Physicomechanical properties of arc sprayed coating formed in supersonic mode

The mechanical properties and the failure mechanism of arc-sprayed coatings with 90Kh17R2GS cored wire (CW) depend on the sprayed air pressure (0.6 and 1.2 MPa). The residual tensile stresses in the coating obtained at the supersonic speed of airflow (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 coating properties formed by the supersonic airflow was explained by a decrease in droplets size of the CW melt and, accordingly, the thickness of the lamellas crystallized on the substrate, and also in a reduction in interlamellar oxides thickness in the coating due to the shorter flight time of droplets during spraying and, accordingly, less intense high-temperature oxidation. In addition, the increase in the proportion of translamellar failures compared to interlamellar delaminations during cohesive strength tests was explained by the dispersion strengthening of lamellas with nanosized particles of (Fe, Cr)₂B borides.