Notch sensitivity of Sanicro 25 in small punch creep test

Small punch creep tests of unnotched and notched 8 mm discs of new austenitic steel Sanicro 25 were performed at 700 °C. Side notches through the disc thickness proposed by Lacalle of different lengths ranging from 3.0 to 4.5 mm were applied for this study. It was found that the notch length influences the time to rupture and the minimum displacement rate, however no apparent signs of crack initiation were observed on the recorded time-displacement and time-displacement rate curves at 400 N force. The shortest time to rupture and fastest displacement rate were obtained for notch length of 3.5 mm, while the longest time to rupture and slowest displacement rate were obtained for notch length of 4.25 mm. The fracture of Sanicro 25 discs had signs of a “star” shape, with multiple cracks, which indicates lower ductility. A larger circular cap which is obvious for materials with high ductility was not present in all the small punch tests performed.