Effect of Flash Temperature on the Formation of ZDDP Reaction Film

As the most common additive of engine lubricating oil, zinc Dialkyldithiopho- sphate (ZDDP) has not yet found a suitable substitute. It is generally considered that ZDDP film is produced at a higher macro environment temperature, while the influence of local flash temperature change on the growth of ZDDP friction film is ignored. Based on the thermal activation theory of stress promotion and the calculation model of lubrication interface flash temperature, this paper focused on the ball-disk slip-rolling friction experimental research, and conducted the analysis of interface flash temperature on the ZDDP friction film formation characteristics. The flash temperature and its distribution under different interface slip roll ratios were calculated under the condition of constant load and ambient temperature. At room temperature the variation of friction coefficient of ZDDP lubricant with different slip roll ratios was measured by ball-on-disk experiment at room temperature, and compared with thecalculated flash temperature model, the effect of flash temperature on the growth of ZDDP reaction film can be obtained. In order to improve the high friction caused by ZDDP film, the synergistic effect of calcium stearate and ZDDP was tested. The results showed that the increase of interfacial flash temperature can also produce ZDDP friction film of a certain thickness. The synergistic friction reduction experiments of calcium stearate lubricant and ZDDP showed that calcium stearate lubricant improved the friction performance of ZDDP friction film, and the boundary film formed by calcium stearate lubricant and ZDDP effectively reduced the high friction caused by ZDDP.