CreepResistant Steels Zphase inaccurate data Thermodynamics Cannot win

Creep-Resistant Steels

Z-phase, inaccurate data

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

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

Taylor & Thornton, ALSTOM Power, Rugby

0. 5 µm

b a time = t+∆t

2. 25 Cr 1 Mo 600°C

Yamasaki & Bhadeshia, 2003

x

Coarsening diffusion flux r concentration 1 q r 2 a aq cr 1 q aq cr 2 distance

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

10 1 Data from Abe, 1999 M_23 C_6 size / µm 0 W 1 W 2 W 4 W 10 0 10 -1 10 -2 10 Fe-9 Cr-W alloys 1 10 2 10 3 Time at 600 °C / h 10 4

Mole fraction of phase 0. 03 M_23 C_6 0. 02 0. 01 0. 00 Laves phase 0 1 2 3 Tungsten / wt% 4 5

Multicomponent coarsening Venugopalan & Kirkaldy, 1978

Effective diffusivity / m s 2 -1 Coarsening accelerated by tungsten 1. 8 e-19 chromium alone 1. 7 e-19 1. 6 e-19 multicomponent 1. 5 e-19 0 1 2 3 4 Tungsten / wt% 5

concentration in ferrite Multiphase coarsening ? Laves q q distance

650 o. C Cole & Bhadeshia, 2002