| With the development of modern science and technology, requirements to lubricating oil and its additives are increasing year by year, people get to know that the oil-soluble anti-wear and friction-reducing additives' final functionary conformation are always inorganic compounds. And they always can perfectly increase load-carrying abilities and extreme pressure properties of lubricating oil. The applications of inorganic particles are restricted by their dispersing performance. It is the application of nano-materials in lubrication that provides a new clue. The characterization, tribological performance and mechanism of anti-wear and friction reduction of nano-particles of CaCO3 and rare earths are studied in this paper. The main conclusions are reached as followed.1. The crystal structure and average sizes of nano-particles of CaCO3 and rare earths have been tested by a D/max-rB X-ray diffractometer. And the shapes and average sizes of nano-particles of CaCO3 and rare earths have been measured through TEM. The results indicated that both nano-particles of CaCO3 and rare earths appeared in spherical powder, and their diameters are 40nm and 11 nm, respectively.2. On the basis of HLB values suitable surfactant such as Tween-20, Tween-60, Span-20and Polyether are selected. The results show that they have nano-particles receiving very good dispersiveness and stability in the lubricating oil.3. Tribological performances of nano-particles of CaCO3 and rare earths as lubricating oil additives were studied in friction and wear test machine. The results indicated that dispersion and stability of nano-particles are key factor to use them as lubricating oil additives. Only with evenly-distributed cluster can the function of anti-wear and friction reduction be achieved.4. The optimal proportion of nano-particles of CaCO3 and rare earths is: CaCO3 (Wt%) : rare earths( Wt%)=1 : 1, and the content is 0.6% .5. The tested results of nano-particles of CaCO3 and rare earths' tribological chemical properties are studied through Scanning Electron Microscope(SEM), Energy Dispersion Spectrum(EDS) and X-ray Photoelectron Spectrum(XPS).6. The mechanism of anti-wear and friction reduction of nano-particles of CaCO3 and rare earths has been discussed and individual opinions of the nano-particles have been proposed.1)Nano-particles of CaCO3 and rare earths deposit on the friction surface, and tribological chemical reaction takes place, producing chemical reactive film, which can keep friction surface from wearing.2) Nano-particles of CaCO3 and rare earths appeared in spherical powder with the diameter of 40nm and 11 nm, respectively. They have different functions on friction surface, CaCO3 nano-particles work similar to "tiny ball bearing", which can support loads; and rare earths nano-particle can fill in and repair worn surfaces.3)Only with appropriate proportion, can nano-particles of CaCOs and rare earths concertedly function as properties of anti-wear and friction reduction. When both nano-particles of CaCO3 and rare earths are added in the lubricating oil, more CaCO3 nano-particles work similar to "tiny ball bearing", which can mostly support loads; on the contrary, more rare earths nano-particles mostly fill in and repair worn surfaces. These two nano-particles can't take effect solely, or work as concerted effect. In our research, when mass of nano-particles of CaCOs and rare earths are the same, CaCO3 nano-particles work as "tiny ball bearing" on the surface which filled by rare earths nano-particle, and function as properties of anti-wear and friction reduction.4) Through tribological chemical reaction, the nano-particles of CaC03, CaO and rare earths nano-particles form a deposited film on the worn surface, and improve anti-wear property of friction surface. It not only keeps friction surfaces from contacting directly, but also supports loads, so elastic deformation and plastic deformation caused by shearing stress are limited in lubricating films area, result in restraining adhesion wear and contacting fatigue o... |
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