Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : November 02, 2019 - November 04, 2019
Hydrogen embrittlement susceptibility of stainless steels has been evaluated by Ni equivalent (Nieq), which is an index of FCC phase stability. Relative reduction of area of stainless steels increases with increasing Nieq up to 50 mass%. However, when Nieq exceeds about 50 mass%, the relative reduction of area decreases. There is a similar tendency for fatigue crack growth behavior. Namely, the hydrogen embrittlement susceptibility cannot be simply evaluated by FCC phase stability. To examine this subject, we investigated an effect of hydrogen on fatigue crack growth behavior in an equiatomic CrMnFeCoNi high-entropy alloy (HEA, Nieq = 52.8 mass%), as a stable FCC alloy. The ΔK increasing compact tension tests were performed at room temperature in air after hydrogen charging with 100 MPa-high pressure gas at 270°C for 237.5 h. The fatigue crack growth rate of the hydrogen charged HEA was 2.5–3.7 times higher than that of the uncharged HEA in the ΔK range of 16 MPa·m1/2–30 MPa·m1/2. The crack growth path in uncharged HEA was predominantly transgranular, whereas intergranular crack growth became significant in hydrogen charged HEA.
