The influence of atomic order on H2-induced environmental embrittlement of Ni3Fe intermetallics

The different sensitivity to H2-induced environmental embrittlement for the ordered and disordered Ni3Fe alloys has been investigated. The results show no environmental embrittlement in disordered Ni3Fe in gaseous H2 when tested at room temperature. However, the H2-induced environmental embrittlement for the ordered Ni3Fe becomes severer as the degree of order increases. The results of testing on simultaneous hydrogen charging show that disordered Ni3Fe embritted as hydrogen atoms are forced into the material, implying that the embrittlement of ordered Ni3Fe in gaseous H2 is due to the acceleration of the kinetics of catalytic reaction to produce more atomic hydrogen. Further more, the hydrogen adsorption test of Ni3Fe 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 H2-induced embrittlement in the ordered Ni3Fe is essentially due to accelerated catalytic reaction to produce more atomic hydrogen.