bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Gladiolus Genotypes under Khumaltar Condition of Nepal
Authors: Dhakal Mira , Poon Tul Bahadur , Adhikari Pratistha , Pandey Suprabha , Bhattarai Shandesh
Published: May 2021

Seven promising genotypes of Gladiolus were experimented during the two consecutive years of 2014/15 and 2015/16 in the field of Horticulture Research Division, Khumaltar, Lalitpur (1332 masl) to evaluate the performances of their vegetative, floral and corm characteristics. The experiment was laid out in Randomized Complete Block Design with four replications. The treatments consisted of seven genotypes (ARSDG-01, ARSDG-02, ARSDG-03, ARSDG-04, ARSDG-05, ARSDG-06 and ARSDG-07). Fifty-four corms of each genotype were planted in the crop geometry of 25 x 25 cm. A total of sixteen characters were observed. The pooled results of two years data indicated significantly different except plant height, spike length, rachis length, number of cormels per mother corm and individual corm weight due to the effects of seven evaluated genotypes. Genotype ARSDG-04 was proven as the earliest one for days to the first spike emergence (73.00 days), the full spike emergence (76.50 days) and the first unfurling of florets (83 days). In contrast, ARSDG-01 and ARSDG-06 were late genotypes for the same three characters. The number of florets/spikes was considerably high in two genotypes viz., ARSDG-06 (21.00) and ARSDG-03 (20.50). The number of daughter corms/mother corm was significantly high in ARSDG-05 (3.10) and ARSDG-04 (2.92) whereas it was minimally low in ARSDG-02 (1.66) and ARSDG-07 (1.69). Summing up all sixteen characters of evaluated genotypes, ARSDG-04 as the first, ARSDG-05 as the second and ARSDG-03 as the third have respectively emerged as superior ones as opposed by those of the rest of evaluated genotypes of Gladiolus.
Advancement, Simplification and Piloting of Electrical Proso Millet De-Husker (Chino Kutak)
Authors: Bhandari Ganga Ram , Gauchan Devendra , Bhandari Bharat , Joshi Bal Krishna , Panta Saroj
Published: May 2021

Proso millet is a minor cereal crop commonly cultivated in rain fed marginal uplands particularly in the mid and far western mountain region of Nepal. It is potential crop for ensuring food and nutrition security and conservation of local crop biodiversity in high mountain region. Traditionally Proso millet (locally as chino) is processed manually on Mortar and Pestle (Okhal) by using muscular power. However, de-husking (pearling) of Proso millet is very tedious job. The traditional method of processing takes 1 hour to dehusk 2 kg – 3 kg of Proso millet for two women and cause lots of physical exertion to them. Therefore, GEF UNEP Local Crop Project in collaboration with Agricultural Engineering Divisionof NARC initiated program in 2017to design, fabricate and test electric Proso Millet de-husking machine (called chino kutak) that is safe and economical in operation for the use of the local farmers of remote Himalayan region. The model-1 designed, fabricated and piloted at Humla (Chhipra, Kharpunath Rural Municipality) in 2018 was improvised version of Finger millet processing machine. The Model-2 was based on the Centrifugal type working on impact principle was developed in January 2020.  The Model-2 was very much successful in all variety of Proso millet and higher capacity up to 52.5 kg/hr.it is equally applicable to other millets.
Conservation Agriculture Mitigates the Effects of Climate Change
Authors: Karki Tika Bahadur , Gyawaly Pankaj
Published: May 2021

Intensive tillage based conventional agriculture have high global warming potential. Alternative to this, conservation agriculture (CA) systems utilize soils for the production of crops by reducing excessive tillage, maintaining crop residue on the soil surface, and adoption of crop rotations. The paper attempts to review the findings of CA based experiments under different cropping systems within and outside of the country. It has been found that CA increases and sustains the crop productivities, mitigates green house gas emissions from agriculture by enhancing soil carbon sequestration, improving soil nutrient status and water use efficiencies, and reducing fuel consumption. Mainstreaming of CA systems in Nepal is hindered by its knowledge gap, inadequate farm machineries and tools, small holdings, poor infrastructures, and lack of CA friendly policy support. Therefore, there is an urgent need to test, verify and scale-out the CA based technologies by Nepal Agricultural Research Council (NARC) across the different agro-ecologies through farmer-centered partnership among the international institutions, public and private sector of Nepal.
Sustainable Intensification in Agriculture: An Approach for Making Agriculture Greener and Productive
Authors: Shrestha Jiban , Subedi Subash , Timsina Krishna Prasad , Subedi Sudeep , Pandey Meena , Shrestha Aakriti , Shrestha Sajina , Hossain Mohammad Anwar
Published: May 2021

Sustainable intensification of agriculture is a good approach for reducing the yield gap without exacerbating the current condition of the environmental components, which is a big challenge for agriculture in the modern world. This review provides a summary of the role and approaches of sustainable intensification in agriculture which offer ways to increase crop production and create long-term sustainability in agriculture production. The current demand for food has continued to rise as a result of the world's rapidly increasing population. In order to increase crop/food production, agricultural systems should be intensified by more sustainable practices, as well as by reforming existing production systems/techniques and diversifying them into newer and more profitable enterprises. Despite the heavy use of inputs, farmers have recently been unable to achieve optimal crop yields. The judicious use of agricultural inputs, combined with improved management techniques, is important for advancing sustainable intensification. New scientific techniques in agronomic practices, as well as improved farm mechanization, are helping to boost resource use efficiency in sustainable crop production. The sustainable agricultural intensification is necessary to increase the agricultural productivity under the changing and adverse climatic conditions while maintaining healthy production practices.
Detection of mutations associated with artemisinin resistance in K13 gene of Plasmodium falciparum parasites
Authors:   nstitute of Biomedicine and Pharmacy, Vietnam Military Medical University, Tran Thi Thu Huyen , Nguyen Thi Lan Dung ,   nstitute of Biomedicine and Pharmacy, Vietnam Military Medical University,   University of Science, Vietnam National University, Hanoi, Nguyen Thuy Trang ,   nstitute of Biomedicine and Pharmacy, Vietnam Military Medical University,   University of Science, Vietnam National University, Hanoi, Nguyen Van Ninh ,   nstitute of Biomedicine and Pharmacy, Vietnam Military Medical University,   University of Science, Vietnam National University, Hanoi, Ho Anh Son ,   nstitute of Biomedicine and Pharmacy, Vietnam Military Medical University, Hoang Van Tong ,   nstitute of Biomedicine and Pharmacy, Vietnam Military Medical University
Published: May 2021

Objective: this study aims to develop a methodology for detecting mutations in the K13 gene and determine mutation frequencies in clinical samples. Method: total DNAs were extracted blood samples collected from 50 patients in failure with artemisinin treatmentin the Central Highlands region. A fragment of the K13 gene was amplified, purified, and sequenced by the Sanger method. The K13 sequences were analysed by using Bioedit and aligned with the reference sequence to determine K13 mutations. Results: successfully amplified the K13 gene segment with size 799 bp in P. falciparum. After sequencing, there was a nucleotide substitution of A>G at position 1740, leading to changes in amino acids C>Y at the respective position 580. In the 50 patient samples, 41/50 (82%) samples showed the C580Y mutation, 9/50 (18%) of the samples had no mutation, and there was no other mutation. Conclusion: the authors have successfully developed and optimised a procedure for detecting the mutation C580Y in K13 in P. falciparum and determined the mutation frequency in the K13 gene.
Hand-Held Point-of-Care Ultrasound: A New Tool for Veterinary Student Self-Driven Learning in the Time of COVID-19
Authors: Williams Zoë J. , Sage Abby , Valberg Stephanie J.
Published: May 2021

The coronavirus pandemic abruptly halted all in-person clerkships, or clinical rotations, for clinical veterinary students across the United States. Online clerkships in radiology offered the opportunity to expand the student’s ability to interpret medical images but did not allow for the development of physical hands-on imaging skills recognized as core competencies in veterinary medicine. The present report highlights the value of providing veterinary students with a smartphone-associated Butterfly iQ point-of-care ultrasound during a 3-week self-driven virtual clerkship. During the virtual rotation, the student was able to develop the skills required to generate sufficient quality images using three horses residing on her property. The affordability, portability, ease of use of the Butterfly iQ and availability of animals made it possible to develop hands-on imaging skills when distance learning was required.
Structure, Properties and Potentials of WC-CO, Cr3C2-NiCr and TiC-Ni-Based Hardmetal-like Coatings
Authors: Berger L.-M. , Hermel W. , Vuoristo P. , Mäntylä T. , Lengauer W. , Ettmayer P.
Published: May 2021

The surfaces of machine components can be effectively protected against wear by highly resistant hardmetal-like coatings, such as WC-Co and Cr3C2-NiCr, deposited by different thermal spray processes. These composite materials are characterized by the presence of hard carbide particles embedded in a ductile metal binder matrix which have also found many applications as sintered parts (cutting tools, wear resistant parts, mining drills and others) obtained by a powder metallurgy route. Conclusions on the potentials of the different systems for coating applications can be made on the base of experiences and fundamental research from sintered hardmetals. In this paper a comparison of the properties of sintered parts and thermally sprayed coatings of the WC-Co, Cr3C2-NiCr and (Ti,Mo)C-NiCo systems is given. The structure and properties of the coatings depend strongly on the technology of spray powder preparation, the combination of spray process temperature and particle velocity, and other spray process parameters. It is shown that the TiC-Ni based system can be significantly improved by alloying. This makes the system suitable for coating applications where simultaneous high wear and corrosion resistance in combination with high temperature stability are required. This system can partially substitute the commercially introduced systems but has also the potential to explore new applications.
Electrochemical Aging of Thermal Sprayed Zinc Anodes on Concrete
Authors: Holcomb G.R. , Bullard S.J. , Covino B.S. , Cramer S.D. , Cryer C.B. , McGill G.E.
Published: May 2021

Thermal-sprayed zinc anodes are used in impressed current cathodic protection systems for some of Oregon's coastal reinforced concrete bridges. Electrochemical aging of zinc anodes results in physical and chemical changes at the zinc-concrete interface. Concrete surfaces heated prior to thermal-spraying had initial adhesion strengths 80% higher than unheated surfaces. For electrochemical aging greater than 200 kC/m2 (5.2 A-h/ft2), there was no difference in adhesion strengths for zinc on preheated and unheated concrete. Adhesion strengths decreased monotonically after about 400 to 600 kC/m2 (10.4 to 15.6 A-h/ft2) as a result of the reaction zones at the zinc-concrete interface. A zone adjacent to the metallic zinc (and originally part of the zinc coating) was primarily zincite (ZnO), with minor constituents of wulfingite (Zn(OH)2), simonkolleite (Zn5(OH)8Cl2H20), and hydrated zinc hydroxide sulfates (Zn4S04(OH)5xH20). This zone is the locus for cohesive fracture when the zinc coating separates from the concrete during adhesion tests. Zinc ions substitute for calcium in the cement paste adjacent to the coating as the result of secondary mineralization. The initial estimate of the coating service life based on adhesion strength measurements in accelerated impressed current cathodic protection tests is about 27 years.
Stainless Steel Coatings for Corrosion Protection of Steel Rebars
Authors: Arsenault B. , Gu P. , Legoux J.G. , Harvey B. , Fournier J.
Published: May 2021

Steel reinforcement corrosion is one of the most serious causes of the premature deterioration of North American bridges and parking garages. Carbon steel rebars are very vulnerable to corrosion in salt contaminated concrete from deicing or coastal environment since the chloride ions induce severe corrosion as they reach the reinforcing steel rebars and depassivate the carbon steel. This paper evaluates the potential of using stainless steel coatings as a means to protect steel rebars from corrosion, especially in a salt contaminated concrete environment. The 316 L stainless steel coated coupons and rebars were prepared using Arc-sprayed and HP/HVOF processes. The corrosion performance of coatings were evaluated using linear polarization, a.c. impedance and salt spray techniques. Metallographic examination was also performed to characterize the coating microstructure.
The Mechanical Properties of Combustion-Sprayed Polymers and Blends
Authors: Brogan J.A. , Berndt C.C. , Claudon A. , Coddet C.
Published: May 2021

The mechanical properties of EMAA copolymer are dependent upon the thermal spray processing parameters. The parameters determine coating temperatures which, in turn, affects the microstructure. If the deposition temperature is too low, (104 °C for PFl 13 and 160 °C for PFl 11) coatings have low strengths and low energy to break values. Increased coating temperatures allow the particles to fully coalesce resulting in maximized strength and elongation to break. However, at 271 °C, PFl 11 had visible porosity which decreased both strength and elastic modulus. Pigment acts as reinforcement in the sense that the modulus increased but the elongation to break decreased, thus reducing the energy to break. Water quenching reduces the elastic modulus and yield strength, but increases the elongation to break for both EMAA formulations. The mechanical properties of post consumer commingled plastic and PCCP / EMMA blends improved if the recycled plastic was pre-processed by melt-compounding. Melt compounding increased the strength and toughness by improving the compatibility among the various polymer constituents. The addition of PCCP increases the modulus and yield strength of ethylene methaciylic acid copolymer.
An Investigation of Particle Trajectories and Melting in an Air Plasma Sprayed Zirconia
Authors: Neiser R.A. , Roemer T.J.
Published: May 2021

The partially stabilized zirconia powders used to plasma spray thermal barrier coatings typically exhibit broad particle-size distributions. There are conflicting reports in the literature about the extent of injection-induced particle-sizing effects in air plasma-sprayed materials. If significant spatial separation of finer and coarser particles in the jet occurs, then one would expect it to play an important role in determining the microstructure and properties of deposits made from powders containing a wide range of particle sizes. This paper presents the results of a study in which a commercially available zirconia powder was fractionated into fine, medium, and coarse cuts and sprayed at the same torch conditions used for the ensemble powder. Diagnostic measurements of particle surface temperature, velocity, and number-density distributions in the plume for each size-cut and for the ensemble powder are reported. Deposits produced by traversing the torch back and forth to produce a raised bead were examined metallographically to study their shape and location with respect to the torch centerline and to look at their internal microstructure. The results show that, for the torch conditions used in this study, the fine, medium, and coarse size-cuts all followed the same mean trajectory. No measurable particle segregation effects were observed. Considerable differences in coating microstructure were observed. These differences can be explained by the different particle properties measured in the plume.
RF-Plasma Technology for Near Net-Shape Deposition
Authors: Fendler E. , Müller M. , Henne R. , Gitzhofer F. , Boulas M.L.
Published: May 2021

A chromium alloy as used for the metallic bipolar plate of a solid oxide fuel cell was processed by RF-plasma spraying to dense free-standing parts. The plasma spray parameters were successfully adapted for two different types of powder. The layer properties, particularly the porosity and the splat shape were investigated in dependence on the spray angles. All the coatings produced with off-normal spray angles show higher porosity increasing from spray angles of 60° to 30°. The splat orientation changes from parallel to the inclined surfaces to almost perpendicular to the plasma jet axis with shallower angles.
Characteristics of Phosphoric Acid Sealed Ceramic Oxide Coatings
Authors: Kumpulainen E. , Vippola M. , Vuoristo P. , Sorsa P. , Mäntylä T.
Published: May 2021

Plasma sprayed ceramic coatings usually have relatively high open porosity in order to provide a good corrosion protection. By using sealants the porosity values can be reduced. In this study atmospheric plasma sprayed (APS) aluminium oxide, chromium oxide and zirconium oxide coatings were sealed by a phosphoric acid treatment. After impregnation the coatings were heat treated at a curing temperature of 400°C. Phosphoric acid was found to react with the coating material during the heat treatment. Wear resistance was evaluated by rubber wheel abrasion tests and corrosion resistance by electrochemical potentio-dynamic polarization tests. Hardness values were also measured. Corrosion resistance and hardness values of sealed coatings were remarkable better in comparison to the unsealed coatings. Rubber wheel abrasion resistances of the sealed coatings were equal to those of Al2O3, ZTA, SiC and Si3N4 sintered ceramics.
Correlation between Particle Temperature and Velocity and the Structure of Plasma Sprayed Zirconia Coatings
Authors: Prystay M. , Gougeon P. , Moreau C.
Published: May 2021

The correlation between particle temperature and velocity and the structure of plasma sprayed zirconia coatings is studied to determine which parameter most strongly influences the coating structure. The particle temperature and velocity are measured using an integrated optical monitoring system positioned normal to the spraying axis. The total porosity, angular crack distribution, crack size distribution and thermal diffusivity are correlated with the particle temperature and velocity. Results show that the temperature of the sprayed particles has a larger effect on the coating properties than the velocity in the conditions investigated.
Correlations Between In-Flight Particle Concentrations and Coating Properties in Atmospheric Plasma Spraying of Alumina
Authors: Lehtinen T. , Knuuttila J. , Vattulainen J. , Mäntylä T. , Hernberg R.
Published: May 2021

The plasma spraying process is controlled by various parameters that have an influence on powder particle velocities, temperatures and trajectories just before impact to the substrate. In order to fully utilize the thermal and kinetic energy of the plasma it is important to obtain information from these powder particle properties. In this work an intensified CCD camera has been used to detect in-flight particles in an atmospheric plasma spraying process. Plasma spraying was performed using fused and crushed AI2O3 powder. The powder carrier gas flow rate was varied during the spraying experiments. All the other deposition parameters were kept constant. Coatings produced using relatively new spraygun electrodes are compared with ones produced later with the same electrodes when they were worn out. The particle concentration is determined on a relative scale by the fraction of the area of a CCD camera frame covered by particle images. Further investigations necessary to clearify the relationship between the measured relative particle concentration and the true particle concentration are identified. The coatings are analyzed for wear resistance, degree of melting, deposition efficiency, hardness and porosity. The dependence of these coating properties on the relative particle concentration and the effect of electrode wear on the relative particle concentration are studied.
Influence of Shroud Gas Flow and Swirl Magnitude on Arc Jet Stability and Coating Quality in Plasma Spray
Authors: Chen H.C. , Duan Z. , Heberlein J. , Pfender E.
Published: May 2021

The quality of a plasma sprayed coating is influenced by the plasma jet stability; entrainment of cold air through large scale turbulence can lead to variations in particle heating and trajectories resulting in increased unmelt densities, reduced deposition efficiencies, and oxidation of metal particles. The jet instabilities are in part caused by the swirl flow of the plasma gas. With two modifications to an atmospheric pressure plasma spray torch, we have investigated the influence of reduced swirl flow on jet stability, particle trajectories, and coating quality. The modifications are (1) addition of a shroud consisting of a porous ring surrounding the anode nozzle while simultaneously injecting part of the shroud gas inside the nozzle with a swirl component in the direction opposing the plasma gas vortex, and (2) an injector ring with which part of the plasma gas is injected radially and part tangentially producing reduced vortex flow for the same plasma gas flow rate. Jet stability and particle trajectories are determined using a LaserStrobe system combined with image analysis, and coatings have been evaluated by determining porosity and unmelt density. Results indicate that deposition efficiency is most affected by reduced vortex flow, while the shroud addition reduces unmelt density and porosity.
Modeling of the Laser Engraving at Plasma Sprayed Cr2O3 Coatings on Anilox Rolls
Authors: Groc M. , Pawlowski L. , Smurov I. , Clinton G. , Pitt R.
Published: May 2021

This paper presents a preliminary study of mathematical modeling and numerical simulation of laser engraving process. The 1-D simulation concerned CO2 c. w. pulsed laser engraving of plasma sprayed Cr2O3 coatings as used in the manufacture of anilox rolls. The thickness of the evaporated material was calculated as a function of laser processing parameters viz. pulse length and power density. The actual thermophysical coefficients of plasma sprayed chromia were used if available and the results of calculated thickness of evaporated layer are compared with the experimentally determined depth of engraved cells to estimate unknown coefficients of liquid chromia. Finally, the experimental effect of overflow was related to the calculated thickness of liquid layer. The experimental procedure of minimization of this effect is proposed.
Crystalline Growth within Alumina and Zirconia Coatings with Coating Temperature Control during Spraying
Authors: Haddadi A. , Grimaud A. , Denoirjean A. , Nardou F. , Fauchais P.
Published: May 2021

In this paper the influence on the coating generation of substrate preheating during spraying, relative movements torch to substrate and cooling conditions is systematically studied for partially stabilized zirconia and alumina coatings. Beads and coatings are sprayed with Ar-H2 dc plasma jets in air. The obtained structure, resulting hardness and adhesion/cohesion for each spraying condition is discussed.
Plasma Sprayed Zirconia: Relationships Between Particle Parameters, Splat Formation and Deposit Generation-Part I: Impact and Solidification
Authors: Léger A.C. , Vardelle M. , Vardelle A. , Fauchais P. , Sampath S. , Berndt C.C. , Herman H.
Published: May 2021

Joint research work between the University of Limoges and the State University of New York, Stony Brook, has been carried out on the impact and solidification of plasma sprayed zirconia particles. A measurement device, consisting of a phase doppler particle analyser and a pyrometer, was used to correlate the characteristic parameters of splats to those of the substrate and to the size, velocity and temperature of the impacting particles.
Droplet Impact and Solidification in a Thermal Spray Process: Droplet-Substrate Interactions
Authors: Pasandideh-Fard M. , Mostaghimi J.
Published: May 2021

Experiments have shown that the mechanical properties of plasma-sprayed coatings depend to a large extent on the details of the spraying process, in particular, they are strongly dependent on the details of the solidification and deformation history of the individual droplets which are in turn highly affected by the substrate conditions such as its temperature, material, and surface thermal contact resistance. In this study, droplet-substrate interactions are investigated through a complete numerical solution of droplet impact and solidification for a typical thermal spray process. The energy equation is numerically solved for both droplet and substrate regions; the solution is based on the Enthalpy Method for the liquid and solidified parts of the droplet, and the conduction heat transfer in the substrate. The numerical solution for the complete Navier-Stokes equations is based on the modified SOLA-VOF method using rectangular mesh in axisymmetric geometry. The developed model is suited for investigating droplet impact and simultaneous solidification permitting any desired condition at the substrate. The splat shape, the solidification front, and the temperature profile in the entire droplet and substrate regions are obtained at any desired time elapsed after the impact. Through these results, the nucleation and growth of solidification and droplet-substrate interactions are extensively studied.
Mathematical Modeling of Flattening Process on Rough Surfaces in Thermal Spray
Authors: Fukanuma H.
Published: May 2021

Thermal spray layers are formed on rough surfaces; however, the flattening process on rough surfaces has not yet been clarified. A mathematical flattening model which takes into account the roughness of the substrate or previously coated layers is proposed in this paper. As a result of surface roughness, the flattening degree and the flattening time decrease with increasing surface roughness in this model. In addition, the characterization of surface roughness is introduced for the flattening model. Several calculated cases of the flattening model are shown.
Splat Solidification of Tin Droplets
Authors: Bhola R. , Chandra S.
Published: May 2021

An experimental study was done of the impact and solidification of tin droplets falling on a stainless steel surface. The surface temperature was varied from 25°C to 240°C. Measurements were made of droplet diameters and contact angles during droplet spread. At a surface temperature of 240°C there was no solidification, and a simple model of liquid droplet impact successfully predicted the extent of droplet spread. Droplets impacting on surfaces at 25°C and 150°C solidified before spreading was complete.
Tensile Bond Strength Variance of Thermally Sprayed Coatings with Respect to Adhesive Type
Authors: Evans K.A.
Published: May 2021

A Round Robin study involving 19 coating suppliers and independent laboratories was conducted on tensile testing of thermally sprayed coatings to determine the accuracy and consistency of the tensile data among the participating labs and within a lab. One coating system (NiCrAl) and two adhesive types (film vs. liquid epoxy) were used. The results showed the average tensile strengths for the coating system using the liquid epoxy systems (EC2086/EC2214) were consistently higher than the average values which resulted using the film epoxy system (FMIOOO). However, less scatter in the results was observed when the FMIOOO film epoxy was used.
Minimization of the Residual Bending of Plates with Sprayed Coatings
Authors: Kroupa F. , Neufuss K. , Lauschmann H. , Materna A. , Oliva V.
Published: May 2021

The theory of residual stresses and of residual bending of plates with relatively thick sprayed coatings is summarized and some methods to minimize the bending are proposed. The particular case of an aluminium alloy substrate with a relatively thick plasma sprayed ceramic coating, with a large difference of thermal expansion coefficients, is discussed.
Supersonic Induction Plasma Spraying of Dense YSZ Electrolyte Membranes
Authors: Mailhot K. , Gitzhofer F. , Boulos M.I.
Published: May 2021

In this paper, RF induction plasma deposition of Yttria Stabilized Zirconia (YSZ) is studied with the objective of producing dense solid electrolyte membranes for Solid Oxide Fuel Cells (SOFC). Different RF induction plasma torch configurations were tested. The results show that high density layers could be obtained using a supersonic Laval nozzle attachment on a standard torch. Coating with apparent porosity of less than 1% could be obtained using this technique at relatively high deposition rates. Optical or electron microscopic examination of the deposit coupled with image analysis show, however, that porosity measurements using these techniques can suffer from relatively large discrepancies depending on equipment setting. A discussion is presented of the validity of this porosity measurement technique.
Slurry Erosion of Arc-Sprayed Metal and Composite Coatings
Authors: Arsenault B. , Legoux J.-G. , Hawthorne H.
Published: May 2021

Two grades of stainless steel, 316 and 440-C, in the form of solid wire, and two cored wires, Duocor and 95-MXC, were used. Coatings were made using the Miller BP-400 and TAFA 9000 systems. Slurry jet erosion tests were conducted using a 10 %w/w alumina particle/water slurry. Two alumina particle sizes, 320 and 80 grit (nominal grain diameters 35 μm and 200 μm, respectively) were used at impinging angles of 90° and 20°. The nominal impact velocity of the slurry was 15 m/s and the nozzle-specimen distance 100 mm. The volume loss of material under various slurry erosion conditions was related to the coating properties and microstructure. Results indicate that the wear behavior of arc sprayed materials is dependent on the erodent particle size; for large erodent particle size, the relative erosion is almost independent of the impinging angle, while for the smaller particle size the angle effect is the dominant factor. This behavior can be related to the lamella structure and the relative toughness of the different phases of the coatings.
Low Friction Cobalt-Based Coatings for Titanium Alloys
Authors: Hajmrie K. , Chilkowich A.P.
Published: May 2021

Protective coatings adapted for titanium alloys which come into frictional contact with one another are described. Among the many coatings investigated, the best ones are cobalt based. The coatings are sprayed only on one of the rubbing surfaces. During rubbing, a small part of the coating transfers to the unprotected titanium alloy surface. The rubbing pair is thus essentially composed of two cobalt alloy-based surfaces. This leads to low coefficient of friction and little or no damage to the rubbing surfaces. The coatings find particular application in the protection from adhesive and fretting wear, galling and seizure of gas turbine and jet engine parts or the like made from titanium alloys.
Tailored Solutions for Off-Shore Applications by Plazjet Sprayed Coatings
Authors: Ladru F. , Lugscheider E. , Jungklaus H. , Herbst C. , Kvernes I.
Published: May 2021

For very large structures and parts in critical environments, a materials solution often cannot be found by using one material. The specific desired properties for those structures, like stiffness, ductility, high temperature stability, corrosion resistance, etc. are difficult to fulfill with only one material. In this case a solution may be found by using coatings and design their specific properties to replenish each other by their combination. The Thermal Spraying processes offer the necessary flexibility of producing thin to thick, ductile, soft to hard coatings while due to the wide range of process temperatures it is possible to process a wide range of materials, both as coating and structure. In this paper the some recent and important developments in Thermal Spraying to produce coatings for technical demanding structures will be described. These developments consist of High Power Plasma Spraying, powder- and process control development. To ensure process consistency during long spraying times and to apply reproducible coating quality a suitable process control is of great importance and the development of temperature control by Pyrometry and Thermography will be presented. The example will be drawn according to the application of a coating on a ball valve for off-shore and ship diesel engine parts (piston and valve).
The Effect of Tungsten Contamination from the Spray Gun on the Performance of a Thermal Barrier Coating
Authors: Wigren J. , Pejryd L. , Karlsson H.
Published: May 2021

A traditional plasma spray gun consists of an anode and a cathode. During spraying small particles of anode material of either copper or tungsten, depending on the brand of the gun, will be worn off and deposited in the coating. The size and frequency of the particles from a copper anode has generally a dramatic appearance (in the beginning or at the end of its life) whereas a tungsten nozzle normally behaves more randomly during its life. Tungsten particles can therefore be expected anywhere in a plasma sprayed coating. Unfortunately the material properties of tungsten is not very compatible with a thermal barrier coating of partially stabilized zirconia and it is shown that a contamination will cause a catastrophic failure, if located in, for a thermal barrier, a critical region. The behavior of tungsten at elevated temperatures is investigated and clearly show the detrimental effect of tungsten on the life and performance of a thermal barrier coating.
Microstructure Control of Zirconia Thermal Barrier Coatings by Using YAG Laser Combined Plasma Spraying Technique
Authors: Zhou Z. , Eguch N. , Ohmori A.
Published: May 2021

As an ideal zirconia thermal barrier coating, the coating microstructure with the strong bonding among coating particles and with certain amount porosities in the coating without connected porosity is desirable. However, it is difficult for usual plasma-spraying to create a zirconia coating with these characters. In order to obtain an excellent zirconia coating with these characters, we prepared zirconia coating on steel substrate under coated with NiCrAlY alloys by means of a hybrid spraying (that is, YAG laser combined plasma spraying) and studied the effect of this hybrid spraying process and plasma and laser conditions on the microstructure of coating, and further compared the microstructure of the coating in this hybrid spraying with that in post-laser irradiation of as-sprayed zirconia coating. It is known that the microstructure with densification is formed by the post-laser irradiation of as-sprayed coating and that microcracks are newly produced in the process of rapid cooling. However, by using this newly-developed hybrid spraying, the microstructure with partial densification in the coating without connected porosities was formed and cracks which is generally produced in the post-laser irradiation treatment were inhibited completely. In addition, this hybrid spraying can be done without the post-treatment of coating. Furthermore, the coating properties, such as hardness and wear resistance associated with bonding state among the coating particles in the zirconia coating created by this hybrid spraying were improved.
Deposition of Nickel-Aluminum Bronze Powder by Cold Gas-Dynamic Spray Method on 2618 AI for Developing Wear Resistant Coatings
Authors: Bhagat R.B. , Amateau M.F. , Papyrin A. , Conway J.C. , Stutzman B. , Jones B.
Published: May 2021

In an emerging thermal spray process a coating is formed by exposing a metallic or dielectric substrate to a high-velocity jet of solid-phase particles, which have been accelerated by a supersonic gas jet at a temperature much lower than the melting or softening temperature of the particle material. This is known as "Cold Gas-Dynamic Spray" (CGDS) method. Using this method, 2618 Al substrates were coated with nickel-aluminum bronze powders (~100 and ~400 mesh) in an effort to obtain improved wear resistance. The coatings have been examined for their microstructure, hardness, and bond strength. Triple lug shear tests performed on coated panels provided quantitative measurement of the coating/substrate interfacial shear strength. The steady state wear rates were determined using the pin-on-rotating ring test at a pressure of 690 kPa and a sliding velocity of 9 m/s. The wear resistance of the nickel-aluminum bronze coatings is discussed in conjunction with scanning electron microscopy (SEM) examination of the wear tracks and metallography of the polished transverse cross-sections. Though the coatings are not completely free from porosity, they exhibit high interfacial shear strength and wear resistance due to the low-temperature, ballistic impingement of the powders in the cold gas-dynamic spray method. The ~400 mesh powder coating shows higher interfacial shear strength and wear resistance in comparison with the ~100 mesh powder coating.
Arc Voltage Fluctuations as an Indication of Spray Torch Anode Condition
Authors: Duan Z. , Beall L. , Planche M.P. , Heberlein J. , Pfender E. , Stachowicz M.
Published: May 2021

Arc voltage fluctuations of a plasma spray torch are primarily an indication of the movement of the arc attachment inside the anode nozzle. These fluctuation have been shown to influence the deposition process. In order to detect changes in the operating conditions which affect coating quality, a method has been developed for on-line analysis of these fluctuations. Voltage fluctuation have been recorded together with light emission fluctuations and with acoustic emissions from the plasma jet and analyzed on-line using a workstation operating with the LabView environment. Anodes with different wear characteristics have been examined in this study. A clear correlation has been found between the changes in the dominant frequencies of all three signals and the conditions of the torch anode and the coating properties. Appearance of a group of frequency peaks in the 2 to 5 kHz range indicates a more unstable plasma jet and is correlated with anode erosion and increased coating porosity. The results of this study provide us with a convenient method to detect coating deterioration due to anode erosion.
Monitoring of Nozzle Wear during Plasma Spray
Authors: Xi J. , Krishnappa G. , Moreau C.
Published: May 2021

Presented in this paper are the results of preliminary experiments carried out for monitoring of plasma nozzle wear. The experiment system consists of two microphones, one accelerometer and voltage measurement. In the experiment, three nozzles were tested, new, used and worn. The test results show clearly the difference in acoustic characteristics with wear in the nozzle. Some observations obtained from the experiment include: 1) the microphone mounted at 45° may be the best choice for nozzle wear monitoring; 2) voltage signal could be used with the 45° microphone as an indicator for severe nozzle wear; 3) vibration signal is not as sensitive to nozzle wear as 45° microphone and voltage signal; and 4) the 90° microphone is insensitive to nozzle wear.
New Developments in the Plasma Transferred Arc Process
Authors: DuMola R.J. , Heath G.R.
Published: May 2021

The plasma transferred arc process continues to be the coating method of choice for the application of cobalt base alloys onto valve and valve trim. Although new applications have been developed over the years, the process remains largely associated with the application of high performance, highly alloyed powders for relatively small parts or small areas of large parts. The use of the plasma transferred arc process for large volume application has been limited by the robustness and performance characteristics of the equipment and the use of cobalt. A new plasma transferred arc system (power source, torch and process controller) has been developed which allows the application of powder metal alloys at deposition rates of up to 40 pounds per hour. In addition, there has been a development of new non-cobalt powder alloys with excellent mixed corrosion and wear resistance properties. These capabilities have rendered the process technically and economically viable for large and demanding applications in the mining, power utility and steel industries. The new PTA system and the recent developments in powder alloys will be discussed. Reference will be made to specific applications in target industries.
The Ultimate Spray Booth
Authors: Pejryd L. , Wigren J. , Hanner N.
Published: May 2021

Reproducibility is a current challenge for the thermal spray industry. Reproducibility associated problems represent a large cost every year not only in terms of rejections and rework, but also in costs for destructive testing and decreased production flow. Thermal spray coatings are moving in the direction of being considered only as a "band aid" to becoming a design element. One of the prerequisites for such a development is an increase in reproducibility for thermal spray coatings. The purpose of this paper is to outline a vision aiming in the direction of a future "ultimate spray booth", where thermal spraying is as reproducible and reliable as machining, grinding or other production processes. A way to increase reproducibility and reliability in the future spray shop involves utilising major parts of IT - technology. This also includes active co-operation design-production in the pre-spray process. This paper will deal with areas such as: operation drawings and lists through multimedia techniques, education programs for operators and designers through multimedia techniques, CAD/CAM, Off-line programming and simulation, On-line diagnostics of flame (particle diagnostics) and coating (temperature & Acoustic emission measurements), on-line Statistical Process Control and Knowledge Based System techniques.
Laser Processing of Sprayed Powder and Compact Materials
Authors: Vityaz P. , Ivashko V. , Ilyuschenko A.
Published: May 2021

Forming technology of protective properties using concentrated energy flows is based on the possibility of laser radiation firstly to provide high heat flow densities which are necessary for intensive heating on a small part of surface. When effecting metal surface laser radiation reflects from it partially and the rest flow penetrates on small depth. As far as the energy is practically absorbed fully in the surface layer, width 10-6 to 10-7 m, the heat source may be considered as surface one [1]. To harden steel products it is necessary to heat the surface till the temperature of phase transformations. The surface cooling takes place mainly due to heat transfer to a less heated member part. Mathematical modeling thermal processes occuring when local surface parts processing is one of effective means to study this method of materials hardering. However till now the predominant number of works of temperature fields investigation when local processing was done supposing that the ray effects semi-infinite space or the process is considered in a moving coordinates system, connected with the centre of a light spot, that enables to consider a stationary task. Such assumption are true when processing massive parts but give a considerable error when processing small parts [2]. The offered models with the aid of which there is studied the heating process for a sample of parallepiped and cylinder shape come to solving the equation of thermal conductivity with considerably nonlinear coefficients. When surface processing with continuity laser, the ray is focused perpendicularly to the sample surface. The period of light spot contact with the surface is estimated from the speed of its travel on the scanned surface. Before the test the product is subjected to special processing reducing the energy loss due to reflection.
Mathematical Modeling of a Free Plasma Jet Discharging into Air and Comparison with Probe Measurements
Authors: Bolot R. , Imbert M. , Coddet C.
Published: May 2021

Plasma spraying process modeling is useful to understand physical phenomena and to decrease the number of experiments. In this paper, a study of the external plasma jet is proposed: the PHOENICS™ CFD code was used with a 2D axisymmetrical geometry and a standard K-ε turbulence model. In a first step, thermodynamic and transport properties were calculated from chemical equilibrium composition, thermodynamic derivatives and kinetic theory of gases. Local Thermodynamic Equilibrium (LTE) was assumed for both plasma and surrounding gases. The proposed numerical results were computed for comparison with temperature measurements realized by Brossa and Pfender in the case of an argon plasma jet discharging into air, using enthalpy probes. The predictions were found reasonably accurate. The influence of the surrounding gas nature was also verified as the validity of the parabolic assumption.
Investigation of the Long-Term Stability of Plasma Spraying by Monitoring Characteristics of the Sprayed Particles
Authors: Leblanc L. , Gougeon P. , Moreau C.
Published: May 2021

In plasma spraying temperature and velocity of the sprayed particles are among the most important parameters influencing the microstructure and properties of the deposited coatings. However, the sprayed particle state is influenced by uncontrollable parameters such as the wear state of the electrodes. In order to investigate the influence of the electrode wear state on sprayed particles, a long-term experiment was conducted during which on-line measurements of plasma sprayed yttria-zirconia powder were performed. Results show that even though input parameters were kept constant during the experiment the state of the sprayed particle changed significantly and coatings prepared at different spraying times have different microstructures and can have different properties. However, by changing some input spray parameters it was possible to retrieve the initial sprayed particle state and coating microstructure.
Measurement Technology for Inflight Particle Diagnosis in Plasma Spraying
Authors: Schütz M. , Barbezat G.
Published: May 2021

A new measurement technology in plasma spraying has been established at SULZER METCO AG, Switzerland. Based on the principle of C. Moreau, CNRC, it is now possible to measure surface temperature and velocity of melted particles during the flight in a plasma flame. Since temperature and velocity are two of the most important parameters for plasma spraying processes and coating characteristics, the knowledge and control of these parameters offers new methods and assistance in the development of coating solutions. The object of this paper is to outline some important measurement results, to show correlations to coating characteristics and to demonstrate measurement applications in an industrial environment.
Diagnostic Development for Control of Wire-Arc Spraying
Authors: Sheard J. , Heberlein J. , Stelson K. , Pfender E.
Published: May 2021

This research has focused on characterization of the wire arc spray process with the goal of achieving improved process controls. Arc voltage and current traces have been analyzed on-line using an oscilloscope and a personal computer with LabView software. The characteristic features of the arc voltage fluctuations are correlated with the molten metal droplet formation process using a high speed Laser Strobe video system operating in synchronization with the oscilloscope trigger. Voltage minima occur when larger globules of molten metal leave the wire tip. Analysis of the voltage fluctuations indicate that they are neither random nor periodic, and that they can be described based on chaos theory. This approach may be used for achieving a further understanding of the dynamic nature of the process, and for the development of control algorithms.