bluuebunny/crossref_metadata_2025 huggingface dataset:
Teachers' Experiences and Reflection on Social Networking Site: Application of Facebook on Students' Learning
Authors: Acharya Kamal Prasad , Acharya Milan
Published: September 2022

This paper explores the effect of the use of the social networking site 'Facebook' on students’ learning in public secondary schools in Nepal. It also examines the use of Facebook in teaching and learning to improve students’ academic performance. A mixed-method (QUAN-qual) research design with an opinionnaire survey tool was used to collect the quantitative data, whereas a semi-structured in-depth interview was used to collect qualitative data. One thousand teachers were selected randomly using the Raosoft sample size calculator with a 95% confidence level. The data from both these sources were analysed using SPSS software version 20 and thematically as well as verbatim methods. The study found that 69% of teachers used Facebook for other purposes than teaching and learning in public secondary schools. Also, 86% of teachers use Facebook during school hours which positively affects students’ academic performance. Based on this study, it is recommended that the use of Facebook need to be done only for academic purposes during school hours in the public secondary schools in Nepal.
Madhyama Pratipad: Nepal’s Middle Path Ambition through Non-alignment
Authors: Bhattarai Gaurav , Pulami Manish Jung
Published: September 2022

The geopolitical variable alone is not sufficient to understand Nepal’s entry into NAM and its relevance. While very little literature has been produced on Nepal’s non-alignment, what exists is also limited to either speeches or statements delivered by Nepali leaders at the conferences Non-Aligned Movement (NAM). Still, while scanning the perspective of Non-Nepali Cold War foreign policy analysts in the literature produced on Himalayan geopolitics, it can be clearly observed that Nepal’s voyage to non-alignment was driven by the Indian response to the bipolarity in Cold War. Such a perspective, however, dismisses the influence that MadhyamaPratipad (the concept of the middle path) had in the evolution of Nepal’s foreign policy priorities as a unified state in 1769. MadhyamaPratipad, here, should be understood as the cultural and civilizational philosophy, which Nepal has accommodated in its world view for centuries. Hence, Nepal’s shift to non-alignment was not abrupt and impulsive. Rather it was triggered by the MadhyamaPratipad, which was also realized by the founder of modern Nepal, Prithivi Narayan Shah. While non-alignment and MadhyamaPratipad differ in their approaches, their objectives remain the same: balancing. While non-alignment demands balancing by not being aligned to any security bloc, MadhyamaPratipad appeals to balancing by treading a middle path. Thus, this qualitative study argues how the historical experience of balancing made it easier for the Himalayan state to adapt to the non-aligned policy and posture. Accordingly, non-alignment to Nepal is not only a survival strategy but also a historical expression of its cultural and civilizational philosophy. Therefore, any attempt to understand Nepal’s foreign policy of non-alignment only from the grand narratives of geopolitics and changing dynamics in the regional and international security environment would not be sufficient to weigh the rationale and relevance of non-alignment for Nepal. Today, India’s perceptible shift to multi-alignment and China’s emphasis on the Xi Jinping Thought have already raised the question of the relevance of non-alignment for Nepal. The answers lie in Nepal’s historical experience of balancing.
Why is Nepal Politically so Unstable? Deconstructing the Instability Conundrum through Cross-Country Comparison
Authors: Aditya Anand
Published: September 2022

Not available.
Role of Remittances on Rural Poverty in Nepal-Evidence from Cross-Section Data
Authors: Byanjanakar Rohan , Shakha Mira
Published: September 2022

This paper attempts to determine the impact of remittance on rural poverty in Nepal using the microdata set of household risk and vulnerability survey 2016 – 2018. The cross-sectional analysis has been carried out using a dataset of 2018 with 5,645 households across 50 districts of Nepal. The logit regression model has been used to determine the relationship between poverty and remittances. About 38 percent of rural households received remittances in 2018. About 65 percent of households headed by females received remittance compared to 30 percent of households headed by male counterparts. About 41 percent, 31 percent, and 32 percent of households living in the Hilly region, Terai, and Himalayan region respectively received remittance in 2018. About 1 in every 5 households in rural Nepal is poor. The probability of households falling into poverty reduces by 4.8 percent with a one percent rise in household assets. Remittance receiving households are 2.3 percent less likely to get caught in poverty as compared to remittance non-receiving households. The probability of households plunging into poverty decreases by about 1.1 percent with every 10 percent increase in remittance inflows to households.
Remittances Economic Growth and Investment Nexus: Evidence From Nepal
Authors: Chaudhary Shashi Kant
Published: September 2022

This paper assesses the contribution of remittances on GDP and private gross fixed capital formation of Nepal by employing the ARDL bound test approach. The model incorporates the level of financial development, and the institutional quality of Nepal as regressors in addition to the macroeconomic regressors recognised by the literature. Perron’s (1997) innovation outlier model of breakpoint unit root test has been used to confirm the suitability of the variables in the ARDL bounds test approach. The findings show a positive effect of remittances on GDP while a negative effect on private gross fixed capital formation. The paper concludes that remittances do not act as a source of capital flows in the context of Nepal, rather they behave as compensatory transfers to the recipient households. To align remittances in productive activities such as self-employment, financial investment, etc., a remittance-focused policy is advised to reach out the recipients and provide them rigorous advisory and training supports.
Understanding the Processes of how Small and Medium Enterprises derive Value from Business Intelligence and Analytics
Authors: Wee Mak , Scheepers Helana , Tian Xuemei
Published: September 2022

This paper provides an in-depth study of how small and medium enterprises (SMEs) use business intelligence and analytics (BI&A) to derive business value and why so many SMEs fail to do so. A qualitative research approach based on semi-structured interviews with five SMEs in Australia was applied with the goal is to understand the process in which SMEs adopt BI&A to derive business value. This involved exploring how owners and managers lead their employees in using data and analytical processes to derive insights to make business decisions. The findings suggest that SMEs which adopt BI&A use a short and simple six-step iterative BI&A process to derive insights for business process application. In addition to the short process, a longer three phase process has been identified which progresses SMEs from solving operational issues to strategic challenges. The resulting short and long BI&A implementation process framework provides a progressive pathway for SME owners and managers to initiate and lead BI&A transformation in their SMEs to derive greater business value. The process model considers dimensions of data, analysis, business process change, social influence, level of information use and financial returns.
Elucidating the role of emotion in privacy-concerns: A text-Convolutional Neural Network (Text-CNN)-based tweets analysis of contact tracing apps
Authors: Mehta Mihir , De Sourya Joyee , Chattopadhyay Manojit
Published: September 2022

The extant contact tracing privacy literature is yet to explore the significance of user emotions in privacy-related decision-making such as whether to use such potentially privacy-invasive apps. Using social media analytics, the present study examines users’ privacy-related emotions stimulated by privacy-related aspects of contact tracing apps. A text-Convolutional Neural Network (Text-CNN)-based emotion analysis of tweets on the Indian contact tracing app Aarogya Setu and its Singaporean counterpart TraceTogether conducted in the paper reveals that users expressed negative privacy-related emotions towards these apps indicating high levels of perceived privacy risks and the perceived lack of privacy protection. For TraceTogether, users have also exhibited positive emotions to appreciate the steps taken by the government to protect their privacy. Based on these findings, the government/data controllers can devise strategies to assuage users’ negative emotions and promote positive emotions to encourage the adoption of contact tracing apps. This work incorporates privacy related emotions as key informants about user privacy concerns within the Privacy Calculus Theory. By relying on candid user opinions available through rich but inexpensive user-generated content, the research provides a quick, reliable, and cost-effective approach to study potential app users’ emotions to gain insights into privacy concerns related to any e-governance platform.
Leapfrogging into knowledge economy: Information and communication technology for human development
Authors: Verma Anushka , Giri Arun Kumar , Debata Byomakesh
Published: September 2022

Modern-day economic growth is focused on productivity and innovation, which puts information and technology integral to economic policy issues. In this context, ICT has a significant position as it increases efficiency, promotes information dissemination, and enhances innovation, resulting in a global shift in social and human development processes. The purpose of this research is to examine the significance of ICT diffusion in fostering human development in the South Asian Association for Regional Cooperation (SAARC) countries from 2005 to 2019. ICT diffusion is measured using a principal component analysis (PCA)- based composite index that combines telephone, mobile, broadband, and internet usage. The United Nations Development Programme (UNDP) created Human Development Index (HDI) serves as a proxy for human development. To adjust for any confounding bias, macroeconomic indicators, such as gross domestic product (GDP), inflation, and trade are also included. Utilizing econometric methods robust to cross-sectional dependence (CSD) such as the dynamic common correlated effect (DCCE) estimator, Driscoll-Kraay (DK) regression, and the Dumitrescu-Hurlin (DH) causality test, the study highlights the strong positive relationship between ICT and HDI. In addition, GDP boosts HDI owing to productivity gains. Similarly, trade expansion, in addition to its direct effects, also influences HDI by boosting economic growth. Inflation, on the other hand, has a negative impact on the HDI. Consequently, the study recommends a cohesive setting that unifies ICT with human development in this modern framework.
Prospects of Trademark Registration To Recover The Economic of MSMEs Actors in Service Sector after The Pandemic
Authors: Jaya Dedi , Disemadi Hari Sutra
Published: September 2022

MSMEs are businesses that can be run by all people who want to start a business with small capital. Q, MSMEs have strategic role in building Indonesian economy. However, the growth  of MSMEs is experiencing a slump due to COVID-19. On March 11, 2020, WHO as a legal world health organization declared the COVID-19 as a pandemic. MSMEs have become solution to increase the welfare of Indonesian citizen, since the issue of welfare itself is not an easy to realize. To support MSMEs in increasing the welfare, it is necessary for the government to take action in pushing MSME actors to registrate their trademarks as part of intellectual property which is very important in the economic recovery. Based on these problems, this study uses non-doctrinal research methods to examine trademark regulation in Indonesia, the awareness of MSME actors on the importance of trademark protection, and the relation of trademark registration as an effort to recover the MSME economy after the pandemic. The result of this study indicates that the regulation regarding trademark protection is contained in Indonesian Trademark & Geographical Indication Law.  Additionally,  the study reveals that there are several MSME actors who aware that a brand must be protected because it is an intellectual property, but there are also MSME actors who do not aware about this issue. In fact, the urgency of trademark registration is considered to be the part of efforts in recovering the economy of MSMEs after the COVID-19 pandemic, this is because after registering the trademark, it automatically has economic value.
Analisis Performansi Kriptografi Berbasis Algoritma Caesar Cipher dan Rail Fence Cipher pada Tembang Macapat
Authors: Purnamasari Dewi , Prasetyani Henny
Published: September 2022

Penerapan kriptografi pada asset budaya sangat perlu dilakukan, karena banyaknya klaim budaya Indonesia oleh negara asing. Oleh karena itu penelitian ini menggunakan tembang macapat Sinom, Pangkur, Pocung, Kinanti. Pada penelitian ini membandingkan algoritma Caesar Cipher dan Rail Fence Cipher untuk mengetahui proses penyandian dan efektifitas waktu enkripsi dan deskripsi. Waktu proses menunjukkan waktu deskripsi lebih lama dibandingkan enkripsi. Waktu rata-rata enkripsi algoritma Rail Fence Cipher lebih cepat yaitu adalah 0.000254 detik dibandingkan dengan Caesar. Waktu rata-rata enkripsi Rail Fence Cipher adalah 0.000254 detik dan waktu deskripsi adalah 0.000475 detik. Waktu enkripsi terpendek Pocung dan Kinanti. Rail Fence lebih aman dibanding Caesar Cipher.
Development of Cold Gas Sprayed Coatings
Authors: Voyer J. , Stoltenhoff T. , Kreye H.
Published: September 2022

By cold spraying, coatings are produced without significant heating of the spray powder and the substrate material. The powder particles are accelerated in a preheated gas stream to velocities of more than 500 m/s without melting and form a dense and tightly bonded coating. Bonding occurs only due to plastic deformation and the heat created thereby. Due to the absence of melting of the powder particles during cold spraying, several negative phenomenon, such as oxidation and phase transformations associated with thermal spray processes, such as HVOF, arc, flame and plasma spray can be minimized or avoided. This paper presents an overview of cold spray process developments and of coating characteristics. A variety of metallic powders having a low or high melting temperature including Cu, Al, Ti as well as alloys were sprayed onto different substrate materials, and the microstructure and properties of the coatings were evaluated.
Automated Cold Spray System: Description of Equipment and Performance Data
Authors: Blose R.E. , Roemer T.J. , Mayer A.J. , Beatty D.E. , Papyrin A.N.
Published: September 2022

Cold Spray is a rapidly emerging technology with numerous applications that have not yet been realized. With the growth of this technology there will be a demand for laboratory systems to perform applications research and development as well as high volume production machines for specific industrial applications. The recent focus of Cold Spray equipment development has been to perfect nozzles and gun assemblies, gas heaters, gas flow, powder feed, and process control. This paper describes the automated equipment that is available in the market and presents some performance data. This equipment will serve as the prototype for the industrial equipment that will soon be designed and installed in industry for commercial production applications.
Helium Recovery: Design Considerations for Cold Spray Systems
Authors: Lauricella Frank , Jaynes Scot
Published: September 2022

Experience with Cold Spray process requirements and equipment selection can impact process gas economics for Cold Spray systems. Cold Spray processes with helium, as the process gas, require helium recovery for optimized economics. In most cases, acceptable process economics require a helium recovery system to achieve greater than 95% overall recovery. Design of a helium recovery system with substantial overall helium recovery demands an understanding of the entire Cold Spray process and specifics about the product to be manufactured.
Intermediate Temperature SOFC Based on Fully Integrated Plasma Sprayed Components
Authors: Ma X.Q. , Hui S. , Zhang H. , Dai J. , Roth J. , Xiao T.D. , Reisner D.E.
Published: September 2022

This work addresses the fabrication of membrane-type SOFCs, operating at an intermediate temperature using all components fabricated by plasma spray technology, and to evaluate the performance of the SOFC single unit at a temperature range of 500-800 0C. Single cells composed of a LaSrMnO3 (“LSM”) cathode, LaSrGaMgO3 (“LSGM”) electrolyte and a Ni/YSZ anode, were fabricated in successive atmospheric plasma spraying processes. Plasma spraying processes have been optimized and tailored to each layer in order to achieve a high porosity cathode or anode layer as well as a high density electrolyte layer. Major effort has been devoted to the production of the LSGM electrolyte film with high density and free-cracking. Electrochemical impedance spectroscopy was used to investigate the conductivity of the electrode layers and particularly the resistance of the electrolyte layer. It was revealed that the heat treatment had a great influence on the specific conductivity of the sprayed electrolyte layer, and that the specific conductivity of the heat-treated one was dramatically increased to the same magnitude as that of a sintered LSGM pellet. The experimental results have demonstrated that the plasma spray process has great potential for the integrated fabrication of the medium temperature SOFC units.
Abrasion and Sliding Wear of Nanostructured Ceramic Coatings
Authors: Leblanc L.
Published: September 2022

PyroGenesis Inc. has been conducting a program on the development of coatings prepared from nanostructured ceramic and cermet materials using atmospheric (APS), vacuum plasma spraying (VPS), and high velocity oxy-fuel spraying (HVOF). In the work presented in this paper, APS and VPS coatings from nanostructured or sub-micron Al2O3- 13TiO2, Cr2O3-5SiO2-3TiO2, and TiO2 feedstock materials were developed and optimized for abrasion wear resistance. They were subsequently tested for sliding wear resistance. The resulting wear properties are discussed in terms of coating microstructure, and compared to those obtained from conventional microstructured feed materials. It is found that the starting powder and the spraying conditions play a major role in the resulting coating characteristics. VPS applied coatings from nanostructured powder were found to generally offer the best performance, most notably under sliding wear conditions.
Abrasion Wear Behaviour of Plasma and HVOF Sprayed Al2O3 SiC Nanocomposite Coatings
Authors: Dearnley P.A. , Panagopoulos K.
Published: September 2022

The present work describes abrasion wear tests that were carried out on low carbon steel test wheels coated with a series of plasma sprayed and HVOF sprayed Al2O3-SiC coatings with varying SiC contents. These were compared to a pure Al2O3 coating applied by HVOF and to uncoated steel. The HVOF sprayed coatings exhibited consistently superior abrasion wear resistance compared to plasma sprayed coatings of equivalent composition and uncoated steel. Overall, the HVOF Al2O3-10%SiC nanocomposite coating showed the best abrasion resistance of all the coatings tested. They were worn very slowly by a micro-abrasion process. The poor performance of the plasma sprayed coatings was attributed to a low cohesive strength which made them particularly vulnerable to grain pull-out.
Effect of Powder Composition on the Microstructure and Wear Properties of Sprayed Cast Iron Coatings
Authors: Morks M.F. , Shoeib M.A. , Tsunekawa Y. , Okumiya M.
Published: September 2022

Microstructure and properties of plasma sprayed cast iron coatings are closely linked to the spray conditions such as substrate temperature, chamber pressure, particle size, and spray distance. Another factor is the chemical composition of sprayed particles, which affects the physical properties such as density, viscosity, and thermal conductivity of droplets. In spraying cast iron on aluminum alloy substrate the purpose is to deposit a superior wear resistant coating as an approach to improve its wear resistance. Presence of graphite in cast iron increases the wear resistance of cast iron coating because of its self-lubricant property. Graphite grows during droplet solidification and splat cooling and thus its appearance is related to the solidification rate of the individual droplets. Alloying elements such as Al and Si in cast iron materials promote the graphite formation because they act as strong graphitizers probably by creation active nuclei for graphite growing. The aim of this paper is to examine the influence of powder chemical composition on the features and properties of sprayed cast iron splat and coating by spraying three cast iron powders of different chemical compositions on Al-Si-Cu alloy. The effect of powder chemical composition on graphite formation and microstructure was investigated. In addition, the mechanical properties such as friction, wear resistance, and microhardness of sprayed coatings with those powders were examined. The influence of chemical composition of sprayed powders on the microstructure of cast iron coatings was examined by X-ray and SEM.
A New Spray Coating Process for Manufacture of Stainless Steel Clad Construction Steel with Resistance to Corrosion by De-icing Salts & Seawater
Authors: Chesney Peter
Published: September 2022

The world’s first plant for manufacture of stainless steel clad structural steel is now operational in the USA. The process consists of coating round steel billets with a spray of stainless steel. A metallurgical bond is achieved so that the billets can be reheated and hot worked into long products while retaining the integrity of the coating. The process consists of teeming stainless steel from a ladle into a spray chamber and atomizing the emerging stream with jets of nitrogen to form a spray of semi-liquid particles. The spray is directed onto a 140mm diameter preheated carbon steel billet to form a thick coating (4 – 5mm). The spraying rate of 50Kg/minute produces clad billet at the rate of 15tonnes/hr. Billet is then hot rolled in a conventional bar mill to make corrosion resistant clad steel sections such as rebar and dowel pins. Coating thickness after rolling is in the range 0.5 – 1.0 mm depending on the final section. Clad products have a life expectancy of 75 – 100 years in high chloride environments such as tidal zones, bridge decks and highways treated with de-icing salts. The spray coating process is described together with mechanical properties of the clad bar and results of corrosion tests. The economics of stainless clad steels vs. other corrosion resistant materials are reviewed.
Marine Exposure Tests of Thermal Sprayed Coatings in Japan
Authors: Kuroda S. , Kawakita J. , Takemoto M. ,   Thermal Spray Committee
Published: September 2022

The thermal spray committee of the Japan Association of Corrosion Control (JACC) has been conducting a marine corrosion test of thermal sprayed Zn, Al and Zn-Al coatings since 1985. Twelve kinds of sprayed coating were deposited onto steel pipes by arc- and flame-spraying to varied thickness and subjected to various post-spray treatments. The samples were set vertically into seawater at a port 80 km south from Tokyo. Corrosion performance of these coatings has been inspected annually by recording the appearance and coatings’ thickness at sea air-, splash- and tidal-zones. No significant changes were observed for five years exposure. After 7 years, however, Zn coatings with and without sealing started to suffer degradation in the immersed portion. Contrary to this, Al and Zn-Al coatings still exhibit superb corrosion performance. The test will continue till 2006 to complete the test period of 20 years. In order to place the test into a proper perspective, we also conducted a survey on the corrosion prevention by thermal spray technology in 2001, collecting more than 170 published reports and asking experts to contribute reviews on various aspects of the technology. This paper first describes several topics from the survey report to explain the past and the present situation of thermal spraying for corrosion prevention in Japan. Then, the corrosion performance of sprayed coatings in the exposure test during 15 years will be summarized.
Optimization of Heat Transferring Components under Severe Wear Stress Conditions
Authors: Wielage B. , Wank A. , Reisel G. , Gross U. , Barth G.
Published: September 2022

There is a variety of components, which are subject to high wear and/or corrosion stress on the one hand and are used to transfer heat on the other hand. Two examples are drying cylinders in paper production and condensing boilers. Up to now there are no data available for the thermal design of thermal spray coated components except for some MCrAlY and thermal barrier coatings for turbine applications. Also guidelines for the optimization of thermally sprayed coatings concerning heat transfer including the effect on the wear resistance are missing. HVOF sprayed cermet coatings are widely used for combined wear and corrosion protection these days. In addition to WC-CoCr 86 - 10 4 and 75 Cr3C2 - 25 Ni20Cr conventional Ni5Al and Ni20Cr bond coats are evaluated concerning their thermal conductivity in the range between room temperature and 600 °C. Also the thermal contact resistance is determined depending on the substrate material: mild steel S355J2G3 (1.0570), grey cast iron GG25 (0.6025) and austenitic stainless steel X5CrNi18-10 (1.4301, AISI 304). The applied Laser- Flash method requires knowledge of the heat capacity, thermal expansion and density, which are determined before. HVOF spraying has only negligible influence on the heat capacity of WC-CoCr feedstock, as the temperature depending functions are almost identical. The use of spraying feedstock with average WC particle sizes of 800 nm, 3 µm and 5 µm permits to investigate the influence of the specific surface area of the hard phases both on the thermal conductivity and wear resistance. Furthermore the influence of the coating porosity is determined. In accordance to the drying cylinder application the wear resistance is determined by Taber-Abraser wear tests. Bond coats are produced by HVOF, HVCW and arc spraying and compared concerning microstructure and thermal conductivity. A comparison to the properties of electroplated hard chromium coatings is drawn.
Corrosion of WC-Co-Cr Cermet Coatings using In-Situ Atomic Force Microscopy
Authors: Souza V.A.D. , Neville A.
Published: September 2022

Most of the early applications of thermal spray coatings were focused towards providing a remedy to excessive wear degradation. However, as the introduction of such coatings into wider industrial sections increases there is also exposure to other potential degradation processes - aqueous corrosion is one such process. The complex microstructures in cermet coatings have been shown to translate to complex modes of corrosion attack. In this paper an electrochemical test methodology to probe the local/micro aspects of corrosion initiation and propagation will be described. A new electrochemical cell has been devised in which the corrosion can be followed `live` and in `real time`. The surface is subjected to in-situ imaging by Atomic Force Microscopy (AFM). This paper reports some of the exciting findings which have enabled the sequence of corrosion events in cermet coatings to be defined. The study has revealed that a precursor to coating degradation is the attack of the Co-base matrix. This sets up an environment which can catalyse WC dissolution. The practical and fundamental importance of the results will be discussed.
Relation Between Abrasive Wear and Microstructure of HVOF Cermet Coatings
Authors: Li C.-J. , Wang Y.-Y. , Ji G.-C. , Ohmori A.
Published: September 2022

HVOF cermet coatings have been widely used to improve the wear resistance. In the present study, an abrasive wear model is proposed according to the examination of wear mechanism. The relation between the relative abrasive wear and the size and content of carbide particles in cermet coating is established. HVOF WC-Co and Cr3C2-25NiCr coatings are deposited to correlate experimentally the relation between the carbide particle size and abrasive wear. The microstructure of coatings is examined using scanning electron microscopy (SEM). The carbide particle size in the coatings is measured according to SEM images of the coating. It has been found that experimental results correlate with the theoretical model well. The abrasive wear of HVOF carbide cermet coating is determined by carbide size and content. The relative abrasive wear resistance will be increased with an increase in carbide content and the decrease of square root of relative carbide particle size.
Plasma Sprayed Stainless Steel Coatings Doped with Graphite Particles : Study of their Dry Friction Coefficient Against 100C6 Steel Using a Pin on Disk Test
Authors: Harir A. , Ageorges H. , Grimaud A. , Fauchais P. , Platon F.
Published: September 2022

A new process has been developed to incorporate graphite particles in a stainless steel coating during its formation. Four means have been tested to inject the graphite particles outside the plasma jet and its plume : graphite suspension, a graphite rod rubbed on the rotating sample, powder injection close to the substrate with an injector or an especially designed guide. The latter process has been shown to be the most versatile and the best controllable one. It allows to incorporate uniformly between 2 and 12 vol % of graphite particles (2-15 µm) within the plasma sprayed stainless steel coatings. A 2 vol % seems to give the best results : a low decrease (6%) of the coating hardness and the best results in dry friction studied with a pin on disk set up. In this case, depending on the sliding velocity (0.1 to 0.5 m/s) and loads (3.7 to 28 N) the dry friction coefficient against a 100C6 pin is reduced by a factor between 1.5 and 4 compared to that obtained with plasma sprayed stainless steel.
Effect of Post-Treatment on the Corrosion Behaviour of HVOF-Stellite 6 Coatings
Authors: Malayoglu U. , Neville A. , De Wet D.
Published: September 2022

Coatings obtained by thermal spray techniques are widely used in many industrial applications where wear and abrasion resistance is required. High Velocity Oxy-Fuel (HVOF) spraying represents the state of the art of such types of coatings. The high velocity of the particles achieved during the spraying process and relatively low temperatures at the point of application enhance bond strength and eliminates substrate deformation by thermal effects. These aspects make the process attractive for high value components. In this work the electrochemical behaviour of both as-sprayed and HIPed Stellite 6 coatings are compared. Hot Isostatic Pressing (HIPing) consists of simultaneous applications of high pressure and high temperature. In this paper HIPing has been used as a post-treatment process for HVOF coating. Electrochemical DC anodic polarisation corrosion experiments were conducted in seawater at 18°C, 30°C, 40°C, 50°C, 70°C and 90°C. To support the electrochemical tests, detailed microscopy was conducted after corrosion tests to determine the attack mechanisms.
Steam Oxidation Resistance of HVOF Thermal Sprayed Ni-Cr Coatings
Authors: Sundararaian T. , Kuroda S. , Itagaki T. , Abe F.
Published: September 2022

HVOF coatings of 80Ni-20Cr and 50Ni-50Cr powders were carried out on 9Cr-1Mo steel substrate. The coating thickness was around 60 µm. The coated specimens were steam oxidized in four different temperatures, ranging from 600 to 750°C. The steam oxidized specimens were taken out from the chamber at 10, 100 and 1000 hours to examine their protectiveness against scale growth. X-ray diffraction, scanning electron microscope and electron probe microanalysis were carried out on the steam-oxidized specimens in reference with as-coated conditions. Both 80Ni- 20Cr and 50Ni-50Cr coatings show neither scale growth at the interface nor de-lamination in the coating structure. Fe, and Ni diffusion was found in the case of 80Ni-20Cr coatings. The diffusion increased with increase in the temperature and test duration. On the other hand, 50Ni-50Cr coatings, showed an excellent performance in all tested temperatures. The effect of Cr content in the coating, change in phase and compound formation during oxidation, and their influence on the diffusion process will be discussed in detail.
Low Friction Metallic Coatings for Reducing Railroad Squeal
Authors: Wei W. , Kootwijk P.A.A.
Published: September 2022

Squeal or screech continues to be a major noise pollution problem for rail systems in heavily populated areas. Squeal is a result of stick-slip phenomena in tight curves and switches at relatively low speeds, where the wheels "crab" through the turn. Current solutions for the problem have focused on lubricating the rails with a number of liquid systems including water and greases. However, commercially available systems have only shown mixed success, not only in terms of reducing squeal itself, but also from an economic and environmental standpoint.
Characterization of Coatings Deposited by Laser-Assisted Atmospheric Plasma Spraying
Authors: Zieris R. , Nowotny S. , Berger L.-M. , Haubold L. , Beyer E.
Published: September 2022

Laser-assisted atmospheric plasma spraying (LAAPS) is a newly developed one-step coating process in which the laser beam interacts simultaneously with the plasma torch on the substrate or deposited coating surface in order to generate the coating. LAAPS combines the advantages of plasma spraying, such as high coating rates, with those of laser cladding. In addition, there is no need for a special surface preparation method, such as grit blasting. In this paper, the principle of LAAPS is described and the use of this process for the preparation of NiCrBSi and Al2O3- 3%TiO2 coatings is demonstrated. The coatings were characterized by optical microscopy, hardness and bond strength testing, X-ray diffraction measurements, and an oscillating sliding wear test. Coating microstructures and properties were compared to those of APS coatings. The bond strengths of LAAPS coatings were higher for NiCrBSi coatings, but they were lower for Al2O3-3%TiO2 with a NiAl bond coat due to the very complex processes occurring in the contact region between the metallic substrate and the ceramic coating material.
On Vacuum Plasma Spray Forming of Ti-6Al-4V
Authors: Leblanc L. , Tsantrizos P. , Salimijazi H.R. , Coyle T.W. , Mostaghimi J.
Published: September 2022

The growing need for new materials and material combinations with superior properties for severe service applications has led to the development of near net-shape forming techniques for certain materials, such as superalloys, refractory metals and highly reactive metals, including Titanium and its alloys. In this work, the vacuum plasma spraying process (VPS) was optimized to prepare dense spray-formed components from high purity plasma atomized Ti-6Al-4V powder. VPS offers a unique environment for spraying reactive materials such as Ti- 6Al-4V as a controlled inert atmosphere is used during deposition of the material. Three particle size distributions of the powder were used to investigate the influence of the starting powder characteristics (size, chemical composition) on the resulting spray-formed material. Post-deposition heat-treatments were subsequently applied to modify the deposit structure in order to improve their mechanical properties. The as-deposited and post-treated specimens were characterized for their internal microstructure and mechanical properties. Results indicate that a combination of high purity starting powder, controlled environment, and tailored deposition and post-processing conditions can be used to produce dense spray-formed Ti-6Al-4V structures with properties comparable to those of cast and wrought materials. Yield strength in the order of 800 MPa, with ultimate tensile strength close to 900 MPa and elongation near 10% were measured for spray-formed and heat-treated Ti-6Al-4V specimens. The results of this investigation on vacuum plasma spray forming of Ti-6Al-4V are presented in a series of two papers. The first one (this one) focuses on the preparation of the spray-form components, and on the resulting mechanical characteristics. The second paper is dedicated to the detailed characterization of the internal microstructure of the as-sprayed and heat-treated deposits, and the correlation with the measured mechanical properties.
Investigation of the Influence of Post-Treatments on the Mechanical Properties of Coated Aluminium Foams
Authors: Maurer Matthias , Zhao Lidong , Lugscheider Erich
Published: September 2022

Beams of a hardenable aluminium foam were coated using electric arc spraying. AlSi6 and XCr13 were sprayed using compressed air or nitrogen. Subsequently the aluminium foam – coating - composites were post treated. The post treatment comprised of a heat treatment, suitable for hardening of the foam, grinding, shot-peening and / or sealing of the coating. Young’s moduli of the composites were non-destructively measured by resonant frequency. The dynamic properties of the composites were investigated by four-point-bending fatigue tests. The influence of the different post treatments on the bending stiffness and the fatigue behaviour was analysed using a statistical approach.
Determination of the Moving Velocity of Preheating Gun During Preheating/Spraying/Cooling Process by a Function Specification Method
Authors: Liao Hanlin , Deng Hao , Verdy Christophe , Coddet Christian
Published: September 2022

Disk-shaped splats that can be obtained on a heated substrate reveal a better contact with the substrate surface, resulting in a better adhesion/cohesion of coatings. Some research results illustrate that when the substrate temperature exceeds the transition temperature, the ideal splat can be obtained. In the simultaneous preheating-spraying-cooling process, named HEATCOOL in which a preheating gun heats the specimen just before the spraying and a cooling jet cools it just after the spraying, the preheating temperature is of short duration. In order to study the preheating effect and determine the optimal velocity of the movement of the system for obtaining an appropriate preheating temperature, the function specification method, an optimisation method, was adopted combined with FEM (the finite element method). An oxy-acetylene flame was used as preheating thermal resource, the optimal velocities were estimated. Particle impact tests of Cu and YSZ (ZrO2- 8%Y2O3) powders sprayed by plasma with a flame heating system were carried out with different moving velocities. The splats morphology collected on stainless steel and aluminium plates were observed to clarify and confirm the calculated results.
Plasma Sprayed Coatings Using Different Nanosize Alumina Powders
Authors: Zeng Yi , Ding Chuanxian , Lee Soowohn
Published: September 2022

Three kinds of nanostructured alumina coatings were prepared by air plasma spraying. As-sprayed coatings were characterized by SEM and XRD. Their surface roughness, porosity and microhardness were also examined. Results indicated that the smaller the size of the starting powders, the better the properties of the coating. The differences in the phase composition of the as-sprayed coatings could be used to explain the differences observed in coating properties.
New Composite Coatings on the Base of Recycled Hardmetals
Authors: Zimakov Sergei , Tarbe Riho , Kulu Priit
Published: September 2022

A new class of composite powders for thermal spray on the base of recycled hardmetal powder is proposed. WC-Co hardmetal powder that is either alloyed/mixed, coated, agglomerated or cladded with binder metal - cobalt enhances the technological properties of spraying powders and enables the producing of sprayed composite coatings with double-cemented structure. The manufacturing technology of WCCo/Co composite powders composed of mixing, agglomerating, sintering and crushing was studied and characteristics of the produced spray powders by particle size, morphology of particles and specific surface area were evaluated. The experiments for deposition of coatings by high velocity spraying processes (HVS), detonation gun (DG) spraying and High Velocity Oxy-Fuel (HVOF) spraying were carried out. Comparison abrasive erosion wear tests of sprayed coatings were performed.
Stainless Steel Coatings Alumina Reinforced by Plasma Spraying Mechanofused Particles
Authors: Cuenca-Alvarez R. , Ageorges H. , Fauchais P.
Published: September 2022

Stainless steel particles have been covered with an alumina shell by the mechanofusion process in order to reinforce stainless steel coatings by uniformly distributed alumina particles. Two stainless steel particle size distributions (PSD) in the range of 65 µm and 120 µm were tested. It was found that the mechanical energy input induced a spherical shape of the final composite particles with a controlled shell thickness (3 µm and 2 µm respectively) without forming new phases that usually take place during the mechanofusion process. The new spherically-shaped composite particles were sprayed in air with a D.C. plasma torch working with an Ar/H2 mixture as plasma forming gas. At mid-flight, two types of composite particles were detected : the first case corresponded to well molten particles where all the alumina shell has flowed to the tail of the particle ; the second case was related to particles which still retained some evidence of the alumina shell uniformly distributed around the stainless steel core. When the mechanofused particles were sprayed onto a cold smooth substrate (stainless steel 316L, Ra<0.05 µm), the resulting splats were extensively fingered and became disk shaped when the substrate surface was preheated over 300°C. However, alumina was either spread exactly on the stainless steel splat corresponding to well molten particles or dispersed in fingers and frozen over the surface of the stainless steel splat corresponding to particles covered by the broken alumina shell. An important effect of fine particle size on in-flight droplet behavior is detected because the center of gravity is more decentred than that of coarse particles influencing the deposit build-up. The composite stainless steel/alumina coatings sprayed on a rough stainless steel substrate (Ra = 6.7 ± 0.3 µm) preheated to 200 °C are compared to those of pure stainless steel. Hardness and adhesion/cohesion of deposits formed with fine particles were found to be improved comparatively to a pure stainless steel deposit. However, when coarse particles are used, the value of hardness is decreased and works is in progress to understand this phenomenon.
Standardization in Quality Control of Thermal Spray Coatings
Authors: van Wonderen M. , Sauer J.P.
Published: September 2022

The goal of this work is to have standardized quality control of thermal spray coatings incorporated into the Standard Practices Manuals of all aircraft engine original equipment manufacturer’s around the world. With the many manufacturers’ criteria for evaluation of thermal spray materials, laboratories are forced to have multiple criteria/systems to test and analyze coatings. As airlines/repair shops are moving towards overhaul of more variable engine types/models in their shops, the need to have a common evaluation system has been identified and is currently being addressed. A sub-committee of the European Airline Committee for Materials Technology is currently working to formulate this common system for thermal spray coatings evaluation. Participants are from GEAE, Pratt & Whitney, Rolls Royce, SNECMA and KLM Royal Dutch Airlines. The progress and goals of this group will be documented and reported.
Evaluation of HVOF Coatings for Wear Applications
Authors: Lima C.R.C. , Camargo F.
Published: September 2022

The use of coatings to improve wear and corrosion resistance of mechanical components has been common for several decades. Various application techniques have been commonly used, including welding, cladding, electroplating, PVD (physical vapor deposition) and CVD (chemical vapor deposition). Thermal spraying has been found to be an interesting and viable alternative for those processes in such applications. Coatings of several types can be used for wear and corrosion protection, including situations when they are combined. The analysis for choice of the ideal coating and of the application process should take into account the environment and related limitations and specificities of each coating material and application process. In this work a study and characterization of tungsten and chrome carbides based coatings was carried out. The coatings were applied by high velocity oxy fuel thermal spraying (HVOF), using two different HVOF systems. Microstructure, hardness, as well as wear characteristics of the coatings were evaluated. The results show that the obtained coatings present great characteristics and can successfully face several wear conditions.
Modelling and Design of an Attachment to the HVOF Gun
Authors: Dolatabadi A. , Pershin V. , Mostaghimi J.
Published: September 2022

Although the HVOF process has shown to be a technological alternative to the many conventional thermal spray processes, it would be very advantageous to design a nozzle that provides improved performance in the areas of deposition efficiency, particle in-flight oxidation, and flexibility to allow coating of ceramic powders. Based on a numerical analysis, a new nozzle was modeled, designed, tested, and used to produce thermal spray coatings according to the industrial needs mentioned above. Performance of the new nozzle was investigated by spraying several coating materials including metallic (Nickel, MCrAlY, Stainless Steel), carbide (WC-Co), and ceramic (Al2O3) powders. Particle spatial distribution, velocity, and temperature corresponding to the new nozzle and the standard HVOF gun were compared. The new nozzle provides a superior particle spatial distribution, as well as higher and more uniform particle velocity and temperature.
High Velocity Oxygen/Air Fuel Spray
Authors: Wang Hangong , Zha Bailin , Su Xunjia
Published: September 2022

According to aerodynamics and thermodynamics, High Velocity Oxygen/Air Fuel Spray system was successfully developed. The system introduced stream atomization, high-pressure combustion chamber, converging/diverging nozzle, spark plug ignition, radial powder injection with reliable operation. The system has the function of both of HVOF and HVAF. It can not only use air and oxygen to spray respectively, but also the mixture of air and oxygen, so the velocity and temperature of the flame can be changed by adjusting the flux of air and oxygen. The system can produce high quality cermets, metal and alloy coatings for the adjustable of flame velocity and temperature.