bluuebunny/crossref_metadata_2025_split huggingface dataset:
Improved Mechanical Properties by Nanoreinforced HVOF-Sprayed Ceramic Composite Coatings
Authors: Neufuss E. , Dyshlovenko Turunen , Varis T. , Keskinen J. , Fäll T. , Hannula S-P. 
Published: September 2022

Abstract
HVOF thermal spraying has been developed to deposit dense ceramic coatings with improved protective properties for various applications. Even though HVOF coatings are much denser as compared to ordinary plasma sprayed coatings, the coating properties are inferior as compared to bulk ceramics because of pores and microcracks, which influence adversely the coating properties, i.e. toughness, hardness and wear resistance. One strategy to improve the properties of the coatings is to decrease the grain size of the ceramic phase and to add toughening elements to the microstructure. Nanocrystalline coatings have been found to offer better thermal shock resistance, lower thermal conductivity and better wear resistance than their conventional counterparts. In this paper we describe the development of nanocrystalline ceramic composite coatings, where the grain size of ceramic has been decreased and a few percents of alloying element has been added in order to toughen the coating. Dense nanostructured alumina coatings alloyed with Ni and ZrO2 nanosized particles were manufactured by HVOF spraying by using HV2000 spray gun. Mechanical properties, especially elastic modulus and relative fracture toughness were studied. Used techniques were instrumented nanoindentation and KIC evaluation. As a result coatings with nearly 100% improvements in relative fracture toughness were produced for nanoreinforced alumina composite coating. Results are compared with the microstructure, hardness and abrasive wear resistance of the coatings.
Microstructure and Mechanical Properties of Yttria Partially Stabilized Zirconia Coatings Deposited by Laser-Assisted Air Plasma Spraying
Authors: Dubourg L. , Moreau C. 
Published: September 2022

Abstract
In laser-assisted air plasma spraying (LAAPS), a laser beam interacts simultaneously with the coating surface during plasma spraying in order to increase the coating surface temperature and possibly remelt the coating surface. As a result, the microstructure is partially densified and macrocracks can be inhibited. In this paper, LAAPS was performed to improve the mechanical properties of ZrO2 – 8 wt.% Y2O3 coatings. The coating microstructure was characterized by optical microscopy, SEM and X-ray diffraction. The mechanical characterization was done by hardness measurements, thermal shock resistance and erosive wear tests. Results showed that laser assistance may induce: (1) a decrease of the amount of microcracks and interlamellar pores, (2) a columnar dendritic structure in the coating splats and (3) an improvement of the thermal shock resistance. LAAPS did not affect the hardness or the erosive wear resistance of yttria partially stabilized zirconia coatings.
Photocatalytic Function of FeTiO3 in Composite TiO2-FeTiO3 Coatings Prepared by Plasma Spray
Authors: Ye F.-X. , Ohmori A. , Tsumura T. , Nakata K. , Li C.-J. 
Published: September 2022

Abstract
The compositions and photocatalytic activity of plasma sprayed TiO2, TiO2-30%FeTiO3, TiO2-50%FeTiO3 and FeTiO3 coatings were investigated. The influence of FeTiO3 compound on the photocatalytic activity of TiO2 coating was clarified. The TiO2-30%FeTiO3 coating sprayed under the arc current of 400 A had good photocatalytic activity because the coating did not contain the unfavorable Fe2TiO5 phase. The relative deposition speed of TiO2-30%FeTiO3 powder under the arc current of 400 A was approximate to 4 µm/pass. Although pure FeTiO3 compound nearly did not show photocatalytic performance, the existence of FeTiO3 could improve the photocatalytic activity of anatase TiO2 if FeTiO3 contacts coherently with it, which was explained using two-steps electron transfer model.
Hot Salt Corrosion Behavior of High Velocity Arc Sprayed Fe-Al Based Composite Coatings
Authors: Zhang W. , Xu W. , Xu B. 
Published: September 2022

Abstract
Fe-Al based composite coatings were deposited on Grade 20 steel substrates by High Velocity Arc Spraying (HVAS) technology. Hot salt corrosion properties of the coatings were studied at the temperatures of 450 °C,650 °C and 800 °C . Results showed that the corrosion resistance of the Fe- Al/Cr3C2 composite coatings changed little with the increase of temperature, contrasted to the substrate and Fe-Al coatings. The excellent corrosion resistance of the Fe-Al/Cr3C2 composite coatings was attributed to the oxidation of the iron, aluminum and chromium to form protective scales. In hot salt, there are mainly iron oxides at the outer corrosion surface; aluminum and chromium oxides are found at the inner corrosion surface, which can effectively protect the Fe- Al/Cr3C2 composite coatings from corrosion.
Roughness Enhancement of HVOF Sprayed MCrAlY Bond Coatings for Adhesion Improvement of Ceramic Top Layers
Authors: Bach Fr.-W. , Mohwald K. , Engl L. , Duda T. 
Published: September 2022

Abstract
High velocity oxyfuel flame spraying (HVOF) has a great potential for replacing the low pressure plasma spraying (LPPS) process in most applications for hot corrosion protective MCrAlY coatings for turbine hot gas path parts. Compared to LPPS coatings, state-of-the-art HVOF sprayed MCrAlY coating systems feature competitive hot corrosion protective properties. Low HVOF facilities investment costs and a stable, easy process controlling are major advantages in terms of application. Besides hot corrosion protective single layers, MCrAlY coating systems are used as bond coats for ceramic thermal barrier coatings (TBC). But HVOF sprayed MCrAlY coatings show a comparatively low surface roughness which leads to a poor adhesion of the ceramic top layer, restricting the application area of HVOF. This paper deals with a development project which aims on roughness enhancement of HVOF sprayed MCrAlY coatings in order to improve the bonding properties of the TBC. In the project’s framework, several HVOF systems and different powders were investigated. Parameter sets were developed considering both a high surface roughness and a low level of defects in the coating.
Characterisations and Corrosion Resistance of HVOF Cr3C2-NiCr on Ni-Base Superalloys at 900°C in Molten Salt Environment
Authors: Sidhu T.S. , Prakash S. , Agrawal R.D. 
Published: September 2022

Abstract
In this study, high velocity-oxy fuel (HVOF) technique was used to deposit Cr3C2-NiCr coating on the Ni-base superalloys for their hot corrosion applications. The coatings were characterised with regard to coating thickness, porosity, microhardness and microstructure. The hot corrosion behaviours of the bare and Cr3C2-NiCr coated superalloys were studied after exposure to molten salt (Na2SO4-60%V2O5) at 900°C under cyclic conditions. Optical microscopy, XRD, SEM/EDAX and EPMA techniques were used to characterise the coatings. The thermogravimetric technique was used to establish kinetics of corrosion. The structure of the as sprayed Cr3C2-NiCr coating mainly consisted of γ-nickel solid solution with very low intensity peaks of Cr7C3 and Cr2O3 phases. Some porosity (less than 1.5%), inclusions, unmelted and semi-melted powder particles were observed in the structure of the coatings. Coating microhardness values were found to be in the range of 850-900 Hv (Vickers hardness). The Cr3C2- NiCr coating was resistant to hot corrosion in the given molten salt environment at 900°C. The hot corrosion resistance imparted by Cr3C2-NiCr coatings may be attributed to the formation of oxides of nickel, chromium, and spinels of nickel and chromium.
A Novel Nano-Composite Wire Material: The Low Cost and Enhanced Properties Coating Design
Authors: Georgieva P. , Thorpe R. , Yanski A. , Seal S. 
Published: September 2022

Abstract
Due to their enhanced mechanical properties and high range applications in severe environments use, there is ongoing research in the area of amorphous metallic glasses and nanostructured materials. The science and mechanisms leading to these exceptional properties are discussed herein. The arc sprayed coatings produced for study in this paper show remarkable performance and are analyzed in-depth using advanced characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Additional analysis of the mechanical properties of the coatings show enhanced strength and hardness, good wear and corrosion properties, along with high temperature corrosion and oxidation resistance.
Mechanical Properties of Plasma Sprayed Alumina-Zirconia Nano-composite Film
Authors: Sodeoka S. , Suzuki M. , Inoue T. 
Published: September 2022

Abstract
Alumina-zirconia nano-composite coating were fabricated by plasma spraying using agglomerated feedstock from alumina and yttria partially stabilized zirconia fine powders of about 100 nm in diameter. The coating was very dense and showed the striped contrast in the splats. XRD analysis and TEM observation revealed that the splats contained gamma-alumina and tetragonal-zirconia crystals, which sizes were under 10 nm. The striped contrast in the splats corresponded to the inhomogeneous distributions of these crystals. To investigate the mechanical properties of this nano-composite coating, micro-hardness and fracture toughness were measured. The critical strain energy release rate of nano-composite coating was 106.4 J/m2, which was two times larger than YSZ coating.
Nanostructured Abradable Coatings for High Temperature Applications
Authors: Lima R.S. , Marple B.R. , Dadouche A. , Dmochowski W. , Liko B. 
Published: September 2022

Abstract
Nanostructured yttria stabilized zirconia abradable coatings were produced via air plasma spray (APS) and compared to conventional abradable coatings based on the composite CoNiCrAlY+BN+polyester also sprayed via APS. The microstructures of the coatings were analyzed using SEM and the hardness determined via Rockwell Y measurements. It was possible to engineer nanostructured abradables with a high degree of plasticity by controlling the amount, morphology and distribution of the nanostructured phase embedded in the coating microstructure. Room temperature rub-rig tests were performed for both types of coatings under different blade tip speeds and seal incursion rates simulating operating conditions of gas turbines. The nanostructured abradables exhibited good performance indicating that abradable coatings engineered in this fashion have potential for industrial application at elevated temperatures.
Nanophased WC-12Co Thermal Spray Coatings for Wear Resistant Applications
Authors: Petsas N. , Papapanos G. , Vardavoulias M. , Moutsatsou A. , Celis J.P. , Matteazzi P. 
Published: September 2022

Abstract
The purpose of the present study is to investigate the influence of critical HVOF spray parameters on mechanical properties of WC–12Co coatings obtained from nanophased powder used as feedstock material. A Taguchi design of experiments approach was used for the selection and optimization of process parameters and coating properties. An L9 table was used for the evaluation of the effect of spray distance, oxygen/fuel ratio, gun traverse speed and feed rate on coating microhardness, adhesion strength, porosity and deposition efficiency – thickness. Results show clearly that each parameter affects in a different way and percentage each property. Furthermore, the comparison of XRD data with a conventional WC–12Co coating indicates that the nanostructure of the initial powder is maintained in the coating, whereas in the conventional one the formation of W2C phase is evident. Finally, fretting tests show similar behavior in terms of friction coefficient, but a significant improvement regarding wear resistance in the case of the nanophased coating.
Impact of Partially Molten Plasma-Sprayed Zirconia Particles on Glass Surfaces
Authors: McDonald A. , Chandra S. , Moreau C. 
Published: September 2022

Abstract
Plasma-sprayed yttria-stabilized zirconia particles (~40 µm diameter) were photographed during impact (velocity ~200 m/s) on a glass surface that was maintained at either room temperature or 400°C. A droplet that approached the surface was sensed using a photodetector and after a known delay, a light source was triggered to illuminate the particle in order to photograph it with a charge-coupled device (CCD) camera. A rapid two-color pyrometer was used to collect the thermal radiation from the particles to follow the evolution of their temperature and size, in-flight and after impact. The fully molten particles spread into a thin liquid splat after impacting the surfaces. The partially molten particles disintegrated into small satellite fragments immediately upon impact. The surface area, as indicated by the pyrometric signals, of the partially molten particles during spreading were almost an order of magnitude smaller than that of the fully molten particles. The pyrometric signals, characteristic of the impact of partially molten zirconia, provide a novel method of identifying partially molten ceramic particles after impact on a flat surface.
Mapping Deposition Parameters and Microstructures of Plasma Sprayed Spinel
Authors: Samadi H. , Coyle T.W. 
Published: September 2022

Abstract
Magnesia-alumina spinel (MgAl2O4) is an oxide ceramic with broad applications as a high temperature and corrosion resistant material. Its moderate coefficient of thermal expansion (7-8 x 10-6 K-1) may allow it to be used as a plasma spray coating on metallic substrates with coefficients of thermal expansion of ~12x10-6 K-1. Two important factors affecting the microstructure and properties of plasma sprayed coatings are the particle temperature (Tp) and particle velocity (Vp) in the plasma jet. The particle temperature and velocity are influenced by a substantial number of operating parameters. Using a statistical design of experiments approach, deposition parameters, microstructure, and physical properties of air plasma sprayed spinel coatings are linked through mapping versus in-flight particle temperature and velocity. The Tp-Vp maps provide a basis for depositing coatings with controlled structures.
Shrouded Plasma Processing of Solution Precursors
Authors: Sadangi R.K. , Shukla V. , Kear B.H. 
Published: September 2022

Abstract
A shrouded-plasma spray process is described for the production of a metastable powder, deposit or preform. A high enthalpy atmospheric DC arc-plasma torch is used as heat source and a solution precursor as feed material. An aerosol-or liquid-jet of solution precursor is delivered to a steady-state reaction zone within the shrouded-plasma flame, where rapid and controlled precursor decomposition occurs. Depending on the operating conditions, the precursor material is pyrolyzed, melted or vaporized, prior to quenching to form a metastable nano-sized powder. This method is capable of processing a host of metastable materials, including the difficult-to-process refractory metals, oxide and non-oxide ceramics, as well as their composites. In this paper, we will discuss our results on multi-component oxide systems.
HVOF Sprayed Multi-Scale Polymer/Ceramic Composite Coatings
Authors: Gupta V. , Niezgoda S. , Knight R. , Twardowski T.E. , Cairncross R.A. 
Published: September 2022

Abstract
The High Velocity Oxy-Fuel (HVOF) combustion spray process has been used successfully for spraying polymers and polymer-matrix composite coatings. Spraying of polymer ceramic composite powders produced by ball-milling nominal 60 ..m Nylon-11 with different size scale (7 nm to 15 µm) ceramic reinforcements is an effective method of producing semi-crystalline micron and nano-scale reinforced composite coatings. Polymer matrix composite coatings with nominal 10 vol. % of different size scale silica and alumina reinforcements have been produced. The levels of filler loading in both the feedstock powders and HVOF-sprayed coatings were determined by thermo-gravimetric analysis (TGA) and compared using ashing. Particle size analysis, microstructural characterization and the elemental compositions of the feedstock powders and as-sprayed coatings were determined by optical and scanning electron microscopy and energy dispersive spectroscopy. The influence of dispersion, distribution and size of the reinforcing phase was studied and correlated to coating microstructure and process parameter variations. The scratch resistance of the coatings was measured as a function of reinforcement size and compared with those of the pure HVOF-sprayed Nylon-11 coatings.
Effect of Reinforcement Size on the Scratch Resistance and Crystallinity of HVOF Sprayed Nylon-11/Ceramic Composite Coatings
Authors: Niezgoda S. , Gupta V. , Knight R. , Cairncross R.A. , Twardowski T.E. 
Published: September 2022

Abstract
The high velocity oxy-fuel (HVOF) combustion spraying of ball-milled Nylon-11/ceramic composite powders is an effective, economical and environmentally sound method for producing semi-crystalline nano- and micron-scale reinforced polymer composite coatings. Polymer matrix composite coatings reinforced with multiple scales of ceramic particulate materials are expected to exhibit improved load transfer between the reinforcing phase and the matrix due to interactions between large and small ceramic particles. An important step in developing multi-scale polymer matrix composite coatings and associated load transfer theory is determining the effect of reinforcement size on the distribution of the reinforcement and the properties of the composite coating. Composite feedstock powders were produced by dry ball milling Nylon-11 with fumed silica particles of 7, 20 and 40 nm, with fumed alumina particles of 50 and 150 nm, and with white calcined alumina 350 nm, 1, 2, 5, 10, 20, 25 and 50 µm at 10 % by volume overall ceramic phase loadings. The effectiveness of the ball-milling process as a function of reinforcement size was evaluated by SEM, EDS microanalysis and by characterizing the behavior of the powders during HVOF spraying. The microstructures of the as-sprayed coatings were characterized by optical microscopy, SEM, EDS and XRD. The reinforcement particles were found to be concentrated at the splat boundaries within the coatings, forming a series of interconnected lamellar sheets with good 3-dimensional distribution. The scratch resistance of the coatings improved consistently and logarithmically as a function of decreasing reinforcement size and compared to those of HVOF sprayed pure Nylon-11.
Implementation of Neural Networks into Modern Process Control Equipment
Authors: Schmitt R. , Doeren J. , Bobzin F. , Lugscheider E. , Ernst F. 
Published: September 2022

Abstract
Previous investigations of thermal spraying processes have shown that the relations between process parameters and the objective measurements are very complex. An approved approach to control complex processes is the application of Neural Networks (NN). Thus, Neural Networks have been designed to control the process of APS and HVOF spraying. Feed forward Neural Networks (Multi Layer Perceptron, MLP) are used. They are able to control a process. The way to train the Neural Network is to conduct as many experiments as possible, this is the major difficulty for the industrial use of Neural Networks. To save time and money DoE (Design of Experiments) is used to create an optimal experimental plan for the training. For testing the implementation of Neural Networks coatings are sprayed with APS, using DoE. The Neural Networks are combined with the particle flux imaging (PFI) tool. In future this combination will be able to provide an open loop control for thermal spray processes. The Neural Networks will be integrated with the software of the PFI-unit in order to create an easy to handle and affordable process control device. First experiments have been done with the APS process by spraying ZrO2 onto steel substrates. Afterwards the porosity of the coating was correlated to the recorded images and to the process parameters.
Influence and Significance of Noise Factors in Plasma Sprayed Surface Coatings
Authors: Bobzin K. , Lugscheider E. , Ernst F. , Zwick J. , Richardt K. , Landes K. , Forster G. 
Published: September 2022

Abstract
The number of parameters influencing the plasma spraying process is very high. Only a part of these parameters can be controlled online; some of them such as gas flows, current, voltage and spraying distance can be controlled easily, others such as particle temperature and velocity can only be controlled with substantially higher effort. As differences from parameter values preinstalled or given at the start of the process, the noise factors affect the coating properties in different ways and show big effects on the coating quality. Nevertheless there is only little knowledge about the significance of several noise factors and about the influence of small process parameter fluctuations on the coating properties. Because some of these noise factors such as plasma torch degradation cannot be avoided, the aim of this work is to determine the sets of coating parameters, where the influence of noise factors is minimized. This should be achieved by using online diagnostic tools, that afford the observation of fast and easy controllable process characteristics. On the other hand process errors shall be identified in an early process stage using appropriate diagnostic methods.
A New Approach to Online Thickness Measurement of Thermal Spray Coatings
Authors: Nadeau A. , Pouliot L. , Nadeau F. , Blain J. , Berube S.A. , Moreau C. , Lamontagne M. 
Published: September 2022

Abstract
In the past ten years, significant progress has been made in the field of advanced sensors for particle and spray plume characterization. However, there are very few commercially available technologies for online characterization of the as-deposited coatings. In particular, coating thickness is one of the most important parameter to monitor and control. Current methods such as destructive tests or direct mechanical measurements can cause significant production downtime. This paper presents a novel approach that enables online, real-time and non-contact measurement of individual spray pass thickness during deposition. Micron-level resolution was achieved on various coatings and substrate materials. The precision has been shown to be independent from surface roughness or thermal expansion. Results obtained on typical HVOF and plasma sprayed coatings are presented. Finally, current fields of application, technical limitations and future developments are discussed.
Effect of Substrate Surface Topography and Temperature, on Millimeter and Micrometer Sized Splat Formation and on Thermal Contact Resistance
Authors: Cedelle J. , Vardelle M. , Fauchais P. , Tanaka Y. 
Published: September 2022

Abstract
Many properties (thermal, electrical, mechanical) of thermal sprayed coatings are strongly linked to the real contacts between the “piled-up” splats. The quality of this contact depends on droplet parameters at impact (size, temperature, velocity) and substrate parameters (temperature, topography). Two different techniques have been developed in order to study the plasma sprayed particle behaviour at impact. The first one allows direct observation under direct current (dc) plasma spray conditions, while the latter one, based on the millimetre sized free falling drop, enables the visualization of flattening phenomena, but at larger scale. These two techniques bring complementary approaches and results. The latter show that flattening time and cooling rate of the lamellae (metallic and ceramic) are improved with the stainless steel substrate surface modification at the nanoscale when corresponding to a positive skewness parameter obtained by preheating it over the transition temperature. Experiments of wettability show that the presence of nanopeaks increases the contact angle of the liquid on the substrates and reduces thermal contact resistance at interface. It has also been shown that, when adsorbates and condensates are not eliminated from the surface, even with a positive skewness, the thermal contact resistance is increased.