Effect of Oxidation and Crystallization on Pitting Initiation Behavior of Fe-Based Amorphous Coatings

Abstract

Fe-based amorphous coatings are typically fabricated by high-velocity oxygen-fuel spraying using industrial raw materials. The bonding mode between the coating particles and the corrosion mechanism of the coating in the chloride-rich environment were studied. The results indicate that some fine crystallites such as α-Fe and Fe3C tend to precipitate from the amorphous matrix as the kerosene flow rate increases or the travel speed of spraying gun decreases. Moreover, some precipitates of the (Cr, Fe)2O3 nanocrystal were detected in the metallurgical interfaces of the amorphous coating. The relationship among the amorphous volume fraction, porosity, and spraying parameters, such as the kerosene flow rate and the travel speed of the spray gun, were established. Due to an oxidation effect during spraying process, atomic diffusion, crystallite precipitation and regional depletion of Cr occur in the area along the pre-deposited side near the metallurgical bonding interface, leading to the initiation of pitting. A model of pitting initiation and expansion of Fe-based amorphous coatings is proposed in this paper.

Interfacial bonding of low-pressure plasma-sprayed Fe-based amorphous coating on 8090 Al–Li alloy

“…Compared to the conventional plasma-sprayed (PS) and HVOF-sprayed coatings, it can be found that the low-pressure plasma-sprayed (LPPS) coating has a considerable advantage over the conventional spraying method in terms of forming, and the average hardness is also higher than that of the other two coatings, indicating excellent performance in Figure 9.

Figure 9 Properties of iron-based AMC with different spraying methods [18,23,24,28,31,41–48].

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Wear resistance of Fe 66 Cr 10 Nb 5 B 19 detonation coatings under dry linearly reciprocating conditions and nanoscratch test

“…To obtain the metallic glass structure during spraying, special conditions must be created, namely, rapid heating of the particles to the molten state and a high cooling rate due to heat dissipation into the volume of the substrate material. During the spraying process, oxidation of the sprayed powder should be avoided, as the oxide lms formed on the surface favor heterogeneous nucleation, and negatively affect the properties of the coatings [17][18][19][20][21][22]. Among thermal spraying methods, the impulse nature of detonation spraying allows the formation of wear resistant and dense coatings with low crystalline phase content [23].…”