To discuss the thermal aging behavior of lithium-based grease under high-temperature working conditions,the lubricating grease samples were prepared using different mineral oils and PAO as the base oil and lithium 12-hydroxystearate as the thickener.Based on the use of self-designed infrared spectrum quantitative analysis equipment,the static thermal aging method were applied to simulate and systematically study the thermal aging process of lithium-based grease of different base oil types under different aging temperatures.This aimed to explore the structural change and its rule of key component molecules in lubricating grease during aging process,and through analysis,set up the comprehensive performance index E that can effectively evaluate the thermal aging degree of lubricating grease.The results show that the oxidation,nitrification and sulfurization of the base oil occur firstly in the thermal aging process of lithium-based grease,and the degradation of the thickener occurs as the aging degree increases.For the 1 # lithium-based grease sample under static thermal aging at 140 ℃,when the E value rises to 1-23 and 23-38 times as compared with the new grease,it is in the primary oxidation stage and on-platform oxidation stage,respectively.Based on other physical and chemical indicators,the first two stages are the main factors that affect the service life of lubricating grease.With the increase of aging time,E values continues to rise and then the structure of lubricating grease fails to be degraded.Besides,the aging degree of lubricating grease is accelerated with increasing temperature.The base oil type has certain influence on the aging rate.The regular long-chain alkane structure of polyalphaolefin can maintain the stability of thickener structure in the late aging process,and the prepared grease samples have better high temperature performance.
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