Hydrogen embrittlement in a vacancy region of a Fe-Cr-Ni alloy: a computational study

C. LANZ; S. SIMONETTI

Waikoloa, Hawaii

Conferencia; The 8th Pacific Rim International Conference on Advanced Materials and Processing; 2013

The interaction of two-hydrogen atoms in a zone of gamma-Fe55Cr25Ni20 alloy having a vacancy (V) was studied by the atom superposition and electron delocalization molecular orbital (ASED-MO) method. The impurities are located aligned both along [1-10] direction and with the vacancy, in the (111) plane.  This behavior can be related with a lineal hydrogen-vacancy clusterization, as a precursor to crack initiation. The interactions mainly involve Fe 4px and Cr 4py atomic orbitals. An electron transfer to the H atoms from the Fe, Cr and Ni nearest neighbor atoms contributes to form the new H-metal bonds. The Cr atoms have an important role in the embrittlent process; the strengths of the Cr-Fe, Cr-Cr and Cr-Ni bonds are the most affected while the H-Cr interaction has the highest overlap population. Same H-H interaction is observed and could be associated with the precursor of hydrogen bubble.