Design of a new generation of 12 % chromium steels

​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.​ ​​​​​

• Hans-Olof Andrén

  Senior Professor, Microstructure Physics, Department of Physics

  My research deals with the microstructure of primarily metallic materials, which I study with high-resolution microscopy and microanalysis. Main methods are electron microscopy and atom probe...
• Fang Liu

  Docent at the division of Materials and Manufacture, Department of Industrial and Materials Science

  Fang Liu's research interest is to reveal the physical and chemical mechanisms underlying materials related phenomena, for instance creep and high temperature corrosion, and to establish the...
• Masoud Rashidi

  Post-doc at the division of Materials and Manufacture, Department of Industrial and Materials Science

  Laser sintering (LS) is the dominant powder-based method for additive manufacturing (AM) of metallic components that is already found in industrial application for high performance components. Masoud...