bluuebunny/crossref_metadata_2025 huggingface dataset:
SUBJECTIVITY AND OBJECTIVITY IN SOCIOGUMANITARIAN KNOWLEDGE
Authors:   Far Eastern State Transport University, Khabarovsk, Russia,, Zangirov Vladimir G.
Published: July 2022

The article presents the idea that the subject of socio-humanitarian cognition is human reality in the fullness of all its relations with the world. The fundamental form of these relations is the dialectic of subjectivity and objectivity, which manifests itself most vividly in the development of a person's life world.
Latent Profile Patterns of Affective Attitudes in Math and Science and Their Influential Factors for Elementary and Middle School Students in TIMSS 2019
Authors:   Korean Society for Educational Evaluation, Seo Minhee , Kim Kyunghee , Lee Bitna
Published: July 2022

According to the results of the international academic achievement assessment and previous studies, it is continuously reported that Korean students have high cognitive achievement but very low affective achievement. The purpose of this study is to explore the characteristics of the affective attitudes in math and science and to provide the implications for the improvement of students’ affective attitudes. To this end, multilevel latent profile analysis based on the 3-step method was used. We explored the latent profiles of the affective attitudes in math and science and their influential factors. We used data from 3,886 elementary school students(151 schools) and 3,857 middle school students(168 schools) who participated in TIMSS 2019. The results are as follows. First, for 4th graders, five latent profiles such as ‘negative(3.7%)’, ‘moderate(61.3%)’, ‘math positive(9.8%)’, ‘science positive(17.4%)’, and ‘very positive(7.8%)’ groups were derived. On the other hand, for 8th graders, the negative characteristics of each subject appeared(math negative(5.5.%), science negative(6.2%), moderate(72.2%), positive(11.3%), very positive(4.3%)). Second, in both grades, it was found that ‘sense of school belonging’, ‘instructional clarity’, and ‘solving math problems on your own’ were more related to the positive groups rather than the other groups. Third, for 4th graders, regional scale had an effect on the group classification. Lastly, educational implications for improving the affective attitude in math and science were proposed.
A Comparison of Item Selection Methods Using Response Times in Computerized Adaptive Testing
Authors:   Korean Society for Educational Evaluation, Kang Yulim , Lee Guemin
Published: July 2022

This study aimed to investigate the performance of item selection methods using response times (RT) in terms of the correlations between ability and test speededness and test lengths for computerized adaptive testing with fixed test time. MI, which does not use RT information, seems to estimate the ability parameters more accurately under a lenient time limit and a zero correlation between ability and test speededness condition. However, for MIT, which incorporates RT information in estimation and item selection procedures, the accuracy of ability estimates can be improved compared to MI and MITS as the correlation between ability and test speededness increases and the test length decreases. When item exposure control was applied, the measurement precision would be decreased. Compared to MI, MIT yielded a higher proportion of the number of items for a given test length. With relaxed limits in testing time, the effects of item exposure control on test efficiency would be decreased. Item selection with item exposure control can enhance item pool usage. After applying item exposure control, no significant differences could be expected in the item pool usage.
Asymptotic Standard Errors of IRT Linking Coefficients for the Bifactor Extension of the 3PL Model
Authors:   Korean Society for Educational Evaluation, Kim Seonghoon
Published: July 2022

The bifactor extension of the three-parameter logistic (B3PL) model has been used in applications of multidimensional item response theory (IRT) such as test equating and vertical scaling. Developing a common multidimensional IRT scale (that is, multidimensional coordinate system) is critical in those applications. Three common-item scale linking methods, the direct least squares (DLS), mean/least squares (MLS), and item response function (IRF) methods, for the B3PL model have been found to be effective in developing a common multidimensional IRT ability scale between two test forms to be linked. In this paper, the asymptotic standard errors (SEs) of IRT linking coefficients estimated by the DLS, MLS, and IRF methods are derived assuming that the B3PL model holds and the asymptotic variance-covariance matrix of item parameter estimates from separate calibrations is available. The delta method is used for the derivations. Computer simulations which investigate the accuracy of the derivations under various conditions are given, showing that the derivations are reasonably accurate when sufficiently large samples are used and that in general the SEs of the IRF method are smaller than those of the DLS and MLS methods. The simulation results also suggest that the SEs of linking coefficient estimates are, approximately, inversely proportional to the square root of the sample size when two test forms are administered to the same number of examinees.
Selection Neglect and Political Beliefs
Authors: Brundage Matthew , Little Andrew T. , You Soo Sun
Published: July 2022

Individuals, like researchers, often have to form beliefs about the political world from non-representative samples; e.g., their friends, what they see on TV, or content on social media. Substantial evidence indicates that many struggle to account for this selection problem, and generally form beliefs as if what they observe is representative. In this review, we provide a formal typology of how this phenomenon of selection neglect affects political beliefs. Homophily leads individuals to believe others’ traits and beliefs are closer to their own. The squeaky wheel effect biases beliefs towards more visible or vocal groups. And the man bites dog effect leads to excessive belief in extreme or unusual events. Selection neglect is a unifying way to understand disparate literatures on perceptions of the economy and demographics, beliefs about others beliefs, partisan media, and social media. Much empirical work is consistent with biased beliefs driven by selection neglect, but rarely directly tests this mechanism outside of lab settings. We discuss how future research can provide more direct evidence.
Are larger cities more central in urban networks: A meta-analysis
Authors: Li Xiaomeng , Neal Zachary P.
Published: July 2022

As cities develop more and longer-range external relations, some have challenged the long-standing notion that population size indicates a city's power in its urban system. Instead, they contend that cities' centrality within urban networks provides a better indicator of power. But are city population size and city network centrality really independent properties in practice, or do larger cities tend to be more central in urban networks? To answer this question, we conducted a systematic literature search and performed meta-analysis on 41 reported correlations between city size and degree centrality. The results show that population size and degree centrality are significantly and positively correlated for cities across various urban systems (r=0.77), but the correlation varies by network scale and type. The size-centrality association is weaker for global economic and transportation networks (r = 0.43), and stronger for non-global social and communication networks (r = 0.91). We conclude by discussing how this clarifies seemingly contradictory predictions in the literature regarding the association between size and centrality for cities.
Coefficient of accelerated expansion and the existence of Inverse Gravitational Fields
Authors: Gadda Navjot Singh
Published: July 2022

Two bound galaxies surrounded by a (nearly) empty vacuum which offers observable expansion of space via Repulsive Gravity.
Quick, eyes! Isolated upper face regions but not artificial features elicit rapid saccades
Authors: Broda Maximilian Davide , Haddad Theresa , de Haas Benjamin
Published: July 2022

Human faces elicit faster saccades than objects or animals, resonating with the great importance of faces for our species. The underlying mechanisms are largely unclear. Here we test two hypotheses based on previous findings. First, ultra-rapid saccades towards faces may not depend on the presence of the whole face, but the upper face halve containing the eye region. Second, ultra-rapid saccades towards faces (and possibly face parts) may emerge from our extensive experience with this stimulus and thus extend to glasses and masks - artificial features frequently encountered as part of a face. To test these hypotheses, we asked 43 participants to complete a saccadic choice task, which contrasted images of whole, upper and lower faces, face masks and glasses with car images. The resulting data confirmed ultra-rapid saccades for isolated upper face halves, but not for artificial facial features.
Thermally Sprayed Filler Metal Coatings for High Temperature Brazing
Authors: Bach Fr.-W. , Möhwald K. , Bach C. , Holländer U.
Published: July 2022

The use of modern thermal spraying techniques for filler metal application may offer new solutions for brazing complex metal components without fluxing agents, when the spraying processes are fitted to the requirements of the following brazing process. The necessary coating parameters always depend on the kind of base material, the geometry of the joint, the used filler metal, and the chosen heating process for brazing (heating in vacuum or protective atmosphere furnaces, inductive or flame heating etc.). Copper and nickel based alloys are typical filler metals for brazing complex components made of stainless steel (heat exchanger, fuel pipe systems, exhaust systems, catalytic devices etc.). Using these examples, the results of brazing experiments and technical aspects of thermally sprayed braze coatings compared with conventional filler metal application techniques are discussed.
The Current Situation and Future of Thermal Spraying Industry in China
Authors: Xiaoou Huang , Yufen Lu
Published: July 2022

The author carried out in 2003 a multiclient survey and research covering thermal spraying industry in China. This work mainly focus on the productive level and scale of thermal spraying equipment and materials, application and coating job shop, R&D in universities and institutes as well as the develop trends of thermal spraying industry in China. This presentation intends to provide general pictures on thermal spraying industry in China, by offering data and analysis, forecasts the future of thermal spraying in China.
DC and RF Plasma Processing for Fabrication of Solid Oxide Fuel Cells
Authors: Schiller Günter , Henne Rudolf , Lang Michael , Müller Matthias
Published: July 2022

Plasma deposition technologies are applied as an alternative approach to conventionally used sintering techniques for the fabrication of the entire cell assembly of solid oxide fuel cells (SOFC). Based on advanced processes with both DC and RF plasma DLR Stuttgart has developed a concept of a planar SOFC with consecutive deposition of all layers of a thin-film cell onto a metallic substrate support. The current state of the development of this “spray concept” which focuses on the application of SOFC as auxiliary power units (APU) for electric power supply in vehicles and aircrafts is summarized in this paper.
Low Pressure Plasma Spraying (LPPS) as a Tool for the Deposition of Functional SOFC Components
Authors: Refke A. , Barbezat G. , Hawley D. , Schmid R.K.
Published: July 2022

Plasma spraying at low pressure conditions (LPPS) is a well established thermal spray process with a broad variety of important applications in different industrial segments. The operating conditions for LPPS processes can vary in a wide range from only a few mbar up to typically 200 mbar which imposes different characteristics of the corresponding spray conditions and resulting coating properties. Thermal spray processes have been approved being suitable for integrated fabrication of various layers for SOFC components. Depending on the process conditions, different layers used as functional coatings of SOFC components such as dense electrolyte layers as well as porous electrodes can be realized using the LPPS technology. Due to the flexibility of these processes, an optimized performance of the application on different target materials and geometries is possible with an increased technological and economical benefit compared to conventional thermal spray techniques. This paper presents an overview on the general potential and spray conditions of the LPPS process and its application for the deposition of various functional layers such as electrolyte and electrodes for SOFC components.
Development of Plasma Sprayed Corrosion Protection Coatings for Sodium Sulfur Battery Cell Containers
Authors: Okuno A. , Harada Y. , Ando T.
Published: July 2022

A NAS battery cell is comprised of a sodium negative electrode and a sulfur positive electrode separated by a solid electrolyte made of beta-alumina, housed within a cylindrical aluminum container. The container is exposed highly corrosive materials, but have to be designed to deliver 4500 charge/ discharge cycles over a 15-year operating life. Studies have shown that a plasma sprayed Fe-75Cr alloy coating provides an effective protection layer. The major challenge to implementing this technology was the development of methods to apply plasma spray coatings in high volume mass production of the cells. This paper describes the development of high speed plasma spray guns optimized for volume manufacturing conditions, and the quality and reliability of NAS cells using this technology demonstrated over a period of nine years in laboratory tests. In April 2002 TEPCO and NGK decided to launch commercial production of NAS batteries. By April 2003, NGK started operation of a new NAS battery manufacturing facility and plasma sprayed aluminum cell containers are now being produced at a rate of over 1300 per day.
Thick Aluminum Coatings Using Axial Plasma Spray for Proton Beam Collimators
Authors: Mager J. , Burgess A. , Pavan R. , Orzechowski J.
Published: July 2022

Aluminum coatings minimum 1.8 mm thick are applied to water-cooled proton beam collimators used in the manufacture of medical isotopes on the TRIUMF TR30 cyclotrons in Vancouver, British Columbia, Canada. The sprayed surface of the collimators is made from silver. These collimators are used to trim the proton beam so that only a designated area on the isotope production target is irradiated with protons. Aluminum is used because its activation products at the energies used have short half-lives, thus minimizing the amount of collateral radioactivity produced. The aluminum is sprayed using an Axial III plasma spray torch. In service, the collimators are subject to high heat fluxes due to the proton beam. Service life, heat transfer and application data are provided in this paper.
Induction Plasma Spraying of Samaria Doped Ceria as Electrolyte for Solid Oxide Fuel Cells
Authors: Jia Lu
Published: July 2022

Samaria doped ceria (SDC), used as a solid oxide fuel cell (SOFC) electrolyte, was deposited by Solution Plasma Spray (SolPS) process. An aqueous solution of mixed nitrates was axially injected into the Radio Frequency (RF) inductively coupled plasma through an atomization probe. The atomic ratio of the SDC components in solution was (Ce0.85Sm0.15)O1.925. In order to control the initial spray droplet diameter, Malvern RTsizer atomization tests were performed. In-flight particle temperature and velocity were analyzed by DPV 2000. Coatings thickness and morphology were measured and observed by scanning electron microscopy, the substrate porosity being determined through gas permeability measurements. Results indicate that the coating's porosity and density strongly depend on the plasma spraying parameters. Gap size of the injection probe, atomization gas flow rate and the probe position have no significant effects on the coating’s porosity under the spraying conditions applied in this study
Research on Microstructure and Properties of Coating Produced by High Velocity Electric Wire Arc Spraying of TiB2/Al2O3 Cored Wire
Authors: Borchers Wang , Liuying Wang , Xunjia Su , Xuetao Zhang
Published: July 2022

In the paper, a newly composite TiB2/Al2O3 coating prepared by High Velocity Electric Wire Arc Spraying and cored wire with ceramic powders composed of refractory Al2O3 and TiB2 filling inside was introduced. The microstructure and composition of the TiB2/Al2O3 coating were investigated by metallgraphic microscope, scanning electron microscope and X-rayed diffraction, Bonding strength and hardness and mechanics properties were tested. The experimental results show the TiB2/Al2O3 composite coating possessed high hardness and higher bonding strength with substrate and excellent comprehensive mechanical properties. It can be used for improving shoot-proof properties in the surface of arms.
Latest Case Study and Subject of Thermal Spray Technology in Japan
Authors: Tani Kazumi , Nakahira Akira
Published: July 2022

The currently distinctive thermal spray applications in the surface modifying technology in Japan are introduced. Applying inventive combinations of coating materials and spraying processes have developed many unique applications. In terms of thermal spraying processes, in particular, low pressure plasma spray, atmospheric plasma spray, and high velocity oxy/fuel flame spray are employed. The profiles of industrial applications that are performed mainly by coating contract job shops are presented. For the typical coating materials, alumina, and zirconia as oxides, tungsten or chromium carbide cermet as composite materials, and special alloys were selected. The performance of coatings includes wide range field such as electrical insulation, erosion resistance, corrosion, wear resistance and so on. The current status of thermal spray market in Japan is also introduced.
Present Furnace and Pot Roll Coatings and Future Development
Authors: Fukubayashi Harold H.
Published: July 2022

In the recent past, automotive manufacturers worldwide started to demand sheet metals with very high surface quality, particularly those used in exposed panels. In order to meet this requirement the majority of strip producers started to use thermal spray coatings of one kind of another on essentially all the rolls in annealing, galvanizing, and other processing sections. In fact, no sheet for an exposed application can be produced without the use of roll coatings. Bridle and accumulator rolls in both entrance and exit ends of a galvanizing line are usually coated with tungsten or chromium carbide and/or oxide ceramic. These coatings prevent surface damage on the roll and provide proper friction/grip. In some cases, a properly textured coating provides the desired characteristics or profile on the strip surface. Coatings for furnace and hot tension bridle rolls prevent pickup due to slippage, iron fines, or an accidental change in the furnace atmosphere. The coating on pot and stabilizer rolls in a galvanizing pot prevents not only dross adhesion but also provides high enough friction to eliminate hydroplaning. Deflector or tower rolls are also coated with carbide or ceramic to minimize zinc pickup. The coating on rolls, in general, allows smooth operation of the line and produces an improved strip surface. At the same time, it allows an extension in service life, thus reducing frequency of maintenance shutdown. This paper attempts to review the present state of the art and predict future development.
Evaluation of Adhesive Strength of HVOF Sprayed Metallic Alloy Coatings by a Modified Tensile Test
Authors: Kuroda S. , Inoue T. , Kishi A. , Yokoyama K. , Yumoto H. , Gotoh Y.
Published: July 2022

A new method for evaluating the tensile adhesive strength of thermal sprayed coatings has been developed using a test specimen that incorporates an artificially introduced circumferential crack to control the stress intensity factor at the crack tip along the interface between the coating and the substrate. FEM-analysis is carried out to calculate a correction factor and the stress intensity factor for the test specimen. When the results of tensile test are sorted out using the stress intensity factor at which failure occurred, constant values should be obtained regardless of changes in geometry such as crack length and the diameter of test specimen. The method was first applied to air plasma spray (APS) coatings and then to HVOF sprayed coatings. Effects of substrate preparation such as surface roughness and preheating temperature on the resultant coating adhesion were studied experimentally.
Comprehensive Study of the Process-Property Correlations: Case Study for Molybdenum Coatings
Authors: Vaidya A. , Streibl T. , Li L. , Sampath S. , Gouldstone A. , Kovarik O. , Greenlaw R.
Published: July 2022

Thermal spray coatings exhibit a wide variety of microstructural characteristics that lead to variation in their functional properties. A complete understanding of the plasma spray process includes examination of the particle-flame interaction, particle impact (to form the splats), and the particle-substrate interaction during coating deposition. The links between these process parameters and coating properties has been established by using diagnostic tools in conjunction with a splat collection shutter and an in-situ curvature measurement instrument. In this study, a commercial grade molybdenum (Mo) powder was plasma sprayed; the spray stream was characterized in relation to the resulting particle state. A "splat map" was deposited through a "spray stream guillotine" to capture the fingerprint of the plume cross section. Subsequently, coatings were deposited at these spray conditions on a newly developed in-situ curvature measurement instrument to measure coating stresses and to estimate the coating modulus. Splats and coatings were subsequently characterized by micro-diffraction (for splat residual stresses), by nano and micro-indentation for elastic and elastic-plastic properties, and by electron microscopy. This complete history of the process followed by splat and coating characterization provides insight into the correlation between processing parameters, resultant particle states, and final coating properties. The role of particle temperature and velocity on the splat (and coating) morphology and residual stress is explained in the results.
Strain Tolerance Characterization for HVOF Coatings using the Acoustic Emission Tool
Authors: Bouaricha S. , Legoux J.-G.
Published: July 2022

The crack propagation characteristics obtained by observing the microstructure of bent coatings at different stages of applied strain were conducted. At the same time, acoustic emission (AE) features of released events were recorded. Generated cracks were found to emit weak acoustic emission events at the initiation (creation) of the crack at the coating surface, and then become strong releasing a uniform acoustic emission energy per event, when propagating transversally in the coating. However, cracks propagating at the interface with the substrate could generate both weak and strong events. It was also found that increasing the thickness of the coating leads to a decrease in the number of events and an increase of their released acoustic emission energy.
Deposition Efficiency and Microhardness of Plasma Sprayed Zirconia Coatings Using Different Powders as Feedstocks
Authors: Chen Huang , Choi Chul Ho , Lee Soo Wohn , Ding Chuan Xian
Published: July 2022

A typical feature of plasma sprayed zirconia-based coatings is that their depostion efficiencies are low. Thus, from the economic view of reducing cost, how to improve the depostion efficiency of plasma sprayed zirconia-based coatings is very important for practical application. In this paper, spray-dried nanostructured powders and conventional powders were used as feedstocks to deposit nanostructured and conventional zirconia coatings by atmospheric plasma spraying(APS). Deposition efficiencies for both nanostructured and conventional zirconia coatings deposited under different spraying parameters were comparatively measured. The obtained results revealed that the spray-dried nanostructured powders possessed higher deposition efficiency than that of conventional powders. In addition, it was found that spraying parameters had strongly influence on microstructure and microhardness of zirconia coatings. Therefore, in order to obtain high quality zirconia coating, proper spraying parameters must be considered.
Comparison of In-Flight Particle Characteristics and Coating Properties While Spraying NiCrBSi Powder with Different Spraying Processes
Authors: Planche M.P. , Liao H. , Coddet C.
Published: July 2022

The aim of this study was to compare different processes for a spraying NiCrBSi powder in order to understand how the coating properties are influenced by the particle characteristics. For that, three processes were tested: atmospheric plasma, HVOF and flame spraying. The plasma torch was a classical F4 gun from Sulzer-Metco, the HVOF gun was the CDS system manufactured by Sulzer-Metco and the flame spray gun was a Castolyn 8000 system. For each spraying process, the particles were analyzed using the DPV 2000 (Technar Ltd) at the distance corresponding to the coating build up. Particles velocity and temperature data were then correlated to the coating quality. Results indicate that the choice of the spraying technique induces important modifications in the coating properties in terms of adherence, porosity level, hardness and Young modulus. Changes in particle velocity and temperature are the key parameters determining the coating properties.
Evaluation of the Fracture Strength of Thermal Sprayed Coatings with Cracks
Authors: Kaneko K. , Ohmori A.
Published: July 2022

Fracture strength of a WC-12Co thermal sprayed coating is investigated experimentally and analytically. In the experiments, a pair of coated butt cylindrical specimens is subjected to combined tension with torsion stresses. Stress distributions in the coating at critical loading conditions are analyzed by using FEM analysis and the fracture criterion of the coating is investigated. It is found that normal stress distributions are common to all cases of testing stress conditions and so fracture condition of the brittle coating is represented as K ≧ Kcr in the normal stress distribution even under mixed deformation mode I and III. By using the experimental method presented in this paper and the corresponding FEM analysis, an approximation for the critical bonding strength of a coating under shearing load can be estimated.
Study on the Behavior of Arc-Spraying Coatings with High-Temperature Erosion Resistance
Authors: Liu Wei , Zeng Ke-li , Song Xi-jian , Wu Chaojun
Published: July 2022

Two cored wires L1 and L2, have been developed to produce arc-spraying coatings for treating high temperature erosion wear of four tubes in the power station, grit erosion experiments under various conditions such as temperature, incident angle, grit weight and shocking velocity have been taken, results show that coating L1 prepared by the new cored wire is more erosion resistance than the comparative materials 20g steel, coating L2 has different behavior varies with the distinct state, from the basis of surface structure and erosion performance, it is also concluded that coating L1 and L2 show mainly plastic erosion wear behavior during the grit erosion process.
Microstructure and Properties of FeNb and FeSi Coatings Obtained by HVOF Thermal Spraying
Authors: Cherigui M. , Fenineche N.E. , Coddet C. , Craven J.
Published: July 2022

Iron-based alloys were sprayed on a copper substrate using high velocity oxy-fuel process to form amorphous coatings. Two modes of cooling were used, water and air, in order to increase the particles speed solidification. Structures and magnetic properties of FeNb and FeSi deposits have been characterized. X-ray diffraction patterns showed that FeNb coatings present a partially amorphous structure, however, in the case of FeSi alloys, their structure is completely crystalline. The use of the two modes of cooling has given almost the same results for the two types of powders. As a consequence, magnetic properties of this material could be improved by using a heat treatment.
Development of Ferrous Powder Thermal Spray Coatings on Cylnder Bore in Diesel Engine
Authors: Uozato S. , Nakata K. , Ushio M.
Published: July 2022

Aluminum alloy has been gradually utilized in cylinder block instead of ferrous casting material for weight reduction in automobile industry these days. In order to acquire more weight reduction, a new liner-less technology - without cast iron liner used - is putting into practice in the fields of aluminum cylinder block and the target is for diesel engine. However, diesel fuel's impurity "sulfur" element and corrosive attack risk, such as sulfuric acid generated to the surface of liner is higher than gasoline fuel. Because of such disadvantage, wear and corrosion resistances applied to the inner cylinder-bore are required in order to achieve this liner-less aluminum cylinder block. This research is intended to accomplish both wear and corrosion performances using plasma thermal spray technology and to verify the feasibility of application to actual engine bore. A newly-developed ferrous powder (Fe-C-Ni-Cr-Cu-V-B alloy) revealed extremely excellent corrosion and wear resistances, compared with currently used bulk casting materials such as Fe-C-Si-B alloy and Fe-C-Si-Mo-B alloy for cylinder liner. For the last time, the new ferrous alloy powder was applied to actual engine bore by using Rota-Plasma spray coating. The experimental results with engine bore presented potential equivalent to current engine bore.
High Performance Coatings Produced by Internal Plasma Spraying on Engine Blocks of New Generation
Authors: Barbezat G.
Published: July 2022

Since about the year 2000, cast aluminum automobile engine blocks have been coated in production lines using internal plasma spraying technology. Using this approach, the coefficient of friction between the cylinder wall and the piston assembly can be reduced to 30% and oil consumption is reduced of a factor two in comparison with cast iron. The extremely low wear rate of the friction elements increases engine life and reduces maintenance costs. The fuel consumption of the cars can be reduced from 2 to 4% in the case of gasoline and diesel engines. The coating costs are strongly dependent on production volume. For high volume production, the costs can be similar to those for cast iron liners. This paper reviews results from laboratory and field tests evaluating the performance and cost efficiency of plasma sprayed engine block liners.
Cast Iron Coatings Containing Graphite Structure by Atmospheric Plasma Spraying
Authors: Ozdemir I. , Ueno T. , Tsunekawa Y. , Okumiya M.
Published: July 2022

The excellent wear-resistant performance of cast iron coatings considerably depends on the formation of graphite structure with an inherent self-lubricating property. In the present study, two types of cast iron powders produced by gas- (GA) and water-atomization (WA) were deposited on an aluminium alloy substrate by atmospheric DC plasma spraying. WA powders are generally characterized by high oxygen content, irregular appearance and inexpensiveness compared with those of GA powders. Although alloying elements of silicon and aluminium work as a strong graphitizer and anti-oxidizer, graphite structures are not recognized in coatings sprayed with as-atomized high silicon and aluminium powders. Therefore, either pre-annealing of powders or post-annealing of coatings is required to achieve cast iron coatings containing graphite structure. A marked decrease in graphite occurs to the coatings with pre-annealed GA powder, since there exists precipitated graphite mainly on a GA powder surface. A short period of post-annealing is also valuable for graphitization. The weak oxide layers are observed in coating cross-sections with GA and WA powder, however, their oxidized levels are much lower than those with bearing steel powder containing low silicon and aluminium. Hence, graphitized cast iron coatings sprayed with inexpensive WA powder exhibit a splendid anti-wear performance.
Formation of TiO2 Photocatalyst Through Cold Spraying
Authors: Li Chang-Jiu , Yang Guan-Jun , Huang Xin-Chun , Li Wen-Ya , Ohmori Akira
Published: July 2022

TiO2 photocatalyst in the form of coatings are of many advantages over those in powder form in practical applications. Various processes have been used to form TiO2 coatings including sputtering, Sol-Gel, vapor deposition, thermal spraying, etc. In all those processes, the coatings are deposited under temperatures from 300 to more than 2000 °C. High temperature during those processing may change the microstructure of the as-received TiO2 to a less effective one for photocataltyic performance. In the present study, TiO2 coating was deposited through cold spraying process using two types of powders, which were agglomerated with anatase ultra-fine particles in micro-size and nano-size. Microstructures of both powders and deposited coatings were characterized using X-ray diffraction and scanning electron microscopy. The photocatalytic performance was examined through acetaldehyde degradation under ultraviolet illumination. The results showed that the nanostructured TiO2 coatings were evenly deposited on stainless steel substrate through cold spraying. The thickness of the deposits reached up to 15 µm. The coating presented a rough surface and porous structure. Owing to the low temperature of spray powders, no change occurred to the phase and grain size of TiO2 during deposition process. It was also found that the cold sprayed TiO2 deposits were photocatalytically active for photodegradation of acetaldehyde.
Study of Aluminum Bronze Coating By Cold Spray Process
Authors: Xiong Tianying , Gu Chunlei , Zhang Weiqiang , Wu MinJie , Wu Jie , Jin Huazi , Li Tiefan
Published: July 2022

Cold spray is a promising potential material deposition process of which the main advantage is that the material to be sprayed is not heated to high temperatures. But one problem encountered is that the coatings for some powders are not well bonded to the substrate. The mechanisms of bonding of cold-sprayed coating to substrates are not at present clearly understood. This work considers the deposition of aluminum bronze by cold spray process onto stainless steel. The micro diffusion along the interface between the substrate and coating as well as the beta-phase depletion of the cold-sprayed coating is observed. Results obtained are important not only for understanding the interaction of the particles with the substrate but also for optimizing the spray parameters for the cold spray process.
Deposition of Copper by Cold Gas Dynamic Spraying: an Investigation of Dependence of Microstructure and Properties of the Deposits on the Spraying Conditions
Authors: Calla E. , McCartney D.G. , Shipway P.H.
Published: July 2022

In the Cold Gas Dynamic Spray (CGDS) process, coatings are deposited by the virtue of the high particle velocity achieved by the use of converging-diverging (de Laval) nozzle along with suitable particle characteristics and process parameters. In this study copper coatings were deposited on aluminium substrates using helium as the accelerating gas. The influence of the CGDS conditions, primarily driving gas temperature and pressure, on the nature of the deposited coatings and the deposition efficiency of the process were investigated. The results indicate that it is possible to deposit copper coatings at a wide range of process conditions, with successful deposition being observed with the driving gas at room temperature and 11 bar pressure (a condition where the nozzle is still choked). However, the nature of the coatings is strongly dependent upon the processing conditions. With room temperature driving gas, an increase in pressure lead to an increase in deposition efficiency, and increase in substrate deformation and an increase in microhardness in the deposit due to higher levels of work hardening. The use of driving gas at temperatures as low as 473 K resulted in recrystallisation in the deposit and a decrease in tendency to debond due to stress relief during recrystallisation. Recrystallisation also manifested itself in reduced hardness. The sensitivity of the recrystallisation conditions to the traverse speed of the jet over the substrate indicated that these processes are initiated by the impingement of the hot gas jet onto the deposit following deposition and not by changes in velocity or temperature of the particles upon impact.
Characterization of Microstructure of Nanostructured Fe-Si Coating Deposited by Cold Spraying
Authors: Li Chang-Jiu , Li Wen-Ya , Ma Wen-Hua , Fukanuma H.
Published: July 2022

The low temperature characteristic of cold spraying makes it possible to deposit the coating of temperature sensitive materials, such as nanostructured material, without any significant change in the microstructure of feedstock. In the present study, the Fe and Si powders of particle size less than 75 µm were mixed at a composition of 10wt%Si and ball-milled to produce the nanostructured feedstock. Cold spraying process was used to deposit coating with nitrogen as a driving gas at different temperatures. The microstructure of the as-sprayed nanostructured Fe-Si coating was characterized using optical microscopy, scanning electron microscopy and transmission electron microscopy (TEM). The grain sizes of the feedstock and as-sprayed coating were estimated based on X-ray diffraction analysis. The results showed that the nanostructured Fe-Si coating can be deposited by cold spraying using the ball-milled powders as feedstock. The as-sprayed coating presented a dense microstructure. The average grain size of the as-sprayed coating was comparable to that of the corresponding milled feedstock. No significant effect of the temperature of driving gas on the microstructure of cold-sprayed nanostructured Fe-Si coating was recognized. Moreover, TEM analysis showed that the amorphous phase was present in the as-milled powders and the as-sprayed coating along with the nanocrystalline.
Deposition of Amorphous Metallic Coatings by Thermal Spraying
Authors: Rohan P. , Bouaricha S. , Legoux J.-G. , Moreau C. , Ctibor P. , Nourouzi S. , Vardelle A.
Published: July 2022

Amorphous metallic coatings are of high interest because of their good wear and corrosion resistance as well as their high hardness and toughness relative to the crystalline alloys with the same composition. Thermal spray that makes it possible to reach quenching rates in the order of 106-107 K/s, has the ability to deposit coatings with a high content of amorphous phase. However, very few studies dealt with the understanding of the spraying factors that affect the formation of the amorphous phase under thermal spray conditions. In this work, the relationship between temperature and velocity of the spray particles and coating characteristics is investigated. Special attention is given to the degree of amorphisation of the as-sprayed coatings. The latter were produced both by plasma and wire-arc spraying in order to get a larger range of particle parameters at impact and different particle heating history in the gas flow before impingement onto the substrate. A commercial iron-based alloy available both in powder and wire forms was used. Microstructural analyses show that the as-sprayed coatings are partially amorphous and that the proportion of the amorphous phases depends on the sizes of the sprayed particles as they control the heating and acceleration of particles in the gas flow and their cooling rate on the substrate.
Plasma Sprayed Coatings from Powders of Alloyed Cast Iron Mill Debris
Authors: Kharlamov Y.A. , Budagyanch N.A. , Shevchenko A.V.
Published: July 2022

Manufacturing of alloyed cast iron forming rolls is accompanied by generation of valuable solid waste as cutting and grinding swarf. The objective of this investigation was to evaluate the potential for mill debris to be used as a new source of inexpensive powders for thermal spraying of wear resistant coatings. More than 25 high-carbon iron alloy compositions are used in roll production. The structure of these cast irons usually includes from 2 to 4 phases (such as troostite, bainite, needled martensite, austenite, and graphite). The properties of powders obtained from mill debris were characterized in terms of particle size and shape, composition, structure, technological fluidity, and bulk density. The obtained powders were used for plasma spraying of wear resistant coatings. The results indicate that cutting and grinding swarf may be a feasible raw material source for economical alloyed powders, granules, and other materials for coatings. The composite plasma sprayed coatings obtained from powder mixtures of alloyed cast iron and nickel-base alloy have better tribological performance in comparison to coatings from any single powder alloy.
A Comparative Diagnostic Analysis of Morphologically Different YSZ powders
Authors: Vaidya A. , Streibl T. , Sampath S. , Zhang H.
Published: July 2022

A wide range of manufacturing processes are used to supply yttria stabilized zirconia powders for plasma sprayed TBC applications. From previous studies it is known that the difference in coating properties can potentially result from variations in powder feedstock as a consequence of particle inflight behavior and particle impact. An additional strong contribution to splat variation results from changes in the particle in flight behavior. In order to understand the variation in particle condition as a consequence of different powder morphologies, a detailed diagnostic analysis was carried out for plasma densified (PD), fused and crushed (FC) and agglomerated & sintered (A&S) powders. In this study a “3D multiple sensors” based integrated approach was used to evaluate these differences. Direct feed back sensors were used for optimization and combined with sophisticated diagnostics for in-depth studies. To obtain comparable results, three batches of commercial powders were sized to the same specification. For a given set of spraying parameters the recorded spray stream characteristics such as plume position, particle temperature, size and velocity deviated strongly for the given morphologies. By optimizing injection, the different powders can be made to follow nominally similar trajectories. This study reveals the sensitivity of each powder to process parameters and the variability in particle state that can result from it. Some techniques are suggested to optimally inject the different powders and to achieve similar particle states for these morphologies
Vibrational Corrosion Potential of HastelloyC Coatings by GS-HVOF Spraying
Authors: Kawakita J. , Kuroda S. , Fukushima T. , Kodama T.
Published: July 2022

Coatings of HastelloyC fabricated by HVOF spraying with a gas shroud (GS) have shown the superior barrier characteristic and corrosion resistance in seawater environment. During immersion of these coatings in artificial seawater, however, vibrational behaviour of the corrosion potential was observed. Some types of surface modification of the sprayed coatings and changing of the spray condition were carried out and their effect on the corrosion potential was investigated. It was revealed that the vibration is related to surface oxides formed during the spray process. Surface modification of the sprayed coatings and changing of the spray condition could reduce the vibration effectively.
Corrosion Protection of a Metal Spray Coating by Using an Inorganic Sealing Agent for Its Micropores
Authors: Kanematsu Hideyuki , Barry Dana M. , McGrath Paul , Ohmori Akira
Published: July 2022

An investigation has been carried out to determine the corrosion protection that an inorganic sealing agent provides for micropores of spray coating films. The sealing agent used is composed of silicate compounds and easily penetrates the micropores of spray coating films. Generally speaking, its stability under ultraviolet light is much higher than any organic sealing agents available. In this study, the sealing capability of the inorganic agent was tested using several kinds of spray-coated specimens. In addition, observations were made about the anticorrosion characteristics of these sealed specimens. The samples used for this study were Zn/Al spray coated steel and pure aluminum spray coated steel. The inorganic silicate-sealing agent was applied to all of the specimens. However, some of them were ground until the sealing agent was completely removed from the surface of the specimens. For the latter case, the silicate-sealing agent remained only in the micropores of the spray-coated films. These specimens were observed by SEM-EDX to observe the sealing condition. Their corrosion characteristics were also observed by performing a CASS test. Using these results, we were able to evaluate the sealing agent’s protective capability for spray coatings.
Oxidation Behaviour of Molybdenum Disilicide Coatings at 1500 °C
Authors: Wielage B. , Reisel G. , Wank A. , Fritsche G.
Published: July 2022

Molybdenum disilicide (MoSi2) is a suitable material for high temperature applications especially because of its excellent high temperature oxidation resistance. For several high temperature applications MoSi2 shows high potential to be used as a protective coating. The oxidation behaviour of HVOF sprayed MoSi2 coatings is studied at 1500 °C. The oxidation tests are carried out in a simultaneous thermogravimetric device and the mass change is measured in dependence on the oxidation time. The microstructure of the coatings before and after oxidation is examined by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXS). The mass of the coating increases according to a parabolic function. During the oxidation test the microstructure changes significantly from a typical thermal spray coating microstructure with lamellae, pores and a phase mixture of MoSi2 and Mo5Si3 to a two phase system with sharply separated grain boundaries. On the surface of the coating a silicon dioxide layer with a thickness of less than 10 µm is formed.
Restricted Oxidation of HVOF Sprayed Deposits by Composition Control of Combustion Gas
Authors: Kawakita J. , Kuroda S.
Published: July 2022

Improved HVOF spraying with a gas shroud has been developed to fabricate environmental barrier coatings of corrosion resistant alloys such as HastelloyC. For such coatings, control of oxidation of the powder material during spraying is very important and the gas shroud has been effective to lower oxygen content to 0.19mass%. In the present study, further reduction of oxygen content to 0.063mass% was achieved by changing the composition of combustion gas by introducing nitrogen into the combustion chamber. This value is almost comparable to the oxygen content 0.042mass% of the feedstock powder but the porosity of the coating increased. Introduction of nitrogen to the combustion chamber lowered the temperature of the spray particles in flight while maintaining their high velocity. Another coating with 0.14mass% was obtained with open porosity below 0.1vol% by changing the mixing ratio of nitrogen, which exhibited improved environmental barrier property in artificial seawater.