Study of Hydrogen Embrittlement Fatigue Properties Using Thermographic Techniques

Hydrogen is known to cause early failure of certain structural materials in a process known as hydrogen embrittlement (HE). Most hydrogen-containing vessels- pipes and valves- suffer from cyclic loading resulted from pressure changes thus raising long-term safety concerns. This work aims to explorer the potential use of a thermography-assisted fatigue testing technique and studies the fatigue properties of three materials. Both type 304 and 201LN stainless steels were found to be strengthened in hydrogen and their fatigue life was increased by a factor of 100. Type 201 nickel alloy on the other hand did not exhibit a significant change in fatigue life. Models are proposed to establish the correlation between thermal and fatigue behaviors in order to assess cumulative damage by analyzing the sample temperature profile during both short and long-term testing. The use of thermographic analysis of rotating beam samples as a fatigue test technique is proven to provide repeatable results independent of test cycle frequency while reducing test times by several orders of magnitude.