Research On Laser Texturing And Coating Technology Improving Tribological Properties Of Piston Rings

The lost caused by friction and wear is huge. There is about 30% power of automobile engine lost because of friction,19% of the power loss is come from the piston ring-cylinder liner pair. This important pair of engine often damaged because of wear. In this paper, the surface micro structure of piston rings is changed in order to change lubrication regime of surface, and wear resistant and lubricant film is add into the surface, to improve the wear resistant property.Using a Nd:YAG pulsed laser to texture the out surface of piston rings, then get microdimple array with different diameter, depth, density. The textures with different parameters are shown as follows:dimple diameter(125μm,150μm,200μm),dimple depth(25μm,40μm,55μm), dimple density(2.1%～11.04%). Simulateing the reciprocating motion of piston rings-cylinder liner pair, test tribological properties of the pair on a self-made friction and wear testing machine, and find the optimum parameters.Electroplate Cr film with a thickness of 40μm on the out surface of piston rings. Then texture the Cr coated rings. Make Ag film with a thickness of 60μm on the surface of textured piston rings by chemical depositing. Observe the surface and section of films by optical microscope and SEM. Analysis the phase by XRD and EDS. Test the tribological properties of the coated/texturing cooperating effect pair. Then observe the wear truck morphology by optical microscope and SEM.The test shows that the tribological property of the pair is proved by laser texturing. In oil lubricating condition, the friction coefficient decreased about 15%～40%, wear rate decreased about 50%, its wear life is prolonged 2 times.There are optimum parameters that make the pair show the best tribological property:Under low load, the optimum diameter is 150μm, optimum depth is 35μm. Under high load, the optimum diameter is 200μm, optimum depth is 50μm.The optimum density is 4.9%.The wear rate of Cr coated/texturing piston rings decreased two orders of magnitude, while friction coefficient decreased 20%.The optimum density of Cr coated/texturing cooperating action is 4.9%, which is the same as texturing action alone. The wear rate of Ag coated piston rings increased one order of magnitude, while friction coefficient decreased 20%～50%。Piston rings with texturing and Ag coatings cooperating effected, its friction coefficient decreased 16%～33%, the wear rate decreased 14%～60%, its wear life prolong 3 times.Compared to surface texturing and coatings action respectively, the effect of texturing and coating cooperating action can improve the tribological properties of piston rings-cylinder liner pair more effectively.