Ni-doped WS2 composite coatings with various Ni contents were co-deposited using a radio frequency sputtering system on silicon wafer and AISI 440C stainless steel substrates. The microstructural characteristics of the WS2-Ni composite coatings and their tribological properties in vacuum were assessed. During introduction of Ni dopant in the WS2-Ni composite coating the sulfur/tungsten (S/W) ratio in the coating increased due to reduced preferential resputtering of sulfur atoms in the growing coating. The microstructure of the WS2-Ni composite coating varied from a fine columnar structure for Ni content equal to or less than 7.7 at.% to a featureless structure as the Ni content increased further. The Ni dopant inhibited the growth of the coarse columnar WS2 platelets which was accompanied by nanocrystallization and amorphization of the composite coating structure. WS2-Ni composite coatings with fine columnar structure exhibited relatively low hardness but showed a high tendency to form a lubricating transfer layer. It also demonstrated low brittleness and prolonged wear life in vacuum condition compared to coatings with dense featureless structure. The variation in tribological performance between the composite coatings resulted from the different wear mechanisms associated with their distinct microstructures.
Bibliographical noteFunding Information:
This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2010-0018289). This work was also supported by the National Key Basic Research Program of China (973) [grant number 2013CB632300] and the National Natural Science Foundation of China [grant number 51505465].
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Surfaces and Interfaces
- Surfaces, Coatings and Films
- Materials Chemistry