Experimental Study Of Composite Solid Lubricating Film

Experimental study of composite solid lubricating film is based on the proposition to reduce the excessive wearing rate of SDZH2-10 valve electrical device's worm wheel and worm shaft.When the transmission ratio of SDZH2-10 valve electrical device's worm wheel and worm shaft is 70, the load is about 4137N, the relative slide speed is 5.3m/s, and the worm wheel and worm shaft material is ZCuAl9Fe4Ni4Mn2, 40Cr steel ( HB250-280) respectively, the device will start up and stop frequently with friction temperature staying high and lubricant hardly in effect. In this situation, the oil-free frictional transmission will be turned into dry-friction or edge lubrication state, which will cease to be effective due to the oxidative wear and adhesive wear. Under such condition, solid lubricant is a good choice due to the fact that ordinary solid lubricant such as graphite and MoS₂ cannot be supplied continuously, which lead to short service life owing to the requirement on adhesion between the material itself and the basal body. To enhance the adhesion between solid lubricating film and the basal body, we need to pay attention to the following:On the one hand, by phosphating its surface, the adhesion and service life can be improved. In this article, the optimal phosphatization formula has been determined after a series of tests on phosphating film's microstructure, thickness, tribology property, etc. The optimal formula sets as: Zn(NO₃)₂ 20g/L, Mn(H₂PO₄)₂ 60g/L, Mn(NO₃)₂ 15g/L, Ni(NO₃)₂ 2g/L, Ca(NO₃)₂ 2g/L,tartaric acid 1g/L, a small amount of additives. The best phosphating technique parameter sets as: temperature between 60 to70℃, duration of 10 to 15 minutes. The wear of the post-phosphating surface is significantly slighter than the phosphating-free sample. The phosphating film is combined with basal body through chemical bond, thus having an adherence of 47.47N. Through the coating adjustment techniques, the frictional coefficient of phosphating film dropped to 0.3 from 0.8.On the other hand, the adhesion and service life can be enhanced by adding a small portion of self-made micro-nano K₂Ti₄O₉ whiskers into graphite-MoS₂ solid lubricating film. Through scanning electron microscope observation, component analysis, and tribology property test, it reveals that the wearing life of combined solid lubricating film with K₂Ti₄O₉ whiskers added is 2.4 times of the K₂Ti₄O₉ whiskers-free one under 300℃, and 3 times under 500℃. Meanwhile, the wearing rate was significantly lower after adding K₂Ti₄O₉ whiskers.Tribology property test and grinding crack test were conducted after using phosphating pre-process with self-made micro-nano K₂Ti₄O₉ whiskers added (known as composite solid lubricating film). It is demonstrated that the wearing life of composite lubricating film is three times of the unphosphated solid lubricating film, the friction coefficient is only less than half of the unphosphated one, and the adhesion between composite solid lubricating film and the basal body is increased to 11.29N from 5.32N when the phosphating-free solid lubricating film was used. By using composite solid lubricating film, the adhesion with the basal body can be improved so as to maintain the sustainability and duration of solid lubricating film. Thus, wear reduction can be achieved by ameliorating the original wearing state in the valve electrical device's worm wheel and worm shaft with heavy load, high sliding speed, high pressure and high friction temperature.In the meantime, in order to study the lubricating property of composite solid lubricating film under high temperature and high pressure condition, experiment on high-speed steel tool's cutting property was conducted including a series of tests on tribology property, wear morphology, cutting property, abrasion loss, etc. It shows that, after the feed rate reaches 0.3 mm/r, the wear of the composite solid lubricant film coated tool begins to reduce with the increase of the feed rate, at 0.5mm / r, the wear is only a half of kerosene cutting fluid. When the cutting speed is 9-36m/min, the cutting property of composite film+kerosene is better than the kerosene one. When the feed rate is 0.2-0.7mm/r, the wear of composite film+kerosene is less than the kerosene one, and only one third of the kenosene's wear when the feed rate is 0.5mm/r. When the cutting speed is 18-36m/min the wear of composite film+kerosene is less than the kerosene one, and only one third of the kenosene's wear when the cutting speed is 36m/min. It shows that high-speed steel cutting tools coated with composite solid lubricating films can significantly improve the tool's cutting property, service life and machining accuracy.By using composite solid lubricating film, multi-synergistic effect can be achieved. Thus, under extreme friction state of heavy load, high pressure, high friction temperature, adopting composite solid lubricating film technique can enhance lubrication condition, meanwhile improving the sustainability and duration of solid lubricating film, this composite solid lubrication film can improve the worm origin lubrication status and reduce the worm wear When the transmission ratio of SDZH2-10 valve electrical device's worm wheel and worm shaft.