Study On Tribological Mechanism Of WS₂ Submicron Particle And Preparation Of High Performance High Temperature Grease

Research and development of high performance high temperature grease has important significance to lubricate the equipment at high temperature. In this paper, a new lubricating material-WS₂ submicron particle is used as additive of high performance high temperature grease and its effects on anti-wear, antifriction and extreme pressure in grease are researched and the high temperature bearing bed test is carried out, the friction surface is analyzed with EPMA and AES. To solve the problem of the microscopic dispersing the submicron particles in grease, Ultrasonic method is used. According to the results, lubrication mechanism of WS₂ submicron particle in high temperature in grease and disperse mechanism of ultrasonic dispersing to submicron particle in grease are analyzed, and two kinds of high performance WS₂ high temperature grease which approach international advanced level are presented.Main research findings of this paper are as follows:1. The results of experiment show that WS₂ submicron particle can enhance the tribology property, including anti-wear, antifriction and extreme pressure, of two main high temperature grease-lithium complex grease and complex calcium sulfonate grease. Adding proper WS₂ submicron particle into the grease used in rolling bearing can reduce the friction factor, consumption, wastage of grease and prolong the working life of grease. It is also found that the lubrication property of WS₂ submicron particle is much better than that of graphite and MoS₂.2. The best proportion of submicron particle is related to soap's fibre structure of grease. In lithium complex grease, some WS₂ submicron particle is blocked in reticular soap fibre and is not into lubrication, so the best percent should be higher and is about 1.5%; In calcium sulfonate complex grease, WS₂ submicron particle is only mixed with nodular soap fibre and is all into lubrication, so the best percent should be lower and is about 1%.3. It is discovered that, under a lower temperature, the metal is lubricated mainly by WS₂ adsorption membrane which is formed between metal friction surfaces besides crystal interior layer slipping of WS₂ submicron particle in the grease. The adsorption membrane cover proportion and thickness are the key to affect the lubrication effect, because WS₂ adsorption membrane cover proportion is higher and WS₂ adsorption membrane is thicker than that of MoS₂ under the same condition.4. It is discovered that, under a higher temperature, the friction and wear are reduced mainly by chemical film which is produced by the friction chemical reaction of friction pairs' surface. In the steel-steel friction, the forming process of this chemical film is: the WS₂ is decomposed into W and S^2- with friction heat. then the W spreads and deposits on metal surface, simultaneously the anti-wear and antifriction ingredients, such as FeS is produced by reaction of S and substrate metal Fe, not only is the direct contact between friction surface prevented, but also the metal has higher beating capacity, which limits the elastic deformation and plastic deformation caused by shear stress to lubricating film region. Thus effectively restrains the friction surface coherence to wear and to contact wearily, so the friction surface is well protected. Chemical film thickness is the key factor to lubrication effect. Because the chemical film is much thicker than the film produced by MoS₂ under the same condition, and has better antiwear, antifriction and extreme pressure performance. Meanwhile, the relation between chemical film thickness and working temperature is presented, which shows that the chemical film becomes thicker as the working temperature rises, and start to drop when it achieves a certain temperature.5. It is discovered that, a little oxidized resultant WO₃ which is produced by WS₂ submicron particle in beating grease under high working temperature, is smaller than 100nm spherical particle, can act as ball bearing and has good friction performance.6. For the first time, ultrasonic dispersion technique is introduced to disperse submicron solid additive in grease. Ultrasonic wave have the sonic flow to stir and cause grease cavitation soaks the collapse to produce the instantaneous high pressure, disperses submicron solid additive in grease equably at micro level, and enhances the lubricating properties of grease.7. Take WS₂ submicron particle as the main additive, introduce ultrasonic dispersion technique, and develop high performance WS₂ lithium complex grease and high performance WS₂ calcium sulfonate complex grease, which can achieve the advanced level at whole performance, some performances excels overseas same kind products. Indicated in the factory practical application situation, independently develops high performance WS₂ grease puts down work in the high temperature makes the situation be good, can meet the requirement of production practice, has replaced some import grease, and has exported to some countries and areas, owing to good economical benefits, is worthy to extending use in the high temperature working conditions.