failure investigation of hydrogen blistering on low-strength carbon steel

the current study assesses the root causes of hydrogen blisters on low strength carbon steel equipment. for this purpose, some experiments including hardness test, non-destructive test (ndt), metallography, and fractograpghy are conducted. the microstructure of two blisters is assessed by means of optical microscopy and scanning electron microscopy (sem). the microstructural studies show that the steel plate has some inclusions and banded ferrite/pearlite structure. the energy dispersive x-ray spectroscopy (eds) results indicate that these inclusions mainly contain mn, s, al, ca, and si. the results show that the inclusions and planar imperfections found in the ndt have been the nucleation locations for blisters in the plate. remediation action plans are recommended to prevent further occurrence and growth of hydrogen blisters.