Showing papers by "Fujio Abe published in 2012"

Creep modeling and creep life estimation of Gr.91

Abstract: The creep behavior and deciding factors for creep life have been investigated for Gr91 in the temperature range between 450 and 725°C The longest time to rupture was 68755 h The creep life is inversely proportional to the minimum creep rate multiplied by the increase in creep rate by strain in the acceleration region for a wide range of test temperature and duration The minimum creep rate depends on both the time to minimum creep rate and the strain to minimum creep rate The strain to minimum creep rate decreases with decreasing stress, suggesting that the creep deformation in the transient region is significantly inhomogeneous at low stresses The creep life is correlated with the creep deformation parameters in the transient region so that we can predict the creep life from a short-term creep test for up to the end of transient region, corresponding to less than 30% of the creep life, without any stress extrapolation

Alloy Design of Creep- and Oxidation-Resistant 9%Cr Steel for High Efficiency USC Power Plant

Abstract: Ferritic heat resistant steels are strongly desired to expand their maximum use temperature up to 650°C for application to the next highest temperature components of highly efficient, low emission ultra-supercritical (USC) power plant with maximum steam temperature of 700 °C. This minimizes the requirement of expensive nickel base superalloys. Critical issues for the development of ferritic steels for 650 °C USC boilers are the improvement of oxidation resistance as well as long-term creep rupture strength, including welded joints. The optimized combination of boron addition and dispersion of nanometer-sized vanadium nitrides significantly improves long-term creep strength of 9% Cr steel and also exhibits no degradation in welded joints at 650 °C. The protective Cr2O3-rich scale forms on the surface of 9% Cr steel by pre-oxidation treatment in Ar gas, which significantly improves the oxidation resistance in steam at 650°C.