bluuebunny/crossref_metadata_2025_split huggingface dataset:
HVOF Reactive Spraying of Mechanically Alloyed Ni-Ti-C Powders
Authors: Horlock A.J. , Sadeghian Z. , McCartney D.G. , Shipway P.H. 
Published: September 2022

Abstract
This work reports research concerning the production of powder, suitable for reactive HVOF spraying, produced by mechanically alloying Ni(Cr), Ti and C elemental powder constituents. Powder mixing was achieved using a high-energy Uni-Ball II Mill and optimisation of the milling parameters are reported. The composition of the powder, at 50wt.%NiCr-40wt.%Ti-10wt.%C, was such that the application of heat has the potential to cause a SHS (Self propagating High Temperature Synthesis) reaction to take place. The utilisation of SHS reactions to produce TiC particles within metallic matrices is well known in bulk systems. However, this work describes carrying out this reaction in individual powder particles on exposure to the high temperature within the HVOF gun. The powder having undergone the SHS reaction during the spray process was deposited onto mild steel substrates to form a dense, coherent coating. The coatings thus formed were shown to contain nanoscale TiC in a Ni(Cr) matrix, indicating a SHS reaction had taken place. This TiC is much finer than that produced in conventional SHS reactions, which is typically ~5ìm. The percentage of TiC formed, and retained in the coating, was lower than expected from the constituent proportions and explanations for this observation are proposed. The microstructure of the coating is described and compared with a Ni(Cr)-TiC cermet coating sprayed using conventional SHS powder generated from reacted compacts which were crushed, sieved and classified to give sprayable feedstock powder.
Development and Implementation of HVOF WC/Co/Cr Coating as Alternative to Electrolytic Hard Chrome Plate in Landing Gear Applications Using Natural Gas as Fuel
Authors: Lee D. , Eybel R. , Evans R. 
Published: September 2022

Abstract
Replacement of Electrolytic Hard Chrome plating (EHC) using High Velocity Oxygen Fuel (HVOF) thermal spray processes to apply dense, wear and corrosion resistant coatings has been identified as a significant goal for the advancement and growth of the thermal spray industry for several years. This paper will provide some details of the development and production implementation of a WC-Co-Cr coating to be used as an alternative to EHC. WC-Co-Cr has been demonstrated in most situations to be superior to the wear performance of EHC with respect to providing functionality in aircraft landing gear hydraulic seal and bearing service. The developed coating is produced via the HVOF process using natural gas as fuel. EHC alternatives using WC-Co-Cr HVOF coatings require significant development prior to implementation into practice. Suitable wear, corrosion and lack of fatigue debit are examples of a few critical properties of coatings for use in landing gear applications. In addition a brief description of the production implementation of a turnkey spray cell for the coating of landing gears will be provided in this paper.
Fatigue and Deformations of HVOF Sprayed WC-Co Coatings vs. Hard Chrome Plating
Authors: Ibrahim A. , Berndt C.C. 
Published: September 2022

Abstract
Environmental problems of hard chrome plating are raising its cost and shrinking availability. HVOF and Detonation spray technologies for application of tungsten carbide and chrome carbide based coatings have proved to be cleaner and more effective than chrome plating. In this paper, the results of fatigue tests for WC-17Co coating deposited onto AISI 4340 steel by HVOF are compared to those for hard chrome plating. The fatigue life distributions as a function of the probability of failure for the coated AISI 4340 steel specimens showed that the HVOF coated specimens exhibited extraordinarily higher fatigue lives compared to the uncoated specimens whereas the hard-chrome-plated imparted fatigue strength degradation to the AISI 4340 steel.
Surface Changes of Several Thermal Spray Coatings Abraded by a TiO2 Slurry
Authors: Stavros A.J. 
Published: September 2022

Abstract
Three-body wear is important in many industrial processes. A laboratory study was performed to follow the response of highly polished thermal spray coating surfaces to degradation by hard titanium dioxide particles. A scanning electron microscope, a white light interferometer and a gloss meter were used to evaluate surface structure and texture of the aspolished and abraded surfaces. Tungsten carbide coatings with differing binder material and applied by different processes all degrade by the same mechanism: softer material is worn away by the hard TiO2 particles until the remaining structure consists of the hardest carbides protruding above the general surface plane. This structure is obtained in spite of significant differences in other surface properties such as roughness (Ra) and gloss number. If a more uniform wear surface is desired the carbide spacing must be reduced so that the coating more effectively presents a carbide surface to the TiO2 particles.
Evaluation of Modern HVOF Systems Concerning the Application of Hot Corrosion Protective Coatings
Authors: Bach Fr.-W. , Engl L. , Bach C. , Lugscheider E. , Parco M. , Duda T. 
Published: September 2022

Abstract
The high velocity oxyfuel flame spraying (HVOF) process appears to be an interesting alternative to low pressure plasma spraying (LPPS) processes for the application of MCrAlY coatings for the use of hot corrosion protection on turbine parts like blades and vanes. Lower investment costs for HVOF facilities compared to LPPS systems combined with adequate coating properties and a stable, easy controllable process can be seen as potential advantages regarding the application of this process. Several recent HVOF systems are screened concerning the application of MCrAlY coatings for hot corrosion protective coatings on turbine blades. In this research project, the Design of Experiments (DoE) is used to built up factorial experimental designs. The aim is, besides a benchmarking, to find out the potential of the HVOF systems to produce high quality hot corrosion protective coatings. The main emphasis of these preliminary investigations is on the evaluation of bonding defects in the interface, the porosity, and the oxide content of the coatings.
Microplasma Spraying of Bioceramic Coatings
Authors: Borisov Yu. , Vojnarovich S. , Bobric V. , Ulianchich N. , Jansen J. , Wolke J.G. , Botisov Y. 
Published: September 2022

Abstract
Microplasma spraying process provides deposition of coatings on small sizes parts and components. An investigation into the process of production and properties of microplasma coatings from bioactive ceramics (hydroxyapatite, tricalcium phosphate and fluorinoapatite) was carried out. Bioactivity of the coatings was tested in vitro by estimation of growth and differentiation of osteogenic cell.
Low Pressure Wire Arc and Vacuum Plasma Spraying of NiTi Shape Memory Alloys
Authors: Halter K. , Sickinger A. , Zysset L. , Siegmann St. 
Published: September 2022

Abstract
Thermal spray technology offers the advantage of producing thin-walled parts. Especially thermal spraying of NiTi shape memory foils demands highest control of atmospheric conditions due to their affinity to e.g. oxygen, hydrogen and nitrogen at high temperatures. This article describes two inert thermal spray techniques in order to produce free-standing shape memory foils, namely low pressure wire arc (LPWAS) and vacuum plasma spraying (VPS). The advantage of low pressure wire arc spraying is the ability to use NiTi wire from commercial suppliers without the detour of powder production, which may result in additional undesired reactions and phases. The benefit of vacuum plasma spraying is the higher kinetic energy of the particles due to higher plasma gas amount and speed. Within the scope of this paper, coatings produced with both methods (LPWAS and VPS) are discussed with regard to their coating microstructure and physical / chemical properties, transformation temperatures (DSC), porosity (%) and their shape memory effect.
Effect of Aluminum Phosphate Sealing on the Elastic Properties of Plasma Sprayed Ceramic Coatings
Authors: Dubský J. , Chráska P. , Ahmaniemi S. , Vippola M. , Vuoristo P. , Mäntylä T. 
Published: September 2022

Abstract
Plasma sprayed ceramic coatings have much lower stiffness in comparison to sintered ceramics. The reason for that is their characteristic microstructure with porosity and microcracks. Microcracks decrease the interlamellar cohesion in vertical direction, but also affect the individual splat properties in the horizontal direction. For that reason sealing treatments are often applied with plasma sprayed ceramic coatings in order to improve their corrosion resistance and mechanical properties. In this paper the effect of aluminum phosphate sealing treatment on the elastic properties of plasma sprayed Al2O3 and Cr2O3 coatings were studied. Residual stresses in the plane of coating surfaces were compared using the X-ray diffraction analysis (XRD). A special four point bending device, designed for the X-ray diffractometer, was used in determining the effect of additional load on coating elastic behavior. In as-sprayed alumina coatings tensile stresses of about 400 MPa were detected while only about 40 MPa of compressive stresses were measured in the as-sprayed chromia coatings. Microstructural characterization revealed that sealing treatment had apparently affected the coating microstructure and filled some microcracks and interlamellar spacings. As a result, in both sealed coatings, compressive stresses of about 100 up to 150 MPa were observed. Also a better stiffness of both materials was detected during the bending of specimens. In addition, the sealing treatment increased nearly ten times the Young’s modulus, determined by XRD analysis under various tensile loads.
Integrated Machine Tool for Laser Beam Cladding and Freeforming
Authors: Nowotny St. , Scharek S. , Naumann T. 
Published: September 2022

Abstract
The repair and quick geometrical changes of components and tools are currently the most important applications of laser build-up welding. Advanced laser technology permits the integration of the main process steps into one machining center for a very efficient and flexible manufacturing process. The solution presented in this paper consists of a 3axes CNC milling machine, in which a 3 kW Nd: YAG laser, a coaxial powder nozzle, and a digitizing system are integrated. All functions (data processing, laser process, powder feeding, and milling) are controlled by one CNC controller using specially developed software. In the first step the workpiece needs to be adjusted to the machine table. Then the contour of the damaged surface is determined by either an optical or mechanical digitizing system. Using the resulting data, a software system generates automatically the laser build-up strategy and the CNC programs for the laser and the milling processes. After laser free-forming, a raw piece with an oversize of 0.3 to 0.6 mm is made. From this geometry the end contour is milled with an accuracy of some 10 microns. This way the machine produces a completely finished tool.
Influence of Carrier Gas Flow and Liquid Injection in the Plasma Jet on Plasma Characteristics During the Atmospheric Plasma Spray Process
Authors: Döring J.-E. , Vaßen R. , Stöver D. 
Published: September 2022

Abstract
The effect of argon carrier gas flow, ethanol- or water injection on the plasma-composition, -enthalpy and – temperature as well as on the entrainment from the ambient was investigated in comparison to the pure plasma condition of an Ar-H2-plasma. Additionally, the plasma gas flow rate and power levels were varied. The enthalpy, and thus the plasma temperature, as well as the composition and speed are determined by means of an enthalpy probe system. Spatial resolved data could be obtained by translating the torch via a robot so that a temperature and speed map shows the evolution of plasma features with increasing stand-off distance.
On the Stripping of Turbine Blades and Vanes: Mechanisms and Performances of Chemical Stripping for the Removal of NiCrAlY Thermal Spray Coatings
Authors: Scrivani A. , Soranzo M. , Rizzi G. , Bardi U. , Carafiello L. 
Published: September 2022

Abstract
The present paper is addressed to the study of chemical stripping processes used in order to remove Thermal Spray deposited Thermal Barrier Coatings. Thermal Barrier Coatings consist in a bond coat of MCrAlY alloy (where M means for Ni, Co or a combination of both), that can be obtained generally by Vacuum Plasma Spray or High Velocity Oxygen Fuel and in a top coat of Yttria Partially Stabilized Zirconia obtained by Air Plasma Spray. These coatings are applied to gas turbine components in order to improve their hot corrosion and oxidation resistance and their service life time through a reduction of the service temperature. The paper focuses on the removal of NiCrAlY bond coat performed by chemical attack (based on hydrochloric acid). Characterization of the blade and vane surfaces after removal of NiCrAlY coatings has been performed from the point of view of surface morphology, metallurgical structure and chemical composition. The efficiency of the acid solution in NiCrAlY removal has been investigated and the behaviour of two Ni based alloys substrates in aggressive environment has been tested. The HCl based stripping solution shows good performances in Vacuum Plasma Sprayed NiCrAlY coatings removal from Ni superalloys. The tested stripping procedure is fast and safe because no damages to base materials have been noted.
Development of Light Metal Matrix Composite Coatings Using High Velocity Thermal Spray Processes
Authors: Bach Fr.-W. , Engl L. , Josefiak L.A. 
Published: September 2022

Abstract
In this paper the development of thermal sprayed, hard phase reinforced aluminum based layers, in particular for coating light metal substrates is described. The aim of the project was to obtain wear resistant coatings for applications on light metal surfaces combined with other advantageous characteristics, especially good thermal conductivity. One possible application for these coatings can be seen in automotive light weight constructions as wear protection for brake discs or drums. Flame shock spraying as well as high velocity oxyfuel flame spraying (HVOF) were used as coating processes. As consumables mechanically alloyed powders consisting of aluminum and ferric oxide were used. Due to the high kinetic process energy developed by the selected procedures in connection with the exothermically reacting spraying material, a new light metal matrix composite was produced. One major advantage of this coating material is the in-situ synthesis of the hard particles in the aluminum matrix during the spray process resulting in good adhesion/cohesion properties. This research project includes an extensive analysis of the consumables including differential thermal analysis, SEM, and EDX. Furthermore, process parameters were optimized. This includes a characterization of the HVOF process using modern particle diagnostics. Besides good bonding properties proven coating characteristics are high thermal conductivity and thermal shock resistance as well as good wear behavior even at elevated temperatures. The results show that the developed coating system is a promising alternative for cast aluminum matrix composite materials used for wear stressed parts even at elevated temperatures.
HVOF Coating Characterization by Acoustic Emission Using Four-Point Bending Test
Authors: Bouaricha S. , Legoux J.-G. , Marcoux P. 
Published: September 2022

Abstract
Four-point bend test using acoustic emission (AE) was used to compare coating properties under mechanical solicitation, mainly the toughness and the spalling behaviour. Coatings are made from the same material; the 2005NS (WC-17Co), sprayed with an HVOF gun at various spray parameters. Coatings deposited on thin rectangular substrates were tested with the coating bent in tension and in compression. AE features like the event number, energy per event and cumulative energy were used to assess the damage in the coatings. The results are analyzed in relation with the coating microstructure.
Influence of Surface Laser Cleaning Combined with Substrate Preheating on the Splat Morphology
Authors: Liao H. , Gammoudi A. , Costil S. , Coddet C. 
Published: September 2022

Abstract
The morphology of sprayed splat raises the coatings adhesion and the properties which are determined by the spraying parameters. A lot of studies in this field show that the substrate surface temperature is a very relevant factor for the splat shape: the hypotheses of substrate surface wetability and contamination or absorption layer on the surfaces are supported by the fact that the near disk-shaped splat can be obtained in increasing the substrate temperature. In the PROTAL process, a short duration pulse laser is used to ablate the substrate just before powder spraying. This ablation is powerful enough to eliminate the contaminations on the substrate surface and to improve the adhesion. In this study the analyses of NiAl splat morphology on polished TA6V substrate were carried out using PROTAL process with different substrate temperatures and different heating modes: the flame and another laser. Results show that the temperature at which the disk shaped splat can be obtained was decreased dramatically by PROTAL process and PROTAL process combined with another laser has increased the adhesion strength of the coatings.
Modeling of Coating Formation and Heat Flux to Substrate by Particles and Plasma Jet in Plasma Spraying
Authors: Mariaux G. , Legros E. , Vardelle A. 
Published: September 2022

Abstract
This work deals with a 3-D transient simulation of the air plasma spraying of ceramic powders using a C.F.D. commercial code ESTET v3.4 that has been adapted to thermal plasma conditions. The mathematical model computes the distribution of particle velocity, temperature, molten state and size at impact and predicts the heat transfer to the substrate by plasma jet and particles. It incorporates the conversion from electrical to thermal energy in the torch nozzle as well as coating formation on the substrate. It makes it possible to predict the shape of the coating footprint when the torch and the substrate are fixed. The projections of the model are compared with experimental results that involve flow characteristics, time-dependant particle behavior in the flow and heat flux to the substrate.
Powder Densification and Spheroidization Using Induction Plasma Technology
Authors: Fan X. , Guo J. , Dignard N. , Normand C. 
Published: September 2022

Abstract
Spheroidization of powder particles is one of the successful commercial applications of induction plasma technology. A review is presented of case studies in which powder densification and spheroidization using induction plasma technology has played a key role in substantial improvement of powder quality and fluidity. Results are given for both metallic and ceramic powders at the pilot plant and industrial scale production. The presentation will cover both technical and economic features of the process. A detailed economic analysis of the process is presented for a production capacity of 15 and 30 kg per hour of tungsten carbide powder.
In-Flight Particle Imaging in Thermal Spraying with Diode Laser Illumination
Authors: Larjo J. , Hämäläinen E. , Kriikka N. 
Published: September 2022

Abstract
Imaging techniques have gained popularity in thermal spray diagnostics over the last decade. They provide large amounts of data for research, development and process monitoring. The most important measured spray parameters are particle temperature and velocity. The biggest advantage of imaging techniques compared to optical point measurements is that they provide instantaneous distribution measurements. We present the application of high-power diode laser illumination to detect weakly emitting particles in thermal spaying. This extends the feasibility of imaging diagnostics to several demanding environments, including cold spray, powder mixing region of a plasma spraying torch and low-pressure plasma spray.
Industrial On-Line Control of HVOF Spray Process Using SDC System
Authors: Bossoutrot C. , Braillard F. , Bansard S. , Vardelle M. , Fauchais P. 
Published: September 2022

Abstract
Coating production with reproducible properties within a range of values acceptable for the specific application requires a on-line control of the thermal spray process. Sprayed coatings present very often reproducibility problems due to spray parameter variations. In fact the quality of coatings is strongly linked to the temperature and velocity of particles at impact, and the temperature evolution of substrate and coating, before (preheating), during (spraying) and after (cooling). The particle temperature and velocity measurements require sophisticated devices rather expensive and not well adapted to work in the harsh environment of spray booths. Moreover in HVOF spraying, the particle surface temperature is generally below 2200K which make the measurements trickier than in plasma conditions. That is why, the Spray and Deposit Control (SDC) has been developed (collaboration between SPCTS laboratory of the University of Limoges and SNECMA Services), which allows to follow continuously both the light emitted by the hot particles (maximum intensity, mean trajectory and trajectory dispersion) and the substrate and coating temperature evolution during spraying. This simple and light system, fixed on the torch, has been tested in flame, plasma and HVOF spraying. The SDC measured parameters allow to develop easily process windows to obtain good working areas corresponding to specific coating parameters. In this study, the SDC on-line system is used in industrial conditions to optimize and control the HVOF spraying of carbide (WC-Co 17% wt) powders. A special attention is given to the possibilities of process parameters adjustment to regain the specific particle jet parameters and the good substrate temperature, in case of measured SDC parameters shifting. This study demonstrates the SDC system ability for an industrial on-line control of HVOF spraying, using process maps, to increase the consistency of coating properties. It is a step to a closed-loop control of the process through both the particle spray jet properties (mean trajectory and radiated flux distribution) and the target surface temperature.
Chemical Reactions between Hydroxyapatite (HA) and Titania during HVOF Spraying and In Vitro Response of the HA/Titania Composite Coating
Authors: Li H. , Khor K.A. , Cheang P. 
Published: September 2022

Abstract
Hydroxyapatite (HA)/titania composite coatings were deposited on titanium alloy substrates using the high velocity oxy-fuel (HVOF) technique. Chemical reactions between the mechanically blended HA and titania particles in the HVOF stream were analyzed. Qualitative phase analysis through X-ray diffraction (XRD) on the composite coatings showed that the chemical reaction between titania and HA occurred during the impingement stage. High temperature differential scanning calorimeter (DSC) analysis revealed that the reaction temperature was 1410 C. The activation energy of the chemical reaction between HA and titania demonstrated a value of 5441.46 kJ/mol obtained through the multiple-heating-rate method. Chemical bonding caused by the reaction between the components was suggested, which may be mainly responsible for the trapping of titania particles during the impingement. Transmission electron microscope (TEM) observation identified the reaction zone and phase distribution area within the HA/titania composite coatings. It demonstrated that the reaction products located around titania were beneficial for the improvement of coating structure. Furthermore, in vitro bioactivity of the HA/titania composite coatings in simulated body fluid (SBF) was revealed. Results showed that the coatings were fully covered by a bone-like apatite layer after 7 days’ incubation.