bluuebunny/crossref_metadata_2025_split huggingface dataset:
Flame Spraying of Titania and Magnetite
Authors: Morton S.S. , Hirschfeld D.A. , Hall A.C. 
Published: September 2022

Abstract
The effect of process conditions on flame spraying of titania (TiO2) and magnetite (Fe3O4) was investigated. Designed experiments were conducted to determine spraying conditions, specifically total combustible gas flow, stand off distance, and oxygen/acetylene ratio that produce high deposition efficiency (DE) and dense coatings. Along with DE, particle temperature and velocity were determined and correlated with process conditions. Results indicate that for both titania and magnetite, hot and high velocity molten particles result in higher DE and lower porosity coatings. Micrographs of coating cross-sections and surfaces were taken with both field emission scanning electron microscope (FESEM) and optical microscope. X-ray diffraction analysis shows that the titania coating retained its rutile structure while the magnetite coating had small amounts of magnetite (γ-Fe2O3) in addition to magnetite.
Cyclic Oxidation Behaviour of Plasma Sprayed Stellite-6 Coated Ni-Base Superalloys
Authors: Singh H. , Puri D. , Prakash S. 
Published: September 2022

Abstract
Stellite-6 coatings were deposited on two Ni-base superalloys namely Superni 75 and Superni 600 by shrouded plasma spray process and the oxidation behaviour of these coatings has been investigated in air and in aggressive environment of Na2SO4 - 60%V2O5. Accelerated oxidation tests were conducted in a silicon carbide tube furnace under cyclic conditions at an elevated temperature of 900°C for 50 cycles. Each cycle consisted of one hour heating and 20 minutes cooling in air. Thermogravimetric technique was used to approximate the oxidation kinetics. The corrosion scales were characterized by XRD, SEM/EDAX and EPMA analyses. It has been observed that coatings followed the parabolic rate law of oxidation, although minor deviations were observed. Overall weight gain conceived in air was just 51% of that in the aggressive environment in case of coated Superni 75, whereas in case of coated Superni 600, the cumulative weight gain in air was found to be one-third of that in the Na2SO4 -60% V2O5 atmospheres. Further the coating showed very good adherence to both of the substrates during the course of air oxidation, whereas some cracks were observed near the edges of the specimens during the molten salt induced oxidation. XRD analysis revealed the presence of phase like CoO, CoCr2O4 and Cr2O3 in the oxide scales, which are reported to be protective oxides. The XRD results were further supported by SEM/EDAX and EPMA.
Effect of WC Addition in Ni-Cr Matrix on Performance as Coatings for Corrosion/Erosion Protection of Heat Exchanger Materials
Authors: Kumari S. , Khanna A.S. 
Published: September 2022

Abstract
Fireside corrosion and erosion of heat exchanger tubes is a serious problem. One of the methods to combat this is by applying corrosion and erosion resistant coatings. Nickel– chromium alloys have already been used as coatings to deal with oxidation environments at high temperature. The wear resistance of these coatings can be improved by adding different hard precipitates such as carbides of refractory metals and cemented carbides. In the present study, various compositions comprising of Ni-Cr with 15, 35, 60 and 100% wt% WC/Co were made using thermal spray grade powders. These were then coated on steel substrate by the HVOF method. After detailed characterization of the coatings, the performance of the coatings at high temperature was studied by exposing the coated samples in the temperature range of 600-700°C. Ni-alloy coatings with moderately (15%) added WC/Co showed better oxidation resistance than coatings with high percentage of WC/Co and also than the pure Ni-alloy coating in high temperature range of 600-800°C. From the characterization, it was found that Ni-Cr alloy with 15% WC/Co gave the optimum results.
Manufacturing of Corrosion Resistant Coatings Using Laser Assisted Thermal Spraying
Authors: Suutala J. , Tuominen J. , Vuoristo P. 
Published: September 2022

Abstract
In the present study, surface engineering related to simultaneously thermally sprayed and laser melted corrosion resistant coatings has been carried out. A 6 kW high power diode laser or a Nd:YAG laser and a flame spray gun were used to construct the laser assisted thermal spraying system. The main aims of the study were to find out the optimal processing parameters and materials to create dense corrosion resistant coatings on steels. The corrosion resistance of the manufactured coatings was measured and the microstructure characterized using optical and scanning electron microscopy.
Corrosion Behaviour of Ni-5Al/WC-12Co HVOF Coating Systems
Authors: Lekatou A. , Gavrilakis N. , Grimanelis D. 
Published: September 2022

Abstract
WC-12Co coatings (with and without Ni-5Al bond coats) as well as Ni-5Al coatings were deposited on Al 7075 by HVOF spraying. The corrosion behaviour of the coatings was investigated by salt spray testing for 40 days, followed by potentiodynamic tests in a 3.5% aqueous NaCl solution, at 25, 35 and 45°C.The thicker duplex coatings (500µm) were not susceptible to pit corrosion, at any temperature. A small fraction of the thinner duplex coatings (260µm) underwent localized corrosion, only at 45°C. Ni-5Al and a small fraction of WC-12Co single coatings showed low susceptibility to pit corrosion which increased with temperature increasing and thickness decreasing. The coating system Ni-5Al/WC-12Co exhibited the highest resistance to general corrosion, which was independent of the thickness at the two thicknesses tested.
Hot Corrosion Behaviour of HVOF Sprayed Coatings on ASTM SA213-T11 Steel
Authors: Sidhu H.S. , Sidhu B.S. , Prakash S. 
Published: September 2022

Abstract
Cr3C2-NiCr, NiCr, WC-Co and Stellite-6 alloy coatings were sprayed on ASTM SA213-T11 steel using the HVOF process. Liquid petroleum gas (LPG) was used as the fuel gas. Hot corrosion studies were conducted on the uncoated as well as HVOF sprayed specimens after exposure to molten salt at 9000C under cyclic conditions. The thermo-gravimetric technique was used to establish the kinetics of corrosion. XRD, SEM/EDAX and EPMA techniques were used to analyse the corrosion products. All these overlay coatings showed a better resistance to hot corrosion as compared to that of uncoated steel. NiCr Coating was found to be most protective followed by the Cr3C2-NiCr coating. WC-Co coating was least effective to protect the substrate steel. It is concluded that the formation of Cr2O3, NiO, NiCr2O4, and CoO in the coatings may contribute to the development of a better hot corrosion resistance. The uncoated steel suffered corrosion in the form of intense spalling and peeling of the scale, which may be due to the formation of unprotective Fe2O3 oxide scale.
Cracking and Spalling Behavior of WC-17% Co Cermet Coatings
Authors: Legoux J.-G. , Bouaricha S. , Sauer J.P. 
Published: September 2022

Abstract
Thermal spray WC based powders are now frequently used as chrome replacement alternatives for a wide range of industrial and aeronautical applications. In numerous cases, the carbide materials outperform the hard chrome in many property evaluations. However, their usage on highly stressed parts, especially in fatigue loading, can be limited by spalling resistance of the coating. While HVOF is being used on many flight critical parts, stringent applications like the landing gear components of carrier-based aircraft are still under investigation. This work, on WC-17%Co, relates coating bend test performance and fatigue/cyclic step loading behavior to the processing history using different HVOF systems. Initially, twelve (12) different coatings were monitored using a DPV- 2000 for temperature/velocity profiles. The mechanical properties were then assessed using an instrumented four-point bend test as well as uniaxial cyclic loading. After mechanical testing, the coating microstructures were characterized using X-Ray diffraction and electron microscopy in order to investigate the phase content and nature. In particular, the cracks generated during the bend test were measured using SEM on sample cross sections to understand characteristics such as spacing and crack penetration to the substrate. The interactions of processing parameters with the cracking/spalling resistance of the various coating deposits will be discussed and a potential criteria for the control of cracking phenomena will be presented.
Fatigue Fracture Mechanism of HVAF Sprayed Low Alloy Steel
Authors: Liu M. , Deng C. , Zhou K. , Song J. , Wu C. 
Published: September 2022

Abstract
The influence of the high velocity air fuel (HVAF) sprayed coating on the fatigue behavior of the low alloy steel was studied at different stress levels. It was observed that only one single main crack initiator existed in the substrate after fatigue at low stress levels, but there were multi-cracks on the substrate surface at high stress level. Detailed investigations showed that the cracks in the HVAF coatings sinuously extended to the interface and deflected thereat along the interface. Consequently, free-standing coating was formed due to its limited bond strength to the substrate and the lower elastic modulus than that of the substrate. The gap between the free-standing coating and the substrate surface was found to be correlated with the stress level. The high stress can greatly degrade the adhesion to the substrate causing the delamination of the coating. The cracks in the HVAF coating had no significant effect on the fatigue life of the substrate.
Processing and Properties of Titanium Coating Produced by Warm Spraying
Authors: Wu T. , Kuroda S. , Kawakita J. , Katanoda H. , Reed R. 
Published: September 2022

Abstract
Thermal spraying of dense titanium coatings in the air atmosphere was achieved by using a two-stage high velocity oxy-fuel process (HVOF) called the Warm Spray Process. In the process nitrogen gas is mixed with the combustion gas to lower the gas temperature. Gas dynamics modeling of the flow field of the gas in the spray apparatus as well as the acceleration and heating of titanium powder injected from the powder feed ports were conducted. Based on the obtained temperature history of a titanium powder particle, its oxidation during flight was also predicted by using a Wagner-type oxidation model. These results were compared with measured velocity and temperature of sprayed particles by DPV2000 and the properties of deposited coatings. Significant discrepancy in the temperature of sprayed particles was found between the calculation and measurement whereas the measured velocity was closer to the model calculation. The model prediction of oxygen content was in a good agreement with the analysis of actual coatings. Furthermore, properties of the sprayed coatings such as porosity, oxygen content were correlated with the particle velocities and temperatures. Nitrogen gas was highly effective in lowering the oxygen content, but excessive nitrogen addition caused the coating porosity to increase due to insufficient particle temperatures.
Analysis of Potential Improvements of HVOF Based Processes
Authors: Voronetski A. , Belashchenko V. 
Published: September 2022

Abstract
The paper presents an analysis of possible improvements in HVOF torches and associated processes. It is shown that increasing the efficiency of combustion modules, widening the available range of operating pressures as well as optimizing the powder injection and nozzle expansion lead to significant improvements in comparison with the currently utilized HVOF processes using liquid fuel and radial powder injection. The analysis is confirmed by experimental data obtained using an advanced HVOF torch designed to use ethyl alcohol as a fuel. The new torch operates at a higher thermal efficiency of a combustion module, able to generate products of combustion with better capability to transfer heat to particles and more dissociated molecules. High thermal efficiency also results in a wider operating window and better control of a desirable balance between particles’ kinetic and thermal energy, which depends on the spraying material and a particular coating’s requirements. Shock wave generators inside the nozzle/barrel are also included in the design to allow an improvement in powder injection and an increase in the heat exchange between products of combustion and particles. These advantages have allowed for the minimization of the throat diameter providing throat cross-sectional surface area approximately 2 times less in comparison with other liquid fuel HVOF torches presently used in the industry. The reduction in throat diameter results in significantly less consumption of fuel and oxygen, and also results in an overall decrease of the operating costs. Coating quality, deposition efficiency and deposition rate in this case are the same or better in comparison with other currently utilized liquid fuel HVOF processes.
Coating Properties of HVOF Sprayed Carbide-based Ultrafine Powders
Authors: Matthäus G. , Bobzin K. , Lugscheider E. , Zwick J. 
Published: September 2022

Abstract
HVOF spraying of carbides is a well established method to produce high performance wear and corrosion protection coatings for various industrial applications. Using ultrafine feedstock powders with particle sizes well below 25 µm can offer many advantages with respect to the resulting coating properties, such as improved coating density and homogeneity and high dimensional accuracy. In this study, fine powder grades of WC 10Co 4Cr, WC 17Co and Cr3C2 25(Ni 20Cr) in a particle size range of –15 +5 µm, -10 +3 µm and –5 µm have been sprayed with suitable HVOF systems on outer surfaces as well as on internal diameters. Resulting coatings have been analysed with respect to coating structure and microhardness. The coatings featured a favourable microstructure and very good hardness values. Furthermore, the Cr3C2 25(Ni 20Cr) material was applied as wear protection coating on piston rings. The coating performance was evaluated in engine tests and proved to be significantly better than a conventionally graded standard material system for this application.
The Effects of Ceria Addition to HVOF Thermal Sprayed NiAl Intermetallic Coatings
Authors: Wang Y. , Liu G. , Tian W. 
Published: September 2022

Abstract
In this paper, the effects of ceria addition to HVOF thermal sprayed NiAl intermetallic coatings were investigated through micro-indentation, thermal shock testing, and microstructural analysis techniques including SEM with EDX, and XRD analysis. It has been found that the addition of ceria to NiAl coatings reduces the tendency of brittle peeling during thermal spraying. This reduction in peeling is presumably due to the improved wetting of the substrate by the molten coating material, which ultimately leads to better coating adhesion. The addition of ceria also resulted in higher coating hardness and elastic modulus as determined by micro-indentation. The coatings containing ceria also exhibited significant increases in thermal shock resistance when compared with that of the pure NiAl coatings. The possible mechanisms responsible for the improvement of the above mentioned properties upon the addition of ceria are also addressed in this paper.
HVAF Sprayed Composite Coating with Ni-base Self-Fluxing Alloy and WC on a Copper Substrate
Authors: Wu C.Q. , Zhou K.S. , Deng C.G. , Deng C.M. 
Published: September 2022

Abstract
In order to improve the wear resistance and service life of the copper, the composite coating consisting of a Ni-base self-fluxing alloy (NiCrWB+50%Al2O3) and WC (WC-12%Co) alloy were sprayed on a copper substrate using High Velocity Air Fuel(HVAF). The coating could meet the operating requirements including high hardness, good wear resistance and low cost. The Ni-base composite coating was analyzed by means of optical microscopy, scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and X-ray diffraction (XRD). The results indicated that the structure of coating was composed of melted particles and partly unmelted round particles of Ni-base alloy, and WC particle. Only a small proportion of the Al2O3 particles were retained in the coating. The phases in the coating consisted of γ-Ni, WC and a little Ni3B. Amorphous structures appeared and some Al2O3 phase existed. The adhesion strength between coating and copper substrate was more than 50MPa. Wear results showed that the Ni-base composite coating exhibited better wear resistance than the coating with no WC particles.
Study of Dynamic Diffusion Bonding of 90MnCrV8 High Strength Steel Coated with WC-Co Obtained by HVOF Thermal Spray
Authors: Gómez de Salazar J.M. , Barrena M.I. , Matesanz L. , Guilemany J.M. , Dosta S. , Miguel J.R. 
Published: September 2022

Abstract
The results for joints obtained by dynamic diffusion bonding of a 90MnCrV8 high strength steel coated with WC-Co are shown in the present work. This high strength steel substrate was coated with WC-Co, sprayed by HVOF technique (Diamond Jet Hybrid DJH-2700) using propylene as fuel gas at different conditions. The dynamic diffusion bonding was carried out in a high frequency furnace, all joints were made in air. Before doing the joints, the steel was coated with Ni and Cu by electrochemical processes in order to obtain a soft 20 m interlayer of Ni30Cu alloy. Microstructure and reacted zones in the joints were investigated by means of Scanning Electron Microscopy (SEM) and Dispersive X Ray Spectrometry (EDX). In all joints different reacted zones can be distinguished, caused by diffusion processes which take place during the joint tests. The mechanical properties of the joints were quantified in a tensile machine, using a constant load of 0.1 MPa·s-1. All joints broke by the WC-Co coating zone by delamination processes. The fracture surface was studied by SEM-EDX in order to know the fracture mechanism of the joints. The maximum tensile strength obtained confirm a very promising technology for industrial applications.
A New High Velocity Oxy-Fuel Process for Making Finely Structured and Highly Bonded Alloy Layers from Liquid Precursors
Authors: Ma X.Q. , Roth J. , Gandy D.W. , Frederick G.J. 
Published: September 2022

Abstract
High velocity oxygen-fuel (HVOF) thermal spray processes are used in applications requiring the highest density and adhesion strength, which is not achievable in most other thermal spray processes. Like other thermal spray processes, however, a normal HVOF process is not able to apply fine powders less than 10 µm via a conventional powder feeder. The advantages of using smaller and even nano-sized particles in a HVOF process include uniform coating, less defective microstructure, higher cohesion and adhesion, full density, lower internal stress and higher deposition efficiency. A new process has been developed to realize HVOF forming of fine-grained alloy layers by using liquid precursors containing fine metallic particles. Process investigations have shown the benefits for making single and duplex layered coatings with full density and high bond strength attributing to the very high kinetic energy of particles striking on the substrate surface and the better melting of the small particles. One of the targeted applications is for the water walls of a fossil-fired boiler that operate in a high temperature and corrosive environment. The new coating system is based on material selection, structure design, process innovation and diagnostics, microstructure, and property evaluation. It is promising to provide better protection of the boilers against various types of degradations like corrosion, oxidation, erosion and interfacial failure.
Suspension Plasma Spraying of Nanostructured WC-12 Co Coatings
Authors: Oberste Berghaus J. , Marple B. , Moreau C. 
Published: September 2022

Abstract
Nanostructured WC-12%Co coatings were deposited by suspension plasma spraying of submicron feedstock powders, using an internal injection plasma torch. The liquid carrier employed in this approach allows for controlled injection of much finer particles than in conventional thermal spraying, leading to thin coatings with a fine surface finish. A PEI (polyethylene-imine) dispersant was used to stabilize the colloidal suspension in an ethanol carrier. In-flight particle states were measured for a number of operating conditions of varying plasma gas flow rates, feed rates and standoff distances, and related to the resulting microstructure, phase composition (EDS, SEM, XRD) and Vickers hardness. High in-flight particle velocities, in excess of 800 m/sec, were generated, leading to dense coatings. It was observed that the coating quality was generally compromised by the high temperature and reactivity of the small particles. To compensate for this shortcoming, the suspension feed rate was adjusted, thereby varying the thermal load on the plasma. Results showed that a slightly larger agglomerate size, in conjunction with low particle jet temperatures, could somewhat limit the decomposition of WC into brittle W2C/W3C and amorphous cobalt containing binder phases.
Microstructure and Electronic Emission of Plasma Sprayed TiO2 Functional Coating with Gradient of Crystal Grain Size
Authors: Tomaszek R. , Pawlowski L. , Gengembre L. , Laureyns J. , Znamirowski Z. , Zdanowski J. 
Published: September 2022

Abstract
The paper aims at the development of coating having a gradient of crystal grain size. Thick, inner layer was plasma sprayed using coarse TiO2 powder. This layer has the thickness ranging from 30 to 50 µm. Thin, outer layer of thickness smaller than 10 µm, was plasma sprayed using different aqueous suspensions of fine powders of TiO2. The morphology of coarse and fine powders was characterized using scanning electron microscope (SEM) X-ray diffraction (XRD). Electronic emission was tested using home made setup. X-ray diffraction enabled to find out an interesting result which is formation of a mixture of rutile and anatase in suspension sprayed coatings. This was also confirmed by Raman spectroscopy investigations. The technology of suspensions plasma spraying was optimized to obtain homogeneous and dense deposits. The sizes were in the range of tenth to one hundred nanometers in initial powders and get clearly smaller in the coatings sprayed using coarse powder but remained quite similar in suspension sprayed films. X-ray photoelectric spectroscopy (XPS) was used to analyze quantitatively TiO2 powders and coatings. Electronic emission was correlated with phase composition of the coating and their grain size.
Atmospheric Plasma Spraying of High-Energy Ball-Milled Al2O3-TiO2 Powders
Authors: Coste S. , Bertrand G. , Coddet C. , Gaffet E. , Hahn H. , Sieger H. , Meunier C. , Vives S. 
Published: September 2022

Abstract
Al2O3-TiO2 materials are very attractive materials for the manufacturing of wear resistant ceramics coatings. Moreover, nanostructured coatings show superior properties (higher hardness and enhanced fracture toughness) as compared to their counterparts containing microscale grains. The aim of this study is to produce nanostructured Al2O3-TiO2 coatings through the plasma spraying technique that can lead to metastable transformations. The starting powders containing 13wt% and 44wt% of titania, have been mechanically activated by high energy ball milling with a planetary mill, (Model P4 by Fritsch, Germany) using steel vials and balls in such conditions to obtained the high pressure TiO2 II phase. The milled powders were then plasma sprayed with an Ar:H2 gas mixture, by varying the plasma parameters (gas flow rates, nozzle diameter, aggregates size). The effect of the milling and the spraying conditions on the crystalline phases and the microhardness of the coatings are evaluated.