Design of a new generation of 12 % chromium steels

Start date 11/10/2010
End date The project is closed: 31/01/2016
​Steam power plants supply 70% of the world’s electricity and in order to minimize the CO2 emissions of fossil fired power plants, it is necessary to increase the steam inlet temperature as high as possible. This requires a material with sufficient creep, oxidation, corrosion and fatigue properties at high temperature of 650°C. 9-12% Cr steels have shown a good performance during last years up to 615°C. The main strengthening mechanism in these alloys is precipitation hardening obtained from fine MX particles in the steel. After long time exposure at high temperature these steels suffer from a phase transformation where coarse and brittle Z-phase grows at the expense of desired MX particles. To delay the occurrence of Z-phase, compromises in the alloy composition such as reduced Cr content and hence reduced corrosion resistance is necessary. Our new solution is to use Z-phase as a thermodynamically stable strengthening agent with a fine distribution in the steel. This leads to a new generation of 12% Cr steels potentially improving the thermal efficiency of power plants from today’s average of 38% to 50%. To do this, microstructure of different trial alloys containing Laves phase, M23C6, MX, and Z-phase are characterized using Scanning Electron Microscopy, Transmission Electron Microscopy​ and Atom Probe Tomography.​ ​​​​​
Publications
​Initial study on Z-phase strengthened 9-12% Cr steels by atom probe tomography
F Liu, H-O Andrén
In “Materials for Advanced Power Engineering 2010”, Eds. J Lecomte-Beckers, Q Contrepois, T Beck and B Kuhn, Schriften der Forschungszentrum Jülich GmbH (2010), Reihe Energitechnik, Part III pp 107-116

Microstructure of a Creep-Resistant 10 Pct Chromium Steel Containing 250 ppm Boron
A Golpayegani, F Liu, H Svensson, M Andersson, H-O Andrén

Metallurgical and Materials Transactions A, 42 (2011) 940-951
Effects of laser pulsing on analysis of steels by atom probe tomography
F Liu, H-O Andrén
Ultramicroscopy, 111 (2011) 633-641

Effect of Boron on Carbide Coarsening at 873 K (600°C) in 9 to 12 pct Chromium Steels
F Liu, D Fors, A Golpayegani, H-O Andrén, G Wahnström
​Metallurgical and Materials Transactions A, 43 (2012) 4053-4062
KME (Consortium for Materials technology for thermal energy processes), VGB (Research Foundation of the Association of Large Power Plant Operators, Germany), STEM (Swedish National Energy Agency), Z-ultra (FP7, EU)
​​​Siemens Industrial Turbomachinery, Finspång, Sweden; Fraunhofer Gesellschaft zur Förderung der angewandten Forschung, Freiburg, Germany; Saarschmiede GmbH Freiformschmiede, Völklingen, Germany; RWE Power AG, Essen, Germany; Technical University of Denmark, Kgs. Lyngby, Denmark; Institute of Physics of Materials, Brno, Czech Republic; E.O. Paton Electric Welding Institute, Kiev, Ukraine; Technical University of Georgia, Tbilisi, Georgia; Technical University of Graz, Graz, Austria; IPP-Centre Ltd, Kiev, Ukraine; Engineering Academy of Armenia, Yerevan, Armenia.

Published: Wed 19 Feb 2014.