The Content Of Carbon, Chromium Bearing Stainless Steels And Contact Fatigue Performance

Recent years,bearing is commonly used in wide range of applications PC and aerospace applications,etc.Excellent corrosion resistance,fine working accuracy and lower noise, long contact fatigue life is in need,so that at present lots of research is made to replace the 9Cr18 alloy,which woks now,as the result of that 9Cr18 alloy contains some coarse eutectic carbides in uneven distribution,leading to the poor performance.An attempt has clearly been made to collect every possible piece of information home and abroad,which might be useful,and then 4 alloys in different carbon and chrome content are developed.Then the work as following was done.At firstly,The temperature experiment of the 4 stainless bearing steel was carried for studying the effect to hardness and making the reasonable heattreatment.Latter,the microstructure and carbides was analyzed by microscope,Scanning Electron Microscope(SEM)and Transmission Electron Microscope (TEM).Finally,the research of the roll contact fatigue life experiment was to analyzed for rule of different carbon and chrome content,and the mechanism was gained by observing the sample in SEM after the roll contact fatigue life experiment.The result shows:(1)The quenching temperature from 1050℃to 1100℃is enough to have the 4 stainless steel to meet the requirement for use,and all the hardness are over 58HRC,after temperature experiments.More,the hardness of the alloy,which C 0.6%,Cr 14%reach highest.(2)After 1050℃quenching temperature was treated,cryptocrystalline martensite,the retained carbides,and the retained austenite are observed in these bearing steel's microstructure.In additional,the substructure of cryptocrystalline martensite is the lath and twin martensite by TEM.(4)The number of carbides rises with the carbon and chrome content increasing,after the quenching treatment.Carbide precipitation is tiny(below 1μm in size),distributed uniformly,as the carbon content is below 0.78%and the chrome content is below 14.82%. Carbide precipitation grows between 6 and 12μm,and become lager.Under the same heat treatment,carbides are all the M₂₃C₆ by the SEM and TEM.(4)The result of the roll contact fatigue life experiment shows that No1,2,3,4 alloy rating life L₁₀is 0.90×10⁷,1.70×10⁷,1.09×10⁷å'Œ0.36×10⁷.Compared with No4 alloy,their life is 2.50 times,4.72 times and 3.03 times.Moreover,the No2 alloy performs best for the leaves of L₁₀and L₅₀,which is 4.72 times and 2.71 times as the No4 alloy.(5)The mechanism of the surface and sub-surface flaw are found by researching contact fatigue.In addition,the shape and distribution of the carbides is proved to contribute to poor fatigue life.This is different from the other contact fatigue research,which focuses on sulfides,oxides,etc.