Cracks was found in type 347 stainless steel internal attachment welds of a reactor for a high temperature, and high
pressure hydrogen service. One of the possible causes of cracking is low cycle fatigue cracking induced by repetition of
thermal stress to embrittled weld metal. Type 347 weld metal loses its ductility by presence of sigma phase and
hydrogen.

Keywords: desulfurization, hydrogen embrittlement, hydrocracking, martensitic, weldment