Calcium Carbonate, Tribological Properties And Mechanism Of The Copper Particle Composition Is Used As Lubricant Additives

With the development of science and technology, requirements to lubricating oil and its additives are increasing year by year, and the capability requirements of the oils are on the up-and-up. People get to know that the traditional oil-soluble anti-wear and friction-reducing additives always produce the environment pollution, although they can increase load-carrying abilities and extreme pressure properties of lubricating oil. The applications of ordinary inorganic particles are restricted by their dispersing performance. Nowadays, It is the application of nano-materials in lubrication that provides a new way. The characterization, tribological performance and mechanism of anti-wear and friction reduction of nano-particles of CaCO3 and Cu 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 Cu have been tested by a D/max-rB X-ray diffractometer. And the shapes and average sizes of nano-particles of CaCO3 and Cu have been measured through TEM. The results indicated that both nano-particles of CaCO3 and Cu appeared as spherical powders, and their diameters are 40nm and 60nm, respectively.2. On the basis of HLB values suitable surfactants such as Tween-60, Span-20, Span-80 and Polyether are selected. The results show that they make nano-particles having very good dispersion and stability in the lubricating oils. It is the "capsules" of nano-materials in lubricating oils that give a new way to get good dispersion and stability.3. Tribological performances of nano-particles of CaCO3 and Cu as lubricating oil additives were tested in the friction and wear test machine. The results indicated that good 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 Cu is: Wt_Caco3 % Wt_cu%=1 : 1. and the total content Wt _{Caco3+ cu} % is about 0.6%.5. The tribological mechanism of nano-particles of CaCO3 and Cu is studied through Scanning Electron Microscope (SEM), Energy Dispersion Spectrum (EDS)and Atomic Force Microscope (AFM). The mechanism of anti-wear and friction reduction has been discussed and individual opinions have been proposed.(1)"tiny polishing": When the machine start to run, Nano-particles of CaCO3 or Cu will polish the micro gibbosity. It makes the friction surface more flatness, so it can reduce the friction factor and the wear value.(2) Nano-particles of CaCO3 and Cu have different functions on the friction surface, CaCCb nano-particles work similar to "tiny ball bearing", which can support loads; and Cu nano-particle can fill in and repair worn surfaces.(3)Only with appropriate proportion, can nano-particles of CaC03 and Cu give fully play to properties of anti-wear and friction reduction. When both nano-particles of CaCC>3 and Cu 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 Cu nano-particles mostly fill in and repair worn surfaces. These two nano-particles alone give neither full play nor co-operating play to properties of anti-wear and friction reduction. In our research, when WtCaco3 % : Wtcu %=1 ? 1, CaCO3 nano-particles work as "tiny ball bearing" on the surface that filled by Cu nano-particle, they give full play to properties of anti-wear and friction reduction.(4) Through friction, the nano-particles of CaCO3 and Cu maybe 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 on friction surfaces.The present study is part of "Research on nanometer particle's tribology mechanism as lubricating oil additives" of project of Shanghai Scientific and Technological Committee and "Nanometer material's application in lubricating technology" of key project of Shanghai Educational Committee. More researches are expectably to be further developed.