bluuebunny/crossref_metadata_2025 huggingface dataset:
Teachers' Perceptions of Student's Weaknesses While Scoring Answer Sheets
Authors: Sherpa Dawa , Baraily Khagendra
Published: September 2022

This paper aims to explore the perceptions of examiners in examining bachelor's level answer sheets. This study was carried out by adopting the hermeneutic phenomenological method under a qualitative research design. The participant of the study were five teachers from the constituent campuses of Tribhuvan University.This study explored whether students mismatched the answer numbers, such as writing the incorrect answer or writing an irrelevant answer. Unpreparedness about curriculum content and writing inappropriate answers with verbal repertoire is a common problems. Most of the answer sheets were found to be lacking in managing the time while writing the answers. Furthermore, students were found poor at structuring answers and wrapping them with appropriate remarks. The study findings can contribute to the test construction, test administration, and refinement of a student's writing with relevant content and demand for the questions.
Sphere pressure: When Politics Contends with Geopolitics
Authors: Upadhyaya Sanjay
Published: September 2022

Nepal’s strategic vulnerability owing to its location between two giants of Asia has risen and fallen with the status of India and China relations, the quality of their bilateral relations, and the principal external variables influencing them. In recent years, Nepal’s boisterous domestic politics has emerged as an additional source of instability. In the past, the internal fundamentals, regardless of the political system of the day, were sturdy enough to cope with often-competing pressures emanating from the north and south. The improvisation that has become the defining feature of the contemporary Nepali state, has made today’s geopolitical spasms far more ominous. While it may be outlandish to suggest that Nepal’s politics and geopolitics have become antithetical, there is sufficient basis for probing that question.
Understanding Nepal’s Geopolitical Dynamics: Connected History Disconnected Future
Authors: Bhatta Chandra Dev
Published: September 2022

The debate on geopolitics has gained momentum at various layers of society in recent years. Yet, there is paucity in clarity as to what geopolitics entails and how Nepal has become geopolitically important. There are, however, multiple opinions, where the tendency has been to project geography as the main tenet of geopolitics. This may partially be true given the changes brought about by the new technology-driven political economy. Likewise, there is a tendency to associate every success and failure in the domestic politics/development with geopolitics, while other undercurrents are not taken into consideration even though they might have implications for keeping the society and state together in the long-term. What is still important for the states like Nepal is the role of powerful countries both in the neighborhood and beyond. Geopolitics certainly is not new, but its manifestations may differ, and this article looks into them and their possible consequences for Nepal. In this regard  shall also carefully considers how foreign policy should be articulated when geopolitics is entrenched. The article largely builds on an analytical approach based on certain facts/events to understand and explain the geopolitical underpinnings.
Geopolitical Trends and Need for Coherent Foreign and Security Policy for Nepal
Authors: Sharma Suresh
Published: September 2022

Nepal faces a severe geopolitical threat because of the geostrategic position between India and China. This geographical positioning and the constantly changing geopolitical trends seriously impact the country. A comprehensive and coherent foreign and security policy is needed by Nepal to address the risks and threats. Realizing the evolving geopolitical effects on Nepal and the country needs to be ready with the foreign policy and security policy harmonize and coordinate the two to promote and protect the national interest. The study aims to point out the geopolitical threats for the country and recommends the fundamentals for developing a coherent and integrated foreign policy. To justify this necessity, the study explores the relationship between foreign policy and security policy and establishes an interdependent connection between the two. The article also traces the historiography of the harmonious and integrated foreign and security policy of Nepal from the nation-building phase. It identifies the situations in which the country had deviated from the core fundamentals of the foreign and security policies. Methodologically, the article has adhered to the secondary resources and has adopted a qualitative approach to collate and analyze the information thematically.
Rishikesh Shaha: A Historical Perspective
Authors: Acharya Jayaraj
Published: September 2022

We must reflect upon the historical background of Nepal’s foreign policy and diplomacy, particularly at the United Nations (UN), to properly understand RishikeshSahah (1925- 2002) as a diplomat and politician. Shaha’s main contribution of public interest is related mainly to his role as Nepal’s permanent representative at the United Nations. During the Rana period, Nepal had the policy of keeping the country isolated from the rest of the world for fear of meddling by the British. JangaBahadur, the first Rana Prime Minister, had himself led the troops to assist the British colonialists in India to quell the police munity of 1857 and firmly expressed his assurance that there was no need for them to enter Nepal for any reason as they could benefit from Nepal without the need to colonize the country. Both the Ranas and the British colonial rulers in India had a common interest in keeping Nepal isolated from others but in close contact with British India for their own reasons. It is said that Nepal lost a total of about 60,000 soldiers in World War I and II. But, even as a sovereign independent state, Nepal did not participate in the San Francisco conference in 1945 to draft the Charter of the United Nations although it could have legitimately participated and become one of the founding members of the world organization. It was a missed opportunity.
Role of Workers’ Remittances in Export Performance of Nepal: Gravity Modelling Approach
Authors: Paudel Ramesh Chandra , Bhusal Tara Prasad
Published: September 2022

Role of workers’ remittance seems to be an imperative part of Nepalese economy for about two decades. The remittances inflow has supported to maintain the foreign reserves at the national level and consumption in household level. This paper investigates the role of remittances in export performance of Nepal employing the gravity modelling approach using annual data for the period of 26 years, from year 1993 to 2018. First, we document the scenario of remittances and export nexus, then conduct an econometric estimation for the exports flows from Nepal to its trading partners. The major finding indicates that the remittances have a statistically significant negative impact on export performance, which is largely impacted by the size of the trading partner’s economy as indicated by the estimation’s results. The study suggests for an urgent attention from policy makers to make the remittance in favor of exports by developing the export strategies. In this regard, a special focus on exporting to the rich economies may be a good way to boost the export performance of Nepal.
Bank Stability and Its Determinants in The Nepalese Banking Industry
Authors: Singh Nirmal
Published: September 2022

This paper investigates bank stability and its bank-specific, industry-specific, macroeconomic and institutional determinants for the Nepalese banking industry. The study employs the system GMM to a panel of bank-level data covering the period from 2004-2018.  The results show that the stability of the Nepalese banking industry improved during the early years of the study period, i.e., 2004-2007; however, it exhibited a decaying trend for the rest of the study period. The analysis reveals that the major factors responsible for this deterioration are capital adequacy, asset quality, and earnings of the banks. Most of the dimensions have shown improvements during the initial years of the study period; however, this trend reversed post-2007.The study groups the banks into three categories: stable, moderately stable, and less stable banks as per their respective stability score. The estimation results indicate that a positive bank stability persistence exists in the Nepalese banking industry. Results suggest that credit growth has a negative impact on the stability of the banks. The results of the study support the concentration-stability hypothesis. Income diversification appears to have a positive impact on the stability of the banks. Findings disclose that inflation is playing a crucial role in impacting the stability of the banks. The study reveals that the GFC had no significant impact on the stability of the Nepalese banking industry.
Attraktive Lösungen für Open Educational Resources aus dem österreichischen Hochschulraum – ein Werkstattbericht von Open Education Austria Advanced
Authors: Hackl Claudia , Ebner Martin , Ganguly Raman , Gröblinger Ortrun , Handle-Pfeiffer Daniel , Kopp Michael , Schmölz Alexander , Schön Sandra , Zwiauer Charlotte
Published: September 2022

Open Education Austria Advanced ist ein Projekt mehrerer österreichischer Universitäten, das attraktive Lösungen für OER als Gesamtprojektziel verfolgt. Diese äußern sich im Rahmen eines OERhub (zentrale Meta-Suchmaschine für OER aus dem gesamten öst. Hochschulraum), dem Aufbau von lokalen OER-Repositorien und einer nationalen Zertifizierungsstelle mit passenden Qualifizierungsangeboten. Der weitreichende Wissenstransfer des Projekts in die österreichischen Hochschulen an der Schnittstelle von Bibliotheken, Zentralen IT-Services und Teaching & Learning Zentren trägt zur Sichtbarmachung und Nutzung von Synergien aus Open Science und Open Education bei, um einen Beitrag zur freien Nutzung von Bildungsinhalten aus der (Hochschul-)Lehre zu leisten und offene Praktiken analog zur Forschung zu etablieren (Open Access, Open Data).
Pentingnya pendaftaran tanah untuk pertama kali dalam rangka perlindungan hukum kepemilikan sertifikat tanah
Authors: Avivah Lisnadia Nur , Sutaryono Sutaryono , Andari Dwi Wulan Titik Andari
Published: September 2022

To ensure legal certainty of land rights, land registration activities are carried out which are a series of land administration activities in collecting and processing physical and juridical data. The purpose of this study is to analyze the importance of the first land registration. The research method uses a normative juridical with a statutory approach. The results of this study indicate that to increase public interest in registering their land is to socialize about the benefits of the importance of land registration held by the government and non-government institutions. The reluctance of the community to register their land is caused by their assumptions about several things, namely the difficult procedure, the high costs associated with the taxes paid, the registration process is long and tends to be considered convoluted. It is necessary to disseminate more complete, clear and massive information about the importance of guaranteeing legal certainty over land right.
Legalitas Komersialisasi Fanart Anime
Authors: Wijaya Jessy , Kornelis Yudi
Published: September 2022

The popularity of anime makes fans take an active role in their community, one of them is by commercializing anime fanart. The commercialization of anime fanart is rather an ambiguous problem, considering that there is no specific regulation about this matter, either in the Law No. 28 of 2014 on Copyright or Japan Copyright Act. The commercialization of anime fanart occurs because fan artists do not understand this matter. Anime fanart is a work produced by fan artist’s creativity with their own style as an element of originality and differentiating them from the original creator and other fan artist’s work, but on the other hand, anime fanart used pre-existing anime characters as their fanart inspiration. Fanart as a work that has elements of originality but not completely original make commercializing anime fanart an act that does not violate the rules. The purpose of this study is to compare the commercialization of anime fanart regulation between Indonesia and Japan. This study uses a normative juridical research method with a comparative law approach and a statute approach. The result of this study indicates that the commercialization of anime fanart has been implicitly regulated in Indonesia Copyright Act, as well as in Japan Copyright Act. In addition, Law No. 28 of 2014 on Copyright and Japan Copyright Act, both categorized the commercialization of anime fanart as an act of copyright infringement.
Perbuatan Makar di Indonesia: Kebijakan Hukum & Ketentuan Penyidikan
Authors: Winson Winson , Alhakim Abdurakhman
Published: September 2022

Indonesia is a state of law, as mandated in the Indonesian constitution. And also Indonesia is a democratic country that upholds the sovereignty of the people, this is certainly inseparable from the problems that then arise by the people and the sovereign government, namely an act which is then carried out by a person or group of people to overthrow the sovereign government or commonly known as a crime. treason. In Indonesia, the crime of treason is something that often happens considering that Indonesia is a democratic country. So the purpose of this research is to find out the provisions of the investigation of the perpetrators of the crime of treason in Indonesia and the policy of criminal law against the perpetrators of the crime of treason in Indonesia. This study uses a normative juridical research method. And it is known that the crime of treason in Indonesia has been explained in the Criminal Code, which in article 104 of the Criminal Code concerning treason, in this case, has an explanation related to the objective and subjective elements of an act of treason so that some provisions on the applicable criminal law policy, in this case, This can be used to adjust to the act of treason committed by the perpetrator.
Cold Spraying – Equipment and Application Trends
Authors: Kroemmer W. , Heinrich P. , Richter P.
Published: September 2022

With lightning speed, the thermal spray process cold spraying established itself as a viable coating technology. Due to such properties as dense, oxide-free coatings, a multitude of new applications now present themselves which, up to now, were not feasible using traditional processes. With the targeted and process-oriented groundwork of the competence group and the manufacturer of cold spray equipment, together with a gas company the equipment engineering for cold spraying has reached an extremely high technological level, facilitating an efficient operation with a tremendous process reliability. This work has, of course, involved extensive long-term testing of such components as the nozzle and gas heater. In the same way, by successfully adapting spray materials, cold spray coatings can now be applied in many new fields and technologies. Practical solutions are already available in the automotive and electronics industries. The constant encounter with new applications for which cold spraying can provide solutions, demonstrates that a new era of thermal spraying in all branches of industry has begun.
Thermal Spray Solutions For Diesel Engine Piston Rings
Authors: Herbst-Dederichs C.
Published: September 2022

Diesel engine development is continuously progressing: light vehicle diesel (LVD) engines are gaining in popularity in Europe and therefore we see a steady improvement in power performance and fuel consumption going along with increased loading of the power-cylinder components. Moreover, heavy-duty (HD) engines for trucks are facing stricter environmental legislation leading amongst other technologies to the introduction of exhaust gas recirculation (EGR). Whatever reduced emission technology will be applied, they all will significantly influence the engine tribology. This paper is dedicated to describing modern piston ring coating technologies to face the future diesel engine demands. The paper mainly focuses onto modern piston ring coating technology such as hard particle reinforced chrome plating, HVOF spraying and PVD. In particular, it will be discussed how thermal spray coatings need to be designed to find their position among established or future coating technologies of the competition.
Protection of Titanium Alloy Surfaces by Thermal Spraying and Laser Treatment
Authors: Wielage B. , Podlesak H. , Wank A. , Matthes K.-J. , Kolbe G. , Wilden J.
Published: September 2022

Titanium alloys are used in several fields due to their outstanding high specific strength, low density and excellent corrosion resistance, but the low wear resistance confines their applicability. The performance of CVD and PVD coatings is limited by the low hardness of the substrate, which cannot supply sufficient support, and conventional thermal spray coating materials do not provide the excellent corrosion properties. Laser alloying also often results in a decreased corrosion resistance and additionally in embrittlement. The use of boron for laser alloying or dispersing of diborides permits the incorporation of extremely hard boride phases without significant decrease of the matrix materials corrosion resistance and ductility, as there is no solubility of boron in titanium. Laser alloying with boron paste and dispersing of TiB2 in Ti6Al4V surfaces is carried out with CO2 lasers and an adapted inert gas shower apparatus. Typically a melt pool depth of 200 - 300 µm is achieved and the boride precipitates permit an increase of the surface hardness from 350 HV0.05 in the initial state to about 800 HV0.05. The surface area is characterized by means of optical microscopy, SEM and EDXS. Vacuum plasma spraying is used to provide a technology for deposition of TiB2 layers with defined thickness prior to laser treatment on surfaces with complex shape and in order to evaluate the direct applicability of thermally sprayed TiB2 coatings.
Photocatalytic Decomposition of Ammonia by Thermal Sprayed TiO2 Coatings
Authors: Ohmori A. , Nakade K. , Yamamoto Y.
Published: September 2022

TiO2 coatings were prepared by plasma and HVOF spray using agglomerated sub-micron TiO2 powder. Effects of various spray conditions on microstructure, phase ratio, coating thickness have been investigated and then photocatalytic properties was evaluated. It was found that anatase phase ratio decreased gradually with increasing arc current in the plasma spray process, while higher anatase ratio (approximately 50%) was obtained in the HVOF process. The coating thickness increased with increasing arc current and displayed approximately 50mm thickness in the case of 800A although anatase ratio was lower. Thus, the anatase phase ratio and coating thickness exhibited strong dependency on thermal spray method and spray conditions (arc current and fuel gas pressure). The sprayed coatings using sub-micron powder feed showed photo-catalytic decomposition of gaseous NH3. As a result of photo-catalytic experiments, TiO2 coating formed by HVOF spraying showed higher decomposition rate because coating by HVOF showed high anatase ratio. And, moreover, the TiO2 coating by plasma spray technique also exhibited photocatalytic decomposition of gaseous NH3 although anatase ratio was lower in comparison with HVOF in present study.
Methodology for Meeting Standards and Environmental Requirements in Thermal Spraying, Hardfacing and Sand Blasting
Authors: Ducos Maurice , Duchateau Daniel
Published: September 2022

This paper presents the bases of a methodology for purchase, installation and use of equipment for thermal spraying, hardfacing and sand blasting. This methodology takes all currently known personnel and environmental regulations into account. Businesses already using the above-mentioned techniques as well as future users will find it useful as it gives details about how to meet the current obligations and to correctly evaluate the resources needed to design not only efficient, but also safe and environment-friendly workshops. To be more user-friendly, the necessary information for setting up a complete installation can be structured and presented under the form of notices which could constitute the basis of a user’s guide.
New Carbide Based Materials for HVOF Spraying
Authors: Zimmermann S. , Keller H. , Schwier G.
Published: September 2022

Standard materials like WC-Co, WC-CoCr, WC-Ni, and Cr3C2- NiCr for HVOF spraying exist in various modifications depending on chemistry, carbide size, and production method. They are widely used for wear, erosion, cavitation, and corrosion protection in many industrial fields. But there are a lot of applications in which the surface is exposed to a combination of different wear mechanisms - e.g. corrosion and erosion or abrasion - and usual state-of-the-art coatings do not fully meet the technical demands regarding lifetime under those combined attacks. New materials therefore are needed. In the present study several modified and completely new carbide based materials are investigated. A series of new cermets differing regarding carbide type, carbide size, and metallic binders are compared. The materials were sprayed with the HVOF system DJ 2600 to show the influence of their different chemistry and morphology on the microstructure and properties of the coating in comparison to standard materials. The experiments comprises microstructural examinations as well as abrasive wear, corrosion, and cavitation tests.
Preparation and Characterization of Powders and Coatings Containing Solid Lubricants
Authors: Männikkö U. , Määttä A. , Vuoristo P. , Mäntylä T.
Published: September 2022

In this work, HVOF sprayed hard metal multi-component Cr3C2-25Ni+10 vol-% solid lubricant coatings were prepared by HVOF spraying. CaF2, BN, MnS and WS2 were used as solid lubricants. Powders were prepared by the spray drying and sintering method. This method produces homogeneous and spherical powders. Powders were sprayed with DJH 2600 HVOF-system. Microstructures, phase structures and compositions of powders and coatings were analysed with optical microscope, scanning electron microscope with EDS-analysator and x-ray diffractometer. The particle size distributions of sintered powders were determined by laser diffractometer. The amount of retained solid lubricant in the sprayed coatings was evaluated by EDS and compared to that in the spray powder. This study showed that spray drying and sintering method is a preferable method for manufacturing multi-component solid lubricant containing thermal spray powders. In sintering processes, solid lubricant phases remained in powders except for the Cr3C2-25Ni+10vol-%WS2-powder. Also, after HVOF spraying, coatings contained solid lubricants.
Properties of Plasma and D-Gun Sprayed Metal-Matrix-Composite (MMC) Coatings Based on Ceramic Hard Particle Reinforced Fe-, Ni-aluminide Matrix
Authors: Bach Fr.-W. , Babiak Z. , Rothardt T. , Formanek B.
Published: September 2022

Coatings of Metal-Matrix-Composite (MMC) with enhanced wear resistance were created by thermal spraying. The used powders composed of iron and nickel aluminides reinforced with alumina, Cr- and Ti-carbides were produced before by self-propagating high temperature synthesis (SHS). The fused and crushed composite powders were sprayed by atmosphere plasma spraying (APS) and gas detonation spraying (D-Gun). Spray powder and coating properties like morphology, structure, microhardness, porosity, bond strength, wear and corrosion resistance are examined using optical and scanning electron microscopy, XRD analysis, pin-on-disc (wear resistance). The produced MMC coatings are compared to commercially used wear resistant coatings, e.g. high velocity oxyfuel flame sprayed Cr3C2-NiCr. The properties of a special coating type depend on the used spraying method. Plasma sprayed MMCs show a slightly higher porosity than D-Gun sprayed coatings. The chemical composition of used powders has a big influence on the coating properties. Fe- and Ni-aluminide matrix coatings reinforced additionally with carbides, especially Cr3C2, show a better wear resistance compared to coatings containing just oxides as hard material.
Ceramic Coating of Alloy 625 using Controlled Atmosphere Plasma Spraying for Sea Water Corrosion Protection
Authors: Guipont V. , Fauvarque J-P. , Beauvais S. , Jeandin M. , Le Guyader H. , Lepresle H. , Grolleau A-M.
Published: September 2022

Crevice corrosion of metal/metal contacts in piping assemblies is a key issue for the design and the manufacturing of marine components. In this work, ceramic coatings onto alloy 625 were obtained using multi-processing CAPS facilities (Controlled Atmosphere Plasma Spraying). These coatings were sprayed in the CAPS chamber using air plasma spraying (APS, air at 100 kPa) or using high-pressure plasma spraying (HPPS, argon at 250 kPa) to achieve different coating microstructures and porosity levels. This allowed to investigate the corrosion behaviour in natural sea water of metal/ceramic contacts with different coating systems. Pure alumina or alumina-titania coatings with or without thermally-sprayed alloy 625 bond-coat were tested. Post-treatments like sealing of pores using epoxy resin were also achieved to study the resulting corrosion protection enhancement. Immersion and potentiostatic tests at +300 mV vs. SCE (Standard Calomel Electrode) tests were carried out in natural sea water at different temperature up to 60°C to expose specimens to the most severe working parameters. A beneficial protective effect of ceramic-coated alloy 625 has been clearly evidenced. Further investigations were performed using light microscopy and scanning electron microscopy to assess the corrosion behaviour and mechanical soundness of ceramic coated specimens which resulted in the determining of relevant technological solutions to prevent the risk of corrosion.
Fatigue and Fracture Resistance of Nanostructured Composite System: Chrome Carbide – Hard Oxide Aluminum – Aluminum
Authors: Kireitseu M.
Published: September 2022

In this paper Al-Al2O3-CrC nanostructured composite coating was presented, fatigue and fracture of the composite coating were investigated by nanoindentation, and in situ experiments performed in a scanning electron microscope to permit examination of freshly exposed surfaces. Crystallographic and morphological texture was characterized and the fracture resistance measured using fracture-mechanics. A CrC layer may improve the fracture resistance of an oxide aluminum layer. A CrC layer produced by pyrolitic deposition effectively heals the pores and defects of an oxide aluminum layer. It results in high load rating of the coating. Experiments revealed that in all cases, detection of an acoustic signal corresponded to an appearance of circular cracks seen on the surface; in a very few cases, examination of the surface after detection of a signal revealed the presence of two ring cracks. The degree of toughening associated with crack healing is determined by the number of healed defects and the effectiveness of the individual healing. Macroscopically, a crack path in the oxide aluminum appears to be straight, propagating along pores and internal voids. However, microscopically, a crack path exhibits a high degree of intergranular fracture. Because cracks generally deflect at small angles in the oxide aluminum layer, a crack path moves through pores and internal voids that usually concentrate internal stresses. The crack path is primarily intergranular at all velocities.
HVOF Reactive Spraying of Mechanically Alloyed Ni-Ti-C Powders
Authors: Horlock A.J. , Sadeghian Z. , McCartney D.G. , Shipway P.H.
Published: September 2022

This work reports research concerning the production of powder, suitable for reactive HVOF spraying, produced by mechanically alloying Ni(Cr), Ti and C elemental powder constituents. Powder mixing was achieved using a high-energy Uni-Ball II Mill and optimisation of the milling parameters are reported. The composition of the powder, at 50wt.%NiCr-40wt.%Ti-10wt.%C, was such that the application of heat has the potential to cause a SHS (Self propagating High Temperature Synthesis) reaction to take place. The utilisation of SHS reactions to produce TiC particles within metallic matrices is well known in bulk systems. However, this work describes carrying out this reaction in individual powder particles on exposure to the high temperature within the HVOF gun. The powder having undergone the SHS reaction during the spray process was deposited onto mild steel substrates to form a dense, coherent coating. The coatings thus formed were shown to contain nanoscale TiC in a Ni(Cr) matrix, indicating a SHS reaction had taken place. This TiC is much finer than that produced in conventional SHS reactions, which is typically ~5ìm. The percentage of TiC formed, and retained in the coating, was lower than expected from the constituent proportions and explanations for this observation are proposed. The microstructure of the coating is described and compared with a Ni(Cr)-TiC cermet coating sprayed using conventional SHS powder generated from reacted compacts which were crushed, sieved and classified to give sprayable feedstock powder.
Development and Implementation of HVOF WC/Co/Cr Coating as Alternative to Electrolytic Hard Chrome Plate in Landing Gear Applications Using Natural Gas as Fuel
Authors: Lee D. , Eybel R. , Evans R.
Published: September 2022

Replacement of Electrolytic Hard Chrome plating (EHC) using High Velocity Oxygen Fuel (HVOF) thermal spray processes to apply dense, wear and corrosion resistant coatings has been identified as a significant goal for the advancement and growth of the thermal spray industry for several years. This paper will provide some details of the development and production implementation of a WC-Co-Cr coating to be used as an alternative to EHC. WC-Co-Cr has been demonstrated in most situations to be superior to the wear performance of EHC with respect to providing functionality in aircraft landing gear hydraulic seal and bearing service. The developed coating is produced via the HVOF process using natural gas as fuel. EHC alternatives using WC-Co-Cr HVOF coatings require significant development prior to implementation into practice. Suitable wear, corrosion and lack of fatigue debit are examples of a few critical properties of coatings for use in landing gear applications. In addition a brief description of the production implementation of a turnkey spray cell for the coating of landing gears will be provided in this paper.
Fatigue and Deformations of HVOF Sprayed WC-Co Coatings vs. Hard Chrome Plating
Authors: Ibrahim A. , Berndt C.C.
Published: September 2022

Environmental problems of hard chrome plating are raising its cost and shrinking availability. HVOF and Detonation spray technologies for application of tungsten carbide and chrome carbide based coatings have proved to be cleaner and more effective than chrome plating. In this paper, the results of fatigue tests for WC-17Co coating deposited onto AISI 4340 steel by HVOF are compared to those for hard chrome plating. The fatigue life distributions as a function of the probability of failure for the coated AISI 4340 steel specimens showed that the HVOF coated specimens exhibited extraordinarily higher fatigue lives compared to the uncoated specimens whereas the hard-chrome-plated imparted fatigue strength degradation to the AISI 4340 steel.
Surface Changes of Several Thermal Spray Coatings Abraded by a TiO2 Slurry
Authors: Stavros A.J.
Published: September 2022

Three-body wear is important in many industrial processes. A laboratory study was performed to follow the response of highly polished thermal spray coating surfaces to degradation by hard titanium dioxide particles. A scanning electron microscope, a white light interferometer and a gloss meter were used to evaluate surface structure and texture of the aspolished and abraded surfaces. Tungsten carbide coatings with differing binder material and applied by different processes all degrade by the same mechanism: softer material is worn away by the hard TiO2 particles until the remaining structure consists of the hardest carbides protruding above the general surface plane. This structure is obtained in spite of significant differences in other surface properties such as roughness (Ra) and gloss number. If a more uniform wear surface is desired the carbide spacing must be reduced so that the coating more effectively presents a carbide surface to the TiO2 particles.
Evaluation of Modern HVOF Systems Concerning the Application of Hot Corrosion Protective Coatings
Authors: Bach Fr.-W. , Engl L. , Bach C. , Lugscheider E. , Parco M. , Duda T.
Published: September 2022

The high velocity oxyfuel flame spraying (HVOF) process appears to be an interesting alternative to low pressure plasma spraying (LPPS) processes for the application of MCrAlY coatings for the use of hot corrosion protection on turbine parts like blades and vanes. Lower investment costs for HVOF facilities compared to LPPS systems combined with adequate coating properties and a stable, easy controllable process can be seen as potential advantages regarding the application of this process. Several recent HVOF systems are screened concerning the application of MCrAlY coatings for hot corrosion protective coatings on turbine blades. In this research project, the Design of Experiments (DoE) is used to built up factorial experimental designs. The aim is, besides a benchmarking, to find out the potential of the HVOF systems to produce high quality hot corrosion protective coatings. The main emphasis of these preliminary investigations is on the evaluation of bonding defects in the interface, the porosity, and the oxide content of the coatings.
Microplasma Spraying of Bioceramic Coatings
Authors: Borisov Yu. , Vojnarovich S. , Bobric V. , Ulianchich N. , Jansen J. , Wolke J.G. , Botisov Y.
Published: September 2022

Microplasma spraying process provides deposition of coatings on small sizes parts and components. An investigation into the process of production and properties of microplasma coatings from bioactive ceramics (hydroxyapatite, tricalcium phosphate and fluorinoapatite) was carried out. Bioactivity of the coatings was tested in vitro by estimation of growth and differentiation of osteogenic cell.
Low Pressure Wire Arc and Vacuum Plasma Spraying of NiTi Shape Memory Alloys
Authors: Halter K. , Sickinger A. , Zysset L. , Siegmann St.
Published: September 2022

Thermal spray technology offers the advantage of producing thin-walled parts. Especially thermal spraying of NiTi shape memory foils demands highest control of atmospheric conditions due to their affinity to e.g. oxygen, hydrogen and nitrogen at high temperatures. This article describes two inert thermal spray techniques in order to produce free-standing shape memory foils, namely low pressure wire arc (LPWAS) and vacuum plasma spraying (VPS). The advantage of low pressure wire arc spraying is the ability to use NiTi wire from commercial suppliers without the detour of powder production, which may result in additional undesired reactions and phases. The benefit of vacuum plasma spraying is the higher kinetic energy of the particles due to higher plasma gas amount and speed. Within the scope of this paper, coatings produced with both methods (LPWAS and VPS) are discussed with regard to their coating microstructure and physical / chemical properties, transformation temperatures (DSC), porosity (%) and their shape memory effect.
Effect of Aluminum Phosphate Sealing on the Elastic Properties of Plasma Sprayed Ceramic Coatings
Authors: Dubský J. , Chráska P. , Ahmaniemi S. , Vippola M. , Vuoristo P. , Mäntylä T.
Published: September 2022

Plasma sprayed ceramic coatings have much lower stiffness in comparison to sintered ceramics. The reason for that is their characteristic microstructure with porosity and microcracks. Microcracks decrease the interlamellar cohesion in vertical direction, but also affect the individual splat properties in the horizontal direction. For that reason sealing treatments are often applied with plasma sprayed ceramic coatings in order to improve their corrosion resistance and mechanical properties. In this paper the effect of aluminum phosphate sealing treatment on the elastic properties of plasma sprayed Al2O3 and Cr2O3 coatings were studied. Residual stresses in the plane of coating surfaces were compared using the X-ray diffraction analysis (XRD). A special four point bending device, designed for the X-ray diffractometer, was used in determining the effect of additional load on coating elastic behavior. In as-sprayed alumina coatings tensile stresses of about 400 MPa were detected while only about 40 MPa of compressive stresses were measured in the as-sprayed chromia coatings. Microstructural characterization revealed that sealing treatment had apparently affected the coating microstructure and filled some microcracks and interlamellar spacings. As a result, in both sealed coatings, compressive stresses of about 100 up to 150 MPa were observed. Also a better stiffness of both materials was detected during the bending of specimens. In addition, the sealing treatment increased nearly ten times the Young’s modulus, determined by XRD analysis under various tensile loads.
Integrated Machine Tool for Laser Beam Cladding and Freeforming
Authors: Nowotny St. , Scharek S. , Naumann T.
Published: September 2022

The repair and quick geometrical changes of components and tools are currently the most important applications of laser build-up welding. Advanced laser technology permits the integration of the main process steps into one machining center for a very efficient and flexible manufacturing process. The solution presented in this paper consists of a 3axes CNC milling machine, in which a 3 kW Nd: YAG laser, a coaxial powder nozzle, and a digitizing system are integrated. All functions (data processing, laser process, powder feeding, and milling) are controlled by one CNC controller using specially developed software. In the first step the workpiece needs to be adjusted to the machine table. Then the contour of the damaged surface is determined by either an optical or mechanical digitizing system. Using the resulting data, a software system generates automatically the laser build-up strategy and the CNC programs for the laser and the milling processes. After laser free-forming, a raw piece with an oversize of 0.3 to 0.6 mm is made. From this geometry the end contour is milled with an accuracy of some 10 microns. This way the machine produces a completely finished tool.
Influence of Carrier Gas Flow and Liquid Injection in the Plasma Jet on Plasma Characteristics During the Atmospheric Plasma Spray Process
Authors: Döring J.-E. , Vaßen R. , Stöver D.
Published: September 2022

The effect of argon carrier gas flow, ethanol- or water injection on the plasma-composition, -enthalpy and – temperature as well as on the entrainment from the ambient was investigated in comparison to the pure plasma condition of an Ar-H2-plasma. Additionally, the plasma gas flow rate and power levels were varied. The enthalpy, and thus the plasma temperature, as well as the composition and speed are determined by means of an enthalpy probe system. Spatial resolved data could be obtained by translating the torch via a robot so that a temperature and speed map shows the evolution of plasma features with increasing stand-off distance.
On the Stripping of Turbine Blades and Vanes: Mechanisms and Performances of Chemical Stripping for the Removal of NiCrAlY Thermal Spray Coatings
Authors: Scrivani A. , Soranzo M. , Rizzi G. , Bardi U. , Carafiello L.
Published: September 2022

The present paper is addressed to the study of chemical stripping processes used in order to remove Thermal Spray deposited Thermal Barrier Coatings. Thermal Barrier Coatings consist in a bond coat of MCrAlY alloy (where M means for Ni, Co or a combination of both), that can be obtained generally by Vacuum Plasma Spray or High Velocity Oxygen Fuel and in a top coat of Yttria Partially Stabilized Zirconia obtained by Air Plasma Spray. These coatings are applied to gas turbine components in order to improve their hot corrosion and oxidation resistance and their service life time through a reduction of the service temperature. The paper focuses on the removal of NiCrAlY bond coat performed by chemical attack (based on hydrochloric acid). Characterization of the blade and vane surfaces after removal of NiCrAlY coatings has been performed from the point of view of surface morphology, metallurgical structure and chemical composition. The efficiency of the acid solution in NiCrAlY removal has been investigated and the behaviour of two Ni based alloys substrates in aggressive environment has been tested. The HCl based stripping solution shows good performances in Vacuum Plasma Sprayed NiCrAlY coatings removal from Ni superalloys. The tested stripping procedure is fast and safe because no damages to base materials have been noted.
Development of Light Metal Matrix Composite Coatings Using High Velocity Thermal Spray Processes
Authors: Bach Fr.-W. , Engl L. , Josefiak L.A.
Published: September 2022

In this paper the development of thermal sprayed, hard phase reinforced aluminum based layers, in particular for coating light metal substrates is described. The aim of the project was to obtain wear resistant coatings for applications on light metal surfaces combined with other advantageous characteristics, especially good thermal conductivity. One possible application for these coatings can be seen in automotive light weight constructions as wear protection for brake discs or drums. Flame shock spraying as well as high velocity oxyfuel flame spraying (HVOF) were used as coating processes. As consumables mechanically alloyed powders consisting of aluminum and ferric oxide were used. Due to the high kinetic process energy developed by the selected procedures in connection with the exothermically reacting spraying material, a new light metal matrix composite was produced. One major advantage of this coating material is the in-situ synthesis of the hard particles in the aluminum matrix during the spray process resulting in good adhesion/cohesion properties. This research project includes an extensive analysis of the consumables including differential thermal analysis, SEM, and EDX. Furthermore, process parameters were optimized. This includes a characterization of the HVOF process using modern particle diagnostics. Besides good bonding properties proven coating characteristics are high thermal conductivity and thermal shock resistance as well as good wear behavior even at elevated temperatures. The results show that the developed coating system is a promising alternative for cast aluminum matrix composite materials used for wear stressed parts even at elevated temperatures.
HVOF Coating Characterization by Acoustic Emission Using Four-Point Bending Test
Authors: Bouaricha S. , Legoux J.-G. , Marcoux P.
Published: September 2022

Four-point bend test using acoustic emission (AE) was used to compare coating properties under mechanical solicitation, mainly the toughness and the spalling behaviour. Coatings are made from the same material; the 2005NS (WC-17Co), sprayed with an HVOF gun at various spray parameters. Coatings deposited on thin rectangular substrates were tested with the coating bent in tension and in compression. AE features like the event number, energy per event and cumulative energy were used to assess the damage in the coatings. The results are analyzed in relation with the coating microstructure.
Influence of Surface Laser Cleaning Combined with Substrate Preheating on the Splat Morphology
Authors: Liao H. , Gammoudi A. , Costil S. , Coddet C.
Published: September 2022

The morphology of sprayed splat raises the coatings adhesion and the properties which are determined by the spraying parameters. A lot of studies in this field show that the substrate surface temperature is a very relevant factor for the splat shape: the hypotheses of substrate surface wetability and contamination or absorption layer on the surfaces are supported by the fact that the near disk-shaped splat can be obtained in increasing the substrate temperature. In the PROTAL process, a short duration pulse laser is used to ablate the substrate just before powder spraying. This ablation is powerful enough to eliminate the contaminations on the substrate surface and to improve the adhesion. In this study the analyses of NiAl splat morphology on polished TA6V substrate were carried out using PROTAL process with different substrate temperatures and different heating modes: the flame and another laser. Results show that the temperature at which the disk shaped splat can be obtained was decreased dramatically by PROTAL process and PROTAL process combined with another laser has increased the adhesion strength of the coatings.
Modeling of Coating Formation and Heat Flux to Substrate by Particles and Plasma Jet in Plasma Spraying
Authors: Mariaux G. , Legros E. , Vardelle A.
Published: September 2022

This work deals with a 3-D transient simulation of the air plasma spraying of ceramic powders using a C.F.D. commercial code ESTET v3.4 that has been adapted to thermal plasma conditions. The mathematical model computes the distribution of particle velocity, temperature, molten state and size at impact and predicts the heat transfer to the substrate by plasma jet and particles. It incorporates the conversion from electrical to thermal energy in the torch nozzle as well as coating formation on the substrate. It makes it possible to predict the shape of the coating footprint when the torch and the substrate are fixed. The projections of the model are compared with experimental results that involve flow characteristics, time-dependant particle behavior in the flow and heat flux to the substrate.
Computer Modelling of the Plasma Spraying Process
Authors: Borisov Yu. , Krivtsun I. , Muzhichenko A.
Published: September 2022

A computer model intended for modelling of subsonic turbulent plasma jets generated by plasma spray torches, as well as for simulation of spray particles behaviour in such jets is presented. Comparison of computer modelling and measurement results showed fairly good agreement.
Powder Densification and Spheroidization Using Induction Plasma Technology
Authors: Fan X. , Guo J. , Dignard N. , Normand C.
Published: September 2022

Spheroidization of powder particles is one of the successful commercial applications of induction plasma technology. A review is presented of case studies in which powder densification and spheroidization using induction plasma technology has played a key role in substantial improvement of powder quality and fluidity. Results are given for both metallic and ceramic powders at the pilot plant and industrial scale production. The presentation will cover both technical and economic features of the process. A detailed economic analysis of the process is presented for a production capacity of 15 and 30 kg per hour of tungsten carbide powder.
In-Flight Particle Imaging in Thermal Spraying with Diode Laser Illumination
Authors: Larjo J. , Hämäläinen E. , Kriikka N.
Published: September 2022

Imaging techniques have gained popularity in thermal spray diagnostics over the last decade. They provide large amounts of data for research, development and process monitoring. The most important measured spray parameters are particle temperature and velocity. The biggest advantage of imaging techniques compared to optical point measurements is that they provide instantaneous distribution measurements. We present the application of high-power diode laser illumination to detect weakly emitting particles in thermal spaying. This extends the feasibility of imaging diagnostics to several demanding environments, including cold spray, powder mixing region of a plasma spraying torch and low-pressure plasma spray.