Microstructural Evolution in Nimonic 263 for High Temperature Power Plant

It is necessary to develop and implement new power plant due to both current energy and environmental demands. To enable these objectives to be met, the next generation of power plant, must be more.efficient. A common method of improving efficiency in plant is to increase the steam temperatures and pressures, which will necessitate the introduction of new materials. Nickel-based alloys lend themselves to high temperature and pressure applications due to their significant creep strength and the ability to operate at metal temperatures above 750 degrees C. Steam header and pipework systems carry steam from, the boilers to the turbines and are of particular interest in this research. Header and pipework systems experience high operating temperatures and pressures in the power plot, and it is therefore paramount that a suitable material is chosen and methodologies are put in place to predict their safe operating lifetimes Microstructural evolution in Nimonic 263, one candidate material for next generation plant, has been quantified using a variety of advanced analytical electron microscopy techniques, including field emission gun scanning electron microscopy (FEGSEM) and transmission electron microscopy (TEM). A focussed ion beam technique has also been used to produce site specific samples for examination in the TEM to assist in the identification of grain boundary precipitates. The changes occurring, in the microstructure as a result of time and temperature of exposure have been quantified and the precipitates fully identified. The results are also compared to predictions from thermodynamic equilibrium calculations. It is shown that variation in.exposure time and temperature can affect the microstructural development, and therefore the mechanical propertieS, of the Ninionic 263 alloy.