bluuebunny/crossref_metadata_2025_split huggingface dataset:
Examining the Variations in Splat Properties within the Footprint of a Spray Stream
Authors: Srinivasan V. , Vaidya A. , Streibl T. , Li L. , Sampath S. 
Published: August 2022

Abstract
It is known that particles injected in a plasma stream follow differing trajectories which in turn leads to different thermal and kinetic history dependent on the location of particle in the plume. The variation in particle characteristics (temperature and velocity) across the plume has been the focus of research over the years. The corresponding variation in impacting particles, particularly in terms of their splat characteristics have not been explored as systematically. This is important for a complete understanding of the coating build-up phenomena and the variations in coating properties. This paper presents the results of a study in which the spatial variation in particle properties is mapped to the spatial variation in splat properties. This has been accomplished using a procedure to collect splats using a shutter mechanism that allows us to expose the substrate for approximately 50 milliseconds. Splats of Alumina and a Ni- Cr-B-Si-Mo have been collected on polished substrates maintained at 250ºC and studied. Micrographs reveal differing splat morphologies across the spray plume – from missing-cores in one part to complete disc-shaped splats in the other. Extent of flattening and fragmentation have been quantified and found to vary within the ‘splat map’. Correlation between the location of particle in the plume and the resulting splat has been constructed using this data. Abstract only; no full-text paper available.
Improvement of DC Thermal Plasma Spraying by Reducing the Cold Gas Entrainment Effect
Authors: Henne R.H. , Arnold J. , Schiller G. , Kavka T. 
Published: August 2022

Abstract
Plasma jets for thermal spraying are strongly affected in a negative sense by the interaction with the relatively static surrounding atmosphere, particularly at atmospheric spray conditions. Turbulences at the jet fringes arise resulting in entrained cold gas, in slowing and cooling down of the jet and in causing eventually its disintegration. All means suppressing or delaying this phenomenon, called cold gas entrainment, help to improve the interaction of plasma and spray material and hence lead to better product quality and higher deposition efficiency of the process. To observe the cold gas entrainment, to investigate the thermal and kinetic properties of DC plasma jets at different operating conditions and to study the effect of plasma source and powder injection modifications a diagnostic equipment with Schlieren optics, enthalpy probe and mass spectrometry was installed. By modification of the internal and external anode nozzle contours and also by application of a shroud nozzle around the plasma jet exit encouraging results with reduced penetration of cold ambient air into the jet could be obtained.
Particle Properties During Plasma-Spraying of Yttria Stabilized Zirconia Using a Triplex-II Torch
Authors: Döring J.-E. , Marqués J.-L. , Vaßen R. , Stöver D. 
Published: August 2022

Abstract
The triplex-torch design providing three stable arcs in power and geometry promises a stable, quasi-laminar plasma jet leading to an uniform plasma and thus an uniform particle distribution. Additionally, the three powder injectors lead to an extended powder feed rate, resulting in a lower spraying time. This paper deals with particle properties of YSZ (SM 204NS) with respect to their injection location and powder feed rate and the resulting coating microstructure and porosity levels. Concerning the injection conditions, the three powder jets can be clearly identified. Their location depends on the spraying distance and less pronounced on the injection velocity. Interestingly, if the different powder-sizes are grouped and the jet cross-section is plotted for the different size cuts, the position of each size cut varies. Thus, a local separation of the powder takes place in the jet. The powder feed rate was varied from 30 to 320 g/min. Accordingly to this variation, the particles mean temperature was lowered from 3050°C down to 2650°C, and the velocity values dropped from 230 m/s to 155 m/s. Regarding the achieved coating thickness, up to a powder feed rate of approximately 210 g/min the thickness is increasing with no dramatic change in the porosity values. More powder does not lead to a thicker coating but results in a significantly higher porosity. Moreover, the microstructure of the coatings obtained by using a higher feed rate exhibits more segmentation cracks.
Plasma Spray Process Control with Neural Network
Authors: Jakimov A. , Hertter M. , Abdullahi H. , Staudacher S. 
Published: August 2022

Abstract
In current aircraft engines challenging coatings or coating systems with different functions are used. Many of these coatings are applied to different components with thermal spray processes. Thermal spraying is a very sensitive and very complex process, which is influenced by numerous controllable variables like the powder feed rate, the gas flow rates, etc. as well as not controllable variables like the torch wear, varying powder properties, etc. With conventional process control based on linear algorithms it is not possible to enduringly create constant coating properties, because they cannot describe the complexity of all influencing variables. In this work, the possibility of a closed loop was investigated exemplarily for an atmospheric plasma spray process (APS). During serial production a data base was collected, consisting information about torch and plume conditions as well as powder and coating properties. This data base was used to train different neural networks (NN). With regard to the automation of the APS, the NN obtained target values of relevant coating properties and should calculate the needed control variables. The result of this work shows the difficulties in the quantification of relevant influencing variables and the feasibility of the plasma spray process control with neural network.
Computational Evaluation of Thermal Barrier Coating Characteristics Under Plasma Spraying
Authors: Solonenko O. , Sato T. , Nishiyama H. 
Published: August 2022

Abstract
To enhance the efficiency of computational experiment covering all links of a technological chain ‘generation of plasma jet – injection of particles – formation of dust-laden plasma jet – coating deposition from drops of a melt’ it is very attractive to integrate the experimentally tested analytical solutions characterizing splats formation along with 2-D/3-D models describing dust-laden technological flow. The authors of the present paper carried out a computer simulation of a plasma spraying process from zirconia particles injection to a coating formation conducted by integrating particle-laden plasma flow, metal oxide splat formation and coating formation models with reference to the thermal barriers. The velocity and temperature of both plasma flow and zirconia particles under an applied RF electromagnetic field were clarified by using the first model. Radial distributions of particle impact location, velocity and temperature were obtained based on both an unsteady effect of a plasma flow and distributions of particle size and injection velocity. Secondly, splat thickness and diameter after zirconia droplets impact onto substrate were clarified by using the earlier experimentally probated analytical solution. Finally, the coating thickness distributions were evaluated by using the last model. Abstract only; no full-text paper available.
Photocatalytic Properties of Nanostructured TiO2 and TiO2-Al Coatings Elaborated by HVOF Spraying
Authors: Toma F.-L. , Chwa S.-O. , Bertrand G. , Liao H. , Klein D. , Coddet C. 
Published: August 2022

Abstract
In the present study, TiO2 and TiO2-Al composite coatings were prepared by HVOF spraying using reconstituted nanosized feedstock powders prepared via the spray drying technique. In the flame, the powders were injected by two methods: internal injection i.e. as in conventional HVOF process and external injection i.e. outside the torch nozzle. The microstructure of the coatings was characterized by scanning electron microscopy and X-ray diffraction. It was found that the amount of anatase in the coatings depends on the nature of the powder and also on the type of the injection method. The coatings were tested for their photocatalytic properties regarding the conversion rate of nitrogen oxides. Coatings elaborated by external injection presented a better photocatalytic activity than those obtained by the conventional HVOF process.
In-Flight Particle Characterization of HVOF-Arc Hybrid Gun
Authors: Kosikowski D. , Batalov M. , Mohanty P.S. 
Published: August 2022

Abstract
The high-velocity oxy-fuel (HVOF) gun represented a major development towards forming dense coatings. But, compared to the electric arc-spray process, the HVOF process is more difficult to apply and in general more costly. Therefore, some process development efforts have aimed at exploiting the attributes of both the electric arc-spray technique combined with those of the HVOF technique. Specifically, this hybrid process utilizes the electric arc spray benefits of using wire stock and high deposition rates combined with the higher coating densities obtained using HVOF. This paper presents an in-depth, in-flight particle characterization of a hybrid spray gun. A DPV-2000 particle diagnostics sensor was used to measure particle velocity, temperature, size and distribution. The influence of feed material, electric arc-spray parameters, and HVOF parameters on the particle characteristics is presented. It is observed that the velocity of the particles in the hybrid mode are slightly lower than the velocity of particles by HVOF alone but significantly higher than typical electric arc-spray velocities. In addition, the particle temperature in the hybrid mode isn’t significantly different than those by HVOF only. The particles produced by the hybrid gun tend to be more uniform and smaller compared to traditional electric arc-spray coatings.
Friction and Wear Behavior of Plasma Sprayed Al2O3 and Cr2O3 Coatings Against Copper Alloy Under High Load Dry Sliding
Authors: Tao S. , Zhou X. , Ding C. 
Published: August 2022

Abstract
Al2O3 and Cr2O3 coatings were deposited by atmospheric plasma spraying. The tribological properties of coatings against copper alloy were evaluated with a block-on-ring configuration under dry friction conditions at room temperature. Microstructure of powders and coatings were observed using scanning electron microscopy (SEM) and optical microscope (OM). Some thermo-physical properties of coatings were measured. Results showed that the Cr2O3 coating exhibits cracking failure in the sliding condition with a normal load of 500N and a sliding velocity of 0.84 m/s. This failure of the plasma sprayed Cr2O3 coating is explained in terms of its low thermal conductivity.
Measuring Thermal Contact Resistance Between Molten Aluminum Droplets and a Steel Plate
Authors: Heichal Y. , Xue M. , Chandra S. , Mostaghimi J. 
Published: August 2022

Abstract
The impact and solidification of 4 mm molten aluminum alloy 380 droplets on a tool steel substrate was studied both analytically and experimentally. Temperature histories at different radial location on the substrate surface under impacting droplets were recorded using an array of thin film thermocouples with response times less than 1 µs. Photographs were taken of droplet impact onto the substrate. Initial substrate temperature was varied from room temperature to 300°C and average surface roughness from 0.5 to 5.0 µm. Estimates of thermal contact resistance were made by matching measured substrate temperatures with an analytical solution for surface temperature variation. A model of the true area of contact between molten metal and a rough surface was developed in order to predict how contact resistance changes with surface roughness and contact pressure. Impact of molten aluminum alloy droplets was simulated using a three-dimensional numerical. Using values of thermal contact resistance predicted by the model gave good agreement between computed and observed droplet shapes during impact.
Shear Testing for Characterizing the Adhesive and Cohesive Coating Strength Without the Need of Adhesives
Authors: Siegmann St. , Dvorak M. , Grützner H. , Nassenstein K. , Walter A. 
Published: August 2022

Abstract
The characterization of the adhesive and cohesive strength of thermally sprayed coatings is often evaluated according to given standardized testing procedures. These tests require the preparation of normally large coupons which have to be fixed together using an appropriate adhesive. Additionally they need time for preparation (e.g. annealing/curing of the adhesive) and require test equipments normally not available at job shops for coating development. One of the largest limitations of these tests is the applicability only for non-porous coatings, and in some cases the limited strength of the adhesive. Within a European CRAFT research project on “standards, measurements and testing”, a new shear test method was developed to characterize the mode and value of failure of thermally sprayed layers in a more reliable and less limited manner. This new shear test does not need any adhesive and yields more intrinsic information on coating quality than conventional tensile tests.
Nanostructures in Thermal Sprayed Hydroxyapatite (HA) and HA/Nano-Zirconia Coatings and their Influence on Coating Properties
Authors: Li H. , Khor K.A. , Cheang P. 
Published: August 2022

Abstract
Nanostructured hydroxyapatite (HA) and HA/nano-zirconia powders were sprayed by both plasma and HVOF spraying. Microstructure characterization on the nanostructured coatings were conducted using scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), and Raman spectroscopy. Results showed that the nanostructures of the HA feedstock retained to some extent after the thermal spraying depending on the melt state of the powders. The microstructural features of individual HA splats were also characterized through TEM observing both as-sprayed and ion-milled splats. A nanostructure (with ~ 30nm grains) within the surrounding parts of the HA splats was revealed, while significant grain growth (a size up to 5 µm) depending on flattening state was found at the center of the splats. It also revealed that the nano-sized zirconia particles (&lt; 90 nm) retained their fine size after HVOF deposition, and were evenly distributed within the coating. The crystallite size of tetragonal zirconia in the coating was found to be less than 13 nm. The biocompatibility of the coatings was characterized using in vitro incubation testing in simulated body fluid and osteoblast cell culturing. It showed that the presence of the nanostructures in the coatings improved the stability of the coatings (delayed the dissolution). The addition, the presence of the nanostructures contributes to improved mechanical properties.
Development of Highly Wear Resistant Iron Based PTAW Hardfacing Alloys
Authors: Branagan D. , Marshall C. , Meacham B. 
Published: August 2022

Abstract
Typically, highly wear resistant PTA materials for mining and mineral processing applications are developed by adding ceramics like tungsten carbide to appropriate matrices. The problem is that failure during abrasion can often occur as a result of preferential wearing of the soft matrix material or crack formation through the highly loaded brittle ceramic phases. In this paper, the development of new highly wear resistant plasma transferred arc (PTAW) iron based alloys will be detailed. In this case, the matrix material itself was found to have excellent abrasion resistance with high hardness obtained in the weld deposits up to Rc 66 from the development of a fine structure consisting of a high volume fraction of complex M23(BC)6 and M7(CB)3 borocarbides phases. The matrix material is found to additionally exhibit high toughness up to 73.3 MPam1/2 due to an effective distribution of fine carbide and boride phases in a ductile dendrites / cells. When adding WC particles to the starting powder and welding, the matrix was found to effectively wet the WC particles forming a strong tough matrix which avoids the typical “pull-out” or cracking found in conventional PTAW hardfacing materials. Specific weight loss measurements were conducted using ASTM G-65 wear testing and will be correlated to the structure achieved during PTAW. Abstract only; no full-text paper available.
New Concepts for Plasma Sprayed Zirconia TBCs for Aeronautical Applications
Authors: Tricoire A. , Vardelle M. , Fauchais P. , Braillard F. , Malié A. , Bengtsson P. 
Published: August 2022

Abstract
The aim of this work, devoted to yttria stabilised zirconia (YSZ) thermal barrier coatings, is to produce by DC plasma spraying a single thick pass macro cracked orthogonally to the substrate. YSZ was plasma sprayed in air atmosphere on Hastelloy X substrates, with a NiCrAlY bond coat. A three-zone microstructure is observed, where lamellae and columns are present. The measurements of deposition stresses during spraying allow explaining the macrocrack formation.
Formation of TiN-Al2O3-ZrO2 Composite Coatings by Gas Tunnel Type Plasma Spraying
Authors: Kobayashi A. 
Published: August 2022

Abstract
High performance Thermal Barrier Coating (TBC) has been expected for use under extream conditions in advanced industrial fields. A high performance of zirconia (ZrO2) composit coating was achieved by gas tunnel type plasma spraying. The zirconia-alumina (ZrO2-Al2O3) composite coating has a high hardness layer at the surface side of the coating, which shows the graded functionality of hardness, and is expected to use as a Thermal Barrier Coating (TBC). TiN thick coatings which has excellent properties have also been formed at high deposition rate by means of the gas tunnel type plasma reactive spraying. In this study, the fundamental characteristics of this method were investigated by measuring the properties of the titanium nitride (TiN) coatings formed on traversed stainless steel substrate. Some coating characteristics of TiN which depend on the spraying distance, the environmental gas, traverse number etc. were then clarified. The functionally graded property of the ZrO2-Al2O3 composite coating was clarified to make TiN-Al2O3 -ZrO2 Composite Coatings. The TiN coating was overcoated on the ZrO2-Al2O3 coating, in order to enhance the performance of such high hardness composite coating. The Vickers hardness of the TiN layer was increased at the coating surface, which corresponded to the result that the coating surface became dense. The graded functionality of the hardness in the thickness direction was increased remarkably in the TiN-Al2O3 -ZrO2 Composite Coatings by Gas Tunnel Type Plasma Spraying. In addition, the performance of TiN thick composite coating was discussed as a heat resistant TBC.
Thermal Conductivity Evaluation and Comparsion of APS Low Density and Dense Vertically Segmented Advanced Thermal Barrier Coatings
Authors: Bolcavage A. , Feuerstein A. , Hitchman N. 
Published: August 2022

Abstract
This study on ceramic thermal barrier coatings (TBCs) presents baseline thermal conductivity data on as-deposited 7-8 wt.% YSZ and a paired-cluster rare-earth oxide doped YSZ, prepared using air plasma spray (APS). The thermal diffusivity for each coating was measured up to 1100°C using the laser flash method, and from these values, the thermal conductivity was calculated. The maximum benefit for thermal conductivity reduction in TBCs with a (GdO2, Yb2O3)-doped YSZ composition was highest for APS dense, vertically macrocracked microstructures, whereas in the case of low density APS TBCs, the reduction in conductivity was found to be more strongly influenced by horizontally-oriented, sub-critical defects and porosity within the coating microstructure.
A Comparison of Cr3C2-NiCr Coatings Obtained by HVOF using Propylene and Hydrogen as Fuel Gases
Authors: Guilemany J.M. , Espallargas N. 
Published: August 2022

Abstract
Due to its oxidation resistance, HVOF thermal sprayed Cr3C2-NiCr coatings have been widely used for wear resistance at elevated temperatures up to 850ºC. During HVOF spraying deposition, compositional degradation occurs through dissolution of the carbide phase into the metal matrix. The occurrence of carbide dissolution and the high working temperatures affects on the final properties of the coating. The aim of this work is to study the effect on the structure and wear properties at elevated temperatures of Cr3C2- NiCr coatings using hydrogen as a fuel gas against propylene. The structural characterization was done by SEM-EDS, XRD, and Scanning White Light Interferometry (SWLI). Wear properties at room and high temperatures have been evaluated by Ball-on-Disk (ASTM G99-90). Oxidation resistance of all coatings was carried out using a calorimetric technique Abstract only; no full-text paper available.
Properties of HVOF Sprayed Multi-Scale Polymer/Silica Composite Coatings
Authors: Gupta V. , Knight R. , Ivosevic M. , Cairncross R.A. , Twardowski T.E. , Taghizadeh S. 
Published: August 2022

Abstract
The high velocity oxy-fuel (HVOF) combustion spray process has been demonstrated to be a suitable technique for the deposition of nano-reinforced polymer matrix composite coatings by controlling both the particle dwell time and the substrate temperature. HVOF-sprayed polymer matrix composites incorporating reinforcements with size scales ranging from 7 nm to 100 µm are being studied to bridge between the nano and conventional scale regimes. Microstructural characterization has been used to characterize the dispersion and distribution of the ceramic reinforcements within the polymer matrix. The effect of particle size distribution on reinforcement dispersion and distribution has been studied, and the influence of substrate temperature on coating adhesion has also been investigated. Changes in crystallinity, as determined by Differential Scanning Calorimetry (DSC), are being correlated to coating microstructure, reinforcement loading and process parameter variations. Results of optical and scanning electron microscopy, scratch testing and DSC characterization of the feedstock materials and sprayed coatings are presented. Coatings of nominal 60 µm Nylon 11 with 10 vol. % of nano and micron size hydrophilic silica reinforcements exhibited a ~22 % improvements in scratch resistance compared to pure Nylon 11 coatings. An ~15 % improvement in scratch resistance was obtained for coatings containing 10 vol. % nano scale hydrophilic silica reinforcement.