Effects of high-temperature hydrogen exposure on room temperature tensile properties and fatigue crack growth behaviour of TiAl base alloy

Abstract

Tensile, notched tensile, and fatigue crack growth tests of hydrogen-exposed (in 0.1 MPa 99.9995% H 2 at 800 °C for 6 and 24 h) TiAl base alloy were carried out in ambient air. The results are compared with those of the material before exposure. By the H 2 exposure, the tensile ductility and tensile strength were reduced significantly, and greater reduction in the strength of the notched specimen was observed. The H 2-exposed specimen fractured in the elastic deformation range, while the non-exposed specimen deformed plastically before fracture. A small compact tension specimen (CT) was used to correlate the fatigue crack growth rate d a/d N and stress intensity factor range Δ K. In the near-threshold region of the fatigue crack growth diagram, the H 2-exposure had no effect on d a/d N. With increasing Δ K, d a/d N of the H 2-exposed material increased to about ten times higher than before exposure. The acceleration is due to the hydrogen embrittlement (reduction in ductility).