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7310 |
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Wednesday, May 04, 2022, Hall G1 2:20 PM HVOF / HVAF Spraying I |
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Comparison of microstructure and properties of HVOF double carbides coatings deposited on magnesium substrate |
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Leszek Latka* / Wroclaw University of Science and Technology, Poland Ewa Jonda / Department of Engineering Materials and Biomaterials, Silesian University of Technology, Poland Monika Górnik/ Department of Metal Forming, Welding and Metrology, Faculty of Mechanical Engineering, Wroclaw University of Science and Technology, Poland Marcin Godzierz/ Department of Metal Forming, Welding and Metrology, Faculty of Mechanical Engineering, Wroclaw University of Science and Technology, Poland |
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The main goal of the present work was to investigate and compare the impact of the different spray distance of HVOF on the microstructure and selected properties sprayed coatings deposited onto magnesium alloy substrate. Three coatings with the same WC-Cr3C2-Ni powder were made, changing the spray distance from the substrate in the following order: 320, 360 and 400 mm. Usually, in order to improve the adhesion of the coating to the substrate, bond coat are used. Some novelty in the proposed solution was direct spraying on a soft magnesium substrate, which resulted from the properties of the WC-Cr3C2-Ni powder used for thermal spraying, the matrix of which is soft nickel. The parameters of the spraying process (including the distance between the gun nozzle outlet and the substrate material) determine the temperature of the particles during spraying, which has a significant impact on the microstructure and properties of the manufactured coatings. The manufactured coatings were investigated in terms of their microstructure and selected mechanical properties. The microstructure of the samples has been characterized by means of SEM and XRD. Additionally, tests of selected mechanical properties, such as instrumented indentation (HIT,EIT) and also microhardness, porosity and residual stress have been estimated. With 400 mm of spray distance minor presence of WC6O6 was detected, most likely as an effect of higher spraying distance, leading to partially oxidation of WC at powders particles boundaries. In obtained results it is clearly seen, that residual stresses have the lowest values for coating sprayed from the shorter distance. This tendency is visible for both, linear and shear stresses. The crystallite sizes are also the smallest for the shorter spray distance. Such fine structure shows a tendency to good redistribute of the thermal stresses in the sprayed coating and also on the coating-substrate interface. |