Studies On Lubrication Properties Of Lithium Based Grease

Grease presents widespread application due to its specific two-phase structure and excellent lubricity. The manufacturing process and the formula are critical to the properties of the grease. The film-building properties of grease is important to understand its lubricating mechanism. In this paper, glycerol is used as the only additive and the lubricating properties of grease samples are examined experimentally. The main work is listed as following:(1)The grease samples are prepared and the process is strictly controlled with different proportion of glycerol as additive.During the manufacturing of grease samples,the affecting factors of temperature,time and cooling speed are considered and the effect of glycerol as an additive on their physical properties is studied. The results show that glycerol hardly influence the consistency of the grease and can lead to higher evaporation and bleeding ratio while lowering dropping point.(2) The film building properties of the grease is studied in a flat-on-flat conformal contact.The time effect is examined firstly. It shows that the film thickness drops significantly at first and then reaches a stable value and the original grease supply exerts little influence on this stable film thickness. Comparing the film thickness by grease and base oil, it shows that with replenishment, the grease can form thicker film. Under low load scale, the film thickness drops with increasing load and the effect becomes less evident when the load increases.(3) The film building properties of the grease is studied in ball-on-disk non-conformal contact and the preliminary theoretical analysis is given.From the results by dichromatic interferometry, it can be seen that grease forms thicker film at low speed, and with further increase in speed the film thickness drops at first and then increases. When the speed is higher, starvation will occur and the film thickness drops. In addition, the structure of the lithium soap will affect the film building properties too.The simulation shows that the film drops with the revolation and it has relation with the Hertz diameter, inlet distance, speed, load and so on.(4) In room temperature, glycerol as additive exerts little effect on the lubricating film under flat-on-flat contact. The film thickness will increase with higher proportion of glycerol at low speed under ball-on-disk condition.(5) The friction and wear property of the grease samples are studied.The results from four-ball wear test machine and UMT-3 show that glycerol as additive can generate low friction and improve the anti-wear property of grease to some extent.