Third-Body and Dissipation Energy in Green Tribology Film

• Main Authors: Shih-Chen Shi, Shia-Seng Pek
• Format: Article
• Language: English
• Published: MDPI AG 2019-09-01
• Series: Applied Sciences
• Subjects: third body; dissipation energy; tribology; hydroxypropyl methylcellulose (HPMC); additive; green material
• Online Access: https://www.mdpi.com/2076-3417/9/18/3787

Green tribology film comprising hydroxypropyl methylcellulose modified with nanoparticles and molybdenum disulfide was prepared by the solvent evaporation method. The nanoparticle additives were Al, Cu, Al₂O₃, and CuO. The tribological behavior of nanoparticles and MoS₂ was investigated using a ball-on-disk tribometer. The surface morphologies and worn surfaces were observed through scanning electron microscopy. The preferred orientation and crystallographic structure of MoS₂ and nanoparticles in the composites were studied via X-ray diffraction. Energy-dispersive X-ray spectroscopy was used to analyze the transfer film formed on the counterball. The surface profile, wear depth, wear width, and wear volume were studied by a 3D optical profiler. The synergistic effect of micro-platelet MoS₂ and nanoparticles contributed to the excellent wear resistances. It was found that the wear volume of hydroxypropyl methylcellulose (HPMC)/MoS₂ composites decreased dramatically when Al, Cu, and CuO were used as fillers, and it decreased slightly with Al₂O₃. The optimal wear resistance was obtained with 3 wt.% additives. These filled composites had a lower coefficient of friction lower than that of unfilled HPMC/MoS₂. The optimal result was observed for the HPMC/MoS₂/CuO 3 wt.% composite coating, which reduces the wear and friction coefficient by 90% and 84%, respectively, as compared to coatings without additives. Nanoparticles existed in the wear track as the third particles improved the load capacity of the composites. The wear mechanism of the composites is discussed in terms of the worn surfaces and the analysis of transfer film with a third-body approach. The dissipation energy theory is used to evaluate the dominant wear mechanism of the system.