, the Young's modulus and Poisson's ratio of the coating were determined using the Cantilever Beam Bending Method performed on beam specimens that were processed with the fatigue specimens and the residual stress specimens. Results indicate that certain levels of residual stress in the coating can enhance the fatigue life of the parts. The fatigue lives in bending tests of several WC coated specimens are compared with the fatigue life of chrome plated specimens.
Surface Morphology of Plasma Sprayed Ceramic Coatings
Authors: Oki S. , Gohda S. , Yamakawa M.
Published: May 2021

A novel method for characterization of microstructure of coatings is presented. Properties of plasma spray coatings are affected by their microstructure, which depends on the spraying conditions. Therefore, a detailed knowledge of microstructure is very important in order to know the coating formation mechanism and the properties of the coatings. There are many studies to characterize the microstructure of coatings. In most of those studies, the microstructures are characterized from the polished cross-section of the coatings, and the results strongly depend on the preparation methods. In this study, a new method for the characterization of coating microstructures by means of surface morphology is proposed. The distribution of shape and dimensions of splats were examined using quantitative analysis of scanning electron microscope images from the surface of the coatings. The results indicate that the surface morphology strongly depends on the spraying conditions. Keywords: characterization, coating property, splat morphology, equivalent diameter, shape factor
Characterization of Graded Ti Silicide Coating Formed by Thermal Diffusion Treatment of Low Pressure Plasma Sprayed Silicon Coating
Authors: Ohmori A. , Zhou Z. , Li C.J.
Published: May 2021

The silicon coating was sprayed on titanium substrate by low pressure plasma spraying and the subsequent coating was heat-treated in vacuum. It is found that a titanium silicide coating with the composition changed gradually can be formed through thermal diffusion treatment of silicon coating sprayed by low pressure plasma on titanium substrate. The formed silicide coatings are characterized by optical microscopy, scanning electron microscopy, EPMA analysis and X-ray diffraction (XRD). The forming process of the silicide coating is investigated by examining the relationship between silicide coating thickness and thermal diffusion parameters. The results show that the composition of silicide coating changes gradually from TiSi, at the silicon coating side through TiSi and Ti5Si4, to Ti5Si4, near substrate side. The thickness of such graded silicide coating is determined by temperature and holding time during heat-treatment. The diffusion of silicon into titanium substrate is mainly responsible for the formation of silicide. Moreover, the investigation of oxidation behavior of silicide coating shows that the formation of silicide coating on the titanium substrate can improve the oxidation resistance of titanium.
Microstructure Development During Plasma Spraying of Molybdenum Part 1: Splat Solidification
Authors: Robert C. , Vardelle A. , Wang G.-X. , Jiang X.Y. , Sampath S.
Published: May 2021

Within the framework of a scientific collaboration between the University of Limoges, France and the State University of New York, Stony Brook, USA, a joint work has been conducted on microstructure development and properties of plasma-sprayed molybdenum coatings. This first part of the work is devoted to the study of the effect of substrate nature and temperature on splat cooling, solidification and crystalline structure. They were investigated by means of a heat transfer model in the splat and the substrate, and the observation of splats by a scanning electron microscope and an atomic force microscope. The model takes into account melt undercooling, nucleation and crystal growth, as also a possible melting and re-solidification of the substrate. It has the capability to predict the grain size distribution under assumptions that the quality of contact between the splat and the underlying layer is uniform, nucleation takes place only on the substrate surface, crystal grains grow perpendicular to the substrate surface and no grain coalescence occurs during crystal growth.
Influence of Plasma Gas (Spral 22, Ar/H2) and Impurities (O2, H2O) on the Electrode Lifetime During Spraying
Authors: Gourlaouen V. , Remy F. , Leger J.M. , Sattonnet J.
Published: May 2021

Electrodes play an important role in the plasma-spraying process and must be frequently replaced to ensure good coating properties. The purpose of this work was to assess the effect of different plasma gases and oxygen and humidity levels on electrode lifetime. The change in arc voltage over time was recorded during spraying, and the elapsed time for a 5V drop was taken as the electrode lifetime. It was found that variations in oxygen and humidity in Ar-H2 gas mixtures have a major effect on lifetime and that the use of SPRAL22 gas could extend electrode life by a factor of three to four. These and other results are discussed in the paper.
Non-Contact Coating Thickness Measurement
Authors: Chandler P.E. , Quigley M.B.C. , Fletcher J.F.
Published: May 2021

There are many instances of coatings that require a nondestructive and non-contact measure of coating thickness as part of a quality control system. Specifically, this paper reports on experiments carried out on non-contact measurements of MCrAlY and TBC coatings. The system uses an infrared beam from a solid state laser to generate a thermal wave in the coating. When this wave reaches the substrate an interference effect is caused. The modulated input heating produces a modulated output infrared signal from the surface and at a different wavelength from the laser beam. The output signal has a phase difference from the input signal which is related to the coating thickness. As neither the laser nor the detector are in contact with the surface of the coating and the temperature of the coating is raised by only a few degrees this represents a non-contact NDE system. This system has been tested across a range of coating/substrate combinations. In this paper we give examples of MCrAlY and TBC coatings applied to engine components demonstrating that the accuracy of measurement is only limited by the roughness of the coating structure and substrate. The use of this system for on-line measurement during the spraying process is also discussed and results presented.
Thermo-Mechanical Characterizations of Plasma-Sprayed MCrAlY Coatings for HP Turbines
Authors: Boudot A. , Crabos F. , Monge-Cadet P. , Monceau D. , Pieraggi B.
Published: May 2021

Two different coatings were studied in this work : vacuum plasma-sprayed NiCoCrAlYTa and electrodeposited NiCoCrAlYTa. These coatings were deposited on AM3 single crystal alloy. The tensile and creep properties of coated single crystal test specimens were investigated. Ductile-brittle transition temperatures (DBBTs) were determined from tensile tests. Creep tests were performed on cylindrical specimens and on thin flat specimens. All the coatings were examined before and after testing. The two tested coatings induce a ductile/brittle transition. Strain rate has a great influence on the transition temperature. The comparison between the two processes of deposition illustrates the strong influence of coating microstructure. A marked decrease in creep properties was observed for thin single crystal specimens but contrary to cylindrical specimens, the coating has a quite positive influence, so that the creep life of coated thin specimens is increased.
A New Aluminium Silicon-Boron Nitride Abradable for Compressor Components
Authors: Boddenberg K. , Kock B. , Dorfman M. , Russo L. , Nestler M.
Published: May 2021

Air separation plants employ centrifugal compressors where air and electrical energy are the only raw materials used in the production process. In order to optimize compressor performance and efficiency, abradable coatings, originally developed for gas turbines, have been designed into turbocompressors. This paper describes the optimization and performance improvements achievable using aluminium silicon-boron nitride materials.
HVOF-Spraying vs. Hard Chrome Plating – Coating Characteristics and Aircraft Applications
Authors: Nestler M.C. , Prenzel G. , Seitz T.
Published: May 2021

High-velocity oxyfuel (HVOF) spraying is a viable alternative for hard chrome plating because of its excellent coating properties and substantially lower environmental pollution. Initial applications in ball valves, journals, and hydraulic cylinders on earthmoving equipment have proven successful. This paper discusses the advantages and disadvantages of HVOF spraying as an alternative to hard chrome plating for aircraft components and presents some of the early results of laboratory and in-service testing.
Influences of Metal Sprayed Coating Artificial Dental Root on the Vital Tissue
Authors: Magome M. , Hara K. , Sano K. , Ueda Y.
Published: May 2021

Artificial dental root materials are of great interest to medical researchers. In this study, two aluminum coating methods are investigated, atmospheric plasma and flame spraying, along with the affinity, stability, and connectivity of aluminum-based toxins. Acute toxic tests performed in vivo and in vitro show that aluminum sprayed coatings are a viable dental root material.
Nitriding of Metal Droplets in Synthesis of Intermetallic Matrix Composite Coatings by Reactive RF Plasma Spraying
Authors: Tsunekawa Y. , Hiromura M. , Okumiya M.
Published: May 2021

This paper presents a novel process that uses RF plasma spraying and premixed elemental powders to produce intermetallic matrix composites in situ without having to add reinforcement fibers or particles. Splats were collected on a stainless steel substrate and were analyzed to determine if nitrides had formed in metal droplets during flight and how it affected splat morphology. The typical splat morphology of impinged Ti droplets is disk-type with an outer peripheral fringe. Aluminum splats, on the other hand, are classified into two categories: a disk-type with an irregular outer periphery and a semi-massive-type. Other composites produced and examined include TiAl, AlN, and Ti2AlN.
Investigations on Thermal Spraying of Silicon Nitride-Based Powders
Authors: Berger L.-M. , Herrmann M. , Nebelung M. , Thiele S. , Heimann R.B. , Schnick T. , Wielage B. , Vuoristo P.
Published: May 2021

Oxide-bonded silicon nitride (OBSN) powders have been developed to address thermal spray problems associated with high temperatures. This paper examines how such powders perform when applied via detonation gun (DGS) and atmospheric plasma spraying (APS) with axial powder injection. All coatings were characterized using optical microscopy and X-ray diffraction with additional tests being performed on DGS coatings. For the first time, relatively dense Si3N4-rich coatings with an oxide binder phase were produced, and some of the DGS coatings were found to be sufficiently wear resistance for industrial use.
On The Fabrication and Properties of a Ceramic Cladded Aluminium Powder Using the Spray Drying Process
Authors: Comas B. , Mateus C. , Hansz B. , Coddet C.
Published: May 2021

A new family of spherical powders produced by the spray drying route has been developed. This paper describes as an example the manufacturing method of an Y2O3-coated aluminum powder. Atmospheric Plasma Spraying (APS) was used to test the corresponding coatings. Morphology and phases of powders and coatings were investigated by optical and scanning electron microscopy while the level of porosity was evaluated using image analysis. Results show that homogenous composite coatings can be obtained from cladded spray dried powders.
Thermal Stability of Nanocrystalline Inconel 718 and Ni Prepared by High Velocity Oxy-Fuel (HVOF) Thermal Spraying
Authors: Jiang H.G. , Lau M.L. , Lavernia E.J.
Published: May 2021

Nanocrystalline Inconel 718 and Ni powders were prepared using two approaches: methanol and cryogenic attritor milling. High velocity oxy-fuel (HVOF) spraying of milled Inconel 718 powders was then utilized to produce Inconel 718 coatings with a nanocrystalline grain size. Isothermal heat treatments were carried out to study the thermal stability of the methanol milled and cryomilled Inconel 718 powders, as well as the HVOF Inconel 718 coatings. All nanocrystalline Inconel 718 powders and coatings studied herein exhibited significant thermal stability against grain growth as evidenced by a grain size around 100 nm following annealing at 1273 K for 60 min. In the case of the cryomilled nanocrystalline Ni powders, isothermal grain growth behavior was studied, from which the parameters required for the prediction of the microstructural evolution during a non-isothermal annealing were acquired. The theoretical simulation of grain growth behavior of nanocrystalline Ni during non-isothermal annealing conditions yields results that are in good correspondence with the experimental results.
CO2 Cooling in Thermal Spraying
Authors: Gourlaouen V. , Remy F. , Hansz B. , Coddet C.
Published: May 2021

Thermal spraying involves high temperatures which can be a serious problem for some applications. Among different possibilities existing to cool down a specimen during spraying, the use of liquid CO2 is one of the most attractive. However, care has to be taken to obtain good results due to the specific characteristics of CO2. Moreover, there are still some remaining problems which limit the growth of such system. One of the most important is the condensation of air humidity at the exit of the atomising nozzle. Therefore, a new design of the nozzle has been developed. This design avoid ice building up and can be easily fixed on any kind of spraying set up. Examples of working conditions are presented.
Refractory Carbide Coatings Sprayed by Electrothermal Explosion of Conductive-Ceramic Powders
Authors: Soda T. , Tamura H. , Sawaoka A.B.
Published: May 2021

This paper examines the properties of thermal spray coatings produced by electrothermal explosion. Three refractory carbides (TaC, WC, and TiC) were sprayed onto metal substrates then analyzed using FESEM, EPMA, XRD, and microhardness testing. The new spray technique required the development of a special powder container to facilitate melting as well as the jetting process and mixing of deposit and substrate materials. Crystal structure and phase changes were also observed, which are attributed to decarburization.
Basic Research for Reactive Plasma Spraying of TiO2
Authors: Suzuki M. , Sodeoka S. , Inoue T. , Ueno K.
Published: May 2021

Reactive Plasma Spraying (RPS) is one of several new plasma spray processes. Although several papers have been published on this technology, they are limited in scope to metal powders, such as Ti, Cr, and Si, and coatings composed of metal and non-oxide ceramics. When oxide powders are used among starting materials to fabricate metal or nonceramic coatings, it is important to understand and account for the reduction of oxides during spraying and the chemical reaction among the powder, plasma, and atmospheric gas. The work presented in this paper focuses on the reduction of plasma-sprayed TiO2 and how it is influenced by the amount and type of plasma and chamber gas used, the addition of carbon powder, and process parameters such as chamber pressure.
Prebrazing of Ceramics by Plasma Spraying for Metal-Ceramic Joining
Authors: Kara-Slimane A. , Treheux D.
Published: May 2021

Traditional brazing alloys do not wet ceramics and are therefore unusable for metal-ceramic bonding. One way to overcome the problem is by depositing a metal layer onto the ceramic prior to brazing. The approach taken in this paper was to plasma spray copper onto different ceramics (Al2O3, AlN, SiAlON) and then assess the wettability of potential brazing alloys (AgCu, AgCuTi). Interface analysis showed that silver and titanium segregation occurs at the ceramic surface and that, conversely, sprayed copper diffuses into the brazed joint.
Influence of Bondcoat Surface Characteristics on the Performance of TBC Systems
Authors: Knight R. , Smith R.W. , Zhangxiong D. , Kim E.-H. , Sahoo P. , Bucci D.
Published: May 2021

The objective of this study was to investigate the effects of thermal spray process selection and corresponding bondcoat surface roughness on thermal barrier coating (TBC) performance. TBC's consisting of a 300 µm (12 mil) thick air plasma sprayed (APS) top coating of ZrO2-8 Wt.% Y2O3 and CoNiCrAlY bondcoats deposited by three different thermal spray processes were produced and their surface roughness characterized. The bondcoats were deposited using low pressure plasma spray (LPPS), shrouded air plasma spray (SPS) and high velocity oxy-fuel (HVOF) combustion spray. Bondcoat surface profiles were measured by profilometric and interferometric techniques and surface roughness values calculated. TBC performance was evaluated by adhesive bond strength testing, thermal shock and thermal cycling testing, and microstructural analysis. Results showed that the bondcoat deposition process used and corresponding surface roughness had significant effects on the adhesive strength, thermal shock and thermal cycling lifetime, and failure mechanisms.
Influence of Interfacial Temperature on the Adhesion Properties of Plasma-Sprayed Metal-Ceramic Coatings
Authors: Lima C.R.C. , Trevisan R.D.E.
Published: May 2021

Metal-ceramic coatings have been widely used for industrial applications, mainly in the thermal barrier coating technology (TBC). Plasma spraying is the common manufacturing process of TBC's. Conventional thermal barrier coatings consist of a metallic bond coat layer and an insulating ceramic overlay. Graded coatings or functionally gradient coatings have also been applied in order to solve the problems associated with the early spallation of plasma-sprayed conventional TBCs. Temperatures and gradients during plasma spraying have and important influence on the coating quality, specially the temperature of the particles just hitting the substrate surface. When applying so distinct materials like metals and ceramics this fact has an increased importance. In this work metal-ceramic coatings have been applied on metallic substrates. The interfacial temperature measurements were performed by optical pyrometry. The substrate temperature was measured by thermocouples. The adhesion of the coatings was determined by standard ASTM tests and correlated with the measured temperatures. In a general way, results show that the coatings with lower adhesion values were that with lower interfacial measured temperatures.
High Temperature Oxidation of Bond Coats in Thermal Barrier Systems
Authors: Peraldi R. , Monceau D. , Pieraggi B. , Malie A.
Published: May 2021

The isothermal oxidation of bond coats composed of vacuum plasma sprayed (VPS) MCrAlY (NiCoCrAlYTa and CoNiCrAlY) or palladium modified nickel aluminides (NiPd + APVS) was studied in several oxygen partial pressures (105, 1 and 10-5 Pa), with two heating rates (20 and 60K/min) at different temperatures (900, 1000 and 1100°C). For MCrAlY coatings, Arrhenius plots of the parabolic rate constants show a kinetic transition below 1000°C. This could be linked to a transition from Al2O3 to Cr2O3 scale growth. Lower oxygen partial pressures induce lower parabolic rate constants at 900°C. This leads to the assumption that scales grown at low oxygen partial pressures are still formed of alumina at 900°C. Nevertheless, these results could not be confirmed by chemical analysis (EDS, XPS). The two tested heating rates show no influence on the oxidation kinetics of both MCrAlY coatings. In the case of aluminide, for low oxygen partial pressures, the parabolic kinetics are reduced of one order of magnitude (for PO2 = 105 to 1 Pa) and correspond to a thinner scale of α-alumina. Also, the heating rate modifies the parabolic kinetics (i.e. after the transient stage) and the total weight gains for all oxidation temperatures, with higher parabolic rate constants after heating at slower rate.
Anisotropic Microstructure of Plasma-Sprayed Deposits
Authors: lavsky J. , Long G.G. , Allen A.J. , Leblanc L. , Prystay M. , Moreau C.
Published: May 2021

The microstructure of plasma-sprayed deposits (PSD) is dominated by two void systems - interlamellar pores and intralamellar cracks - each with a different anisotropy. Varying anisotropics and crack-to-pore ratios within PSDs are responsible for the anisotropic properties observed in the deposits. While it is difficult to apply standard porosity measurement techniques to the assessment of anisotropic microstructures, novel techniques utilizing different approaches have recently emerged. Image analysis (IA) of impregnated PSD samples is the most direct technique. The structure is stabilized by impregnation and then polished and imaged. The limitations of IA lie in the impregnation process and in the subsequent polishing. Also, the images produced from anisotropic materials can be difficult to interpret quantitatively. The technique of small-angle neutron scattering (SANS) has recently been successfully applied to the study of PSDs. The major advantages of SANS are that it does not require sample preparation and that quantitative information can be gotten about the separate crack and pore systems, including their distinctive anisotropics. However, the relationship between the SANS results and the underlying structure is more complex and less intuitive than for IA, and the availability of the SANS technique is limited by the need to have access to a powerful neutron source, such as a reactor. Also, the two techniques present different views of the microstructure because of the different sensitivities in different parts of the size range. This paper compares results from IA and SANS from a set of thick plasma-sprayed ceramic deposits possessing a range of crack/pore microstructures, and discusses how the two techniques might complement one another.
Evolution of the Microstructure of Plasma-Sprayed Deposits During Heating
Authors: Ilavsky J. , Long G.G. , Allen A.J.
Published: May 2021

The evolution of the void microstructure of yttria-stabilized zirconia (YSZ) plasma-sprayed deposits (PSD) was studied as a function of heating in air from room temperature to 1400°C , and during a constant temperature hold at 1100°C for 19 hours. The samples were studied using the terminal slope (Porod scattering) of small-angle neutron scattering (SANS), modified for the analysis of anisotropic structures. The experiment was done in-situ using a special furnace built for use on the small-angle scattering instrument. SANS Porod scattering can distinguish between the two major void systems - interlamellar pores and intralamellar cracks - that are present in the PSD microstructure. Thus, changes in the void surfaces of the cracks and the pores could be followed separately as a function of temperature. The surface area attributable to the interlamellar cracks significantly decreased at temperatures below 1000°C, whereas the surface area of the interlamellar pores only began to decrease at temperatures above 1000°C. This suggests that there are significant differences in the sintering of these two void systems, probably associated with differences in their sizes and shapes. The first noticeable changes in the void surfaces were observed at temperatures just above 600°C, which is a very low temperature for YSZ. During annealing at 1100°C for 19 hours, there was a decrease in the interlamellar surfaces of about 10%.
Comparison Between the Effectiveness of Mental Practice and Physical Practice using Cup Stacking on Hand Function in the Elderly
Authors: Prasomsri Jaruwan , Wadbanjerd Jenjira , Suttinon Tiriporn , Keereena Sakongkorn
Published: May 2021

Objective: The objective of this study was to investigate the effect of mental vs. physical cup stacking practice in healthy people aged over 65 years.Material and Methods: Healthy elderly, who met the inclusion criteria, were randomized into 2 groups—physical practice and mental practice. Both groups received cup stacking training according to the specific condition of the group. This study collected data on the immediate effects of the training using the Jebsen Hand Function Test (JHFT) for both hands, the dominant and the non-dominant ones. The movement time during cup stacking and reaction time were measured. The paired t-test and the independent t-test were selected to analyze the differences within and between groups, respectively.Results: There were 39 participants in each group. It was found that the movement time related to stacking cups and the JHFT movement time of the non-dominant hand was significantly lower in the physical practice group compared with the mental practice group. Besides, after training, the movement time for stacking cups and the JHFT movement time of both hands was significantly lower in both groups. However, a statistically nonsignificant result for reaction time was found in the mental practice group after training.Conclusion: This study shows that both mental and physical training can enhance the ability to learn hand movement in the elderly. In further studies, the inclusion of the retention of training effects after practice, a different training approach, and a feedback method should be considered.
Penegakan Hukum Terhadap Kebakaran Hutan Di Kabupaten Pelalawan Provinsi Riau Berdasarkan Undang-Undang Nomor 41 Tahun 1999 Tentang Kehutanan
Authors: Utama Andrew Shandy , Rizana Rizana
Published: May 2021

Kebakaran hutan bukan merupakan fenomena yang langka di Indonesia, khususnya di Kabupaten Pelalawan Provinsi Riau. Pada tahun 2019 terjadi kebakaran hutan di Kabupaten Pelalawan seluas 827 Ha serta dikunjungi langsung oleh Presiden Joko Widodo pada tanggal 17 September 2019. Penelitian ini bertujuan untuk menjelaskan penegakan hukum terhadap kebakaran hutan di Kabupaten Pelalawan Provinsi Riau berdasarkan Undang-Undang Nomor 41 Tahun 1999 tentang Kehutanan. Metode yang digunakan dalam penelitian ini adalah penelitian hukum sosiologis. Berdasarkan Pasal 50 ayat (3) huruf d Undang-Undang Nomor 41 Tahun 1999 tentang Kehutanan ditegaskan bahwa setiap orang dilarang membakar hutan. Akan tetapi, pada tahun 2019 terjadi kebakaran hutan di Kabupaten Pelalawan seluas 827 Ha. Implementasi Undang-Undang Nomor 41 Tahun 1999 tentang Kehutanan terhadap kebakaran hutan di Kabupaten Pelalawan belum berjalan sesuai harapan. Membakar hutan merupakan tindak pidana. Penegakan hukum terhadap tindak pidana pembakaran hutan di Kabupaten Pelalawan yaitu berdasarkan pada Pasal 78 ayat (3) Undang-Undang Nomor 41 Tahun 1999 tentang Kehutanan ditegaskan bahwa barang siapa yang dengan sengaja membakar hutan dapat diancam dengan pidana penjara paling lama 15 tahun dan denda paling banyak Rp5.000.000.000,-. Pemerintah Kabupaten Pelalawan dapat melakukan upaya pencegahan untuk meminimalisir terjadinya kebakaran hutan dengan melaksanakan penyuluhan hukum ke tengah-tengah masyarakat mengenai larangan membakar hutan serta meningkatkan peran masyarakat dalam menjaga kelestarian hutan yang ada di sekitarnya.