Preparation And Tribological Properties Of PAO3 Based Magnetic Fluid

Traditional mineral lubricants are difficult to meet the development needs of aviation industry technology,and polyalphaolefin（PAO）has become one of the most widely used aviation lubricating base oils.However,the research on synthetic base oils in China started relatively late and has become a bottleneck in the development of China’s aviation industry.Nanolubricating additives can improve the lubricating performance of base oils,among which Fe₃O₄nanoparticles have advantages such as chemical stability and superparamagnetism.The magnetic fluid formed by dispersing Fe₃O₄into lubricating oil can be manipulated through electromagnetic fields,which is expected to improve the lubrication conditions of aviation lubricating oil shortage or oil shortage.In addition,there are few reports on magnetic fluids as aviation lubricants.Based on this,a magnetic fluid based on domestic polyalphaolefin（PAO3）was prepared and characterized;Subsequently,the tribological properties of PAO3 based magnetic fluids were studied using UMT and a self-made friction and wear test rig;Finally,the lubrication mechanism was discussed.The specific research results are as follows:（1）Fe₃O₄-OA and Fe₃O₄@Cu O-OA nanoparticles were prepared by chemical coprecipitation and sodium oleate（OA）modification methods.The characterization test results showed that OA molecules were successfully grafted onto the surface of the particles;The phase composition of the particles meets experimental expectations;The average particle sizes of Fe₃O₄-OA and Fe₃O₄@Cu O-OA particles are 9.8 nm and 13.8nm,respectively,which are approximately spherical;The specific saturation magnetization of Fe₃O₄-OA is 64.57 emu/g,and the specific saturation magnetization of Fe₃O₄@Cu O-OA is 29.59 emu/g;Using polyisobutylene amine（PIBA）as the particle secondary coating,the dispersion standard of magnetic liquid as a colloidal system in PAO3 base oil has been achieved.（2）When the Fe₃O₄-OA content is 1wt%,the average friction coefficient of the magnetic fluid in 304 steel and 12Cr Ni4A friction pairs decreases by 20%;In GCr15steel and 12Cr Ni4A friction pairs,the average friction coefficient increased by 19%;In Si₃N₄and 12Cr Ni4A friction pairs,the average friction coefficient decreases by 20%,but the wear amount increases.Based on the analysis of wear traces,it is believed that Fe₃O₄-OA has worn the friction surface and promoted the formation of oxide films during the friction process,which has been confirmed.Adding Fe₃O₄@Cu O-OA to PAO3 base oil can reduce the average friction coefficient of aviation gear materials by up to 29.6%and the average wear scar width by up to 49.6%.（3）Under different mass fractions,the optimal content of Fe₃O₄-OA in 304 steel and 12Cr Ni4A friction pairs is 0.5 wt%,the average friction coefficient decreases by50%,and the average wear scar width decreases by 60%;In GCr15 steel and 12Cr Ni4A friction pairs,friction and wear are intensified;In Si₃N₄and 12Cr Ni4A friction pairs,the optimal content of Fe₃O₄-OA is 5 wt%,the average friction coefficient decreases by11%,and the average wear amount decreases by 55%.Under the action of an external magnetic field,the lubricating performance increases when the content of magnetic particles is less than the optimal content,and decreases when the content is more than the optimal content.Under the action of temperature,the tribological properties of PAO3 base oil at-20℃are close to those of PAO3 base oil;At 75℃,the average friction coefficient decreases by 15.3%and the average wear scar width decreases by8.9%.The change in tribological properties of PAO3 based magnetic fluids under experimental conditions is attributed to the change in the adsorption and sedimentation properties of magnetic particles in the magnetic fluid.