The nature of“white layer”found in 55SiMnMo steel subjected to friction test has been stu-died using TEM,SEM,X-ray diffraction and EPMA techniques.It is shown that the struc-ture of the“white laver”on the rubbing surface is duplex,consisting of a special martensiteand some austenite.This layer may be 25—50 μm thick.It is ultrafine,with grain diametricapproximately 30 nm.Its micro-hardness may be as high as Hm 1500 and is capable of cut-ting glass.It has superb corrosion resistance and resists tempering.Its mierostructure andhardness undergo changes only when the steel is tempered above 500℃.
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