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Plasma arc spraying
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Proceedings Papers
ITSC2024, Thermal Spray 2024: Proceedings from the International Thermal Spray Conference, 399-408, April 29–May 1, 2024,
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In glass mold industry, a surface treatment by laser cladding of a Ni based powder on cast iron is performed with a 4-kW continuous diode laser. For this, a robot programming method named "Wavering" was used. This method allows to cover large surfaces (higher than 5 mm). The cast iron substrate used during this work is employed for its heat exchange properties in glass mold Industry. However, it has drawbacks which are weak wear, corrosion, and abrasion resistance. Conventional techniques used to protect the molds, like Plasma Transferred Arc (PTA), affect the molds microstructure, but also the thermal and mechanical properties. The laser cladding of the Ni based alloy allows to protect the molds without affecting the cast iron thermal properties (and reduce the Heat Affected Zone length). The purpose of this research is to produce a well bonded Ni based melted powder without pores or cracks on large and curvilinear surfaces with the wanted geometry. The impact of the process parameters such as laser power, scanning speed and frequency on the coating geometry was investigated with an experimental design technique using the ANOVA (Analysis of variance) method. It was used to determine and represent the influence of each process parameter on the coating geometry (width, height, and circularity). This ANOVA analysis led to a parameter combination to optimize the Ni coating and the cast iron substrate quality by considering the industrial geometrical constraints. The bonding quality and the cracking behavior are also investigated on optimized parameters. Finally, it appears that laser cladding process leads to a better coating on curvilinear surfaces than other process like PTA.
Proceedings Papers
ITSC2023, Thermal Spray 2023: Proceedings from the International Thermal Spray Conference, 70-76, May 22–25, 2023,
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Plasma Transferred Wire Arc (PTWA) is a well-established thermal spray process that is used in high-volume production by multiple automotive OEMs. Benefits of these PTWA thermal spray coatings include closer bore spacing, improved thermal transfer, lower bore distortion, increased resistance to corrosion and abrasion, reductions in weight and friction, enhanced durability, and product cost savings. For automobiles, this leads to increased fuel economy and lower emissions. Millions of engine cylinder bores per year are coated using the PTWA thermal spray process. To ensure optimal surface coatings, it is vital to monitor the process variables. Although some process monitoring already exists in current production, new technological advancements allow for additional variables to be monitored. Arc voltage is of particular importance as it can be viewed real-time in situ to the PTWA process to determine the curvature of the feedstock wire. Straight wire is ideal for achieving peak system performance. If the wire has excessive curvature, it can lead to out-of-tolerance conditions that detrimentally affect the quality of the surface coating. Therefore, in-situ monitoring of wire curvature is both desirable and necessary for producing the highest quality PTWA thermal spray coatings possible.
Proceedings Papers
ITSC 2021, Thermal Spray 2021: Proceedings from the International Thermal Spray Conference, 298-306, May 24–28, 2021,
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Pulsed plasma transferred arc surfacing is presently used in many industrial applications to make protective layers against corrosion, temperature exposition, and excessive wear. Increasing wear resistance is especially important in areas of industry where titanium alloys are used, such as aviation and cosmonautics, because the wear resistance of titanium alloys is often weak. One way to increase the wear resistance is to deposit or form a cermet with a titanium matrix (TMC) on the surface of the part. The present study deals with the fabrication and characterization of TMC based on B4C. TMC with B4C was formed by cofeeding Ti6Al4V and B4C powder into a melting pool. It has been found that the deposited, relatively thick layers have homogeneously dispersed B4C grains in the matrix. The deposits are metallurgically connected to the substrate - Ti6Al4V. The TMCs were investigated in terms of microstructure and chemical composition. Wear resistance was determined using the linear pin test.
Proceedings Papers
ITSC 2021, Thermal Spray 2021: Proceedings from the International Thermal Spray Conference, 657-663, May 24–28, 2021,
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Wire atomization processes used to make refractory and high temperature alloy powders are relatively expensive due to the cost of feedstock, energy, and gas. A new process based on Transferred Arc Wire Atomization technology, however, has the potential to overcome these problems. This paper introduces the innovative process which, in combination with hydrogen generation, presents new opportunities for several alloys that can be more easily processed by plasma wire atomization. The new approach shows promise to reduce both fixed and variable costs for certain refractory and high temperature materials.
Proceedings Papers
ITSC 2019, Thermal Spray 2019: Proceedings from the International Thermal Spray Conference, 199-206, May 26–29, 2019,
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This study evaluates the effect of an external magnetic field on arc fluctuations in a cascaded plasma torch. End-on images of anode arc jets are captured by high-speed photography while associated arc voltages are measured. The results are presented and discussed.
Proceedings Papers
ITSC 2019, Thermal Spray 2019: Proceedings from the International Thermal Spray Conference, 650-658, May 26–29, 2019,
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In plasma spraying, hydrogen is widely used as a secondary working gas. Under low-pressure conditions, even small amounts of hydrogen can have a significant effect on the plasma jet as mechanisms such as diffusion and recombination come into play. This study investigates the influence of Ar-H 2 mixtures on electron densities, temperature distributions, and local composition in the plasma jet using optical emission spectroscopy. Several mechanisms reported in the literature are consulted to explain the observed phenomena.
Proceedings Papers
ITSC 2017, Thermal Spray 2017: Proceedings from the International Thermal Spray Conference, 228-234, June 7–9, 2017,
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Nowadays combustion engines are the most common way to impel vehicles. Thereby losses occur, due to cooling, exhaust gas and friction. Modern engines roughly dissipate 8% of the chemical energy stored in the fuel because of friction in different tribological systems. The highest potentials for optimisation can be found in the tribological system of inner surface of combustion chamber and piston ring. Besides friction, corrosive stress of inner surface of combustion chamber increases e.g. due to the utilization of auxiliary systems such as Exhaust-Gas-Recovery. In order to save energy, reduce emissions and enhance the lifetime of combustion engines innovative coating material systems need to be developed, especially for inner surface of combustion chamber. This study focuses on the development of innovative iron based materials for combustion chamber application using Plasma Transferred Wire Arc (PTWA) and Rotating Single Wire Arc (RSW) technologies. In order to improve the wear and corrosion resistance boron and chromium are added into the feedstock material. After deposition, different honing topographies are manufactured in order to evaluate their influence on the tribological behavior. Furthermore, electro-chemical corrosion tests are conducted by using an electrolyte simulating the exhaust gas concentrate. In conclusion an optimised coating material deposited by PTWA and RSW and improved surface topographies can be combined.
Proceedings Papers
ITSC 2017, Thermal Spray 2017: Proceedings from the International Thermal Spray Conference, 394-399, June 7–9, 2017,
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Iron-based hardfacing alloys are widely used to counteract abrasive and impact wear of industrial components soil in, sand and mineral processing applications. These alloys show a high performance to cost ratio as well as a low environmental impact. The wear resistance of the components hardfaced with these alloys depends on achieved coating microstructure i.e. on the alloys chemical composition, the coating method and process parameters selected. The present work focuses on iron based hardfacing alloys with varying amount of chromium, vanadium, tungsten, molybdenum, boron and carbon deposited by plasma transferred arc (PTA) overlay welding. Weldability, hardness, abrasive and impact wear of the overlays are presented and interpreted through their microstructure. The performance of the iron based overlays is compared with that of nickel-based metal matrix composite coatings with tungsten carbide (MMC) commonly used for hardfacing of parts subjected to severe abrasive wear. The hardness of the iron based overlays investigated ranges between 60 and 65 HRC while abrasive wear is typically below 20 mm 3 (ASTM G65, procedure A). Microstructure consists of different primary precipitated carbides or borides, a martensitic matrix and eutectic structures.
Proceedings Papers
ITSC 2017, Thermal Spray 2017: Proceedings from the International Thermal Spray Conference, 400-403, June 7–9, 2017,
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Laser cladding technology is widely used in industry to precisely apply tailored surface coatings, as well as three-dimensional deposits for repair and additive layer-by-layer fabrication of metallic parts. However, the processing of larger components, like tools for oil and gas production, is economically challenging due to the conventionally low deposition rates. Consequently, industry is requesting more powerful technologies that maintain the quality advantages of the laser technology, but also make the process more productive and time effective. The modern highest power diode lasers offer practical solutions for applying of large-area laser cladding with significantly increased productivity. Using a fiber-coupled diode laser of 20 kW power and the accordingly developed laser cladding heads, real deposition rates of metal alloys, e.g. Inconel 625, could reach 14 kg/h. With the new-developed powder nozzles with rectangular profile of the powder jet allows at a laser power of 20 kW single tracks with 45 mm-width can be produced. Besides the laser source, the processing laser head is the key parameter for a high productivity and efficiency of the whole cladding procedure. The paper presents a new generation of high-performance laser cladding heads with integrated process sensors, which guarantee a stable long-time operation at highest power levels. The deposition rates achieved with this technology are equal or even exceed typical values of the common PTA technique. Current applications are large-area coatings on power plant components, hydraulic cylinders for off-shore equipment, and large metal forming tools for automotive bodies.
Proceedings Papers
ITSC 2017, Thermal Spray 2017: Proceedings from the International Thermal Spray Conference, 404-407, June 7–9, 2017,
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The powder of HSS (HSS23, AISI M3:2) was deposited by pulsed-PTA method on to low alloyed steel substrate. The influence of pulsation frequency was evaluated on the surface of deposits and on their cross sections by both light microscope and by Vickers hardness measurement apparatus and extreme properties mapping (XPS). Surfacing parameters at current frequency from 0 to 200Hz were tested during deposition of single weld bead. Dilution and heat affected zone were evaluated and compared for all tested parameters. The presence of retained austenite after deposition was determined by X-ray diffraction. The beads deposited with different frequencies differ in their shape, dilution degree, microhardness and penetration depth. It was found that the microhardness increases with current frequency.
Proceedings Papers
ITSC 2017, Thermal Spray 2017: Proceedings from the International Thermal Spray Conference, 408-413, June 7–9, 2017,
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Tungsten carbide in nickel based self-fluxing alloy overlays has been dominating hardfacing applications due to its excellent properties, namely extremely high wear resistance. Nevertheless, there are still applications and limits which tungsten carbide has not conquered. This study focuses on (TiW)C 1-x which was deposited with several matrix materials and tested in wear, corrosion and impact resistance and benchmarked against tungsten carbide. Results for several other carbides such as (NbW)C 1-x , (VW)C 1-x , NbC 1-x and TiC 1-x overlays deposited by plasma transferred arc (PTA) and laser cladding (LC) will be presented and discussed. As a result of deposition trials and overlay testing, it was found that better thermodynamic stability of alloyed carbides allows them to be used in an iron based matrix and/or a matrix with a high chromium content, in applications requiring improved corrosion and oxidation resistance, better impact resistance and lower weight.
Proceedings Papers
ITSC 2017, Thermal Spray 2017: Proceedings from the International Thermal Spray Conference, 566-571, June 7–9, 2017,
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The objective of this research is to investigate the changes of the microstructure and mechanical property of aluminum based coatings manufactured by VLPPS along the radial directions of the plasma plume. Aluminum powders were sprayed with a F4-VB low-power plasma gun under a working pressure of 150 Pa. Coatings deposition is studied at different distances from the plasma plume impact. Front of the plasma plume, in-situ reactions between aluminum and substrate elements (such as Fe, Cr, Ni) present in the base metal take places. It mainly forms aluminum based intermetallic Al 3 Fe coating according to the XRD. Based on the SEM observation, the packed columnar microstructure mixed with nanometer particles is formed with a majority of pure vapor condensation due to evaporated particles from the plasma jet and/or aluminum coating already made. For different distances relative to the center of plasma plume (i.e. from 10 mm to 110 mm along the radial directions), the deposited coatings exhibit a lamellar binary structure which was formed by the mixed deposition of vapor and molten droplets. The coatings morphologies vary from nearly dense to loose and highly porous. Finally, the hardness of typical coating is investigated. The Al based intermetallic Al x Fe y coating, on the center of the plasma plume, reached 448HV 0.025 , which is much higher than those obtained at other positions.
Proceedings Papers
ITSC 2017, Thermal Spray 2017: Proceedings from the International Thermal Spray Conference, 1153-1157, June 7–9, 2017,
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Wear-resistant cobalt–based alloy (Stellite 12) coatings deposited by plasma transferred arc (PTA), commonly used to protect critical mechanical components in harsh environments, were modified by addition of hard ceramic particles (TiC) and solid lubricant compounds (MoS 2 and CaF 2 ) to improve the overall tribological performance. In this preliminary study, microstructural, microhardness and tribological analyses were carried out to assess: a) the feasibility of PTA deposition of thermally sensitive phases characterised by very low density; b) the effect of the addition of a mixture of soft and hard phases on the coating hardness; c) the effect of the modified composition in terms of wear resistance; d) the effect of the addition in terms of lubrication (friction coefficient and produced heat). Results showed that: a) an appropriate pre-consolidation of feedstock materials can be effective in preserving the heat-sensitive phases within the microstructure of PTA deposits; b) the addition of a total amount of 5% wt. of solid lubricants and reinforcing carbides produced a limited decrease in the coating hardness (about 13%) and an evident improvement in terms of friction coefficient but, on the other hand, a remarkable reduction (about 30%) in wear resistance. Further investigation will be addressed to optimize the composition of modified feedstock to counteract the softening effect of lubricant phases without depressing the self-lubrication behaviour.
Proceedings Papers
ITSC 2015, Thermal Spray 2015: Proceedings from the International Thermal Spray Conference, 836-840, May 11–14, 2015,
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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.
Proceedings Papers
ITSC 2015, Thermal Spray 2015: Proceedings from the International Thermal Spray Conference, 1086-1091, May 11–14, 2015,
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In nuclear plants, the replacement of hardfacing Stellite, a cobalt-base alloy, on parts of the piping system in connection with the reactor has been investigated since the late 60’s. Various Fe-base or Ni-base alloys, Co-free or with a low content of Co, have been developed but their mechanical properties are generally lower than that of Stellites. The 4th generation nuclear plants impose additional or more stringent requirements for hardfacing materials. Plasma transferred arc (PTA) coatings of cobalt-free nickel-base alloys with the addition of sub-micrometric or micrometric alumina particles are thought to be a potential solution for tribological applications in the primary system of sodium-cooled fast reactors. In this study, PTA coatings of nickel-base alloys reinforced with alumina particles were deposited on 316L stainless steel substrates. The examination of coatings revealed a refinement of the microstructure. Under the conditions of the study, the addition of alumina particles did not improve the micro-hardness of coatings but improve their resistance to abrasive wear.
Proceedings Papers
ITSC2014, Thermal Spray 2014: Proceedings from the International Thermal Spray Conference, 75-78, May 21–23, 2014,
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In this study, two high-Cr stainless steel feedstocks and a post-spray honing process are evaluated for potential use on cylinder running surfaces in passenger car engines. The two materials, X12 CrNi 25-4 and X6 Cr17, were deposited by plasma transferred wire arc (PTWA) spraying on aluminum cylinder bore surfaces that were mechanically roughened prior to coating. The coatings were then honed to a mirror finish using progressively finer diamond tools. Coating surfaces were analyzed by SEM and REM imaging, roughness profiles were recorded, and coating hardness and porosity were measured. The results are presented and discussed along with recommendations for additional work.
Proceedings Papers
ITSC2014, Thermal Spray 2014: Proceedings from the International Thermal Spray Conference, 88-93, May 21–23, 2014,
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In this investigation, high carbon steel wire is deposited on aluminum cylinder bores with different surface profiles by plasma transferred wire arc (PTWA) spraying. The first part of the study deals with feedstock materials, process parameters, droplet formation, and splat morphology. The second part deals with bead profiles, build rates, and the influence of substrate composition, temperature, and surface profile on coating characteristics including microstructure, morphology, composition, and bond strength.
Proceedings Papers
ITSC2014, Thermal Spray 2014: Proceedings from the International Thermal Spray Conference, 196-202, May 21–23, 2014,
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This paper describes the development of a numerical model and explains how it is used to investigate arc-cathode interactions in a plasma arc torch. The model is based on magnetohydrodynamic (MHD) theory and couples Navier-Stokes equations for a nonisothermal fluid with Maxwell’s equations for electromagnetic fields. The equations account for the internal geometry of the torch as well as arc current and gas type and flow rate. They are solved using CFD code and relevant boundary conditions and are shown to provide insight on arc dynamics and the effect of cathode shape on arc behavior.
Proceedings Papers
ITSC2014, Thermal Spray 2014: Proceedings from the International Thermal Spray Conference, 234-238, May 21–23, 2014,
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This study evaluates the effect of laser texturing on the bonding strength of cylinder bore coatings deposited by plasma transferred wire arc (PTWA) spraying. Experiments were carried out on an AlSi 9 Cu 3 engine block sectioned along a plane through the length of the bores. Cylinder surfaces were laser textured on one side and degreased and grit blasted on the other. Laser power, beam angle, and pulse count were varied to determine their effect on hole morphology and coating adhesion. After surface treatment, the engine block sections were rejoined and the cylinder bores were PTWA sprayed with high carbon steel. Coating samples were examined by SEM and cross-sectional analysis and adhesion tests were conducted. The bonding strength of the coatings on the laser textured portion of the cylinder bore was significantly higher than that of the coatings on grit-blasted surfaces and is shown to vary with laser power, beam angle, and total pulses or impacts per hole.
Proceedings Papers
ITSC 2013, Thermal Spray 2013: Proceedings from the International Thermal Spray Conference, 471-474, May 13–15, 2013,
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This study deals with two new material deposition processes in which raw materials are in the form of a thixotropic slurry. In one case, the slurry (Al 2 O 3 nanoparticles in an acrylic resin) is misted into an arc plasma jet and sprayed on a stainless steel substrate. By varying the volume content of nanoparticles and slurry supply rates, investigators were able to achieve uniform droplets, resulting in fine Al2O3 layers free of microcracks and pores. In the other process evaluated, pure aluminum particles were dispersed in a photosensitive resin, producing a slurry that was spread on stainless steel substrates then patterned with a UV laser. The patterned metal particles were heat treated, creating iron-aluminide intermetallic phases through reaction diffusions. The microstructure and composition of the patterned lines are analyzed by SEM and XRD and surface stress distributions associated with a Hilbert fractal pattern are simulated via finite element analysis.
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