Synthesis and Properties of Electrodeposited Ni–Co/WS2 Nanocomposite Coatings

Abstract

Ni–Co coatings have gained widespread attention due to their potential in replacing hard chromium deposits (which have traditionally utilized toxic and corrosive chromic acid baths). A major challenge is to lower the high coefficient of friction of coated surfaces against steel, under dry sliding conditions. In this research, low friction Ni–Co/WS2 nanocomposite coatings have been prepared by a convenient, one-pot electrodeposition from aqueous Ni–Co plating baths containing WS2 particles. The embedment of the WS2 lubricants is found to reduce the friction coefficient of coating significantly, and an ultra-low friction coefficient of 0.16 is obtained for the coating having a WS2 content of 7.1 wt.%. Morphology and composition characterization of wear tracks reveal that the formation of a WS2-rich lubricating tribofilm on the contact surfaces is beneficial to a low friction coefficient and good oxidation resistance. The wettability of electrodeposited coatings was also investigated. Compared to pure Ni-Co coating, the Ni–Co/7.1 wt.% WS2 coating has an excellent hydrophobicity with a high water contact angle (WCA) of 157°, due to a rough surface with dual scale protrusions and the low surface energy of WS2.

Interfacial Aspects of Metal Matrix Composites Prepared from Liquid Metals and Aqueous Solutions: A Review

“…Furthermore, graphene [121] and nano-diamonds also appear in the literature as a reinforcement [80]. Electrodeposition enables the deposition of different Ni alloys with different reinforcements, such as Ni-P coating reinforced with CeO 2 -TiO 2 [122], Ni-B/SiC [123], Ni/graphene [124], Ni-W/SiC [125], Ni-W/Si 3 N 4 [126], Ni-Co/WS 2 [127] [128], Ni/Al 2 O 3 [129], Ni/SiC [130] or pure Ni-P itself [131,132].…”