National Repository of Grey Literature 2 records found  Search took 0.01 seconds. 
Degradation of protective effect of surface layer on Ni3Al-Cr in hydrogen environment
Čermák, Jiří ; Rothová, Věra
Protective effect of surface layer on Cr-doped (4 and 8 at. % Cr) Ni3Al intermetallic was studied by high-temperature hydrogen permeation tests that were carried out at temperatures in the interval 775-1223 K. Hydrogen with about 1 vol. ppm O2 and 2 vol. ppm of H2O was used for the gas-permeation tests. It was observed that the addition of Cr degrades the - otherwise very good - high-temperature protective ability of oxide-containing surface layer of Ni3Al-Cr at strongly reducing hydrogen environment.
Modification of transmissivity of hydrogen through the surface of Ni3Al by alloying
Čermák, Jiří ; Rothová, Věra
Hydrogen invasion into Ni3Al-M was studied by gas-permeation method in temperature range 573 - 1 223 K. The dependence of hydrogen permeation flux J(d) through the membrane-like samples on the samples thickness d enabled us to assess the influence of the surface upon the rate of permeation. The surface transmissivity was introduced as a quantitative characteristic describing the rate of the process. Influence of three modifying elements M = Fe, Cr and Zr was studied. It was found that Zr supports and, on the contrary, Cr eliminates the inhibiting effect of the surface. The iron did not alter significantly the hydrogen transmissivity, and it causes enhanced grain boundary brittleness in hydrogen environment.

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