Thermomechanically induced precipitation of intermetallic phases in heat resisting ferritic steels

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The objective is to develop new ferritic steels together with its manufacturing process, which shows high resistance to creep, thermomechanical fatigue and oxidation. Therefore the influence of a thermomechanical treatment on precipitation of Laves phase will be investigated in steel grades with chromium contents between 15 and 20 wt.-%. One challenge is to control the chemistry and morphology of the Laves phase as well as the precipitation of carbonitrides and avoid at the same time the formation of sigma-phase. For this purpose a computer-aided optimization of the alloy will be performed, which intends to get a high volume fraction of the Laves phase. Thermodynamic modelling helps to increase the tungsten content in solid solution and reduces the amount of carbonitrides. The developed alloys will be manufactured in an laboratory scale and analyzed in further steps. The thermomechanical processing of this steel will be derived from thermodynamic modelling and its validation with experimental results. One major issue is the investigation of the temperature-sensitive mechanical properties which will be compared with the state of the art. A further important aspect is the quantitative description of the relationship between thermomechanical treatment and precipitation of the Laves phase. Thus the influence of the thermomechanical treatment on the microstructure and mechanical properties will be analyzed. In the focus is also the effect of precipitation kinetics and morphology of the precipitated particles. This project will establish a fundamental understanding of the correlation between alloying elements, microstructure, deformation structure, precipitations and mechanical properties of a new ferritic alloy concept.