Thermal Spray Coating Paper

Thermal Spray Coating Paper - Thermal Spray Coating and Its...

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Unformatted text preview: Thermal Spray Coating and Its (Potential) Applications in Indonesia Budi Prawara R&D for Electrical Power and Mechatronics, Indonesian Institute of Sciences e-mail : [email protected]; [email protected] 1. Overview Thermal spraying is a coating process. Thermal spraying consists of processes in which spray materials (wire or powders) are heated to the plastic or molten state, inside or outside of the spray equipment, and then accelerated by a compressed gas stream to the substrate. towards the workpiece surface. The particles strike the substrate, flatten, and form thin platelets (splats) that conform and adhere to the irregularities of the prepared substrate and to each other. As the sprayed particles impinge upon the surface, they cool and build up, splat by splat, into a laminar structure forming the thermal spray coating. Thermal spray coating is a well-established coating technique comparing with other coating processes. The advantages of thermal spray coating comparing with hard chrome, physical vapour deposition (PVD), chemical vapour deposition (CVD) are: - high deposition rate - low heat input process - proven technology - variety of coating materials - high degree of repeatability - resource of utilization - favorable economics The thermal spray coating technology has been used in various industry ranges from aerospace to electronic industry and the utilization of this technology is growing fast in the industrial country. The market of thermal spray coating in Indonesia is widely opened, but there still few utilization from the industry and thermal spray workshop due to the limitation of technology and equipment. This paper provides a technological view and potential market of thermal spray coating in Indonesia. 2. Thermal Spray Process Thermal spray processes may be categorized as either combustion or electric processes. Combustion processes include flame spraying, HVOF (High Velocity Oxygen Fuel) spraying, and detonation flame spraying. Electric processes include arc spraying and plasma spraying. Coating can be applied under standard atmospheric conditions, or in specialized, highly controlled atmospheric condition - even under water. Coating can be applied by hand, or with the automated precision of software- driven robotics. 2.1. Combustion processes 2.1.1. Flame spraying (a) Wire flame spraying. The wire flame-spraying is a process of thermal spraying in which a wire shaped feedstock material is melted by a fuel-oxygen flame and is accelerated with an atomizing gas onto the prepared surface to be coated. The coatings deposited in this way usually are porous and contain oxides. They are used mainly as wear and corrosion protection as well as electrical conductive coatings. Fig. 2-1 and Fig. 2-2 show a schematic of a typical flame spray system and a typical wire flame spray gun respectively. The wire flame spray gun consists of a drive unit with a motor and drive rollers for feeding the wire and a gas head with valves, gas nozzle, and air cap that control the flame and atomization air. Compared with arc spraying, wire flame spraying is generally slower and more costly because of the relatively high cost of the oxygen-fuel gas mixture compared with the cost of electricity. However, flame spraying systems, at only one-third to one-half the cost of wire arc spray systems, are significantly cheaper. Flame spray systems are field portable and may be used to apply quality metal coatings for corrosion protection. Fig. 2-1. Wire fleme spray system [1] Fig. 2-2. Wire flame spray gun [1] (b) Powder flame spraying. Powder flame spraying consists of a gun nozzle in which a mixture of oxygen and fuel such as acetylene or propane is injected. operates in much the same way as wire flame spray except that a powder feedstock material is used rather than wire and there is no atomizing air stream. The melted coating material is atomized and propelled to the surface in the stream of burning fuel gas. The powder is stored in either a gravity type hopper attached to the top of a spray gun or a larger air or inert gas entrainment type detached hopper. Powder flame spray guns are lighter and smaller than other types of thermal spray guns. Production rates for powder flame spray are generally less than for wire flame spray or arc spray. Particle velocities are lower for flame spray, and the applied coatings are generally less dense and not as adherent as those applied by other thermal spray methods. Workshop use of powder flame spray should be limited to repair of small areas of previously applied thermal spray coatings and galvanizing. Fig. 2-3 illustrates a typical combustion powder gun installation. Fig. 2-3. Powder flame spray gun [1] 2.1.2. HVOF spraying One of the newest methods of thermal spray, HVOF (High Velocity Oxygen Fuel), utilizes oxygen and a fuel gas at high pressure. Typical fuel gases are propane, propylene, and hydrogen. The burning gas mixture is accelerated to supersonic speeds, and a powdered feedstock is injected into the flame. The process minimizes thermal input and maximizes particle kinetic energy to produce coatings that are very dense, with low porosity and high bond strength. HVOF systems are field portable but are primarily used in fabrication shops. HVOF has been used extensively to apply wear resistant coatings for applications such as energy generating components. For example, an evaluation of HVOF-applied metal alloy coatings for protection against cavitation wear in hydro turbines. Fig. 2-4 shows cross section of HVOF gun. Fig. 2-4. HVOF gun [1] 2.2. Electric processes 2.2.1. Arc spraying Arc spraying is generally the most economical thermal spray method for applying corrosion resistant metal coatings, including zinc, aluminum, and their alloys. Energy costs are lower and production rates are higher than they are with competing methods such as wire flame spray. Arc spraying may be used to apply electrically conductive materials including metals, alloys, and metal-metal oxide mixtures. In arc spraying, an arc between two wires is used to melt the coating material. Compressed gas, usually air, is used to atomize and propel the molten material to the substrate. The two wires are continuously fed to the gun at a uniform speed. A low voltage (18 to 40 volts) direct current (DC) power supply is used, with one wire serving as the cathode and the other as the anode. Fig. 2-6 shows the components of a typical arc spray gun, including wire guides, gun housing, and gas nozzle. Coating quality and properties can be controlled by varying the atomization pressure, air nozzle shape, power, wire feed rate, traverse speed, and standoff distance. Arc sprayed coatings exhibit excellent adhesive and cohesive strength. Fig. 2-6. Arc spray gun 2.2.2. Plasma spraying Plasma Spraying is a Thermal Spraying Process that uses an arc as a heat source that ionizes an inert gas to melt a coating material which is finally propelled on to the substrate. A major advantage of spraying the material via the Plasma Spray Method is its ability to generate higher heats to melt ceramics as well as the ability to control how long the material dwells in the flame, ultimately allowing precise control over the final result. An arc is formed between an electrode and the spray nozzle, which acts as the second electrode. A pressurized inert gas is passed between the electrodes where it is heated to very high temperatures to form a plasma gas. Typical plasma spray gun is shown in Fig. 2-7. Powdered feedstock material is then introduced into the heated gas where it melts and is propelled to the substrate at a high velocity. A plasma spray system consists of a power supply, gas source, gun, and powder feeding mechanism. Plasma spraying is primarily performed in fabrication shops. The process may be used to apply thermal barrier materials, such as zirconia and alumina, and wear resistant coatings such as chromium oxide. Fig. 2-7. Plasma spray gun [1] 3 Thermal spray material and its application 3.1. Thermal Spray Material The final properties of a thermal spray coating are based on its microstructure properties, and these depend on both the material and the deposition method. Material properties can be affected by the manufacturing process, particle size, purity, and crystallographic structure and particle shape. These different can also influence application performance and final product price. The coating material may consist of a single element, but is often an alloy or composite with unique physical properties that are only achievable through the thermal spray process. Generally speaking thermal spray coatings are a highly cost-effective way to add superior performance qualities to a given substrate. Material may be classified according to several characteristics. Abradables provide cleareance control in high speed application in which near zero clearance between moving parts is required. Types of abradables include aluminum silicon-polyester, aluminum silicon-graphite, nickel graphite, nickel chromium aluminum-bentonite, aluminum bronze-polyester and MCrAlY-BN-polyester. Pure metals, alloys, and cermets provide surface enhancement, corrosion, oxidation, abrasion resistance, electrical resistance, and shielding. Types of material include, but are not limited to, copper, stainless steel, molybdenum, nickelaluminum, Inconel, MCrAlY, and blend of metal oxides such as alumina and chromium. Carbides improve surface hardness and add wear resistance. They include tungsten carbidecobalt, tungsten carbide-cobalt chromium, nickel chromium-chromium carbide, and blend of carbides and self-fluxing alloys. Ceramics produce textured surfaces that resist oxidation, abrasion, sliding wear, and high temperature corrosion, or that provide thermal insulation or electrical insulation. These include aluminum oxide, chromium oxide, titania, alumina-titania, and zirconium oxide stabilized with either calcia, magnesia, yttria, or ceria. Self-fluxing alloys and blends are fused metallurgically to bond with substrate. They form nonporous protective finishes resistant to abrasion, cavitation, fretting particle erosion, and corrosion. Nickel/cobalt chromium-boron-silicon-carbon alloys and carbide blends are examples of these types of material systems. Polymers are specified by their chemistry, morphology, molecular weight, melt-flow index, particle size, and heating/cooling (melting) characteristics. Thermoplastic amenable to thermal spraying are polyethylene (PE), PE copolymers, polyesters, nylon, fluoroplymers, etc. 3.2. Thermal spray application Many industries use thermal spray coatings to extend product life, increase performance, and reduce production and maintenance cost. Thermal spray coatings can be the most cost-effective means of protecting substrate surfaces from wear or corrosion. Other primary uses of thermal spray coatings include restoring dimensionality, maintaining precise clearances, and modifing thermal and electrical properties. The single most common use of thermal spray technology is to retard and control wear. Thermal spray coating are used to: alter the hardness and finish characteristics of countless mating surfaces, to minimize the effect of mechanical wear, and extend product life and reduce maintenance cost in a world of applications. Generally thermal spray coating have been using for : a. Protection againt wear b. Dimensional restoration c. Protection under thermal environment d. Protection from effects of liquids, gases, and particulate solids e. Protection againts corrosion f. Isolator or Conductor 4. Thermal spray in Indonesia: status and the future potential application in industry 4.1. Status The thermal spray processing market can be divided into two groups; one is the production by contract job shops, the other is that by the in-house production inside large enterprise. The thermal spraying output by the contract job shops are the all market size of the thermal spray industry in Indonesia. There are several job shops of thermal spray company where among of them are located in Jakarta, Bekasi. The wire arc spraying and flame spraying are the common thermal spray processing in the workshops. Accordingly the common thermal spray material to be used in the jobs is metallic for the application such as on the steel structure and machine parts. The ceramic material sometimes was applied by combustion flame spraying other than high investment cost of plasma spraying. The quality of the coatings was poor by this method due to low melting temperature and low particle velocity. So the processing of ceramic materials by flame spraying resulting low bond strength of coating. 4.2. The future potential application in industry There are many others potential application of thermal spraying in Indonesia which can be developed to aircraft, iron & steel, petroleum-chemical, anti-corrosion, machinery, light industry, textile, automotive, paper & printing, power, shipping and many other industries. The thermal spray industry in Indonesia could be developed in the following characteristics. a. Having large application areas and high level in certain fields, such as aircraft engine (cooperation with Boeing GE, PT, etc.), annealing furnace hearth roller, zinc pot roller (iron & steel), valve(petroleum chemical industry), drawn wire guide roller, cone pulley, drawn wire ring (textile industry), high-grade glass mould (light industry), valve piston (automobile industry),etc. b. Having wide range of process and materials. Almost all of the thermal spraying process and materials are available but some of them are not availaible, such as vacuum plasma, laser, vacuum fusion, cold spray, etc. c. Two thirds of the job shops are small and medium sized (less than 20 staffs in each unit), with an output of 75% of the total. For the rest are limited companies, private owned and collective companies, also a few foreign solely owned enterprises could be set up. d. Thermal spraying is commonly applied to maintenance. For the medium and small sized job shops, more than half of their jobs go to maintenance. e. The research institutes and universities will positively entered into market and the technical development for equipment and materials are mainly carried our by them. For example LIPI have been employing some research activity on thermal spray equipment and developing the next generation material [2-4]. Thermal spraying technology has been applied in some steel enterprises. However it has still not been used to its full potential in all steel enterprises. This high potential market has yet to be developed. The thermal spraying market in the steel industry is estimated at around U$ 23.2 M, within 5 years of which less than U$ 0.5 M have been developed only. The power industry has been a key industry developed by the Government over the last 10 years. The forecasted output of thermal spraying market in 5 years will reach to U$ 27.7 M. The coatings also applied to anilox print rolls, water rollers, cylinders etc. For example, for the high class anilox rollers (ceramic coating plus laser carving), the market demands increases every year. The product volume for water-transfer rollers of 50,000 parts/year is valued at U$ 66 M for non-coated parts. The market capacity for thermally sprayed coatings is estimated at U$ 83.3 M. In other industry such as textile, automobile, anti-corrosion, oil, gas and chemical, etc. have also quite large market potential capacity for thermally sprayed coatings, see Table.1. In the past five years, the thermal spray industry in Indonesia achieved more progresses. Indonesia economy is in recovery state since the crisis in 1998, GDP increasing by over 4 % yearly, and reached to approximately U$178 Billion in 2002. As the edge technology and junction of high technology industry and multi high-tech, thermal spray industry depends on and is sensitive to national economy especially to development of manufacturing and production restructure. In the other word, Indonesia thermal spray industry is faced with unprecedented opportunities such as in iron & steel, energy, automobile, paper & printing, anti-corrosion steel structure, textile, military industry and aerospace etc. Table 1. Thermal Spraying Market Estimated Growth Rate (%) Thermal Spraying (potential) Market (U$) 23.2 M Industry Output/year [5] Typical Parts Iron & Steel 3,499,657 ton 6.0 Power Paper & Printing 73,547,000 MWh 6,968,374 ton 3 14 6.27 27.7 M 83.3 M Textile Automobile Anti Corrosion 8221 million m 107,912 unit 280,220 ton 14.5 M 7 9M 2.2 M 3 sink roll, hearth roll, roll-table roll, mould for CCL, furnace nozzle, fan blade, etc boiler tubes, hydraulic cylinders, blades, fans, shafts, etc. Calender rolls, dry rolls, robbin winder rolls, anilox rolls, corrugating rolls, etc. godet rolls, grooved rolls, thread guides,etc. pistons, piston rings, brake disks, synchronizing rings, etc. bridges, tanks, highways, tubes, towers, etc. Oil, Gas and Chemical 1,914,639,000 m (gas); 432 million barrel (oil); 68,962,000 ton (chemical) 4,7 12.4 M MTM seals for ball, gate valves, (oil), 50 M etc. (chemical), 13.3 M (gas) 4.3. Comparing with status thermal spray in the world At present, output of thermal spray industry all over the world is about US$ 5 billion, and America shares US$ 2.12 billion, Japan shares US$ 0.83 billion, Germany shares US$ 0.5 billion, China shares US$ 0.14 billion (RMB 1.2 billion), Indonesia shares U$ 0.11 billion occupying respectively 0.21, 0.17, 0.25, 0.12, 0.06 in proportion to GDP. This displayed that both the absolute output and relative GDP proportion of Indonesia thermal spray industry are lower than developed countries especially than USA, Germany, Japan and China. The former showed that there is no large scale and high industrialization thermal spray industry in Indonesia, and the latter showed Indonesia thermal spray industry has not reached high technology level. The former attaches to the expansion of national economy scale especially the manufacturing scale, and the latter depends on production restructure and thermal spray industry self-optimization. As the same time, thermal spray industry is in possession of great developing space and excellent future. The domestic and foreign experiences proved that the more developed the country is, the more developed advanced manufacturing and thermal spray industry are, the thermal spray industry enterprises will enjoy better life. This is the arduous and glorious mission to all professionals among thermal spray industry field. "The ship rises with the tide", we are endowed with opportunity by history and undoubtedly people have the capability and duty to perform well in this field. References: 1. J. Stokes, "Theory and Application of Sulzer Metco High Velocity Oxy-Fuel (HVOF) Thermal Spray Process", Dublin City University (2008), ISBN 1-87232-753-2, ISSN 1649-8232 2. B. Prawara, G Pikra, Arini. 2008. Modeling dan Simulasi Pencampur Bahan Bakar (Mixer) Untuk Sistem HVOF Thermal Spray Coating, Pemaparan Hasil Penelitian Kedeputian IPT-LIPI, Bandung 3. B. Prawara, F. Afandi, Teknologi Pelapisan dengan Sistem HVOF dan Aplikasinya di Industri, Prosidin Seminar Nasional Tenaga Listrik dan Mekatronik, 27-29 Juli 2006, Bandung 4. Budi Prawara, Edy Riyanto, Rahmat, Rinto Suhendra, Andri Setiawan Perancangan dan Uji Coba High Velocity Oxygen Fuel Thermal Spray Coatings Prosiding Seminar Nasional Material dan Metalurgi-2, 20-21 Agustus 2008 Bandung, ISSN : 1978-6352, A11-09 5. Pusdata Depperin, National Production Capacities ...
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This note was uploaded on 03/17/2010 for the course ME ME78212 taught by Professor Prof.sulis during the Spring '10 term at Institut Teknologi Bandung.

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