Conference Paper

Energy efficiency by thermal spraying

Authors:
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Machines used by the basic industries of Russia (metallurgy, oil-gas processing and power engineering) are characterized by high metal consumption, which in turn lead to high energy consumption. Their service lives increase and their worn parts are restored by means of low-cost materials for restoration. The processes of Thermal Spraying (TS) are more effective than alternative methods in restoration and increase in service life. Such methods include electroplating, chemical and thermal processing. The results of research and experience have proven this. At the same time, the load on the environment is reduced in comparison with the alternatives by decreasing emissions. Based on OEM publications and our own experience, we analysed the efficiency of TS processes. Plasma spraying was excluded from consideration since it has no real alternative for refractory oxide coatings which are mainly used for gas turbines and jet engines. By the criteria of the coating’s quality, performance and cost arc of spraying, flame spraying, HVOF/HVAF, cold spraying and detonation spraying were compared. Commonly used materials for TS, such as metals and carbides in metal bond (cermet), were examined as sprayed materials. This paper shows that a combination of activated arc spraying and HVAF for producing wear and corrosion-resistant coating is a rational variant with respect to a wide variety of parts for the aforementioned industries. Examples of resource-saving in metallurgy, oil–gas processing and power engineering are shown based on our own TS experience in material, equipment and technology development. Keywords: resource saving, thermal spraying, HVAF, HVOF, arc spraying, metallurgy, power engineering, service life increase.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... [137] Considering several criteria such as environment friendliness, reliability and process adaptability, thermal spraying is more widely used than other methods of surface engineering in many industries including paper, biomedical, metal processing and electronics. [138,139] Plasma spraying of large-scale devices including mill rolls is another example of commercial application of thermal spraying in which cost and processing time are of crucial importance. [140] Due to its unique features such as reliability, thermal spraying has been widely used for the deposition of functional coatings, e.g. ...
... Apart from deposition materials, the overall cost of deposition remarkably varies for different thermal spraying processes due to their different deposition rates and outputs. [139] In case of practical applications, cold spraying has been developed from a laboratory technique to a reliable method of commercial deposition in the last 20 years. For instance, it has found practical applications in the production of electronics devices including central processing unit (CPU). ...
... [142] Among different methods of thermal spraying, plasma spraying has made the highest contribution (around 45%) due to its capability in deposition of ceramics with high melting temperatures. [139] Typical pore size and relative total cost (including consumables, processing, and initial capital investment) of some major deposition processes are compared in Figure 9(a) and 9(b), respectively. Compared to other methods, plasma spraying could produce dense coatings, and is among the most cost-effective methods for the deposition of nanostructured films. ...
Article
Photocatalysis is widely used for the degradation of organic pollutants, with TiO2 and ZnO as the best candidates with unique properties. However, agglomeration and recycling are major challenges in practical photocatalysis applications. Advanced deposition processes can provide nanotubular or hierarchical structures that are more promising than suspended particles. More importantly, higher efficiency of photoelectrocatalysis than photocatalysis for the degradation of persistent organic pollutants including perfluorooctanoic acid (PFOA) necessitates catalyst immobilization. Photoelectrocatalysis exhibited remarkably higher efficiency (56.1%) than direct photolysis (15.1%), electrocatalysis (5.0%) and photocatalysis (18.1%) for PFOA degradation. This paper aims to review the progress in the application of anodizing and thermal spraying as two major industrial surface engineering processes to bridge the gap between laboratorial and practical photocatalysis technology. Overall, thermal spraying is considered as one of the most efficient methods for the deposition of TiO2 and ZnO photocatalytic films.
... Korobov and Salimov [18] and Murthy and Venkataraman [19] have carried out a detailed study on different coating processes like arc spraying, cold spraying, plasma spraying, flame spraying, HVOF spraying and detonation spraying and reported HVOF as the cheaper option with respect to output and cost. ...
Article
Full-text available
High cost imported components of seamless steel tube manufacturing plants wear frequently and need replacement to ensure the quality of the product. Hard chrome plating, which is time consuming and hazardous, is conventionally used to restore the original dimension of the worn-out surface of the machine components. High Velocity Oxy-Fuel (HVOF) thermal spray coatings with NiCrBSi super alloy powder and Cr3C2 NiCr75/25 alloy powder applied on a 50CrMo4 (DIN-1.7228) chromium molybdenum alloy steel, the material of the wear prone machine component, were evaluated for use as an alternative for hard chrome plating in this present work. The coating characteristics are evaluated using abrasive wear test, sliding wear test and microscopic analysis, hardness test, etc. The study results revealed that the HVOF based NiCrBSi and Cr3C2NiCr75/25 coatings have hardness in the range of 800–900 HV0.3, sliding wear rate in the range of 50–60 µm and surface finish around 5 microns. Cr3C2 NiCr75/25 coating is observed to be a better option out of the two coatings evaluated for the selected application.
Article
Full-text available
In Russia Federation, coal fired power plants account for about 29% of the total electricity generation. Russia's "Energy strategy until the year 2020" projecting a 75% increase in coal production as well as a significant increasing role for coal in electricity production. The long operating period of the majority of the coal-fired boilers resulted in considerably reduced efficiency and availability, while the repair and maintenance expenses made about 12% of the primary cost of the electricity production. Therefore, it is important to encourage the use of modern, efficient and cleaner coal combustion technologies. This paper presents the most significant problems related to the current operation of the coal power plants in Russia and estimates the most relevant options to implement the clean coal technologies in Russians coal power sector.
Article
Full-text available
In this article, we will show how unconventional nanoscale composite coatings can be formed using conventional wire-arc thermal spray systems. The as-sprayed SHS7170 wire-arc coatings are found to develop an amorphous matrix structure containing starburst-shaped boride and carbide crystallites with sizes ranging from 60 to 140 nm. After heating to temperatures above the peak crystalline temperature (566 °C), a solid/state transformation occurs that results in the formation of an intimate three-phase matrix structure consisting of the same complex boride and carbide phases, along with α-iron interdispersed on a structural scale from 60 to 110 nm. The nanocomposite microstructure contains clean grain boundaries, which are found to be extremely stable and resist coarsening throughout the range of temperatures found in boilers. Additionally, the properties of the coating are presented including the bond strength, hardness, bend resistance, and impact resistance. The sprayability, forgiveness, and repairability of the SHS7170 wire-arc coatings are explained in detail, with an emphasis on field applicability in boiler environments. The performance of the SHS7170 coatings in boiler environments is measured via elevated temperature-erosion experiments conducted at 300, 450, and 600 °C using bed ash from an operating circulating fluidized-bed combustor boiler, and the results are compared with those for existing boiler coatings.
Conference Paper
Due to their enhanced mechanical properties and high range applications in severe environments use, there is ongoing research in the area of amorphous metallic glasses and nanostructured materials. The science and mechanisms leading to these exceptional properties are discussed herein. The arc sprayed coatings produced for study in this paper show remarkable performance and are analyzed in-depth using advanced characterization techniques such as X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Additional analysis of the mechanical properties of the coatings show enhanced strength and hardness, good wear and corrosion properties, along with high temperature corrosion and oxidation resistance.
Conference Paper
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.
Book
This book guides readers through the systematic analysis of Arc Spraying: one of the most widespread and important thermal spraying methods. Along the way, readers from industry and research laboratories become familiar with the features of the process and physical-chemical regulations of particles in flight, coating formation, internal coating properties, and their output parameters. The book is ideal for engineers, technicians, and scientists engaged in welding and thermal spraying and stands as an excellent reference for students interested in advanced coatings technology. © Springer International Publishing Switzerland 2016. All rights reserved.
Article
The elevated temperature erosion resistance of experimental amorphous thermal spray coatings was determined in a laboratory elevated temperature erosion tester. Test conditions attempted to simulate the erosion conditions found at the combustor waterwall tubes in fossil fuel fired boilers. Erosion tests were conducted on four experimental amorphous thermal spray coatings, using the bed ash retrieved from an operating coal fired boiler. An experimental arc-spray process was used to spray coatings. These results were compared with erosion test results of two common structural materials, two commercially available arc-sprayed coatings, and a proprietary HVOF coating. Test results indicated that the Duocor coating had the highest erosion resistance among the four experimental coatings, it showed equal resistance to the HVOF coating (DS-200). Compared to AISI 1018 steel, both Duocor and DS-200 coatings reduced material wastage by 26-fold. Other test results indicated that the XJ-16, 60T and Armacor M coatings had equal erosion resistance reducing material wastage approximately 7-fold, while Armacor CW reduced by 10-fold. Only slightly better than the unprotected 1018 steel, the X-20 coating performed poorly on erosion tests. The high erosion resistance of Duocor and DS-200 coatings was attributed to their high densities and fine splat structures.
Article
Electrolytic Hard Chrome (EHC) method, which is still widely utilized in the printing, automotive and off-shore industries, is coming to be subjected to strong restrictions in the next decade in the use of hexavalent Chromium, with the increasing strengthening of European normative. Alternative methods to EHC, such as High Kinetic Thermal Spray Technology, have shown a growing interest the past decades. Compared to conventional HVOF processes which pioneered the development of WC-based coated materials, newly developed HVAF systems are processing at higher kinetic energy and more particularly at lower temperature, which significantly reduces feedstock oxidation and decarburization, then increasing respective wear and corrosion resistance properties. A preliminary investigation of HVOF- and HVAF-sprayed coatings is here proposed on the evaluation basis of material decarburization, coating porosity and microhardness. Role of carbides size and morphology on coating adhesion strength, wear and corrosion resistance properties are preliminary discussed.
Article
From the appearance of HVOF thermal spray system on 1980s, WC cermet coatings have been used as anti-wear coatings in many industrial applications. Recently, WC cermet spray materials were applied to new thermal spray method such as Warm Spray and Cold Spray for improvements of coating performance, spray efficiency and so on. Gas velocity values of the latest models of HVAF torches are higher than those of the previous ones. Therefore, dense WC coating can be fabricated by using the latest HVAF process. In this study, agglomerated and sintered WC-Co-Cr powder properties and spray conditions were investigated to understand the influence on HVAF spraying. From the results, it was clear that coating wear performance was improved by using higher gas speed conditions and powder composed of fine CoCr particles. It is also clear that coating hardness was improved by employing fine particles.
Conference Paper
Before 1970s, the focus of industrial development was mainly on manufacturing, but since the 1980s, it has shifted towards quality control and maintenance due to increasing environmental issues. Based on these trends, spray coating could be established in Korea due to its environmental friendly nature. In the 1980s, the thermal spray market in Korea was based on commercial and military aero space industry (Korean Air Line and Sam Sung Aerospace respectively). And after 1990s, the market domain expanded rapidly to the steel, automobile, textile, paper, electronics, and boilers industry etc. Hence, more than 40 thermal spraying companies are committed in Korea. From the start of 21st century, IT and energy resource have surfaced as potential fields for application of thermal spray. Ceramic coatings on various components of semiconductor fabrication equipment as well as manufacturing of solid oxide fuel cell are some of the representative applications. Bulk metallic glass materials and other functional materials also have potential application in many fields such as aero space and biomedical etc. Nowadays the focus is on upgrading the spray coating technology from being a tool for repairing and surface modification of products to being a main production method for making bulk and products. In this address, the share of spray industries in the economy of Korea and its applications are introduced. Also, Korean spray technology is compared with world standards and the necessary up-gradation for future development is suggested.
Conference Paper
Iron based wire feedstocks can represent a technical as well as economical alternative to conventional carbide reinforced feedstocks for wear protection applications. Within the frame of this work, different iron based feedstocks were developed as cored wires. In order to produce wear resistant coatings, the wires contain up to 6 wt.-% of boron. When processed by thermal spraying, these feedstocks form hard, partially amorphous coatings with embedded nanocrystalline boridic precipitations. In order to further improve the wear resistance, for some wires chromium carbide was blended into the powder filling. Coatings were produced from all feedstocks by electric arc spraying. The coatings were investigated by light optical microscopy, XRD, transmission electron microscopy and hardness measuring. In order to compare the coatings amongst each other with regard to their wear behaviour, the coatings were tested on a pin-on-disc tribometer.
Article
Features of gas-flame supersonic spraying (GFS) methods of coating are discussed. Comparison of typical models of equipment used for these processes—JP-5000, DJ, and Intelli-Jet units—is performed with respect to their gasdynamic parameters, spraying capacity, material utilization factor, and cost of coating application. Fields of their application are mentioned.
Conference Paper
Electrolytic Hard Chrome (EHC) method, which is still widely utilized in the printing, automotive and off-shore industries, is coming to be subjected to strong restrictions in the next decade in the use of hexavalent Chromium, with the increasing strengthening of European normative. Alternative methods to EHC, such as High Kinetic Thermal Spray Technology, have shown a growing interest the past decades. Compared to conventional HVOF processes which pioneered the development of WC-based coated materials, newly developed HVAF systems are processing at higher kinetic energy and more particularly at lower temperature, which significantly reduces feedstock oxidation and decarburization, then increasing respective wear and corrosion resistance properties. A preliminary investigation of HVOF- and HVAF-sprayed coatings is here proposed on the evaluation basis of material decarburization, coating porosity and microhardness. Role of carbides size and morphology on coating adhesion strength, wear and corrosion resistance properties are preliminary discussed.
Article
Four high velocity thermal spray guns were evaluated in the production of 10% Co-4% Cr tungsten carbide (WC) cermets. Three high velocity oxygen fuel guns (JP-5000, JP-5000ST, and Diamond Jet [DJ]-2700) and one plasma gun (Axial III) were used to spray the same angular, agglomerated, and crushed WC-10Co-4Cr powder. The DPV-2000 was used to monitor the in-flight velocity and temperature of the WC cermet-sprayed particles. From those values, spray conditions were selected to produce coatings that were evaluated in terms of porosity, hardness, and deposition efficiency. Results show that the plasma Axial III provides the highest particle temperature, between 2000 °C and 2600 °C, depending on the spray conditions. The JP-5000 imparts the highest velocity to the particles, between 550 and 700 m/s, depending on the spray conditions. The ST version of the JP-5000 provides the same velocity as the standard version but with lower particle temperature. The DJ-2700 sprays particles with temperature and velocity between those of the JP-5000 and the Axial III. Minimum porosity values of 2.1%, 3.7%, and 5.3%, respectively, were obtained for the JP-5000, the DJ-2700, and the Axial III guns. The porosity and carbide degradation are found to depend mostly on the particle velocity and temperature, respectively. The values for the Vickers microhardness number (200g) ranged from 950 to 1250. Measurements of the deposition efficiency indicated a variation between 10% and 80%, depending on the spray conditions and the gun used.
Article
This paper is devoted to thermal spraying and presents the state of our current knowledge, as well as the following research or development needs: spraying heat sources, i.e., flame, high-velocity oxifuel flame (HVOF), detonation gun (D-Gun), and plasma torches; particle heat and momentum transfer (measurements and modeling), process on-line control, powder morphologies, and injection within the hot jet and reactions with environment; coating formation, i.e., particle flattening and solidification, splat layering, residual stresses, coating microstructure, and properties; and reliability and reproducibility of coatings.
Article
The effect of severe substrate topography on the microstructure of thermally sprayed coatings has been relatively neglected, but is critical in controlling the performance of thick electric arc sprayed steel shells for rapid tooling applications. This paper shows how the spray angle and the atomizing gas pressure control the distribution of porosity and oxide in steel sprayed in and around cylindrical holes of different diameter and depth. Droplet splashing and the secondary deposition of splash droplets caused systematic variations in microstructure. In particular, the origin of the phenomenon of “bridging,” the premature closure of features, has been revealed by microstructural analysis and explained in terms of the trajectories of droplets. The filling of features with higher-quality material can be aided by using a low atomizing gas pressure, reducing the oxygen partial pressure of the surrounding atmosphere and careful selection of the spray angle.
Article
Nowadays, wire-arc spraying of chromium steel has gained an important market share for corrosion and wear protection applications. However, detailed studies are the basis for further process optimization. In order to optimize the process parameters and to evaluate the effects of the spray parameters DoE-based experiments had been carried out with high-speed camera shoots. In this article, the effects of spray current, voltage, and atomizing gas pressure on the particle jet properties, mean particle velocity and mean particle temperature and plume width on X46Cr13 wire are presented using an online process monitoring device. Moreover, the properties of the coatings concerning the morphology, composition and phase formation were subject of the investigations using SEM, EDX, and XRD-analysis. These deep investigations allow a defined verification of the influence of process parameters on spray plume and coating properties and are the basis for further process optimization.
Article
Tungsten carbide (WC) thermal spray coatings have gained increased acceptance for commercial aircraft applications driven by the desire to replace chromium electroplate due to environmental and economic considerations. In order to confidently replace electroplated chrome with WC thermal spray coatings in aircraft applications, the coatings must demonstrate fatigue and wear characteristics as good as or better than those of electroplated chrome. Previous research in this area has shown that the fatigue life of the WC thermal spray coatings can be improved by inducing compressive residual stresses in the coating. This paper compares the wear characteristics of several types of WC thermal spray coatings with those of electroplated chrome in sliding wear tests using the “block-on-ring” procedures described in the ASTM G77 standard. Wear results are interpreted in terms of coating residual stresses and in terms of x-ray diffraction (XRD) and scanning electron microscope (SEM) analyses.
Thermal spraying -the current status: Proc. of int. sciencetechnical seminar
  • V Baranovsky
Baranovsky, V., HVAF -equipment for supersonic air-flame spraying, [in Russian]. Thermal spraying -the current status: Proc. of int. sciencetechnical seminar. Ural State Technical University: Ekaterinburg, Russia, pp. 4-30, 2010.
Thermal spraying coatings and environmentally friendly production, maintenance and repair of machines
  • Yu A Kharlamov
Kharlamov, Yu.A., Thermal spraying coatings and environmentally friendly production, maintenance and repair of machines, [in Russian], Heavy Machinery (Tyazheloe mashinostroenie), 2, pp. 10-13, 2000.
Comparison of Operating Characteristics for Gas and Liquid Fuel HVOF Torches
  • W Rusch
Rusch, W., Comparison of Operating Characteristics for Gas and Liquid Fuel HVOF Torches. Proc. of ITSC 2007, ASM: Beijing, China, pp. 572-576, 2007.
Progressive methods of repair of metallurgical equipment
  • V I Tsekov
Tsekov, V.I., Progressive methods of repair of metallurgical equipment, [in Russian], Metallurgy: Moscow, Russia, 1976.
Fuel and energy complex of Russia today and tomorrow. Aspects of reliability and safety
  • V M Neuimin
Neuimin, V.M., Fuel and energy complex of Russia today and tomorrow. Aspects of reliability and safety, [in Russian], Reliability and energy security, 1, pp. 7-13, 2008.
The effectiveness of road transport
  • N Korolev
Korolev, N., The effectiveness of road transport, [in Russian], Moscow, Russia, 1984.
JP-5000, the HVOF of the 21st century
  • M J Breitsameter
  • M Prosperini
JP-5000, the HVOF of the 21st century. Breitsameter, M. J., Prosperini, M., Proc. of 4 th HVOF Colloquium, DVS: Erding/Munchen, Germany, pp. 119–125, 1997.
Cold spraying. Theory and practice
  • A P Alkhimov
  • S V Klinkov
  • V F Kosarev
  • V M Fomin
Alkhimov, A.P., Klinkov, S.V., Kosarev, V.F., Fomin, V.M., Cold spraying. Theory and practice, [in Russian], Fizmatlit: Moscow, Russia, 2010.
Increase the service life of heat engineering equipment based on application of wear-resistant coatings
  • V K Krainov
Krainov, V.K., Increase the service life of heat engineering equipment based on application of wear-resistant coatings, [in Russian], General issues of power engineering. 2, pp. 14-21, 2002.
Development of cored wires for coatings against wear and hot corrosion
  • Y S Korobov
  • V I Shumyakov
  • M A Filippov
  • S V Nevezhin
Korobov, Y.S., Shumyakov, V.I., Filippov, M.A., Nevezhin, S.V., Development of cored wires for coatings against wear and hot corrosion, [in Russian]. Welder in Russia, 4, 2012.
Development of Iron Based Wire Feedstocks and Their Processing by Electric Arc Spraying
  • K Bobzin
  • T Schläfer
  • L Zhao
  • P Kutschmann
Bobzin, K., Schläfer, T., Zhao, L., Kutschmann, P., Development of Iron Based Wire Feedstocks and Their Processing by Electric Arc Spraying. Proc. of ITSC 2009, ASM: Las-Vegas, NV, pp. 844-848, 2009.