Creep rupture of alloy 718 after thermal aging

Alloy 718 given the conventional 718/621°C age-hardening treatment was thermally aged at 593°C, 621°C, and 649°C for up to 50,000 h. These temperatures bracket the lowest of the duplex age-hardening temperatures. Subsequent creep-rupture tests conducted at the same temperature of thermal aging show no detrimental effects of 593°C aging after 50,000 h. Material aged for 50,000 h and tested at 621°C shows the rupture life to be approximately 60–65% of the unaged material, but at 649°C, the aged-material rupture life is on the order of 15% of the unaged material.