Creep Rupture Properties of Indigenously Developed 304HCu Austenitic Stainless Steel

The 304HCu austenitic stainless steel tubes are being produced for the first time indigenously in India. Creep tests have been carried out at 923 and 973 K on two heats with different solution annealing conditions. Stress levels ranged from 180 to 300 MPa at 923 K and 100 to 170 MPa at 973 K. The creep curves showed a small instantaneous strain followed by primary, secondary and tertiary creep stages. The rupture lives varied in the range of 50-8700 hours. Higher rupture life was observed in the heat with higher solutionising temperature. The variation of creep rupture life with applied stress at different temperatures is compared with internationally reported data and it is found that the indigenous 304HCu SS tube material has creep rupture strength comparable with internationally reported data. The variation of steady state creep rate with stress showed a power law relationship. Rupture ductility was generally found to decrease with increase in rupture life. SEM fractography revealed mixed mode failure with predominance of intergranular creep cavitation.