bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Contribution to Engine Pistons Life Time Improving by Means of Thermal Spray Coatings
Authors: Rosso M. , Ugues D. , Bechis F. , Groppetti R. , Scrivani A. , Bardi U. , Rizzi G. 
Published: June 2022

Abstract
Engine pistons are working components subjected to very high wear actions, mechanical and thermal stresses; moreover they can suffer damages due to pinking. Many solutions have been proposed, but there is still a large margin of improvement and strong efforts are made for improving performances and service life, taking into account for the requirements of fuel composition and of environment. Advantages can be obtained by the utilization of thermal spray coatings as protection against corrosion and pinking damages; on this matter the evolution of thermal spray processes and techniques offers suitable means. The aim of this paper is to evaluate the possibility to coat with NiCr alloys or with austenitic stainless steel (AISI 316L) the surface of engine pistons made by Al alloys. Coating layers, with thickness in the range of 200 ÷400 µm, have been sprayed, using Plasma Spray processes, on samples for metallographic investigation end test and on pistons directly. Optical and Scanning Electron Microscopy analyses were carried out on the cross sections to examine the microstructural features, while the hardness properties have been evaluated by means of both surface and cross-sectional measurements. Bend test is in progress to get information about the coating strain as well as about adhesion of the coating to the substrate. Finally the tested coatings have been applied directly on pistons and these are being tested on the test bench, evaluating the improvement of the service life.
Fabrication and Properties of TiO2 Photo-Catalytic Coatings by Thermal Spraying with TiO2-AI Agglomerated Powder
Authors: Matsusaka S. , Ohmori A. , Toki Y. 
Published: June 2022

Abstract
In the present study, anatase TiO2 photo-catalytic coatings were fabricated by plasma and HVOF spraying. In order to prevent the transformation from anatase to rutile phase, lower heat input conditions were adopted. For the improvement of bondability between coatings and substrate, anatase TiO2-Al agglomerated powder was used for the experiment. The microstructures of the coatings were characterized with SEM and XRD analysis, and the photo-catalytic characteristics of coatings were evaluated by the decomposition rate of acetaldehyde gas. Due to the addition of aluminum, thick coatings were formed even at lower heat input conditions in both plasma and HVOF spraying. The results of XRD analysis for the plasma sprayed coatings, however, indicated the disappearance of anatase phase and deoxidization of TiO2 to Ti3O5 or magnetite phase. On the other hand, high anatase/rutile ratio and high photo-catalytic efficiency were achieved for the coatings formed by HVOF spraying. The temperature measurements of flying particles were also carried out using DPV-2000. As results, significant increase in temperature of TiO2-Al particles was observed compared with the case of using pure TiO2 particle. These results suggest that a chemical reaction between TiO2 and Al occurs during thermal spraying.
HVOF Sprayed Hydroxyapatite Coatings: Powders’ Melting State and Mechanical Properties
Authors: Li H. , Khor K.A. , Cheang P. 
Published: June 2022

Abstract
In the present study, hydroxyapatite coatings were deposited on Ti-6Al-4V alloy substrate by high velocity oxy-fuel (HVOF) spray technique. The as sprayed HA powders and coatings were analyzed with the aim to reveal the melting state of HA powders and its influence on coating properties. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were employed for the characterization of the starting powders and as-sprayed coatings. Differential scanning calorimetry (DSC) was performed to determine the recrystallization temperature of the amorphous phase in HVOF HA coating. Results show that different melting state of HA powders can be achieved through altering HA powder size and/or spray parameters. XRD result reveals that the as sprayed HA coating made from large powders with size of ~50 µm is composed of crystalline HA and very small amount of a-tricalcium phosphate (TCP). While the coatings deposited using fine powders around 30 μm demonstrated a lot of amorphous phase besides crystalline HA and small amount of a-TCP. The recrystallization temperature of the amorphous phase in HA coating is ~720°C. The adhesive strength of the HVOF sprayed HA coatings is ~31MPa and is largely dependent on the melting state of HA powders. This suggests that the fully melted state of the feedstock can result in the formation of amorphous phase, and simultaneously decrease the adhesive strength. It also suggests that the melted fraction of the powders is the most critical factor influencing the adhesive strength and phase composition of HVOF HA coatings. The partial melting state of HA powders is beneficial in terms of adhesive strength and crystallinity.
Corrosion Resistant Coatings for Gas Turbine Exhaust Stack Applications
Authors: Mutasim Z. 
Published: June 2022

Abstract
Land-based gas turbine exhaust stacks are typically made of low carbon steels, and when used in very harsh industrial environments, they are subjected to corrosion attack leading to material degradation and loss of structural integrity. To maintain acceptable condition, various types of corrosion resistant paints and coatings are used. These include aluminum-based polysiloxane organic paints, as well as wire arc sprayed stainless steel and aluminum coatings. Aqueous corrosion protection and thermal stability up to 538°C are required. Development and testing of various coating systems was conducted and presented in this paper. Laboratory and engine field-testing demonstrated the best performance for sealed aluminum wire arc sprayed coatings
Effect of Bond Coat Processes and Surface Characteristics On the Failure Mechanism of Thermal Barrier Coatings
Authors: Ding Z. , Knight R. , Smith R.W. 
Published: June 2022

Abstract
This paper explores the effect of bond coat processes and surface characteristics on the failure mechanism of thermal barrier coatings (TBC's). TBC's consist of a 300µm thick air plasma sprayed (APS) top coating of ZrO2-8Y2O3 w% and CoNiCrAlY bond coats which were deposited using low pressure plasma spray (LPPS), shrouded air plasma spray (SPAS) and high velocity oxy-fuel (HVOF) combustion spray and different size powder. Bond coat surface profiles were measured by profilometric techniques and surface roughness was calculated according to the measured results. TBC performance and failure mechanisms were evaluated by adhesive bond strength testing, image analysis measurements of porosity, thermal cycling testing. X-ray diffraction and microstructural analyses. Research results show that bond coat deposition processes and surface characteristics had significant effects on the thermal cycling lifetime and failure mechanism.
Kinetics of Thermally Grown Oxide at Interface Between Thermal Barrier Coatings and MCrAlY Bond Coatings
Authors: Ogawa K. , Shoji T. , Masuda T. 
Published: June 2022

Abstract
In recent years, thermal barrier coatings (TBC) have been used in advanced gas turbine plants for improved durability and performance. Typically, TBCs consist of an inner layer of metallic bond coating (MCrAlY) and an outer layer of ceramic top coating (8wt% yttria stabilized zirconia (YSZ)). According to several studies, the failure of coating is induced by thermal stress due to formation of oxides at the interface between YSZ and MCrAlY. Therefore, it is important to investigate kinetics of oxidation at the interface. In this work, the interface between YSZ and MCrAlY is studied and characterized. TBC specimens are thermally aged at 1000 deg. C to simulate the surface temperature of first rotating blades. After aging, thermally grown oxide (TGO) is formed at the interface. The TGO has two layers of different contrasts. One layer is black, and is closer to MCrAlY; the other layer is gray, and is closer to YSZ. The black layer is identified as Al2O3 by energy dispersive X-ray spectroscopy (EDX) and electron probe micro analyzer (EPMA). The EDX and EPMA spectra of the gray layer contain various peaks of Al, Cr, Co, Ni, and O, which suggests that the layer can be mixed oxide which is a combination of NiO, CoO, Cr2O3, and Ni(Cr, Al)2O4. However, the outer layer of mixed oxide contains only Cr and O. Accordingly, Cr2O3 forms at the outer layer of mixed oxide, and the other oxides are distributed at the inner layer of mixed oxide. The thickness of the two oxide layers increases with aging time. While the formation of mixed oxide layer obeys a parabolic law, the formation of an alumina layer cannot be expressed in terms of a parabolic law. Due to the formation of protective mixed oxide on the alumina layer, the oxidation rate of alumina decreases as the thickness of mixed oxide increases.
Reaction Diffusion Behavior of Thermally Sprayed MCrAlY Coatings On Ni-Based Super Alloys
Authors: Teratani T. , Tani K. , Harada Y. 
Published: June 2022

Abstract
The gas turbine blades in a severe environment are overlaid with MCrAlY coatings by Low Pressure Plasma Spray (LPS) process for protection against hot corrosion. However, the service life of each blade is limited by damage due to embrittlement layer, which is formed by reaction diffusion at the interface between the coating and the substrate. Reaction diffusion behavior between the CoNiCrAlY coatings and substrates was investigated. In addition, high-temperature oxidation behavior of the CoNiCrAlY coating by LPS was evaluated. The CoNiCrAlY coatings for reaction diffusion test were carried out by 3 kinds of spray process (LPS, High Velocity Oxygen Fuel Spray: HVOF, Atmospheric Plasma Spray: APS) on 2 kinds of substrate (Directional Solidification and Single Crystal Ni-based super alloys). It has been found that the CoNiCrAlY coating by APS inhibited the reaction diffusion at the boundary of the coating and the base material as compared with LPS coating. It was also confirmed that the protective dense layer of aluminum oxide against hot corrosion was formed in the surface of the CoNiCrAlY coatings by LPS.
Removal of Thermal Barrier Coatings From Turbine Blades: A Comparison of Mechanical and Chemical Methods
Authors: Scrivani A. , Groppetti R. , Ianelli S. , Bardi U. , Ballerini G. , Bonacchi D. , Fantini M. , Rizzi G. 
Published: June 2022

Abstract
Thermal barrier coatings are gaining considerable importance for the improvement the energetic efficiency of turbines. These materials are often applied on the surface of blades and are based on a layer of antioxidation material (mainly MCrAlY alloys) and a top layer that acts as proper thermal barrier (normally Yttria partially stabilized Zirconia). Coating removal is an important aspect in the production of these blades. "Decoating" or "stripping" is needed for the production of new components as well as for the reconditioning of existing ones. The present paper is dedicated to the comparison of different stripping methods and to the characterization of the blades surface after removal of thermal spray coatings both of Zirconia and of MCrAlY. The results reported here show that chemical stripping is particularly suitable for MCrAlY coating removal and does not affect the substrate. Water jet stripping can successfully be used for Zirconia-MCrAlY system removal although care is needed to avoid substrate damage. Salt bath technologies have been formed to be effective for TBC removal but not for MCrAlY removal.
Induction Plasma Synthesis of MoSi2 Ultrafine Powders
Authors: Gutierrez S. , Gitzhofer F. 
Published: June 2022

Abstract
Ultrafine MoSi2 powders have been synthesized from commercial MoSi2 powders by using an Ar-H2 induction plasma. Reactor pressure and plate power were taken as the experimental parameters to optimize the phase as well as the size distribution of ultrafine MoSi2 powders. The powders were collected from porous metal fibers. They were composed of both metastable hexagonal structure (β-MoSi2) and stable tetragonal structure (α-MoSi2) with small levels of Mo5Si3 and free silicon.
Plasma Spray Dissociation of ZrSiO4 As the Basis of Forming ZrO2-Mullite Composites From a ZrSiO4 + AI2O3 Mixture
Authors: Li Y. , Khor K.A. 
Published: June 2022

Abstract
Zirconia is effective in improving the fracture toughness to a number of ceramics when introduced as a reinforcement either in the form of particulate, dispersed phase, or whiskers because of its unique tetragonal-monoclinic (t → m) transformation. In this paper, the authors attempt to prepare ZrO2 reinforced Mullite by plasma spraying mixtures of zircon and alumina. Pre-mixed powders of zircon (ZrSiO4) and alumina are injected into a dc plasma jet. The plasma sprayed particles are collected in distilled water and analyzed. The dissociation of zircon in thermal plasma is a well-established fact. The present investigation aims to utilize the plasma dissociation of zircon to produced ZrO2-toughened mullite from a zircon + alumina mixture. The results indicate that the plasma sprayed powders consist of zirconia, amorphous SiO2, zircon, and alumina. It was found that ball milling and plasma spraying could yield fine grained, even amorphous and chemically homogeneous, composite powders. Recrystallization of amorphous phases and formation of mullite occurred at about 1000 °C in plasma sprayed powders. This value is more than 500 °C lower than the formation of mullite in as-milled powders. Uniform coatings with good structural integrity were obtained by plasma spraying. The relative quantity of mullite in coatings after heat treatment is about 4 times as much as that obtained in the spheroidized powders. Preheat treatment of the spheroidized powder promoted dissociation of zircon. Zirconia remained as tetragonal under 1000 °C in the sprayed coatings.
HVOF Sprayed Hydroxyapatite/Titania Composite Coatings
Authors: Khor K.A. , Li H. , Cheang P. 
Published: June 2022

Abstract
As ceramic materials, the use of hydroxyapatite (HA) in clinical applications is severely limited by its intrinsic poor mechanical properties. The incorporation of some bioinert ceramics is believed to be a way to improve the mechanical reliability of HA matrix. HA coatings with titania addition were produced by using high velocity oxy-fuel (HVOF) spraying process in the present study. The mechanical properties of the as-sprayed coatings in terms of adhesive strength, shear strength and fracture toughness were investigated aiming to reveal the reinforcing effect of the titania addition in HA coatings. Qualitative phase analysis through X-ray diffraction (XRD) showed that mutual chemical reaction between TiO2 and HA occurred during coating formation, from which CaTiO3 was resulted. Totally unmelted titania powders were observed which suggests that the mutual reaction locates at HA/TiO2 splats' interface. Significant influence of coating microstructure on mechanical properties was revealed. As the content of titania in HA coatings reached 20vol%, the adhesive strength decreased largely. As the content of titania reached 30vol%, the further augmentation of the adhesive strength of is possibly resulted from the improved coating microstructure. The fracture toughness exhibited the values of 0.48 Mpa ⋅ m½ 0.60 Mpa ⋅ m½ and 0.67 Mpa ⋅ m½ for pure HA coating, 10vol% TiO2 blended HA coating and 20vol% TiO2 blended HA coating, respectively.
Abradable Coatings for Low-Temperature Applications
Authors: Nava Y. , Mutasim Z. , Coe M. 
Published: June 2022

Abstract
Various low-temperature abradable coatings for applications reaching 482°C were evaluated with the purpose of being applied onto the compressor spacers of an 11 MW land-based gas turbine engine. The coating is intended to reduce the compressor rotor tip-clearance, and is expected to increase the compressor efficiency by a range of 0.5 to 1%. This study evaluated physical and metallurgical characteristics, abradable and oxidation-resistance properties of plasma-sprayed AlSi-BN, NiCrFeAl-BN and quasicrystal AlCuFeCr, and flame-and plasma-sprayed NiCrFeAl-BN.
Developments of Plasma Sprayed Ceramic Coatings
Authors: Ding C.X. , Liu X.Y. , Zheng X.B. 
Published: June 2022

Abstract
Recent developments in the field of plasma sprayed ceramic coatings at Shanghai Institute of Ceramics (SIC) are presented. Nano-titania and nano-tungsten carbide coatings were prepared. Their structure and properties were detected. The super hard B4C coating was deposited by APS. The physical and mechanical and anti-irradiation properties of B4C were measured. Wollastonite coating was deposited and its bioactivity has been tested. The results obtained indicated that (1) nano-titania coating possessed porous structure and unique electric properties; (2) nano-WC-Co coating exhibited notable wear resistance; (3) B4C coating was excellent irradiation resistance and (4) the carbonate-containing hydroxyapatite was formed on the surface of wollastonite coating, which indicated that this coating has excellent bioactivity.
On the Tailoring of Spray Dried Thermal Spray Powders
Authors: Keller N. , Bertrand G. , Comas B. , Coddet C. 
Published: June 2022

Abstract
In thermal spray, it is well established that tailoring the powder characteristics is of major importance to achieve reproducible coatings on a microstructural and chemical point of view. Among the techniques developed to produce thermal spray powders, spray drying has proved to be the most versatile process. The spray drying method consists in spraying a slurry containing finely dispersed particles of the materials to be agglomerated. However, in order to prepare specific thermal spray powders, two steps have to be mastered: the slurry stability and the spray drying operating conditions. The present study was focused on the relationships that exist between the slurry rheology, the powder morphology and the coating properties. This work was performed on a model material namely Al2O3. In a first part, the effects of the surfactant percentage and pH on the stability of the suspensions were determined. The evolution of the viscosity of the slurries versus the amount of binder was measured. In a second part, these slurries were used to prepare spray-dried powders. The effects of some process parameters such as atomizing air pressure and slurry feed rate on the granule characteristics (morphology, density, particle size distribution, and powder flow ability) were investigated. Finally, some coatings were deposited using the APS technique on steel substrates from the non-sintered spray-dried powder previously realized. The coating morphology and the crystallographic structure were evaluated as a function of the spraying conditions.
A Comparative Study of the Deposition of Chromium Carbide Based Metal Matrix Composites by Axial Plasma Spray, Air Plasma Spray and High Velocity Oxygen Fuel
Authors: Scrivani A. , Groppetti R. , Ianelli S. , Bardi U. , Ballerini G. , Bertini S. 
Published: June 2022

Abstract
The present work has the purpose of comparing different thermal spraying techniques, namely axial plasma spray, standard air plasma spray and high velocity oxygen flame (HVOF), for depositing metal matrix composites, in this case chromium carbide nickel-chromium based. The quality of the coatings deposited by these three techniques has been assessed in terms of structural characteristics (porosity, oxide concentration, unmelted particles presence, etc.) and of mechanical characteristics (hardness, adhesion, etc.) as well as surface morphology. A specific efficiency test has been carried out to compare the three examined technologies. The results of the present study indicate that, against a slightly decrease in the quality of the film in terms of structural and mechanical properties, axial plasma sprayed coatings can be sprayed with a higher efficiency in comparison to the traditional technologies.
Heating Effect of Flame Impingement on Polymer Coatings
Authors: Gawne D.T. , Zhang T. , Bao Y. 
Published: June 2022

Abstract
A computational model of the effect of the tail end of the flame on the temperature of polymer coatings during thermal spraying is presented. The low thermal conductivity of polymers results in a substantial build up of temperature at the surface of the coating and large temperature gradients are developed throughout its thickness. This is particularly problematic for polymer deposition owing to their low decomposition temperatures. The model quantifies the heat transfer from the impinging flame and the in-coming feedstock particles to the coating and the subsequent heat flow into the substrate and surroundings. The work shows that the heat input from the in-coming particles can be neglected in first-order computations. The scanning action of the flame across the substrate is simulated and the temperature profiles within the coating and substrate are calculated. The predictions are consistent with the experimental measurements. The model shows that overheating of polymer coatings can readily occur during combustion flame spraying and indicates remedial measures.
Mechanical Properties of Thermal Spray PEEK Coatings
Authors: Liao H. , Coddet C. , Simonin L. 
Published: June 2022

Abstract
The influences of process parameters on the microstructure of PEEK coatings deposited by flame spraying were analyzed by different physical and thermal methods, considering the density, the hardness and the Young's modulus. The cooling rate of the coating after spraying leads to large variations of the microstructure which evolves between the crystalline and amorphous states. Amorphous coatings exhibit less residual stress than semi-crystalline ones, which has an influence on the friction behavior.
Structure and Thermal Conductivity of Flame Sprayed Polyamide 11 Coatings Filled With Al2O3, AIN and BN Ceramics
Authors: Leivo E.M. , Kellberg T.H. , Vuoristo P.M.J. , Mäntylä T.A. , Kolari M.J. 
Published: June 2022

Abstract
Polymer ceramic composite coatings were applied by flame spraying on preheated steel substrates. Polyamide (PA 11, nylon) powder was blended with alumina (Al2O3), aluminium nitride (AIN) or boron nitride (BN) powder with two different filler content to increase thermal conductivities of polymer coatings. Morphologies and particle sizes of polyamide and filler powders were examined by scanning electron microscope and laser scattering methods. Coating structures and thicknesses of composite coatings were studied by the polished cross sections. Thermal conductivities were measured by hot disc method. Thermal conductivities of polyamide coatings increased from 30 % up to few times by blending ceramic filler material on PA 11 powder. Structures of composite coatings were dense and filler materials were clearly observed in polyamide matrix.
Sprayed Composite Coating of High Performance Thermoplastics
Authors: Kawase R. , Tanaka Y. 
Published: June 2022

Abstract
Polyetherether-ketone (PEEK) and Polyphenylene-sulfide (PPS) are high performance thermoplastics having high heat resistance and high corrosion resistance. Composite powders of PEEK / Alumina (Al2O3) with different Al2O3 content have been produced by four processes, which are Mixing (MX) process. Mechanical granulation (MG) process. Melting-crush (MC) process and Heating-granulation (HG) process. PEEK / Al2O3 composite powders have been sprayed with High Velocity Air Fuel (HVAF) spray system. The microstructures of these composite coatings have been evaluated and the properties of these composite coatings have been investigated by the corrosion test, the adhesion test, the ACT-JP test and the abrasive wear test. It was recognized that all the composite coatings containing Al2O3 powder have a good wear resistance. PPS / Al2O3 composite powders have been sprayed with HVAF spray system onto substrate of various pre-heat temperature. It was recognized that the adhesion strength of the composite coatings increases with increasing pre-heat temperature of substrate.