Abstract：In order to study the effect of sample preparation method on the results of nanoindentation test of steel, single-phase, multiphase, low-carbon, medium-carbon and high-carbon steels were selected to explore the parameters of sample preparation of nanoindentation. The equipment of mechanical polishing and electropolishing were utilized for surface polishing, and the influence on surface condition between oxide mechanical polishing and electropolishing with different parameters was compared. The surface roughness of the sample was quantitatively determined by real color confocal scanning microscope. Subsequently, in order to verify the effect of sample preparation, a nanoindenter was employed to obtain nanohardness and elastic modulus of different microstructures by two polishing methods. The results show that oxide mechanical polishing is suitable for preparing the sample of single-phase and indentation depth more than 500nm. Electropolishing can effectively avoid the surface hardened layer. Under the appropriate parameters, it can not only meet the requirements of test standard but also distinguish different phases. However, inappropriate parameters can bring about the illusion of microstructures, seriously affecting the accuracy of the nanoindentation results. Meanwhile, the evaluation of the sample preparation should take into account the stability of the test curve rather than just the average surface roughness of the polished sample. Finally, the parameters of electropolishing for low-carbon steel W1300, medium-carbon steel SWRCH35K and high-carbon steel SWRH82B were given, which could provide reference and guidance for preparing the similar steel sample to perform nanoindentation test.
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