Effect of Surface Nanocrystallization on Stress Corrosion Cracking of SS400 Steel

A nanostructured surface layer was synthesized on SS400 steel by means of high energy shot peening (HESP).The refined microstructure in the top surface layer was characterized by means of transmission electron microscopy (TEM),and the residual stress variation along the depth of the treated sample was examined.Experimental results showed that after the HESP treatment the microstructure of the surface layer could be refined down into the nanoscale.The compressive stress induced by HESP decreased along the cross-section down to zero at about 600 μm.A compressive stress nanostrutured layer was achieved in the top surface of SS400 steel.The results of slow strain rate tests of SS400 steel in Ca(NO3)2 57％＋NH4NO3 3％ solution at 98±3 ℃ indicated that the resistance of SS400 steel to SCC had been improved.