What causes hydride embrittlement? Atomic hydrogen atoms
diffuse into the metal and react with the metal atoms to
form a brittle metal hydride phase (MHx), which precipitates
in the metal where it affects the mechanical properties and
initiates cracking. The hydrogen may originate from welding
work without adequate protection with regard to the
environment, a heat treatment, corrosion processes or a
casting operation without a controlled atmosphere. Stresses
in the metal accelerate the formation of hydride.
Consequently, hydride formation will recur in the stress
field at the crack tip, and the crack will continue to
propagate until failure. The graph shows the temperature-pH
limits for some titanium alloys in NaCl brines.
