bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Comparative Microstructural Investigation of Nanostructured and Conventional AI2O3 Coatings Deposited by Plasma Spraying
Authors: Zois D. , Vardavoulias M. , Lekatou A. , Panagiotopoulos I. , Vazdirvanidis A. 
Published: September 2022

Abstract
Nanostructured and conventional Al2O3 powders have been plasma sprayed, under the same parameters, to produce coatings on 304 stainless steel. The nanopowder was fabricated by mechanical attrition techniques and composed of agglomerates of nanoparticles, whereas the conventional powder consisted of solid granules. In order to maintain the beneficial effect of the nanostructure in the final coating, a fraction of the powder’s nanostructure should be retained in the coating after spraying. Dissimilarities were observed between the two types of coating, regarding porosity, roughness, deposition efficiency and α-Al2O3 to γ-Al2O3 proportions, which are related with the different percentages of semimolten particles in the coatings. The nanocoatings retained a higher percentage of semimolten particles than the conventional coatings, owing to the higher porosity of the nanoparticle agglomerates, as compared to the conventional solid granules. The molten part of both conventional and nanostructured coatings consisted of γ-Al2O3 of columnar morphology. In order to investigate the mechanism of the melting front advance into the particle interior during their presence in the plasma stream, the particles were sprayed directly into distilled water. The nanoparticles mainly formed hollow spheres, whereas the conventional particles mainly formed compact spheres. The internal porosity of the solidified nanoparticle agglomerates, which affected the overall coating porosity, was linked to the hollow sphere phenomenon.
Influencing Parameters on the Turning Process of Fe-Based Thermal Sprayed Coatings
Authors: Wilden J. , Jahn S. , Fischer G. , Wang S. 
Published: September 2022

Abstract
Thermal Spray processes are widely used to fabricate corrosion and wear resistant coatings respectively. However, these coatings have to be finished generally in subsequent steps, for example by turning, milling or grinding, to adjust the the required properties, e.g., surface roughness and accuracy. Up to now grinding is the most common post processing for wire arc sprayed coatings, but in recent years the hard turning technology gained high interest for coating treatment due to high machining efficiency. The aim of the present work is to enhance the machinability of different thermal sprayed coatings. DoE-based experiments regarding surface roughness, cutting forces and temperatures in the cutting zone had been carried out. Within the investigations a significant increase of hardness due to the hard turning process at Fe-Mn coatings had been verified. This effect, the force induced martensitic transformation, could improve the mechanical properties of the coating considerably. Based on the investigations presented in this paper, a deeper understanding of post processing of thermal sprayed coatings is given.
Three-Dimensional Analysis of Cold-Sprayed Coatings using Microtomography
Authors: Rolland G. , Borit F. , Guipont V. , Jeandin M. , Bara L. , Bourda C. 
Published: September 2022

Abstract
In this work, the microstructure of silver coatings obtained by cold spraying with a fine and a rather coarse powder were investigated. Cold-sprayed microstructures strongly depend on the deposition process parameters. These parameters have an influence on porosity, plastic strain, particle-to-particle bonding mechanisms. The originality of this study rests on the use of X-ray microtomography, which is shown to be a very powerful technique to investigate into cold-sprayed coatings. Several samples were machined from coatings by electro-discharge machining (EDM) then scanned using microtomography. Porosity fraction was determined by three-dimensional image analysis and compared to classical two-dimensional analysis of micrographs. A difference between the two methods was exhibited, which showed sample preparation effects. Consequently, X-ray microtomography seems to be well adapted to study cold-sprayed coatings thoroughly. Another result from this work was the characterization of the morphology of pores and deformed particles. Bonding mechanisms in cold spray could therefore be discussed. In addition, the knowledge on deformed particles allowed to simulate cold-sprayed coatings with build-up models. This will be done in a further work
HVOF Sprayed Nylon-11/Nanodiamond Composite Coatings: Production & Characterization
Authors: Stravato A. , Mochalin V. , Picardi S.C. , Knight R. 
Published: September 2022

Abstract
High velocity oxy-fuel (HVOF) combustion spraying has previously been shown to be a viable method for depositing polymer and polymer/ceramic composite coatings. The addition of hard particulate reinforcing phases to soft polymeric matrices should improve their durability and wear performance. Nano-sized diamond is an ideal reinforcing phase, owing to its high hardness and desirable thermal properties. Composite coatings comprising a Nylon-11 matrix reinforced with nanodiamonds have been successfully produced by HVOF. An important challenge is preserving the structure of the nanoparticles after thermal spray deposition and achieving a uniform dispersion of them within the polymeric matrix. Raman spectroscopy and X-ray diffraction confirmed the presence and retention of nanodiamonds after HVOF deposition. Understanding of the role of variables including the % loading of reinforcing phase in the matrix and powder preparation route are necessary. The coatings exhibited improved sliding wear resistance in macromechanical tests. Nanoindentation studies demonstrated an improvement in deformation behavior and recovery of the HVOF nanodiamond Nylon-11/nanodiamond composites subjected to deformation.
Numerical Modeling of Warm Spray (Two-Stage HVOF) Process
Authors: Katanoda H. , Kawakita J. , Kuroda S. 
Published: September 2022

Abstract
The warm spray gun was developed to make a coating of temperature-sensitive material, such as titanium, on a substrate. The gun has a combustion chamber followed by a mixing chamber, in which the combustion gas is mixed with the nitrogen gas at room temperature. The temperature in the gun can be controlled in the range of about 1500 - 2500 K by adjusting the mass flow rate of nitrogen gas. The mixed gas is accelerated to supersonic speed through a converging-diverging nozzle followed by a straight passage. In this paper, the performance of the warm spray gun is investigated by the simulation program in order to deeply understand the performance of the warm spray gun. The gas flow as well as the velocity and temperature of titanium particle inside and outside the gun are predicted by the numerical simulation.
HVOF Sprayed Coatings by Customized Cermet Materials for Specific Applications
Authors: Kitamura J. , Mizuno H. , Tawada S. , Aoki I. 
Published: September 2022

Abstract
High velocity oxy-fuel (HVOF) sprayed cermet coatings are required in various industrial fields due to their excellent properties, such as combination of wear resistance, corrosion resistance, high hardness, high bonding strength and stability under high temperature. In order to utilize them in the fields, optimization of composition and structure of the coatings are essentially important meaning that both spray powders and spray conditions are key process parameters. In this paper, developed spray powders of cermet materials are introduced for the specific applications, where 1. cavitation erosion, 2. mechanical impact, 3. corrosion by molten alloy and 4. general abrasive wear are major factors that damage the coatings. In order to solve these factors, HVOF coatings of 1. WC/Co/Cr with large WC particle, 2. WC/Cr3C2/Ni with addition of metal or alloy, 3. MoB/CoCr composed of double boride and 4. WC particle size in WC based cermet, are proposed and these merits are described.
Copper Particle Impact Onto Aluminium by Cold Spray
Authors: King P. , Zahiri S. , Jahedi M. 
Published: September 2022

Abstract
Copper particles with median diameter 15.2 micrometres were cold sprayed onto a polished aluminium 1139 substrate. Under the spray conditions used, deep embedment of the copper particles occurred. The as-sprayed copper particles were dissected using a focussed ion beam (FIB), and their microstructure investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). At the crater wall an intense shear zone developed due to sliding of copper past aluminium. Evidence of melting is presented.
PTA Processing of Ceramic Coatings
Authors: Drozda F.O. , Takano H. , Oliveira A. 
Published: September 2022

Abstract
Welding of dissimilar materials in particular ceramics to metals is a technical challenge with attractive economical consequences. In this study a ceramic coating was processed by plasma transferred arc (PTA). ZrO2–7wt.%Y2O3 powders were deposited on low carbon steel plates and on Ni based alloys layers previously welded on a steel plate. Coatings were evaluated regarding the soundness and features of the metal/ceramic bond. Results showed that the pair ZrO2–7wt.%Y2O3 /metallic alloy played a major role on the quality of the processed surfaces determining the effectiveness of the bonding. The presence of Al in the Ni based intermediate layer was detrimental to the adhesion of the ceramic coating. Deposition of ZrO2–7wt.%Y2O3 on NiCrFe intermediate layers allowed for a metal/ceramic bond resulting on 3,0mm thickness coatings. Ceramic deposits exhibited cracks, whose features were altered after a stress relief treatment of the substrate (AISI 1020+NiCrFe layer) prior to the deposition of ZrO2–7wt.%Y2O3. Transverse section analysis revealed the presence of second phase particles in the ceramic coating and the diffusion of elements from the intermediate Ni based layer into the ceramic deposit.
Numerical Investigation of the Heat Insulation Behavior of Thermal Spray Coatings by a Unit Cell Model Approach
Authors: Liu F.R. , Zeng K.L. , Wang H. , Zhao X.D. , Ren X.J. , Yu Y.G. 
Published: September 2022

Abstract
In the recent decade, considerable numerical models have been built up to simulate the thermal spray process. However, much less work has focused on the prediction of thermo-physical properties of the thermal spray coating, in particular the heat insulation properties. In this paper, a microstructure integrated finite element model is developed to investigate the heat insulation behavior of the thermal spray coating. A two-layer model is used to calculate thermal conductivity of the coating, where one layer stands for the coating by a unit cell, while another one for a standard material with known thermal conductivity. In the proposed unit cell model, pores and unmelted particles are assumed spherical and randomly distributed, and the interface between the coating and the unmelted particles is perfectly debonding. Based on the predictions, the effect of the pores, unmelted particles, cracks and their respective distributions on the heat insulation behavior of the coating has been further discussed in the paper.
Innovative High-Speed Camera System Diagnostics of Plasma Torch Fluctuations
Authors: Schein J. , Forster G. 
Published: September 2022

Abstract
Instabilities in plasma torches can result in poor particle heating and thus a production of low quality coatings. In order to investigate these fluctuations numerous experiments have been performed using high speed cameras taking pictures at a rate of 1000 images/s to create sequences with duration of few seconds total. Individual exposure times are usually in the range of few microseconds. In order to improve upon these parameters a new high speed camera system (HOBAS) was developed, which has been demonstrated to acquire short film sequences at a rate of 106 images/s using exposure times of down to 1ns/image. The camera system is based on a regular CCD camera mated with an MCP, where the MCP is triggered rapidly while the image is moved across the CCD-chip, thus enabling it to record multiple images during the CCD integration interval. Results of investigations will be presented using this instrument to detect plasma jet fluctuations in single electrode and multi electrode plasma torches.
Study on the Detection of Melting Temperatures and Sources of Errors using Two-Color Pyrometry for In-Flight Measurements of Plasma Sprayed Particles
Authors: Mauer G. , Vaßen R. , Stöver D. 
Published: September 2022

Abstract
In-flight particle temperature measurements during atmospheric plasma spraying (APS) of Tungsten, Molybdenum, and Yttria stabilized Zirconia by two-color pyrometry are analyzed statistically. The particle temperature distributions allow assessing the melting status of the particles. Particularly the melting temperature and the particle fractions being still molten or already solidifying can be identified. Furthermore, the relevant systematic and material dependant sources for measurement errors using two-color pyrometry are investigated. Their influence is estimated and corrected best possible. As far as there is reliable data available on the emissivity of the powder material there is good agreement between the corrected measured melting temperatures and reference data.
Evidence of the 2-Stage Build-Up Process in Cold Spray from the Study of Influence of Powder Characteristics on Ti-6Al-4V Coating
Authors: Christoulis D.K. , Borit F. , Guipont V. , Jeandin M. 
Published: September 2022

Abstract
During the deposition of metallic cold sprayed coatings, it could be observed that only a thin layer is formed on the substrate and further building-up of a thick coating is not enabled. As for other thermal spray techniques, the formation of cold sprayed coatings can be divided to two stages: the creation of the first layer onto the substrate and the building-up of the coating itself onto as-sprayed layers. This two-stage build-up process was evidenced according the study of two Ti-6Al-4V powders exhibiting different characteristics (particle size, morphology, oxygen content, hardness, etc) which were sprayed by cold gas dynamic spraying onto substrates of different nature with various hardnesses (Ti-6Al-4V, AISI 304L, Al-alloy 2017). The phenomenology of the two-stage process is investigated in the present study. Cold spray conditions with pure nitrogen or pure helium as processes gas were applied to achieve a significant difference for particle velocities. The first stage of the process was completed by both powders with the formation of a first coating layer onto the various substrates. However, very different features for particle-substrate interactions (penetration depth and comparative deformation) were observed. For the particle-particle interaction (the second stage of the process), despite similar spraying conditions for both powders, the results were completely different since the formation of thick coating was achieved only with one of the powders. It was found that the intrinsic ductility of the material powder is the main parameter to promote the successful completion of both stages in order to achieve thick coatings.
New Generation Perovskite Thermal Barrier Coating Materials
Authors: Ma W. , Jarligo M.O. , Mack D.E. , Pitzer D. , Malzbender J. , Vaßen R. , Stöver D. 
Published: September 2022

Abstract
Advanced ceramic materials of perovskite structure have been developed for potential application in thermal barrier coating systems, in an effort to improve the properties of the pre-existing ones like yttria stabilized zirconia. Yb2O3 and Gd2O3 doped strontium zirconate (SrZrO3) and barium magnesium tantalate (Ba(Mg1/3Ta2/3)O3) of the ABO3 and complex A(B’1/3B”2/3)O3 systems respectively, have been synthesized using ball milling prior to solid state sintering. Thermal and mechanical investigations show desirable properties for high temperature coating applications. On atmospheric plasma spraying, the newly developed TBCs reveal promising thermal cycle lifetime above 1300°C.
Role of High-Temperature Creep Stress in Thermally Grown Oxide Growth of Thermal Barrier Coatings
Authors: Ogawa K. , Nakao Y. , Seo D. , Miura H. , Shoji T. 
Published: September 2022

Abstract
Thermally grown oxide (TGO) grows at the top / bond coating interface of the thermal barrier coating (TBC) in service. It is supposed that the failures of the TBC occur due to thermal stress and the decrease of adhesive strength caused by the TGO growth. Recently, large local stress has been found to change both the diffusion constant of oxygen through an existing oxide and the rate of chemical reaction at the oxide / oxidized material interface. Since high thermal stress occurs in the TBC, the volume expansion of the newly grown oxide, and centrifugal force, the growth rate of the TGO may change depending on not only temperature but also the stress. The aim of this study is to make clear the influence of stress on the growth rate of the TGO quantitatively. As a result, the thickness of the TGO clearly increases with increase of the amplitude of the applied stress and temperature. The increase rate of the TGO thickness is approximately 23% when the applied stress is increased from 0 to 205 MPa at 900 °C, and approximately 29 % when the stress is increased from 0 to 150 MPa at 950 °C.
Characterization of Mesoporous Nanocrystalline TiO2 Deposited by Vacuum Cold Spray using Ceramic-Polymer Composite Powder
Authors: Yang G. , Fan S. , Gao J. , Li C. , Xi Y. , Li C. 
Published: September 2022

Abstract
Vacuum cold spray is a promising method to deposit nanocrystalline ceramic coating. The effective control of porous structure within nanostructured coating is essentially important to enhance the performance of the mesoporous nanocrystalline coatings for applications to catalyst and photo-electrode. In this study, the ceramic-polymer composite powders were employed as spray feedstocks for vacuum cold spray to control the pore structure in the deposits. The ceramic-polymer composite powders were made from nano-sized TiO2 (25nm), ZrO2 (30nm) and Al2O3 (30nm) and polyethylene glycol (PEG). The surface morphologies and the cross-sectional microstructures of the coatings were characterized using scanning electron microscope (SEM). The pore size distribution was measured using a nitrogen adsorption approach. The results showed that the deposition during spraying was implemented through the composite particles in a size ranging from submicrometers to several micrometers. Through post-spray heat treatment of the deposit, the PEG can be completely removed to increase the porosity in the deposit. The pores exhibited a bimodal distribution. The small pores present the size from several nanometers to tens of nanometers. Moreover, the size of large pores is in micrometer scale. The porosity and pore size distribution can be controlled by the composition of the composite powder.
Influence of the HVOF Gas Composition on the Thermal Spraying of WC-Co Submicron Powders (- 8 + 1 μm) to Produce Superfine Structured Hard Material Coatings
Authors: Tillmann W. , Vogli E. , Baumann I. , Matthaeus G. , Ostrowski T. 
Published: September 2022

Abstract
Deep-drawing is a widely used sheet metal forming process in the aircraft and automotive industry. The manufacturing of modern parts with complicated shapes and curvatures requires forming tools with highest shape accuracy even at complex surface geometries. However, the application of novel, high-strength sheet metals combined with a continuous increase in productivity impose high tribological demands on forming tools and finally lead to increasing wear. In order to minimize the high costs for the repair and maintenance of such tools it is crucial to enhance their service life by an appropriate surface modification, which is able to preserve the high shape accuracy. Conventional coatings obtained by thermal spraying of coarse grained feedstock materials are not suitable to achieve this aim. In this collaborative study, the feeding and HVOF spraying of WC-Co submicron powders (- 8 + 1 µm) have been investigated to manufacture superfine structured, wear resistant near-net-shape coatings with improved macroscopic properties and smooth surfaces. Special equipment for the powder feeding and a novel HVOF flame spraying system designed by Thermico (optimized for the processing of fine-scaled powder fractions) have been employed. Correlations related to the process dynamics at varying HVOF gas compositions, the thermokinetic particle behavior in-flight and corresponding coating properties have been analyzed.
Effects of Silver Addition on Mechanical Properties of Plasma Sprayed SOFC Interconnect Layer
Authors: Park S.D. , Kumar S. , Lee S.C. , Lee C. 
Published: September 2022

Abstract
In this study, interconnect layer of solid oxide fuel cell (SOFC) was built up from spray-dried La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) and blended LSCF-Ag through atmospheric plasma spraying (APS). Microstructure and phase of each coating was analyzed through scanning electron microscopy (SEM) and X-ray diffraction (XRD) respectively. Furthermore, bond strength, micro-hardness, thermal cycle test and oxidation test were performed and compared. The coatings prepared from spray-dried LSCF have higher porosity and cracks at inter-particle boundaries. However, the coatings with silver addition presented reduced cracks and porosity due to relatively high ductility of silver, resulting in higher mechanical properties.
Mechanical Modelling of Highly Heterogeneous Thermally Sprayed Abradable Coatings
Authors: Seichepine J. , Coddet C. , Sporer D. , Lourtie D. 
Published: September 2022

Abstract
Abradable coatings are widely used in aerospace turbine engines to improve seal performance between rotating and stationary parts and thus the engine efficiency. As they are elaborated by thermal spraying of composite powders, these materials are highly heterogeneous. Their behaviour in working conditions is quite complex and not fully understood. This study contributes to a better knowledge of the mechanical behaviour of a range of abradable coatings. Finite Element calculations were derived from the analysis of micrographs and allowed to estimate the coefficients of an anisotropic elastic law of behaviour. Several models were investigated in the case of an AlSi-PE (Polyester) coating. As the PE % appeared to be a determinant factor, its influence was quantified ranging from 0% to 100%, using virtual micrographs deduced from the original ones. The computed Young's moduli Ex (in coating longitudinal direction) were quite consistent, considering the hypotheses made. An empirical relationship giving the variation law of Ex versus the PE % was suggested and applied to predict the modulus Ex of a real coating, which was close to the measured value.
Modeling of Plasma-Sprayed Thermal Barrier Coatings for Prediction of Residual Stress
Authors: Arai M. 
Published: September 2022

Abstract
The surfaces of gas turbine components are coated by thermal barrier coatings (TBCs) with a plasma spraying technique. Spallation damage is an essential problem, as well known, in usage of TBC. A lot of efforts for TBC interfacial strength examination had been done, however studies examined how residual stress are formed after the process and also the coating stress changes with temperature were limited. In this report, the residual stress prediction model is proposed based on the splat deposition process. Simplified model including the plasma sprayed process is developed based on shear-lag theory. The simplification is given in continuous particle deposition process. That is, continuous particle deposited coating is modeled as a single layer, which is called by "deposition layer" in this study. This deposition layer is assumed to impact directly onto the substrate. The binding layer is also introduced to express multiple cracks caused by quenching stress in splats and sliding deformation at splat boundary. It is shown that the numerical analysis has good agreement with the associated experiments.