Browsing by Author "Fagoaga, I."
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Item Behavior of Austempered Ductile Irons (ADI) Subjected to Laser Surface Melting(1989-03-24) Jones, D. L.; Fagoaga, I.; Liceaga, J. F.; EXTREMAT; Centros PRE-FUSION TECNALIA - (FORMER)The near surface microstructure of 3 austempered ductile irons has been modified using laser surface melting (LSM). A white cast iron layer was produced to depths of up to 500 microns. The microstructure of this region varied depending upon the parameters used. A heat affected zone (HAZ) appeared at an abrupt transition between the LSM zone and the substrate. The size of the HAZ, which varied between 20 and 200 microns was predominately affected by the pass velocity in the range of energies used. The hardness profiles showed large variations in the Haz probably due to varing tempering effects from the subsequent passes.Item Erosion protection of carbon-epoxy composites by plasma-sprayed coatings(1991-12-10) Alonso, F.; Fagoaga, I.; Oregui, P.; Centros PRE-FUSION TECNALIA - (FORMER); EXTREMATThis paper deals with the production of plasma-sprayed erosion-resistant coatings on carbon-fibre-epoxy composites, and the study of their erosion behaviour. The heat sensitivity of the composite substrate requires a specific spraying procedure in order to avoid its degradation. In addition, several bonding layers were studied to allow spraying of the protective coatings. Two different functional coatings were sprayed onto an aluminium-glass bonding layer, a WC-12Co cermet and an Al2O3 ceramic oxide. The microstructure and properties of these coatings were studied and their erosion behaviour determined experimentally in an erosion-testing device.Item High velocity spray deposition of WC cermets by an air-oxygen controlled combustion process(ASM International, 2016) Parco, M.; Fagoaga, I.; Barykin, G.; Vaquero, C.; EXTREMATHVOF processes represent the state of art for the spray deposition of wear and corrosion resistant coatings since their supersonic gas velocities in combination with moderate flame temperatures allow the deposition of optimal coatings with very high bond strengths, fine surface finishes and low oxide levels. However, new generation coating materials (fine powders), stringent quality requirements and the high productivity demanded by the industry, push the HVOF technologies to their limits. Recently, a novel air-oxygen controlled high velocity combustion process has been development by Tecnalia. The system operates within the supersonic regime using a broad range of fuel/oxidant ratios thanks to the use of air-oxygen mixtures and a carefully designed gun. Extremely low flame temperatures can be achieved while keeping a supersonic flow of combustion products, thus allowing the solid state deposition of almost all industrially relevant metal alloys with superior deposit qualities. This work deals with the development of superhard cermet coatings using different types of conventional and fine WC-Co(Cr) powders. The process parameters and the system configuration have been optimised looking for the best coating properties and microstructure. Results are compared in terms of ascertained coating properties (microstructure, microhardness and toughness) and the functional performance under sliding wear.Item Hydroxyapatite coating on titanium by a low energy plasma spraying mini-gun(2012-01-15) Demnati, I.; Parco, M.; Grossin, D.; Fagoaga, I.; Drouet, C.; Barykin, G.; Combes, C.; Braceras, I.; Goncalves, S.; Rey, C.; EXTREMAT; INGENIERÍA DE SUPERFICIESPlasma-sprayed hydroxyapatite (HA) coatings are used on metallic implants to improve osseointegration and bone growth. The purpose of this work was to determine the microstructure and composition of HA coatings obtained with a newly developed low energy plasma spray mini-gun employing an HA feedstock powder with smaller granulometry than that commonly used. The microstructure and the phase composition of the coatings obtained by varying the number of mini-gun runs were examined using scanning electron microscopy, X-ray diffraction and Fourier transform infrared and micro-Raman spectroscopy. In all cases, the results indicate the presence of an amorphous phase and oxyapatite in the coatings due to hydroxyl group removal. No other foreign crystalline phases were detected. The absence of foreign phases was attributed to the fast cooling rate of the small particles used in the experiments and the low amount of energy employed with the mini-gun. Decomposition in the υ1PO4 region of the Raman spectra allowed a semi-quantitative evaluation of the phase contents as a function of the number of runs. Micro-Raman spectroscopy appears to be a powerful technique providing comprehensive and localised information concerning calcium phosphate phases in coatings.Item Liquid-solid self-lubricated coatings(2013-02) Armada, S.; Schmid, R.; Equey, S.; Fagoaga, I.; Espallargas, N.; EXTREMATSelf-lubricated coatings have been a major topic of interest in thermal spray in the last decades. Self-lubricated coatings obtained by thermal spray are exclusively based on solid lubricants (PTFE, h-BN, graphite, MoS 2, etc.) embedded in the matrix. Production of thermal spray coatings containing liquid lubricants has not yet been achieved because of the complexity of keeping a liquid in a solid matrix during the spraying process. In the present article, the first liquid-solid self-lubricating thermal spray coatings are presented. The coatings are produced by inserting lubricant-filled capsules inside a polymeric matrix. The goal of the coating is to release lubricant to the system when needed. The first produced coatings consisted solely of capsules for confirming the feasibility of the process. For obtaining such a coating, the liquid-filled capsules were injected in the thermal spray flame without any other feedstock material. Once the concept and the idea were proven, a polymer was co-sprayed together with the capsules to obtain a coating containing the lubricant-filled capsules distributed in the solid polymeric matrix. The coatings and the self-lubricated properties have been investigated by means of optical microscopy, Scanning Electron Microscopy, and tribological tests.Item Metallurgical study of SiCNiCr plasma-sprayed coatings(1992-01-15) Alonso, F.; Fagoaga, I.; Oregui, P.; Viviente, J. L.; Centros PRE-FUSION TECNALIA - (FORMER); EXTREMAT; TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOSCermet materials are widely used as protective coatings for wear problems; in particular, WCCo and Cr3C2NiCr cermets are well known. However, SiC cermets appear as alternative materials for some applications. In this study an SiCNiCr cermet has been plasma sprayed and its metallurgical structure determined. Despite the fact that SiC is not suitable for plasma spraying, the proper choice of spraying parameters makes it possible to produce coatings with a composite structure of unmodified SiC particles in an Ni20Cr alloy matrix. Such coatings are acceptable from the viewpoint of providing adequate resistance to abrasion, but their microstructure is not stable, particularly in high temperature environments, owing to the tendency of SiC to react with the metal matrix. The metallurgical structure of the coating in the assprayed condition and its degradation at high temperature (up to 1000 °C) have been studied by means of analytical techniques such as optical microscopy, scanning electron microscopy, X-ray diffraction and energy-dispersive spectroscopy microanalysis.Item Multilayer coatings by continuous detonation system spray technique(1998-04-01) Fagoaga, I.; Viviente, J. L.; Gavin, P.; Bronte, J. M.; Garcia, J.; Tagle, J. A.; EXTREMAT; TECNOLOGÍA DE MEMBRANAS E INTENSIFICACIÓN DE PROCESOSSurface protection of high-temperature components for power generation has become one of the most advanced fields of modern engineering. In this area, a multilayer coating of chromium oxide/chromium carbide for erosion-corrosion protection of furnace boiler-walls has been produced by thermal spray continuous detonation system (CDS) technique. These composite coatings present a microstructure made by alternate phases of chromium carbide cermet and oxides resulting from preferential oxidation of chromium compounds. Mechanisms for the generation of such mixed structure are discussed. Produced coatings have been characterized by electron probe microanalysis, X-ray diffraction and ultramicrohardness techniques, combined with traditional procedures of metallographic preparation, quantitative image analysis, and microhardness testing.Item Thermally sprayed SiC coatings for offshore wind turbine bearing applications(2013-12) Mubarok, F.; Armada, S.; Fagoaga, I.; Espallargas, N.; EXTREMATTribological tests were conducted on thermally sprayed silicon carbide (SiC) coatings to investigate its potential on reducing wear in offshore wind turbine bearings. The tests were carried out under dry conditions, 3.5 wt.% NaCl solution, and polyalfaolefin (PAO)-lubricated conditions. In order to obtain good quality SiC coatings, it is compulsory to modify the feedstock to limit SiC decomposition during atmospheric spraying process. The SiC feedstock used in this research has been modified with yttrium aluminum garnet (Y 3Al5O12) oxide additives that originated from its metal salt precursors. High-frequency pulse detonation (HFPD) technique has been utilized to produce coatings of around 100 μm in thickness. The sliding tests have recorded the lowest coefficient of friction (COF) of 0.15 in PAO condition and the highest COF of 0.50 in dry sliding. The wear tracks morphology show that during dry sliding test, the coatings experience abrasive wear accompanied by tribo-oxidation reaction that initiates crack formation along the splat boundaries. On the other two sliding test conditions (NaCl and PAO), polishing of asperities and some grain plowing from the splats were observed in the wear tracks. Tribochemical wear was found to be the main mechanism producing smooth surfaces. Nevertheless, in all cases, the wear losses were negligible.Item Understanding the influence of micro- and sub-micro structural features on the mechanical properties of HVO/AF sprayed WC-CoCr cermets(ASM International, 2017) Parco, M.; Fagoaga, I.; Barykin, G.; Vaquero, C.; Chuvilin, A.; EXTREMATHVOF processes represent the state of art for the spray deposition of wear and corrosion resistant coatings since their supersonic gas velocities in combination with moderate flame temperatures allow the deposition of optimal coatings with very high bond strengths, fine surface finishes and low oxide levels. However, new generation coating materials (fine powders), stringent quality requirements and the high productivity demanded by the industry, push the HVOF technologies to their limits. Recently, a novel air-oxygen controlled high velocity combustion process has been development by Tecnalia. The system operates within the supersonic regime using a broad range of fuel/oxidant ratios thanks to the use of air-oxygen mixtures and a carefully optimized gun design. Extremely low flame temperatures can be achieved while keeping a supersonic flow of combustion products, thus allowing the solid state deposition of almost all industrially relevant metal alloys with superior deposit qualities. In this work, a systematic investigation of the influence of the powder particle size and gun configuration on resulting coating microstructural features has been performed. For comparison, two fine structured commercially available WC10Co4Cr powders with different particle size distributions have been investigated. The coating structure has been characterized with by high resolution SEM cross-section imaging and X-ray diffraction analysis. Resulting coatings are characterized by highly dense structures, a high reterion of the primary carbides, average microhardness of up 1885 HV0.3 and fracture toughness varying between 3 and 7 MPa.m-1/2 depending on the powder particle size distribution and the process conditions used.