The effect of chromium and molybdenum carbides alloing on corrosion resistance of mesostructure WC-Nі composites in chloride environment

DOI: 10.62564/M4-OM1206

Oleksandr Matviichuk¹, Vasyl Vynar², Vasyl Ivashkiv², Nadiia Ratska², Сhrystyna Vasyliv<sup>2

1</sup>V. Bakul Institute for Superhard Materials of the National Academy of Sciences of Ukraine
²Karpenko Physico-Mechanical Institute of NAS of Ukraine, Lviv


Composites of the WC-Ni system are characterized by high wear resistance and crack resistance and are used in the sliding friction pairs [1]. Friction pairs based on WC-Ni alloys work well in such not electrically conductive environments as petroleum products and ammonia, but are not corrosion resistant in electrolytes such as chloride-containing solutions. One solution of the problem is to increase the corrosion resistance of the Ni binder. The aim of the work was to study the electrochemical characteristics of the WC-20 wt% Ni mesostructural alloy with the addition of 1%Cr3C2 and 0.5%Mo2C in chloride-containing solutions. The characteristics of corrosion processes were studied in the potentiodynamic mode in solutions: 3% NaCl+0.5% CH3COOH (pH 3), 3%NaCl (pH 7) and 3% NaCl + 0.0004% NaOH (pH 10). It is shown that the modification of the mesostructural alloy WC-20% wt. Ni by Cr3C2 and Mo2C contributes to shifting the electrode potential to more positive values. Taking into account the pH of the environment, there is an improvement in the potential values for both materials with a shift in the environment pH from 3 to 10. It was established that the corrosion current density of the WC- Ni alloy in a neutral 3% NaCl solution is 1∙10-3 mA/cm2. In alloy with 1%Cr3C2 and 0.5%Mo2C, the current density decreases by almost an order of magnitude and is 5∙10-4 mA/cm2. A similar trend is observed in acidic and alkaline environments. In an acidic environment, the corrosion current density of basic alloy and modified by carbides is 5∙10-3 and 1∙10-3 mA/cm2, in an alkaline environment – 6∙10-4 and 2∙10-4 mA/cm2, respectively. In an environment with a pH3, nickel is oxidized and goes into solution, while in an environment with a pH10, its partial passivation occurs. Therefore, alloying WC-Ni mesocomposition with 1%Cr3C2 and 0.5%Mo2C increases its corrosion resistance in environments with different acidity. The maximum corrosion resistance is observed in an alkaline environment.

Keywords
Metal-ceramic mesostructural composites, corrosion resistance

Acknowledgments
Not provided

References
[1] Baranovskii A. M. and Bezruchko A. G., Antifriction materials based on hard alloys of the WСNi type and the experience of their application in heavily loaded sliding friction couples, Instrum. Svit, 2013, No.1(57). P.12–15.