Research On Tribological Performance Of Tannins As A Water-based Lubricant Additive

With the depletion of oil resources,energy crisis and serious environmental pollution,the use of water-based lubrication began to gradually replace oil-based lubrication in some areas.Because of the advantages of low price,convenient storage and transportation,wide resources and so on,water-based lubrication is an important direction in the field of mechanical field and future development.In view of the poor lubrication performance and corrosion resistance of water-based lubricants,it is necessary to add various water soluble additives in water to improve the tribological properties of water.In recent years,it has been found that water-soluble polymer can not only improve the viscosity of water for forming thicker oil film,it can also adsorb on the metal surface to prevent the direct contact between the friction pairs.Therefore,the tribological properties of water can be greatly improved by adding water soluble polymer.On the other hand,with the development and utilization of marine resources,the research and exploration of the tribological properties of materials in the seawater environment are more and more concerned.However,the research on water-based lubrication in the seawater environment is not well available.Thus,in the thesis,we try to use the tannic acid in nature as a lubricant additive.The tribological properties of tannic acid as water-based lubricant additive were analyzed,and the lubrication mechanism was analyzed.The results is important to provide some reference and reference for obtaining environmentally friendly water-based lubricant.The experiment achieved some stage results,and it was found that:（1）A certain concentration of tannic acid solution can play a good role in reducing friction and wear in the ceramic Si₃N₄ ball-stainless steel friction pair.However,when the tannic acid reaches a citric concentration,it will accelerate the corrosion of stainless steel,resulting in the increase of wear.The main reason is that the tannic acid molecules can be adsorbed on the stainless steel surface to form a chemical conversion film for reducing friction and wear.In addition,the study found that tannic acid as a water-based lubricant additive can play a good antifriction and lubricating role in different load and acid-base environment,where hydrogen ions play a crucial role in the formation of conversion film on stainless steel surface by tannic acid molecules.（2）The aqueous solution of tannic acid plays a good role in reducing friction and wear in the ceramic Si₃N₄ ball-aluminum bronze friction pair.With the increase of tannic acid concentration,the lubrication performance is better.Similarly,the ceramic Si₃N₄ ball-aluminum bronze friction pair,tannic acid as a water-based lubricant additive,in different load,speed and acid-base environment also have obvious antifriction and lubrication effect.The experimental results show that the hydrogen ions in tannic acid solution can inhibit the formation of the conversion film on the surface of aluminum bronze by tannic acid molecules.（3）Tannic acid solution shows better lubricating performance for ceramic Si₃N₄-stainless steel and Si₃N₄-aluminum bronze friction pairs in presence of simulated seawater.