Abstract
Recent work indicates that the high-velocity oxy-fuel (HVOF) thermal spraying WC–Co coatings have been used to enhance the wear resistance of various engineering components in a variety of industrial environments. In the present work, WC–Co powder, containing Cr particles in an amount of 10%, was deposited on ductile cast iron with the HVOF thermal spray coating technique. An investigation was conducted to determine the role of Cr particles in the WC–Co coating produced with the HVOF technique on microstructure, mechanical, and wear properties in a system of type: WC-Co coating/ductile cast iron. The microstructure of the HVOF-sprayed WC–Co + Cr coating was characterised by light microscopy, X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscope (TEM), and energy-dispersive X-ray spectroscopy (EDS). The analysis of the microstructure showed the formation of a coating with low porosity, compact structure, and good adhesion to the substrate with a typical lamellar structure composed of fine molten Cr particles and finely fragmented WC grains embedded in a Co matrix, reaching the size of nanocrystalline. The scratch test was applied for the analysis of the adhesion of coatings to the substrate. The erosion behaviour and mechanism of material removal was studied and discussed based on microstructural examinations. Moreover, the results were discussed in relation to the bending strength test, including cracks and delamination in the system of the WC–Co + Cr/ductile cast iron, as microhardness and erosion resistance of the coating. It was found that the addition of Cr particles to the WC–Co powder, which causes hardening of the binder phase is a key influence on increased mechanical and wear properties in the studied system. Additionally, due to the construction of nanostructured coatings, suitable proportion of hard and soft phases, the technique sprayed HVOF coatings have advantageous properties such as high density and good slurry erosion resistance.
Highlights
The high-velocity oxy-fuel (HVOF)—that is the High-Velocity Oxy-Fuel method—is still a developing technology of surface modification, leading to increased erosion and corrosion resistance, and extended usage time of crucial parts of machines and devices [1]
Owing to the relatively low process temperature and due to a relatively short period of charge powder occupying the gas jet, adverse phenomena, connected with changes within the phase composition of coatings, such as carbide decomposition and oxidation of metallic and carbide materials, are limited. This allows for the production of carbide coatings with special properties, such as high hardness, high abrasion and erosion resistance, high-temperature corrosion resistance, good thermal conductivity and lower porosity, as well as higher adhesion to the substrate, in comparison to coatings generated with the use of conventional plasma spraying [5,6,7]
This study focuses on the creation of WC–Co + Cr composite coatings using the HVOF technique, as well as on the characteristics of their microstructure, mechanical properties, and wear in order to improve the operational characteristics of the responsible parts of machines and devices, made of ductile iron
Summary
The HVOF—that is the High-Velocity Oxy-Fuel method—is still a developing technology of surface modification, leading to increased erosion and corrosion resistance, and extended usage time of crucial parts of machines and devices [1]. Owing to the relatively low process temperature and due to a relatively short period of charge powder occupying the gas jet, adverse phenomena, connected with changes within the phase composition of coatings, such as carbide decomposition and oxidation of metallic and carbide materials, are limited This allows for the production of carbide coatings with special properties, such as high hardness, high abrasion and erosion resistance, high-temperature corrosion resistance, good thermal conductivity and lower porosity, as well as higher adhesion to the substrate, in comparison to coatings generated with the use of conventional plasma spraying [5,6,7]. The study assessed the effect of Materials 2021, 14, 3282 introducing Cr particles into the WC–12Co charge powder on the relationship between the microstructure—properties of the HVOF sprayed WC–Co coating
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