LONG-TIME CREEP-RUPTURE PROPERTIES AND ELEVATED TEMPERATURE STABILITY OF D-979.

Long-time creep rupture tests were conducted on D-979 wrought bar in the fully heat treated condition. Forty smooth bar tests were run in the 1000 degree F to 1500 degree F temperature range for times ranging from 100 to 70,000 hours or more. A few notch rupture tests were also conducted in this temperature range for times up to 60,000 hours. Time to rupture and time to 1% total strain were tabulated and shown as log-log plots of stress versus time and as Larson-miller parametric curves. The long-time parametric data showed good correlation with extrapolated data based upon shorter time tests, indicating a moderate degree of stability over the temperature range studied. The alloy displayed very good stability up to 60,000 hours or more at 1000 degree F, 1100 degree F and 1200 degree F and resonably good stability at 1300 degree F or higher.