Influence of molybdenum on the mechanical properties, electrochemical corrosion and wear behavior of electrodeposited Ni-Mo alloy

Abstract

Abstract In the present work, the influence of molybdenum (Mo) content on the grain size, hardness, corrosion and wear behavior of Ni-Mo alloy coatings electrodeposited from citrate electrolyte has been studied. Crack free Ni-Mo alloy with different Mo content (3, 5, 6, 9 and 12 at.%) was obtained using direct current and pulsed current electrodeposition. It was observed that the grain size of Ni-Mo alloy decreased with increase in Mo content. Hardness of the coatings increased with Mo content and decreased subsequently above 9 at.% Mo as per inverse Hall-Petch effect. Potentiodynamic polarization tests carried out in 2\u202fN H2SO4 suggested increase in both corrosion current and passive current density with increase in Mo content. In addition, both friction coefficient and dry sliding wear rate of Ni-Mo coatings decreased with increase in Mo content. The results are rationalized based on grain size and Mo content in the coatings. Finally, Ni-Mo and Ni-W coatings were compared with hard chrome with respect to mechanical properties, wear and corrosion resistance. Results indicated that, Ni-Mo coatings exhibit least friction coefficient (0.2–0.3) amongst Ni-W and hard chrome coatings.