[ Hydrogen Embrittlement ]
[ Hydrogen Embrittlement ]
Figure 3. SSRT for DMV 316L and DMV 316LMoS
This slow deformation process allows the hydrogen to diffuse into the material and make the interactions with microstructural weak points, such as grain boundaries and dislocations, visible. The results of the SSRT test are then compared with a reference test in an inert gas such as nitrogen. A loss of ductility, reduced elongation at break or a brittle fracture are indicators of increased susceptibility to hydrogen embrittlement. The SSRT method
thus allows a precise assessment of hydrogen resistance. The effects of hydrogen embrittlement are quantified using formula( 3), the calculation of the relative reduction in area ratio( RAR), or formula( 4), the plastic elongation to failure ratio( EPR).
( 3) RA( in hydrogen gas) RAR
RA( in nitrogen gas)
= × 100 %; RA: Reduction in Area
( 4) EP( in hydrogen gas) EpR
EP( in nitrogen gas)
= × 100 %; EP: plastic elongation to failure
For SSRT tests according to NACE TM0198, the DMV 316L and DMV 316LMoS samples were manufactured from cold-finished tubes in our Costa Volpino facility. The individual samples were pre-loaded with hydrogen and tested at a pressure of 150 bar and room temperature in the
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