Research On Friction And Wear Behavior Of Cylinder Liner With MoS₂ Deposited On Microtextured Surface

The frictional pair of piston ring and cylinder liner(PRCL)is one of the important mating motion pair in the marine diesel engine.As the enhancement of the average effective pressure and other strengthening parameters in the power cylinder,it gradually emerges the friction and wear problems,such as friction power consumption,severe wear damage.The combination of surface micro-texture and solid lubricant was applied on the surface of cast iron cylinder liner.This multiple lubrication structure which using micro-texture filled with molybdenum disulfide(MoS2)can effectively improve the friction and wear performance of PRCL.In this paper,boron-phosphorus alloy cast iron cylinder liner was studied.MoS2 tilled microtextured cylinder liner was prepared by reciprocating electrolyte jet with prefabricated-mask(REJP)and electrochemical deposition technology.According to the working condition of PRCL near the top dead center area,the friction and wear behavior of MoS2 filled microtextured cylinder liner was studied by changing the working condition,such as load,temperature and starved lubrication.The factors including the micro texture,MoS2 solid lubricant and ZDDP additives were analyzed to acquire the synergistic action in terms of the improvement of friction and wear performance.Most of the results are as follows:(1)Boron-phosphorus alloy cast iron cylinder liner was studied.The micro texture on the cylinder liner was prepared by REJP technology.Then MoS2 was uniformly filled in the micro-textures by electrochemical deposition technology,and micro textured cylinder liner filled with MoS2 was prepared.(2)Under different loads(25MPa to 75MPa),friction coefficient and wear depth of the microtextured cylinder liner filled with MoS2 were always smaller than those of the microtextured cylinder liner.As the load was increased,friction coefficient of both textured cylinder liners firstly decreased and then increased.Friction coefficient of both textured cylinder liners reached the lowest at 50 MPa and the difference is the largest at 75 MPa.The increasing load promoted the tribo-chemical reaction between the ZDDP additives and the textured surface.Compared with the microtextured cylinder liner,microtextured cylinder liner filled with MoS2 continuously released MoS2 out of the micro-textures which was helpful to the ZDDP tribo-chemical reaction.This MoS2 releasement also reduced the adhesive worn degree under high contact stress areas.(3)Under different temperatures such as 150?,200? and 250?,friction coefficient and wear depth of the microtextured cylinder liner filled with MoS2 were always smaller than those of the microtextured cylinder liner and the values were minimum at 250 ?.Based on the surface analysis of microtextured cylinder liner filled with MoS2,the tribo-chemical reaction of ZDDP was accelerated as the temperature increased.ZDDP was basically decomposed and consumed when the temperature was 250?.The oxidation action of MoS2 distributed on the worn surface was very serious at 200?,but the oxidation action weakened when the temperature raised to 250?.This may be due to the decomposition of ZDDP which inhibited the oxidation process of MoS2.Meanwhile,the micro-acid environment formed by MoS2 oxidation also helped the reactive speed between ZDDP and cast-iron surface.All of the synergetic action improved the friction and wear performance at high temperature.(4)In the starvation experiment,the anti-scuffing time of the microtextured cylinder liner filled with MoS2 was 46.58%longer than that of the microtextured cylinder liner.Compared with microtextured cylinder liner,friction coefficient of microtextured cylinder liner filled with MoS2 was also much lower during the starved period.MoS2 filled micro-textures can continuously release MoS2 to the worn surface after cutting-off oil,even at the extending period of scuffing wear.This MoS2 distribution inhibited the initiation period of micro-adhesive expansion,prolonged the consumption rate of tribo-chemical film and avoided large area damage of cast iron cylinder liner.