Papers by Keyword: ODS

Abstract: A powder metallurgical process has been applied to synthesize the FeNiCr+Y₂O₃ oxide dispersion strengthened (ODS) alloys. The composition of the reinforcing Y₂O₃ added into matrix was varied from zero to 2.0 percent weight. Raw powders were carefully weighed with a four-digit balance. Y₂O₃ powder was pre-linked into Fe powder as the dominant element in the matrix by manually ground for half an hour. Ni and Cr powders were then mixed evenly for the next a half hour to obtain FeNiCr+Y₂O₃ precursor. Avoiding agglomeration and grain coarsening, the precursor was uniformly homogenized by milling for 20 hours. The precursors were then compressed at an isostatic pressure of 100 kN to 12 grams of pellets each. To prevent sample erosion during smelting with an electric arc furnace (EAF), crystal growing mechanism by conventional sintering was performed at 900 °C for 2 hours. This strengthens the bonds between precursors in forming ODS alloys. The samples were then melt-casted in the arc by 4 times flips. As a result, the neutron diffraction analysis and SEM-EDS strongly reveal the austenitic crystal structure and Y2O3 oxide successfully dispersed in the cast-alloy respectively. The microstructures with Y2O3 oxide spread uniformly overall the cast-alloy surfaces.

Abstract: Development of accident-tolerant fuel (ATF) cladding materials for LWR (Light Water Reactors) is being intensively carried out in many research centers in the world as the lesson-learned from the Fukushima Daiichi nuclear reactor power plant accident. One of the advanced high temperature materials which is intensively developed is Oxide Dispersion strengthened (ODS) steel. The strengthened mechanism is generated by homogeneous dispersion of nanometer sized ceramic oxide particles in the matrix of the steel which is done by mechanical alloying technique so called mechanosynthesis. Synthesis of an austenitic ODS steel powder of SS316L with additional element of 4% aluminum and dispersion of nanoparticles of 0.5% yttrium oxide (yttria: Y₂O₃) has been done. The aim of the research is to achieve a better performance of SS316L steel as the established material for power plant at elevated temperature. Mechanosynthesis was done using High Energy ball Milling (HEM) for 30 hours with BPR (Ball to Powder Ratio) of 10:1. Afterward, the sample was characterized using Scanning Electron Microscope-Energy Dispersive Spectroscope (SEM-EDS) and X-ray diffraction (XRD) to analyze the microstructure characteristics. The results showed that the alloying between SS316L and aluminum powders was formed. Furthermore, crystal grains and the particles of SS316L-4Al-0.5Y₂O₃ powder was smaller than as received SS316L and aluminum powders.

Abstract: Fe-10wt% La (OH)₃ composite powders have been fabricated by ball milling, under argon atmosphere for milling periods of 0, 5 and 10 h, respectively. Changes in structural, morphological, thermal and magnetic properties of the powders during mechanical alloying and during subsequent annealing have been examined by X-ray diffraction, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and vibrating sample magnetometer (VSM). XRD results: showed the formation of new phases (Fe and LaFeO3 perovskite) created through the ball milling. The results showed that the crystalline size of ball milled powders decreased with increasing the milling time. In fact, after 10 h of ball milling, La (OH)₃ changes from nanostructure in amorphous structure. The magnetic measurements display a distinct saturation magnetization and coercivity.

Abstract: Recently, the use of high temperature materials are became more common in different types of engineering activities. The new generation of Oxide dispersion strengthened alloys (ODS) consist of Fe-Al matrix with small oxide particles dispersed within it, was generated by the authors to keep their mechanical properties at elevated temperatures. The new ODS prepared by means of mechanical alloying and hot consolidation. The preliminary tests results shows a better oxidation resistant, creep and Ultimate Tensile Strength (UTS) compare to similar materials. To go more inside in thermomechanical and microstructural properties, a series of different test were performed on different variant of ODS which manufactured by the authors. The results show that the annealing time and temperature has a significant influence on these properties while almost total recrystallization of grains and subgrains were observed during the investigation.

Abstract: The oxide dispersed strengthened (ODS) ferritic-martensitic steel was irradiated by 100MeV iron ion whose energy was degraded by using a Ta foil of 4 μm thick, 100 keV Hydrogen and 200 keV Helium at 480, 515, 550 and 580 °C. The irradiation fluences were 1×10¹⁶, 1.1×10¹⁵ and 6.8×10¹³/cm², respectively for Fe, H and He. The techniques of positron annihilation lifetime and Doppler broadening of slow positron beam were utilized to examine the produced radiation damage. At 550 °C the maximal positron annihilation lifetime and S parameter of Doppler broadening were observed, implyin g tha t 550 °C is the pea k temperature of swelling. The S parameter and annihilation lifetime of the sample irradiated at 515 °C by the single Fe ion beam were smaller compared to the triple beam irradiation at the same temperature, implying that the triple beam irradiation caused more severe damage than the single beam irradiation.

Abstract: Sealing of nuclear fuel material inside the fuel element clad must create a leak-tight "safety barrier" to prevent the release of radioactive products to environment. High quality welds are mandatory to withstand harsh conditions (radiation, pressure, temperature, corrosion) making possible the safe operation of nuclear reactors. The joint design, material selection and welding technique must be combined by smartly balancing possible technological options to yield the best attainable quality for the intended purpose; these choices are discussed in the paper. For thin-walled clad to end-plug welding, heat flow pattern as determined by joint design and fitting accuracy proved to be crucial for the fusion boundary shape and moreover for the success rate in automate welding. Consequently, Finite Element Analysis of the transient thermal field during welding was performed, in order to determine the best compromise with reasonable machining precision for parts. The main features of the developed thermal model and some results illustrating its good predictions vs. actual welds are also presented. Helium-shielded pulsed welding was initially preferred to minimize HAZ, distortion and porosity but unfortunately important cast-to-cast variation in penetration was observed with Inconel-600 plugs, due to Marangoni effect. Extensive work was done to overcome this, mainly through variation of pulsing and of the shielding gas; depth-to-width ratio can be noticeably improved with no material addition. Out of welding classic cladding materials, studies were initiated at INR on joining oxide-dispersion strengthened (ODS) alloys and specialty austenitic formulations (e.g. 15/15Ti) since they are candidate materials of great interest for the next generation of nuclear reactors.

Abstract: Oxide dispersive steel is a promising material for next nuclear reactors generation. Performance of this material in nuclear reactor can be modeled by means of irradiation by swift Bi ions, which are typical nuclear fusion products. Radiation damage results in microstructure alternation leading to formation of micro and macro stresses that influence the material performance. The residual stress state of ferrite matrix of the steel is investigated by XRD methodic and dependence on the irradiation dose is analyzed.

Abstract: In this paper, by combining methods of LMS Test.Lab test systems analysis and Ansys finite element analysis on the rack of batching mixer system for dynamic performance analysis, the ODS and the modal parameter of the batching mixer machine rack is obtained. Two research methods results show that, the weakness of the rack vibration is that there is large vibration deformation on the stands of two sides and two beams above the rack. The corresponding parts need firming connection to reduce the vibration of left and right sides, before and after the rack, and improving the working stability of batching mixer machine rack. This paper provides a valuable reference for the vibration and noise control of batching mixer system.

Abstract: By using ODS (Operating Deflection Shapes) technology, the modal parameters of the rack of a batching system mixer under operating condition are identified and the modal shape and modal damping ratio of the rack in a few working frequencies are obtained. The results show that, the batching machine rack on working condition has a significant effect on some frequency and the work principal modes that appear as before and after exercise of two beams above the rack and swaying motion of the brackets of the two side surface. This paper provides a valuable reference for the structure vibration optimization of batching system mixer.

Abstract: A new method was employed to synthesize nanosized Y₂O₃ dispersion strengthened Fe-base superalloy powders using self-propagating combustion. A concentrated solution of nitrates of iron and yttrium was used as oxidizer, malic acid as fuel to fabricate Fe₂O₃/Y₂O₃ powders at low temperature. Afterwards, uniform and fine Fe/2wt.%Y₂O₃ powders were obtained by selective reduction with hydrogen, on the surface of which dispersive Y₂O₃ particles of the mean size of 30 - 50 nm were observed.