Electrochemical Corrosion Characterization of Submicron WC-12Co Coatings Produced by CGS and HVAF Compared with Sintered Bulks
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Data
2022-05-01
Autores
Cinca, Núria
Lavigne, Olivier
Peres, Riberto Nunes [UNESP]
Conze, Susan
Hoehn, Soeren
Dosta, Sergi
Koivuluoto, Heli
Kim, Chung
da Silva, Fernando Santos
Matikainen, Ville
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The electrochemical corrosion performance of WC-12 wt% Co in coating and bulk forms has been evaluated in a 3.56 wt% NaCl solution. The coatings were deposited by means of thermal spray techniques, i.e., cold gas spraying (CGS) and high-velocity air fuel (HVAF) spraying, while bulks with different WC sizes were manufactured by conventional pressing and sintering. Microstructural characterizations and phase composition determinations were carried out using scanning electron microscopy and X-ray diffraction. Differences in WC grain size and morphology, carbide dissolution, and cobalt binder phase transformation are discussed according to the inherent characteristics of each processing method. Together with surface roughness (polished/as-sprayed), these features have been observed to directly affect the electrochemical corrosion performance. Electrochemical measurements (open circuit potential, polarization resistance, electrochemical impedance spectroscopy, and polarization curves) showed that the as-sprayed CGS coating presented an electrochemical behavior similar to those of the bulk materials. This was attributed to the higher metallic character of this coating in comparison to that of the HVAF coating. The polished HVAF coating showed anodic activity lower than those of the bulk samples, most likely due to the presence of cobalt–tungsten carbide phases and eventually the lower amount of Co available for dissolution. Finally, the as-sprayed HVAF coating showed very high resistivity due to the presence of surface oxides generated during the deposition process.
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cemented carbides, cold gas spray, corrosion, high-velocity air fuel, thermal spray coatings
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Coatings, v. 12, n. 5, 2022.