Creep-Resistant Steels

1. Creep-Resistant Steels

3. Z-phase, inaccurate data

6. Can only break even at absolute zero Thermodynamics Cannot win, can only break even Cannot reach absolute zero

7. Goal Increase as far as is possible, the maximum temperature in the cycle i.e. better materials & engineering

10. Taylor & Thornton, ALSTOM Power, Rugby

11. 0.5 µm

15. b a time = t+∆t time = t

17. 2.25Cr1Mo 600°C

19. Yamasaki & Bhadeshia, 2003

24. x

27. Coarsening diffusion r r 2 1 flux a q q concentration aq c r aq 1 c r 2 distance

28. -6 10 -7 10 -8 10 -9 10 2 3 4 5 6 7 8 9 10 10 10 10 10 10 10 10 10 10 4 2 0 2 3 4 5 6 7 8 9 10 10 10 10 10 10 10 10 10 10 1/3 Mean radius / m 1/2 Time / s -3 Number density 18 10 m Time / s Fujita & Bhadeshia, 2000

29. 1 10 0 10 -1 10 -2 10 1 2 3 4 10 10 10 10 Data from Abe, 1999 Fe-9Cr-W alloys 0W 1W 2W 4W M_23C_6 size / µm Time at 600 °C / h

30. 0.03 0.02 0.01 0.00 0 1 2 3 4 5 M_23 C_6 Mole fraction of phase Laves phase Tungsten / wt%

31. Multicomponent coarsening Venugopalan & Kirkaldy, 1978

32. 1.8e-19 1.7e-19 1.6e-19 1.5e-19 0 1 2 3 4 5 Coarsening accelerated by tungsten -1 chromium alone 2 Effective diffusivity / m s multicomponent Tungsten / wt%

33. Multiphase coarsening ? Laves concentration in ferrite q q distance

35. 650 oC Cole & Bhadeshia, 2002