Characterization of the Corrosion of Nanostructured 17-4 PH Stainless Steel by Surface Mechanical Attrition Treatment (SMAT)

Abstract

The corrosion properties of nanostructured 17-4PH stainless steel facilitated by a surface mechanical attrition treatment (SMAT) process were studied using electrochemical measurements in 0.6 M NaCl aqueous solution. The microstructure of the surface layer was characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results demonstrated the formation of a nanostructured surface layer on the surface of the material. By the combination of SMAT and low-temperature annealing processes, the potentiodynamic polarization measurements and X-ray photoelectron spectroscopy (XPS) spectra demonstrated an improvement in the corrosion resistance of 17-4PH stainless steel with a reduced corrosion current density of 0.241 mA/cm² and a higher chromium content. The improved corrosion resistance may be attributed to the formation of nucleation sites through which chromium may freely move from the matrix to the upper surface and thereby form a protective oxide layer on the surface of the material.

Keywords:

• 17-4PH stainless steel
• electrochemical impedance spectroscopy
• scanning electron microscopy
• surface mechanical attrition treatment
• X-ray diffraction
• X-ray photoelectron spectroscopy

Conflict of interest

No conflicts of interest are reported by the authors.

Additional information

Funding

Professor J. Lu acknowledges the support of the National Key R&D Program of China [Project No. 2017YFA0204403], the Major Program of National Natural Science Foundation of China: NSFC 51590892, the Ministry of Science and Technology of China [Project No. 2018YFE0190400], the Hong Kong Collaborative Research Fund (CRF) Scheme [Ref. C4026-17W], Theme-based Research Scheme [Ref. T13-402/17-N], and General Research Fund (GRF) Scheme [CityU 11247516]. This work was also supported by the Government of Hong Kong, Hong Kong SAR, China, Hong Kong [PF16-02783].