Optimization of Sensitization and Intergranular Corrosion (IGC) Resistance of 304L Stainless Steel by Grain Boundary Engineering

Abstract

Sensitization behavior of thermo-mechanically processed stainless steel AISI 304L has been investigated. The thermo-mechanical processing was carried out at defor-mations 0-90%(reduction in thickness), annealed subse-quently at temperature ranging from 800-950oC for 15-60 minutes. Stainless steel was then sensitized at 675oC both for short (2 hours) and long and (53 hours) durations. The treated specimens were characterized for grain boundary character distribution, grain size and degree of sensiti-zation. The increase in annealing temperature and time during thermo-mechanical processing showed to increase grain size (upto 37 um) and the degree of sensitization. The ....(3-29) were also noticed to increase with the annealing temperature. The increasing fraction of coin-cident site lattice boundaries.... ...however did not decrease the degree of sensitization. The grain size through its effect on grain boundary surface area and effective grain boundary energy correlated well with the sensitization. Grain growth reduces the grain boundary surface area and the effective grain boundary energy as well which, in turn, enhanced the degree of sensitization. The degree of sensitization below a critical grain size(-<16 um) or beyond effective grain boundary energy (->0.05) is effective in minimizing the sensitization to the insignigicant level.