Effect of fabrication and test parameters on the fracture toughness of aged cast duplex stainless steels

Cast duplex stainless steels used in the primary circuit elbows of pressurized water reactors undergo thermal aging at their service temperature, around 300 deg C. This affects their toughness. In order to assess the residual toughness of elbows, two methods are applicable : an indirect one based on chemical composition and a direct one, newly developed, based on the testing of mini-CT specimens taken from elbows. The indirect method can be over conservative. The direct method has proved feasible provided several parameters are taken into account. It was shown that a correct assessment of toughness requires a large number of specimens, and a special care in the choice of sampling areas. (authors). 5 refs., 7 figs., 2 tabs., 1 appendix