Abstract
In this study, Fe40Cr19Mo18C15B8 amorphous coatings were prepared using high velocity oxygen fuel (HVOF) technology. Different temperatures were used in the heat treatment (600 °C, 650 °C, and 700 °C) and the annealed coatings were analyzed by DSC, SEM, TEM, and XRD. XRD and DSC results showed that the coating started to form a crystalline structure after annealing at 650 °C. From the SEM observation, it can be found that when the annealing temperature of the Fe-based amorphous alloy coating reached 700 °C, the surface morphology of the coating became relatively flat. TEM observation showed that when the annealing temperature of the Fe-based amorphous alloy coating was 700 °C, crystal grains in the coating recrystallized with a grain size of 5–20 nm. SAED analysis showed that the precipitated carbide phase was M23C6 phase with different crystal orientations (M = Fe, Cr, Mo). Finally, the corrosion polarization curve showed that the corrosion current density of the coating after annealing only increased by 9.13 μA/cm2, which indicated that the coating after annealing treatment still had excellent corrosion resistance. It also proved that the Fe-based amorphous alloy coating can be used in high-temperature environments. XPS analysis showed that after annealing FeO and Fe2O3 oxide components increased, and the formation of a large number of crystals in the coating resulted in a decrease in corrosion resistance.
Highlights
The method of manufacturing amorphous metals involves melting the metals down and applying a rapid cooling rate, so that the metal atoms do not have chance to form an orderly arrangement during the condensation process and form an amorphous state
Amorphous metals are free of grains and grain boundaries, which results in high-strength mechanical properties [1], high corrosion resistance [2], and excellent soft magnetization [3]
The corrosion mechanism of the Fe-based amorphous alloy coating was observed by polarization test, and the defects of the coating were found to come from cracks and recrystallization during thermal spraying under TEM observation
Summary
The method of manufacturing amorphous metals involves melting the metals down and applying a rapid cooling rate, so that the metal atoms do not have chance to form an orderly arrangement during the condensation process and form an amorphous state. Lee et al [15] prepared Fe40Cr19Mo18C15B8 alloy coatings using the HVOF method and compared them with 304SS and 316SS They found that the corrosion current density of 304SS and 316SS is lower than that of Fe-based amorphous alloy, the width of the passivation zone of stainless steel is smaller than that of the latter. This shows that the corrosion resistance of Fe-based amorphous alloy comes from its passivation protection. The corrosion mechanism of the Fe-based amorphous alloy coating was observed by polarization test, and the defects of the coating were found to come from cracks and recrystallization during thermal spraying under TEM observation
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