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7332 |
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Friday, May 06, 2022, Hall G2 12:00 PM Characterization & Testing Methods I |
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Characterization of the microstructure, mechanical properties and corrosion behavior of submicron WC-12Co coatings produced by CGS and HVAF compared with sintered bulk material |
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Núria Cinca* / Hyperion Materials and Technologies, Spain Assis Benedetti / Univ Estadual Paulista - UNESP, Brazil Olivier Lavigne/ Hyperion Materials and Technologies, Spain Sergi Dosta/ Universitat de Barcelona, Spain Heli Koivuluoto/ Tampere University, Findland Rico Drehmann/ Chemnitz University of Technology, Germany Thomas Grund/ Chemnitz University of Technology, Germany Ville Matikainen/ Valmet Technologies Oy, Findland |
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Both as bulk material and coatings, cemented carbides currently occupy very well-established market niches and exhibit a promising future thanks to the development of compositions and manufacturing parameters. Direct comparisons of the properties of both are found only very rarely in the literature, very likely because the fields of application are complementary to each other but keep mostly separated. The current work is intended to evaluate similarities and differences in terms of microstructure and properties for two submicron WC-12Co coatings obtained by High Velocity Air Fuel (HVAF) and Cold Gas Spray (CGS), together with a conventional sintered part. Binder mean free path, together with carbide size and distribution, as well as carbide decomposition, are discussed according to the inherent characteristic features of each processing method. This covers a wide range in terms of the mechanical and thermal stresses acting on the coating material. While in CGS, the impacting particles do not melt, but experience extremely high plastic strain rates, the cobalt matrix is fully molten in the sintering process, allowing time enough for diffusion processes. HVAF is to be placed in between, since the deposition process is characterized by a moderate heat input, leading to partial and/or full melting of cobalt, followed by rapid cooling. The microstructure and phases of the deposited coatings and bulk are characterized by using SEM and XRD. EBSD investigations enable the identification of the crystallographic structure of the binder phase and any potential texturization in the samples. The mechanical properties such as hardness and fracture toughness are investigated as well. Additionally, electrochemical corrosion measurements in NaCl media are presented to evaluate the facility for electrolyte penetration and how the degradation of the material is affected by its inherent microstructure. |