The influence of atomic order on H 2-induced environmental embrittlement of Ni 3Fe intermetallics

Abstract

The different sensitivity to H 2-induced environmental embrittlement for the ordered and disordered Ni 3Fe alloys has been investigated. The results show no environmental embrittlement in disordered Ni 3Fe in gaseous H 2 when tested at room temperature. However, the H 2-induced environmental embrittlement for the ordered Ni 3Fe becomes severer as the degree of order increases. The results of testing on simultaneous hydrogen charging show that disordered Ni 3Fe embritted as hydrogen atoms are forced into the material, implying that the embrittlement of ordered Ni 3Fe in gaseous H 2 is due to the acceleration of the kinetics of catalytic reaction to produce more atomic hydrogen. Further more, the hydrogen adsorption test of Ni 3Fe powder shows that the amount of chemically adsorbed hydrogen in the ordered state at room temperature is significantly larger than that adsorbed by the disordered materials, indicating that the more sensitive to H 2-induced embrittlement in the ordered Ni 3Fe is essentially due to accelerated catalytic reaction to produce more atomic hydrogen.