Inconsistent evolvement of micro-structures and corrosion behaviors in cold/warm deformed austenitic stainless steel

Abstract

The effects of cold/warm deformation on the micro-structures and corrosion properties of type 304 stainless steel (SS) were studied by micro-structural analysis and electro-chemical tests. Strain-induced α ′ martensite was produced by cold deformation but not by warm deformation at 100 °C, and it significantly influenced the surface nanohardness of SS. The corrosion resistance of the cold deformed 304 SS continued to decrease as the deformation reduction increased, while the corrosion resistance of the warm deformed 304 SS first decreased and then increased. The increases in strain-induced α ′ martensite and dislocation tend to promote corrosion, but the increases in low-∑ coincidence site lattice boundaries, low angle grain boundaries and the severely disrupted random grain boundaries tend to resist corrosion. Warm deformation may provide a possibility of obtaining type 304 SS with high-strength and corrosion resistance, which is attributed to the coupling effect of dislocation and grain boundary.

Keywords

• stainless steel
• deformation
• micro-structure
• nanohardness
• corrosion property