Surface Shaping Treatments And Effect On Friction And Wear Properties Of High-Silicon Aluminum Alloy Cylinder Liner

Vehicle lightweight is an important way to save energy.The cylinder liner-cylinder block integration reduces the volume and weight of cylinder block.It is an effective way of energy saving design for medium and small power engines.In order to improve the friction and wear properties,aluminum which covers above silicon particles is removed by surface shaping treatment.Silicon particles are protruding the surface,and the edges of them are sharp.This paper presents three surface shaping treatment,they are traditional chemical etching shaping,new mechanical honing shaping,and laser ablation shaping.The wear tests are perfromed in different patameters of surface shaping treatment.The results present the better parameters and surface shaping treatment.The friction and wear mechanism is analysed in the paper.The main conclusions are as follows:(1)The high-silicon aluminum alloy cylinder liner is chemical etched by 5%NaOH solution at 20 ℃ The protrusion height of silicon particle increases linearly with the increase of chemical etching time.Friction coefficient and weight loss decreases first and then increases with the increase of chemical etching time.When chemical etching time is 2 min(protrusion height of silicon particle is 1.1 μm),the friction coefficient and weight loss are lowest.(2)A new mechanical honing shaping method is proposed,and the new machine is designed.It could achieve rotating and reciprocating motions at the same time with the characteristics of high processing efficiency and low cost.The protrusion height of silicon particle increases linearly with the increase of mechanical honing shaping time.The friction coefficient and weight loss decreases first and then increases with the increase of mechanical honing shaping time,but there is a difference in the shaping time corresponding to the minimum value.When mechanical honing shaping time is 1 min-2 min(protrusion height of silicon particle is 0.5 μm～1.2 μm),friction coefficient is lowest.And when mechanical honing shaping time is 2 min-3 min(protrusion height of silicon particle is 1.2 μm～2.5 μm),weight loss is lowest.When mechanical honing shaping time is 2 min(protrusion height of silicon particle is 1.2 μm),the friction coefficient and weight loss are in a lowest range.(3)A new laser ablation shaping method is proposed.The protrusion height of silicon particle increases linearly with the increase of laser power,and it decreases linearly with the increase of laser scanning speed.Friction coefficient and weight loss decreases first and then increases with the increase of laser power or laser scanning speed.When laser power is 1000 W and laser scanning speed is 600 mm/min(protrusion height of silicon particle is 1.2 μm),the friction coefficient and weight loss are lowest.(4)The three surface shaping treatments all can expose the silicon particles on the surface of cylinder liner.That prevents the contact aluminum from piston ring.The concave shape of the aluminum on the surface can serve as an oil storage reservoir to enhance lubrication.The edges of silicon particles are sharp by chemical etching shaping.The edges of silicon particles are rounded but with burr by mechanical honing shaping.Mechanical honing shaping owns high processing efficiency and low cost.The edges of silicon particles are rounded but without burr by laser ablation shaping,but laser ablation shaping owns low processing efficiency and high cost.The friction coefficient and weight loss are lowest by laser ablation shaping in three surface shaping treatments.When the protrusion height of silicon particle is 1.1 μm-1.2 μm,the friction and wear properties of high-silicon aluminum alloy cylinder liner are excellent by chemical etching shaping or laser ablation shaping.By mechanical honing shaping,the radius of curvature of rounded edges is larger.When the protrusion height of silicon particle is 0.5 μm～1.2 μm,the friction properties are excellent by mechanical honing shaping.And when the protrusion height of silicon particle is 1.2 μmΦ2.5 μm,the wear properties are excellent.Mechanical honing shaping owns larger machinable range.(5)The result of flow field analysis shows the silicon particles with rounded edges reduce the probability of eddy current.Lubrication oil presents a good bearing effect.The lubrication is improved.Friction coefficient is reduced.The result of contact stress analysis shows the silicon particles with rounded edges reduce contace stress and friction force,and reduce the probability of breakage.The friction coefficient and weight loss are reduced.The silicon particles with rounded edges exposes on the surface,this structure improve the friction and wear properties of high-silicon aluminum alloy cylinder liner.