| In the modern coal mining,the transmission gear of the cutting section is the most vulnerable part of the shearer,and its failure has become the key to the mechanization and modernization of coal mining equipment.It is necessary to have research on the lubrication mechanism of low speed heavy-duty gears.Adding nano additives with anti-friction and anti-wear properties to lubricants is of great significance for improving the lubricating performance of shearer gears,preventing early friction fatigue failure of tooth surfaces,and prolonging the service life of gears.This article uses traditional nano-lubricants MoS2 and TiO2.Through L16(45)orthogonal test and improved tests,the optimal modifier composition ratio was obtained.High-performance ball milling with silane coupling agent KH-560 and surfactant Span 80 can greatly reduce nanoparticle agglomeration,increase their lipophilicity,and obtain a MoS2/TiO2 modified powder with good dispersion.The tribological properties were investigated by several groups of tests.The main conclusions are as follows:(1)The wettability of the obtained MoS2/TiO2 modified powder was tested.The results showed that the nanoparticles changed from lipophilic to hydrophilic and hydrophobic,and the lipophilicity was significantly improved.From the microscopic morphology of the powder,it can be seen that the modified MoS2 and TiO2 are respectively agglomerated.After the modification,TiO2 was dispersed among the MoS2 layers,and there was almost no agglomeration tendency of the nanoparticles.The MoS2/TiO2 modified powder was analyzed by Fourier transform infrared spectroscopy.The results show that the surface of MoS2/TiO2 modified powder is coated with a large amount of Span-80 and a small amount of KH-560.(2)Using MoS2/TiO2 modified powder as solid lubricant,it is found that the wear degree of the friction pair containing MoS2/TiO2 modified powder is obviously lower than that of pure dry friction condition.Nano particles play a role in grinding and polishing the convex peak of the steel sheet.Nano particles play a role in grinding and polishing the convex peak of the steel sheet.At the same time,the nano particles have a chemical reaction during the friction process to produce a protective wear resistant reaction film,so that the MoS2/TiO2 modified powder can effectively reduce the wear range of the friction pair.(3)The wear resistance test results of the four-ball tester show that the MoS2/TiO2 modified powder can play a good anti-friction and anti-wear effect in three different synthetic base oils.For PAO,when the load increases to a certain size,the addition of nanoparticles will no longer play a role in anti-friction and anti-wear,and even exacerbated wear.Through testing the extreme pressure properties of oil products,it can be found that the addition of MoS2/TiO2 modified powders increases the maximum no-bite load of the lubricating medium to varying degrees.(4)The viscosity of the lubricating medium has a great influence on the test.When the viscosity of the lubricating medium is low,the lubrication state is poor,but the nano-particles improve the lubrication performance of the low viscosity lubricating medium more obviously.The action mechanism of nano particles is that MoS2 is deposited and adsorbed on the surface of the friction pair,forming a layer of physical adsorption film.The spherical TiO2 plays the role of bearing and turns the sliding friction into rolling friction.Nanomaterials are extruded and leveled under the action of high load,repairing and leveling the surface.These nanoparticles form a new sliding surface between the friction pairs,reduce the direct contact on the metal surface,and play a role of anti-friction and anti-wear. |
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