Temperature Dependency of Hydrogen Embrittlement in Thermally H-precharged STS 304 Austenitic Stainless Steel

In the present study, the resistance to hydrogen embrittlement (HE) of STS 304 austenitic stainless steel was investigated at a wide range of temperature from 25 to - 253 degrees C. Tensile specimens were thermally precharged with H at 300 degrees C for 35 days under a H-2 gas pressure of 10 MPa. The resistance to HE was reduced with decreasing tensile temperature from 25 to - 50 degrees C, and then increased again with decreasing deformation temperature further. Finally, HE disappeared at temperatures below - 150 degrees C. This temperature dependency of HE in thermally H-precharged specimens was almost the same as that in the specimens deformed in a H-2 gaseous environment. The occurrence of HE at the temperature range of 25 to - 50 degrees C was attributed to both strain-induced martensitic transformation (SIMT) and H diffusion into stress-concentrated regions. The absence of HE at temperatures below - 150 degrees C was due to the sluggish H diffusion, despite of active SIMT.