bluuebunny/crossref_metadata_2025 huggingface dataset:
Locating Flowing Conduits in Karst Using Amplitude-based Passive Seismic Location Method
Authors: Karbala Ali Haleh , Bean Christopher
Published: September 2022

The aim of this study is to develop methods for directly detecting energetic groundwater flow in sub-surface conduits through passive seismic applications, by detecting the small ground vibrations (seismic microtremor) that flowing water in the sub-surface may generate. This is in contrast to the current ‘traditional’ approach of attempting to actively image the conduits using geophysical and other methods, in order to determine the geometry of flow paths. The imagery of conduits in karst is a very difficult problem and determining if they contain flowing structures is also a very significant challenge using traditional methods, which is the motivation for developing a new approach to the problem. We observed that subterranean flow-related micro-tremor in karst also appears as persistent frequency bands on the spectrograms that vary with time and seismic station location with respect to the conduit. This persistent frequency is different than the soil resonating frequency and relates to the subterranean water flow in the conduits. Application of an Amplitude Location Method (ALM) to the linear profiles clearly delineated the conduit as the source of the micro-tremor in experiments conducted in Ireland. We also discovered a secondary (previously unknown) tributary at one site which demonstrates that this method has the potential to delineate complex subsurface flow structures. We applied the Amplitude Location Method (ALM) to active sledgehammer shots successfully locating the hammer shots. This validates the approach that we are taking and gives confidence in both the concepts behind and implementation of the methodology.
Attention Is Not the Solution: Experiences of University Students With ADHD With Remote Learning
Authors: Dobrowolski Sonja , Watson Steven James
Published: September 2022

education and wellbeing. Since symptoms of ADHD affect the individual’s attention and various skills such as time management, it was expected that remote learning may introduce new challenges as well as benefits due to novel opportunities offered by technology. Semi-structured interviews were conducted with seven university students from one city in the Netherlands and one student from Germany. The collected data was analysed with thematic analysis. Remote education was generally perceived as having a negative influence on the student’s university experience and wellbeing. Key factors mentioned included reduced social interaction, disrupted schedules and increased procrastination, resulting in time management issues, reduced external pressure and finally reduced performance. However, the interviewees found recorded lectures and the availability of all relevant information in one document as well as social support as beneficial. The interviewees themselves mentioned several suggestions concerning improvements for future university education, including a support system from universities, which would offer study groups and information on organisation skills. Furthermore, interactivity during lectures could be improved and mandatory attendance may increase external pressure. The findings of this study suggest that remote education may introduce new barriers for students with ADHD. A major strength of this study was the participant engagement which led to target-group centred suggestions. Future research should address the suggestions offered in this research and explore intervention for social integration in remote settings and reducing stigma surrounding received support.
Genetic Confounding in Bullying Research: Causal Claims Revisited
Authors: Vrijen Charlotte , Nolte Ilja Maria , Oldehinkel Albertine , Veenstra René , Kretschmer Tina
Published: September 2022

Bullying research has shown repeatedly that victims of bullying have an increased risk for later internalizing problems and bullies have an increased risk for later externalizing problems. Bullying involvement is often, either explicitly or implicitly, presented as part of a causal mechanism for maladjustment. However, genetic vulnerability may confound the reported associations. This study examined to what extent genetic vulnerability can account for the reported associations between bullying involvement (age 11-14) and later internalizing and externalizing problems (age 16), using data from the TRacking Adolescents' Individual Lives Survey (n = 1604). Because polygenic scores capture only a fraction of the total genetic effect, they were extrapolated to the size of SNP and twin heritability estimates to examine genetic confounding while controlling for (hypothetic) polygenic scores that capture the genetic effect fully. Genetic vulnerability for internalizing and externalizing problems confounded, respectively, the association between bullying victimization and later internalizing problems, and the association between bullying perpetration and later externalizing problems. This study showcases a method that can be broadly used to assess the magnitude of genetic confounding. Caution is warranted in interpreting particularly the less straightforward extrapolations of polygenic scores to the size of twin heritability estimates.
Exploring provider roles, continuity, and mental models in cirrhosis care: A qualitative study
Authors: Barber Tanya , Toon Lynn , Tandon Puneeta , Green Lee A
Published: September 2022

BACKGROUND: Advanced cirrhosis results in frequent emergency department visits, hospital admissions and readmissions, and a high risk of premature death. We previously identified and compared differences in the mental models of cirrhosis care held by primary and specialty care physicians and nurse practitioners that may be addressed to improve coordination and transitions in care. The aim of this paper is to further explore how challenges to continuity and coordination of care influence how health care providers adapt in their approaches to and development of mental models of cirrhosis care. METHODS: Cross-sectional formal elicitation of mental models using Cognitive Task Analysis. Purposive and chain-referral sampling took place over 6 months across Alberta for a total of 19 participants, made up of family physicians ( n = 8), specialists ( n = 9), and cirrhosis nurse practitioners ( n = 2). RESULTS: Lack of continuity in cirrhosis care, particularly informational and management continuity, not only hinders health care providers’ ability to develop rich mental models of cirrhosis care but may also determine whether they form a patient-centred or task-based mental model, and whether they develop shared mental models with other providers. CONCLUSIONS: The system barriers and gaps that prevent the level of continuity needed to coordinate care for people with cirrhosis lead providers to create and work under mental models that perpetuate those barriers, in a vicious cycle. Understanding how providers approach cirrhosis care, adapt to the challenges facing them, and develop mental models offers insights into how to break that cycle and improve continuity and coordination.
What is purposive interpretation?
Authors: Weinrib Jacob
Published: September 2022

Purposive interpretation leads a double life. As a matter of constitutional practice, it forms the doctrine through which courts in Canada and around the world determine the concrete protections that abstract constitutional rights afford. However, as a matter of constitutional theory, purposive interpretation is routinely rejected as either an empty phrase that offers no alternative to established theories of constitutional interpretation or a dangerous doctrine that provides no basis for distinguishing between justified and unjustified interpretations of constitutional rights. This essay formulates a conception of purposive interpretation that is not vulnerable to these objections. The purposive approach to the interpretation of constitutional rights follows from a set of ideas about how legal interpretation differs from interpretation more broadly, how constitutional interpretation differs from interpretation in other legal domains, and how constitutional interpretation constrains both the purposes it attributes to particular provisions and the application of those purposes to particular contexts. My aim is to show that these ideas fit together in a coherent doctrinal whole that is neither empty nor dangerous. Purposive interpretation is not empty because it offers a genuine alternative to the presuppositions and structure of opposing interpretive paradigms. Purposive interpretation is not dangerous because it provides a principled set of resources for distinguishing between justified and unjustified interpretations.
Radiological psoas muscle parameters as a reliable tool for detection of sarcopenia and prediction of short-term survival in liver cirrhosis
Authors: Motsiuk V. M. , Pentiuk N. O.
Published: September 2022

Loss of skeletal muscle mass or sarcopenia is associated with the development of complications and mortality in patients with liver cirrhosis (LC). Skeletal muscle index (SMI) is the most validated parameter of sarcopenia in clinical studies, but its evaluation is difficult in routine clinical practice. The purpose of the study was to assess the diagnostic concordance between different radiologic skeletal muscle parameters and their relationship with a short-term survival of LC patients. The study involved 147 LC patients, including 90 males and 57 females (55.51±0.97). LC Class A according to Child-Turcotte-Pugh (CTP) was diagnosed in 23 patients, class B in 51 patients, and class C in 73 patients. 50 patients died from LC complications during the follow-up period (489 (306 – 637) days). Skeletal muscle index (SMI), psoas muscle mass index (PMI), and transversal psoas muscle thickness (TPMT) were calculated using the computed tomography at L3 level. The statistical data was processed using the SPSS22 software (© SPSS Inc.). PMI and TPMT were found to be objective parameters of sarcopenia in LC patients having stable diagnostic concordance with SMI (r Spearman’s 0.734, 0.649, p˂0.001; k Cohen’s 0.727, 0.643, p˂0.001, respectively). The use of all three parameters allowed to reveal more patients with a reduced skeletal muscle mass. Sarcopenia was diagnosed in 54.9 % of CTP B patients, 86.3 % of CTP C patients, and was associated with an elevated incidence of ascites, hydrothorax, hepatic encephalopathy, and hypoalbuminemia. Sarcopenic patients were found more likely to have an alcohol-related etiology than viral one (HBV, HCV). The overall survival of patients with low SMI, PMI and TPMT was significantly lower according to Kaplan-Meier analysis. SMI, PMI, and TPMT were independent predictors of LC-associated mortality (HR 2.66, 2.19, 2.21, respectively, p˂0.05) in Cox proportional hazards regression. At least one of the three decreased radiologic skeletal muscle mass parameters was associated with the highest risk of fatal LC complications (HR 3.65, p=0.021). Therefore, the psoas muscle dimensions were considered a reliable tool for detection of sarcopenia and prediction of short-term survival in LC.
Correlation between aortic root dimensions and biometric indicators in coronary heart disease
Authors: Pidvalna U. Ye.
Published: September 2022

Aortic root requires preliminary preoperative analysis for coronary artery bypass graft (CABG) in coronary heart disease (CHD). The dimensions of the aorta correlate with anthropometric indicators. The purpose of the study: to establish the relationship between sinuses of Valsalva height, coronary artery ostia height and biometric parameters (age, height, weight, body surface area and body mass index) in men with CHD using computed tomography. Research materials and methods include contrast-enhanced computed tomography images of the aorta of men with verified CHD. According to growth parameters, division into 2 groups was made. The sinuses of Valsalva height and right and left coronary artery ostia height were measured. Clinical data were analyzed: age, height, body weight, body surface area (BSA) and body mass index (BMI). Statistical analysis: Student's t-test, Kendall's rank correlation method, Pearson's linear correlation, Fisher's multifactorial regression analysis. Analysis of the results of computed tomography of 30 men with CHD (average age 60.80±10.63 years) showed that the average values of the three sinuses of Valsalva height were approximately at the same level. The results of the Pearson linear correlation evaluation showed the absence of a proven relationship between biometric indicators and morphometric data according to CT in men with CHD (p>0.05). Multifactor regression analysis proved the inverse significant influence of weight and the direct significant influence of BMI and BSA on the dependence of left coronary artery ostia height. The multiple correlation coefficient was R=+0.55, with p=0.023, SEE=2.74. Prediction of the level of left coronary artery ostia height in men with CHD was carried out with confirmation of the constructed model. In the first group of short men (n=11) with CHD (average age 60.11±12.63 years, height 1.677±0.023 m), an inverse correlation between height and left coronary artery ostia height (τb=-0.56, p=0.034). Reliable direct relationships between the left coronary artery ostia height parameter and several anthropometric indicators were established: with weight – a direct strong relationship (τb=+0.72, p=0.007), with BMI – a direct relationship of medium strength (τb=+ 0.67, p=0.008), with BSA – average strength direct connection (τb=+0.58, p=0.023). The relationship between the value of the right coronary artery ostia height and the BSA indicator – the inverse of the average strength correlation (τb=-0.51, p=0.046) was proved. Relationships between morphometric parameters and age were not proven. Thus, in men with CHD, left coronary artery ostia height correlates with weight, BMI, and BSA. In short men with CHD, there is an inverse relationship between left coronary artery height and height; direct relationships with weight, BMI and BSA.
Effect of Microplasma Spray Conditions on Structure, Phase Composition and Texture of Hydroxyapatite Coatings
Authors: Borisov Y. , Voynarovych S. , Kislitsa A. , Borisova A. , Karpetz M. , Tunik A.
Published: September 2022

Hydroxyapatite (HA) coatings were deposited onto titanium alloy substrate using the microplasma spray (MPS) technique. The fractional-factorial experiment design method was employed to study the relationships between MPS parameters (amperage, plasma gas flow rate, spray distance and powder rate) and characteristics of HA coatings (microstructure, morphology, content of crystalline and amorphous phases, texture). Influence of coating thickness and the deposited coating heat treatment were evaluated also. The results show some peculiarities of HA coating formation in conditions of microplasma spraying process.
Introduction of Bioactivity to Plasma Sprayed TiO2 Coating with Nanostructured Surface by Post-Treatment
Authors: Liu X.Y. , Zhao X.B. , Ding C.X.
Published: September 2022

In this work, a TiO2 coating with nanostructured surface was obtained through plasma sprayed nano-sized TiO2 powder. Its bonding strength onto Ti-6Al-4V substrate is high up to 38 MPa. At same time, we have successfully improved the bioactivity of plasma sprayed TiO2 coating with nanostructured surface using hydrogen ion implantation and UV illumination. Bone-like apatite can form on the surface of the post-treated TiO2 coatings after they are soaked in simulated body fluid for a period of time. Introduction of surface bioactivity (bone conductivity) to plasma-sprayed TiO2 coatings which are generally recognized to have excellent biocompatibility and corrosion resistance as well as high bonding to titanium alloys makes them more superior than many current biomedical coatings such as plasma-sprayed hydroxyapatite.
Bonding Strength Investigation of Plasma-sprayed HA Coatings on Alumina Substrate with Porcelain Intermediate Layer
Authors: Yang Y.C. , Choun C.S. , Chang E.
Published: September 2022

Hydroxyapatite (HA) has recently been used as a bone substitute in orthopedic and dental surgery applications, owing to its excellent biocompatibility. However, the poor mechanical properties of HA limit the material’s application in the loading condition. In this study, HA was coated onto the surface of alumina substrate, with a view to overcome the poor mechanical properties of HA and the biocompatibility of alumina. Improvement of the bonding strength of HA coatings to alumina substrate was attempted by adding a bond coat of porcelain via plasma-spraying and by post heat-treatment. HA-50wt% porcelain and pure porcelain were used to manufacture two kinds of bond coat before HA coating, and then all the specimens were heat-treated at 750°C, 800°C, 850°C, 900°C for 0.5 hours. The results shows that the bond strength between HA coating and Al2O3 substrate could be improved by employing the porcelain as the bond coat after the heat treatment. The strengthening mechanisms of the two systems are discussed.
The Influence of Particle Morphology on In-flight Particle Velocity in Cold Spray
Authors: Fukanuma H. , Ohno N. , Sun B. , Huang R.
Published: September 2022

Cold spray is a relatively recent spray coating technology in which metal or alloy particles are plastically deformed by the kinetic energy of the particles accelerated in a supersonic gas flow through a convergent-divergent nozzle before hitting the substrate. The particle velocity at impact onto the substrate is a key factor in determining the characteristics of the cold spray deposit. Therefore, various studies have been carried out on particle acceleration with the aim of obtaining faster cold spray particle velocities. Mathematical modeling has also been carried out on spherical particle acceleration in a supersonic gas flow in a Laval nozzle. To understand better how a non-spherical particle behaves in a supersonic gas flow, experiments were carried out on the effect of morphology on particle acceleration in cold spray. Two types of powder morphology were used for the experiment, one was spherical and the other was angular and jagged. The particle size distributions were almost the same. In-flight particle velocities of the spherical and angular particles were measured with a DPV-2000. It was found that the particle morphology greatly influenced the in-flight particle velocity and deposit efficiency.
Cold Sprayed Discontinuously Reinforced Aluminum (DRA)
Authors: Haynes J. , Pandey A. , Karthikeyan J. , Kay A.
Published: September 2022

Discontinuously reinforced aluminum (DRA) has many attractive mechanical and physical properties. Discrete hard particles such as B4C have been added to aluminum alloys, such as 6061, to add strength and stiffness for an improved performance. Traditionally, these particles are introduced in melt additions and extruded or made into preforms and cast. These ceramic particles are also added in aluminum through a powder metallurgy process resulting in extrusion or forging. Inhomogeneous distribution of these particles in casting results in inferior properties and also it is difficult to produce preforms with high volume fraction materials. While wrought properties can be achieved in the powder metallurgy approach, extrusion directionality of the process introduces anisotropic properties. Though thermal spray has been used to produce DRA coatings, it has been observed that the melting and re-solidification of the aluminum matrix material as well as reaction with potential substrates such as copper is of concern. Since cold spray does not melt the feedstock material, it is ideally suitable for producing DRA coatings. Boron carbide particles and 6061 aluminum alloy were used as reinforcing and matrix material respectively. Experimental studies were carried out to optimize the raw material characteristics, DRA powder preparation technique and spray parameters, and using these optimized parameters, dense and strong coatings and free-forms were produced. Proper selection of the particle size distribution of the matrix and reinforcing materials, wet blending them and subsequent drying yielded the required spray feedstock. Optimization of the spray parameters resulted in strong, dense and well-bonded coatings with acceptable deposition efficiency and deposition rate values. Post spray heat treatments were carried out to retrieve the ductility of the specimens. A series of mechanical property measurements were carried out on the as-sprayed and heat treated specimens. Results of these studies were analyzed to evolve a preliminary model of the DRA structures and establish the feasibility of cold spray production of DRA coatings and free-form structures.
Comparison Between Coatings from two Different Copper Powders: Mechanical Properties, Hardness and Bond Strength
Authors: Kairet T. , Di Stefano G. , Degrez M. , Campana F. , Janssen J-P
Published: September 2022

Cold sprayed copper coatings have been widely studied but the effect of substrate properties and spraying conditions on the bond strength still needs further investigations. Using nanoindentation, it is possible to compare the effect of spray parameters on the change in hardness of the coating due to the difference in size distribution of the powder. Deposition of 2 copper powders on aluminium and Ta6V substrates has been done at different stagnation temperatures and pressures using nitrogen as process gas. Hardness profiles show how the speed of the particles induces shot peening effects on the surface. The interaction between the hot gas jet and the surface may modify the hardness profiles. The effect on the substrate hardness has also been investigated.
Influence of Powder Type and Properties on Ceramic Layer Deposition by Cold Spraying
Authors: Veräjänkorva S. , Lagerbom J. , Vuoristo P.
Published: September 2022

Ceramic deposition produced by cold spraying was studied for functional surface applications. Several oxide materials and metal matrix composite (MMC) powders were used to model the behavior of ceramic powder deposition on soft metallic substrate materials. The manufacturing method, density and size of ceramic powders and matrix material of MMC were found to affect the deposition on soft metal surfaces. The powder density influences the deposition greatly and it is also an important factor in finding an ideal powder particle size. Fusing and crushing the powder can be a good manufacturing method if the fusion does not cause phase transformations in the powder. In that case, spray drying with sintering can give better results. Spraying parameters, such as the process gas parameters and the effect of multiple sweeps of the torch were also studied to optimize the amount of deposition. Cold spraying was found to be a promising manufacturing method for functional surfaces.
Mechanisms Resulting in Improved Ductility of Cold Spray Coatings after Annealing
Authors: Hall A.C. , Williamson R.L. , Hirschfeld D.A. , Roemer T.J.
Published: September 2022

An earlier study reported an investigation of the mechanical properties of cold sprayed aluminum and the effect of annealing on those properties. In that study, cold spray coatings approximately one centimeter thick were prepared using three different feedstock powders: Valimet H-10, Valimet H-20, and Brodmann Flomaster. ASTM E8 tensile specimens were machined from these coatings. Each material was tested in two conditions: as-sprayed and after a 300°C, 22 hour air anneal. The as-sprayed material showed a high ultimate strength and low ductility, < 1% elongation. The annealed samples showed a reduction in the ultimate strength but a dramatic increase in ductility, up to 10% elongation. Microstructural examinations and fractography clearly showed a change in the fracture mechanism between the as-sprayed and annealed material, but insufficient data was available to conclusively explain the ductility increase at that time. Since then, Kikuchi mapping of the Valimet H-10 material in the as-sprayed and annealed conditions has been conducted. Kikuchi mapping allows indexing of grains, identification of grain boundaries, and phase identification using backscattered diffraction patterns in an SEM. The data shows that significant recrystallization within the splats upon annealing has occurred. No significant crystal growth across splat boundaries is observed. The data demonstrate that the mechanism of ductility increase in annealed cold spray deposits is recrystallization of the base aluminum material.
Modeling the Restrike Mode Operation of a DC Plasma Spray Torch
Authors: Moreau E. , Chazelas C. , Mariaux G. , Vardelle A.
Published: September 2022

A key aspect of the operation of conventional non-transferred Direct Current (DC) plasma torches is the random motion of the arc inside the nozzle. Various plasma gun designs have been developed to limit the arc fluctuations without increasing the heat load to the anode wall that results in surface erosion and anode wear. However, construction of these plasma torches is highly complex while the conventional DC plasma torch consists of small number of elements and is simple to manufacture and maintain. A better understanding of the behavior of the arc-anode attachment and the way it depends on the operating conditions may help to design and operate conventional plasma torches so that the fluctuation of the time-voltage and therefore the time-enthalpy variation, is as low as possible with a fluctuation frequency adapted to the time characteristic of the powder particles in the plasma jet. This study deals with a three-dimensional (3-D) time-dependent modeling of the arc and plasma generation in such a torch operating under the so-called “restrike” mode. The latter is characterized by rather large voltage fluctuations, corresponding to a broad range of conditions used in the manufacturing of plasma coatings. The mathematical model is based on the simultaneous solution of the conservation equations of mass, momentum, energy, electric current and electromagnetism equations. It makes it possible to predict the effect of the operating parameters of the plasma torch on the motion of the anode root attachment over the anode surface, and the time-evolution of arc voltage and flow fields in the nozzle.
Modelling of Motion and Heating of Powder Particles in Laser, Plasma and Hybrid Spraying
Authors: Borisov Yu. , Bushma A. , Krivtsun I.
Published: September 2022

Mathematical models for simulation of motion and heating of fine ceramic particles in plasma and laser spraying, as well as under conditions of a new technological process, i.e. hybrid laser-plasma spraying, are proposed. Trajectories, velocities and temperature fields of fine SiO2 particles being sprayed using the argon plasma jet, CO2-laser beam and their combination have been calculated. It is shown that the space-time distribution of temperature in spray particles greatly depends upon the spraying method.
Advanced Coatings on Furnace Wall Tubes
Authors: Matsubara Y. , Sochi Y. , Tanabe M. , Takeya A.
Published: September 2022

Nickel based self-fluxing alloy coating extends the service life of furnace wall tubes at waste incineration plants due to its excellent corrosion resistance and heat resistance. With our system, fusing of such coatings is performed by induction heating, which offers improved efficiency and reliability of products. Compared with conventional plasma, flame, and HVOF thermal-sprayed coatings, induction-fused coatings provide a far stronger metallurgical bond at the interface, while minimizing the inclusion of pores. In addition, the tubes are less costly than those with welded coatings, and the process reduces the distortion of the products, facilitating easier final assembly. A successful experimental application of 11 units (four, six-meter pipes per unit) revealed virtually no corrosion on the exposed surfaces, and showed an improved water heating efficiency over that of the original mortar-coated tubes. Over 200 such units are now being employed in four incinerators in Taiwan, and further installations are in progress.
Low Thermal Conductivity Coatings for Gas Turbine Applications
Authors: Markocsan N. , Nylén P. , Wigren J. , Li X.-H.
Published: September 2022

Plasma spraying of thermal barrier coatings (TBCs) on gas turbine parts is widely used today either to enable higher turbine inlet temperatures with consequent improvement of combustion efficiency or to reduce the requirements for the cooling system and increase components life-time. Development of low conductivity TBCs, which allows us to further increase gas turbine efficiency and availability, is an ongoing challenge. In order to get low thermal conductivity values an experimental program was conducted. Two zirconia powders were used for coating deposition: yttria partial stabilised zirconia (YPSZ) and dysprosia partial stabilised zirconia (DyPSZ). Microstructure evaluations were performed to evaluate the influence of the spraying parameters on the coating morphology and porosity level. Two methods were utilised to evaluate the coatings thermal conductivity: Laser Flash (LF) and Transient Plane Source (TPS). A comparison between the two methods was made as well as a correlation study between coating microstructure/composition and thermal conductivity (TC).
Corrosion Resistance of SS304 Substrate Coated with Al2O+ZrO2 Composite Coatings Prepared by Gas Tunnel Type Plasma Spraying
Authors: Kobayashi A. , Zhang J.
Published: September 2022

In this paper, composite thermal barrier coatings (TBCs) of Al2O3+ZrO2 are deposited on SS304 stainless steel substrates by gas tunnel type plasma spraying. The resultant coating samples prepared with different Al2O3+ZrO2 mixing ratio and thickness are compared in corrosion resistance. A potentiostatic anodic polarization corrosion tester is used to get the corrosion characteristics of coated samples to measure their corrosion resistance. From the polarization curves, corrosion potential and deactivated corrosion current density are obtained and analyzed corresponding to the microstructure of the coatings. The results show that the higher alumina content and thicker coatings, the better the corrosion resistance, which is attributed to the diffusion resistance of coating layers to corrosion reaction. The coating microstructure is characterized using an optical microscope imaging system and measured the coating thickness and porosity. The coating porosity and thickness are believed to be the important factors for the variation on the corrosion behavior of Al2O3+ZrO2 coated SS304 stainless steel substrates.
Thermo-Mechanical Behavior of Nanostructured Plasma Sprayed Zirconia Coatings
Authors: Soltani R. , Garcia E. , Coyle T.W. , Mostaghimi J. , Lima R.S. , Marple B.R. , Moreau C.
Published: September 2022

Retaining non-melted nano-particles of zirconia in nanostructured coatings has been a challenge in the past. Recently an air plasma spray process was developed to produce coatings which retain up to 30-35% by volume non-melted particles, resulting in a unique structure. The creep/sintering behavior of such thermal barrier coatings deposited from nanostructured feedstock has been measured and compared with deposits produced from hollow sphere powder (HOSPTM). Both feedstocks contain 6-8wt% Y2O3 as stabilizer. Flexure and compression creep testing were conducted under several different loads and temperatures to obtain creep exponents and parameters.
Optical Properties of Yttria-Stabilized Zirconia Plasma-Sprayed Coatings
Authors: Debout V. , Vardelle A. , Abélard P. , Fauchais P. , Meillot E. , Bruneton E. , Schelz S. , Branland N.
Published: September 2022

The objective of this study is to establish relationships between the optical properties of yttria-stabilized zirconia (YSZ) plasma-sprayed coatings and their microstructure to improve YSZ thermal barriers. So, coatings with significant microstructural differences were manufactured and their hemispherical reflectance and transmittance were investigated over the 0.25-20µm wavelength range. However as plasma-sprayed coatings are heterogeneous materials, they exhibit optical properties different from those of homogeneous ones. Indeed, the pores and grain boundaries act as scattering centers and cause modifications in optical properties that are closely linked both to intrinsic properties of materials and microstructural characteristics. Therefore, the extinction coefficient which describes the decrease in light intensity due to the light absorption and diffusion processes in the matter, was determined by using the Kubelka-Munk two-flux model. The absorption and diffusion coefficients were infered from the comparison between the experimental data and model predictions of reflectance and transmittance.
HVOF-Applied WC-Co-Cr as a Hard Chrome Replacement for Landing Gear
Authors: Evans B. , Panza-Giosa R. , Cochien Brikaras E. , Maitland S.
Published: September 2022

The Airbus A380 program marked the Goodrich Landing Gear introduction of High Velocity Oxygen Fuel (HVOF) applied tungsten carbide cobalt chrome (WC-Co-Cr) coating as a replacement coating for electrolytic hard chrome. HVOF is a new coating technology when applied to aircraft landing gear so specifications for coating application, finishing, powder and supplier qualification were developed to reflect the unique function of landing gear components. Since the materials, sizes and shapes of landing gear components are dissimilar to other aerospace parts currently HVOF sprayed, the capabilities of each spraying and grinding supplier needed careful assessment. Both suppliers and internal customers required training on the requirements specific to landing gear. This paper will discuss the development of HVOF specifications specific to aircraft landing gear, the methods developed for qualifying HVOF suppliers, and some challenges encountered when introducing HVOF-applied WC-Co-Cr as a hard chrome replacement.
Microstructure and Properties of Thermally Sprayed Al-Sn based Alloys for Plain Bearing Applications
Authors: Marrocco T. , Driver L.C. , Harris S.J. , McCartney D.G.
Published: September 2022

Al-Sn plain bearings for automotive applications traditionally comprise a multilayer structure. Conventionally, bearing manufacturing involves casting the Al-Sn alloy and roll¬bonding to a steel backing strip. Recently, high velocity oxy- fuel thermal spraying has been employed as a novel alternative manufacturing route. The present project extends previous work on ternary Al-Sn- Cu alloys to quaternary systems, which contain specific additions for potentially enhanced properties. Two alloys were studied in detail, namely Al-20wt.%Sn-lwt.%Cu-2wt.%Ni and Al-20wt.%Sn-lwt.%Cu-7wt.%Si. This paper will describe the microstructural evolution of these alloys following HVOF spraying onto steel substrates and subsequent heat treatment. Microstructures of powders and coatings were investigated by scanning electron microscopy and phases identified by X-ray diffraction. Coating microhardnesses were determined in both as-sprayed and heat treated conditions and differences related to the microstructures which developed. Finally, the wear behaviour of the sprayed and heat treated coatings in hot engine oil was measured using an industry standard test and compared with that of conventionally manufactured Al-Sn bearings.
Finite Element Analysis of Residual Stress Generated by the HVOF Process
Authors: Stokes J. , Looney L.
Published: September 2022

Due to the recent advances in thermal spraying technology, considerable research emphasis has been placed on the development of models capable of predicting deposition mechanisms at various stages during the process. In order to gain a deeper knowledge of the mechanisms involved in thermal spraying, it is necessary to isolate the factors affecting these constitutive properties (for example residual stress generation) and in doing so quantify the effect of the individual factors. Finite Element Analysis (FEA) is used in the present research to predict the residual stress generated in a WC-Co deposit produced via the HVOF process. The model is compared to an analytical technique and validated experimentally, the result of which provides a thermomechanical modelling procedure with an accuracy greater than 80% of that found experimentally. Combining FEA techniques with analytical and experimental results will enhance the understanding of residual stress in thermal spray techniques.
Development and Characterization of Nanostructured Iron-Based Coatings by HFPD and HVOF
Authors: Parco M. , Fagoaga I. , Bobzin K. , Lugscheider E. , Zwick J. , Hidalgo G.
Published: September 2022

Structuring coating materials in the nanoscale can significantly enhance the performance of Fe-based coatings. Nanostructured steel coatings with a very high hardness, the strength of carbon-based fibers and a corrosion resistance superior to nickel-based super alloys are currently commercially available. This work deals with the development of wear resistance nanostructured coatings using a commercial steel powder by high frequency pulse detonation. Results concerning the deposition of this powder using two different high velocity oxy-fuel spray systems are presented for comparison. The process parameters were optimized on the basis of the achieved coating features hardness, thickness, porosity and surface roughness. The microstructure of the coatings achieved with the different systems as well as the resulting adhesion and cavitation erosion resistance are compared. These results are also compared with the performance of standard WC-CoCr coatings.
Study on Properties and Microstructure of Nanostructured Ceramic Composite Coatings Prepared by High-Velocity Arc Spraying
Authors: Li Z.x. , Wang J.P. , Cui L.
Published: September 2022

Nanostructured ceramic composite coatings were deposited by high velocity arc-spraying. It was found that metal-clad powders exhibited better thermal conductivity and atomization capabilities when compared to mechanically blended powders. The Surface Rockwell hardness values of the nanostructured ceramic composite coatings were similar to those of the conventional coatings (from 66.7 to 72.8), however, the bond strength of the nanostructured coatings measured via the GB9796-88 standard reached values of 60 MPa, whereas the bond strength of the conventional coatings stayed below 40 MPa. The microstructure of the high velocity arc sprayed nanostructured ceramic coatings was analyzed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The coatings exhibited the typical lamellar structure of thermal spray coatings. The surface of the nanostructured composite coatings was smoother than that of the conventional ones, and their microstructures were denser, showing lower levels of impurity.
Study on the Influences of DPV-2000 Software Parameters on the Measured Results in Cold Spray
Authors: Huang R.Z. , Sun B. , Ohno N. , Fukanuma H.
Published: September 2022

The velocity of particles prior to the impact on the substrate surface is a very important factor that determines the deposition characteristics and coating quality in cold spray. The DPV-2000 system is an on-line diagnostic system that simultaneously measures the velocity, temperature and diameter of thermally sprayed particles. In the present study, the DPV-2000 system was employed to measure the velocity and diameter of cold sprayed particles. The effects of pre-setting software parameters of the DPV-2000 system on the measured particle velocities were investigated. The experimental results showed that the pre-setting values of the software parameters produced a significant influence on the accuracy of measured results.
Method for Quantitative Evaluation of Carbon and Carbide Loss during HVOF Spraying of Cr3C2-NiCr Coating
Authors: Ji G.-C. , Li C.-J. , Wang Y.-Y. , Li W.-Y. , Yang G.-J.
Published: September 2022

For high velocity oxy-fuel (HVOF) sprayed Cr3C2-NiCr coating, an experimental method to evaluate the carbon and carbide loss of the particles in the stages of both in-flight and impacting on a substrate was proposed. The carbon loss in these two stages was determined by comparing the carbon content in the starting powder, the collected powder sprayed into water and the coating deposited on the substrate. The carbide loss caused by carbide rebounding, dissolving into NiCr matrix and oxidizing in-flight can be determined by evaluating quantitatively the carbide content of the collected powder and the deposited coating. According to the experimental results, it was revealed that the rebounding off of large carbides during particle impact on the substrate is mainly responsible for the carbon loss. The carbide rebounding off and dissolving are two main reasons for the carbide reduction in the coating. The carbon and carbide loss caused by oxidizing during the in-flight of particles is very limited.
Reactively Thermal Sprayed Composite Coatings with Different Particle Temperature and Velocity
Authors: Tsunekawa Y. , Hamanaka I. , Hirose M. , Okumiya M. , Ozdemir I.
Published: September 2022

Reactively thermal sprayed coatings based on in-process reactions during flight and after impingement offer superior properties compared with conventional coatings because it has in-situ formed fine and uniformly dispersed stable hard phases. In the present work, composite powder composed of plated nickel, fine SiO2 particulates and Al-Si-Mg core particles with water glass binder (SiO2/Ni/Al-Si-Mg) was deposited onto an aluminum substrate to fabricate composite coatings by using HVOF (high velocity oxyfuel), RF (radio frequency) and DC (direct current) plasma spraying methods. The amount and constituents of phases formed during reactive thermal spraying were found to be different depending upon the methods used where in-process reactions differently proceed. Consequently, reactively sprayed composite coatings mainly consist of Mg2Si, MgAl2O4, NiAl3 and Al-Si matrix through the exothermic reaction of SiO2 and nickel with molten Al-Si-Mg alloy. The depletion of magnesium in the composite powder is responsible for the obtained lower hardness of composite coatings sprayed by RF plasma spraying which offers the highest molten droplet temperature.
Effects of Coating-Substrate Properties and Adhesion on Indentation Results
Authors: Kim J.H. , Gouldstone A. , Chollacoop N.
Published: September 2022

The adhesion at the interface between coating and substrate is a key factor for the reliability and performance since the main problem in the application of coating systems is the delamination at the interface. Finite element models are developed to find a way to predict the adhesion strength of a thermal sprayed coating system from simply designed indentation test. Large depth indentation behavior is simulated to study shear induced delamination beneath the indenter. The interface between the coating and the substrate is modeled by three different bonding characters to investigate the effect of interfacial bonding on indentation test. Pressure-strain relations based on Tabor’s suggestion are observed for various combinations of material properties and interfacial bonding characteristics. The growth of a crack in the interface plane leaves a clear imprint on indentation load-depth curve in case of soft coating on hard substrate. Tabor curve also shows potential ability to detect interface bonding strength under indentation test.
TBC Characterization Using Capacitive and Inductive Sensors with Multivariate Inversion Methods
Authors: Sheiretov Y. , Zilberstein V. , Schlicker D. , Goldfine N. , Sikorski R.
Published: September 2022

This paper describes flexible inductive sensors, such as the Meandering Winding Magnetometer (MWM) and MWM-Arrays for characterization of conductive nonmagnetic, conductive magnetic and nonconductive magnetic materials; and capacitive sensors, such as the flexible Interdigitated Electrode Dielectrometer (IDED) (MWM and IDED are registered trademarks of JENTEK Sensors, Inc.) for characterization of dielectric materials. These sensors and multivariate inversion algorithms can provide effective nondestructive characterization of thermal spray coatings on complex shape components.
Inelastic Deformation of Metallic Coatings: Measurement and Analysis
Authors: Choi W. , Sampath S. , Gouldstone A.
Published: September 2022

Performance and reliability of TS coatings are strongly dependent upon their inelastic behavior. To that end, continuum-level flow stress and hardening have been explored by recourse to e.g., indentation, substrate curvature and tensile measurements. While the results of such efforts have great implication for process and quality control, further refinement is necessary for incorporation into models of wear, fatigue or delamination. Here we present results and analysis of mechanical testing on metallic TS coatings deposited by different methods, emphasizing particular characteristics under localized and cyclic loading.
PTA Welding – Modeling and Experimental Optimization
Authors: Wilden J. , Bergmann J.P. , Frank H.
Published: September 2022

Plasma Transferred Arc (PTA) welded coatings are used to improve surface properties of mechanical parts. Advantages are the high reliability of the process and the low dilution of substrate and coating material. Processing of surfaces by PTA welding is restricted at the time to flat horizontal position. Furthermore industry is interested in the development of strategies for coating with PTA in constraint position as complex 3-D parts could be then easily processed as well. Under commercial aspects, the process design can be optimized in order to increase process efficiency and to reduce heat input during the welding process. Process optimization involves the determination of guidelines for PTA welding in constraint positions as well. Modelling the process gives an alternative to reduce the experimental effort to optimize the welding process. Results of simulation studies of the PTA welding process will be given in the present work. It will be shown, that coating conditions can be optimized by varying plasma gas flow, heat input and heat flow, process speed or powder injection with regard to welding in constraint positions. The defined controlling of the PTA welding allows to modify process management with less experimental effort and to develop coating strategies for processing in different positions. In experimental investigations the developed coating strategies will be confirmed by producing PTA coatings in constraint position as well as complex 3-D parts.
Laser Cladding of M2 Steel on a Steel Substrate
Authors: Levcovici D.T. , Boiciuc R. , Levcovici S.M. , Gheorghieş C.
Published: September 2022

Multilayer high-speed cladding by injection of a M2 steel powder with 0.82%C, 4.7%Mo, 6.4%W, 4.1%Cr, 2.02%V, 0.3%Mn, as chemical composition, in a melted bath produced using a CO2 continuous wave laser connected to a x-y-z coordinate table was tested in order to increase the wear resistance and heat stability of tool active surfaces made of 0.45%C steel. Layers made by different laser runs were characterized by macro and microstructure analysis, as well as a phase identification analysis by X-ray diffractometry, micro-hardening analysis and hardness testing on the coated layer surfaces in order to establish the optimal cladding condition. Lathe tools made using this technique showed a good ability to maintain their cutting power during steel shaping.
On the Surface Engineering Technologies Available to Today's Engineer
Authors: Tucker R.C. , Treglio J.
Published: September 2022

It is difficult for engineers and scientists to remain up to date on the wide variety of surface engineering technologies available for product and process design, to solve maintenance problems, etc. This paper provides a brief overview of several of the major types of surface processes and resulting coatings or other surface treatments. It is intended only to provide an elementary introduction to serve as a background for further inquiry by the reader or to assist those not familiar with a given field to more easily understand other presentations in this conference session. The technologies considered include thermal spray, physical vapor deposition, and chemical vapor deposition.