Effects of materials modification on the mechanical and corrosion properties of AISI 316 stainless steel

Material related failures such as fatigue, crack, wear and corrosion mostly occur on the surface and they damage the structure and affect the properties of the materials. Hence, enhancing the surface properties by various surface modification techniques is necessary to protect the material surface as well improve their microstructural and mechanical properties without altering their inherent properties. In the present study, the effect of surface mechanical attrition treatment (SMAT) on the mechanical and corrosion properties of 316 stainless steel (SS) was investigated in 0.6 M NaCl by electrochemical tests. Firstly, the material was subjected to SMAT and the effect of processing parameters on the material properties was determined. The results from the micro-hardness and surface roughness tests indicated a significant increment of strength, hardness and surface roughness in the layer surface with nanostructures after SMAT. The micro-hardness of the surface layer of the treated sample is higher than that of the untreated one by about 80–110 VHN at a depth of 200 µm. Compared with the untreated sample with an average roughness of 0.43 µm, the SMATed sample exhibited a higher average surface roughness of 0.69 µm. The nanocrystalline microstructure of the untreated and SMATed samples observed by an FEI Quanta 450 FEG Scanning Electron Microscope (SEM) revealed that SMAT resulted in the formation of a nanostructured surface layer on 316 SS without changing the chemical composition. However, lots of defects such as cracks were detected on the surface, which led to the deterioration in the corrosion resistance of 316SS after SMAT. The corrosion resistance of 316 SS deteriorated after SMAT. Compared to the as-received sample, the extent of corrosion attack is severe for treated sample. The electrochemical tests corroborate each other and confirm the effect of materials modification by SMAT on the mechanical and corrosion properties of 316SS.