| The failures of metal material (such as corrosion, wear and fracture) usually begin from their surface, which is very sensitive to the surface structure. A certain thickness of the nanocrystalline structure layer is prepared by surface nanocrystallization, its unique structure and excellent performance can significantly improve the global properties and environmental service behavior of materials, therefore the research is being paid great attention by considerable researchers. As a new concept in recent years, surface nanocrystallization becomes a convenient technology with high efficiency and low cost. Nanostructured layer is fabricated on the metal material surface as well as geometrical modality nanocrystallization was formed, this technology provides a practical way for nano-technology combined with conventional materials, and neatly solves the technical problem of the nano-bulk materials preparation, therefore the research of surface nanocrystallization technology has a great significance.With the low production cost, high strength, small thermal expansion coefficient, favorable thermal conductivity and good corrosion resistance,1Cr17steel is mainly used in chemical industrial equipment and oxidation-resistant parts. However, more defects appear in the1Crl7steel surface with the hot-rolling process, lower hardness and poor global performance limit41Cr17to use in engineering construction. But, we can prepare a nanostructure layer on the stainless steel surface by nanocrystallization processing to improve the1Cr17stainless comprehensive performance.In this paper,1Cr17stainless steel was treated by the fast multiple rotation rolling (FMRR) equipment. The microstructure of the processed sample was observed and analyzed by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM); micro-hardness tester was used to determine micro-hardness variation along the depth. This paper studied the corrosion resistance of1Cr17stainless steel after FMRR treatment; meanwhile wear morphologies were observed by scanning electron microscope (SEM) and the wear resistance of the sample before and after the FMRR processing was compared.(1) An approximately50μm thickness of the equiaxed nanocrystalline structure layer was prepared on the1Cr17stainless surface by the fast multiple rotation rolling treatment, which is a severe plastic deformation layer, the average grain size is about20nm in the top surface, grain orientation is random distribution, grain size increased gradient with the depth of the deformed layer; the deformed layer thickness of FMRR60min sample is more than FMRR30min sample, however there is little change in the degree of grain refinement.(2) Compared with the original sample (190HV), the1Cr17stainless steel surface micro-hardness increased significantly after FMRR treatment, for FMRR30min and60min sample, the micro-hardness increased to270HV and310HV respectively; the micro-hardness along the depth from the outermost layer is a gradient change, until the same as the matrix.(3) Compared with the original sample, corrosion resistance of the FMRR specimen is decreased, while the corrosion resistance of FMRR60min sample is better than FMRR30min sample.(4) Under the oil lubrication friction circumstance, compared with the original sample, the average friction coefficient of1Crl7stainless steel after FMRR treatment decreased22%,39%, meanwhile the wear rate decreased20%,27%; shallower and thinner wear trace and furrows appear in the morphology of the FMRR sample surface, therefore the wear resistance had been improved significantly. |
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