Effect Of Laser Microtexturing On Tribological Properties Of Boron Phosphorus Alloy Cast Iron Cylinder Liner

There are many types of friction pairs in diesel engines,among which the cylinder liner-piston ring friction pair is one of the most important components of diesel engines.The friction loss caused by the cylinder liner and piston ring friction pair accounts for more than 40%of the total loss.Its surface tribological behavior has a very important impact on the performance and efficiency of the diesel engine,as well as economy,stability,pollution emissions and service life..With the development of diesel engines in the direction of energy saving and emission reduction and high indicators,higher design requirements are placed on the tribological performance of the cylinder liner-piston ring friction pair.The laser micro-texturing processing technology can not only effectively improve the tribological performance of the friction pair,but also has the advantages of high processing efficiency,high precision,and small pollution during the processing process,so it has received extensive attention.In this paper,the Nd:YAG laser is used to perform laser texture treatment on the surface of the boron-phosphorus alloy cast iron cylinder liner sample.Through calculation,the laser ablation threshold of the boron-phosphorus alloy cast iron material is obtained.On this basis,the effect of laser pulse number,energy density and defocusing amount on the micro-pit geometry is experimentally studied.Optimized laser parameter design,processed texture samples with different geometric shapes(including diameter,depth,angle and area occupancy)on the surface of boron-phosphorus alloy cast iron cylinder liner The oil-rich friction and wear performance and lean oil anti-scuffing performance of different texture geometry parameters.Observation and analysis of the surface micro-morphology of the friction-damaged specimens reveals the micro-texture anti-friction mechanism.The main research results of the paper are as follows:(1)According to the relationship between the pit diameter and the pulse energy of microsecond laser,the ablation threshold of boron phosphorus alloy cast iron under the action of microsecond laser is 8.4J/cm2,and the cumulative coefficient is 0.87.With the increase of laser energy density,the diameter of micro pits increases,but the diameter and depth of micro pits decrease with the increase of laser energy density.With the increase of the number of pulses,the depth of the crater increases linearly,and the increase of the number of pulses has little effect on the diameter of the crater.With the increase of the negative defocusing amount,the diameter and depth of the micro pits increased.When the negative defocusing amount reached-1 mm,the depth of the micro pits reached the maximum.(2)In the oil rich friction and wear experiment,it is found that with the increase of micro texture diameter,area share and depth diameter ratio,the friction coefficient of cylinder liner piston ring decreases first and then increases,and the wear amount also decreases first and then increases;there is no definite rule for the influence of micro texture angle on the fiiction coefficient and wear amount.When the diameter of the laser micro texture is 130 ?m,the ratio of depth to diameter is 0.3,the area share is 15%,and the angle is 0°,the friction coefficient of the cylinder liner piston ring friction pair is the smallest,the wear amount is the smallest,and the friction reduction effect is the best.(3)It is found that with the increase of micro texture diameter,area share and depth diameter ratio,the anti-scuffing time of cylinder liner piston ring increases first and then decreases.When the diameter of laser microtexture is 130 ?m,the ratio of depth to diameter is 0.2,the area share is 15%,and the angle is 0°,it has the best anti-scuffing effect.