Effect of Misorientation on Intergranular Corrosion and Intergranular Stress Corrosion Cracking of Type 304 Steel with Coarse Columnar Crystals

Abstract

The effects of misorientation on intergranular corrosion in boiling H₂SO₄-CuSO₄ and boiling HNO₃ solutions and on intergranular stress corrosion cracking in FeCl₃ solution were investigated on type 304 steel with coarse columnar crystals. As the deviations of the growing direction around <100> orientation were within 10°, the grain boundaries were treated as simple tilt boundaries with <100> rotation axis.
The depth of interglranular corrosion, D_I, and the depth of intergranular stress corrosion cracking, D_C, of the specimen water-quenched, followed by sensitization at 923K for 7.2ks clearly decreased at coincidence boundaries (Σ13, Σ17, and Σ5) and the grain boundaries with rotation angle, ω, which were less than 10°and more than4 0°. D_I and D_C of the specimen water-quenched, followed by sensitization at 823K for 7.2ks after strained to 3.0% clearly decreased at coincidence boundaries and at the grain boundaries with ω which were more than 40°. However, D_I and D_C changed over a wide range at the grain boundaries with ω which were less than 10°. Schmid factor of component crystals was larger for deep D_I and D_C, and was smaller for shallow D_I and D_C. This suggests that D_I and D_C do not only depend on ω but also on the degree of plastic deformation near grain boundaries.
According to observation of carbide precipitation at grain boundaries, carbides were recognized at random boundaries, but not recognized at coincidence boundaries and the grain boundaries with ω which were about 45°.