Preparation of nanocrystalline Ni–Mo and Ni–Mo–ZrO2 coating and investigation of its corrosion resistance and wear behaviors

Abstract

Nanocrystalline Ni–Mo and Ni–Mo–ZrO2 coatings were designed and successfully fabricated via electrodeposition process in direct current mode. Impacts of molybdate and ZrO2 nanoparticles, cathodic current density (ic) on surface, structure and performance of Ni–Mo alloy were analyzed. Electrochemical behaviors were evaluated by electrochemical impedance method in sodium chloride solution. A more compact and consistent surface morphology was prepared by introducing molybdate in nickel. Grain sizes of Ni–Mo alloy decreased as molybdate increased from 2 to 6 g L−1, and enlarged as ic increased. After incorporation of ZrO2, the grains initially decreased to 12 nm and later increased to 18 nm. The structure of the deposit is a face-centered cubic phase. With the increase of molybdate content, the preferential Ni (220) crystal plane was changed to oriented (111) plane. The Ni–Mo alloy comprises 91 wt% Ni and 5.4 wt% Mo. Ra of Ni–Mo–ZrO2 was 73 ± 4 nm. Ni–Mo alloys obtained at 20 mA cm−2 and 2 g L−1 molybdate possess the best corrosion-resistant behavior. Incorporation of ZrO2 can strengthen electrochemical stability and anti-wear behavior of Ni–Mo alloy. The inclusion of ZrO2 refined the grain size from 18 to 12 nm. The Ni–Mo/ZrO2 coatings electrodeposited under 2–4 g L−1 Na2MoO4·2H2O, 20–40 mA cm−2, 10–15 g L−1 ZrO2 have excellent wear and corrosion resistance.