Z phase strengthened steels for ultra-supercritical power plants

© Fraunhofer IWM

Z-Ultra is a medium-scale European Consortium which has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration under grant agreement no 309916.

The Z-Ultra project is running from 02/01/2013 - 07/31/2016.

The aim is to develop a heat resistant steel which allows increasing the thermal efficiency of fossil power plants to over 50%, which is 30% higher than the present standard in most existing power plants. The CO2 emissions are reduced accordingly.

The consortium combines the expertise of a steelmaker, a utility company, an engineering consultant company from Ukraine and eight research organizations and universities from EU and Eastern Partnership countries.

© Fraunhofer IWM

The idea is to exploit the Z phase as a thermodynamically stable strengthening agent in martensitic creep resistant steels.

Previously the Z phase has been considered as detrimental, since the coarse Z-phase particles that develop during long time service in high-chromium steels hardly contribute to the strength while growing at the expense of the fine, strengthening nitride particles.

However, high chromium contents around 12% are needed, since the current 9% chromium steels do not provide sufficient oxidation resistance at 650°C. Hence the challenge is to control the precipitation of the Z phase in 12% Cr steels such that fine Z particles are formed, which are stable for long times.

An important aspect is that the beneficial microstructure should be established also by the post-weld heat treatment.

The Z-Ultra project is funded by FP7 under NMP.2012.2.2-3 - Advanced materials for high-temperature power generation call with Grant agreement no: 309916.

 

 

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