Materials for ultra efficient low emission power plant

Research project P 13802 Materials for ultra efficient low emission power plants H. CERJAK 11.10.1999 The intention of this proposal is to fullfill the applicants obligations to perform the tasks A5 and A6 as well as to co-operate in the common activities of. the European research programme COST 522. These tasks have been appreciated by the European community as well as by the Austrian ministry for science and traffic. Mainly for temperatures above 560C there is a great demand to replace the widely used austenitic tube materials through advanced ferritic-martensitic steels, in order to utilise their better thermal conductivity, lower thermal expansion coefficient, lower costs and better resistance against stress corrosion cracking in thermal power plants. Through the higher operating temperatures for steam power plants it will be possible to raise the service temperature and thus raise the efficiency and lower the emissions. In the last decades the ferritic-martensitic 9-12% chromium steels were further developed only by experimental methods which gave no insight and physically understanding of the important parameters which strongly affect the creep behaviour. The objective of this project is, as an essential part of the European research initiative COST 522, to get a reliable description of the high-temperature behaviour and stability for the modem 9-12%Cr steels. Nowadays the efforts are going in the direction towards heat resistant steels for USC-conditions(Ultra-Super-Critical, p>=300 bar and T>=600C). Due to the complex structure and behaviour of advanced ferritic heat resistant steels under service conditions, the trial and error method is not longer useful for the optimisation of these materials. The former applied method will be replaced by fundamental considerations with the aid of computational methods to consider the manifold influences on the creep behaviour named as: the stress response of the material controlled by the microstructure in form of the kinetics of precipitates and dislocations, influence of physical parameters like self-diffusion, evolution of damage. Based on the successfull research work done by our group in the framework of COST 501/1H the whole complex problem, the description of the creep behaviour for this materials has been subdivided in special tasks as: * Refined microstructural investigations to reveal an accurate description of the kinetic processes for the microstructure, * modelling of phases in equilibrium and the kinetics for the different phases based on thermodynamic models. This models or programs should be used too in a way to setup parameter concepts capable for fast optimisation of these materials, * modelling of the deformation behaviour basing on the changes and kinetics of the microstructure in a self- constituent physical way and * the modelling of the damage evolution, including refined models and microstructural considerations, to tackle the whole creep life. This four introduced fields are strongly interrelated concerning their influence on the creep behaviour of a complex steel. According to the above introduced division of the focused main problem, the present research proposal is splitted up in four tasks to get handable research topics. The final objective of this proposal is the description of the creep behaviour considering the most important kinetic processes on a physical base to be capable to perform calculations in a predictive and not descriptive way.