bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Surface Chemistry on Splat Formation during Plasma Spraying
Authors: Tran A. , Hyland M.M. , Qiu T. , Withy B. , James B.J. 
Published: September 2022

Abstract
In this study, aluminium 5005 and stainless steel 304L substrate surfaces were modified by thermal and hydrothermal treatments. Ni-Cr single splats were deposited onto these substrates at room temperature using plasma spraying. The collected splats were characterised qualitatively and quantitatively by Scanning Electron Microscopy (SEM) and ImageJ software. A splat classification scheme was developed based around splash and disk-type splats. The proportions of the different splat types were found to vary significantly as a function of substrate pretreatment, especially when the pretreatment involved heating. The effect of surface roughness to splat formation and splat shape was investigated. It was observed that surface roughness was not a critical factor in splat morphology. The above substrate surfaces were also characterised by X-ray photoelectron spectroscopy (XPS) using in-situ heating in vacuum to determine the effect of thermal pretreatment on substrate surface chemistry and the oxide thickness. It was found that heat treatment promoted a change in the chemical structure of the oxide surface layer which was consistent with the dehydration of oxyhydroxide to oxide. Dehydration of the substrate surface layer improved the physical contact between the splat and substrate which enhanced the formation of disk-splats, decreased the number of pores evident in the splats and increased number of splats and their diameter.
New LN2 Cryogenic Process to Strip Parts Thermal Spray Coated
Authors: Ducos M.D. , Richard F. , Matile O. , Warnecke R. , Hume H. , Debionne T. 
Published: September 2022

Abstract
Thermal spray coatings applied for aircraft gas turbine maintenance often needs to be stripped and removed. Various methods are used, such as chemicals or a very high pressure water jet. None of them are environmentally friendly and they must be applied with care to prevent substrate damage. Also, these methods can produce a great deal of waste that has to be managed. As regulation gets tougher, a new technology using very high pressure liquid nitrogen could be the future for such treatments. As the worldwide exclusive licensee, over several years Nitrocision LLC has developed and commercialized this technology, which initially was conceived in the late 90s by the Idaho National Laboratory. The NITROJET 6000 can pressurize Liquid Nitrogen up to 4000 bars and to temperatures as low as - 170°C. Various sets of tools can provide single or multiple nozzles on a fixed, or alternatively, a rotary head that provides greater coverage and efficiency. This publication presents case studies of the technology applied to coating removal on aeronautical parts in gas turbines and landing gears.
Improving Wear and Corrosion of Magnesium Alloys through a Combination of Thermal Spraying and Laser Cladding
Authors: Biermann T. , Weisheit A. , Bobzin K. , Zwick J. , Ernst F. , Richardt K. 
Published: September 2022

Abstract
Saving energy is a major concern in every aspect of the economy, especially in the automotive and aerospace industry. The use of lightweight materials is one way to reduce weight of moving parts and thus energy consumption. Research activities to improve the porosity on the one hand, and the coating properties like wear and corrosion resistance on the other hand, show the potential of a hybrid coating process. The creation of thermal-sprayed coatings and a laser post-treatment enable a minimization of porosity and an improvement of wear properties. Different coating materials (e.g. Al-Si alloy) have been investigated regarding microstructure, hardness, wear- and corrosion protection.
Improvement in Deposition Efficiency of Copper Particles onto Metallic Substrate in Cold Spray Process
Authors: Fukumoto M. , Terada H. , Satoh K. , Mashiko M. , Yamada M. , Yamaguchi E. 
Published: September 2022

Abstract
To improve the deposition efficiency of copper particles, especially fine particle, in cold spray process onto metallic substrate, optimization of nozzle shape and dimension was performed by numerical simulation. Maximum velocity of the particle reached up to 685 m/s under the optimum conditions by using self-designed nozzle based on the simulation results. In the spraying of copper particle onto steel substrate, lamellar-like unique micro-structure was observed near the interface region of the steel substrate. Correspondingly, hardness increase in this region of steel substrate was recognized. Work hardening was induced in the steel substrate due to the higher velocity of copper particles. Furthermore, to reduce the bow shock effect on the substrate surface region in cold spray process, special shaped nozzle was newly developed. While nominal particle velocity decreased in the special nozzle, deposition efficiency, Vickers hardness and adhesion strength increased significantly especially in the case of fine particle and higher pressure levels of the working gas. Numerical simulation showed that pressure level on the substrate surface decreased effectively in the special nozzle. In the observation of a cold sprayed individual particle onto mirror polished substrate, extended metal jet was recognized at particle’s periphery when the particle was sprayed by the special nozzle. The results indicate that the decrease of particles velocity by bow shock was suppressed effectively in the special nozzle as compared with conventional nozzle.
TGO Growth and Crack Propagation in a Thermal Barrier Coating
Authors: Chen W.R. , Archer R. , Huang X. , Marple B.R. 
Published: September 2022

Abstract
In thermal barrier coating (TBC) systems, a continuous alumina layer developed at the ceramic topcoat/bond coat interface helps to protect the metallic bond coat from further oxidation and improve the durability of the TBC system under service conditions. However, other oxides such as spinel and nickel oxide, formed in the oxidizing environment, are believed to be detrimental to TBC durability during service at high temperatures. It was shown that in an air-plasma-sprayed (APS) TBC system, post-spraying heat treatments in low-pressure oxygen environments could suppress the formation of the detrimental oxides by promoting the formation of an alumina layer at the ceramic topcoat/bond coat interface, leading to an improved TBC durability. This work presents the influence of post-spraying heat treatments in low-pressure oxygen environments on the oxidation behaviour and durability of a thermally sprayed TBC system with high-velocity oxy-fuel (HVOF)-produced Co-32Ni-21Cr-8Al-0.5Y (wt.%) bond coat. Oxidation behaviour of the TBCs is evaluated by examining their microstructural evolution, growth kinetics of the thermally grown oxide (TGO) layers, as well as crack propagation during low frequency thermal cycling at 1050°C. The relationship between the TGO growth and crack propagation will also be discussed.
Development and Investigation on New Composite and Ceramic Coatings as Possible Abradable Seals
Authors: Bardi U. , Giolli C. , Scrivani A. , Rizzi G. , Borgioli F. , Fossati A. , Partes K. , Seefeld T. , Sporer D. , Refke A. 
Published: September 2022

Abstract
In order to improve gas turbine performance it is possible to decrease back flow gases in the high temperature combustion region of the turbo machine reducing shroud/rotor gap. Thick and porous TBC systems and composite CoNiCrAlY/Al2O3 coatings made by Air Plasma Spray (APS) and composite NiCrAlY/graphite coatings made by Laser Cladding were studied as possible high temperature abradable seal on shroud. Oxidation and thermal fatigue resistance of the coatings were assessed by means of isothermal and cyclic oxidation tests. Tested CoNiCrAlY/Al2O3 and NiCrAlY/graphite coatings after 1000 hours at 1100°C do not show noticeable microstructural modification. The oxidation resistance of new composite coatings satisfied Original Equipment Manufacturer (OEM) specification. Thick and porous TBC systems passed the thermal fatigue test according to the considered OEM procedures. According to the OEM specification for abradable coatings the hardness evaluation suggests that these kinds of coatings must be used with abrasive tipped blades. Thick and porous TBC coating has shown good abradability using tipped blades.
Development of HVOF-Sprayed Nanostructured TiO2 Coatings for High Temperature Applications
Authors: Lima R.S. , Moreau C. , Garcia E. , Miranzo P. , Osendi M.I. 
Published: September 2022

Abstract
Titania (TiO2) coatings are candidates for high-temperature applications in the fields of wear, corrosion, and environmental barrier coatings (EBCs); however, at temperatures at or above 540 °C, titania coatings are not pursued due to the usual presence of the anatase phase in the as-sprayed TiO2 coatings. This phase tends to impede the applications of these materials at high temperatures due to the stresses provided by the critical anatase-to-rutile phase transformation at temperatures higher than 540 °C; such stresses tend to generate cracks in the coating microstructure, leading to premature coating failure. It has been hypothesized that this barrier could be overcome by the use of nanostructured TiO2 coatings, due to their known high toughness and resilience levels. Nanostructured TiO2 powders were HVOF-sprayed. The high velocity levels of the HVOF-sprayed particles generated a gas-tight microstructure (i.e., no through-thickness porosity). SEM pictures of the as-sprayed and heat-treated (800 °C for 1 h) coatings did not show any significant signs of crack network formation, which may have been prevented by the high toughness and resilience of these coatings. These coatings were also HVOF-sprayed on SiC substrates and did not exhibit macroscopic signs of delamination after a 1400 °C exposure for 1 h in air.
A Comparison of Sintering Behavior and Phase Transformation Characteristics Between Plasma Sprayed Commercial CSZ and Conventional YSZ Based TBCs
Authors: Altuncu E. , Ustel F. 
Published: September 2022

Abstract
Plasma-sprayed thermal barrier coating (TBC) systems are widely used in gas turbines blades in order to increase turbine entry temperature (TET) with better efficiency. Yttria stabilized zirconia (YSZ) has been usually chosen as the top thermal barrier coating material because of its low thermal conductivity, high thermal expansion coefficient and good corrosion resistance. However as a new candidate commercial TBC material, ceria stabilized zirconia (CSZ) currently looks to be promising. Ceria and ceria based ceramics show an outstanding potential for use at temperatures exceeding 1200 °C. CSZ coatings do not only have high temperature stability, good corrosion resistance and high fracture toughness but also lower thermal conductivity and higher thermal expansion coefficient than YSZ coatings. The sintering and phase transformation characteristics of both ceramic thermal barrier coatings under high temperature conditions are complex phenomena. In this paper, microstructural differences, sintering behaviours (1200 oC, 10h, 25h and 50h) and phase transformations of the plasma sprayed ceria stabilized zirconia (CSZ: ZrO2–2.5 wt.%Y2O3– 25 wt.%CeO2) and conventional yttria stabilized zirconia (YSZ; ZrO2–8 wt.%Y2O3) coatings and their powder materials have been investigated and compared using thermal analysis techniques, XRD and scanning electron microscope.
Residual Stress Distribution in HVOF Inconel 718 Coatings for Aerospace Repair Applications
Authors: Lyphout C. , Nylén P. , Manescu A. , Pirling T. 
Published: September 2022

Abstract
Residual stress build up in thick thermal spray coatings is a property of concern. The adhesion of these coatings to the substrate is strongly influenced by the residual stress generation during the coating deposition process. In the HVOF spray process, due to lower processing temperature and higher particle velocity as compared to plasma spraying, significant peening stresses are generated during the impact of semi molten particles on the substrate. The combination of these peening stresses together with quenching and cooling stresses that arise after deposition can be of significant importance. In this paper both a numerical finite element analysis (FEA) method, to calculate peening, quenching and cooling residual stresses, and experimental methods, as Modified Layer Removal Method (MLRM) and Neutron Diffraction analysis, are applied. The investigation is performed for thick Inconel 718 coatings on Inconel 718 substrates. Combined, these numerical and experimental techniques yield a deeper understanding of residual stress formation and a tool for process optimisation. The relationship between the stress state and deposit/substrate thickness ratio is given particular interest.
In Situ Visualization of Impacting Phenomena of Plasma-Sprayed Zirconia: From Single Splat to Coating Formation
Authors: Shinoda K. , Murakami H. , Kuroda S. , Oki S. , Takehara K. 
Published: September 2022

Abstract
Understanding the impacting phenomena of yttria-stabilized zirconia (YSZ) particles and following coating formation in plasma spraying process is of importance to control and design the microstructure of coatings such as thermal barrier coatings. To this aim, recently, the authors have developed a novel in situ monitoring system for particle impacts under atmospheric dc plasma spraying conditions. This system utilized a high-speed video camera coupled with a long-distance microscope and was capable of capturing the particle-impinging phenomena at one million frames per second. To understand the coating formation mechanism, two approaches were attempted, that is, observation of the single splat formation and the following coating formation as the integration of splats. In the former case, the deformation and cooling processes of YSZ droplets impinging on substrates were captured successfully. In the latter case, multiple-droplet-impacting phenomena were observed as an ensemble treatment. Representing coating process, the tower formation (1- dimensional) and bead formation (2-dimentional) were observed under typical plasma spray conditions for thermal barrier coatings. By using a triggering system coupled with the motion of a robot, impact events were recorded for every pass. The obtained images clearly showed the coating formation resulted by the integration of single splats.
Analysis of Plasma Spray Particle State Distribution for Deposition Rate Control
Authors: Wroblewski D. , Ghosh O. , Lum A. , VanHout M. , Basu S.N. , Gevelber M. , Willoughby D. 
Published: September 2022

Abstract
Plasma spray for depositing thermal barrier coatings features large distributions of particle states that result in significant variations in coating quality. These variations arise from distributions of particle sizes, large spatial gradients of plasma thermal-fluid fields, and temporal variations of the arc and jet. This paper describes a simplified approach for studying how particle state distributions are influenced by torch conditions and powder distributions, and the implications for deposition rate monitoring and control. The approach combines a simplified jet model with a more detailed particle model. The important fluid-thermal spatial gradients in the plasma jet are captured using a three zone model: a core region, modeled by growth of a turbulent shear layer around a laminar core, a transition region and a similarity region. Plasma-particle momentum and thermal interactions, particle phase transitions, internal particle temperature gradients, and collapse of in-flight hollow particles have been modeled using a multi-lumped particle model. Effects of distributions of particle size, particle morphology, injection velocity, and carrier gas flow were studied for YSZ spray in an Ar-He plasma. The results provide guidance on sensor design and operation and on approaches for plume location control.
A Combined Numerical and Experimental Analysis of the Cold Spray Process
Authors: Samareh B. , Dolatabadi A. , Lüthen V. , Stier O. 
Published: September 2022

Abstract
The two-phase flow properties of copper particle laden nitrogen are measured and compared to computational fluid dynamic calculations, determining the achievable degree of consistency between model and reality. Two common, commercial nozzles are studied. A two-way coupled Lagrangian scheme along with the RSM turbulence model is used to track the particles and to model the interactions between the gas and the particulate phase. Significant agreement is found for the geometrical gas flow structure, the resulting particle velocities, and the dependence of the two-phase flow on the particulate phase mass loading. The particle velocities decrease with increasing mass loading, even for modest powder feed rates of less than 3 g/s. The velocity drop occurs even when the gas flow rate is kept constant. Adiabatic gas flow models neglecting the energy consumption by the particles are thus inaccurate, except for very dilute suspensions with low technical relevance. For the cases modeled, the experiments evidence the high predictive power of the chosen approach.
Microstructure and Creep Behaviour of Plasma Sprayed Yttria Stabilized Zirconia Thermal Barrier Coatings
Authors: Soltani R. , Coyle T.W. , Mostaghimi J. 
Published: September 2022

Abstract
The purpose of this study was to determine the creep/sintering characteristics of thermally sprayed zirconia coatings and attempt to understand the influence of microstructure on the creep resistance of deposits. The major modification, compared with more typical practice, was employment of powder feedstock with agglomerated sub-micron size particles (Nanox), which is compared to one of the best commercially available powders (HOSP). Thick plasma sprayed coatings were prepared and their physical and mechanical properties were characterized. Creep/sintering experiments were then conducted to investigate the response of the materials when exposed to high temperatures under load. The results showed that it could be possible to correlate the splat thickness to the creep behaviour of the coatings.
Microstructure of Plasma Sprayed La2O3 Modified YSZ Coatings
Authors: Liu Y. , Tao S.Y. , Zhou X.M. , Gao Y.F. , Li W.D. , Luo H.J. , Ding C.X. 
Published: September 2022

Abstract
Yttria stabilized zirconia coatings (YSZ) have received great attention as a good candidate for thermal barrier coatings (TBCs). However, the grain growth and phase transformation, within applied coatings particularly under temperatures higher than 1473 K limit its further applications to great extent. In our present study, in order to develop better understanding of aforementioned phenomena and explore effective methods to conquer this challenge, TBCs using traditional and La2O3 modified YSZ powders were deposited by atmospheric plasma spraying and their microstructures were investigated. Results show that the La2O3 addition can effectively alleviate the grain growth of coatings under high temperature.
Issues and Requirements for Developing a Plasma Spray Deposition Rate Sensor for Real-Time Control
Authors: Gevelber M. , Wroblewski D. , Vattiat B. , Ghosh O. , VanHout M. , Basu S.N. 
Published: September 2022

Abstract
This paper investigates the need and requirements for developing an improved sensing scheme for plasma spray, which would aid in compensating for the large variations in deposition rate. Experimental evaluation of a variety of current sensors reveals poor correlation with deposition rate. Important issues that explain these results include reconsidering what particle state characteristics should be measured and determining what sensing characteristics are required to achieve better correlation with deposited mass. A new particle flux sensor is proposed that meets these challenges is evaluated.
Spreading of Plasma-Sprayed Molybdenum on Grit-Blasted Glass
Authors: McDonald A. , Chandra S. , Moreau C. 
Published: September 2022

Abstract
Plasma-sprayed, molten molybdenum particles (~55 µm diameter) were photographed during impact on grit-blasted glass surfaces that were maintained at either room temperature or at 350°C. Droplets approaching the surface were sensed using a photodetector and after a known delay, a fast charge-coupled device (CCD) camera was triggered to capture time-integrated images of the spreading splat from behind the glass. A rapid two-color pyrometer was used to collect the thermal radiation from the spreading droplets to follow the evolution of their temperature and calculate the splat cooling rates. It was found that as the surface roughness increased, the maximum spread diameters of the molten molybdenum droplets decreased, while the splat cooling rates increased. Impact on non-heated and heated roughened glass with similar roughness values produced splats with approximately the same maximum spread diameters, skewed morphologies, and cooling rates. On smooth glass, the splat morphologies were circular, with larger maximum spread diameters and smaller cooling rates on non-heated smooth glass. An established model was used to estimate the splat-substrate thermal contact resistances. On highly roughened glass, the thermal contact resistance decreased as the glass roughness increased, suggesting that splat-substrate contact was improved as the molten metal penetrated the spaces between the large asperities.
Particle Temperature Fluctuations in Plasma Spraying
Authors: Goutier S. , Nogues-Delbos E. , Vardelle M. , Fauchais P. 
Published: September 2022

Abstract
In a DC plasma spray torch, the dynamic behaviour of the arc attachment at the anode nozzle results in fluctuations of arc voltage and the resulting plasma jet instabilities affect the treatment of the particles injected in the plasma flow, and thus, the coating quality. However it is not clear if the experimentally-observed fluctuations of particle temperatures are a major phenomena and if their frequencies are always in unison with those of voltage. In this study, two on-line techniques are used to investigate respectively the time-variation of particle temperatures and their correlations with voltage variations; the first technique makes it possible to analyse plasma voltage instabilities and the second one to investigate the instabilities of particle temperatures. Both allow determining the frequencies and amplitude variations of voltage and particle temperatures. The experiments are carried out with two plasma torches (F4-type and 3MB-type) using respectively argon-hydrogen or nitrogen–hydrogen mixtures as plasma-forming gases. A good correlation between arc voltage and particle temperature fluctuations is observed when the plasma torch is operating with argon-hydrogen while that's not the case when the torch is operating with nitrogen-hydrogen.
Substrate Properties Influence on the Coating Deposition by DYMET Technology
Authors: Shkodkin A. , Kashirin A. , Klyuev O. 
Published: September 2022

Abstract
The heating of the substrate by the jet may influence on the process of coating deposition by DYMET technology. It can be observed as deposition efficiency variation at various nozzle transverse speeds. Experimental investigation of the deposition efficiency variation for different jet stagnation temperatures and different substrate thermal properties is presented and discussed. The suppression of substrate influence on the deposition process with the coating thickness growth is demonstrated.