1 Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016
2 Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016
3 Shenyang Blower Works Group Co. Ltd., Shenyang 110869
4 Herbert Gleiter Institute of Nanoscience, Nanjing University of Science and Technology, Nanjing 210094
Cite this article:
Haiwei HUANG, Zhenbo WANG, Li LIU, Xingping YONG, Ke LU. FORMATION OF A GRADIENT NANOSTRUCTURED SURFACE LAYER ON A MARTENSITIC STAINLESS STEEL AND ITS EFFECTS ON THE ELECTRO- CHEMICAL CORROSION BEHAVIOR. Acta Metall Sin, 2015, 51(5): 513-518.
A gradient nanostructured (GNS) surface layer was fabricated on a Z5CND16-4 martensitic stainless steel by means of surface mechanical rolling treatment (SMRT). The microstructure in the GNS surface layer was characterized by using SEM and TEM. The results showed that the mean grain size increases with depth, from about 25 nm at the topmost surface layer to the initial value in the matrix. The total thickness of the grain-refined layer is about 150 mm. The electrochemical corrosion property of the SMRT sample was compared with that of the as-received sample in a 3.5%NaCl aqueous solution. It is shown that the pitting corrosion potential increases from about 0.179 V in the as-received sample to about 0.313 V in the SMRT sample, and the self-corrosion potential also increases evidently. The formation of nanostructures, the increased structural homogeneity, and the introduction of compressive residual stresses in the GNS surface layer, as well as the decreased surface roughness, were discussed to promote the pitting corrosion resistance of the SMRT sample.
Fig.1 SEM image of the as-received Z5CND16-4 stainless steel sample
Fig.2 Cross-sectional SEM image of the Z5CND16-4 stainless steel sample after surface mechanical rolling treatment (SMRT)
Fig.3 TEM images of the SMRT surface layer at different depths
Fig.4 Statistical distribution of grain size of the topmost surface layer
Fig.5 Distributions of residual stresses along depth in the SMRT surface layer
Fig.6 Potentiodynamic polarization curves of the SMRT and the as-received samples in 3.5%NaCl aqueous solution
Fig.7 SEM images of pits after corrosion on the as-received sample (a) and the SMRT sample (b) (d ferrite and martensite are pointed by A and B, respectively)
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