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T. Mantyla
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Proceedings Papers
ITSC 2007, Thermal Spray 2007: Proceedings from the International Thermal Spray Conference, 1099-1104, May 14–16, 2007,
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Hot corrosion tests have been conducted on Ni- and Cr-based laser coatings, a high-velocity oxy-fuel (HVOF) sprayed coating and various wrought alloys covered with a synthetic salt of Na 2 SO 4 -V 2 O 5 and exposed at 650°C for 1000 h in air. Coating microstructures and reaction product layers were analyzed with scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The hot corrosion resistance of tested specimen was evaluated by measuring its mean thickness loss. Generally, wrought alloys, HVOF coating and Cr-based laser coatings suffered from selective corrosion beneath salt film, that is, distinct Cr-depleted layer was formed at alloy/salt interface. Cr-based laser coatings exhibited extended solid solubility and they transformed towards equilibrium condition. Cr-rich phases enriched further with Cr and they were prone to corrosion. Low diluted laser coatings and HVOF coating were more resistant to hot corrosion than commonly used industrial standard alloy, Nimonic 80A. Ni-based laser coating exhibited resistance equivalent to Cr-based coatings and superior to corresponding wrought alloy.
Proceedings Papers
ITSC 2006, Thermal Spray 2006: Proceedings from the International Thermal Spray Conference, 1189-1192, May 15–18, 2006,
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High power diode lasers (HPDL) at the level of ? 6 kW are efficient cladding tools in heavy engineering applications where thick (up to 5 mm) wear and corrosion resistant coating layers are required. Large beam geometry makes possible the overlap of thick 20 mm wide cladding tracks side by side without coating defects. Compact size and closed cooling water circulation enable HPDL cladding process to take place also at a site of new or worn high-value machine parts, which have worn in operation or been damaged already during overseas transportation. Instead of moving parts of several tons’ weight, it would be perhaps more cost efficient to transport HPDL cladding unit.
Proceedings Papers
ITSC 2005, Thermal Spray 2005: Proceedings from the International Thermal Spray Conference, 580-584, May 2–4, 2005,
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Plasma sprayed oxide coatings are widely used in applications where the surface properties of the coatings dictate the performance of the coating. The knowledge of chemical surface properties of plasma sprayed oxide coatings is very limited and to our knowledge surface chemical studies of these coatings have not been published. Surface properties of common plasma sprayed oxide coatings exposed to water based electrolytes were evaluated using several surface sensitive techniques such as X-ray photoelectron spectroscopy (XPS) and electrophoretic mobility studies. The dissolution behaviour of the coating materials were studied using inductively coupled plasma-mass spectroscopy (ICP-MS). Other characterization techniques included X-ray diffraction (XRD) and scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS). The correlation between chemical stability, bulk and surface properties of the coatings were evaluated. Obtained results are compared with published values of traditionally manufactured oxide counterparts.
Proceedings Papers
ITSC 2004, Thermal Spray 2004: Proceedings from the International Thermal Spray Conference, 1046-1051, May 10–12, 2004,
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Thermally sprayed hard coatings, including tungsten carbide and chromium carbide cermets and other hard metallic materials, were studied in two types of wear tests. Surfaces of the coatings were worn by coarse and hard quartz sand in a rubber-wheel dry abrasion wear test, and by fine and soft kaolin abrasive in a wet slurry abrasion wear test. The aim of the work was to study how the surfaces retain their high polished finish and gloss, and the type of wearing of different coatings and materials. The results showed that coatings with hard tungsten carbides were worn preferentially by removal of the the binder material. Cermet coatings with softer chromium carbides, and with another types of uniform microstructures showed more uniform wear and better retained their glossy finish.
Proceedings Papers
ITSC 2003, Thermal Spray 2003: Proceedings from the International Thermal Spray Conference, 233-236, May 5–8, 2003,
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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 Al 2 O 3 , Cr 2 O 3 and TiO 2 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.
Proceedings Papers
ITSC 2003, Thermal Spray 2003: Proceedings from the International Thermal Spray Conference, 243-248, May 5–8, 2003,
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In this work, HVOF sprayed hard metal multi-component Cr 3 C 2 -25Ni+10 vol-% solid lubricant coatings were prepared by HVOF spraying. CaF 2 , BN, MnS and WS 2 were used as solid lubricants. Powders were prepared by the spray drying and sintering method. This method produces homogeneous and spherical powders. Powders were sprayed with DJH 2600 HVOF-system. Microstructures, phase structures and compositions of powders and coatings were analysed with optical microscope, scanning electron microscope with EDS-analysator and x-ray diffractometer. The particle size distributions of sintered powders were determined by laser diffractometer. The amount of retained solid lubricant in the sprayed coatings was evaluated by EDS and compared to that in the spray powder. This study showed that spray drying and sintering method is a preferable method for manufacturing multi-component solid lubricant containing thermal spray powders. In sintering processes, solid lubricant phases remained in powders except for the Cr 3 C 2 -25Ni+10vol-%WS 2 -powder. Also, after HVOF spraying, coatings contained solid lubricants.
Proceedings Papers
ITSC 2003, Thermal Spray 2003: Proceedings from the International Thermal Spray Conference, 485-494, May 5–8, 2003,
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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.
Proceedings Papers
ITSC 2003, Thermal Spray 2003: Proceedings from the International Thermal Spray Conference, 617-622, May 5–8, 2003,
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Plasma sprayed ceramic coatings have much lower stiffness in comparison to sintered ceramics. The reason for that is their characteristic microstructure with porosity and microcracks. Microcracks decrease the interlamellar cohesion in vertical direction, but also affect the individual splat properties in the horizontal direction. For that reason sealing treatments are often applied with plasma sprayed ceramic coatings in order to improve their corrosion resistance and mechanical properties. In this paper the effect of aluminum phosphate sealing treatment on the elastic properties of plasma sprayed Al 2 O 3 and Cr 2 O 3 coatings were studied. Residual stresses in the plane of coating surfaces were compared using the X-ray diffraction analysis (XRD). A special four point bending device, designed for the X-ray diffractometer, was used in determining the effect of additional load on coating elastic behavior. In as-sprayed alumina coatings tensile stresses of about 400 MPa were detected while only about 40 MPa of compressive stresses were measured in the as-sprayed chromia coatings. Microstructural characterization revealed that sealing treatment had apparently affected the coating microstructure and filled some microcracks and interlamellar spacings. As a result, in both sealed coatings, compressive stresses of about 100 up to 150 MPa were observed. Also a better stiffness of both materials was detected during the bending of specimens. In addition, the sealing treatment increased nearly ten times the Young’s modulus, determined by XRD analysis under various tensile loads.
Proceedings Papers
ITSC 2003, Thermal Spray 2003: Proceedings from the International Thermal Spray Conference, 1213-1220, May 5–8, 2003,
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The objective of this study is to increase the deposition rate in the plasma-spray manufacturing of thermal barrier coatings without altering the quality of the coatings. The experimental part involves the measurement of in-flight particle characteristics and analysis of coatings properties when varying the hydrogen content of the plasma-forming gas, the torch nozzle diameter and the powder feed rate. The experimental results of particle measurements are discussed in the light of the gas flow fields projected by a 3-D model of the plasma spray process.
Proceedings Papers
ITSC 2003, Thermal Spray 2003: Proceedings from the International Thermal Spray Conference, 1307-1310, May 5–8, 2003,
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By modification of parameters in plasma spraying it is possible to alter porosity of the deposits only in a relatively small range. Industrial applications may require to adjust the porosity in wider range, to double or triple the original value in some cases. Such changes can be achieved only by special procedures. One of them is plasma spraying of ceramic/metal deposit followed by removal of the metal within the coating. The material removal is performed by dissolving, by leaching or by its extraction with an appropriate process. The paper describes preparation of very porous Cr 2 O 3 coatings by this method from a composite Cr 2 O 3 /Al deposit. The initial porosity of approximately 13% (total porosity) was increased to 37% or 51% respectively by changing the initial volume of aluminum in the ceramic/metal plasma-sprayed composite. The discussion is complemented by observation of the resulting coating structure and detailed characterizations of the pore structure and porosity.
Proceedings Papers
ITSC 2003, Thermal Spray 2003: Proceedings from the International Thermal Spray Conference, 1477-1486, May 5–8, 2003,
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In gas turbines and diesel engines there is a demand for Thick Thermal Barrier Coatings (TTBCs), because of the increased process combustion temperatures. Unfortunately the increased thickness of plasma sprayed TBCs normally leads to a reduced coating lifetime. So for that reason the coating structures have to be modified. When modifying the structure of TTBCs, the focus is normally set on elastic modulus reduction of the thick coating, in order to improve the coating strain tolerance. On the other hand, coating structural modification procedures, such as sealing treatments, can be performed when increased hot corrosion resistance or better mechanical properties are needed. In this paper we introduced several modified zirconia based TTBC structures and their specific microstructural properties. Coating surface sealing procedures such as phosphate sealing, laser-glazing and sol-gel impregnation were studied as potential methods in increasing the hot corrosion and erosion resistance of TTBCs. Some microstructural modifications were also made by introducing segmentation cracks into the coating structures by laserglazing and by using special spraying parameters. These last two methods were studied in order to increase the strain tolerance of TTBCs. The coating microstructures were characterized by optical microscopy, SEM, TEM, EDS analysis and X-ray diffraction. The effect of sealing procedures was studied on basic thermal and mechanical properties of the coatings. In the paper it was also presented some correlations between the coating properties and microstructures, and discussed about the advantages and drawbacks of each modification procedure.
Proceedings Papers
ITSC 2003, Thermal Spray 2003: Proceedings from the International Thermal Spray Conference, 1693-1702, May 5–8, 2003,
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Several polymeric coatings, including flame sprayed polyethylene (PE), were evaluated for use in parts of natural gas pipelines. The components of interest were for instance large valves, T-joints, weld joints of pipes and pipe bends. More than 30 different coatings were selected to laboratory scale testing and evaluation. After first preliminary tests, the most potential coatings were selected further for more detailed and long term laboratory scale studies. After these tests were finished, one coating concept, i.e. fusion bonded epoxy (FBE) + flame sprayed PE, was prepared on a small natural gas valve body for demonstration purposes. Besides this coating concept, also some other coatings, e.g. liquid epoxy + flame sprayed PE and some polyurethane coatings were found to be potential coatings for the application. The test methods and results are presented in this paper.
Proceedings Papers
ITSC 2002, Thermal Spray 2002: Proceedings from the International Thermal Spray Conference, 676-680, March 4–6, 2002,
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This paper describes the production of self-lubricating chromium carbide-nickel coatings using the HVOF spraying process. The present work deals with the preparation of Cr 3 C 2 -Ni + CaF 2 multicomponent powders and to spray them with a minimum loss of the CaF 2 solid lubricating phase. The powders are processed by atomization with subsequent sintering and qualification processes. The microstructure of the powder and resulting layers is characterized by SEM. The content of calcium fluoride in the sprayed layer is determined using the EDS method and compared with its content in the spray powder. Wear resistance is measured using a rubber wheel tester. Paper includes a German-language abstract.
Proceedings Papers
ITSC 2002, Thermal Spray 2002: Proceedings from the International Thermal Spray Conference, 727-732, March 4–6, 2002,
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This paper provides a short summary of the information that can be found in the literature on the preparation and structure of titanium carbide (TiC) wettable powders. From the work that has been done, it can be concluded that TiC-based coatings can be tailored for applications where complex stress profiles are encountered. Paper includes a German-language abstract.
Proceedings Papers
ITSC 2002, Thermal Spray 2002: Proceedings from the International Thermal Spray Conference, 755-759, March 4–6, 2002,
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The main focus of this study is sealed zirconia-based thermal barrier coatings produced by plasma spraying. AEM examinations conducted on phosphate-sealed Y 2 O 3 -ZrO 2 coatings and orthophosphoric acid sealed MgO-ZrO 2 coatings provide detailed information on the phases in the sealed coatings and the bonding mechanism of phosphate-based sealants on zirconia. In the case of aluminum phosphate sealed alumina and chromia, the primary objective is to add clarity on the bonding mechanism by means of transmission electron microscopy. Investigations of the sealing-layer interface indicate that the sealing of the layer lamellas is due to chemical reactions. Paper includes a German-language abstract.
Proceedings Papers
ITSC 2002, Thermal Spray 2002: Proceedings from the International Thermal Spray Conference, 905-907, March 4–6, 2002,
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In this study, Cr 3 C 2 +25NiCr hardmetal powder is mixed with small amounts of NiCr and CoCr powder and sprayed on steel substrates with a high-velocity oxyfuel torch. High-temperature friction tests are used to assess tribological performance and investigate the formation of tribolayers. The results of the study show that the friction coefficient of HVOF sprayed hardmetal coatings can be reduced by adding small amounts of low-friction powder to the feed stocks prior to spraying. The reduction in friction is the result of a tribochemical reaction that occurs on friction surfaces under contact conditions involving high temperature, pressure, and sliding speed. Paper includes a German-language abstract.
Proceedings Papers
ITSC 2002, Thermal Spray 2002: Proceedings from the International Thermal Spray Conference, 908-911, March 4–6, 2002,
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This paper examines plasma-sprayed alumina and chromia coatings, with and without aluminum phosphate sealing, in order to assess the stability of the as-sprayed layers and phosphate reaction as a function of temperature during the sealing process. Thermogravimetric analysis showed no changes in mass in the alumina layers, an increase of 1.7% in the mass of the chromia layers due to oxidation, and a 14% loss of mass in the sealed layers, which agrees well with the evaporation behavior of a pure seal. Paper includes a German-language abstract.
Proceedings Papers
ITSC 2002, Thermal Spray 2002: Proceedings from the International Thermal Spray Conference, 196-201, March 4–6, 2002,
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This paper discusses the development of a two-layer thermal barrier coating that reduces heat flow to the lowest allowable level based on the temperature limits of the materials involved. The thick, porous coating was sprayed using a modified plasma torch and then thermally cycled until failure. Test results show that the process used to apply the bond coat has a measurable effect on the performance of the thermal barrier coatings. In addition to zirconia powders, a low cost polymer powder was used as well. Paper includes a German-language abstract.
Proceedings Papers
ITSC 2002, Thermal Spray 2002: Proceedings from the International Thermal Spray Conference, 208-212, March 4–6, 2002,
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This paper demonstrates the use of an articulated robot in a plasma spraying operation for gas turbine transition ducts. A 3D model of the coating cell and workpiece plays a key role in the application, facilitating off-line programming and the verification of process parameters prior to spraying. In the spray experiments, a YSZ coating was applied to a NiCr bondcoat and subsequently characterized based on microstructure and hardness. The results were then used to set the injection parameters and travel path for the actual component. Paper includes a German-language abstract.
Proceedings Papers
ITSC 2002, Thermal Spray 2002: Proceedings from the International Thermal Spray Conference, 470-475, March 4–6, 2002,
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HVOF spraying is used to produce NiCoCrAlYRe deposits that serve as adhesive layers for plasma-sprayed thermal barrier coatings. This paper investigates the influence of HVOF spray parameters on the structure and properties of the adhesion-promoting layers. Spray parameters are optimized to produce high layer densities with low degrees of oxidation and a surface roughness comparable to that of the thermal barrier coatings. A vacuum-sprayed layer with similar composition is also examined. Following the application of the TBC, the oxidized layers are characterized based on microstructure, oxide layer thickness, proportion of the NiAl phase, and imperfections at the boundary layer. It is observed that the less expensive HVOF layer offers the same protective properties as a vacuum plasma sprayed bond coat. Paper includes a German-language abstract.
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