Abstract
New coatings resistant to corrosion in high-temperature molten zinc aluminum were prepared by supersonic flame spraying of various composite powders. These composite powders were prepared by mixing, granulation, and heat treatment of various proportions of Mo–B4C powder and WC and Co powder. X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF–STEM), energy dispersive X-ray spectroscopy (EDS), and mechanical analysis were used to study the effects of Mo–B4C on the microstructure, phase, porosity, bonding strength, and elastic modulus of the composite powder and coating. Results show that the addition of an appropriate quantity of Mo–B4C reacts with Co to form ternary borides CoMo2B2 and CoMoB. Ternary boride forms a perfect continuous interface, improving the mechanical properties and corrosion resistance property of the coating. When the amount of Mo–B4C added was 35.2%, the mechanical properties of the prepared coating reached optimal values: minimum porosity of 0.31 ± 0.15%, coating bonding strength of 77.81 ± 1.77 MPa, nanoindentation hardness of 20.12 ± 1.85 GPa, Young’s modulus of 281.52 ± 30.22 GPa, and fracture toughness of 6.38 ± 0.45 MPa·m1/2.
Highlights
Hot-dip galvanizing is a very economical and efficient method to prevent steel corrosion during atmospheric exposure [1]
When a small amount of Mo–B4 C was added, it reacted with Co to produce ternary borides CoMo2 B2 and CoMoB
When Mo–B4 C was added to excess, Mo and
Summary
Hot-dip galvanizing is a very economical and efficient method to prevent steel corrosion during atmospheric exposure [1]. Because of the high economic impact of solutions to these problems, scholars have remained committed to the study of the surface coatings of sink rolls used for preparing hot-dip galvanized steels. MoB–CoCr coatings in the hot-dip galvanizing industry is clearly better than those of other alloys owing to the non-wettability of boride in molten zinc, the compactness of the coating with its lower defect rate, and the superior mechanical properties, all meeting the needs of sink roll use. Successfully prepared a WC–WB–W2 B composite coating via in-situ synthesis based on B4 C–W–WC Their coating exhibited high density, excellent mechanical properties, and high resistance to molten zinc corrosion because of the high B content of its ceramic phase. A low-porosity coating rich in CoMoB and CoMo2 B2 ternary boride, which could enhance resistance to molten zinc–aluminum corrosion, was successfully prepared with mechanical properties equivalent to those of traditional WC–Co coatings, but stronger resistance to molten zinc–aluminum corrosion due to the ternary boride
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