Hydrogen in hot-salt stress corrosion cracking of titanium-aluminum alloys

Experimental studies show that hydrogen produced during the corrosion of titanium alloys by halide salts and subsequently absorbed by the titanium is responsible for cracking of these alloys. Autoradiography and proportional β counting were used to detect the diffusion of hydrogen into the metal matrix. Similar failure modes were observed in fractographic examinations of surfaces produced by hot-salt cracking and surfaces of precracked specimens pulled to failure in high pressure hydrogen gas. Stressed titanium-aluminum alloys cracked under low-energy proton bombardment and show that failure can be caused by the effects of stress and hydrogen alone. Similarities to hot-salt cracks were noted, and the approximate concentrations required to initiate and propagate cracks were calculated.