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Proceedings Papers
ITSC 2011, Thermal Spray 2011: Proceedings from the International Thermal Spray Conference, 985-990, September 27–29, 2011,
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Thermal sprayed ceramic coatings are well used as the electrode of corona discharge treatment in order to modify the surface of many kinds of films and papers due to its superior durability and adaptability. Some kinds of Al 2 O 3 -TiO 2 were sprayed by APS on the parallel plate electrodes, and output power of corona discharge generated by the electrodes was measured by using Sawyer-Tower circuit. In addition, discharge output power was calculated with an equivalent circuit of corona discharge. By comparing them, effects of the electrical property of the coating on discharge was researched. As a result, the electrostatic capacitance of the coatings influences the impedance of the whole circuit, and higher relative permittivity of the coating brought higher output power in a constant voltage.
Proceedings Papers
ITSC 2011, Thermal Spray 2011: Proceedings from the International Thermal Spray Conference, 1017-1020, September 27–29, 2011,
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New concept and method of testing for the interconnecting porosity of thermally sprayed nonconductive ceramic coatings is proposed. This process is useful to differentiate the open porosity from the closed porosity. Thermally sprayed ceramic coating with metallic substrate is plated, and the intergranular gaps in the coating are filled by deposited metal. Typically, 304 stainless steel substrate deposited with atmospheric plasma sprayed alumina coating is immersed in copper(II) sulphate bath, and electroplated. Inward of the alumina coating, plating solution penetrates toward the interface of coating/substrate via interconnected porosity, and attains the coating-substrate interface to deposit metallic copper. Deposit of copper is gradually grown up along the coating intergranular. The exposure of deposited copper on the coating surface can be visible. Because these phenomena occur only in the interconnected pore structure, it is easy to differentiate the interconnected porosity from the closed porosity. Also the proposed process suggests the unprecedented possibility of manufacturing method of three-dimensional structure of thermally sprayed ceramic coating.
Proceedings Papers
ITSC 2011, Thermal Spray 2011: Proceedings from the International Thermal Spray Conference, 15-19, September 27–29, 2011,
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Trends of thermal spraying technology in Japanese steel industry is summarized by investigating the patent applications filed in Japan Patent Office in the past 20 years from FY1990 to FY2009. The total number of patents filed in 8 Patent Offices (Japan, United States, Europe, China, Korea, Russia, Brazil and India), retrieved by the International Patent Classification symbol C23C4/00 (IPC index key: Coating by spraying the coating material in the molten state ), is 15,082. The ratio of patent applications filed in each Patent Office is as follows: JP (39%), US (22%), EP (17%), CN (9%), KR (6%), RU (3%), BR (3%) and IN (1%). The database used in this study is from commercially available “PatBase”. Number of patent applications of thermal spray technology (C23C4/00) in Japan is 4,369. Among these patents, the ratio of patents related to steel industry filed by major Japanese steel companies is 13% of total patents of every industrial segment in Japan. These patents are classified according to (1) coating applications in the process of steel production lines, (2) performances and effects obtained by coatings, .and (3) coating materials. In this paper, current status and future trend of thermal spray technology in Japanese steel industry is discussed.
Proceedings Papers
ITSC 2011, Thermal Spray 2011: Proceedings from the International Thermal Spray Conference, 218-223, September 27–29, 2011,
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The corrosion behavior of thermally sprayed Al-Zn alloy coatings immersed in NaCl aqueous solution was determined by using electrochemical impedance spectroscopy. Ohmic resistance and capacitance of the corrosion product film formed on the sprayed coating surface, and the corrosion resistance and electric double layer capacitance at the interface between the sprayed coating and the solution were evaluated. As immersion time in NaCl solution increased, the corrosion rate of the Al-2mass%Zn coating increased, but the corrosion rate for Al-6mass%Zn and Al-15mass%Zn coatings decreased due to the influence of the corrosion product.
Proceedings Papers
ITSC 2010, Thermal Spray 2010: Proceedings from the International Thermal Spray Conference, 183-188, May 3–5, 2010,
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Damage of marine screw propeller parts made of aluminum bronze cast material caused by cavitation erosion is one of the serious problems. Erosion resistant thermal spray coating on aluminum-bronze material is expected to extend lifetime of such propellers. In this study, Cobalt-based alloy coatings sprayed by; (a) atmospheric plasma spraying (APS), (b) low pressure plasma spraying (LPPS) and (c) high velocity oxy-fuel (HVOF) spraying and aluminum bronze cast material were evaluated by cavitation erosion test using magnetostrictive cavitation test equipment. Fracture morphology of cavitation eroded coating surfaces were analyzed by surface observations with SEM and also the amount of volume loss was measured. Cobalt-based alloy coatings sprayed by LPPS exhibited superior cavitation erosion resistance compared to aluminum bronze cast material and coatings by APS and HVOF. Moreover, mechanical properties of Cobalt-based alloy coatings were investigated in detail by nanoindentation technique. It is found that cavitation erosion resistance of coatings is subjected to interparticle cohesive strength.
Proceedings Papers
ITSC 2007, Thermal Spray 2007: Proceedings from the International Thermal Spray Conference, 977-982, May 14–16, 2007,
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Mechanical properties of thermal-sprayed ceramic coatings were investigated. Al 2 O 3 and Y 2 O 3 -stabilized ZrO 2 (YSZ) coatings were deposited on plate substrates. Stainless steel plates and aluminum plates, of different thermal expansion coefficients, were used as substrates. The coatings were prepared at two different thicknesses. During deposition of each sample, the history of substrate temperature was recorded. Four-point bending tests were carried out, while strains at the coating surface and the substrate surface were measured with strain gages. The apparent Young's modulus of the coating was determined using the composite beam theory. In addition, the rupture strain of the coating was measured by three-point bending test. The relationship between the results of these tests and the temperature of each substrate during deposition is discussed.
Proceedings Papers
ITSC 2007, Thermal Spray 2007: Proceedings from the International Thermal Spray Conference, 324-328, May 14–16, 2007,
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Thermal spray technology trends in Japan were studied on the basis of patent information related to such technologies in Japan. Information related to research in and the basic development of thermal spray and allied coating technologies can be found in publication papers or documents submitted to national or international conferences, symposiums academic journals and so on. However, this kind of information does not always disclose key fundamentals pertinent to the industry in question. The present status of thermal spray technology and related future trends in Japan are described in this paper based on an investigating of patent filings, claims, and the specific industrial fields and applications related to such patent applicants.
Proceedings Papers
ITSC 2006, Thermal Spray 2006: Proceedings from the International Thermal Spray Conference, 797-802, May 15–18, 2006,
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In plasma spraying, generally, powders are radially injected into plasma jet. However, percentage of particles which have enough enthalpy to melt is not high in radial injection, possibly leading to low deposit efficiency especially for high melting point powders. In this research, powder port for radial injection was attached to an axial injection plasma torch in order to compare the plasma flame in both cases of axial and radial powder injections. The powder trajectory and the shape of the plasma plume were observed, and particle flux density, temperature, velocity, and deposit efficiency of alumina powders were measured and the results were compared between the two powder injection methods.
Proceedings Papers
ITSC 2005, Thermal Spray 2005: Proceedings from the International Thermal Spray Conference, 1393-1396, May 2–4, 2005,
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Generally, the surface of a substrate is roughened by blasting in pretreatment thermal spraying. Since some of the grit remains on the substrate surface, sprayed coating and the adhesion property characteristics are degraded. However, it seems that there is almost no research on this problem. In this study, residual grit is quantitatively evaluated, and a technique for reducing grit is proposed. For residual grit reduction, a solid lubricant was used, and applied to the surface of a substrate or grit; reduction of residual grit was confirmed. After blasting with solid lubricant, it remained on the substrate surface, which could be removed by heating the substrate.
Proceedings Papers
ITSC 2004, Thermal Spray 2004: Proceedings from the International Thermal Spray Conference, 918-921, May 10–12, 2004,
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The high temperature oxidation resistance behavior of atmospheric plasma sprayed CoNiCrAlY coating with a thin layer of Cr 2 O 3 employing chromate treatment was investigated. The high-temperature oxidation test was performed at 1423K for 7.2, 14.4 and 32.4ks, respectively. The formation of the oxide layer on the CoNiCrAlY coatings with Cr 2 O 3 thin layer by chromate treatment was compared with that of the non-Cr 2 O 3 thin layer. The oxide layer formed on the both types of MCrAlY coatings grows with increasing the elevated temperature and the holding time. Also, the thickness of the oxide layers was proportional to the square root of time. The thickness of the oxide layer on CoNiCrAlY coatings with the thin layer of Cr 2 O 3 was only 60% as compared with that of the non-Cr 2 O 3 thin layer in high temperature oxidation tests at 1423K.
Proceedings Papers
ITSC 2001, Thermal Spray 2001: Proceedings from the International Thermal Spray Conference, 1085-1088, May 28–30, 2001,
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Thermally sprayed coatings with Co-based alloy were evaluated for cavitation erosion resistance in order to use as erosion proof coatings. Co-based alloy coatings have been applied by Low Pressure Plasma Spray (LPS) and High Velocity Oxygen Fuel Flame Spray (HVOF) on the AISI 403 stainless steel substrates and half number of each coated specimen were post-heated at 1073K for 1 hour. The mass loss was measured for evaluation in this study. The following results have been obtained in the cavitation test; i) Both of LPS coatings (the post-heated and the as sprayed) have more excellent cavitation erosion resistance than HVOF coatings, ii) With regard to LPS coatings, the post-heated coating has the same weight loss as the as-sprayed coatings. iii)The post heat treatment to HVOF is remarkably effective to improve the cavitation erosion resistance.
Proceedings Papers
ITSC 2001, Thermal Spray 2001: Proceedings from the International Thermal Spray Conference, 195-198, May 28–30, 2001,
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The gas turbine blades in a severe environment are overlaid with MCrAlY coatings by Low Pressure Plasma Spray (LPS) process for protection against hot corrosion. However, the service life of each blade is limited by damage due to embrittlement layer, which is formed by reaction diffusion at the interface between the coating and the substrate. Reaction diffusion behavior between the CoNiCrAlY coatings and substrates was investigated. In addition, high-temperature oxidation behavior of the CoNiCrAlY coating by LPS was evaluated. The CoNiCrAlY coatings for reaction diffusion test were carried out by 3 kinds of spray process (LPS, High Velocity Oxygen Fuel Spray: HVOF, Atmospheric Plasma Spray: APS) on 2 kinds of substrate (Directional Solidification and Single Crystal Ni-based super alloys). It has been found that the CoNiCrAlY coating by APS inhibited the reaction diffusion at the boundary of the coating and the base material as compared with LPS coating. It was also confirmed that the protective dense layer of aluminum oxide against hot corrosion was formed in the surface of the CoNiCrAlY coatings by LPS.
Proceedings Papers
ITSC 2001, Thermal Spray 2001: Proceedings from the International Thermal Spray Conference, 699-704, May 28–30, 2001,
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Hardness and microstructure of Cr 3 C 2 -NiCr coating formed by vacuum plasma spraying process (VPS coating) were investigated in compare with that formed by High Velocity Oxygen Fuel Spraying process (HVOF coating). The results are as follows. (1) The hardness of VPS coatings in as sprayed condition was HV1243 ± 80, which was much higher than that of HVOF coatings, HV958±44, and never went down under HV1100 even after heat treatment at 1273K for 3.6ks. (2) VPS coating presents dense lameller structures composed of Cr 2 C 3 , Cr 7 C 3 and γ-NiCr phase, while HVOF coating presents lameller structures with many fine gaps, composed of Cr 2 C 3 , Cr 7 C 3 , γ-NiCr phase and relatively large amounts of Cr 2 O 3 . (3) The reason why such high hardness was obtained in VPS coating, has been considered due to their dense lamella structures.
Proceedings Papers
ITSC2000, Thermal Spray 2000: Proceedings from the International Thermal Spray Conference, 1025-1031, May 8–11, 2000,
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The work reported herein deals with the interaction among the thermally sprayed coatings and steel substrate in acid aqueous solutions investigated by using the electrochemical process. Thermally sprayed coatings on steel substrate for such as the tribological applications except for the sacrificial anode property have been extended. The environment of these machinery components is often utilized accompanied with the aqueous solutions. The galvanic corrosion occurred in aqueous solutions among the metals or alloys have been well known. In the actual spray process, the formation of penetrated pores or crevice defects are not generally avoided. In the aqueous solution environment, the penetrated defects cause the galvanic corrosion between coating and steel substrate, and tend to be occurred the coating spalling. In this work, the electrochemical process was employed to determine the corrosion phenomena. The preferable combination of sprayed coatings and steel substrate are discussed and the examples of design of the intermediate layers are proposed.
Proceedings Papers
ITSC1998, Thermal Spray 1998: Proceedings from the International Thermal Spray Conference, 481-487, May 25–29, 1998,
Abstract
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The structure and morphology of plasma sprayed splats are experimentally investigated using different droplet materials and substrate materials. Droplet materials include aluminum, copper, nickel and refractory metals such as molybdenum and tungsten, and substrate materials include aluminum, stainless steel, and molybdenum plates. The results show that the splashing occurs during the splatting of a completely molten droplet. Most splats formed by droplets molten completely are only central part of the ideal disk type ones, which are defined as the annulus-ringed disk-like splat. It is found that the morphology of such annulus-ringed disk-like splat is greatly influenced by the combination of droplet and substrate materials depending on whether substrate melting occurs. With the combinations of droplet and substrate materials which are of similar thermal properties the splashing of central area of splat tends to occur to present a honeycomb structure at the center of splat. When droplet impacting can cause melting of substrate annulus-ringed splat prefers to present a split type. The flattening ratio of an annulus-ringed disk splat is typically less than 2.
Proceedings Papers
ITSC1998, Thermal Spray 1998: Proceedings from the International Thermal Spray Conference, 951-956, May 25–29, 1998,
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The unusual effects of plasma sprayed coating on the fire-side of evaporator tubes located in an oil-fired steam generating boiler are discussed. The main heat transfer surfaces are constructed by heat exchanger tubes, evaporator tubes and superheaters. Maintenance to prevent of the boiler failure or the preserve heat exchanger effectiveness is a very important factor in the operation of boiler facilities. In a boiler which employs heavy gravity oil as a fuel, plasma sprayed Ni-Cr alloy has often been applied to boiler tubes for the relief of hot corrosion by combustion gas. However, the circulation of boiler water causes an internal deposit to form on the inner wall of evaporator tubes. The internal deposit generates excess heat load against the tubes. As the overheating of the tubes often causes the evaporator tubes to fail, they are chemically cleaned periodically. In this paper, the influence of Ni-Cr plasma sprayed coating for the heat flux, which dominates the formation of the internal deposit, is investigated. Ni-Cr plasma sprayed coating is substitutionally hot corrosion resistant and is a composite coating into which the fuel ash containing a vanadium or sulfur compound are interstitially penetrated and solidified. It is derived that the existence of the coating on the fire-side of the evaporator tubes normalizes the heat load in their inner walls. Moreover, the suppression of internal deposit formation decreases the frequency of chemical cleaning for tubes. The dual effects of plasma sprayed coating for hot corrosion resistance in the fire side and the suppression of internal deposit on the water side of the tubes are reported.
Proceedings Papers
ITSC1998, Thermal Spray 1998: Proceedings from the International Thermal Spray Conference, 1097-1102, May 25–29, 1998,
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Some applications of high velocity oxygen fuel (HVOF) flame sprayed WC cermet coatings in paper mills are summarized. The WC cermet sprayed coating is one of the most widely used in the thermal spray industry. HVOF sprayed WC cermet coatings have such excellent physical and chemical properties that they are extensively employed in the industrial field. Typical properties for example, are wear resistance, high stress rotating bending or rolling contact fatigue strength, frictional characteristics, wettability for aqueous agent, non picking or non adhesive property against foreign material, thermal conductivity, mirror finished surface property and so on. They are derived from the compact, denser microstructure, containing fine-sized hard WC particles, high bond strength onto substrate. These characteristics obtained by HVOF sprayed WC cermet coatings are utilized to improve the surface functions of machine parts which are installed mainly in the press department, drying department, size press, calender department and finishing department of paper mills. In this study, examples of some application of WC cermet coatings in several types of rolls in paper mills are introduced.