Effect of Dissolved Hydrogen on the SCC Susceptibility of SUS316L Stainless Steel

摘要

The SSRT behavior in hydrogen dissolved hot water was investigated for cold worked SUS316L at a strain rate of 5 × 10~(-7)/sec. The cold work to 75% thickness reduction of the as-annealed steel resulted in the hardness increase from 150 HV to 420 HV. The tensile yield stress of the cold worked specimens (CW=75%) was about 1000 MPa and the total tensile elongation was significantly reduced from 0.8% of annealed specimen to 0.14% of the 75%CW specimen. The results of EPR tests on SUS316L steel indicated that the EPR-DOS increased with increasing sensitization period at 700°C and decreased with increasing degree of cold work or reduction in thickness. In the water with hydrogen dissolution of 0.4 ppm, many IGSCC type cracks were nucleated on the specimen side surfaces, while the fractured surface was almost TGSCC. No such a SCC as observed in hydrogen dissolved water was observed after the test in oxygen dissolved water. The susceptibility to SCC increased with increasing hydrogen content in hot water. Cold work caused the reduction of the number of surface cracks and disappearance of IGSCC.