| As a new type of the technology, the solid-oil compound lubricating technology shows a wide application prospect in the high technology fields. In present work, compound lubricating sistem of polyimide bonded solid lubricant coatings and several oils was selected as the research object, and the tribological behaviors of polyimide bonded MoS2 solid lubricant coating, polyimide bonded graphite solid lubricant coating and polyimide bonded PTFE solid lubricant coating under dry sliding and lubrication of kerosene oil, diesel fuel, paraffin liquid and lubrication oil were investigated. The effects of testing conditions including applied load and sliding speed and friction couple on tribological performances of the corresponding composite coatings were examined, and the mechanisms of the coating-oil compound lubricating were preliminarily discussed. The main results and conclusions are as follows:1. For the coating against counterpart metal ring form, the friction and wear behaviors of three polyimide bonded (MoS2, graphite and PTFE) solid lubricant coatings in four different oils (Kerosene RP-3, Lubrication oil SG 15W-40, Diesel fuel O# and Paraffin liquid) were investigated by MHK-500 friction-wear tester. Compared with the dry friction condition, the friction coefficient of the coatings under lubrication of four oils greatly decreases and their value are about 0.08, whereas the wear life of the coatings increases by 1-4 orders of magnitude. The wear-resistance properties of three coatings at high sliding speed and low applied load are better than that at low speed and high load under the same lubrication condition. The variation of the wear-resistance properties of the coatings under lubrication of kerosene is most obvious. Three coatings reveal different wear-resistance properties under the same testing condition, and the polyimide bonded PTFE solid lubricant coating shows the best wear-resistance properties among three coatings.For the coating against counterpart metal block form, the friction and wear properties of bonded PTFE solid lubricant coating under lubrication of diesel fuel were also investigated by MHK-500 friction-wear tester. The results show that the antifriction properties of the coating under oil lubrication condition are better than under drv friction condition. Bonded solid lubricant coating exhibits much better wear-resistance properties at low applied load and low sliding speed under oil lubrication. The friction and wear properties of bonded PTFE solid lubricant coating under lubrication of diesel fuel in the coating against counterpart metal ring form are obviously better than that in the coating against counterpart metal block form.2. There are many cracks or micro-cracks on the worn surfaces of the coatings under lubrication of kerosene with low viscosity, whereas the worn surfaces of the coatings under lubrication of diesel fuel and paraffin liquid with moderate viscosity are glossy. Under lubrication of lubrication oil with high viscosity, many cracks or micro-cracks form on the worn surfaces of the coatings. There are deep plough grooves in the counterpart metal ring's surfaces under lubrication of kerosene with low viscosity. Under lubrication of diesel fuel, paraffin liquid and lubrication oil, there are slight plough grooves in the counterpart metal ring's surfaces, whereas the plough grooves in the counterpart steel ring's surfaces become deeper with the increase of the oil's viscosity. These are probable reason that oil film of the oil with low viscosity on the surface of the friction pair is insufficient, and cooling effect of the high viscosity oil with low flow is poor.3. XPS analyses of the counterpart metal rings' surfaces under lubrication of kerosene and diesel fuel indicate that there are the formations of MoS2 transfer films in the counterpart metal rings' surfaces. The physical adsorption film is the main type of lubricating oil films in friction process.
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