| The higher wear resistance and lower friction cylinder liner is required with the ever-increasing of the power density of the diesel engines.The good adhesive force with the substrate and excellent tribological properties make the FeNi Alloy electroplated coating a good choice for the surface improvement of the iron cast cylinder liner.The in-situ friction can be realized by using the micro-texture coupling with the solid lubricant,as a result of friction reduction and good lubrication,the cylinder liner with the improved tribological properties will be obtained.Therefore,the investigation on the textured and FeNi Alloy electroplated liner coupling with the solid lubricants will be of great significance in developing the high tribological performance and high power density diesel engines.First,the tribological properties of the FeNi Alloy electroplated liner against the Cr-Al2O3 coated piston ring(CKS)under various conditions(different loads and lubrication states)were systematically investigated on the basis of the friction coefficient and wear rate as well as the time-based scuffing resistant ability.The results show that the FeNi Alloy deposited liner presents the higher friction coefficient by 11-20%,lower wear rate by 11%and longer scuffing-time by 6.5 times compared with the original iron cast liner.Next,the surface of the FeNi Alloy electroplated layer was modified with the purposely designed micro texture coupling with the MoS2 in order to reduce the friction coefficient.The surface texture was fabricated by electrical discharge machining(EDM).The way of filling the MoS2 in the texture was investigated,and the best ratio of MoS2 to lube oil is 10:1.The effect of the texture coupling with the MoS2 lubricants on the tribological behaviors of the liner and the affecting zone of the MoS2 was analyzed,and the optimized distribution of the texture was obtained.Subsequently,with the optimized texture distribution and MoS2 content,the effect of the key texture parameters including the diameter,the depth,density and the relative angle on the friction coefficient and worn surface morphology was studied.With the best combination of the texture distribution and individual texture shape as well as MoS2 content,the friction coefficient is reduced by 7.3%and 11.4%compared with the pure FeNi Alloy electroplated liner and the original iron cast liner respectively.Based on the effect of the effect of the lube oil dosage on the friction coefficient and worn surface,a better understanding of the tribological behavior of the liner under the different lubrication condition such as the dry friction and boundary lubrication as well as mixed lubrication etc has been achieved.Eventually,the model for the effect of solid paticales on the textured surface lubrication was established based on the nature of the MoS2 mixed lube oil.With the model,how the particle diameter and content affect the oil film thickness and bearing capacity on the textured surface,and the effect of particles on the surface pressure distribution were obtained.As the model cannot have a good representation of boundary lubrication,x-ray photoelectron spectroscopy(XPS)was utilized to analyses the chemical component of the worn surface.The results reveal the mechanisms of the formation of the tribo-film originated from the MoS2 and ZDDP additives on the FeNi Alloy electroplated liner. |
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