Correlation between small punch and CVN impact tests for evaluation of cryogenic fracture characteristics of isothermally-aged nitrogen-containing austenitic stainless steels

The Charpy-V-notch impact test has been used routinely to evaluate the ductile-brittle behavior in steels. Likewise, the Small-Punch test has been applied to evaluate toughness properties in different materials. In this work, both tests were conducted at -196 °C on three types of austenitic stainless steels JN1, JJ1 and JK2, which were solution treated and then aged at temperatures between 700 and 900 °C for 10 and 1000 minutes. The solution treated steels exhibited a ductile fracture with high fracture energy, after testing with both tests. The brittle intergranular fracture was induced by the aging process of specimens and thus the fracture energy of tested specimens decreased dramatically. The highest and lowest decreases in energy with both tests occurred in the aged JN1 and JK2 steels, respectively. The Charpy-v-notch, CVN, test energy and small-punch, SP, test energy at -196 °C was found to follow a linear correlationship equation, CVN Test Energy = 89.7 SP Test Energy-63.0.