| LI Guotao,HE Qiang,XU Zehua,ZHANG Lei,CHEN Yonggang,DU Zhicai.Effect of KH550 Modified Nano-mullite on Tribological Properties of Polyurea Grease[J],53(9):158-166 |
| Effect of KH550 Modified Nano-mullite on Tribological Properties of Polyurea Grease |
| Received:May 02, 2023 Revised:October 30, 2023 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.09.015 |
| KeyWord:mullite nano-additives KH550 polyurea grease tribological properties wear mechanism |
| Author | Institution |
| LI Guotao |
College of Civil Aviation Safety Engineering, Civil Aviation Flight University of China, Sichuan Guanghan , China |
| HE Qiang |
College of Civil Aviation Safety Engineering, Civil Aviation Flight University of China, Sichuan Guanghan , China |
| XU Zehua |
College of Civil Aviation Safety Engineering, Civil Aviation Flight University of China, Sichuan Guanghan , China |
| ZHANG Lei |
College of Civil Aviation Safety Engineering, Civil Aviation Flight University of China, Sichuan Guanghan , China |
| CHEN Yonggang |
College of Civil Aviation Safety Engineering, Civil Aviation Flight University of China, Sichuan Guanghan , China |
| DU Zhicai |
College of Civil Aviation Safety Engineering, Civil Aviation Flight University of China, Sichuan Guanghan , China |
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| Abstract: |
| As a traditional lubricant medium, lubricating grease effectively reduces the friction and wear of mechanical equipment during operation. Polyurea lubricating grease is highly favored due to its good thermal stability, oxidative stability, and corrosion resistance. With the rapid development of modern industries, people's requirements for the performance of lubricating grease are becoming increasingly demanding. Adding nanoparticles to lubricating grease is a feasible solution to improve its lubricating performance. However, nano oxides tend to agglomerate due to their small volume and large specific surface area. The currently used method is to modify the surface of nanoparticles to improve their dispersibility. Therefore, this study chose to investigate the effect of KH550-modified mullite (Al2O3-SiO2 system) on the frictional properties of polyurea lubricating grease. In this study, the silica coupling agent (KH550) was used to modify the surface of nano-mullite, and polyurea lubricating grease containing 0.03% nano-mullite and KH-mullite were prepared, respectively. The frictional properties of polyurea lubricating grease with nano-mullite and KH-mullite as additives were evaluated with a four-ball friction tester (MRS-10D). GCr15 steel balls were used as the friction pairs in the test, and a composite grease with a mass of 10 g was used each time. The test duration was 60 minutes. The surface morphology of the worn surface was observed with a scanning electron microscope (SEM) and a three-dimensional surface profiler. Energy-dispersive X-ray spectroscopy (EDS) was used to analyze the element content of the worn surface and X-ray photoelectron spectroscopy (XPS) was used to analyze the valence states of the elements in the lubricating film on the worn surface to explore the mechanism of mullite and KH-mullite in polyurea lubricating grease. The results showed that mullite, as an additive, could effectively improve the frictional properties of polyurea lubricating grease. Compared with that before modification, the nano-KH-mullite after modification showed better anti-wear and friction-reducing properties in polyurea lubricating grease, with a decrease in friction coefficient and wear scar diameter of 22.4% and 15.6%, respectively. Observations were made on the worn surface using SEM and a 3D surface profilometer, and it was found that after the addition of molybdenum disulfide lubricant, there were few wide and deep furrows on the worn surface, indicating the presence of abrasive wear. In contrast, the wear surface lubricated with KH-mullite was smoother, and the surface roughness was improved, indicating the presence of polished wear. EDS analysis revealed that, compared with the worn surface lubricated with mullite, the worn surface lubricated with KH-mullite had an increased oxygen element content, indicating that KH-mullite could deposit a large amount on the frictional surface to provide a friction repair effect. XPS element analysis showed that KH-mullite had good compatibility with polyurea lubricating grease, and could carry the stress between the friction pairs in the lubricating film while moving along the surface, transforming the sliding friction into rolling friction and thereby improving the frictional performance of the polyurea lubricating grease. Therefore, it can be concluded that both mullite and KH-mullite can improve the lubricating performance of polyurea grease, but KH-mullite modified with silane coupling agent exhibits superior anti-friction and anti-wear properties. |
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