Abstract: The research of two kinds of environmental hydrogen embrittlements in intermetallic at room temperature is summarized in this paper. Environmental embrittlement of intermetallic involves two main processes: generation of atomic hydrogen and diffusion of hydrogen in the alloy. The experimental results have verified that the ways of hydrogen atom generation are surface reaction of active elements with water vapor in air and catalysis reaction of molecular H₂ induced by transition metal atoms in gaseous hydrogen. The efficient method of suppressing environmental embrittlement of intermetallic is alloying. The moistureinduced environmental embrittlement can be suppressed completely by borondoping in Ni3Al alloy. The basic mechanism of the suppression effect of boron is related to severe reduction of hydrogen diffusivity along the grain boundaries. Effective suppression of the moistureinduced environmental embrittlement by Fedoping in Co₃Ti alloy is related to the reduction of the surface reaction kinetic of Co₃Ti alloy with water vapor. The H₂induced embrittlement can be suppressed completely by boron addition in the ordered Ni₃Fe alloy. The suppression mechanism is that boron atom segregates to the grain boundary, reducing the grain size and increasing the mechanical properties of the alloy. Boron in the ordered Ni₃Fe alloy clearly increases cohesion of grain boundary and decreases the diffusion coefficient of hydrogen along grain boundary.

Key words:  intermetallic, alloying, catalytic reaction, environmental hydrogen embrittlement, hydrogen diffusion, surface reaction