Study On Friction And Wear Properties Of Marine Diesel Engine Cylinder Liner Under Simulated Low Sulfur Conditions

Since the implementation of the sulfur restriction order,low sulfur fuel oil has been widely used in ships.However,many researches and practices show that the cylinder liner of marine engine will be affected by high temperature,high pressure,combustion products,cylinder oil content and other factors under the condition of low sulfur fuel,which will produce various forms of wear.Therefore,the article first clarifies the working environment and state of the marine main engine cylinder liner,and then explores the friction and wear behavior of the cylinder liner under low sulfur conditions and proposes effective suppression methods.The main research contents of the thesis include:In this thesis,the composition and physical and chemical properties of cylinder used oil are analyzed firstly,and the working environment of cylinder lubrication under low sulfur conditions is discussed.The experimental results show that compared to the unused FEOCY 54 cylinder oil,the appearance of the cylinder used oil is black and opaque,the PH value of the oil aqueous solution is 8.5,and there is no aqueous acid or alkali,resulting in a significant increase in kinematic viscosity.Used oil is doped with metal abrasive particles,diesel fuel and its catalytic particles,corrosion products,fuel combustion waste,as well as oxygen-containing acids,colloidal substances,paint film asphaltenes and other substances formed by high-temperature oxidation and pyrolysis.Taking base oil,cylinder used oil and simulated medium as lubricating mediums,static immersion test and high temperature tribology test at 200℃were carried out to study the friction and wear behavior and mechanism of marine main engine cylinder liner under low sulfur conditions.Through immersion experiments,it can be seen that the cast iron sample has the largest weight loss and the most obvious surface corrosion in cylinder used oil.Pitting pits increased with time,followed by the degree of corrosion in the simulated lubricating medium,and there is no significant corrosion phenomenon in the base oil.The tribological test results show that the friction coefficient in the cylinder used oil and the simulated medium first increases and then decreases,and the wear marks and wear volume are larger than those of base oil.The cylinder liner samples are mainly abrasive wear in cylinder used oil and simulated medium,accompanied by a small amount of corrosion wear and adhesive wear,and iron oxides such as Fe_xO_y,FeSO₄ and FeS are generated;in the base oil,there are abrasive wear and weak adhesive wear.Surface modified potassium borate lubricant additives was prepared by plasma assisted ball milling for 10 hours and explored the inhibitory mechanism of potassium borate lubricating additive on wear and corrosion of cylinder liner materials under low sulfur conditions.The results show that under the mechanical action of ball milling and the effect of plasma pulse,the modifier and potassium borate powder are melted in micro regions and rapidly refined.The average primary particle size of potassium borate powder is between 100 and 300 nm,and the surface of the powder is chemically modified by organic groups.The friction surface with 0.8 wt%potassium borate powder simulated medium compound oil is flat and smooth,with significantly reduced corrosion traces,pitting pits,and wear marks.At the same time,the content of K and B on the wear surface increased significantly,while the content of Fe,S,and O decreased.Under the action of friction and heat of friction,friction chemical reaction films such as B₂O₃,Fe₂B,Fe₂O₃,and Fe₃O₄ are formed on the worn surface,which indicates that the potassium borate powder adsorbed and deposited on the worn surface can not only fill and repair the wear marks,but also neutralize acidic media and prevent acidic substances from directly contacting the cylinder liner,thereby achieving the effects of friction reduction,anti-wear,and corrosion inhibition.