Observational analysis highlights improved microhardness and cohesive strength in coatings from supersonic spray, suggesting beneficial impacts on performance and durability.
It was established that the mechanical properties and the failure mechanism of arc sprayed coatings with cored wire (CW) 90Kh17R2GS depend on the pressure of the sprayed air (0.6 and 1.2 MPa). It was found that residual tensile stresses in the coating obtained at a supersonic speed of air flow (600 m/s) decreased by 10%, and their microhardness and cohesive strength increased by 30 and 200%, respectively, relative to that formed at the subsonic speed (300 m/s). The improvement in the properties of the coating formed by a supersonic air flow was explained by: a decrease in the size of droplets of the CW melt and, accordingly, the thickness of the lamellas crystallizing on the substrate and also by a decrease in the thickness of interlamellar oxides in the coating due to a shorter flight of droplets during spraying and, accordingly, less intense high-temperature oxidation of their surface; dispersion strengthening of lamellas with nano-sized particles of (Fe, Cr)2B borides; an increase in the proportion of translamellar failures compared to interlamellar delaminations during cohesive strength tests.
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Hvozdetskyi et al. (2024) studied this question.
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