A comparison of gaseous hydrogen embrittlement, slow-strain-rate hydrogen embrittlement, and stress-corrosion cracking InTi-8Ai-1Mo-1V

Abstract

Metallographic, fractographic, and acoustic-emission studies have been carried out on the near-α commercial alloy, heat treated to produce the Widmanstätten structure and in some cases aged to precipitate α₂. Both aged and unaged material underwent GHE in ∼ 10 kPa gaseous hydrogen, failure occurring along the α-β interface. Electron-diffraction studies established the presence of a layer of fee titanium hydride at the fracture surfaces, and acoustic-emission and fractographic observations indicated that propagation was discontinuous. The aged alloy underwent SSRHE in inert environments and SCC in 3 pct aqueous NaCl and, in contrast to GHE, failure occurred across the α-plates in both cases, producing indistinguishable cleavage-like fracture surfaces. Again, titanium hydride was detected at the fracture surfaces and, from acoustic-emission studies, crack propagation appeared to be discontinuous. Based on these observations, it is suggested that the three forms of failure occur by a common mechanism, namely by the repeated formation and rupture of the hydride phase.