bluuebunny/crossref_metadata_2025 huggingface dataset:
Fully Nano-Equiaxed-Structured Thermal Barrier Coating Deposited Using Very-Low-Pressure Plasma Spray
Authors: Gao Yang , Zhao Yan , Sun Cheng-qi , Yang D.-M. , Gao Jianyi
Published: August 2022

A novel fully nano-equiaxed-structured thermal insulation Y2O3-stabilised ZrO2 (YSZ) coating was first successfully deposited using very-low-pressure plasma spray (VLPPS) and the agglomerates feedstock from nanometer-sized powders. The microstructure of fully nano-equiaxed-structured coating is different from that of a “bimodal microstructure”, which is currently the dominant nanostructured coating. This desirable structure in the new TBCs appears to be responsible for their improved thermal cycling lifetimes and reduced thermal conductivity relative to those of conventional plasma-sprayed TBCs with lamellar structures or bimodal structures. Preliminary results from experiments aimed at understanding the VLPPS deposition mechanisms suggest that the nanometre-scale equiaxed in the coating are formed from original nano-particles, they underwent melted in the low pressure plasma plume and solidification onto the substrate. The VLPPS method, which offers some unique advantages over the conventional plasma-spray process, is generic in nature and can be potentially used to deposit a wide variety of ceramic coatings for diverse applications.
Homogenization of Coating Properties in Three-Cathode Atmospheric Plasma Spraying by Use of Advanced Diagnostics and Numerical Simulation—Investigations of Suspension Plasma Spraying (SPS)
Authors: Zimmermann Stephan , Schmettlach Sven , Weber Sebastian , Marques Jose , Forster Guenter , Landes Klaus , Schein Jochen , Lummer Christin , Knödler Patrick , Kresnik Simon , Prehm Jens , Möhwald Kai , Maier Hans J.
Published: August 2022

This paper discusses a research project with the goal of homogenizing the properties of three-cathode plasma sprayed coatings through the use of advanced diagnostics and numerical simulations. The approach included the development of a suspension injection setup, the determination of plasma and suspension behavior through diagnostic methods such as computer tomography and particle image velocimetry, and the analysis of coating formation through computational fluid dynamics and finite element analysis. The results of their investigations are presented, including tomographic reconstructions of temperature distribution, suspension behavior measurements, and coating analysis. The paper concludes with a discussion of the future directions of their research and the potential impact on the field of thermal spray coatings.
Improved Corrosion Resistance of Plasma-Sprayed NiCr-Mo Coating with Shell-Core-Structured Powder by Improving Lamellar Interface Bonding
Authors: Tian Jia-Jia , Yang Guan-Jun , Li Cheng-Xin , Luo Xiao-Tao , Li Chang-Jiu
Published: August 2022

The bonding between flattened particles in plasma-sprayed metal coatings dominates their corrosion behavior by influencing the porosity in coatings, especially the porosity connected to the substrate for coatings used in a corrosive environment. Therefore, how to efficiently enhance the lamellar interface bonding in metallic coatings has been an important issue which has not been settled effectively. In this study, a shell-core structured powder particle designing with cladding spherical Ni20Cr powders with refractory molybdenum as alloying element is proposed to limit the evaporation of low melting point elements and subsequently raise particle temperature significantly high enough to cause impact melting. Results show that a dense coating with much low porosity was obtained due to the improved lamellar interface bonding by gas shrouded plasma spraying of the composite NiCr -Mo particles. Electrochemical method was employed to evaluate the polarization behavior of the NiCr - Mo coating to estimate its connected porosity. It was revealed that NiCr-Mo coating of excellent corrosion resistance with low connected porosity can be obtained by designing the shell-core-structured powder.
Influence of Gas Flow Parameters and Nozzle Design on Secondary Atomization in a Rotating Twin-Wire Arc Spray System
Authors: Devillers Jean-Baptiste , Liao Hanlin , Coddet Christian , Malhaire Jean-Marie
Published: August 2022

Internal coating of cylinders has always been a challenge for cars engineers. Driven for more than two decades now by the ecological and economical constrains applied to the automotive industry, it constitutes a dynamic way of research and development for industrial applications. One of the most economical processes for this kind of coatings is the rotating twin-wire arc spray (TWAS) system. Meanwhile the actual quality and the performances of the corresponding coatings still leave place for some improvements. Therefore, in the work presented here, attention was paid to the second atomization phenomena in a TWAS system considering the influence of the gas flow parameters on the particles’ morphology and deposition behavior. Numerical modeling of the plume and comparisons between several designs of the second atomizing units were also considered.
Influence of Surface Oxide Film on Deposition Behavior of Cold Spray Emulated Particle by Single Particle Shot System
Authors: Ito K. , Ichikawa Y. , Ogawa K.
Published: August 2022

In a cold spray technique (CS), which used for making dense and thick metallic coatings, the fine solid metallic particles are impinged and deposited on a substrate at subsonic or supersonic velocity. The property and performance of a CS metallic coating significantly depends on the bonding state of particle-substrate and particle-particle interfaces. Therefore, the deposition mechanism of the CS particles has become one of the most important research targets. However, it is difficult to experimentally evaluate the deposition mechanism due to numerous impingements of very fine particles with various size and shape. In this study, in order to evaluate the deposition mechanism, a CS emulated environment was created by a single particle shot system (SPSS) in which spherical particle with 1 mm diameter is impinged on a substrate. The influence of substrate surface oxide film on deposition behavior of a spherical Al particle with 1 mm diameter was investigated. The thickness of surface oxide film on a substrate was controlled by heat treatment and estimated by X-ray photoelectron spectroscopy (XPS). Using the SPSS, Al particles were impinged on the substrates with different surface oxide film thicknesses. The critical velocity, which means the starting velocity for particle deposition, and the microstructure of deposited particle were evaluated. From the results, it was found that the surface oxide films on substrates play important roles on the deposition behavior of the Al particle.
Investigation of Flow Parameters in Wire Arc Thermal Spraying Using CFD Simulation
Authors: Farrokhpanah Amirsaman , Pershin Larry , Mostaghimi Javad , Naffrechoux Julien
Published: August 2022

Comprehensive study of the wire arc thermal spray technology will allow for better design and optimization of guns. In wire arc spray, a feed of two electrically-charged wires are melted using an arc. This bath of molten metal goes through an atomization process with a high pressure air being blown upon it. Flow of air will then carry the generated molten drops and deposits them on the substrate. The focus of this study is on the numerical simulation of wire arc sprays using ANSYS FLUENT software. Effects of geometrical parameters on resulting flow conditions and flow circulations inside the gun are studied. Simulation results help in better parameter selection for effective wire arc coating.
Investigation of the Bonding Mechanisms of Al Coatings on Ceramic Substrates Deposited by Cold Gas Spraying and Magnetron Sputtering
Authors: Drehmann R. , Grund T. , Lampke T. , Wielage B. , Wüstefeld C. , Motylenko M. , Schreiber G. , Rafaja D.
Published: August 2022

The present work builds on investigations of cold gas-sprayed Al coatings on Al2O3, which strongly indicated that heteroepitaxial growth is a possible mechanism supporting the adhesion between metal and ceramic at their interface. The present study was focused on the deposition of Al on further ceramic substrates (AlN, Si3N4 and SiC). In particular, it should be clarified whether the different ionicity of the chemical bonding in these substrate materials influences the interface formation or not. Aluminum coatings were deposited alternatively by using cold-gas spraying (CGS) and magnetron sputtering. In CGS coatings, the effect of substrate roughness, substrate temperature and powder fraction on the adhesion of the coating was investigated. The magnetron-deposited coatings were used to evaluate the role of the heteroepitaxy in the interface formation and to identify microstructure defects in the metal/ceramic interface, which are caused solely by the lattice misfit between the counterparts and not by the impact-induced deformation that is typical for cold gas-sprayed coatings. Interface characterization was conducted by scanning electron and high resolution transmission electron microscopies combined with XRD.
Lithium Iron Phosphate Coatings Deposited by Means of Inductively-Coupled Thermal Plasma
Authors: Major K. , Brisard G. , Veilleux J.
Published: August 2022

Lithium-ion batteries have high energy efficiency and good cycling life and are considered as one of the best energy storage device for hybrid and/or electrical vehicle. Still, several problems must be solved prior to a broad adoption by the automotive industry: energy density, safety and costs. To enhance both energy density and safety, the current study aims at depositing binder-free cathode materials using inductively-coupled thermal plasma. In a first step, lithium iron phosphate LiFePO4 powders are synthesized in an inductively-coupled thermal plasma reactor and dispersed in a conventional polyvinylidene fluoride (PVDF) binder. Then, binder-free LiFePO4 coatings are directly deposited onto nickel current collectors by solution precursor plasma spraying (SPPS). These plasma-derived cathodes (with and without PVDF binder) are assembled in button cells and tested. Under optimized plasma conditions, cyclic voltammetry shows that the electrochemical reversibility of plasma-derived cathodes is improved over that of conventional sol-gel derived LiFePO4 cathodes. Further results related to the substitution of iron with manganese in the SPPS precursors (LiMPO4, where M = Fe or Mn) are discussed.
Mechanisation of the Grit Blasting Process for Thermal Spray Coating Applications
Authors: Begg Henry , Riley Melissa , Lovelock Heidi de Villiers
Published: August 2022

The bond strength between a thermal spray coating and substrate is critical for many applications and is dependent on good substrate surface preparation and optimised spray parameters. While spray parameters are usually carefully monitored and controlled, most surface preparation is carried out by manual grit blasting, with little or no calibration of blast parameters. Blasting is currently highly dependent on operator skill and often surface finish is only assessed visually, meaning a consistent, reproducible surface profile cannot be guaranteed. Mechanised blasting offers the promise of more tightly controlled surface preparation and presents an opportunity to improve coating adhesion. This paper presents investigations on the effect of blast parameters (including blast pressure, standoff distance, media feed rate, blast angle, traverse speed and media size) on surface profile for a range of metallic substrates using a mechanised, robotic blasting system. Substrates were characterised using contact profilometry and non-contact focus variation microscopy.
Metal-Ceramic Nanocomposite Coatings Produced by HVOF Thermal Spray and In-Situ Precipitation of Ceramic Components for Tribological Applications
Authors: Schulz R. , Savoie S.
Published: August 2022

Protective coatings with high wear, erosion and corrosion resistance are of great importance in many fields of application and in particular, in the electric power generation sector. In this paper, the HP-HVOF (high-pressure high velocity oxy-fuel) technique is used to produce dense rapidly quenched metal-ceramic nanocomposite protective coatings. The powders for the thermal spray process are produced by high energy ball milling using mechanochemical displacement reactions to synthesize ceramic components in-situ at the nanometric scale. Boron nitride solid lubricant is used as a source of nitrogen and boron to precipitate nitride and boride phases in a corrosion resistant iron aluminide metal matrix. The formation of the hard phases during milling and/or thermal treatments is investigated using various analytical methods. The tribological properties of the coatings with and without ceramic additives are reported.
Modeling of the APS Process—From the Arc to the Coating Effective Properties
Authors: Bolot R. , Aubignat E. , Planche M.P. , Montavon G. , Allimant A. , Billières D.
Published: August 2022

Atmospheric Plasma Spray is widely used for tens of years to elaborate protective coatings on parts for several applications. However, our understanding of the APS process can still be improved, requiring a fine modeling of the process in parallel with some corresponding experiments. In the present work, a complete series of models was applied to reinforce our knowledge of the process: the case of an alumina coating was considered. A 3D CFD model was first used to study the internal arc within the torch. Interactions between the external plasma jet and the injected particles were then computed in a second step. At this level, the predicted in-flight particle characteristics were compared with some corresponding measurements recorded with the DPV 2000 diagnostic tool. A third model was then applied to investigate the particle flattening on the substrate/coating material. SEM pictures of coating cross-sections were then captured and a last model was finally applied to estimate the coating effective thermos-mechanical properties based on calculations performed directly on the SEM micrographs. This set of models allows investigating the APS process from the DC arc within the torch to the coating properties.
On the Relationship of Tungsten Composition to Coating Properties
Authors: Colmenares-Angulo Jose , Molz Ronald , Hawley David , Seshadri Ramachandran Chidambaram
Published: August 2022

Industry today has an increased awareness of environmental, health, and safety issues. This, together with recent Nuclear Regulatory Commission changes concerning source material (e.g. thorium) have added complexity in the supply chain of thoriated tungsten commonly used in plasma spray gun spares. In the interest of a safer and more sustainable work environment Oerlikon Metco has developed non-thoriated material solutions proven to have longer service life than conventional thoriated spares. This work reports on the effect, if any, caused by tungsten compositional changes and extended service life in coating properties. Microstructure, coating efficiency parameters, hardness, particle state and in-situ stress are evaluated over the duration of the nozzle, comparing coatings with thoriated and non-thoriated nozzles and electrodes with the same spray parameters.
Parametric Study of Plasma Torch Operation Using a MHD Model Coupling the Arc and Electrodes
Authors: Alaya M. , Chazelas C. , Vardelle A.
Published: August 2022

Coupling of the electromagnetic and heat transfer phenomena in a non-transferred arc plasma torch is generally based on a current density profile and a temperature imposed on the cathode surface. However, it is not possible to observe the current density profile experimentally. To eliminate this boundary condition and be able to predict the arc dynamics in the plasma torch, the electrodes were included in the computational domain, the arc current was imposed on the rear surface of the cathode, and the electromagnetism and energy conservation equations for the fluid and the electrodes were coupled. The solution of this system of equations was implemented in a CFD computer code to model various plasma torch operating conditions. The model predictions for various arc currents were consistent and indicated that such a model could be applied with confidence to plasma torches of different geometries, such as cascaded-anode plasma torches.
Splat Formation of Copper and Copper Alloy on Ceramic Substrate in Plasma Spray Process
Authors: Tran Anh T.T. , Hyland Margaret M. , Fukumoto Masahiro , Munroe Paul
Published: August 2022

In the present work, we have examined the role of active elements in controlling the extent of splashing of plasma sprayed splats. Splats of Copper (Cu) and Copper alloyed with Al, Zr were deposited by plasma spray or as free-falling droplet. The splat formation and splat-substrate interfaces were characterised using SEM and FIB. It was found that the presence of Zr, either in the splat material or the substrate, enhanced disk splat formation in free falling droplets. Similarly, the presence of aluminium in plasma sprayed Cu- 10%Al increased the portion of favourable disk-shaped splats compared to pure copper. It was also found that the disk-shaped splat proportion of Cu-10%Al at room temperature is nearly identical to that of Cu splat at 300°C, indicating that the addition of Al in the alloy leads to the improvement of splat formation, correlating with the improvement in the interface bonding with the substrate.
Structure and Mechanical Properties of Thick Copper Coating Made by Cold Spray
Authors: Leshchynsky V. , Maev R.Gr. , Strumban E. , Dzhurinskiy D. , Kocimski J. , Maeva E.
Published: August 2022

The main purpose of this study was to form cold sprayed copper coatings on A 516 low carbon steel, which is considered a prospective material for manufacturing used nuclear fuel containers. The 3 mm-thick Cu coatings were formed using the high pressure cold spray method with N2 as the propellant gas. To increase the adhesion strength of the deposited coatings a copper sublayer was formed first, using He as the propellant gas. The deformation of copper particles during the deposition process was studied. The obtained SEM images of the Cu layer-A 516 low carbon steel substrate cross-sections demonstrated that the Cu sublayer had a dense microstructure, and local jet-metallic mixing areas. The Cu particles were deformed considerably more severely in the sub-layer than in the following layers. The steel substrate underwent severe deformation due to the impact of Cu particles. The mutual severe deformation of Cu particles and steel substrate resulted in a considerable increase of adhesion strength up to 120MPa. The structure of coatings and coating-substrate interface was studied by OIM, SEM and EDS.
Study on Cu-Ag-Zn Abradable Seal Coatings by Cold Spraying
Authors: Shen Yanfang , Cui Xinyu , Wu Jie , Li Ming , Xiong Tianying
Published: August 2022

This paper presents a study on Cu-Ag-Zn abradable seal coatings prepared by cold spraying. The micro-morphologies of the coatings were analyzed using scanning electron microscopy and electron dispersion scanning. The hardness of the coatings was analyzed. Thermal shock tests were conducted to evaluate the combination strength between the coating and the substrate. The friction and wear properties of the coatings were also tested. Two methods, annealing the coatings in vacuum and heating the feed powders in cold spraying, were tried to improve the combination strength and quality of the coating. The results showed that Cu-Ag-Zn coatings made by cold spraying with powder heating exhibited better combination strength and anti-friction properties compared to coatings annealed in vacuum and the original samples. The paper also proposed a combination mechanism for the Cu-Ag-Zn coatings.
Surface Preparation for Ceramics Functionalization by Thermal Spraying
Authors: Scheitz S. , Toma F.-L. , Kuntze T. , Leyens C. , Thiele S.
Published: August 2022

Dense sintered technical ceramics demand special surface preparation in order to be coated by thermal spraying. Sandblasting results in the damage of the interface region and leads to bonding defects. On the contrary, by varying the laser conditions, different laser structured surfaces were generated, which at Rz roughness values in the range of 40 μm, allowed to achieve thick and well bonding coatings. Therefore, laser ablation is proved to be the best method for surface preparation of ceramic substrates. In the case of porous ceramics (including pre-sintered ceramics) substrate preparation can be omitted, depending on their porosity level. Ceramics with porosity content up to 60 % can be coated by APS, whereas HVOF can be used on ceramics with porosity up to 30 %. On ready-to-get-coated pre-sintered ceramic parts (without substrate preparation), followed by co-firing of the substrates and coatings, the development of new ceramic components is possible.
Synthesis of Thermal Spray Grade Silicon Carbide Feedstock Powder for Plasma Spray Deposition
Authors: Mubarok F. , Espallargas N.
Published: August 2022

Novel synthesis of thermal spray grade silicon carbide (SiC) feedstock powder is necessary to allow deposition of this material using atmospheric plasma spraying (APS) method. SiC particles with average size of 1.0 µm are treated using co-precipitation techniques to deliver yttrium aluminum garnet (YAG) binder from its solution precursor as a nano-film onto SiC particles surface. The YAG nano-film will protect SiC core from direct interaction with plasma jet thus hindering their decomposition as well as providing matrix phase within the SiC particles vicinities. The modified SiC particles are sintered and crushed and then sieved to separate 25-45 µm and 45-90 µm size powders, which are then plasma sprayed to deposit SiC coatings of about 300 µm in thickness. Both the feedstock and the coatings were analyzed and compared with regards to their phase composition and microstructures.
The Effect of Fuel Ratio on Activity of Suspension Flame Sprayed Titania Coatings
Authors: Robinson B. , Parkin I.P. , Darr J.A. , Tabecki A. , de Villiers Lovelock H.L. , Jose D. , Mills A.
Published: August 2022

The photocatalytic properties of titania are widely known with applications including solar water disinfection, solar hydrogen production and as anti-bacterial surfaces. Herein, we report the use of suspension flame spraying for the deposition of conformal TiO2 coatings. This process is carried out using aqueous titania suspension (ca. 5 wt%) injected into an acetylene flame (ca. 3100 °C), via an atomiser. Coatings deposited were adherent, majority anatase phase and retained their nanostructure after coating. In this study the acetylene/oxygen ratio was altered to determine the effect on the photoactivity of titania coatings produced, with photoactivity determined by photocurrent generation under illumination. All coatings produced were shown to be photoactive with a marked difference in photocurrent observed between coatings produced in the varying flame conditions. Photocurrent generation increased by up to 3.7 times with decreasing fuel ratio. This difference was attributed to the build-up of reduced titania species in the coating.
The Importance of Optimizing Nozzle Dimensions for Cold Spray Process
Authors: Huang Renzhong , Fukanuma Hirotaka
Published: August 2022

Particle velocity is one of the most crucial parameters to determine coating’s properties in cold spray process, such as coating’s densification and bonding strength. To achieve a high particle velocity, the common way is to increase the working gas temperature or pressure, sometime using the extremely expensive helium gas. In this study, computational fluid dynamics (CFD) method was employed to optimize the nozzle dimension in order to improve particle velocity. Particle velocity was also measured with DPV-2000 to verify the simulation results. Furthermore, coatings were deposited with the optimized nozzle, and their mechanical and electric properties were tested. The results show that the optimized nozzle benefited to improve the adhesive strength with substrate and electric properties of cold-sprayed coatings.
The Importance of Temperature Management in Thermal Spraying and the Respective Advantages of CO2 for Cooling
Authors: Kroemmer Werner
Published: August 2022

Different directions characterize the advances being made in thermal spraying today. On the one hand, spray processes are becoming colder, on the other hand, high-performance systems are being designed which enable a higher powder throughput, thus making production faster and more efficient. The current spectrum of substrate materials is much broader and even more versatile, as can be seen with new materials which prevent thermal stresses from arising during the production process. More and more applications require the use of special cooling methods to increase the cooling efficiency and, in turn, optimize the process. An ongoing objective of the gas industry is to offer the user hardware which not only exploits all the advantages of CO2, for example, but which is also suited to new applications.
Transplantation of Thermal Sprayed Coatings
Authors: Knödler P. , Otten M. , Möhwald K. , Maier H.J. , Freiburg D. , Peuker A. , Biermann D.
Published: August 2022

Be it to save the environment or to save money, engineers everywhere attempt to use materials which can’t normally withstand the surface stress they will be exposed to on their own. This is one of the reasons for the constant interest in new and innovative coating technologies. One such innovation is the transplantation of thermal sprayed coatings. In the transplantation process the coating is integrated into a high-pressure die casting process. In contrast to the conventional process chain, the coating is not directly applied to the work piece, but to a mold insert. During the pressure casting the melt infiltrates the coating and thus creates a join. This way the coating is indirectly applied to the die-cast work piece after removal from the mold. Additionally, depending on the materials involved, a material bonding connection similar to brazing is possible and results in an increased adhesion of the coating. A potentially very interesting trait of the transplantation process is, turning an internal coating process into an external coating process. This allows the coating of inside diameters well below the usual limit of an internal spray gun. Due to the high geometric accuracy of the process this can be potentially done without any need for additional finishing steps.
Tribological Properties of Hard Metal Coatings Sprayed by High Velocity Air Fuel Process
Authors: Lyphout C. , Sato K. , Houdkova S. , Smazalova E. , Lusvarghi L. , Bolelli G. , Sassatelli P.
Published: August 2022

Lowering the thermal energy and increasing the kinetic energy of sprayed particles by newly developed HVAF systems can significantly reduce material decarburization, and increases sliding wear and corrosion resistance of hard metal coatings, making HVAF coatings attractive both economically and environmentally over its HVOFs predecessors. Two agglomerated and sintered feedstock powder chemistries, respectively WC-Co (88/12) and WC-CoCr (86/10/4), with increasing primary carbides grain size from 0.2 to 4.0 microns, have been deposited by the latest HVAF-M3 process onto carbon steel substrates. Respective dry sliding wear behaviours and friction coefficients were evaluated at room temperature via Ball-on-disk (ASTM G99-90) wear tests against Al2O3 counterparts, and via Pin-on-disk (ASTM G77-05) wear tests against modified martensitic steel counterparts in both dry and lubricated conditions. Sliding wear mechanisms, with formation of wavy surface morphology and brittle cracking, are discussed regarding the distribution and size of primary carbides. Corrosion behaviours were evaluated via standard Neutral Salt Spray (NSS), Acetic Acid Salt Spray (AASS), accelerated corrosion test and electrochemical polarization test at room temperature. Optimization of coating tribological properties are discussed regarding the suitable selection of primary carbide size for different working load applications.
A Feasibility Study on Hybrid Use of Thermal Spray Coating and Ultrasonic Nanocrystalline Surface Modification
Authors: Amanov Auezhan , Kim Jun-Hyong , Pyun Young-Sik , Tripathi Khagendra , Lee Soo-Wohn , Lee Hae-Ryong , Kim Taehyung
Published: August 2022

An ultrasonic nanocrystal surface modification (UNSM) technique was applied to the thermally sprayed yttria-stabilized zirconia (YSZ) ceramic thermal barrier coating (TBC) deposited onto a hot tool steel substrate to improve the mechanical and tribological properties. The surface microstructure of the as-sprayed and UNSM-treated coatings was examined using a scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and Raman spectroscopy, while the hardness of the coatings was measured by Vicker`s hardness tester. The friction and wear behavior of the coatings was assessed using a ball-on-disk tribometer against bearing steel (SAE52100) ball at temperatures of 25 °C and 200 °C under dry reciprocating conditions. Results showed that the UNSM-treated coating had smoother surface, lower friction and higher resistance to wear compared to that of the as-sprayed coating. It was found that hybrid use of thermal spray coating (TSC) and UNSM technique is meaningful to bring together synergy effect of two emerging surface technologies.
Columnar Structured YSZ Coating Formation by PS-PVD Using Conventional Plasma Spray System Assisted Through Droplet Filtering
Authors: Chen Qing-Yu , Li Cheng-Xin , Li Chang-Jiu , Luo Xiao-Tao , Yang Guan-Jun
Published: August 2022

It is only performed light of sight deposition in atmospheric plasma spray (APS) and electron beam physical vapor deposition (EB-PVD). The PS-PVD processing is realized no light of sight deposition which bridge the gap between APS and EB-PVD. In this study, shielding deposition process was used to produce YSZ coatings and the microstructure and deposition behavior were also researched. A shrouded plasma torch was used to proceed on PS-PVD working. Multiple samples were placed on the same straight line to realize multistage shielding. The surface morphology and cross section morphology of coatings were observed by SEM. It is found that the surface is shown an island structure and the nano particles consist of island are grown smaller with the increased shielding stage. The cross section morphology of fracture coatings is shown columnar structure. This confirmed that the YSZ coatings are deposited via vapor phase at the condition of shielding. The deposition behavior of multi-stage shielding is also researched.
Composition Effects of La2Ce2O7 Thermal Barrier Coatings against Calcium-Magnesium-Aluminum-Silicate (CMAS) at 1250°C
Authors: Wang Li-Shuang , Li Guang-Rong , Li Cheng-Xin , Liu Tao , Yang Guan-Jun , Li Chang-Jiu
Published: August 2022

The evaporation of both CeO2 and La2O3 in high temperature plasma arc leads to deviation of plasma sprayed La2Ce2O7 coating composition from the starting powder particle. Such change results in significantly inhomogeneity of compositions within a coating which influences the performance of calcium-magnesium-alumina-silicate (CMAS) corrosion. In this study, the pellets with different Ce / La ratio were interacted with molten CMAS glass. The penetration of molten CMAS on different pellets was characterized by scanning electron microscopy and energy dispersive spectrum (EDS) and the phase of different powder mixtures treated at 1250 °C was characterized by X-ray diffraction ( XRD ). The effects of pellets with different Ce / La ratio on the CMAS corrosion after thermal exposure at 1250 °C for 50 h were investigated. The result demonstrated that pellets with ratio of Ce / La greater than or equal to 1.0 were completely dissolved into the molten CMAS, at the same time the others were also damaged, forming diffusion layer and reacted layer, respectively. The difference of the ratio of Ce / La indeed affected their performance against CMAS attack.
High Thermal Conductivity Plasma Sprayed AlN Coating
Authors: Shahien Mohammed , Yamada Motohiro , Fukumoto Masahiro , Egota Kazumi , Okamoto Kenji
Published: August 2022

Aluminum nitride (AlN) ceramics is characterized with its high thermal conductivity and chemical stability. However, it was impossible to fabricate AlN coatings by conventional thermal spray processes directly from AlN feedstock powder due to thermal decomposition of AlN during spraying. In the last decade we were apple to fabricate the AlN coatings through the reactive plasma spraying process (RPS) in the atmospheric ambient. This study describes the way to fabricate high thermal conductivity plasma sprayed AlN coatings. The thermal conductivity of the AlN coatings was investigated by laser flash method. The as sprayed coating had very low thermal conductivity (2.43 W/m.K), compared to the AlN value. It is attributed to presences of high oxide content (Al5O6N, γ-Al2O3 and α-Al2O3 phases), low density (2.32 g/cm3) and high porosity in the plasma sprayed coating (about 22%). Besides that, although the N2 gas flow improved the nitride content, the thermal conductivity decreased gradually. It is related to the further increase of the coating porosity and decreasing its density with the N2 gas. The influence of the process parameters on the thermal conductivity was investigated and to fabricate high thermal conductivity AlN coating adjusting the oxide content, the coating porosity and microstructure are the main factors. Very high thermal conductivity (about 95 W/m.K) atmospheric plasma sprayed AlN coating was fabricated. The coating consists of mainly AlN phase (more than 95% AlN), very small amount of oxide phases, low porosity (about 3%) with a sintered microstructure (nicked-shape sintered particles).
Influence of Elemental Evaporation on the Composition of La2Ce2O7 Splats Deposited by Plasma Spraying
Authors: Wang Li-Shuang , Liu Tao , Li Guang-Rong , Yang Guan-Jun , Li Chang-Jiu , Li Cheng-Xin
Published: August 2022

La2Ce2O7 (LCO) is one of the promising candidates of high temperature thermal barrier coating materials. However, during plasma spraying, the evaporation of both CeO2 and La2O3 in high temperature plasma jet leads to deviation of coating composition from the starting powder particle. Such change results in significant inhomogeneity of compositions within a coating which influences the performance of resultant coating. In this study, an agglomerated La2Ce2O7 powder with Ce / La ratio of 1.5 and in a size range of 5-60 μm was used to deposit the splats and coatings under different plasma spray conditions. The compositions of La2Ce2O7 splats in different sizes were characterized by scanning electron microscopy and energy dispersive spectrum (EDS), and splat dimensions were characterized by 3D laser microscopy. The relationship between droplet size and splat composition was examined. Results showed that the Ce / La ratio in splats changes significantly with the splats diameter in a range from 1.5 to 0.7. There is a big difference in the composition of APS coatings deposited by coarse and fine powders. The mechanism causing splat composition change was examined based on the selective elemental loss during plasma heating of LCO particles in APS, aiming to control LCO coating composition.
Microstructure and Properties of Equiaxed 316L Stainless Steel Coating Deposited by LPPS
Authors: Yang Deming , Gao Yang , Sun Chengqi
Published: August 2022

The equiaxed microstructure of 316L stainless steel coating was successfully deposited by low pressure plasma spraying (LPPS), which was different from the lamellar microstructure prepared by other thermal spraying technologies. In this article, the effect of substrate temperature during deposition process and post annealing treatment on the lamellar – equiaxed microstructural transition were investigated. The results indicated that the homogeneous equiaxed grains without lamellar boundaries coatings were observed when the deposition temperature was about 900 °C. Completely lamellar microstructural coatings were deposited at the substrate temperature of about 300 °C, and the lamellar microstructure can transform to equiaxed microstructure after annealing treatment. The hardness of equiaxed coating was lower than lamellar coating.
Numerical Study of the Arc Fluctuations in DC Plasma Torch
Authors: Ardakani Esmaeil Safaei , Mostaghimi Javad
Published: August 2022

Plasma spray technology is widely employed by industry to apply coatings on different components to protect them from corrosion, wear and high temperature environments. The gases introduced into the DC plasma torch are heated by the arc and a plasma jet exits the torch. Powders are injected into the plasma jet where they are then accelerated, heated, and melted before impacting the substrate, which is placed at some distance from the outlet of plasma spray torch. Plasma arc exhibits strong voltage fluctuations which correspond to the movement of the anode arc root attachment. Understanding the arc movement within the torch and how it affects the flow and temperature fields of the plasma jet exiting the torch is of great importance. Understanding the flow, temperature and electromagnetic fields within the DC plasma torch is extremely challenging and there is a limited number of investigations in the literature. In order to provide unique sets of surface characteristics, e.g., thermal barriers, wear and corrosion resistance, a high quality coating with appropriate combination of powder and base materials must be produced. To produce a high quality coating, powder particles should be uniformly heated and accelerated, and then deposited onto the substrate. In this paper, an unsteady 3-dimensional model of the arc movement within the plasma torch is reported. The proposed model is employed to solve electric potential and magnetic vector potential equations in addition to continuity, momentum and energy equations. The k-ε turbulence model was used to model the turbulence of the flow field inside a non-transferred DC argon plasma torch. The geometry of the torch was that of SG-100 torch (Praxair). TO study the effect of the arc length on the voltage, first a steady-state model was considered for a range of arc lengths and arc-root radii. The results of this model provided the relation between arc length and arc voltage for a set of arc root radii and given argon flow rate. Then, given voltage fluctuation profile, the unsteady, arc root attachment movement was simulated from the estimation which found from steady models. Results show that the effects of velocity and temperature fluctuations at the outlet of the torch (where the particles are injected) are not negligible and such fluctuations exceed 15% of their average values. These will in turn affect the particle heating history and will negatively impact the microstructure of the coating.
Residual Stresses Analysis of Cold Sprayed Coatings by Numerical Simulation
Authors: Li Wenya , Yang Kang , Zhang Dongdong
Published: August 2022

In this paper, a preliminary analysis on the residual stress evolution of cold-sprayed coatings taking copper coating as an example was performed. An integrated frame of calculation was proposed based on the simulation results obtained from the developed thermo-mechanically coupled Eulerian model. In a single Cu splat, the residual stress appears to be large tensile stress near the surrounding area of the interface and be small tensile stress at the bottom. In single pass Cu coating, the residual stress is variable and there exists not only compressive stress but also tensile stress. When the impacting velocity changes, the resultant residual stresses also vary in both cases. The present simulated results were related to the reported experiments by others, while there is much difference.
Scuffing Resistance of HVOF Sprayed Nanostructured Carbide Coatings
Authors: Żórawski Wojciech , Makrenek Merard
Published: August 2022

This paper discusses results of research concerning the microstructure and scuffing resistance of HVOF sprayed WC- 12Co nanostructured and conventional coatings under dry friction conditions. The observations were carried out by means of a Falex type tester. It was found that HVOF sprayed nanostructured WC-12Co coatings showed the most homogeneous structure, the greatest scuffing resistance and the highest hardness.
Shot Peening Effect on the Morphology and Roughness of HVOF Coatings
Authors: Sucharski Gustavo Bavaresco , Paredes Ramón Sigifredo Cortés , Pukasiewicz Anderson Geraldo Marenda , Vaz Rodolpho Fernando
Published: August 2022

The HVOF process is characterized by the deposition of a low porosity and oxide content coating and the particles projected by this process have high kinetic energy, resulting in a high density coating. However, the presence of non-melted particles can affect the porosity, tensile adhesion, hardness and surface finishing. In this article, the influence of the shot peening treatment on morphology, porosity, tensile adhesion and roughness of some FeMnCrSi(Ni/B) HVOF coatings have been studied. High carbon steel particles with spherical geometry were used for shot peening. The results show that the shot peening reduces the porosity, mainly in the coatings with higher porosity level, and generates an increase of hardness with no phase transformations. The increase in adherence is also a benefit generated by the treatment. The surface quality analyses show a significant roughness reduction. With shot peening a compressive residual stress state was achieved in the coating, improving mechanical properties.
Solution Precursor Plasma Spraying of Bismuth Titanate by Means of Inductively-Coupled Thermal Plasma
Authors: Le Roux B. , Veilleux J.
Published: August 2022

Lead-free piezoelectric materials are nowadays drawing considerable attention as lead titanium zirconium oxide (PZT) is considered “as a substance of very high concern” by the European Chemicals Agency because of its toxicity. An interesting PZT replacement material for high temperature capable ultrasonic transducers is bismuth titanate (Bi4Ti3O12), which could be used for pipe thickness and corrosion monitoring in the oil & gas and nuclear industries. In this study, solution precursor plasma spraying (SPPS) is used to deposit Bi4Ti3O12 coatings onto stainless steel substrates by means of inductively-coupled thermal plasma. The crystal structure and the morphology of the deposited coatings is studied as a function of the SPPS operating parameters such as plasma gases, electrical power, chamber pressure and spraying distance. SPPS of piezoelectric materials is an interesting one step process alternative to the time consuming layered-based chemical spray pyrolysis/calcination of sol-gel precursors.
TGO Formation and Failure Mode of TBC Systems Comprising PVD-Al Interlayers
Authors: Ali I. , Grund T. , Lampke T. , Wett D. , Nestler D. , Wagner G.
Published: August 2022

The physical characteristics and volume growth of TGOs in TBC systems lead to TBC failure. It is proved that enriching the BC/TC interface with α-Al2O3 is beneficial to an extended operational time by prolonging the steady-state growth stage of the TGO. The corresponding phase reactions in TBC systems with heightened Al activity, however, are not studied yet. In this work, the stage formation of TGO layers of TBC systems with PVD-Al interlayers is described. The study uses thermal cyclic loading with dwell time at maximum high temperature of 1,150 °C. The crack formation in the ceramic top coat and the TGOs thickness at the interface are investigated by SEM/EDS after 1, 6, 12, 24, 40 and 80 thermal cycles. The results plot the interface change and crack formation as a function of the thermal cycle number. The corresponding failure mode is discussed.
Breaking Behavior of Oxide Scale on the LPPS Bond Coat Surface during Pretreatment in Vacuum
Authors: Zhang Bang-Yan , Yang Guan-Jun , Li Cheng-Xin , Li Chang-Jiu
Published: August 2022

Pre-diffusion treatment (high temperature vacuum treatment) plays an important role in the growth of the thermally grown oxide (TGO) on the low pressure plasma spray (LPPS) bond coat surface. Results show that the initial thin oxide scale, formed during deposition process, on the as-sprayed bond coating surface has broken and shrunk to discontinuous oxide particles through the elements diffusion during the pre-diffusion. Two kinds of pre-diffused bond coats deposited in different oxygen partial pressure atmosphere show different results of the average distance between the individual oxide particles on the pre-diffused bond coating surface. In this study, a three dimensional model with thermal grooving theory was developed to explore the essential condition for the scale breaking and explain the differences of these results. This research can provide reference for the preparation optimization and pre-treatment optimization of bond coat towards high performance TBCs.
Characterisation and In Vitro Corrosion Resistance of Plasma-Sprayed Hydroxyapatite and Hydroxyapatite–Silicon Oxide Coatings on 316L SS
Authors: Singh Gurpreet , Singh Hazoor , Sidhu Buta Singh
Published: August 2022

In the current investigation plasma spray technique was used for depositing hydroxyapatite (HA) and hydroxyapatite – silicon oxide (SiO2) coatings on 316L SS substrate. In HA-SiO2 coating, 20 wt% SiO2 was mixed with HA. The feedstock and coatings were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) / energy-dispersive X-ray spectroscopy (EDX) analyses. The corrosion resistance of the uncoated, HA coated and HA + 20 wt% SiO2 coated 316L SS was investigated by electrochemical corrosion testing in simulated human body fluid (Ringer’s solution). After the corrosion testing, the samples were analyzed by XRD and SEM / EDX analyses. The addition of SiO2 reduces the crystallinity of the coating. The corrosion resistance of the 316L SS was found to increase after the deposition of the HA + 20 wt% SiO2 and HA coatings.
Coaxial Introductions of Resin Rods with Ceramics Nanoparticles into Gas Flame Spraying
Authors: Takai Kazuto , Kirihara Soshu
Published: August 2022

Solid resin rods including ceramics nanoparticles were fed successfully into a Rokide flame gun to create dense coated layers without micro cracks and pores applying for electric, magnetic and dielectric components. In this investigation, alumina particles of 170 nm in average diameter were dispersed into acrylic liquid resin at 40 % in volume fraction. The paste material was injected into an brass mold of φ4 ~ 200 mm in inner dimension and thermally cured through heating at 120 °C for 60 min. Formed solid rods were fed coaxially into an oxyacetylene gas flame by using the Rokide spraying system. Sprayed particles were collected in a water bath for microstructure observations by a scanning electron microscope and crystal phase analyses by an X-ray diffraction spectroscopy. Fine ceramics layer formations will be discussed systematically by the feeding speed of solid rods and gas flame condition of air pressure and oxygen pressure.
Comparative Study of the Erosive Wear of Thermally Sprayed Coatings Using Powder and Flexi-Cord Feedstock Materials
Authors: Lima C.R.C. , Libardi R. , Mojena M.A.R. , Fals H.C. , Leal C.V. , Camargo F.
Published: August 2022

Sprayed deposits using conventional wire and powder materials open a wide range of possibilities to solve wear problems in engineering equipment. The option for new different spray technologies and consumables like nanostructured powder materials and nanocomposite cored wires has expanded the engineering possibilities. Cored wire technology allows the use of compositions that cannot be drawn into wire form like carbides in metallic matrix and high-temperature materials, thus intensifying the use of low operating cost welding and spraying processes to demanding wear applications. The objective of this work was to compare the mechanical characteristics and erosive wear performance of coatings obtained by Flame Spray and High Velocity Oxygen Fuel Spray using some selected powder and flexi-cord wire materials. The wear resistance of the coatings was determinate by slurry erosion wear test.