Development of ferritic creep resistant steels containing 15% Chromium

Description

Development of 9Cr steels with improved creep strength resulted in an increase of the efficiency and a reduction of specific CO2 emissions in power plants. The martensitic 12Cr steels were suggested to improve corrosion resistance of martensitic steels under more severe steam conditions. However, all attempts for a development of 12% Cr steels were not successful due to the instability of the microstructure.
Ferritic steels, is a general name given to a group of steels containing 13-16% chromium. A combination of martensite and ferrite can be observed in the microstructure of ferritic steels. A higher amount of chromium content provides a higher corrosion resistance and enable ferritic steels to operate at relatively high temperatures. A reduction of martensite in general decreases the dislocation density and decreases the diffusion of alloying elements through dislocations and laths. Consequently, ferritic structure reduces the evolution rate of precipitates, especially at high temperature.
Both, microstructure and mechanical properties of ferritic steels strongly depend on the chemical composition and the performed heat treatment. In this study, first, the equilibrium phases of ferritic steels with different Nickel and Carbon content were simulated by MatCalc software in order to predict the phase fraction of the stable phases. Then, different heat treatments were performed on ferritic steels to optimise the phase fraction of martensite. Afterwards, the microstructure was investigated by means of SEM and XRD and mechanical properties such as tensile stress, toughness, and creep strength of three ferritic steels were examined in order to define the optimum variant.

Period	1 Jun 2021 → 5 Jun 2021
Event title	11th International Conference on Processing & Manufacturing of Advanced Material: THERMEC 2021
Event type	Conference
Location	Virtuell, AustriaShow on map
Degree of Recognition	International