Fracture Toughness Behavior of an Austenitic and a Martensitic Steel Tested in Gaseous Hydrogen

Abstract Turbomachinery companies are pursuing solutions to achieve industry wide carbon reduction objectives. One possible solution is utilizing hydrogen and or hydrogen blends instead of full hydrocarbon gases. The introduction of hydrogen into turbomachinery products, like compressors, gas turbines and turboexpanders, poses materials challenges due to the potential embrittlement of equipment operating for long periods in hydrogen. A testing program was conducted on two materials commonly used – a martensitic (ASTM A522 Type 1) steel and an austenitic (A182 F316L) stainless steel. In this work a specific focus is dedicated to fracture toughness tests according to ASTM E1820 conducted in gaseous hydrogen. Mechanical testing, detailed fractographic and micrographic analyses of the materials, including optical microscopy, scanning electron microscopy (SEM) and electron back-scatter diffraction (EBSD) were conducted. The results of the test program and materials characterization are described, highlighting the significantly different behavior in hydrogen environment of these two alloys.