Isothermal, Thermo-Mechanical and Bithermal Fatigue Life of Ni Base Alloy HR6W for Piping in 700 °C USC Power Plants

Abstract Three types of high temperature fatigue tests are carried out for HR6W, which is one of the candidate materials for piping in an advanced ultra super critical (A-USC) power boiler operating over 700 °C steam condition. The first test is the isothermal fatigue test at 700 °C, the second one is the thermo-mechanical fatigue (TMF) test between 100 °Cand 700 °C under in-phase and out-of-phase conditions, the final one is the bithermal fatigue (BTF) test at 100 °C and 700 °C. The relations between the partitioned inelastic strain range determined by the strain range partitioning method and the life in those tests show good agreement, while the relations between the total strain range and the life show some differences.