Effect of Ageing on Creep behaviour of IN 617 Nickel Base Super Alloy for Advanced USC Power Plant Applications

The goal of improving the efficiency of pulverized coal power plants has been pursued for decades. The need for greater efficiency and reduced environmental impact is pushing utilities to advanced ultra-supercritical conditions, i.e., steam condition up to 710/720 °C and 310 bar of pressure. The long-term creep strength with adequate thermal stability and environmental-resistance requirements imposed by these conditions are clearly beyond the capacity of the currently used ferritic steels and other related alloys. Nickel base alloys, such as IN617 super alloy is one of the preferred choices for steam turbine components used by fossil fuelled power generation plants. In this paper, effect of thermal ageing on creep behaviour of IN 617 nickel base super alloy were studied. Effect of thermal ageing on other mechanical properties such as tensile, yield and impact strength were also studied. Correlation between creep properties and microstructural changes, due to thermal ageing on IN 617 super alloy were also studied. Creep testing was carried out at different stress and temperatures for various thermal ageing conditions (800 and 850 °C) for different time durations and compared. The Alloy (IN 617) shows good thermal stability over long term aged condition with respect to creep strength. Less deterioration is observed in yield strength and tensile properties over long term ageing.