Manifestation of Hall–Petch breakdown in nanocrystalline electrodeposited Ni-MoS2 coating and its structure dependent wear resistance behavior

Abstract

Abstract This work reports successful development of pure Ni and Ni-MoS2 bulk nano-crystalline electrodeposited coatings and it's mechanical and wear behavior. The crystallite size of the Ni in the Ni-MoS2 coatings varies from 31.6 to 146.8 nm at different loading levels of MoS2 (1, 2, 5, 10 and 20 g/l) in the deposition bath. The nanocrystalline Ni in the Ni-MoS2 coatings follow inverse Hall-Petch relation, as the hardness value is observed to decrease with decrease in crystallite size of the Ni below 62.2 nm. The wear mechanism of the electrodeposited pure Ni and Ni-MoS2 electrodeposits has been analyzed using micro-scratch technique with progressive load of 100 to 1000 mN. Moreover, all the Ni-MoS2 coatings display significantly improved wear resistance than the pure Ni electrodeposit due to the higher hardness of the Ni-MoS2 coatings caused by dispersion hardening. Moreover, the wear behavior of the Ni-MoS2 coatings has been correlated with crystal orientation, coating morphology and hardness to establish the possible abrasive wear mechanism.