Tribological Studies of Transmission Oil Dispersed With Molybdenum Disulfide and Tungsten Disulfide Nanoparticles

This paper compares the tribological properties of transmission oil dispersed with molybdenum disulfide (MoS₂) and tungsten disulfide (WS₂) nanoparticles. Lubricant samples are prepared by dispersing MoS₂ and WS₂ nanoparticles in 0.5 wt.% in transmission oil. The nanoparticles are stabilized in the lubricant by surface modification with surfactant SPAN 80. The stability of the lubricant in terms of size variation of dispersed nanoparticles is evaluated using particle size analyzer. The antiwear, antifriction, and extreme pressure (EP) properties are tested on a four-ball wear tester and a comparison is made to assess the relative performance of MoS₂ and WS₂ nanoparticles. The friction and wear characteristics of lubricant dispersed with nanoparticles are strongly dependent upon the load taken into consideration. The lubricant dispersed with WS₂ nanoparticles gave higher weld load and load wear index (LWI) than that of lubricant dispersed with MoS₂ nanoparticles. The metallographic studies show that under high load conditions, the WS₂ nanoparticles deposit more than MoS₂ nanoparticles, thereby giving better performance at higher load conditions.