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Projects / Programmes source: ARIS

New generation of superior creep resistant steels with nano-particles modified microstructure

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Research activity

Code Science Field Subfield
2.04.02  Engineering sciences and technologies  Materials science and technology  Metallic materials 

Code Science Field
T150  Technological sciences  Material technology 

Code Science Field
2.05  Engineering and Technology  Materials engineering 
Keywords
high Cr steel, microstructure, nano-particles, creep, toughness, plasma
Evaluation (rules)
source: COBISS
Evaluation of bibliographic research performance indicators according to ARIS methodology
Citations Citations for bibliographic records in COBIB.SI that are linked to records in citation databases
source: WoS source: Scopus source: COBISS
Researchers (17)
no. Code Name and surname Research area Role Period No. of publications
1.  35645  PhD Jaka Burja  Materials science and technology  Researcher  2016 - 2019  321 
2.  22289  PhD Uroš Cvelbar  Electronic components and technologies  Researcher  2016 - 2019  730 
3.  37413  PhD Ana Debevec  Materials science and technology  Junior researcher  2016 - 2018  45 
4.  21559  PhD Darja Feizpour  Materials science and technology  Researcher  2016 - 2019  174 
5.  33330  PhD Gregor Filipič  Electronic components and technologies  Researcher  2016 - 2017  129 
6.  10842  PhD Matjaž Godec  Materials science and technology  Researcher  2017 - 2019  883 
7.  18475  PhD Aleksandra Kocijan  Materials science and technology  Researcher  2016 - 2019  255 
8.  28660  PhD Irena Paulin  Materials science and technology  Researcher  2016 - 2019  317 
9.  15269  PhD Bojan Podgornik  Materials science and technology  Head  2016 - 2019  1,130 
10.  26237  PhD Marko Sedlaček  Materials science and technology  Researcher  2016 - 2019  248 
11.  04101  PhD Božidar Šarler  Process engineering  Researcher  2016 - 2019  1,101 
12.  08001  PhD Franc Tehovnik  Materials science and technology  Researcher  2016 - 2019  324 
13.  05438  PhD Matjaž Torkar  Materials science and technology  Retired researcher  2016 - 2019  469 
14.  17622  Janez Trtnik    Technical associate  2016 - 2019  18 
15.  24284  PhD Franci Vode  Materials science and technology  Researcher  2016 - 2019  159 
16.  31618  PhD Rok Zaplotnik  Electronic components and technologies  Researcher  2016 - 2019  304 
17.  32177  PhD Borut Žužek  Materials science and technology  Researcher  2016 - 2019  414 
Organisations (2)
no. Code Research organisation City Registration number No. of publications
1.  0106  Jožef Stefan Institute  Ljubljana  5051606000  90,682 
2.  0206  Institute of Metals and Technology  Ljubljana  5051622000  5,977 
Abstract
Steam power plants on fossil fuels still produce approx. 40% of world electrical energy and the same trend is expected to remain also in the future. Majority of steam power plants operate at steam temperatures of up to 600°C and efficiency of about 40%. The efficiency is directly proportional to the temperature and pressure of the steam, with a minimal temperature increase meaning substantial energy savings and reduced CO2 discharge. Pressure and temperature of the steam are limited by the properties of materials used. For materials intended for components in steam power plants creep resistance, high-temperature oxidation resistance and crack propagation resistance are crucial. With the development of steels with increased chromium content already in 50's remarkable progress was made with steam power plants able to operate at temperatures up to 600°C. Requirements to increase the efficiency and temperature stability of the components coupled with extremely complex effect of the type, amount and combinations of different alloying elements on the microstructure of steel are constantly dictating the development of new creep resistant steels and modification and optimization of the existing ones. Creep is low speed process of permanent deformation, which is carried out by diffusion of vacancies and dislocations. Movement of vacancies and dislocations in the microstructure is mainly affected by grain and sub-grain boundaries, by dissolved atoms in solid solution and the presence of precipitates in the matrix. Mechanical properties and creep resistance of steel is greatly dependent on the size, distribution and volume fraction of thermodynamically stable precipitates. Important elements of the microstructure which increases the creep resistance of 9-12% Cr steel are fine M23C6 and MX precipitates and Laves phase. During the creep process Z-phase as well as the Laves phase starts to grow thus having negative impact on the creep resistance. The downside of 9-12 % Cr creep resistant steels is also in the reduction of fracture toughness, being related to the presence of M23C6 carbides. The most famous representative, which is still one of the most commonly used steels for steam power plants in Central Europe, is the X20CrMoV12-1 steel, with a high content of M23C6 carbides. In the middle of the 70's P91 steel with a reduced content of C and Cr and the addition of V and Nb was developed in USA. It has a better creep resistance, but due to the reduced content of Cr lower resistance to corrosion. Another possibility to increase creep resistance is in the strengthening of ferritic steels with nano-oxide particles, such as TiO2 and Y2O3. However, production of ODS steels requires expensive and complex processes of powder metallurgy, which is not suitable for mass production. Another option is direct addition of nano-particles in the melt. However, due to poor wettability, agglomeration of the particles and their solubility in the steel this method is still in the development stage and very limited. Solution to this problem should be seek in plasma technology. Advantage of plasma lies in the surface conditioning, thus allowing full wettability and increase of surface energy. The aim of the proposed research is to investigate the possibilities for direct alloying of steel with nano-particles as well as to develop a steel resistant to creep deformation at temperatures above 650 °C. The basic idea is to change the properties of steel with a modification of the microstructure on the nano-scale, which should be achieved by modifying and optimizing the type and content of alloying elements, through the improvement of thermo-mechanical processing and heat treatment, but especially by plasma surface modification of nano-particles and their successful addition into the melt. On the other hand, nano-modification of the microstructure must not deteriorate the mechanical and corrosion properties of the steel.
Significance for science
Content of the project fully coincides with national research priorities and objectives, as well as with the European guidelines in the program Horizon 2020. Subject of the project connects area of advanced materials and nanotechnology with technological development for a sustainable economy, with emphasis on the development of materials for extreme operating conditions and integration of nano-materials into existing production systems. The key question is how to achieve cost-effective development and incorporation of stable nano-particles in the steel microstructure and thus provide superior properties in a wide temperature range. Scientific contribution is planned in two areas. Namely in the multidisciplinary research approach to the effect of various parameters on the formation of finely dispersed phases and the associated high-temperature resistance. Furthermore, research will be focused on the opportunities and impact of direct alloying of the melt with nano-particles. Based on the results of the theoretical thermodynamic analysis, creep experiments and analysis of the corresponding microstructure new knowledge about development and elements of the microstructure and their effect on the hardening mechanisms and properties of steel will be obtained. In the area of composition ??modification the scientific contribution is seen in determining the influence and interaction of various alloying elements on the formation and stability of stable phase and carbides. Study on the effect of thermo-mechanical and heat treatment conditions will give answers on the possibility of introducing additional nucleation sites for precipitation and further stabilization of the microstructure. From the analysis of the microstructure evolution the ability of theoretical thermodynamic tools for identifying origin and evolution of microstructure will be determined. The aim is also to develop a semi-empirical dependence of the precipitates growth rate during creep as a function of composition, temperature, size, distance between precipitates and their volume fraction. Investigations on the possibility of introducing nano-particles directly in the melt open a tremendous opportunity for further improvement in steel properties. With the successful realization of direct addition of nano-particles in the melt nano-technologies could become an important part also in the traditional production processes. Based on the world-wide relevance and importance of the topic, we expect for the research results and findings to be patented and published in the top international scientific literature, both in the field of materials and nano-science. By working with experts from other institutions and industry, we will provide rapid transfer and implementation of research results in the practice.
Significance for the country
Thermal power plants on fossil fuels produce approx. 40% of world energy and due to the constant increase in electricity demand this trend will continue in the next 30 years. Currently they achieve up to 45% efficiency. In order to increase efficiency and reduce energy consumption, CO2 emission and impact on the environment it is necessary to increase the temperature and pressure of the steam entering the turbine. This dictates the use of new, more temperature-resistant materials. Despite the availability of materials with excellent high-temperature characteristics, their expensive and complex production limits their use. Thus, steel produced by traditional methods still remains the main material for the components in thermal power plants. Project is important for co-financier of the project, as well as for the entire Slovenian and global steel industry. The results will enable production of steel with nano-modified microstructure and consequently greatly improved creep resistance and extended operation limits. On the other hand, the concept of strengthening steel microstructure by direct incorporation of nano-particles can be transferred to other types of steels too, leading to improved properties. From the beginning of the nineties co-financier systematically invests in research and development of knowledge, which is reflected in increased quality of their tool steels and permanent presence in the global tool market. With the development of creep resistant steel with nano-modified microstructure new possibilities of entering on a very broad market of steel for energetics are opening for the co-financier. Development of a new temperature-resistant steel represents significant competitive advantage and better market position as compared to the competitors. Aim of the proposed project is a better understanding and insight into the microstructure development in the process of creep and study of the possibilities for direct addition of nano-particles in the melt. These investigations will contribute to improved product quality and increased opportunities for the development of new steels and thus entrance to new markets. Additionally, mastering the technology of direct alloying of nano-particles will directly indicate high-tech level of the company and research capabilities in Slovenia.
Most important scientific results Interim report, final report
Most important socioeconomically and culturally relevant results Interim report, final report
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