Study On Friction And Wear Behavior Of Cylinder Liner Microtextured Surface Caused By Lubricating Oil Degradation

As the heavy-duty conditions for marine diesel engines continue to improve,the tribo-pair of cylinder liner and piston ring(CLPR)begin to have more demands in terms of friction and wear reduction.The preparation of microtextured surface on the cylinder liner is a promising control method that has received increasing attention.The micro-textures are effective in storing abrasive particles to avoid surface abrasive wear and increasing the lubricant film thickness to provide hydrodynamic lubrication,as well as reducing the direct contact area.When degradation of the lubricant occurs,such as high temperature oxidation and diesel dilution,the effect of degraded lubricants on the microtextured surface needs to be considered to support the design of the microtextured cylinder liner.In this thesis,the degraded lubricants were prepared by means of high temperature oxidation and diesel dilution.Compared with nontextured cylinder liner,the friction and wear performance of microtextured cylinder liner were investigated using the degraded lubricants.The worn surface morphology and tribochemical products were analyzed.The purpose is to provide some technical guidance for the micro-texture design.The main conclusions are as follows.(1)For high-temperature oxidized lubricants,compared with the non-textured tribopair,the friction coefficient and liner wear depth of microtextured tribopair decreased,while the ring wear depth increased.The anti-scuffing time of microtextured tribopair increased.As the high temperature oxidation of lubricants increases,the honing pattern on the non-textured cylinder liner gradually disappeared,and the wear scratches along the sliding direction gradually increased.The wear scratches on the microtextured cylinder liner are interrupted by micro dimples,but the edges of the micro dimples were more damaged.Some of the wear particles are stored in the micro dimples.The elements S,P and Zn corresponding to the tribochemical reaction products of ZDDP are presented on the nontextured and microtextured cylinder liner worn surface.(2)For the diesel diluted lubricant,compared with the non-textured tribopair,the friction coefficient of the microtextured cylinder liner decreased,but the wear depth of the microtextured cylinder liner and its mated piston ring increased.The microtextured cylinder liner presents a longer anti-scuffing time at 180°C,but does not present a significantly longer period of anti-scuffing time at 240°C.With the increase of diesel diluted lubricating oil,the friction coefficient of the microtextured cylinder liner first decreases and then increases,the wear depth gradually increases,as well as the anti-scuffing time first increases and then gradually shortens.The wear surface scratches obviously increase.Micro dimples still have the action of wear scar blocking.Besides S,P,Zn and other elements,Ti,Cu and other elements from diesel are also detected on the worn cylinder liner.(3)For the high temperature oxidation + diesel diluted lubricating oil,microtextured and non-textured cylinder liner have a large number of scratches along the sliding direction.Micro textures block the wear marks,and tribochemical reaction products present a large number of white bright spots gathered in the micro dimples.The diesel composition mixed in the degraded lubricant cause a reduction in the proportion of Zn S,emerging more short chain phosphates.