Hydrogen-assisted cracking of T-250 maraging steel

Hydrogen-assisted cracking (HAC) of T-250 maraging steel has been studied. The results showed that HAC could occur in air when the relative humidity (RH) was ≥30%. The arrested threshold stress intensity factor, KIH (MPa m1/2), decreases linearly with increasing the logarithm of hydrogen concentration entered into the samples during putting in humid air or charging in the solution, C (ppm), i.e. KIH = 49.5–26.1 ln C. The threshold stress intensity factor for the crack initiating from notch tip in humid air with RH = 82%, KIH(ρ), increases with increasing the square root of notch radius ρ, as ρ > ρ0 = 0.08 mm, i.e. K IH ( ρ > 0.08  mm ) = − 32.7 + 244.9 ρ , however, when ρ ≤ ρ0, KIH(ρ ≤ 0.08 mm) = KIH = 37.5 MPa m1/2.