Study On Fabrication And Tribological Properties Of Micro-pits On Laser Textured Chromium Plated Piston Rings

The internal combustion engine is the main power equipment for transportation and machinery production.The key component piston ring-cylinder liner friction pair has a harsh working environment,and the wear failure accounts for more than half of the friction loss of the whole machine.The friction loss produced by the piston ring-cylinder liner friction pair directly affects the power performance,energy utilization and service life of the internal combustion engine,so it is very important to improve its tribological performance and prolong its service life.Using the laser beam to prepare micro-texture on the surface of friction pair can store lubricating oil,generate dynamic pressure effect,and improve the surface tribological properties of friction pair.It is of great significance to design micro-texture with reasonable feature sizes to exert their antifriction properties.In this paper,laser texturing technology is applied to the surface of chrome-plated piston ring,and the effect of micro-pits texture on the surface of piston ring on the tribological properties of the friction pair is studied through theoretical analysis,simulation,preparation process and tribological experiments.The main research contents and conclusions are as follows:1.Theory and simulation.Theoretical analysis is made on the principle that the oil film in the surface texture of the friction pair produces dynamic pressure lubrication and improves the tribological performance of the friction pair.Based on the N-S equation of fluid mechanics,a three-dimensional cylindrical micro-pits texture model was established.FLUENT computational fluid dynamics simulation software was used to simulate micro-pits texture under the condition of cavitation effect,and the influence of micro-pits morphology,depth and area ratio on the tribological properties of piston ring-cylinder liner friction pairs at different moving speeds was investigated.The study found that the cavitation effect is one of the factors to improve the bearing capacity of the oil film between the friction pairs.And at different motion speeds,the elliptical micro-pits texture is more conducive to improving the tribological properties of the friction pair.By optimizing the characteristic size parameters of elliptical micro-pits at different speeds,it is obtained that the optimal dimensionless depth of micro-pits is 0.5 at low speed and 1 at medium and high speed;the optimal parameter for the proportion of micro-pits area is 15% at low speed,20% at medium and high speed.2.Micro-pits texture preparation technology.Nanosecond pulsed laser was used to prepare elliptical micro-pits texture on the coating surface of chrome-plated piston ring,and the characteristics of single-point multiple processing and laser scanning filling were analyzed.The effect of laser scanning filling process parameters on the size and morphology of elliptical micro-pits on the surface of chrome-plated piston rings was investigated.The results show that increasing the laser power and the number of repeated processing,reducing the scanning speed and the spacing between filling lines can effectively increase the depth of the micro-pits;The long-diameter length of the micro-pits decreases with the increase of laser power,first increases and then decreases with the increase of processing times,and the scanning speed and filling line spacing have little effect on it.3.Tribological test.Under the condition of lean oil lubrication,a reciprocating friction and wear test was designed to study the influence of the area ratio and depth parameters of elliptical micro-pits on the tribological performance of the friction pair under the lean oil lubrication mechanism.The test results show that compared with the smooth samples,the elliptical micropits texture with reasonable geometric parameters can effectively reduce the friction coefficient of the friction pair surface.When the texture area accounts for 20% and the depth is 30 ?m,the friction reduction performance is the best The friction reduction efficiency is about 35%.