Fatigue crack growth of additively and conventionally manufactured Hastelloy X in pressurized hydrogen gas

Artikel i vetenskaplig tidskrift, 2026

This study examines the fatigue crack growth behavior of Hastelloy X, a common gas turbine burner alloy, in both wrought and powder bed fusion-laser beam (PBF-LB) conditions. Room temperature fatigue crack growth tests were performed in 4.6 MPa hydrogen gas, with emphasis on crack propagation in the Paris regime. Compact tension specimens were tested either with or without hydrogen pre-charging, performed at 343 ◦C in 34.5 MPa hydrogen gas for 35 days. When tested at room temperature in gaseous hydrogen, the wrought alloy exhibited an approximately three-fold higher crack growth rate. The PBF-LB material showed accelerated crack growth in hydrogen at stress intensity factor ranges below ΔK = 30 MPa√m , whereas at higher ΔK values, the crack growth rates in hydrogen converged with those measured in air. Interestingly, the fatigue crack growth rates in hydrogen were similar irrespective of hydrogen pre-charging despite the six-to seven-fold increase in bulk hydrogen content after pre-charging. Although the acceleration of fatigue crack growth in hydrogen was modest compared with that typically reported for high-strength steels, fractography revealed clear evidence of hydrogen- assisted damage in the wrought material, including textured cleavage facets. No comparable features were observed in the PBF-LB material. However, a larger number of secondary cracks were observed in regions corresponding to ΔK < 30 MPa√m. Overall, the results suggest that hydrogen embrittlement was more prominent in the wrought Hastelloy X than in the PBF-LB Hastelloy X under the investigated conditions.