The permeability Φ of hydrogen with low partial pressure of O2 in Ni3Al, Ni3AI-4Cr, Ni3Al-8Cr intermetallics and in related disordered solid solutions Ni-4Cr, Ni-8Cr, Ni-7Al, Ni-7A1-8at%Cr was measured at 523 to 1223K (table 18) by using the gas permeation method. A maximum in Φ at about 623K, observed in Ni3Al, was attributed to a reported maximum in hydrogen solubility. It was observed that the addition of Cr to Ni3Al reduced Φ. Chromium exhibited the destabilizing effect that reduced the protective function of Al-based oxides. Aluminum, present in the alloys, was responsible for a surface protective layer that reduced the permeation flux of hydrogen.

Influence of Cr upon Hydrogen Permeation in Ni3Al at Low Partial Pressure of Oxygen. Čermák, J., Rothová, V.: Intermetallics, 2001, 9[3], 245-51

Figure 14

Hydrogen permeation flux in Ni3Al

Black circles, 270µm; white circles, 140µm;

black squares, 85µm; white squares, 190µm

Table 18

Arrhenius parameters for H permeation in Ni3Al alloys