bluuebunny/crossref_metadata_2025 huggingface dataset:
Production Coating Cost Comparison
Authors: Meyer P. , Rusch W.
Published: September 2022

Several attempts have been made in the past to compare the coating costs associated with different processes. These have been based normally on various process related assumptions. The comparisons have typically been biased by the views and objectives of the presenters. A realistic comparison of the process costs needs to be based on the actual production methods and the historical data. This paper presents the comparisons of the Vacuum Plasma process with two versions of the HVOF process. Both small and large part geometries are considered as well as part complexity. The cost data will be presented as an actual cost per part to coat, including both operating costs and amortized capital costs. This method is preferred over the theoretical calculation of the cost per pound of material sprayed. The latter method requires a number of assumptions and does not consider the limitations of production cycles and material handling.
Low-Cost High-Performance Coatings Produced by Internal Plasma Spraying for the Production of High Efficiency Engines
Authors: Barbezat G.
Published: September 2022

For the deposition of functional coatings in cylinder bores of automotive engines different thermal spray processes are reviewed. Extensive studies of the process reliability have shown that the internal plasma spraying can be used in the industrial area of the automotive industry. Already today this technology is introduced in Europe and major Japanese companies are in an advanced status of evaluation. This paper describes the main processes used for these engine cylinder coatings and gives some results on typical coating characteristics and friction engine tests. It was shown in engine tests that the friction between piston ring and cylinder wall can be significantly reduced. Further the oil consumption can be significantly reduced and the wear resistance increased. The cost of the developed coating solution can be considered as low for this type of application.
Development of Thermal Spray for Automotive Cylinder Bores
Authors: Cook D. , Zaluzec M. , Kowalsky K.
Published: September 2022

High volume production of a consistent, repeatable coating on the internal diameter of surfaces has been a challenge for engineers for many years. Ford Motor Company and Flame Spray Industries, Inc. have developed a Plasma Transferred Wire Arc (PTWA) process and method of applying a wear resistant thermal spray coating on the internal surfaces of aluminum engine cylinder bores. For this automotive application, many challenges existed, including: achieving coating adhesion capable of passing long term engine durability testing, obtaining optimum materials performance and wear resistance, and developing a low cost thermal spray process that would be capable of high volume manufacturing. A novel fluoride based flux surface preparation technique utilizing a non-hazardous chemical solution was developed. This allows a NiAl bond coat to be applied to a non-roughened aluminum surface, yielding high bond strengths with the consistency necessary for high volume production. Process and materials development produced a cylinder bore coating using inexpensive low carbon steel wire feedstock that resulted in a coating with less than 2% porosity. After completing a detailed materials testing program, it was determined that using low carbon steel wire feedstock with compressed air atomizing gas formed a unique thermal spray coating system consisting of an iron/iron oxide (Fe/FeO) structure that exhibited excellent tribological properties while maintaining compatibility with existing piston ring pack materials. The PTWA thermal spray process was designed to operate in a turnkey environment in excess of 100 hours before requiring maintenance or replacement of consumable components. To fully test this process, Ford completed a production prove out including extensive dynamometer and fleet engine testing. The PTWA process proved to be production capable while producing coated aluminum block engines that accumulated over 3 million miles of fleet vehicle tests with zero coating failures. The test engines also exhibited excellent performance including piston and ring wear, power output, oil consumption, and vehicle emissions.
Influence of Powder Size in Aluminum Oxide Coatings for Use in the Semiconductor Industry
Authors: Gansert Robert V.
Published: September 2022

Plasma spraying of aluminum oxide is attracting great interest as a method for depositing economical coatings for use in the semiconductor equipment industry. The microstructure and mechanical properties of the sprayed aluminum oxide coatings are critical to the coating usage in the semiconductor equipment application. The influence of powder size on the coating microstructure and mechanical properties for coatings used in this industry is investigated.
Investigation of the Photocatalytic Efficiencies of Plasma Sprayed TiO2-Fe3O4 Coatings
Authors: Ye F.-X. , Ohmori A. , Li C.-J
Published: September 2022

Owing to the much concern with global environmental problem, photocatalytic TiO2 coatings were obtained using plasma spraying technique. The influences of the content of Fe3O4 additive to the TiO2 powder on the phase composition, microstructure and photo-absorption of plasma sprayed TiO2 coatings were systematically studied. The photocatalytic efficiency of the sprayed coatings is evaluated through the photo mineralization of acetaldehyde. The UV-VIS-NIR absorption spectra of the deposited coatings were obtained by using Shimadzu UV-3100PC scanning spectrophotometer. The results showed that the TiO2-Fe3O4 coatings consist of anatase TiO2, rutile TiO2 and FeTiO3 ilmenite, and Fe2TiO5 pseudobrookite phase appears when the content of Fe3O4 additive is equal to or over 10%. The content of anatase TiO2 in the sprayed coatings decreases from 14.8% to 5.9% with the increasing of Fe3O4 content to 32.6%. It was found that TiO2 coatings can decompose acetaldehyde under the illumination of ultraviolet rays, and the degrading efficiency is improved with an increase in the content of FeTiO3 in the coatings. However, the presence of large amount of Fe2TiO5 compound will substantially lower the photocatalytic efficiency of the sprayed TiO2-Fe3O4 coatings for the unfavorable photo-excited electron-hole transfer process.
Fabrication of TiO2 Photocatalytic Coatings on PET by Thermal Spraying
Authors: Kanazawa T. , Ohmori A.
Published: September 2022

To provide the polyethylene terephtalate (PET) plastic material with photocatalytic property, anatase TiO2 powders were plasma sprayed under various plasma spraying conditions. The effects of spraying parameters and surface morphology of substrates such as PET and PET pre-coated with Cu on the microstructure, phase composition and photocatalytic activity of TiO2 coating were systematically studied. The photocatalytic activity of the TiO2 coating was evaluated by the decomposition test of acetaldehyde gas. From the experimental result, it was found that fabrication of TiO2 coating was possible on PET substrate at arc currents of 200, 300 and 400A. The TiO2 coatings were thicker with increasing arc current. However, the coating was not attained when the plasma spraying was carried out on steel substrate even at a high arc current of 400 A. In case of plasma spraying on PET substrate pre-coated with Cu, the coating was locally formed at the arc current of 200 A. At the current of 300 A, the coating was attained. It was found that all fabricated TiO2 coatings exhibited photocatalytic activity regardless of undercoat materials and spraying parameters from the acetaldehyde decomposition test. Even coatings with thin and locally formed layers also showed the same photocatalytic performance as other thick coatings. From the XRD analysis, the reason for the efficient photocatalytic activity in the coatings was due to the high anatase phase content.
Optimization of Axial Injection Conditions in a Supersonic Induction Plasma Torch: Application to SOFCs
Authors: Renouard-Vallet G. , Gitzhofer F. , Boulos M. , Fauchais P. , Vardelle M. , Bianchi L.
Published: September 2022

The aim of this paper is the optimization of Yttria Stabilized Zirconia (YSZ) particle injection in a supersonic induction plasma torch to improve the reproducibility of this plasma deposition process. Indeed, the optimization is necessary to eradicate clogging in the supersonic nozzle due to the constriction of the nozzle. Investigations of the relationships between the parameters of particle’injection and the in-flight properties of the particles are carried out using an ANOVA experiment design. The in-flight particle properties were determined using two commercial systems, the DPV 2000 associated with the CPS 2000 (temperature, velocity and diameter of in-flight cold particles) and the Control Vision system (divergence of plasma jet imagery). First results have shown the necessity of a new design of the injection probe; development that allowed to reach a good reproducibility in terms of particle velocity and molten state.
Advanced Oxide Ceramic Coatings for Applications Demanding High Wear Resistance
Authors: Niemi K. , Rekola S. , Vuoristo P. , Laurila J. , Vippola M. , Mäntylä T.
Published: September 2022

The paper deals with wear properties of various advanced oxide ceramic coatings deposited by plasma and HVOF spray processes. Several types of ceramic oxide coatings on the base of Al2O3, Cr2O3 and TiO2 are studied in the work. The coatings are characterised by their wear properties in slurry abrasion wear test with fine abrasives (kaolin) and in dry abrasion conditions with coarse abrasives (quartz sand). The surfaces of the wear tested coatings were studied by SEM. The results show that coatings with high homogeneity and minor porosity, especially HVOF sprayed and some plasma sprayed coatings perform extremely well in both of the wear tests used in the study. In the test with hard abrasive and high load, the coatings with lower interlamellar strengths seem to be more prone to wear than coatings with higher homogeneity, e.g. HVOF sprayed oxide ceramic coatings. The results can be explained on basis of type of the coating material and the coating microstructure.
Development and Application of WC-Cr3C2-Ni Coating with High Impact Resistance
Authors: Itsukaichi T. , Osawa S.
Published: September 2022

The aim of this study was to investigate a new generation of agglomerated and sintered composite (WC, Cr3C2, Ni and Cr) powders for improved impact and wear resistance. The poor impact resistance of conventional WC cermet coatings, such as WC-20%Cr3C2-7%Ni, WC-10%Co-4%Cr and WC-12%Co, has so far hindered their use in new industrial applications. Results of this study indicated that both durability and impact resistance of the deposits, sprayed with these new powders, were significantly improved, and their wear resistance was equal or superior to conventional WC cermet coatings. This was achieved by optimizing both the spray powder chemistry, and also the HVOF spray conditions (for the new powders) to cater to the improved quality requirements for wear, corrosion, and impact resistance. It is expected that the high impact resistance of the new generation powders will open up new markets for the use of HVOF coatings for construction machinery parts such as excavating tools and shovels. For instance, it was found that excavating tools with the coating demonstrated approximately 16 times longer life than conventional tools without the coating. The mechanism for improving the impact resistance of the coating was also investigated in this study.
Influence of Rare Earth Elements on the Corrosion Resistance of Fe-Cr-Ni Thermal Sprayed Coatings
Authors: He D.Y. , Jiang J.M. , Yan Y.Q. , Xiong D.J.
Published: September 2022

The advantage of cored wires, a new type of material in thermal spraying, is that it is easy to control their composition and convenient to develop new materials. This research is aimed at developing the Fe-Cr-Ni austenitic stainless steel corrosion-resistance thermal-sprayed cored wires with rare earth elements added. The experiments are conducted with arc spraying. The anodic polarization curves of the sprayed coatings of the developed wires and of the 1Cr18Ni9 solid wire are drawn by using MODEL 351 corrosion measuring system in the 0.5mol/L sulfuric and 3.5wt.% sodium chloride solution at a temperature of 20° C . For the sake of comparison, the substrate and the 18-8 wrought stainless steel are also measured. Results to date indicate good usability of thermal sprayed coatings in all the developed wires. Owing to added rare earth elements, the corrosion-resistance of coatings increases in the 0.5mol/L sulfuric solution. The wires with RE-3 added have exhibited good corrosion-resistance. Deterioration of the corrosion-resistance in the 3.5wt.% sodium chloride solution is caused by generation of crevices and inclusions between the deposited particles.
Influence of Thermal Spray Process on the Corrosion Behavior of High-Density 316 Stainless Steel Coatings in Simulated Marine Environment
Authors: Simard S. , Arsenault B.
Published: September 2022

Under marine and coastal conditions, the degradation by corrosion of low-alloyed steels is generally observed. In order to overcome such important corrosion problems, the use of thermal spray coatings made of noble materials may be an attractive solution. 316 stainless steel thermal spray coating, an iron alloy coating, is often considered for corrosion protection because of its low material cost. Also, the high velocity oxy-fuel (HVOF) is often the selected coating process because it is known to provide coatings with a very low porosity level preventing the corrosive media to reach the substrate. The present paper compares the corrosion behavior of wrought 316 stainless steel with sprayed coatings made of the same alloy on 1020 mild steel. The corrosion behavior of materials is studied under salt fog conditions and with electrochemical techniques in brine simulating the marine environment. The coatings have been sprayed by HVOF under usual conditions. The results of this study demonstrate that the material behavior with regard to corrosion is process dependent . The HVOF sprayed stainless steel coating is much more sensitive to corrosion than wrought stainless steel. Corrosion product appearing on the samples is not only linked to the corrosion of the substrate by diffusion of the corrosive solution through pores but is also generated by intrinsic corrosion of coating itself. An enhanced sensitivity of the coating with regard to corrosion is attributed to the surface of particles or droplets, which are most likely degraded during the spraying process. However, thermal spray coatings having performances as good as wrought stainless steel can be obtained. In the present work, it is demonstrated that coatings obtained using vacuum plasma spray (VPS) have similar corrosion properties than wrought stainless steel in simulated marine environment. The industries considering corrosion protection of their components in marine environments by the use of stainless steel coatings must be aware of the reliability of their coatings. During the usual HVOF spray process, particles or droplets of stainless steel 316 are subject to important modification leading to a loss of performance against corrosion. Oxidation of alloying elements necessary to obtain a good stainless steel most likely occurs. However, the use of vacuum sprayed stainless steel coatings results to efficient protection against corrosion in marine environment.
Development of Dense Corrosion Resistant Coatings By an Improved HVOF Spraying Process
Authors: Kawakita J. , Kuroda S. , Fukushima T. , Kodama T.
Published: September 2022

For 6 years, we have developed corrosion resistant coatings for the marine structural steels by using a thermal spray technique. Such a coating requires primarily impermeability and secondarily cleanliness. In order to make denser and highly corrosion resistant coatings, we selected spray materials and improved fabrication processes. In addition, some new methods were designed to evaluate the sprayed particle’s state and coating properties with high accuracy and sensitivity. An inert gas shroud system was attached with the commercial HVOF apparatus and this attachment enabled inflight spray particles to be accelerated over 750 m·s-1 and simultaneously to avoid to be oxidized. The coating of HastelloyC nickel base alloy by this process had zero through porosity and 0.2 mass% of oxygen content, leading to be comparable to the bulk material of HastelloyC in terms of corrosion resistance. This coating, formed on steel, demonstrated an excellent protective performance over 10 months in the marine exposure test.
Studies of Cavitation Resistant Thermally Sprayed and Welded Coatings
Authors: Marques P.V. , Lima C.R.C.
Published: September 2022

Cavitation is one of the most serious problems that affect hydraulic systems and components, mainly power turbines. Welding deposits have been traditionally used to protect components from cavitation damage. Since the protection process is normally associated to maintenance repairs (welding overlay), there are some difficulties related to weld distortion and residual stresses as well as some economic problems regarding to process efficiency and time. Thermal spraying has been recently tested as an alternative to welding in such applications. Some of the materials tested have been proved to be ineffective or inappropriate due to several causes like poor adhesion or mechanical damage. This work refers to a study of wear resistant coatings applied by thermal spraying and welding for cavitation resistance applications. The coatings were applied by High Velocity Oxygen Fuel (HVOF) and Flame Spraying and by Shielded Metal Arc Welding (SMAW). Hardness, roughness as well as cavitation resistance characteristics of the coatings were evaluated. The results show that the obtained coatings are promising for protection in cavitation resistance applications.
Erosion Behavior of WC-10Co-4Cr HVOF Coatings
Authors: Legoux J-G , Arsenault B. , Hawthorne H. , Immarigeon J-P
Published: September 2022

Among the WC based cermets coating materials, those using the 10%Co-4%Cr matrix demonstrate excellent wear and corrosion properties. In this paper the erosion behaviors of WC-10%Co-4%Cr HVOF coatings was evaluated under different erosion conditions. The coatings were obtained from the JP-5000 gun using kerosene as fuel and the Diamond Jet gun using propylene and hydrogen. Two types of powder morphology were used: the first type was coarse and angular while the second was smaller, porous and spherical. The coatings were submitted to dry and slurry erosion. Erosion tests were performed at room temperature for both dry and slurry erosion. Dry erosion was evaluated by jet erosion while for slurry erosion, two different tests were performed: Coriolis and jet impingement erosion. Experimental results show that for the same powder, the erosion resistance measured by the Coriolis test exhibits 100% variation while for jet impingement it varies only by 20% depending on gun and spray conditions. The results also show that the powder selection is one of the key factors controlling the coating performance. The selection of powder can affect the Coriolis erosion resistance by more than 300% and the dry and slurry erosion resistance by 75%. The results are analyzed as a function of the processing and coating microstructure.
Erosion and Abrasion Resistance of Boride and Carbide-Based Weld Overlays
Authors: Lapointe F. , Dallaire S.
Published: September 2022

WELD OVERLAYS, more specifically chromium carbide weld overlays, have been widely used as thick coatings to protect critical plant components from abrasion wear. These thick coatings have been also considered in applications involving severe erosion, their thickness being synonymous with long life protection. Recently, boride-based arc-sprayed coatings have been developed especially for erosion control. They have demonstrated their superiority in erosion resistance over various coatings including chromium carbide submerged arc overlays. This work was undertaken to produce dense boride-based coatings comparable in thickness with carbide-based overlays. A GMAW (Gas Metal Arc Welding) welding procedure was developed for depositing boride-based overlays from cored wires. A comparative evaluation of the hardness, erosive and abrasive wear resistance of these boride-based overlays with regards to chromium and tungsten carbide overlays was carried out. Abrasion and erosion wear testing demonstrated that boride-based overlays showed higher abrasion and erosion resistance than chromium and tungsten carbide-based overlays. Overlays with higher wear resistance can be obtained if appropriate welding procedure is used to decrease weld bead dilution and therefore increase coating hardness. Results also showed that boride-based coatings deposited by arc spraying posses higher erosion resistance than those produced by the welding process.
Plasma Sprayed Nanostructured Zirconia Coatings for Wear Resistance
Authors: Ding Chuanxian , Chen Huang , Liu Xuanyong , Zeng Yi
Published: September 2022

Nanostructured and conventional ZrO2 coatings were deposited by plasma spraying. The wear and friction properties of these coatings against stainless steel under dry and water lubricated conditions were comparatively studied respectively. The results obtained showed that the wear resistance of the coating produced using the nanostructured zirconia powder is greatly improved compared with the coating produced using the conventional powder. The wear rates of the nanostructured zirconia coatings are two-fifths and half of those of conventional zirconia coating under dry and water lubricated conditions. It is explained in terms of the optimization of microstructure and higher microhardness of the nanostructured coating. In comparison with the dry condition, the water lubrication improved the tribological properties of both nanostructured and conventional zirconia coatings, which could be attributed to the formation of a smooth surface mainly consisting of zirconia and Fe3O4.
Sliding Wear Evaluation of Hot Isostatically Pressed (HIPed) Thermal Spray Cermet Coatings
Authors: Stoica V. , Ahmed R. , Itsukaichi T. , Tobe S. , Escribano M.
Published: September 2022

The aim of this preliminary investigation was to ascertain the synergetic potential of two process technologies of thermally spraying and HIPing (Hot Isostatic Pressing) for tribological applications and address the key design factors, which need to be considered for successful applications of HIPed thermal spray WC-NiCrBSi coatings. The relative performance of the as-sprayed and hot isostatically pressed WC-NiCrBSi functionally graded coatings was investigated in sliding wear conditions. Results indicate that HIPing post-treatment can improve the sliding wear resistance of WC-NiCrBSi coatings. These coatings were deposited by a High Velocity Oxy-Fuel - JP5000 system and HIPing process was carried out at two different temperatures of 850°C and 1200°C. This study shows that un-capsulated HIPing can be successfully applied to functionally graded WC-NiCrBSi coatings, which has economical as well as technical incentives for industrial applications. Sliding wear tests were carried out using a high frequency reciprocating ball on plate rig using steel and ceramic balls. Results are discussed in terms of powder manufacture method, microstructural investigations, phase transformation, mechanical properties and residual stress investigations. Phase analysis by X-ray diffraction revealed transformations, which altered the phase composition such as the elimination of secondary phase W2C and metallic W and the formation of new phases containing Ni, Si and B after the post-treatment. The measurements of hardness, Young’s modulus and residual stress indicate that substantial improvements can be achieved due to simultaneous application of temperature and pressure during the HIPing post-treatment. Hardness and Young’s modulus measured by indentation method, increased after the HIPing process due to the transformations in the morphology and phase composition of the coatings. The residual stress evaluations by sin2Ψ technique using synchrotron x-ray diffraction showed a relaxation of residual stress fields in the coating with increasing temperature of the HIPing process.
Formation of Intermetallic Phases by Laser Alloying of Thermally Sprayed Ti and Al Coatings for Enhanced Wear Resistance of Lightweight Materials
Authors: Wilden J. , Frank H.
Published: September 2022

Lightweight materials such as Al and Ti alloys tend to show poor wear resistance. However, laser alloying of thermally sprayed coatings can be used to form intermetallic phases within the surface area to overcome this disadvantage and to build a metallurgical bond between substrate and coating. Such phases formed in an exothermic reaction may show excellent corrosion behaviour and wear resistance. These reactions can be used to influence the surface properties by remelting metallic coatings on Al or Ti substrates. With respect to the wear behaviour, Ti and Al intermetallics are of great interest. Ti and Al alloys were coated by Al, Ti, and Ni respectively. The different structures on the surface of the alloys depend first on the laser processing parameters resulting in the overheated melt and as well as the latent heat of the formed intermetallic phases. The experimental results clearly show that for short dwell times the latent heat dominates the solidification process and that at high solidification rates the microstructure formation becomes nearly independent from the process parameters. This effect is of special interest for industrial applications as quality requirements ask for robust processes. The paper discusses the metallurgical fundamentals of intermetallic phases and the energy balance of the solidification while giving a deep insight into the influence of different process parameters. Lastly, the properties of alloyed surfaces are discussed.
The Effect of Chlorine on Degradation Mechanisms of Thermal Sprayed Coatings at Elevated Temperatures
Authors: Uusitalo M. , Vuoristo P. , Mäntylä T. , Berger L-M , Backman R.
Published: September 2022

The significance of biofuels and the other chlorine-containing fuels in energy production is in strong increase. Serious erosion-corrosion problems in boilers combusting fuels with high chlorine-content have been detected frequently. A series of erosion-corrosion and corrosion tests were performed on thermal sprayed coatings and coating precursors in chlorine-containing environments in order to evaluate possibilities to utilize thermal sprayed coatings for erosion-corrosion protection in boilers combusting chlorine-containing fuels. A series of hot erosion and erosion-corrosion tests were performed on thermal sprayed coatings at elevated temperatures with and without chlorine. Carbide-containing HVOF coatings performed well in hot erosion tests, but they were completely destroyed in the presence of chlorine due to rapid oxidation of carbides. Metallic HVOF coatings with high chromium content performed well in both conditions. Iron-based arc-sprayed coatings with unhomogeneous microstructure suffered more hot erosion and erosion-corrosion damages than metallic HVOF coatings. The E-C (erosion-corrosion) resistance of carbide-containing coatings in the presence of chlorides was worse than expected. A series of oxidation tests were performed on various carbides in order to elucidate the effect of chlorine on high temperature oxidation behavior of carbides. TGA and isothermal oxidation tests proved that gaseous chlorine-containing species and also solid chlorides have a detrimental effect on oxidation resistance of tested carbides.
Effect of Thermal Sprayed Al on the Steam Oxidation Resistance of 9Cr-1Mo Steel
Authors: Sundararajan T. , Kuroda S. , Itagaki T. , Abe F.
Published: September 2022

Thermal spray of Al was carried out on the modified 9Cr-1Mo steel to evaluate the steam oxidation resistance of the sprayed Al coating. Atmospheric plasma spray process (APS) was used to coat aluminum on sandblasted 9Cr-1Mo steel substrate. The coating thickness was around 40 µm. The coated specimens were steam oxidized in four different temperatures, ranging from 600 to 750°C. The results show that the scale growth occurred in the interface between coating and substrate subsequently it penetrated into the coating structure. Al diffused into the alloy substrate with high solubility. The diffusion increased with increase in the steam temperature and test duration. Diffused aluminum formed the high hardness intermetallic compound in the substrate near the coating/substrate interface. With increase in the test duration, the intermetallic compound moved towards the bulk and at prolonged aging, it became dissolved. This was identified from the decrease in the micro hardness values at coating/substrate interface at prolonged duration. The scale growth at the substrate surface of Al sprayed steel was much controlled compared to the uncoated specimens.
Activated Combustion HVAF Coatings for Protection against Wear and High Temperature Corrosion
Authors: Verstak A. , Baranovski V.
Published: September 2022

Activated Combustion HVAF Spraying (AC-HVAF) involves a jet of air-fuel combustion products to deposit coatings of metallic and carbide powders. In the process, spray particles are heated below their melting temperature while accelerated to velocity typically 700-850 m/s, forming a coating upon impact with a substrate. Extremely low oxygen content and high density are distinguished features of the AC-HVAF coatings, resulting in their excellent performance under conditions of severe wear and corrosion. Besides new level of coating quality, the AC-HVAF process demonstrates outstanding technological efficiency and spray rates 5-10 times exceeding those of the HVOF counterparts. The paper presents results on characterization of selected metallic and carbide coatings and describes their applications.
Microstructure and Wear Performance of Spray & Fused NiCrBSiC/WC Composite Coatings
Authors: Kim H.J. , Hwang S.Y. , Lee C.H.
Published: September 2022

Characterization of flame sprayed and furnace fused NiCrBSiC alloy coatings with two different carbon contents and 15~45 wt.% WC-Co addition is described in terms of microstructure, microhardness, and differential thermal analysis. Microstructural development of these coatings before and after fusing treatment is discussed to identify the precipitates in the coatings. Optimum fusing conditions (time and temperature) for wear testing sample are investigated in terms of microhardness and porosity of the coatings. Wear performance of these coatings is also investigated by two-body and three-body abrasive and dry sliding wear experiments. Optimum tungsten carbide content of the coatings is also selected to improve wear performance and thus enhance the service life of the process roll for cold rolling steel plant. Finally, microstructure and microhardness of the furnace and induction fused coatings are compared with emphasis on the interface between the coating and the steel substrate.
Improved Heat Transfer by RF Plasma Produced Structured Surfaces
Authors: Bouyer E. , Henne R. , Müller-Steinhagen H. , Schäfer D. , Asano H.
Published: September 2022

Structured surfaces are needed for improving the heat transfer in a lot of industrial processes. The paper deals with the production and the characterization of coatings with rough and porous surface. Structured coatings of inconel or copper are deposited on copper tubes by means of radio-frequency vacuum plasma spraying. The microstructure as well as the surface roughness of the coatings are investigated. Boiling experiments are carried out on the coated tubes to measure their heat transfer coefficient. The results show that the coated tubes exhibit improved heat transfer values in comparison to smooth tubes. The enhancement ratio can reach more than 20 for inconel coatings.
Modified Nozzle for the Atmospheric Plasma Spraying
Authors: Schwenk A. , Nutsch G. , Gruner H.
Published: September 2022

A modified Laval-like-contour for a convergent-divergent nozzle is presented for the Atmospheric Plasma Spraying (APS). The influence of the nozzle design on the thermal and deposition efficiency as well as on the arc voltage fluctuations and the sound level of the plasma torch are investigated and compared with former investigations. The improvements of the quality of DC-Plasma sprayed Al2O3 coatings by the nozzle design is shown by the coating porosity, adhesive and breakdown strength. A 2D-model presents the gas dynamics inside the nozzle. The intention of this study is to promote the industrial application of convergent-divergent nozzles for the APS in conjunction with the optimisation of the plasma gas dynamics.
Characterization of LPPS Processes Under Various Spray Conditions for Potential Applications
Authors: Refke A. , Barbezat G. , Dorier J.L. , Gindrat M. , Hollenstein Ch.
Published: September 2022

Low Pressure Plasma Spraying (LPPS) is nowadays a well-established thermal spray process with a broad variety of important applications for functional surface coatings. The operating pressure for LPPS processes can vary in a wide range from typically 200 mbar down to only a few mbar. This leads to unconventional properties of the plasma jet, in terms of supersonic flow with strong shock structure at moderate pressure, towards rarefaction and frozen flow at very low pressure. In order to optimize and control the spray processes for specific applications, it is necessary to understand the underlying physical mechanisms. However, so far only limited knowledge has been established on the plasma jet properties and its interaction with the spray particles in LPPS conditions. We present several experimental investigations to characterize plasma spray processes under various pressure conditions. Measured plasma jet properties using a dedicated enthalpy probe system and imaging are combined with IR-pyrometry and velocimetry on the particles (DPV2000) to further improve the understanding of the plasma particle interactions. These results, along with spray deposit characterization, can be used to optimize the coating properties and explore further potential applications.
Effect of Chamber Pressure and Spray Distance on the Plasma Sprayed Alumina Deposition
Authors: Sodeoka S. , Suzuki M. , Inoue T.
Published: September 2022

The effect of the chamber pressure and the spray distance on the splat formation of the plasma sprayed spherical alumina powder was investigated. The velocity and the surface temperature of the sprayed particles were measured by DPV2000. The particle temperature was changed in wide range by the chamber pressure; a solid core remained in the sprayed particle at 30 kPa and the surface temperature reached to the boiling point of alumina over 90 kPa. At the higher temperature, the splashing behavior was explained by the model of liquid film stability. However, in the cooling stage after coming out from the plasma flame, the inhomogeneous temperature in the sprayed alumina particle led to the complex splashing. The temperature distribution in the molten particle is very important to consider the splat formation.
Microstructural Formation of Vacuum Plasma Sprayed Ti-6Al-4V Alloy
Authors: Salimijazi H.R. , Coyle T.W. , Mostaghimi J. , Leblanc L. , Tsantrizos P.
Published: September 2022

Titanium alloys are extremely reactive in the molten state, therefore near-net shape and complex shape components cannot be produced by many techniques used for steel, aluminum and other less reactive metals. The vacuum plasma spray (VPS) process is a well-known method for coating and forming reactive metals and alloys such as titanium alloys. In this study the internal microstructure of individual splats, porosity, and mechanical properties of Ti-6Al-4V deposited by vacuum plasma spray forming (VPSF) were studied using SEM, XRD, mercury porosimetry, image analysis and mechanical testing. Results described in a companion paper show that while tensile and yield strength rise with increasing initial powders size, elongation still remains as low as 1%. The as-sprayed structure consists of α’ martensite with a small amount of residual β between the martensite colonies as well as pores between the splats. The fracture surface within the splats is indicative of ductile failure. The low cohesion between the splats results in damage accumulation at the boundaries and failure at small elongations. Post deposition heat treatments were conducted to improve the coating structure and were successful in improving the ductility to levels approaching that of traditionally processed material.
High Velocity Continuous Combustion A Review of the Technology and Performance History
Authors: Hill H.A.
Published: September 2022

The High Velocity Continuous Combustion (HVCC) Spray System was invented in 1993. The HVCC process uses wire as a consumable feedstock. Atomization takes place in a supersonic air jet, which is produced using a converging-diverging nozzle arrangement. The arc point is located within this supersonic air stream, which produces extremely finely atomized particles averaging 30 µm in diameter. The morphology of the HVCC produced coatings are homogeneous and consist of flat splat platelets with thin, adherent oxides. Permeation by gases and liquids through coating structures is significantly lower than that typically seen for twin wire arc spray coatings. Wear and erosion resistance of materials are significantly better than the same material applied with twin wire arc spray. The HVCC process has been successfully deployed over the past 7 years. It has been successfully used in confined space, in-situ applications, where traditional High Velocity Oxy-Fuel (HVOF) processes cannot be used for reasons of safety and practicality. These include applications in the petrochemical, paper and pulp, utility and independent power generating industries. Many other more specialized workshop and in-situ applications have also been performed with success.
Plasma Spraying of a Perovskite Suspension for SOFC Cathodes
Authors: Monterrubio-Badillo C. , Ageorges H. , Chartier T. , Coudert J.F. , Fauchais P.
Published: September 2022

A perovskite suspension was air plasma sprayed (APS) with a direct current (dc) plasma jet. The process conditions including the standoff distance, plasma forming gases and their ratio influence on the perovskite deposits and splats characteristics were investigated. Particularly the molten state of particles, phases obtained, morphology and composition of splats were studied. The process consists in injecting a well dispersed stable suspension of submicrometric particles. The suspension was produced by attrition milling LaMnO3 perovskite powder (mean particle size of 0.8 µm). The plasma forming gases influences drastically the obtained phases in deposits. When the plasma gas mixture contains hydrogen the heat transfer is too high and the perovskite phase is decomposed but when the plasma forming gases is Ar/He or only Ar, just a very little quantity of perovskite is found to be decomposed in the plasma jet. With Ar/He, perovskite splats are well melted, but with argon there is a high percentage of semi-melted and non-melted particles.
Study on Finishing Wear Resistant Thermally Sprayed Coatings: Influence of Feed Stock Material, Spraying Parameters and Machining Parameters
Authors: Widen J. , Szczesny D. , Jahn S.
Published: September 2022

HVOF-sprayed coatings have become increasingly important for many different industries. Because of this, the ability to adjust coating process parameters according to a customer’s demands becomes a necessity. Several studies have been done on various powders, spray parameters, and the resulting coating properties such as coating hardness, wear resistance, and internal stress. On the other hand few studies have been published regarding post-treatment and finishing processes. This study is intended to investigate the entire production process, from thermal spraying to the ready-to-use finished layer; the primary points of consideration were hardness, surface quality (roughness), and resulting microstructure. The scope of this study is to present initial results of cylindrical grinding as a finishing process. Several different tungsten-carbide-based coatings of various compositions and particles sizes were produced by thermal spraying under varying kerosene-oxygen flow, spray distance, and powder feed rates. Machining parameters such as speed of workpiece rotation and longitudinal feed rate were tested as well.
Sialon Coating from Sintered Mixtures of Silicon Nitride and Oxides
Authors: Seong B.G. , Hwang S.Y. , Park J.M.
Published: September 2022

Silicon nitride and sialons are very attractive materials for thermal spaying, but the high temperatures of spray processes lead to their decomposition instead of melting. Therefore, the use of these materials as protective coatings has been very restricted. Nevertheless, researchers have tried to provide silicon nitride-based coatings using metallic or oxide binders. Oxide binder additions to silicon nitride have been quite successful. In this paper, mixtures of silicon nitride and oxides were prepared for the thermal spraying of silicon nitride-based materials by using a detonation gun. Powders for the spraying were prepared through mixing, sintering, crushing and sieving. To get an oxide binder of low melting point, three components of oxides, Al2O3-ZrO2-TiO2, were selected; the ratio of oxides was determined to have a low melting point. When the sintering temperatures were below 1400°C, phases of the powders and coating layers were composed of α-Si3N4 and oxides and any of sialon phases were not found. By sintering at the temperatures between 1400 and 1600°C in a nitrogen gas environment, χ(chi)-sialon (Si6Al10O21N4) and β’-sialon (Si3Al3O3N5) were formed. The ratio of β’-sialon increased as the sintering temperature increased. TiO2 was transformed to a nitride, TiN. During the spraying procedure χ-sialon was decomposed to amorphous binder, but β’-sialon was not totally decomposed. Finally a coating layer composed of tetragonal-zirconia and β’-sialon was made.
Oxidation Behavior of Electroplated MCrAlY Coatings
Authors: Khan Abdus , Duda Thomas , Taylor Alan , Moore Peter , Rutter Peter , Foster John
Published: September 2022

High temperature oxidation behavior of MCrAlY coatings was studied at several temperatures in the range from 800 to 1100°C. In this study the MCrAlY coatings were obtained by plating using CrAlY as precursor powders in an electrolytic bath containing nickel and cobalt salt in solution. The size of the precursor CrAlY powders used was generally below 10 um. As-plated coatings consisted of a random distribution of CrAlY particles in the Ni-Co matrix. The heat-treatment of the as-plated coatings at elevated temperature resulted in the development of a gamma and beta structure. Both as-deposited and oxidized coatings were characterized by optical, scanning electron microscope and electron beam microprobe. During oxidation the coatings formed alumina scale with a negligible amount of transient nickel and chromium oxides. The spallation resistance of the oxide scale was investigated by thermal shock testing. The test consisted of a rapid cooling from 1000°C to 100°C with a two- minute dwell time at the maximum temperature. The thermal shock test was conducted in a) as–deposited and heat-treated condition and b) after preoxidation at 800°C and 1050°C, respectively. The coatings retained the alumina scale during thermal shock cycling.
HVOF Coatings of Ball-Milled Al2O3/NiCr Dispersion-Strengthened Powders
Authors: Lugscheider E. , Zwick J. , Zhang H.
Published: September 2022

Nanostructured materials have a high potential to improve properties of thermal spray coatings. High-energy ball milling is an effective process to produce dispersion-strengthened powders with a homogenous nanoscale microstructure and superior mechanical properties compared to unstrengthened material. Because of the relatively low temperatures and heat flux during HVOF spraying, the microstructure of the powder particles can be maintained in the coating. In this study Al2O3- dispersion-strengthened NiCr powders were synthesised by high-energy ball milling, using optimised milling parameters. Thermal spray coatings were produced using the HVOF process. The improvement of the tribological behaviour and the potential for technical applications were evaluated. The study shows the favourable impact of mechanically alloyed MMCs on the tribological behaviour of HVOF coatings on the basis of an Al2O3-strengthened NiCr powder
Key Factors for Dense Copper Coating by HVOF Spraying
Authors: Isoyama K. , Kawakita J. , Kuroda S. , Yumoto H.
Published: September 2022

For thermal sprayed coatings, compactness of their constituent particles is required in many applications, e.g. to obtain impermeable anticorrosion coating in marine use. We investigated key factors to improve compactibility of deposited particles in HVOF sprayed coatings by condition measurements of spray particles. The results revealed that plastic deformability of the sprayed particles as well as their molten fraction was important to obtain the dense VHOF coatings.
Microstructure and Properties of HVOF-Sprayed TiC-Based Coatings
Authors: Berger L.-M. , Zimmermann S. , Keller H. , Schwier G. , Scholl R. , Thiele S. , Nebelung M. , Enžl R.
Published: September 2022

Advanced TiC-based spray powders contain molybdenum and nitrogen as alloying elements and consist of core-rim-structured (Ti,Mo)(C,N) hard phases embedded in Ni, Co or mixed Ni/Co binder phases. For the investigations of the present study, four powders with binder phase contents of 29 and 39 mass-%, corresponding to about 20 and 27 vol.-%, respectively, were prepared by agglomeration and sintering. Coating samples were sprayed using JP-5000 equipment and two spray parameter sets. During coating characterization, special emphasis was placed on the changes in chemical (carbon loss and oxygen uptake) and phase compositions during spraying and their correlation to the coating microstructures and properties. It was found that the decreases in carbon and nitrogen contents were practically independent of the spray parameters for all of the four powders, whereas the oxygen uptake was different for each of the powders. The effect of the oxygen content on different coating properties is discussed in detail. All coatings investigated in this work showed excellent properties. It is anticipated that TiC-based coatings sprayed from these types of advanced powders can complement thermal spray coating solutions based on WC and Cr3C2.
Development of HVOF Sprayed Aluminium Alloy Engine Bearings
Authors: Sturgeon A.J. , Reignier C. , Laing I. , Perrin C.
Published: September 2022

Aluminium-based plain bearings for gasoline internal combustion engines are traditionally manufactured by casting and rolling, followed by forming and boring. The application places severe demands on the bearing material and a combination of properties such as fatigue, seizure and wear resistance are required. These properties are achieved by using a multi-phase material comprising of a distribution of tin in an aluminium alloy matrix. HVOF has been investigated as an alternative process for bearing manufacture and as a route to producing novel bearing materials with microstructures that cannot be achieved using the conventional casting route. The work reported describes the use of different HVOF spraying systems and powder types to develop aluminium-tin based coatings for advanced bearing applications. The coatings are described in terms of microstructure characteristics. The fatigue performance of the advanced sprayed bearings is compared with conventional cast bearings.