The mechanical behavior of the T91 martensitic steel has been studied in liquid lead-bismuth eutectic (LBE) and in inert atmosphere. Several conditions were considered to point out the most sensitive embrittling factor. The Small Punch Test technique has been employed by using smooth specimens.
T91 appeared in general as a ductile material, and became brittle in the considered conditions only at least, but not necessarily, if the test was performed in LBE.
It turns out that the loading rate appeared as a critical parameter for the occurrence of liquid metal embrittlement of T91 in LBE. For standard heat treatment condition, loading the T91 very slowly instead of rapidly in low oxygen LBE resulted in brittle fracture.