New method for long-term slow crack growth testing in hydrogen

Two self-loaded fracture toughness specimens, the environmental test ring (ETR) and the extended compact tension specimen (EXTCT), have been designed to efficiently measure the resistance of materials to slow crack growth in hydrogen environments. In tests lasting up to six months and at hydrogen pressures up to 52 MPa, crack initiation, crack arrest and growth rate data were reproduced for 4340 and Inconel 718 alloys. In addition, the crack growth resistance of high energy rate forged (HERF) 304L and 21-6-9 stainless steels was verified. The test program has shown the EXTCT to be the preferred specimen because it requires less demanding machining, inspection, and assembly procedures, and produces crack arrest information