bluuebunny/crossref_metadata_2025 huggingface dataset:
Wear Properties of WC/Co Coatings with Plasma and High Velocity Oxyfuel Spraying
Authors: Akasawa T. , Ai K.
Published: May 2021

A tungsten carbide/cobalt hard coating was deposited on steel substrates using plasma-arc and high velocity oxyfuel flame (HVOF) spraying. The characteristics of the coatings made by the two spraying methods were evaluated under identical conditions. The microstructure and the chemical composition ofthe coatings were different depending on the powder heating temperature and the velocity of particles. The sliding wear properties of the coatings against hardened steel at high sliding speeds showed different tendencies from those at low speeds. The plasma sprayed coatings resulted in better abrasive wear properties than HVOF coatings did. Material removal by solid particle erosion depended on the striking angle of particles on the substrate surface but there are no clear differences in wear properties between the two coatings.
Modelling of Coating Thickness, Heat Transfer and Fluid Flow and Its Correlation with the TBC Microstructure for a Plasma Sprayed Gas Turbine Application
Authors: Nylen P. , Wigren J. , Pejryd L. , Hansson M.-O.
Published: May 2021

The plasma spray deposition of a zirconia thermal barrier coating (TBC) on a gas turbine component has been examined using analytical and experimental techniques. The coating thickness was simulated by the use of commercial off-line programming software. The impinging jet was modelled by means of a finite difference elliptic code using a simplified turbulence model. Powder particle velocity, temperature history and trajectory were calculated using a stochastic discrete particle model. The heat transfer and fluid flow model were then used to calculate transient coating and substrate temperatures using the finite element method. The predicted thickness, temperature and velocity of the particles and the coating temperatures were compared with these measurements and good correlations were obtained. The coating microstructure was evaluated by optical and scanning microscopy techniques. Special attention was paid to the crack structures within the top coating. Finally, the correlation between the modelled parameters and the deposit microstructure was studied.
Fe-Simulations of Temperature and Stress Field Distribution in Thermally Sprayed Coatings Due to Deposition Process
Authors: Lugscheider E. , Barimani C. , Eritt U. , Kuzmenkov A.
Published: May 2021

During the formation of coating systems we find strong temperature gradients within the coating-substrate system resulting in thermally induced stresses in the coating after the spraying process. The purpose of this investigation is to develop numerical tools which provide insight into the relationship between coating parameters and the thermomechanical response of the produced composite. Transient finite element modelling is applied to calculate temperature and stress histories in thermally sprayed coatings due to the deposition process. Two different models with different levels of complexity have been developed to investigate the spraying process on a macroscopic and on a microscopic scale. Experimental investigations of the temperature history during spraying in the substrate have been carried out to determine boundary conditions for the mathematical model and to enable a verification of the obtained results.
Flattening Mechanism in Thermal Sprayed Particle Impinging on Flat Substrate
Authors: Fukumoto M. , Huang Y. , Ohwatari M.
Published: May 2021

The transitional behavior of the splat pattern of Ni particles sprayed on a flat substrate was investigated. Based on Auger analysis and SEM observation, it was confirmed that the splashing was formed not by material flowing on the substrate surface from the impingement center to the periphery, but by jetting away from the central disk. Observations of etched splat surfaces revealed that the bottom portion of the central disk solidified rapidly after impingement, and it was also confirmed, based on the direction of the splash pattern, that the splashing was caused by stumbling due to some type of deterrent to liquid flow, such as poor wettability at the flow tip or initial rapid solidification of the splat. The drastic change of the splat pattern near the transition temperature seems to occur when the Weber number of the liquid flow coincides with some critical value.
Integrated Simulation of the Atmospheric Plasma Spraying Process
Authors: Kundas S. , Kuzmenkov A. , Lugscheider E. , Eritt U.
Published: May 2021

The main purpose of this work is the development of mathematical and computer models for the integrated simulation of all stages of the atmospheric plasma spraying process (APS) with temperature dependent thermophysical and mechanical properties of the used materials and gases and experimental verification of the simulated results. The following mathematical models of APS were created: particle heating and movement in the plasma jet; coating structure formation; heat transfer and residual stresses in the coating-substrate system. The computer realization of these models enables us to model all stages of APS (integrated or separately). Databases of coating, substrate and plasma-gas substances include the temperature dependent properties. The model of APS is divided in 3 parts, which are connected by continuous data interface. Two dimensional approximation of plasma-gas velocity and temperature in the free plasma jet was used for computation of particle velocity, trajectory and temperature. This information was created with a special Graphic program module and included in database. Computer experiments for plasma spraying of Ah03 and ZrO2+8%Y2O3 in Ar/H2 plasma were carried out. The experimental verification of developed models with High-Velocity-Pyrometry (HVP) and Laser-Doppler-Anemometry (LDA) have shown the satisfactory precision of simulated results.
In Situ Measurement Within Plasma-Sprayed Zirconia Coatings Under Industrial Conditions
Authors: Baradel N. , Bianchi L. , Blein F. , Freslon A. , Jeandin M.
Published: May 2021

The thermomechanical properties of plasma-sprayed deposits strongly depend on residual stress distribution. This latter is mainly attributed to the relative torch/substrate velocity as well as to the cooling system location and efficiency. The determining of both quenching and thermal stresses, which are generated respectively during spraying stage and cooling stage, is then required to improve coatings quality. A rather simple apparatus, which consists in monitoring the curvature of a beam substrate during the whole deposition process, has been developed to work under industrial conditions. It has been applied to partially stabilized zirconia coatings performed onto stainless steel and cast iron substrates. Spraying temperature and plasma gun velocity have been selected as relevant parameters for this study about stress generation and mechanical release. Finally, four point bend tests have been performed on deposited samples to measure coating mechanical properties and to evaluate damage level.
Fatigue Strength and Fracture Mechanism of Thermally Sprayed WC-Co Coating on a Medium Carbon Steel by HVOF
Authors: Tajiri T. , Sakoda N. , Watanabe S. , Amano J.
Published: May 2021

Fatigue strength and fracture mechanism of a medium carbon steel with HVOF thermally sprayed WC-Co coatings were investigated under rotating bending. Two types of commercially available WC-Co powders were used, which have similar total chemical composition with different manufacturing processes. The fatigue strengths of the specimens with thick coatings were lower than that with thinner ones. Especially, it was found that the fatigue strengths of the thick coating specimens decreased more greatly than that of the grit blasted ones. Also, the morphology of the fatigue crack depended on the type of powders and the thickness of the coating. Futhermore, an embedded Al2O3 grit and a crack generated during the grit blasting were found near the fatigue fracture origin of the coated substrate.
Standardization of Metallographic Practices for Thermally Sprayed Coatings in the Automotive Industry
Authors: Blann G.A.
Published: May 2021

Thermally-sprayed coatings are applied to various materials to provide protection for beat-loaded parts as well as corrosion and wear. They also serve as a thermal barrier to reduce metal substrate temperatures. Microstructural analysis is used to characterize the substrate, the coating, and the adherence of the coating to the substrate. Accurate evaluation or these coatings depends heavily upon the quality of the polished surface produced by metallographic preparation. A well-prepared surface must first be free of plucked material and have minimal relief between the hard and soft constituents. The entire surface must be flat to allow a clear view of the interface and any reaction products that might be present in the coating or the substrate. Furthermore, the finished polished specimen must be scratch-free and have no resolution destroying films or stains. Various metal and oxide coatings on ferrous substrate material are used to demonstrate the excellent microstructural detail that is revealed when correct polishing procedures are used. These special techniques successfully address the problems normally encountered when preparing hard, brittle coatings or softer metallic coatings and substrates. As a result, clear microstructures are revealed across the specimen surface and valuable information is obtained.
Study on the Spray Processes and Characteristics of Cr3C2/NiCr Coating
Authors: Liu M. , Wang D. , Wang J. , Dai M. , Zhou K.
Published: May 2021

HVOF and plasma spray processes were used to apply Cr3C2-NiCr coatings, which were then characterized by X-ray diffraction and various other tests. The results revealed that the HVOF coatings were more stable than their plasma-sprayed counterparts as well as harder, tougher, less porous, and more erosion resistant. The HVOF coatings have been successfully used in industry and have proven to be an acceptable alternative to electroplated chromium.
Improvement of Adhesion Strength and Formation of Veined Structure in Alumina Coating
Authors: Era H. , Otsubo F. , Kishitake K.
Published: May 2021

Alumina coatings plasma-sprayed on alumina substrate with metallic bond coating (50Ni-50Cr) and on metal (Ni) substrate have been investigated in terms of adhesion strength and a veined structure formed in alumina coating. The veined structure is formed to heal up cracks and pores in sprayed alumina and substrate alumina after heat-treatment in air. The veined structure consists of oxides of NiAl2O4 (spinel-type) and NiO (NaCl-type). This indicates that the metallic elements in the bond coating or the metallic substrate diffuse along the cracks and pores in alumina and react with alumina. The alumina coating with veined structure shows high strength due to the mechanical anchoring of veined oxide and chemical bonding.
In-Flight Particle Characteristics of Plasma-Sprayed Dense Yttria Stabilized Zirconia
Authors: Leblanc L. , Moreau C.
Published: May 2021

The influence of input spray parameters on the state of plasma-sprayed zirconia powder is studied. The particle temperature, velocity and diameter are measured using an integrated optical monitoring system. The monitoring system allows the investigation of the particles behavior in the spray jet. The collected information is correlated to coating characteristics such as deposition efficiency, microstructure and thermal diffusivity. Results show that, by monitoring the state of sprayed particles, a better understanding of the coating microstructure and properties can be achieved.
Effect of In-Flight Particle Characteristics on the Properties of Plasma Sprayed NiCrAlY & NiCoCrAlY
Authors: Pejryd L. , Wigren J. , Gougeon P. , Moreau C.
Published: May 2021

Plasma sprayed MCrAlY bondcoats play a major role in thermal barrier coatings. During service, oxide forms on both sides of the bond coat and must be minimized to prevent coating failures. Along with powder chemistry, coating microstructure significantly influences oxide growth. It is known that both coating microstructure and coating strength are strongly related to plasma spraying parameters. This present work examines the effect of inflight particle properties on the adhesion strength and microstructure of NiCrAlY and NiCoCrAlY bondcoats. The relation between particle velocity and temperature and coating properties is particularly important. Relatively small changes in spray parameters such as arc current and gas flows can have a major impact on sprayed particles and consequently coating microstructure. Through online control of particle states it is expected that the quality of plasma-sprayed MCrAlY coatings can be significantly improved.
Controls for Plasma Spraying Based on Plasma Jet Stability Analysis
Authors: Beall L. , Duan Z. , Schein J. , Heberlein J. , Stachowicz M. , Planche M.P.
Published: May 2021

Despite the fact that plasma spraying has been a widely used technology over the past three decades, industries using this technology still need higher quality products. Presently, only a small degree of process control is used in most plasma spraying systems. Improved process control should lead to more consistent results and higher quality products. We discuss a relatively simple control scheme consisting of a microphone as a primary sensor and a fuzzy logic look-up model indicating the condition of the anode. Selected frequency peaks in the power spectrum of the microphone signal are analyzed online, and the results are correlated with an average jet length obtained from a series of high speed images. The jet length, in turn, is correlated with coating characteristics. A simple feedback control system is proposed which will counteract the negative effects of an eroded anode on coating quality.
In-Situ Observation and Acoustic Emission (AE) Analysis of Microscopic Fracture Process of Thermal Spray Coatings
Authors: Akita K. , Zhang G. , Takahashi S. , Misawa H. , Tobe S.
Published: May 2021

Microscopic fracture mechanisms of thermal spray coatings under bending stress are investigated. Samples of thermally sprayed coatings were made using three distances. The sprayed powder was pure molybdenum. Vertical microcracks occur in lamellae and subsequently, these cracks join together and form vertical macrocracks in the samples sprayed with a short spraying distance. On the other hand, horizontal microcracks occur at the lamellae interfaces, and these cracks link together in the samples sprayed with a long spraying distance. These tendencies can be explained in terms of the hardness of the lamella and the bonding strength between each lamella. It is clarified that the bonding strength between each lamella corresponds to the applied strain at the point of rapid increase of the acoustic emission (AE) event. The amplitude and rate of AE beyond the point of rapid increase are high in the coatings which formed macrocracks. It is concluded that the coating which has high resistance to crack formation has a high point of AE increase, low AE amplitude and low AE increasing rate.
Evaluation of Adhesion and Properties of Sprayed Coating by Ultrasonic Testing Method
Authors: Suga Y. , Lian D.
Published: May 2021

This study evaluates a nondestructive method for determining the adhesion strength and porosity of thermally sprayed coatings. The method is based on ultrasonic surface echo measurements. Porosity is surmised by the impedance of the coating and adhesion by the transmission coefficient. Experimental results confirmed that the method is effective for its intended use.
QS-9000 – Using the Automotive Requirements to Improve Existing ISO 9000 Systems
Authors: Young J.F.
Published: May 2021

In this paper, we will discuss how to incorporate several of the QS-9000 quality system requirements into an existing ISO 9000 quality system. This expansion of the existing quality system will be cost effective and ensure that the continuous improvement program will meet its goals. The QS-9000 quality system was developed in 1994 by the "Big Three" automotive and truck producers in Detroit, Michigan. This document, originated in the United States, is based upon the International Standard: ISO 9001-94. It is mandatory that any supplier of goods and/or services to either Chrysler, Ford or General Motors must have their quality system registered to the QS-9000 standard. We believe that there can be benefits to non-automotive organizations if they will incorporate some of the QS-9000 clauses into their current ISO 9000 quality systems. We will discuss actual cases in the following areas: purchasing, safety, process control, training, business management and continuous improvement. We will show how these examples of quality system enhancement are both effective and efficient ways of driving cost reduction and process improvement programs. Cost of quality initiatives can be better managed.
Experimental Design Based on Mclean & Anderson Modeling Applied to the Prediction of Plasma Properties
Authors: Blein F. , Roussel E. , Freslon A.
Published: May 2021

This paper presents a method for optimizing plasma spraying parameters based on statistical analysis and related models. The models presented account for particle velocity and plasma mass enthalpy and make it possible to study the influence of plasma properties on the deposition process.
Effects of Powder Morphology on Pneumatic Feeding and Plasma Spray Deposition
Authors: Anderson I.E. , Sordelet D.J. , Besser M.F. , Terpstra R.L.
Published: May 2021

The demand for highly continuous thermal spray deposition processing to gain manufacturing efficiency and enhanced control of deposition microstructure has driven the search for powder feedstocks that exhibit uniform flow behavior in pneumatic feeding devices even at low carrier gas flow ratios. This paper compares the continuous powder feeding characteristics of one type of feeding device for two different powder alloys fabricated by a representative set of powder processing methods, including spray dried, fused (cast) and crushed, and inert gas atomized. Powders were fabricated by both commercial vendors and Ames Laboratory processing equipment. The powder mass flow rate was found to depend directly on the apparent density of a specific powder type instead of the dry powder flowability, as initially expected.
SOFC Components Production – An Interesting Challenge for DC- and RF-Plasma Spraying
Authors: Henne R. , Schiller G. , Borck V. , Mueller M. , Lang M. , Ruckdaschel R.
Published: May 2021

Solid oxide fuel cells (SOFC) are expected to gain a high importance as direct converters for transforming chemical into electrical energy. They have the potential of working with considerably higher efficiency and much less environmental problems compared to systems used so far. SOFCs of present technology operate at temperatures in the range of 950 °C. Besides an increase in performance and stability, a main precondition for a technical breakthrough of SOFCs is a drastic reduction of their production costs. Approaches are the use of less-expensive materials, new SOFC designs with thinner components and the improvement of presently applied production routes, or their replacement by other techniques such as thermal spray methods. DC- and RF-VPS show very attractive properties particularly if the cell will be manufactured in one consecutive combined process. The state of SOFC spray design will be described together with results of the process adaptation and the SOFC components development.
A Contribution to Methodology and Protocol Definition for Thermal Spray Coated Surface Compatibility Analysis in Food Processing Applications
Authors: Scrivani A. , Antolotti N. , Bertini S. , Viola G. , Groppetti R. , Gutema T. , Mangia A. , Mucchino C.
Published: May 2021

The paper discusses the testing methodology and identifies the analytical protocols, with proper validation, in order to evaluate the compatibility of thermal spray coatings in the food production technology, according to EU and FDA applicable standards. A brief state-of-the-art analysis of the international standards on food additives and human health is given, namely on indirect food additives (as defined in 21 CFR 170.3(e)), that can migrate into the food during the process. An outline of the test protocols, based on contact between coating and food simulating solvents in a set time/temperature conditions, are presented, and the main phases for the proposed testing methodology, as the choice of the simulating solvent, the migration cell design and the time/temperature conditions, are discussed. Finally the proposed methodology and protocols are validated through a thermal spray coating for food process application test case.
The Influence of Coated Mould on Heat Transfer and Microstructure for Horizontal Strip Casting of Aluminium Alloys
Authors: Isac M. , Netto P. , Guthrie R.I.L. , Tavares R.
Published: May 2021

Experimental apparatus simulating a horizontal belt caster has been constructed for the study of thin strip casting of steels and light metal alloys. In this apparatus, the solidifying metal is deposited onto a moving substrate. The substrate was flame sprayed with various commercial coatings while its speed and the thicknesses of strip produced matched industrial values. The main objective of the present work was to determine the influence of various operational variables on local cooling rates and final microstructures. To this end, experiments were carried out to study the effects of various types of coating, roughness of the substrate, initial superheat, and strip thickness on heat fluxes. An interesting feature of this equipment is that the strip is subjected to different rates of cooling at the lower and upper surfaces, allowing two different rates of solidification to be studied simultaneously.
Plasma Spray Ceramic Plunger for Polymer Pump
Authors: Wu C.J. , Shao T.M. , Mu A.G. , Du W.L.
Published: May 2021

Polymer injection is an effective technique for increasing oil production in the later stage of petroleum exploitation. The pumps used typically incorporate ceramic plungers because they do not produce metal ions which tend to decrease polymer viscosity. This paper compares the performance of plasma sprayed and sintered alumina plungers and includes the results of stress analysis using finite elements and field testing. Under real working conditions, plasma sprayed plungers achieved an average lifetime of 12,000 hours, approximately double that of their sintered ceramic counterparts.
Applications of HVOF Sprayed WC Cermet Coatings for Paper Mills
Authors: Tani K. , Nakahira A.
Published: May 2021

Some applications of high velocity oxygen fuel (HVOF) flame sprayed WC cermet coatings in paper mills are summarized. The WC cermet sprayed coating is one of the most widely used in the thermal spray industry. HVOF sprayed WC cermet coatings have such excellent physical and chemical properties that they are extensively employed in the industrial field. Typical properties for example, are wear resistance, high stress rotating bending or rolling contact fatigue strength, frictional characteristics, wettability for aqueous agent, non picking or non adhesive property against foreign material, thermal conductivity, mirror finished surface property and so on. They are derived from the compact, denser microstructure, containing fine-sized hard WC particles, high bond strength onto substrate. These characteristics obtained by HVOF sprayed WC cermet coatings are utilized to improve the surface functions of machine parts which are installed mainly in the press department, drying department, size press, calender department and finishing department of paper mills. In this study, examples of some application of WC cermet coatings in several types of rolls in paper mills are introduced.
The Application of Thermal Spraying Technology in the Oil and Gas Industry
Authors: Price J.C.
Published: May 2021

The last decade has seen a rapid increase in the use of Thermally Sprayed Coatings for Oil and Gas production applications. In particular, since 1982 the Offshore Oil and Gas Industry has considered Thermally Sprayed Aluminum (TSA) for protection of steel structures in the splash zone and other areas in the marine environment. Experience to date has indicated that when TSA is properly applied with a specific sealer system a service life in excess of 30 years with zero maintenance is possible. This produces a corresponding reduction in life cycle costs. Other coating systems such as nickel-based alloys, ceramics and thermoplastics are also finding useful applications. This paper discusses recent advances in thermal spraying technology and current and future applications in the Oil and Gas Industry. This is illustrated with reference to several projects and details on life cycle costs. In particular, thermal spraying of pressure vessels, risers, pipelines and structural components are detailed.
Fabrication of Composite SiC-MoSi2 Powders Through Plasma Reaction Process
Authors: Fan X. , Ishigaki T.
Published: May 2021

This study was aimed at the production of SiC-MoSi2 composite powders through a high-temperature plasma reaction route. The addition of SiC appears to be the best second phase reinforcement for improving the mechanical properties of MoSi2 material for high-temperature structural application. The in-flight carbonization of MoSi2 powders was carried out in an Ar-H2-CH4 induction plasma process. Using methane served as both the powder carrier gas and the "precursor" to react with the MoSi2 powders forming the SiC phase in-situ. Under the experimental conditions employed in this investigation, up to about 8.0 wt. % of carbon was incorporated into the MoSi2 powder particles. The chemical composition, phase content and the microstructure of the composite powder products were examined by XRD, SEM, EDS etc. analysis methods. The reaction mechanisms are discussed in terms of the calculated thermodynamic equilibria.
Plasma Spray Forming of Free Standing W-AI Functionally Graded Materials
Authors: Blein F. , Freslon A.
Published: May 2021

The aim of this study is to produce free-standing functionally-graded structures in which density varies continuously from 2.2 to 17.3 g/cm3 through a total thickness of 4.5 mm. In order to optimize material performance, it is necessary to account for the different combinations or ratios of materials (i.e., tungsten and aluminum) in the plasma jet when determining mixture laws. A relationship based on the deposition efficiency, powder feed rate, and density of individually sprayed materials has been established and was used to predict the density, thickness, and deposition efficiency of the combined materials. The mixture laws were found to be in good agreement with experimental results, making it possible to build up coatings with a parabolic density profile and uniform layer thickness.
Increasing Performance of Plasma Spray Formed Components
Authors: O’Dell J.S. , Mckechnie T.N. , Holmes R.R.
Published: May 2021

Near-net-shape spray forming reduces the cost and complexity of fabricating certain types of structures. Although such components perform adequately as-sprayed, improvements achieved through alloying, thermal treatments, and additional coating steps are often worth pursuing. In tungsten components, for example, additions of rhenium, nickel, or iron can significantly improve material strength and ductility; thermal treatments such as heat treating and hot isostatic pressing can change and densify microstructures; and coating exposed surfaces can improve environmental compatibility. Such improvements in plasma spray formed refractory metal components are presented in this paper.
A Gas Shroud Nozzle for HVOF Spray Deposition
Authors: Pershin V. , Mostaghimi J. , Chandra S. , Coyle T.
Published: May 2021

Properties of MCrAlY coatings obtained by High Velocity Oxy-Fuel (HVOF) thermal spray process operated in a standard configuration were compared with those obtained using a gas shroud attachment to the HVOF gun. Our measurements show that the attached gas (nitrogen) shroud nozzle considerably reduces the oxygen content in the coating without an appreciable change in the microstructure. The particle temperatures were decreased by an average of 100 °C at a standoff distance of 0.275 m (11 inches). There was also a large reduction in the particle velocity at this distance. Both these effects were related to the excessive amount of nitrogen used for shrouding.
Reactive Plasma Spraying of 80:20 Ni/Cr and MCrAlY Powders with Hydrocarbon Reactive Gases
Authors: Al-Sabouni O. , Stephenson D.J. , Nicholls J.R. , Creffield G.
Published: May 2021

Reactive plasma spraying (RPS) with hydrocarbon (HC) gas has been studied as a way to improve the mechanical properties of Ni-Cr alloys and reduce the oxygen content of MCrAlY coatings. A conventional dc plasma torch has been modified by attaching a conical graphite tube (reactor) onto the end of the gun and spraying parameters were adjusted accordingly. Significant improvements have been achieved in terms of both objectives. As test results indicate, the hardness of Ni-Cr alloys has been doubled and the oxygen content in MCrAlY coatings has been reduced by an order of magnitude.
Ceramic Coatings Obtained on Superalloys Modified by Laser Treatment
Authors: Kobylanska-Szkaradek K. , Swadzba L.
Published: May 2021

The paper presents the influence of laser-beam remelting of Al2O3-Ni ceramic layers spread on creep-resisting alloy by means of plasma spray upon the quality of ceramic coatings, which form thermal barrier and high temperature corrosion shield of these alloys. The examination showed that 0.103.109 W/m2 power density laser-beam scanning ensures good quality of coatings at beam moving rate 1 to 2 m/min. At smaller scanning rate, laser remelted ceramic layer spalls and chips. Better quality of the ceramic coatings can be obtained by diffusive chromoaluminizing applied prior to laser remelting. Laser-beam remelting conditions of such layers, elaborated in the course of examination, ensure pores fading, decrease of remelted layer thickness and increase of base adhesion without cracks, chips and spalls. Additionally remelted zone features either strong break up of structure or the structure is amorphic with unchanged chemical composition as to the matrix chemical composition. Obtained results are the base for the elaboration of thermal barrier technology and the technology of anticorrosion shield for creep - resisting alloys applied in high temperature power engineering.
Phase Transformations in Laser Treated Hydroxyapatite Coatings
Authors: Ranz X. , Aslanian T. , Pawlowski L. , Sabatier L. , Fabbro R.
Published: May 2021

Hydroxyapatite (HA) was plasma sprayed onto titanium alloy substrates. One set of samples had a crystalline content of 25%, the other set, 30%. The coatings were then subjected to CO2 laser treatments at different power levels and scanning rates while surface temperatures ware monitored with a pyrometer. XRD analysis verified the crystallinity of HA and the content of amorphous calcium phosphate as well as foreign phases. Optical microscopy revealed the microstructure and depth of the laser modified zone.
Study on Underwater Thermal Spraying
Authors: Minami N. , Hongawa T. , Nojiri Y. , Nishida M. , Araki T. , Katsumura M.
Published: May 2021

The objective of this study is to develop viable surface-treatment technologies for offshore and underwater structures. The study focused on cavity formation, which is a prerequisite to underwater plasma spraying using a fluid-stabilized local dry-wet method. Factors affecting cavity formation that were investigated in the study include slit angles on protection tubes, jet velocity of water curtains, and clearances between protection tubes and plate surfaces. All plasma-sprayed coatings formed underwater were made with pure Ti wire and then assessed to determine the influence of various factors on cavity formation. Macroscopic examination of the coatings revealed neither cracks nor peelings. X-ray analysis confirmed that coatings consisted mostly of Ti phase.
Practical Experiences with a New Portable HVOF Spraying and Cutting System
Authors: Voronetsky A.V. , Jagodnikov D.A. , Filimonov L.A. , Suchkov S.A. , Shirjaeva N.V. , Elisseev A.A. , Boronin E.V.
Published: May 2021

Current HVOF systems available on the world market are relatively complicated to operate and expensive. At the Bauman State Technical University in Moscow (BMSTU) a new portable HVOF spraying and cutting system MiniJet-30 has been developed. This rugged system offers the ease of operation of conventional gas welding equipment and produces high quality HVOF coatings. In this paper, the results of numerical simulation calculations of supersonic gas/powder flows, with and without a particle mask, are presented and compared with experimental outcomes. Additionally, typical HVOF coatings were sprayed and evaluated for bond strength, porosity, microhardness, abrasive wear, and phase composition (OM, XRD). The results are compared to those of other HVOF systems. Lastly, the cutting efficiencies for stainless steel, cast iron, and non-ferrous metals are discussed.
The High-Velocity Plasma Spraying
Authors: Klubnikin V.S.
Published: May 2021

This paper summarizes the results of several studies on the velocity of powder particles during plasma spraying. It presents and compares experimental data collected by numerous authors for a wide range of materials. An analysis of the data shows how plasma jets are affected by stream velocity, process parameters, and the density and size of powder particles. It also sheds light on the maximum velocity that particles can attain in different plasma streams.
Supersonic Induction Plasma Spraying of Yttria Stabilised Zirconia Films
Authors: Mailhot K. , Gitzhofer F. , Boulos M.I.
Published: May 2021

In this paper, supersonic RF induction plasma deposition of Yttria Stabilized Zirconia (YSZ) has been developed in order to produce dense solid electrolyte membranes for Solid Oxide Fuel Cells (SOFC). Different RF induction plasma torch configurations were tested. The results show that high density layers could be obtained using a supersonic Laval nozzle integrated on a standard torch. 50 to 100 um YSZ coatings with porosity of near 1% could be obtained using this technique at relatively high deposition rates (10g/min.). Attention has been given to the thin coating porosity measurement by using a proper calibration and back scattered electron micrographs of the deposit cross-section coupled with image analysis. Absolute porosity has been measured by using this technique described in another paper of the same conference.
An Improvement of Cr3C2-NiCr Sprayed Coatings Followed by Chromium Diffusion Treatment
Authors: Takeuchi J. , Murata Y. , Harada Y. , Tomita T. , Nakahama S. , Go T.
Published: May 2021

A hybrid technique that combines plasma spraying and metal diffusion treatment was developed to improve the density, hardness, and adhesion of carbide cermet coatings. In this study, which was conducted to assess the process, Cr3C2-NiCr was deposited on stainless steel substrates by atmospheric plasma spraying. The test specimens were then embedded in a powder mixture of chromium, alumina, and ammonium chloride and diffusion treated. Cross-sectional SEM imaging, X-ray diffraction, and microhardness testing found the resulting surface layer to be extremely dense with outstanding hardness and exceptional bonding strength.
Characterisation of Molybdenum Coatings by a Newly Developed Flame Spray Process
Authors: Calla E. , Modi S.C. , Niku-Lari A.
Published: May 2021

This paper assesses the performance of a supersonic flame spraying gun along with the quality of molybdenum coatings produced with it. The hardness of the wire sprayed molybdenum was compared to coatings made using conventional flame spraying methods. The coatings were also evaluated for porosity, bond strength, and phase distribution by X-ray diffraction. The results indicate that the supersonic gun performs better than conventional flame spray equipment when depositing refractory metals such as molybdenum.
A New Arc Spray System to Spray High Density, Low Oxide Coatings
Authors: Unger R.H. , Belashchenko V.E. , Kratochvil W.R. , Dunkerley J.P. , Sedov V. , Smith E.A.
Published: May 2021

A new arc spray system has been designed which produces coatings with very high density and low oxide content. Advantages of the new process are illustrated by a comparison of coating properties sprayed by a conventional arc process and the new system for various metals.
The Effect of Bond Coat Creep on Residual Stresses and Debonding in Plasma Sprayed Thermal Barrier Systems
Authors: Tsui Y.C. , Thompson J.A. , Clyne T.W.
Published: May 2021

Test pieces were machined from vacuum plasma sprayed (VPS) deposits of the bond coat materials Ni-22Cr-10Al-1Y and Co-32Ni-21Cr-8Al-0.5Y. Changes in gauge length at high temperatures under various applied stresses were measured using a scanning laser extensometer. In this way, isothermal creep data and, using no applied load, expansivity data were obtained. The CoNiCrAlY creeps faster than the NiCrAlY at low stresses, but the reverse is true at high stresses. The CoNiCrAlY has an appreciably higher expansivity than the NiCrAlY. These data were used in a numerical process model to evaluate the effect of bond coat creep on the stress state of a TBC system. Comparisons between measured and predicted curvature histories during deposition were used to evaluate the quenching stress for the two materials. This is considerably higher for the CoNiCrAlY. Although creep generally results in reduced stress levels at service temperatures, it can generate residual stresses which are raised after cooling down to ambient temperature, particularly for the CoNiCrAlY. Evaluation of the strain energy release rates associated with various stress distributions, and comparison with measured interfacial fracture energy values, confirmed that debonding will tend to occur at the top coat / bond coat interface, rather than between the bond coat and the substrate. However, bond coat spallation is more likely with CoNiCrAlY than with NiCrAlY.
Comparison of Thermal Cycling Experiments on Thick Thermal Barrier Coatings
Authors: Haubold T. , Wigren J. , Gualco C.
Published: May 2021

In the Brite Euram Project COMBCOAT Thermal Barrier Coatings for improved thermal protection with a thickness up to 2 mm have been developed for combustor applications. As a typical experiment to evaluate the quality of the coatings, life cycles to spallation by means of thermal cycling tests have been determined at ANSALDO Ricerche, BMW Rolls- Royce and Volvo Aero Corporation. To ensure that the ranking on the different cycling experiments are equivalent and to compare cycles to spallation reached in the different rigs, a comparison of 6 different coatings, highly porous as well as segmented ones, has been performed on the three different rigs. Results of the different tests demonstrated that a direct comparison of the result is not possible. The ranking and the number of cycles to spallation have been inconsistent for different specimen and rigs. Detailed simulation of experiments need to be performed to understand the differences between results.
Vacuum Plasma Sprayed ZrO2-Based Thermal Barrier Coatings for Aerospace Applications
Authors: Brzezinski T. , Cavasin A. , Grenier S. , Kharlanova E. , Kim G. , Tsantrizos P.
Published: May 2021

Zirconia-based thermal barrier coatings (TBCs), produced using Vacuum Plasma Spray (VPS) technology, were recently subjected to burner rig testing. The VPS TBC performance was compared to TBCs deposited using conventional Atmospheric Plasma Sprayed (APS) and Electron Beam Physical Vapor Deposition (EB-PVD) techniques. All of the coatings consisted of an MCrAlY bond coat and a partially stabilized ZrO2-8%Y2O3 (PSZ) top coat. The TBC coated pins (6.35 mm in diameter) were tested using gas temperatures ranging from 110CC to 1500°C. The pins were tested to failure under severe conditions (1500°C gas temperature, with no internal cooling). The initial testing indicated that under typical operating gas temperatures (1400°C), the VPS TBC performance was comparable, if not superior, to conventional TBCs. Following the encouraging results, thick composite TBCs, produced in a single-step operation, were investigated. Preliminary work on ZrO2-8% Y2O3/Ca2SiO4 composite TBCs with interlayer grading included thermal shock testing and temperature drop measurements across the TBC. The composite TBC thicknesses ranged from 850µm to 1.8 mm. Initial results indicate that thick adherent composite TBCs, with high resistance to severe thermal shock, can be produced in a single step using the VPS process.
Properties of Functionally Graded Zirconia Coating by Gas Tunnel Type Plasma Spraying
Authors: Kobayashi A.
Published: May 2021

The one problem of zirconia (ZrO2) coatings is control of the porosity, because the functionality of wear resistance, corrosion resistance, and so on are required for their application in the extreme environment. In this study, a high hardness and dense ZrO2 coatings is formed by a gas tunnel type plasma spraying under the condition of a short spraying distance. The properties of this ZrO2 coating formed are investigated about coating qualities, such as Vickers hardness characteristics, wear characteristic, etc. The graded functionality of this coating is clarified by the coating qualities.
First record of the Carassius auratus (Linnaeus, 1758) in inland waters of Ordu province and some data on the Ulugöl plateau pond population of the species
Authors: Bostancı Derya , Yedier Serdar , Helli Selma , Polat Nazmi
Published: May 2021

Aquarium fish trade is one of the global industrial areas that is gradually increasing in popularity throughout the world. The sectors all over the world as well as in Turkey is one of the major causes of the spread of invasive species. The non-native aquarium fish species is known for the existence of Turkish inland waters these days. In this study, Carassius auratus were recorded for the first time in the inland waters of Ordu province of the middle Black Sea Region. C. auratus was stocked in the Ulugöl Plateau Pond in Ordu-Mesudiye for fisheries purposes and adapted to this habitat.
Implikasi Sengketa Batas Wilayah Terhadap Penyelenggaraan Pemilu (Studi Kasus di Provinsi Maluku Utara)
Authors: Alwan Sultan
Published: May 2021

Pemekaran wilayah sebagai konsekwensi logis dari pelakasanaan otonomi daerah telah menimbulkan ekses sengketa batas wilayah yang berujung konflik. Kasus yang terjadi di 6 (enam) desa dalam wilayah Maluku Utara disebabkan karena adanya penolakan warga menjadi bagian dari Kecamatan dalam wilayah Kabupaten Halmahera Utara dan menginginkan tetap dalam wilayah Kabupaten Halmahera Barat. Pada kenyataannya terjadi dualisme pelayanan administrasi pemerintahan karena masing-masing Desa terdapat 2 (dua) orang Kepala Desa yakni versi pemerintah Halmahera Utara dan versi pemerintah Halmahera Barat. Berlaurutnya penyelesain sengketa berimplikasi pada penyelenggaraan Pemilihan Kepala Daerah dan Pemilu di wilayah tersebut. Penyelenggara Pemilu menetapkan Daftar Pemilih Tetap (DPT) warga 6 (enam) desa masuk dalam yurisdiksi Kabupaten Halmahera Utara. Sebagai bentuk protes, ribuan warga tidak menggunakan hak pilihnya pada Pemilu dan Pemilihan Kepala Daerah Tahun 2014 dan 2018. Undang-undang Pemilu dan Pilkada yang ada saat ini, belum mengatur secara eksplisit terkait jaminan perlindungan hak warga negara untuk memilih (right to vote) di wilayah sengketa batas akibat pemekaran wilayah. Kedepan perlu pengaturan khusus agar tidak ada warga negara yang kehilangan hak pilihnya karena persoalan teknis admnistrasi yang mengabaikan substansi berpemilu.
Side-to-side reverse superficial temporal artery to M4 middle cerebral artery bypass for common carotid artery occlusion with bonnet collaterals: illustrative case
Authors: Daggubati Lekhaj C. , Padmanaban Varun , Church Ephraim W.
Published: May 2021

BACKGROUND

The bonnet bypass was initially described for common carotid artery occlusion. Considered a second-generation bypass, it augments intracranial perfusion with contralateral external carotid artery flow through an interposition graft running over the scalp vertex. However, the traditional first-generation low-flow superficial temporal artery (STA)-M4 middle cerebral artery (MCA) bypass may be enhanced by performing a side-to-side (S-S) bypass with an intraluminal suture technique (fourth-generation bypass) to increase perfusion through antegrade and retrograde flow.

OBSERVATIONS

The authors present a reimagined S-S STA-M4 bypass in the case of a patient with symptomatic common carotid occlusion, in which the ipsilateral STA filled in a reverse fashion from the contralateral external carotid branches over the scalp vertex (bonnet collaterals). By performing an S-S anastomosis, the authors were able to improve cerebral perfusion and avoid the multiple anastomosis sites of the bonnet bypass.

LESSONS

The patient had a good recovery with resolution of his preoperative symptoms. Follow-up angiography showed a patent bypass supplying the MCA territory through retrograde flow in the frontal and parietal limbs of the STA, converging at the anastomosis site. In this report, the authors present a new fourth-generation bypass dubbed the “S-S reverse STA-M4 MCA bypass.”
Motivation: Up and down: Implementation of a motivational model and assessing the results
Authors: A. Potemkina Victoria , G. Sharshavina Svetlana
Published: May 2021

The opportunity to enroll in a foreign university skyrockets the motivation of many students. However, a huge number of these students eventually find themselves, in the midst of their studies, to unsure that they will even be able to graduate. This article focuses on the causes of demotivation for these students and aims to find a solution to this problem. Our study relies on previous research conducted by H. Douglas Brown, Zoltan Doernyei, Natalie Ness, Penny Ur, Desley I. Watson-Raston, and others. This article contributes to this literature by, first, looking into the causes of motivation loss among foreign students studying the English language in Russia, and second, by proposing certain tactics that could be put into practice in the classroom. By conducting our research over the last year and a half, we have come to several conclusions. According to our observations, authentic materials, along with the freedom for students to choose study topics and the way assignments are presented determinately increases not only student motivation but also improve learning results in speaking and writing. In our research, we tried to use a big variety of research methods. These included focus and control groups, general and individual questionnaires, video essays, and classic tests.