Reassessment of the effects of laser surface melting on IGC of SUS 304

Abstract

Laser surface remelting (LSM) experiments were conducted on surface of 304 stainless steel using a 2 kW CW Nd: YAG laser and the effects of LSM on the intergranular corrosion (IGC) resistance of 304 stainless steel were reassessed from view point of grain boundary engineering (GBE). LSM could make the sensitized microstructures locally desensitize, and could improve the IGC resistance. The improved IGC resistance of the laser-surface-melted specimens could be attributed in part to Cr redistribution at the boundaries of the cells and grains and in part to existence of a large amount of low energy Σ(1 ≤ Σ ≤ 29) boundaries and the formation of 〈0 0 1〉(1 0 0) texture. However, the laser-surface-melted specimens became much more susceptible to IGC in the sensitization temperature region, and the corrosion rate of the resensitized specimen was even higher than that of the base materials under the same sensitization condition. A subsequent annealing treatment changed the grain boundary character distribution (GBCD) remarkably and the IGC resistance of the processed specimens was improved.