Surface Nanocrystallization of Nb-Ti Stabilized 439M Ferritic Stainless Steel

A new nanocrystallization process was designed, which included punching the surface coating to generate dislocation network or cells and recovery treatment to turn the dislocation cells into nano-sized grains. The effort was made to increase the service life of Nb-Ti stabilized 439M stainless steel surface with medium passive ability, particularly to enhance the outmost surface layer by nanocrystallization for improving resistances to corrosion. Electrochemical properties, electron work functions (EWFs), nano-mechanical properties of the nanocrystallized surfaces were investigated. It was demonstrated that the nanocrystallized 439M stainless steel surface exhibited improved resistance to corrosion in 0. 5 mol/L H2 SO4 solution. However, the nanocrystallized 439M stainless steel surface exhibited decreased resistance to corrosion in 3. 5% NaCl solution.