Research Of Friction And Wear Properties Of Self-lubricating Coating Which Prepared By Edm With Graphite And Cemented Carbide Alternately Deposited On Substrate Surface

The self-lubricating coating with graphite and cemented carbide alternately deposited on the surface of 45 steel by ESD-03 B electric spark surfacing repair machine,to improve the surface lubricity and wear resistance of mechanical parts.It's can improve the wear resistance and lubrication on the coating at the same time.The surface and cross-section morphology of self-lubricating coating were analyzed by SEM.The stress and temperature generated in the friction process were simulated by using Workbench.The friction and wear properties and wear mechanism of the self-lubricating coating were analyzed by using HSR-2M reciprocating friction and wear testing machine.The self-lubricating coating with graphite and cemented carbide alternately deposited on the surface of 45 steel by EDM.The coating structure was designed according to the requirements,and the coating states under different preparation processes were investigated.The optimal preparation parameters were determined as follows: rotating electrode 140 r / min,frequency 60 Hz,capacitance 60?F,deposition time determined by area ratio of graphite 0.18 and cemented carbide 0.2.Through the analysis of the surface and cross-section morphology of the coating,it is found that the coating surface is relatively uniform and dense.From the cross-section morphology,it can be seen that a transition layer will be formed between the coating and the substrate,which proves that a good metallurgical bonding is formed between the coating and the substrate.The friction of self-lubricating coating was simulated by workbench,and the distribution of stress,strain and temperature in the friction process was studied.The simulation results show that the stress and temperature at the contact interface of different coatings are different.Whether it is ball plane friction or pin plane friction,the maximum strain and stress occur on different coating region,and the temperature of the contact surface will gradually increase with the friction.In this thesis,the friction and wear properties of self-lubricating coatings were systematically studied.And the effects of load and friction frequency on the friction and wear properties of coatings under ball(GCr15)-plane and pin(YG8)-plane friction conditions were discussed.The results show that the friction coefficient of the coating is inversely proportional to the load and friction frequency,but the amount of wear is increasing.After the analysis of wear morphology,it is found that a layer of lubricating film was formed on the surface of graphite coating,which was covered on the surface of cemented carbide coating to improve the lubrication and wear resistance.When the coating is in the state of ball-plane friction,the friction coefficient reaches the minimum at the friction frequency of 500t/min and the load of 10 N,the minimum value is 0.247,and the maximum wear amount is 0.6mg.When the coating is in the state of pin-plane friction,the friction coefficient reaches the minimum at the friction frequency of500t/min and the load of 30 N,the minimum value is 0.136,and the maximum wear amount is 0.6mg.Through comparison,it is found that the friction coefficient of the coating after pin plane friction is the smallest,and the fluctuation is relatively stable,the wear surface is relatively flat,and the wear amount is relatively low.The wear mechanism of the self-lubricating coating was studied.It was found that the graphite coating played a lubrication role,while the carbide coating played a supporting role on the entire surface of the coating.The self-lubricating coating had the effect of reducing friction and anti-wear in the friction process.