Research On Preparation And Properties Of Metal Ceramic Sulfide Solid Lubrication Film

Seawater hydraulic pump is the power source of hydraulic system.The key friction pairs are prone to severe friction and corrosion in seawater service conditions.Regarding this issue,commonly used materials for hydraulic pump were treated by laser cladding-ion sulfurizing process.With the aid of three processes including providing the source of sulfide metal by target,addding metallic elements in the cladding layer,and adding compound in the cladding layer,more than two sulfide solid lubricants were prepared,which had strength of excellent wear-corrosion resistance and self-lubrication properties.What’s more,the process improves the whole life of friction pairs of seawater hydraulic pump.This paper mainly studys the preparation process of more than two kinds of sulfide.The laser cladding was prepared on the surface of 45 steel and A36 steel,SD-Ni55 powder as the material.Low temperature ion-sulfurization process was used after polishing treatment of laser cladding samples.Ion sulphurizing target plays two roles in the process of sulfuriation,the first is the rapid warming,quickly heating the workpiece to sulfurizing temperature and the second is providing active metal or sulfide particles to the surface of the workpiece.The addition of sulfide metal element in the laser cladding layer,regardless its existence form,can be used as the source of suhide in the process of sulfurization.With the help of channel target,molybdenum target and tungsten target,solid lubricating composite layer containing FeS,MoS₂,WS₂ can be obtained on Ni55 cladding layer.MoS₂and WS₂ have strong compressive ability,suitable for high temperature,high speed,high load conditions.Therefore,sulphide compounds can also greatly improve the application scope of the sulfurized layer.Under the condition of dry friction and medium lubrication,the friction coefficient of the composite layer had the trend of firstly increasing and secondly decreasing until stable value.In distilled water lubrication condition,the friction coefficient of solid lubricating composite layer reduced about 45%than in dry friction condition,and the wear loss about 35%.In water lubrication condition,the friction coefficient of composite layer decreased about 64%than in dry condition,the wear volume about 70%.After adding elemental Mo,W or WC alloy in Ni55 powder,the composite layer containing two or three solid lubricating phase（Fe S,MoS₂,WS₂）can be obtained with the aid of channel steel by low temperature ion sulphurization.Under the same friction and wear condition,compared with the matrix and laser cladding,the solid lubricating composite layer has the lowest friction coefficient and wear loss weight,and has the best wear and friction reducing properties.Laser cladding-ion sulfurized solid lubricated composite layer has more excellent properties of antifriction and wear resistance in medium lubrication conditions.This is because the dielectric film is formed under the lubricated friction conditions.Continuous dielectric film makes only parts of the micro convexes of two friction solid surfaces contact,the actual contact area is reduced.Therefore the tribological performance of the composite layer under the condition of medium lubrication is better than that under dry friction condition.Under distilled water and sea water medium lubrication condition,a large amount of friction heat of the contact area of the friction pair can be taken away because of the circulation flow of the liquid,diminishing the effect of temperature on the friction surface.The medium lubrication is an ideal state of fluid lubrication.Under dry friction condition,the heat dissipation of friction contact area is slow,but because of the presence of solid lubricating film,the friction coefficient is small,the condition is boundary lubrication.The sulfurized layer surface is irregularity,and convex peak bears greater pressure.When the strength of the sulfide film is less than the friction load,the film will break.Therefore sulfide solid film is very suitable for precision wear environment.