Cause Analysis on Significant Decrease of Impact Toughness of Nitronic 50 Stainless Steel at Cryogenic Temperature

Regarding to the obvious low impact absorption energy of Nitronic 50 austenitic stainless steel used in the movement mechanism of cryogenic wind tunnel at cryogenic temperature during reinspection, a series of testing methods were adopted on the specimens of raw material and reference sample, such as chemical composition analysis, metallographic analysis, scanning electron microscope and energy spectrum analysis, and so on. The results show that numerous short rod-like AlN brittle inclusions existing in this batch of Nitronic 50 stainless steel were the main reason for the significant decrease of the impact toughness at cryogenic temperature. The coarse grain and the mischcrystal in the material also reduced the impact toughness.