OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 3 2025 Fig. 8. Nyquist plots of coatings in an aqueous solution containing 3.5% NaCl near the stationary potential in the frequency range from 50 kHz to 10 MHz: a – NiCrBSi PR-NKh17SR4); b – NiCrBSi (PR-NKh17SR4)+10 wt.% B4C; c – NiCr/WC (VSNGN-85); d – 0.4% C-Mn a b c d carbide into the self-fluxing alloy NiCrBSi (PR-NKh17SR4) significantly improves the corrosion resistance of the coating. 2. The modified coating demonstrates the most noble corrosion potential (−260±10 mV) and the minimum corrosion current (0.8±0.02 μA/cm2), which indicates its high thermodynamic and kinetic stability in an aggressive environment. These indicators significantly exceed the characteristics of both the base alloy NiCrBSi (PR-NKh17SR4) and the commercial coating NiCr/WC (VSNGN-85). 3. Microstructural analysis revealed that boron carbide promotes the formation of a dense multilayer protective system, including an external passivation layer based on chromium and boron oxides, a main matrix with dispersed NiB2 particles, and an increase in the volume of the NiSi phase. Such a structure not only reduces the porosity of the coating, but also provides effective protection against the development of general and crevice corrosion. 4. Impedance spectroscopy confirmed the formation of a dense protective film, as evidenced by high values of polarization resistance (215±25 kOhm cm2) and low values of the phase element constant.
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