Tribology Properties of Synthesized Multiscale Lamellar WS2 and Their Synergistic Effect with Anti-Wear Agent ZDDP

Abstract

The microscale/nanoscale lamellar-structure WS 2 particles with sizes of 2 µm and 500 nm were synthesized by solid-phase reaction method and characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The synergies between microscale/nanoscale WS 2 particles and ZDDP as lubricating oil additives was evaluated by means of UMT-2 tribometer at room temperature. The wear scars were examined with SEM and electron-probe micro-analyzer (EPMA). The results show that the anti-wear properties were improved and the friction coefficient was greatly decreased with the simultaneous addition of WS 2 particles and ZDDP, and the largest reduction of friction coefficient was 47.2% compared with that in base oil. Moreover, the presence of ZDDP additive in the lubricant further enhances the friction-reduction and anti-wear effect of microscale/nanoscale WS 2 . This confirms that there is a synergistic effect between WS 2 particles and ZDDP.

Wear and Rolling Contact Fatigue Analysis of AISI 52100 Bearing Steel in Presence of Additivated Lubricants

“…The difference in the position of the peaks of WS 2 is due to the possibility of the presence of defects, which might have generated during the tribo-tests. Similar results of detection of only WS 2 without any other reactant products in the tribo-film was also reported by Wu et al [22]. However, in case of MoS 2 and PT, apart from the deposition of the additives, several other peaks were also observed, especially iron oxides.…”

“…The reported values of interlayer spacing in case of MoS 2 and WS 2 are approximately 6.15-6.5Ȧ [27][28][29], while for PT the interlayer spacing is 15.532Ȧ [30]. The friction reduction in case of these lamellar additives is due to the weak van der Waals forces between the layers, which shear themselves easily; hence, the increase in the interlayer spacing will result in further easy shearing, making a strong point for an enhanced performance of PT than MoS 2 and WS 2 ; thus, reducing the friction between the tribo-pairs [22]. However, WS 2 indicated a lower coefficient of friction; this may be due to the stable film during the short anti-wear tests, but in the extended RCF tests, when the situation was more dynamic due to the free rotation of the lower balls (as the bottom balls are not fixed), the WS 2 could not form a stable film and resulted in the easy formation of surface cracks.…”

Tribological Analysis of Several Coatings under Flood and Cryogenic Cooling Conditions

“…The apparent friction coefficient is strongly correlated to the sliding speed and the contact pressure. Many researchers have shown that the friction coefficient drops when increasing the sliding speed [14][15][16][17][18]. Rech et al [3] conducted tribological tests on various work materials with a TiN-coated carbide tool; the friction coefficient dropped significantly with increasing sliding speeds.…”

Synergistic lubrication effects and tribological properties of graphene/oil-based lubricant systems

“…Common additives including zinc dialkyl dithiophosphate (ZDDP) [3], Al 2 O 3 [4], MoS 2 [5], SiO 2 [6], WS 2 [7], graphene [8], graphene oxide [9], and carbon nanotubes [10] have been widely investigated in industries and social academia. It has indicated that the friction-reducing ability of base oils was significantly improved by adding these additives, especially graphene.…”