Lubrication Mechanism of MoDDP/CaB Lubricant Additive under Heavy Load,Variable Speed,and Impact Conditions
To solve the problem of equipment failure and even safety production accidents caused by lubrication failure under adverse working conditions,and to further enhance the stability and safety of mechanical equipment operation,the anti-wear and friction reduction effect of single and composite lubricant additives of calcium borate(CaB)and molybdenum dialkyl dithiophosphate(MoDDP)under heavy load,variable speed,and impact conditions were investigated.The results show that the organic molybdenum additives can effectively reduce the friction factor and wear spot diameter compared with the base oil.The 1.5 wt.％MoDDP additive exhibited the best friction reduction and anti-wear performance,reducing the friction factor by 41.0％and the wear spot diameter by 48.9％compared to the base oil.Among the four oil samples,the 1.5 wt.％MoDDP/3.0 wt.％CaB composite lubricant additive showed the best friction and anti-wear effects,reducing the friction factor by 55.0％,62.7％,and 65.1％and the wear spot depth by 75.8％,78.8％,and 80.0％,respectively,compared with the base oil at different rotation speeds.With the increase of rotation speed,the friction factor curves of base oil,2.0 wt.％CaB,and 1.5 wt.％MoDDP fluctuated and the maximum wear spot depth of base oil,2.0 wt.％CaB,and 1.5 wt.％MoDDP also tended to increase with the rotation speed,while the friction factor curves of 1.5 wt.％MoDDP/3.0 wt.％CaB composite lubricant were always the most stable.The surface wear spots of the specimens lubricated by 1.5 wt.％MoDDP/3.0 wt.％CaB composite lubricant at different rotation speeds were uniform,and no significant changes in the wear spot depth were observed,indicating that the rotation speed under heavy load has a slight effect on the friction reduction performance of 1.5 wt.％MoDDP/3.0 wt.％CaB composite lubricant.The composite lubricant additives exhibited stable and excellent friction reduction and anti-wear performance under heavy loads and variable-speed operating conditions.Under a 50 N impact load,the 1.5 wt.％MoDDP/3.0 wt.％CaB additive showed the best friction reduction effect,reducing the friction factor by 66.7％.The typical friction factor curves of 1.5 wt.％MoDDP/3.0 wt.％CaB composite lubricant exhibited the least fluctuation.The 1.5 wt.％MoDDP/3.0 wt.％CaB composite lubricant additive exhibited the smallest wear spot depth and the smallest increase in depth of wear spot under a 50 N impact load,which can reduce the wear spot depth by 76.5％compared to the base oil.The comparisons of wear spot depth and morphology show that the 1.5 wt.％MoDDP/3.0 wt.％CaB composite lubricant can play an excellent anti-wear effect under low speed,heavy load,and impact conditions.The MoDDP/CaB composite lubricant additives can generate a metal composite layer containing C-C,Fe2O3,FeB,and MoS2 during the lubrication process.The CaB and MoDDP in the composite lubricant additive can promote each other's reactions and increase the generation of FeB/MoS2 lubricating films.Compared to a single additive and base oil,the composite lubricant additives showed better self-healing performance and synergistic efficacy,forming a lubricating film with a high load-bearing capacity and improving the anti-wear and friction reduction performance of the composite lubricant.The preparation of MoDDP/CaB composite lubricant additives can fully synthesize the stable and excellent lubricating properties of antioxidants,extreme pressure,and wear agents,and the results can provide data and theoretical support for the wide application of composite lubricant additives.
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