Coated Superalloys for Power Installations
Characterization and Testing of Coated Nickel- and Iron-Based Superalloys for Application in High-Temperature Power Installations
Tech Area / Field
- MAT-ALL/High Performance Metals and Alloys/Materials
8 Project completed
Senior Project Manager
Latynin K V
National Nuclear Center of the Republic of Kazakstan / Institute of Nuclear Physics, Kazakstan, Almaty
- Argonne National Laboratory (ANL) / West / Nuclear Technology Division, USA, ID, Idaho Falls\nUniversity of Wisconsin-Madison / College of Engineering, USA, WI, Madison\nLublin University of Technology, Poland, Lublin\nKorea Atomic Energy Research Institute, Korea, Yusung Taejon\nPacific Northwest National Laboratory, USA, WA, Richland
Several years ago leading countries joined their efforts to elaborate a concept for designing nuclear reactors of new, fourth, generation. Objective of this initiative (the Generation IV Nuclear System Roadmap) is to achieve crucial progress in development of nuclear energy installments and materials used for their construction.
At present, the majority of experts have identified work of the reactors at more high temperatures as an important step to increase economical fascination and assure further development of nuclear power production. Transition to higher operating temperatures will require both full-scale investigations at currently available materials used in nuclear industry at such extreme temperatures and development of new construction materials.
Currently the most important task of material investigations for the generation IV nuclear reactors are development of concepts and scientific insight of the behavior of construction alloys surrounded by supercritical water, led or led-bismuth, liquid salts; chemical compatibility of materials with heat carrier; corrosion of alloys and compatibility of fuel with fuel assembly casing .
Investigators in the field of high-temperature material science for space applications and fusion technology face similar problems. For example, dopants (such as wolfram, molybdenum, tantalum) in nickel superalloys (turbine blades in space and aircraft technology) increase durability and endurance of alloys. Yet, chromium, introduced to increase thermal stability to oxidation, decreases them. Therefore, to optimize properties of such alloy, one should create a region with increased concentration of chromium on the surface and decrease its content in the bulk.
An effective way to solve this problem is to use multilayer protective coatings of different function. Coatings of technological materials may assure reactor safety in transition (exceeding in operation temperature regime) and accident conditions. The requirement in this case is their physics-and-chemical compatibility with basic technological material at specified operating temperatures .
The Project objective is to obtain, characterize and test superalloys on the basis of nickel and iron with multilayer coatings of various functions for their application in high-temperature energy installments.
Characterization and tests of coated samples will be performed at high temperatures (Т 0.5Тmelting) in vacuum and in oxygen and acid environments. Coating thickness will vary from units to hundreds of micrometers. Main methods for coating preparation will be ion-plasma (+ ion mixing) and plasma-detonation deposition. Experimental researches will be performed using x-ray phase analysis, x-ray fluorescent analysis, optical metallography, transmission electron microscopy, scanning electron microscopy, Rutherford back scattering, nuclear reactions, PIXE, secondary ion mass-spectrometry, gas thermal desorption.
The following tasks will be performed within the Project:
1. Preparation of sample targets for coating;
2. production by the method of ion-plasma depositing of thin two-component coatings of given composition using two plasmotrons; production of multicomponent coatings by the methods of ion-plasma deposition of thin one-component coatings of given thickness with following their ion mixing; experimental control of composition and structure in produced coatings;
3. production of massive coatings by the method of plasma-detonation depositing based on powders of high-temperature (high-nickel) alloys; experimental control of composition and structure in produced coatings;
4. experimental and theoretical investigations of diffusion and phase transformation processes in thermally annealed coated materials for creation of thermally stable depth distribution of the formed phases;
5. corrosion stability tests of samples with physically-and-chemically compatible coatings in presence of oxygen and acidic media in a given temperature range; experimental investigations of aggressive media influence on microstructure (crack formation) and chemical composition of the samples;
6. mechanical tests of oxidized and non-oxidized samples (yield stress, tensile strength, relative expansion, microhardness, wear resistance); microstructure investigation of cracking under load; development of theoretical models and numerical simulations at atomic level of crack nucleation and proliferation processes in materials under stress;
7. investigation of influence of irradiation with light charged particles on coated sample’s microstructure (progress of gas swelling, surface blistering) and related degradation of mechanical properties; development of theoretical models and algorithms, numerical calculations of gas swelling and blistering in lamellar systems.
Upon completion of the Project it is expected to achieve the following main results:
· There will be developed the technologies for simultaneous ion-plasma deposition of two-component coatings of the given composition, deposition and ion mixing of multilayer one-component coatings.
· There will be developed technology for depositing of coatings from multicomponent alloys.
· There will be determined the direction, sequence of phase transformations, obtained quantitative information on the formed phases on the basis of experimental data on thermally induced phase transition processes in superalloys with multicomponent coatings.
· There will be produced samples with thermally stable depth distribution of phases, what means with varying with depth properties. There will be revealed main mechanisms of thermal stabilization and developed theoretical models, algorithms and performed numerical calculations.
· Based on tests of samples with chemically compatible coatings there will be developed general principles for corrosion protection and improvement of mechanical characteristics. To understand the corrosion mechanisms at atomic level the processes of nucleation and proliferation of cracks in samples under load will be numerically simulated.
· From imitation tests with irradiation of samples with light charged particles there will be revealed basic mechanisms of helium behavior and gas swelling in coated materials at various irradiation doses and consequent annealings. Based on the experimental data, there will be developed theoretical models, algorithms and performed numerical calculations of gas swelling in layered materials.
· There will be obtained and tested massive samples with multifunctional coatings. There will be elaborated practical recommendations on production of coated materials with given physical and mechanical properties.
. Proceeding of “High Temperature Reactor Materials Workshop”, ed. Todd Allen, ANL-02/12/, June, 2002.
. K.К.Kadyrzhanov, A.L.Udovsky, T.E.Turkebaev , Nucl. Instr. Meth. B103 (1995) 38.
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