NOTCHED FATIGUE OF AUSTENTIC ALLOYS IN GASEOUS HYDROGEN

Circumferentially notched specimens of several austenitic stainless steel alloys subjected to positive load ratio, load controlled fatigue have been cycled to failure in high pressure hydrogen gas. The number of cycles to failure for a given applied stress amplitude varies among the alloys tested indicating that control of fatigue life in hydrogen environments may be attained through informed alloy selection. The number of cycles to initiate a crack does not vary significantly among the alloys tested, however the total life to failure varied by over an order of magnitude. This difference in life is attributed to variations of the stress and strain fields ahead of the blunt notch. These fields are influenced by the strength and strain hardening characteristics of each alloy and they dictate the driving force for fatigue crack growth while the crack is small.