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Microstructure And Friction Properties Of Sliver Coating On The Surface Of Bearing Steel By Electric Spark Deposition

Posted on:2015-02-14Degree:MasterType:Thesis
Country:ChinaCandidate:Y J ZhangFull Text:PDF
GTID:2181330422991233Subject:Materials science
Abstract/Summary:PDF Full Text Request
This paper prepares sliver coating on the surface of9Cr18steel and M50steel byelectro spark deposition, studies on the microstructures and properties of sliver coating,and investigates the effect of different parameters on the microstructures, cross-sectionalhardness and surface roughness. The optimum process parameters can be obtained byorthogonal experimental results. This paper also researches about the effect oftemperature, load and speed on the friction and wear properties of the silver coatingproduced on the surface of bearing steel by electro spark deposition with the optimalparameters, at the same time, reveals the mechanisms and laws of friction and wear.It has two ways to prepare sliver coatings on the surface of bearing steels byelectro spark deposition: one is deposited with rotating welding torch, the other isultrasonic welding torch. It investigates the effect of different parameters on theroughness and thickness of sliver coatings produced on the surface of bearing steels,with the analysis and testing methods of backscattered electron image, roughness testand so on. The optimum process parameters which can make the thickness of slivercoating reach the maximum can be obtained by orthogonal experimental results. Theoptimum parameters are got when voltage is100V, capacitor is120μF, the frequency is5files and the speed is medium.The results of XRD and EBSD show that the phases of the surface of bearing steelare mainly composed of silver and austenite. Researches of optical microscopy analysisshow that the microstructure of samples was divided into five levels from the surface tothe centre: silver, austenitic, quench-hardened case, tempering zone, matrix.Under dry sliding contact conditions, compared with the sample without electrospark deposition, the surface after electro spark deposition of M50steel have the lowerfriction coefficient, less than0.2. The results also show that the service life of slivercoating are longer than others when the friction condition is high loading, low speed orlow loading, high speed, which service life more than4800s. Under dry sliding contactconditions at low temperature, the friction coefficient of sliver coating of9Cr18steelrapidly decreased at first, dropped to0.1, then remain stable for a long time with a lowfriction coefficient. It means that the sliver coating on the surface of9Cr18steel canimprove friction and wear resistance at low temperature.
Keywords/Search Tags:solid lubrication, electro spark deposition, bearing steel, friction and wear
PDF Full Text Request
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