Experimental Method for Creep Crack Growth Testing in Controlled Environments at High Temperatures

Investigating creep crack growth under extreme environmental conditions is a challenging yet essential undertaking for the assessment of structural lifetimes of critical components subjected to extreme working conditions for long periods of time. For example, there is currently a need to evaluate structural materials for Next Generation Nuclear Plants (NGNPs) which will operate very high temperature helium-cooled reactors (VHTRs) for generating electricity and use by-product process heat for applications such as hydrogen production and desalination. The primary helium coolant is expected to operate at temperatures at or above 750 degrees C. In order to evaluate candidate materials for the intermediate heat exchangers, such as Inconel 617 and Alloy 800H, we have developed a creep crack growth (CCG) test apparatus which was designed to test compact tension specimens at temperatures up to 850 degrees C in controlled environments, including impure helium environments, following ASTM standard E 1457-13. Details of the design of the CCG apparatus and representative results are presented.